Molecular pathogenesis of tumorigenesis caused by succinate dehydrogenase defect

Molecular pathogenesis of tumorigenesis caused by succinate dehydrogenase defect

Journal Pre-proof Molecular pathogenesis of tumorigenesis caused by succinate dehydrogenase defect Behrooz Moosavi, Xiao-lei Zhu, Wen-Chao Yang, Guang...

3MB Sizes 0 Downloads 26 Views

Journal Pre-proof Molecular pathogenesis of tumorigenesis caused by succinate dehydrogenase defect Behrooz Moosavi, Xiao-lei Zhu, Wen-Chao Yang, Guang-Fu Yang

PII:

S0171-9335(19)30141-4

DOI:

https://doi.org/10.1016/j.ejcb.2019.151057

Reference:

EJCB 151057

To appear in:

European Journal of Cell Biology

Received Date:

16 June 2019

Revised Date:

19 September 2019

Accepted Date:

29 October 2019

Please cite this article as: Moosavi B, Zhu X-lei, Yang W-Chao, Yang G-Fu, Molecular pathogenesis of tumorigenesis caused by succinate dehydrogenase defect, European Journal of Cell Biology (2019), doi: https://doi.org/10.1016/j.ejcb.2019.151057

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Title: Molecular pathogenesis of tumorigenesis caused by succinate dehydrogenase defect

Authors:

ro

of

Behrooz Moosavi, Xiao-lei Zhu, Wen-Chao Yang, and Guang-Fu Yang

-p

Affiliation:

Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of

lP

re

Chemistry, Central China Normal University, Wuhan 430079, P.R.China

Corresponding authors: Behrooz Moosavi and Guang-Fu Yang, Phone: +86-27-

ur na

67867800, Fax: +86-27-67867141, Email: [email protected] and [email protected]

Jo

Highlights 

Malfunction of succinate dehydrogenase (SDH), leads to tumorigenesis.



Succinate is linked to metabolite and GPCR signalling, and inflammatory response.



Moderate generation of ROS leads to tumorigenesis.



Succinate levels and ROS are therefore the denominators of tumorigenesis.

1

Abstract Succinate dehydrogenase (SDH), also named as complex II or succinate:quinone oxidoreductases (SQR) is a critical enzyme in bioenergetics and metabolism. This is because the enzyme is located at the intersection of oxidative phosphorylation and

of

tricarboxylic acid cycle (TCA); the two major pathways involved in generating energy

ro

within cells. SDH is composed of 4 subunits and is assembled through a multi-step

process with the aid of assembly factors. Not surprisingly malfunction of this enzyme

-p

has marked repercussions in metabolism leading to devastating tumors such as paraganglioma and pheochromocytoma. It is already known that mutations in the genes

re

encoding subunits lead to tumorigenesis, but recent discoveries have indicated that

lP

mutations in the genes encoding the assembly factors also contribute to tumorigenesis. The mechanisms of pathogenesis of tumorigenesis have not been fully understood. However, a multitude of signaling pathways including succinate signaling was

ur na

determined. We, here discuss how defective SDH may lead to tumor development at the molecular level and describe how yeast, as a model system, has contributed to understanding the molecular pathogenesis of tumorigenesis resulting from defective

Jo

SDH.

Keywords: Succinate dehydrogenase, mitochondria, signaling, ROS, hereditary paraganglioma, pheochromocytoma

2

Introduction Succinate dehydrogenase (SDH) also named as complex II or succinate:quinone oxidoreductases (SQR) is positioned at the intersection of oxidative phosphorylation and tricarboxylic acid cycle (TCA) (Fig 1), the essential pathways of bioenergetics in many organisms. SDH comprises 4 subunits (Fig 1) that are assembled together through a multi-step process which is facilitated by accessory proteins. The details of

of

structure, function and assembly of SDH have been recently reviewed by our group in a

ro

separate article and interested readers are referred to that article (Moosavi et al., 2019).

-p

Mutations in the genes encoding 4 subunits lead to tumorigenesis. Additionally recently various types of tumors have been caused by defects in accessory (assembly) factors.

re

Tumorigenesis is not only the consequence of energy production deregulation and

lP

metabolism; an essence of the function of SDH but also the result of signaling events, as this enzyme plays diverse signaling roles, some of which recently discovered. This, therefore, makes understanding the tumorigenesis difficult. Further complexity is added

ur na

to that because SDH, on the one hand, is a sensor of apoptosis and therefore its proper function is required for apoptosis and on the other hand, its defect causes apoptosis through various mechanisms. We here, entangle pathways which contribute to

Jo

tumorigenesis as a consequence of SDH defect and present a clearer picture of the molecular details.

The role of SDH mutations in tumor development

3

For simplicity, the mutations are divided into two groups; mutations in SDH subunits and in assembly factors.

Mutation in SDH subunits SDH impairment is implicated in tumors such as hereditary paraganglioma, and

of

pheochromocytoma (Astuti et al., 2001; Baysal et al., 2000; Niemann and Müller, 2000;

ro

Yankovskaya et al., 2003). Succinate dehydrogenase (SDH) and fumarate hydratase (FH; the enzyme which catalyzes the next step in the Krebs cycle ensuing SDH)

-p

mutations follow the hereditary pattern of tumor suppressor genes. The inflicted cells inherit a germline loss of function mutation in one allele while the other wild-type allele is

re

lost through somatic deletion or chromosomal loss (termed loss of heterozygosity)

lP

leading to tumor development (Bayley and Devilee, 2010; Zhou et al., 2018). Although initially it was thought that SDHA mutations were responsible for Leigh

ur na

syndrome (LS), a neurodegenerative disease, recent data indicate SDHA mutations can also cause sporadic paragangliomas and pheochromocytomas (Burnichon et al., 2010; Dwight et al., 2013; Korpershoek et al., 2011) and even recently an SDHA mutant has been reported to give rise to both disorders (Renkema et al., 2015). Furthermore,

Jo

mutations in the SDH assembly factor SDHAF1 (Ghezzi et al., 2009a), SDHB (Alston et al., 2012) and SDHD (Jackson et al., 2013) were shown to induce LS or LS-like symptoms.

Defect in SDH expression has also been observed in a subset of gastrointestinal stromal tumors (GIST). GIST that lack KIT or platelet-derived growth factor receptor

4

alpha (PDGFRA) mutations have been classified as KIT/PDGFRA wild type GIST (WT GIST) (Corless et al., 2004). 20–40% of all KIT/PDGFRA WT GIST is succinate dehydrogenase complex (SDH)-deficient GIST. In this disease, SDH expression is impaired usually as a result of germline and/or somatic loss-of-function mutations in any of the four SDH subunits (A, B, C, or D) (Corless et al., 2004; Nannini et al., 2017). Other forms of malignancy associated with impaired SDH function include renal and

of

thyroid tumors, neuroblastoma, and testicular seminoma, implying its involvement in a

ro

wide range of tumors (Bardella et al., 2011).

-p

Besides tumor and neurodegeneration, SDH defects are also implicated in diabetes, ageing, optic atrophy, ischemia reperfusion (IR) injury and ischemic preconditioning

re

(IPC) (Rustin et al., 2002; Wojtovich et al., 2013). The broad spectrum of diseases is likely a reflection of several roles that SDH plays in cellular processes (Rustin et al.,

ur na

lP

2002).

Mutation in assembly factors So far at least 4 SDH assembly factors have been identified in humans including SDHAF1, SDHAF3, SDHAF2, and SDHAF4.

Jo

SDHAF1 (in humans)/ Sdh6 (in yeast): A soluble mitochondrial matrix protein (Iverson et al., 2012) which was initially identified as a specific human SDH assembly factor, defective in two families with specific infantile leukoencephalopathy syndrome. The diminished function of SDHAF1 in humans and its homolog in yeast cause reduced SDH activity and assembly but engender no effect on other mitochondrial respiratory

5

chain complexes implying its specificity to the SDH assembly (Ghezzi et al., 2009a). Later more cases of infantile leukoencephalopathy syndrome were reported with similar or novel mutations in SDHAF1 gene (particularly Gly57Arg substitution) with varying clinical symptoms. All patients showed accumulation of succinate detectable by in vivo proton MR spectroscopy of the brain (Ohlenbusch et al., 2012; Taylor et al., 2013).

of

Studies have indicated that although yeast Sdh6 and human SDHAF2 have similar functions, they may differ in certain aspects (Ghezzi et al., 2009b). Sdh6 (in yeast)

ro

presumably interacts with Sdh1/Sdh2 subcomplex and the interface for the interaction

-p

lies within Sdh2 (Van Vranken et al., 2015). SDHAF1 (in humans) contains an LYR motif; LX(L/A)YRXX(L/I)(R/K) which is likely the signature for proteins involved in Fe-S

re

metabolism. Thus SDHAF1 harboring LYR motifs may play a role in insertion or retention of the Fe-S centers within SDH structure. Consequently, failure in SDHAF1

lP

incorporation into the apo-enzyme structure may undermine the holo-enzyme structure or prevent its formation (Ghezzi et al., 2009a). In line with this, defective SDHAF1

ur na

significantly debilitates the biogenesis of SDHB as a result of sequential rapid degradation by the mitochondrial protease, LONP1 (Maio et al., 2016). A separate study using yeast, fly and mammalian cell culture have shown that SDHAF1

Jo

in concert with SDHAF3 (another assembly factor; see below) promotes maturation of SDH2 during oxidative metabolism and particularly protects against ROS damage, however, the details have not been fully investigated (Na et al., 2014). SDHAF3 (in humans)/ Sdh7 (in yeast and Drosophila): SDHAF3/Sdh7 and SDHAF1/Sdh6 are assembly factors required for maturation of SDHB/ Sdh2. When Sdh7 in yeast and Drosophila is deleted SDH activity and Sdh2 levels are reduced.

6

Drosophila without Sdh7 is hypersensitive to oxidative stress and suffers from muscular and neuronal dysfunction. Yeast Sdh7 and Sdh6 act together to assist in Sdh2 maturation through interaction with Sdh1/Sdh2 intermediate (interface of the reaction resides within Sdh2), protecting against oxidative damage. These data from yeast and Drosophila implied that SDHAF3 mutations might have caused SDH-associated disease in cases where no mutations in the genes encoding SDH subunits were identified (Van

of

Vranken et al., 2015). This prediction recently came true as an impaired (hypomorphic)

ro

variant of SDHAF3, c.157 T > C (p.Phe53Leu) was identified in pheochromocytoma and paraganglioma patients. In agreement with that, the sdhaf3 mutant could not restore

-p

SDH function in yeast cells lacking Sdh7. Furthermore, although WT SDHAF3 could

re

interact directly with SdhB in vitro, the defective variant could not (Dwight et al., 2017). SDHAF2: Studies in human initially revealed that germline loss-of-function mutations in

lP

SDHAF2 gene segregate with hereditary paraganglioma; a neuroendocrine tumor hitherto associated with mutations in genes encoding SDH subunits (Hao et al., 2009).

ur na

Further clinical studies were carried out in sporadic patients with paraganglioma and pheochromocytoma who had no mutations in SDHD, SDHC, or SDHB. They revealed that investigating SDHAF2 mutations in young patients suffering from isolated head and neck paraganglioma without mutations in SDHD, SDHC, or SDHB, and in individuals

Jo

with familial antecedents who are negative for mutations in all other risk genes is definitely justifiable and may reveal mutations in SDHAF2 gene (Bayley et al., 2010). Subsequently, more cases of head and neck paraganglioma and their association with various types of SDHAF2 mutations/deletion were reported (Hoekstra et al., 2017; Kunst et al., 2011; Piccini et al., 2012; Zhu et al., 2015). In one study a universal genetic

7

screening approach was applied for sequencing all susceptibility genes for hereditary pheochromocytoma/paraganglioma. And a novel SDHAF2 mutation in association with pheochromocytoma was identified which was previously found to be linked to mutations in SDH subunits and other genes. This study illustrated that the application of this approach was particularly useful to detect new SDHAF2 mutations which might have

of

been otherwise overlooked by assessing only phenotype (Casey et al., 2014).

ro

SDHAF4 (in humans and Drosophila)/ Sdh8 (in yeast):

Sdh8 is a mitochondrial matrix protein with two functions; first, it binds directly to Sdh1-

-p

FAD and acts as a chaperone to protect against ROS generated by solvent-accessible FAD covalently bound to Sdh1. Second, it assists in Sdh1-Sdh2 dimer formation and

re

thereby stabilizes the SDH complex structure.

lP

So far no human disease reported being associated with defective SDHAF4. However, the pathology of sdhaf4Δ in Drosophila can possibly be linked to the corresponding

ur na

human diseases, as defects in various SDH subunits of model organisms typically cause analogous diseases in humans. This is in line with the reports of SDH-defective diseases such as Leigh’s syndrome and Wild Type gastrointestinal stromal tumors (WT GIST) without any mutations in all known genes encoding SDH subunits (Van Vranken

Jo

et al., 2014).

Mutating SDH8 in yeast/fly and siRNA-mediated knockdown of SDHAF4 in mammalian cells reduce the levels of SDH complex and SDH enzyme activity. Nevertheless, Sdh8/SDHAF4 is not absolutely essential for SDH activity. Because SDH activity is still preserved to some extent even though Sdh8/SDHAF4 is lacking in yeast/fly/mammalian

8

cell models. Surprisingly though the loss of SDHAF4 induces more drastic outcomes in Drosophila than in yeast and mammalian cells. This is partly because sdhaf4Δ Drosophila maintains only 10% of SDH activity and almost no SDH complex while the sdh8Δ yeast strain keeps 40% of SDH activity and complex formation. Additionally deletion of SDHAF4 in Drosophila, unlike yeast, destabilizes Sdh1 dramatically and leads to both muscular and behavioral dysfunction. The reason for these differences is

of

not fully understood but it might be that SDHAF4/Sdh8 in mammalian cells/yeast cells is

-p

against oxidative stress (Van Vranken et al., 2014).

ro

functionally redundant or that the yeast growth media may provide a buffering capacity

re

The molecular mechanisms of tumorigenesis associated with impaired SDH

lP

function

At least four key players seem to coordinate tumor development;

ur na

(I) Functions of succinate or SDH;

(A) Metabolite signaling; The SDH and FH mutants promote the accumulation of succinate and fumarate respectively in the mitochondria; these metabolites are then transported into the cytosol (through the dicarboxylic acid transporters) and

Jo

inhibit prolyl hydroxylase (PHD) (Fig 2). This, in turn, leads to the inhibition of hypoxia-inducible factor (HIF) degradation and thereby its accumulation. The enhanced levels of HIF induce tumorigenesis through reinforcing resistance to apoptotic and/or a pseudohypoxic signaling that favors glycolysis; a requirement for tumor expansion. The enhanced levels of HIF can also stimulate

9

angiogenesis that enables feeding the tumor (Esteban and Maxwell, 2005; King et al., 2006; Lee et al., 2005b; Rutter et al., 2010). Succinate and fumarate may inhibit other dioxygenases in addition to PHD, some of which are directly involved in tumorigenesis. Histone demethylases (HDM) and the ten-eleven translocation (TET) family of 5-methylcytosine (5mC) hydroxylases (TET1-3) are examples of such dioxygenases (Laukka et al., 2016; Tretter et al., 2016) (Fig 2). These

of

enzymes are key epigenetic regulators of metabolism and ageing, reviewed in

ro

Salminen et. al. (2015) (Salminen et al., 2015). The effect of non-functional SDH in epigenetic regulation of tumorigenesis was first shown in yeast and confirmed

-p

in human embryonic kidney cells (T293 cells) (Smith et al., 2007; Tretter et al.,

re

2016). Subsequently, pharmacological inhibition of SDH activity in various cell lines and siRNA-based gene silencing of SDHD and SDHB in HEK293 and

lP

Hep3B cells indicated that the reduction of SDH activity leads to an increased methylation of histone H3 and that can be reversed by overexpression of the

ur na

H3K27me3-specific Jmjd3 histone demethylase (Cervera et al., 2009; Tretter et al., 2016). In keeping with this, studies in human Hela cells demonstrated that dysfunctional FH and SDH promote inhibition of histone demethylation and hydroxylation of 5mC (Tretter et al., 2016; Xiao et al., 2012). While compromised

Jo

function of SDH as a result of mutations in SDH genes leading to elevated levels of succinate is already known to cause histone methylation (i.e. hypermethylation), another type of epigenetic dysregulation has been reported in various types of tumors; in this case hypermethylation occurred in the SDHC promoter without any mutations in SDH genes which resulted in aberrant

10

expression of SDH and consequently tumor development (Bezawork-Geleta et al., 2017). The hypermethylation may not be limited to the SDHC promoter region, as a recent study using a human hepatocellular carcinoma G2 (HepG2) cells showed that accumulation of succinate and fumarate led to global DNA hypermethylation (Wentzel et al., 2017) (Fig 2). In contrast with these findings, a new study, using a mouse cell line model, reported that in fact DNA methylation

of

derangement rather than just DNA hypermethylation is the driver of familial

ro

pheochromocytoma and paraganglioma (Smestad et al., 2018). The reason for this dissonance is unknown, but it might be related to the level of DNA

-p

methylation site coverage of each study (Smestad et al., 2018). Altogether these

re

findings indicate various signaling functions of accumulated succinate can be translated into genetic and epigenetic alterations and eventually lead to tumor

lP

formation.

(B) Link with apoptosis; another mechanism by which SDH may be involved in

ur na

both tumorigenesis and Leigh syndrome is through apoptosis. SDH defect is linked with apoptosis through three mechanisms (Fig 3). (1) Through PHD and HIF as described above, (2) through ROS formation as will be explained later in this section, and (3) through a direct function of SDH as an apoptosis sensor,

Jo

reviewed in (Grimm, 2013; Hwang et al., 2014). Recent evidence suggests this function of SDH is exerted through sensing pH but most likely this is not the only sensor. Apoptosis presumably promotes acidification of intracellular milieu and Ca2+ influx into mitochondria, leading to the dissociation of SDHA/B dimer from the rest of the SDH complex. The SDH activity of the dimer is retained while its

11

SQR activity is curtailed. This prompts the catalytic generation of ROS and eventually induces cell death through oxidative stress (Grimm, 2013). When SDH function is impaired, resistance builds up to apoptosis signals that otherwise prevent tumor development. In support of this hypothesis one study indicated that mitochondrial outer membrane (MOM) permeabilization is a crucial

of

step in apoptosis signaling which leads to the inhibition of SDH complex (and complex I) in a caspase-dependent manner and this contributes to apoptotic cell

ro

death via ROS generation- these are high lethal doses of ROS which lead to

-p

apoptosis, while sublethal concentrations contribute to tumor formation- and ΔΨμ collapse (Grimm, 2013; Ricci et al., 2003). Furthermore, another study revealed

re

that functional SDH is required for apoptosis induction through nerve growth factor (NGF) withdrawal in neurons (Grimm, 2013; Lee et al., 2005a). It appears

lP

that NGF deprivation activates the transcription factor c-Jun and apoptosis via PHD3 (EglN3), a prolyl hydroxylase involved in HIF1α degradation. In this case,

ur na

however, the apoptosis is induced by KIF1Bβ and not HIF1α. KIF1Bβ is a motor protein engaged in anterograde transport of synaptic vesicles (Grimm, 2013). This protein has been found to be a tumor suppressor which acts by activating calcineurin, and mitochondrial fission (Li et al., 2016). KIF1Bβ also increases

Jo

ROS which through a positive feedback loop reinforces the expression of KIF1Bβ (Angelina et al., 2017). Although these studies suggest that the functionality of SDH is required for apoptosis induction, there is evidence that apoptosis can also be induced when SDH function is inhibited with vitamin E (VE) analogs such as the mitochondrially targeted VE succinate (MitoVES) (Dong et al., 2011) and

12

mutation in ubiquinone-binding (Qp) site (Kluckova et al., 2015). Cell death, in the latter case, has been found to be dependent on ROS generation and that the magnitude of cell death corresponds with the potency of inhibition at the Qp site unless the concentration of intracellular succinate is high. Accordingly, it has been suggested that induction of cell death by MitoVES or Qp site inhibition may be of importance in tumor therapy (Kluckova et al., 2015). It, therefore, seems

of

that apoptosis may occur through various mechanisms under certain

ro

circumstances in different cell types in which the rate of ROS generation together with the succinate levels may be important determinants of cell fate. This

-p

necessitates consideration of these and other potential variables in all

re

therapeutic approaches.

(C) G-protein-coupled receptors signaling; accumulated succinate may contribute

lP

to the pathogenesis of hereditary paraganglioma/phaeochromocytoma syndrome yet through another signaling pathway. This is a signaling function for succinate

ur na

beyond its typical role as a Krebs cycle metabolite. G-protein-coupled receptors (GPCRs) GPR91 (also known as SUCRN1) act as succinate receptors (Bardella et al., 2011) and the interaction between succinate and these receptors triggers a signaling pathway (Fig 4). This implies that enhanced levels of succinate may

Jo

dysregulate the physiological activity of the G-protein-coupled GPR91 receptors possibly leading to sustained signaling pathway with potential tumorigenesis consequences (Bardella et al., 2011). In keeping with this, it was revealed that GPR91 expression was significantly up-regulated in SDHB-silenced cells. Furthermore, GPR91 mRNA was also induced in VHL negative cells and in

13

HepG2 cells upon overexpression of HIF2α. These results suggest HIF may induce GPR91 transcription while SDHB is silenced (Bardella et al., 2011; Cervera et al., 2008). Additionally, in ischemic retina, succinate acting through GPR91 effects vessel growth via stimulating the release of proangiogenic factors vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), and Ang-2 by the retinal ganglion neurons, in a HIF1α-independent manner (Bardella et al.,

of

2011; Mu et al., 2017; Sapieha et al., 2008; Zhao et al., 2017). Likewise, using

ro

human umbilical vascular endothelial cells it was found that succinate

upregulates VEGF expression by activating signal transducer and activator of

-p

transcription 3 (STAT3) and extracellular regulated kinase (ERK)1/2 via its

re

receptor GPR91 in a HIF-1α independent fashion (Mu et al., 2017; Zhao et al., 2017) (Fig 4). These results show that in tumors associated with impaired SDH

lP

function, succinate could trigger the proliferation of endothelial cells by a paracrine mechanism. These angiogenic responses can synergize with the

ur na

vascularizing effects of HIF signaling during pseudohypoxia (Bardella et al., 2011).

(D) Inflammation; succinate can also act through a newly-defined and an unexpected mechanism and that is inflammation. The emergence of

Jo

inflammation as a tumorigenic factor seemed counterintuitive but it turned out to be factual. Succinate induces interleukin-1β (IL-1β) production through HIF-1α (Tannahill et al., 2013; Zhao et al., 2017). Therefore accumulation of succinate in the tumor microenvironment advances the inflammation (Zhao et al., 2017). Along with acting through GPR91, this mode of action can be considered a

14

second example by which succinate functions through a paracrine mechanism. Notably enhanced levels of IL-1β has also been found in several malignancies including colorectal, oral and colon cancer (Johnstone et al., 2016; Lee et al., 2015; Li et al., 2012; Zhao et al., 2017). Inflammation can, in turn, lead to the release of bioactive molecules including; proangiogenic factors that maintain nutrition supplement; growth factors that support proliferative signaling;

of

extracellular matrix-modifying enzymes that facilitate angiogenesis, metastasis,

ro

and invasion (Hanahan and Weinberg, 2011; Zhao et al., 2017).

-p

(II) Tumor suppressor p53; SDHB/D mutations are linked with lower levels of p53 and reduced p53 binding to NADH ubiquinone oxidoreductase I, therefore promoting

re

tumorous phenotype (Wojtovich et al., 2013).

lP

(III) ROS generation; SDH complex is already known to be a source of ROS production (Jardim-Messeder et al., 2015; Murphy, 2009; Paddenberg et al., 2003; Ralph et al., 2011; Wojtovich et al., 2013). The debate on how ROS can trigger tumorigenesis has

ur na

not yet been settled. One study has shown that the loss of SDHB but not SDHA increases ROS production which in turn leads to the hypoxia-response by PHD inhibition (Guzy et al., 2008; Saito et al., 2016). In line with this, another study has

Jo

recently illustrated that SDHB silencing leads to the loss of SDH complex activity, followed by elevated production of ROS, nuclear stabilization of HIF1α and increased expression of anti-apoptotic Bcl-2 (Saito et al., 2016). Moreover, a yeast model study has illustrated that the enhanced levels of ROS due to SDHB subunit defect, leads to elevated DNA mutability thereby contributing to tumorigenesis (Goffrini et al., 2009). On the other hand, there are reports of no increase in the levels of ROS production despite

15

mutations in SDHB, C, or D (Cervera et al., 2008; Pollard et al., 2005). It is possible that different mutations and the method by which SDH subunit is knocked down/mutated contribute to various degrees to ROS formation. Nevertheless, the discord on the role of ROS in tumor formation warrants further examinations. (IV) Epigenetic dysregulation; Mutation in SDH genes is an established cause of many

of

cases of pheochromocytomas and paragangliomas. Recently cases of these tumors have been found to be associated with mutations in enzymes responsible for epigenetic

ro

regulation of histones (which affects gene expression) such as histone-

-p

methyltransferases, histone-demethylases, or even mutations in histone itself (Toledo et al., 2016). This raises the possibility that this abnormal histone modifications or histone

re

may also influence SDH expression indirectly (Bezawork-Geleta et al., 2017).

lP

Taken together SDH defects can lead to two completely adverse outcomes; tumor and neurodegeneration. This points to the two facets of mitochondria; ‘energy-producing’ and ‘death-promoting’ which is contingent upon; gene dosage, timing and exposure time

ur na

to loss-of-function as well as tissue sensitivities. How the cell decides which route to follow remains to be established (Eng et al., 2003). Although significant progress has been made in understanding the molecular mechanisms of mitochondrial diseases no

Jo

effective therapy has been found as yet. This, therefore, necessitates developing novel drugs to treat these diseases (Kluckova et al., 2013; Lasserre et al., 2015). Recently it has been found that the loss of SDH function leads to reliance on pyruvate carboxylation for cellular anabolism. This reduction in metabolic plasticity which occurs in tumors may, therefore, be exploited as a strategy to develop novel drugs against tumorigenesis (Lussey-Lepoutre et al., 2015). Some of other potential therapeutic

16

approaches against various pathologies associated with SDH defect include lactate dehydrogenase (LDH) inhibition (as there is synthetic lethality between SDHC and LDHA) (Smestad et al., 2018), adjusting metabolites such as fumarate and succinate (Xiao et al., 2012), treating with α-ketoglutarate derivatives (MacKenzie et al., 2007), manipulating chromatin modifications (for those pathologies associated with chromatin remodeling) (Toledo et al., 2016; Xiao et al., 2012). Clearly, the mechanism of

of

tumorigenesis is complex and a single approach may not be effective to treat the

ro

disease, therefore therapeutic avenues may consider a more systemic view of the

-p

pathology.

re

Yeast as a model organism for studying SDH genetic defects in human disorders

lP

Model organisms such as bacteria, yeast, worm, fly, and mice have contributed to a large extent to learn various aspects of mitochondrial biology (Rea et al., 2010).

ur na

Amongst model organisms yeast (here is usually referred to Saccharomyces cerevisiae unless otherwise stated) has a special place as an organism of choice (Rea et al., 2010) and that is because yeast provides many advantages over other organisms, including; (I) Yeast can survive with or without mitochondrial genome depending on the

Jo

existence/concentration of certain carbon source. For instance in the presence of high concentrations of glucose yeast prefers fermentation, while in the presence of nonfermentable carbon sources such as glycerol yeast switches to oxidative phosphorylation. (II) Having both haploid and diploid states, this organism enables studying the dominance and recessive nature of genetic mutations. (III) Genes can be rather easily knocked out or heterologously knocked in using versatile genetic

17

approaches. (IV) Approximately 40% of human genes whose mutations cause diseases have an orthologue in yeast. (V) Even the major difference between human and yeast mitochondrial genomes- that is the predominant heteroplasmy of human and the homoplasmy of yeast- can facilitate characterization of the pathogenic mutations (Rea et al., 2010; Rinaldi et al., 2010). Despite these advantages, there are cases where yeast (Saccharomyces cerevisiae) cannot be useful. For instance complex I does not

of

exist and instead, a nuclear-encoded NADH dehydrogenase is present (Rinaldi et al.,

ro

2010). Although in this case an alternative model; Yarrowia lipolytica an obligate aerobic yeast possessing a vital proton-pumping NADH:ubiquinone oxidoreductase, has

-p

enabled analysis of mitochondrial complex I (Kerscher et al., 2004).

re

Most studies with regard to mitochondrial proteins in model organisms have been undertaken using yeast (Rea et al., 2010). Furthermore, SDH genetic defects have

lP

been investigated in this microorganism. We, therefore, here, limit our examples of studies carried out mainly in this model. Smith et. al (Smith et al., 2007), for instance,

ur na

applied a yeast strain lacking Sdh2 subunit in an attempt to decipher the molecular pathogenesis of paraganglioma. They found out although ROS production was increased, DNA was not mutated as a result. On the other hand loss of SDH function resulted in a dramatic accumulation of succinate. This, in turn, led to inhibition of α-

Jo

ketoglutarate (α-KG)-dependent enzymes Jlp1 (involved in sulfur metabolism) and histone demethylase Jhd1. They also showed that mammalian JmjC-domain histone demethylases were also inhibited by succinate in vitro and in cultured cells. Altogether these results suggested that any α-KG-dependent enzyme might be dysregulated by enhanced levels of succinate leading to oncogenesis (Smith et al., 2007). This finding

18

was later substantiated further in vitro using C. elegans and human α-KG-dependent enzymes; histone methylases as well as in vivo using human Hela cells. The mechanism by which elevated levels of succinate leads to the inhibition of α-KGdependent enzymes has not been fully understood. But since there are some structural similarities between succinate (and fumarate), α-KG and 2-hydroxyglutarate, both succinate and fumarate may act as competitive inhibitors of α-KG-dependent

of

dioxygenases in addition to PHDs (Xiao et al., 2012).

ro

Yeast cells have also been exploited for studying glomus tumor associated with a

-p

missense mutation (C191Y) in SDHB gene germline (Goffrini et al., 2009). The mutant could not restore oxidative phosphorylation phenotype of sdh2 null mutant.

re

Furthermore, SDH activity was abolished, while sensitivity to oxidative stress increased. Notably, in contrast, to result from Smith et al. (2007) the frequency of petite colony

lP

formation was increased, indicating an increased mtDNA mutability. The authors proposed two reasons for this controversy. First, their experiment was performed at 37°

ur na

C in which mitochondrial DNA mutability was thought to be higher than 30° C, and second, they argued that their yeast growth assay on YP-ethanol media was a more sensitive test than PCR mtDNA amplification [used in Smith et al., (2007)] to measure the frequency of mtDNA mutability. The latter assay was already considered rather

Jo

insensitive by Smith et al. (2007). On the whole, it was concluded that C191Y mutation leads to augmented ROS production and mtDNA mutability. Whether this scenario truly occurs in human cells and leads to tumor development remains to be confirmed (Goffrini et al., 2009). In another attempt to delineate the molecular mechanisms of tumor development resulting from impaired SDH function, Szeto et al., (2007) took

19

advantage of a yeast model in which SDH3 and SDH4 mutations were generated corresponding to the mutations observed in humans cancers. They realized that both ROS and succinate levels increased as a result of the mutations and concluded that both of these effects may be echoed in the relevant human cancer cells (Szeto et al., 2007). Accumulated succinate leads to hypoxia and eventually promotes cell

of

proliferation as described in section 3. SDH gene deletions or truncations often cause diseases, but the pathogenic

ro

significance of missense substitutions is uncertain unless the cause-effect link between

-p

mutation and the disease is verified by functional and in silico studies or by the familial segregation with the phenotype. Yeast model has also been applied as a tool for

re

functional studies of such missense mutations. The results indicate that yeast can validate the pathogenic significance of SDHB missense mutations, however, this is true

lP

for missense mutations in SDHC and SDHD genes only when the mutation occurs in a conserved residue in a conserved domain (Panizza et al., 2013). Overall these

ur na

examples illustrate how yeast models can be applied to gain insight into the molecular pathogenesis of human diseases associated with different kinds of defects in SDH subunits. Nevertheless, findings in yeast models should always be confirmed in higher

Jo

eukaryotic models such as mice and human cells.

Concluding remarks and future perspective SDH is a unique enzyme in that it is located at the interception of oxidative phosphorylation and tricarboxylic acid cycle (TCA). Furthermore, it is engaged in

20

signaling pathways that control cell proliferation and apoptosis. Impaired function of SDH leads to the accumulation of succinate. And this triggers a number of signaling pathways that each one contributes in a different way to the tumorigenesis. These pathways include metabolic signaling, apoptosis, GPCRs, and inflammation. Furthermore, SDH defect is linked to low levels of the tumor suppressor p53, promoting tumor development through a distinct pathway. These pathways may eventually work

of

synergistically or independently depending on the tissues involved.

ro

The role of ROS in tumorigenesis is still controversial, but that may be the result of

-p

different methods by which SDH function was inactivated (knockdown versus mutation) for example) and therefore different levels of ROS generated.

re

Epigenetic can be the cause or the effect of impaired function of SDH. On one hand

lP

succinate accumulation leads to global DNA hypermethylation and histone hypermethylation eventually leading to tumor development, on the other hand, SDHC promoter hypermethylation can cause SDH defect and thereby succinate accumulation

ur na

triggering tumorigenesis through epigenetic and other mechanisms (Fig 2). SDH defect leads to opposite outcomes; cell death (in neurodegenerative diseases), and cell proliferation (in tumors). How these adverse outcomes arise is not fully

Jo

understood. Clearly many factors contribute to forcing cells to follow either pathway. These include gene dosage, tissue sensitivity, timing and exposure level to the pathogenic elements like ROS. Additionally, the integration of SDH function with other signaling pathways and sometimes contradictory roles of SDH in cellular processes make the pathology more complex. A case in point is that SDH can act as an apoptosis sensor and thereby its functionality required for apoptosis, while its impairment can

21

cause apoptosis. We are still at the beginning of the path to understand exactly the pathogenesis of diseases related to SDH defect. Since SDH is a multi-faceted enzyme systems (biology) approaches are essential to simultaneously probe the influence of several factors involved in the pathogenesis. These include ROS level, succinate level, and its signaling and apoptotic pathway.

of

Application of systems (biology) methods in simple eukaryotic model systems such as yeast might be a useful strategy to portray the molecular events occurring during

ro

tumorigenesis. At later steps, more advanced eukaryotic models may be exploited to

-p

confirm the relevance of findings.

lP

Conflict of interest

re

A mind map summary of the topics discussed in this article is presented in Fig 5.

ur na

The authors have no conflict of interest to declare.

Acknowledgments

Jo

Research on the biochemistry of SDH in the authors’ laboratory is financially supported by the National Key R&D Program (2017YFA0505203), and the National Natural Science Foundation of China (21837001).

22

References

Jo

ur na

lP

re

-p

ro

of

Alston, C.L., Davison, J.E., Meloni, F., van der Westhuizen, F.H., He, L., Hornig-Do, H.-T., Peet, A.C., Gissen, P., Goffrini, P., Ferrero, I., Wassmer, E., McFarland, R., Taylor, R.W., 2012. Recessive germline SDHA and SDHB mutations causing leukodystrophy and isolated mitochondrial complex II deficiency. Journal of Medical Genetics 49, 569-577. Angelina, C., Tan, I.S.Y., Choo, Z.e., Lee, O.Z.J., Pervaiz, S., Chen, Z.X., 2017. KIF1Bβ increases ROS to mediate apoptosis and reinforces its protein expression through O2−in a positive feedback mechanism in neuroblastoma. Scientific Reports 7, 16867. Astuti, D., Latif, F., Dallol, A., Dahia, P.L.M., Douglas, F., George, E., Sköldberg, F., Husebye, E.S., Eng, C., Maher, E.R., 2001. Gene Mutations in the Succinate Dehydrogenase Subunit SDHB Cause Susceptibility to Familial Pheochromocytoma and to Familial Paraganglioma. American Journal of Human Genetics 69, 49-54. Bardella, C., Pollard, P.J., Tomlinson, I., 2011. SDH mutations in cancer. Biochimica et Biophysica Acta (BBA) - Bioenergetics 1807, 1432-1443. Bayley, J.-P., Devilee, P., 2010. Warburg tumours and the mechanisms of mitochondrial tumour suppressor genes. Barking up the right tree? Current Opinion in Genetics & Development 20, 324-329. Bayley, J.-P., Kunst, H.P., Cascon, A., Sampietro, M.L., Gaal, J., Korpershoek, E., Hinojar-Gutierrez, A., Timmers, H.J., Hoefsloot, L.H., Hermsen, M.A., 2010. SDHAF2 mutations in familial and sporadic paraganglioma and phaeochromocytoma. The lancet oncology 11, 366-372. Baysal, B.E., Ferrell, R.E., Willett-Brozick, J.E., Lawrence, E.C., Myssiorek, D., Bosch, A., Mey, A.v.d., Taschner, P.E.M., Rubinstein, W.S., Myers, E.N., Richard, C.W., Cornelisse, C.J., Devilee, P., Devlin, B., 2000. Mutations in SDHD, a Mitochondrial Complex II Gene, in Hereditary Paraganglioma. Science 287, 848-851. Bezawork-Geleta, A., Rohlena, J., Dong, L., Pacak, K., Neuzil, J., 2017. Mitochondrial Complex II: At the Crossroads. Trends in biochemical sciences 42, 312-325. Burnichon, N., Brière, J.-J., Libé, R., Vescovo, L., Rivière, J., Tissier, F., Jouanno, E., Jeunemaitre, X., Bénit, P., Tzagoloff, A., Rustin, P., Bertherat, J., Favier, J., Gimenez-Roqueplo, A.-P., 2010. SDHA is a tumor suppressor gene causing paraganglioma. Human Molecular Genetics 19, 3011-3020. Casey, R., Garrahy, A., Tuthill, A., O'halloran, D., Joyce, C., Casey, M.B., O'shea, P., Bell, M., 2014. Universal genetic screening uncovers a novel presentation of an SDHAF2 mutation. The Journal of Clinical Endocrinology & Metabolism 99, E1392-E1396. Cervera, A.M., Apostolova, N., Crespo, F.L., Mata, M., McCreath, K.J., 2008. Cells Silenced for SDHB Expression Display Characteristic Features of the Tumor Phenotype. Cancer Research 68, 4058-4067. Cervera, A.M., Bayley, J.-P., Devilee, P., McCreath, K.J., 2009. Inhibition of succinate dehydrogenase dysregulates histone modification in mammalian cells. Molecular Cancer 8, 89. Corless, C.L., Fletcher, J.A., Heinrich, M.C., 2004. Biology of gastrointestinal stromal tumors. Journal of clinical oncology: official journal of the American Society of Clinical Oncology 22, 3813-3825. Dong, L.F., Jameson, V.J., Tilly, D., Cerny, J., Mahdavian, E., Marin-Hernandez, A., Hernandez-Esquivel, L., Rodriguez-Enriquez, S., Stursa, J., Witting, P.K., Stantic, B., Rohlena, J., Truksa, J., Kluckova, K., Dyason, J.C., Ledvina, M., Salvatore, B.A., Moreno-Sanchez, R., Coster, M.J., Ralph, S.J., Smith, R.A., Neuzil, J., 2011. Mitochondrial targeting of vitamin E succinate enhances its pro-apoptotic and anti-cancer activity via mitochondrial complex II. The Journal of biological chemistry 286, 3717-3728.

23

Jo

ur na

lP

re

-p

ro

of

Dwight, T., Mann, K., Benn, D.E., Robinson, B.G., McKelvie, P., Gill, A.J., Winship, I., Clifton-Bligh, R.J., 2013. Familial SDHA mutation associated with pituitary adenoma and pheochromocytoma/paraganglioma. The Journal of Clinical Endocrinology & Metabolism 98, E1103E1108. Dwight, T., Na, U., Kim, E., Zhu, Y., Richardson, A.L., Robinson, B.G., Tucker, K.M., Gill, A.J., Benn, D.E., Clifton-Bligh, R.J., Winge, D.R., 2017. Analysis of SDHAF3 in familial and sporadic pheochromocytoma and paraganglioma. BMC Cancer 17, 497. Eng, C., Kiuru, M., Fernandez, M.J., Aaltonen, L.A., 2003. A role for mitochondrial enzymes in inherited neoplasia and beyond. Nature Reviews Cancer 3, 193. Esteban, M.A., Maxwell, P.H., 2005. HIF, a missing link between metabolism and cancer. Nature Medicine 11, 1047. Ghezzi, D., Goffrini, P., Uziel, G., Horvath, R., Klopstock, T., Lochmüller, H., D'Adamo, P., Gasparini, P., Strom, T.M., Prokisch, H., 2009a. SDHAF1, encoding a LYR complex-II specific assembly factor, is mutated in SDH-defective infantile leukoencephalopathy. Nature genetics 41, 654-656. Ghezzi, D., Goffrini, P., Uziel, G., Horvath, R., Klopstock, T., Lochmüller, H., D'Adamo, P., Gasparini, P., Strom, T.M., Prokisch, H., Invernizzi, F., Ferrero, I., Zeviani, M., 2009b. SDHAF1, encoding a LYR complexII specific assembly factor, is mutated in SDH-defective infantile leukoencephalopathy. Nature Genetics 41, 654. Goffrini, P., Ercolino, T., Panizza, E., Giachè, V., Cavone, L., Chiarugi, A., Dima, V., Ferrero, I., Mannelli, M., 2009. Functional study in a yeast model of a novel succinate dehydrogenase subunit B gene germline missense mutation (C191Y) diagnosed in a patient affected by a glomus tumor. Human Molecular Genetics 18, 1860-1868. Grimm, S., 2013. Respiratory chain complex II as general sensor for apoptosis. Biochimica et Biophysica Acta (BBA) - Bioenergetics 1827, 565-572. Guzy, R.D., Sharma, B., Bell, E., Chandel, N.S., Schumacker, P.T., 2008. Loss of the SdhB, but Not the SdhA, Subunit of Complex II Triggers Reactive Oxygen Species-Dependent Hypoxia-Inducible Factor Activation and Tumorigenesis. Molecular and Cellular Biology 28, 718-731. Hanahan, D., Weinberg, Robert A., 2011. Hallmarks of Cancer: The Next Generation. Cell 144, 646-674. Hao, H.X., Khalimonchuk, O., Schraders, M., Dephoure, N., Bayley, J.P., Kunst, H., Devilee, P., Cremers, C.W., Schiffman, J.D., Bentz, B.G., Gygi, S.P., Winge, D.R., Kremer, H., Rutter, J., 2009. SDH5, a gene required for flavination of succinate dehydrogenase, is mutated in paraganglioma. Science 325, 11391142. Hoekstra, A.S., Hensen, E.F., Jordanova, E.S., Korpershoek, E., 2017. Loss of maternal chromosome 11 is a signature event in SDHAF2, SDHD, and VHL-related paragangliomas, but less significant in SDHBrelated paragangliomas. Oncotarget 8, 14525. Hwang, M.-S., Rohlena, J., Dong, L.-F., Neuzil, J., Grimm, S., 2014. Powerhouse down: Complex II dissociation in the respiratory chain. Mitochondrion 19, 20-28. Iverson, T.M., Maklashina, E., Cecchini, G., 2012. Structural Basis for Malfunction in Complex II. Journal of Biological Chemistry 287, 35430-35438. Jackson, C.B., Nuoffer, J.-M., Hahn, D., Prokisch, H., Haberberger, B., Gautschi, M., Häberli, A., Gallati, S., Schaller, A., 2013. Mutations in SDHD lead to autosomal recessive encephalomyopathy and isolated mitochondrial complex II deficiency. Journal of medical genetics, J Med Genet-2013-101932. Jardim-Messeder, D., Caverzan, A., Rauber, R., Souza Ferreira, E., Margis-Pinheiro, M., Galina, A., 2015. Succinate dehydrogenase (mitochondrial complex II) is a source of reactive oxygen species in plants and regulates development and stress responses. New Phytologist 208, 776-789. Johnstone, M., Han, A., Bennett, N., Standifer, C., Smith, A., Donohoe, D., 2016. Characterization of the Pro-inflammatory Cytokine IL-1β on Butyrate Oxidation in Colorectal Cancer Cells. The FASEB Journal 30, 688.686-688.686.

24

Jo

ur na

lP

re

-p

ro

of

Kerscher, S., Grgic, L., Garofano, A., Brandt, U., 2004. Application of the yeast Yarrowia lipolytica as a model to analyse human pathogenic mutations in mitochondrial complex I (NADH:ubiquinone oxidoreductase). Biochimica et Biophysica Acta (BBA) - Bioenergetics 1659, 197-205. King, A., Selak, M.A., Gottlieb, E., 2006. Succinate dehydrogenase and fumarate hydratase: linking mitochondrial dysfunction and cancer. Oncogene 25, 4675. Kluckova, K., Bezawork-Geleta, A., Rohlena, J., Dong, L., Neuzil, J., 2013. Mitochondrial complex II, a novel target for anti-cancer agents. Biochimica et Biophysica Acta 1827, 552-564. Kluckova, K., Sticha, M., Cerny, J., Mracek, T., Dong, L., Drahota, Z., Gottlieb, E., Neuzil, J., Rohlena, J., 2015. Ubiquinone-binding site mutagenesis reveals the role of mitochondrial complex II in cell death initiation. Cell death & disease 6, e1749. Korpershoek, E., Favier, J., Gaal, J., Burnichon, N., van Gessel, B., Oudijk, L., Badoual, C., Gadessaud, N., Venisse, A., Bayley, J.-P., van Dooren, M.F., de Herder, W.W., Tissier, F., Plouin, P.-F., van Nederveen, F.H., Dinjens, W.N.M., Gimenez-Roqueplo, A.-P., de Krijger, R.R., 2011. SDHA Immunohistochemistry Detects Germline SDHA Gene Mutations in Apparently Sporadic Paragangliomas and Pheochromocytomas. The Journal of Clinical Endocrinology & Metabolism 96, E1472-E1476. Kunst, H.P., Rutten, M.H., de Mönnink, J.-P., Hoefsloot, L.H., Timmers, H.J., Marres, H.A., Jansen, J.C., Kremer, H., Bayley, J.-P., Cremers, C.W., 2011. SDHAF2 (PGL2-SDH5) and hereditary head and neck paraganglioma. Clinical Cancer Research 17, 247-254. Lasserre, J.-P., Dautant, A., Aiyar, R.S., Kucharczyk, R., Glatigny, A., Tribouillard-Tanvier, D., Rytka, J., Blondel, M., Skoczen, N., Reynier, P., Pitayu, L., Rötig, A., Delahodde, A., Steinmetz, L.M., Dujardin, G., Procaccio, V., di Rago, J.-P., 2015. Yeast as a system for modeling mitochondrial disease mechanisms and discovering therapies. Disease Models & Mechanisms 8, 509-526. Laukka, T., Mariani, C.J., Ihantola, T., Cao, J.Z., Hokkanen, J., Kaelin, W.G., Godley, L.A., Koivunen, P., 2016. Fumarate and Succinate Regulate Expression of Hypoxia-inducible Genes via TET Enzymes. Journal of Biological Chemistry 291, 4256-4265. Lee, C.-H., Chang, J.S.-M., Syu, S.-H., Wong, T.-S., Chan, J.Y.-W., Tang, Y.-C., Yang, Z.-P., Yang, W.-C., Chen, C.-T., Lu, S.-C., Tang, P.-H., Yang, T.-C., Chu, P.-Y., Hsiao, J.-R., Liu, K.-J., 2015. IL-1β Promotes Malignant Transformation and Tumor Aggressiveness in Oral Cancer. Journal of Cellular Physiology 230, 875-884. Lee, S., Nakamura, E., Yang, H., Wei, W., Linggi, M.S., Sajan, M.P., Farese, R.V., Freeman, R.S., Carter, B.D., Kaelin, W.G., Jr., Schlisio, S., 2005a. Neuronal apoptosis linked to EglN3 prolyl hydroxylase and familial pheochromocytoma genes: developmental culling and cancer. Cancer Cell 8, 155-167. Lee, S., Nakamura, E., Yang, H., Wei, W., Linggi, M.S., Sajan, M.P., Farese, R.V., Freeman, R.S., Carter, B.D., Kaelin, W.G., Schlisio, S., 2005b. Neuronal apoptosis linked to EglN3 prolyl hydroxylase and familial pheochromocytoma genes: Developmental culling and cancer. Cancer Cell 8, 155-167. Li, S., Fell, S.M., Surova, O., Smedler, E., Wallis, K., Chen, Z.X., Hellman, U., Johnsen, J.I., Martinsson, T., Kenchappa, R.S., Uhlen, P., Kogner, P., Schlisio, S., 2016. The 1p36 Tumor Suppressor KIF 1Bbeta Is Required for Calcineurin Activation, Controlling Mitochondrial Fission and Apoptosis. Developmental cell 36, 164-178. Li, Y., Wang, L., Pappan, L., Galliher-Beckley, A., Shi, J., 2012. IL-1β promotes stemness and invasiveness of colon cancer cells through Zeb1 activation. Molecular Cancer 11, 87. Lussey-Lepoutre, C., Hollinshead, K.E., Ludwig, C., Menara, M., Morin, A., Castro-Vega, L.J., Parker, S.J., Janin, M., Martinelli, C., Ottolenghi, C., Metallo, C., Gimenez-Roqueplo, A.P., Favier, J., Tennant, D.A., 2015. Loss of succinate dehydrogenase activity results in dependency on pyruvate carboxylation for cellular anabolism. Nat Commun 6, 8784. MacKenzie, E.D., Selak, M.A., Tennant, D.A., Payne, L.J., Crosby, S., Frederiksen, C.M., Watson, D.G., Gottlieb, E., 2007. Cell-permeating alpha-ketoglutarate derivatives alleviate pseudohypoxia in succinate dehydrogenase-deficient cells. Mol Cell Biol 27, 3282-3289.

25

Jo

ur na

lP

re

-p

ro

of

Maio, N., Ghezzi, D., Verrigni, D., Rizza, T., Bertini, E., Martinelli, D., Zeviani, M., Singh, A., Carrozzo, R., Rouault, T.A., 2016. Disease-causing SDHAF1 mutations impair transfer of Fe-S clusters to SDHB. Cell metabolism 23, 292-302. Moosavi, B., Berry, E.A., Zhu, X.-L., Yang, W.-C., Yang, G.-F., 2019. The assembly of succinate dehydrogenase: a key enzyme in bioenergetics. Cellular and Molecular Life Sciences. Mu, X., Zhao, T., Xu, C., Shi, W., Geng, B., Shen, J., Zhang, C., Pan, J., Yang, J., Hu, S., Lv, Y., Wen, H., You, Q., 2017. Oncometabolite succinate promotes angiogenesis by upregulating VEGF expression through GPR91-mediated STAT3 and ERK activation. Oncotarget 8, 13174-13185. Murphy, Michael P., 2009. How mitochondria produce reactive oxygen species. Biochemical Journal 417, 1-13. Na, U., Yu, W., Cox, J., Bricker, Daniel K., Brockmann, K., Rutter, J., Thummel, Carl S., Winge, Dennis R., 2014. The LYR Factors SDHAF1 and SDHAF3 Mediate Maturation of the Iron-Sulfur Subunit of Succinate Dehydrogenase. Cell Metabolism 20, 253-266. Nannini, M., Urbini, M., Astolfi, A., Biasco, G., Pantaleo, M.A., 2017. The progressive fragmentation of the KIT/PDGFRA wild-type (WT) gastrointestinal stromal tumors (GIST). Journal of Translational Medicine 15, 113. Niemann, S., Müller, U., 2000. Mutations in SDHC cause autosomal dominant paraganglioma, type 3. Nature Genetics 26, 268. Ohlenbusch, A., Edvardson, S., Skorpen, J., Bjornstad, A., Saada, A., Elpeleg, O., Gärtner, J., Brockmann, K., 2012. Leukoencephalopathy with accumulated succinate is indicative of SDHAF1 related complex II deficiency. Orphanet Journal of Rare Diseases 7, 69. Paddenberg, R., Ishaq, B., Goldenberg, A., Faulhammer, P., Rose, F., Weissmann, N., Braun-Dullaeus, R.C., Kummer, W., 2003. Essential role of complex II of the respiratory chain in hypoxia-induced ROS generation in the pulmonary vasculature. American Journal of Physiology-Lung Cellular and Molecular Physiology 284, L710-L719. Panizza, E., Ercolino, T., Mori, L., Rapizzi, E., Castellano, M., Opocher, G., Ferrero, I., Neumann, H.P.H., Mannelli, M., Goffrini, P., 2013. Yeast model for evaluating the pathogenic significance of SDHB, SDHC and SDHD mutations in PHEO–PGL syndrome. Human Molecular Genetics 22, 804-815. Piccini, V., Rapizzi, E., Bacca, A., Di Trapani, G., Pulli, R., Giachè, V., Zampetti, B., Lucci-Cordisco, E., Canu, L., Corsini, E., Faggiano, A., Deiana, L., Carrara, D., Tantardini, V., Mariotti, S., Ambrosio, M.R., Zatelli, M.C., Parenti, G., Colao, A., Pratesi, C., Bernini, G., Ercolino, T., Mannelli, M., 2012. Head and neck paragangliomas: genetic spectrum and clinical variability in 79 consecutive patients. Endocrine-Related Cancer 19, 149-155. Pollard, P.J., Brière, J.J., Alam, N.A., Barwell, J., Barclay, E., Wortham, N.C., Hunt, T., Mitchell, M., Olpin, S., Moat, S.J., Hargreaves, I.P., Heales, S.J., Chung, Y.L., Griffiths, J.R., Dalgleish, A., McGrath, J.A., Gleeson, M.J., Hodgson, S.V., Poulsom, R., Rustin, P., Tomlinson, I.P.M., 2005. Accumulation of Krebs cycle intermediates and over-expression of HIF1α in tumours which result from germline FH and SDH mutations. Human Molecular Genetics 14, 2231-2239. Ralph, S.J., Moreno-Sánchez, R., Neuzil, J., Rodríguez-Enríquez, S., 2011. Inhibitors of Succinate: Quinone Reductase/Complex II Regulate Production of Mitochondrial Reactive Oxygen Species and Protect Normal Cells from Ischemic Damage but Induce Specific Cancer Cell Death. Pharmaceutical Research 28, 2695. Rea, S.L., Graham, B.H., Nakamaru-Ogiso, E., Kar, A., Falk, M.J., 2010. Bacteria, yeast, worms, and flies: Exploiting simple model organisms to investigate human mitochondrial diseases. Developmental Disabilities Research Reviews 16, 200-218. Renkema, G.H., Wortmann, S.B., Smeets, R.J., Venselaar, H., Antoine, M., Visser, G., Ben-Omran, T., Van Den Heuvel, L.P., Timmers, H.J., Smeitink, J.A., 2015. SDHA mutations causing a multisystem

26

Jo

ur na

lP

re

-p

ro

of

mitochondrial disease: novel mutations and genetic overlap with hereditary tumors. European Journal of Human Genetics 23, 202. Ricci, J.E., Gottlieb, R.A., Green, D.R., 2003. Caspase-mediated loss of mitochondrial function and generation of reactive oxygen species during apoptosis. The Journal of cell biology 160, 65-75. Rinaldi, T., Dallabona, C., Ferrero, I., Frontali, L., Bolotin-Fukuhara, M., 2010. Mitochondrial diseases and the role of the yeast models. FEMS Yeast Research 10, 1006-1022. Rustin, P., Munnich, A., Rötig, A., 2002. Succinate dehydrogenase and human diseases: new insights into a well-known enzyme. European Journal Of Human Genetics 10, 289. Rutter, J., Winge, D.R., Schiffman, J.D., 2010. Succinate dehydrogenase – Assembly, regulation and role in human disease. Mitochondrion 10, 393-401. Saito, Y., Ishii, K.-a., Aita, Y., Ikeda, T., Kawakami, Y., Shimano, H., Hara, H., Takekoshi, K., 2016. Loss of SDHB Elevates Catecholamine Synthesis and Secretion Depending on ROS Production and HIF Stabilization. Neurochemical Research 41, 696-706. Salminen, A., Kauppinen, A., Kaarniranta, K., 2015. 2-Oxoglutarate-dependent dioxygenases are sensors of energy metabolism, oxygen availability, and iron homeostasis: potential role in the regulation of aging process. Cellular and Molecular Life Sciences 72, 3897-3914. Sapieha, P., Sirinyan, M., Hamel, D., Zaniolo, K., Joyal, J.-S., Cho, J.-H., Honoré, J.-C., KermorvantDuchemin, E., Varma, D.R., Tremblay, S., Leduc, M., Rihakova, L., Hardy, P., Klein, W.H., Mu, X., Mamer, O., Lachapelle, P., Di Polo, A., Beauséjour, C., Andelfinger, G., Mitchell, G., Sennlaub, F., Chemtob, S., 2008. The succinate receptor GPR91 in neurons has a major role in retinal angiogenesis. Nature Medicine 14, 1067. Smestad, J., Hamidi, O., Wang, L., Holte, M.N., Khazal, F.A., Erber, L., Chen, Y., Maher, L.J., 3rd, 2018. Characterization and metabolic synthetic lethal testing in a new model of SDH-loss familial pheochromocytoma and paraganglioma. Oncotarget 9, 6109-6127. Smith, E.H., Janknecht, R., Maher, I.I.I.L.J., 2007. Succinate inhibition of α-ketoglutarate-dependent enzymes in a yeast model of paraganglioma. Human Molecular Genetics 16, 3136-3148. Szeto, S.S., Reinke, S.N., Sykes, B.D., Lemire, B.D., 2007. Ubiquinone-binding site mutations in the Saccharomyces cerevisiae succinate dehydrogenase generate superoxide and lead to the accumulation of succinate. The Journal of biological chemistry 282, 27518-27526. Tannahill, G.M., Curtis, A.M., Adamik, J., Palsson-McDermott, E.M., McGettrick, A.F., Goel, G., Frezza, C., Bernard, N.J., Kelly, B., Foley, N.H., Zheng, L., Gardet, A., Tong, Z., Jany, S.S., Corr, S.C., Haneklaus, M., Caffrey, B.E., Pierce, K., Walmsley, S., Beasley, F.C., Cummins, E., Nizet, V., Whyte, M., Taylor, C.T., Lin, H., Masters, S.L., Gottlieb, E., Kelly, V.P., Clish, C., Auron, P.E., Xavier, R.J., O’Neill, L.A.J., 2013. Succinate is an inflammatory signal that induces IL-1β through HIF-1α. Nature 496, 238. Taylor, J., Schmidt, J., Helman, G., Shibuya, P., Bloom, M., Rabin, J., Evans, S., Bai, R., Vanderver, A., 2013. Solving the Unsolved: Targeted Gene Panel Identifies SDH-Related Infantile Leukoencephalopathy (P02.090). Neurology 80, P02.090. Toledo, R.A., Qin, Y., Cheng, Z.M., Gao, Q., Iwata, S., Silva, G.M., Prasad, M.L., Ocal, I.T., Rao, S., Aronin, N., Barontini, M., Bruder, J., Reddick, R.L., Chen, Y., Aguiar, R.C., Dahia, P.L., 2016. Recurrent Mutations of Chromatin-Remodeling Genes and Kinase Receptors in Pheochromocytomas and Paragangliomas. Clinical cancer research: an official journal of the American Association for Cancer Research 22, 23012310. Tretter, L., Patocs, A., Chinopoulos, C., 2016. Succinate, an intermediate in metabolism, signal transduction, ROS, hypoxia, and tumorigenesis. Biochimica et Biophysica Acta (BBA) - Bioenergetics 1857, 1086-1101. Van Vranken, J.G., Na, U., Winge, D.R., Rutter, J., 2015. Protein-mediated assembly of succinate dehydrogenase and its cofactors. Critical Reviews in Biochemistry and Molecular Biology 50, 168-180.

27

Jo

ur na

lP

re

-p

ro

of

Van Vranken, Jonathan G., Bricker, Daniel K., Dephoure, N., Gygi, Steven P., Cox, James E., Thummel, Carl S., Rutter, J., 2014. SDHAF4 Promotes Mitochondrial Succinate Dehydrogenase Activity and Prevents Neurodegeneration. Cell Metabolism 20, 241-252. Wentzel, J.F., Lewies, A., Bronkhorst, A.J., van Dyk, E., du Plessis, L.H., Pretorius, P.J., 2017. Exposure to high levels of fumarate and succinate leads to apoptotic cytotoxicity and altered global DNA methylation profiles in vitro. Biochimie 135, 28-34. Wojtovich, A.P., Smith, C.O., Haynes, C.M., Nehrke, K.W., Brookes, P.S., 2013. Physiological consequences of complex II inhibition for aging, disease, and the mKATP channel. Biochimica et Biophysica Acta (BBA) - Bioenergetics 1827, 598-611. Xiao, M., Yang, H., Xu, W., Ma, S., Lin, H., Zhu, H., Liu, L., Liu, Y., Yang, C., Xu, Y., Zhao, S., Ye, D., Xiong, Y., Guan, K.-L., 2012. Inhibition of α-KG-dependent histone and DNA demethylases by fumarate and succinate that are accumulated in mutations of FH and SDH tumor suppressors. Genes & Development 26, 1326-1338. Yankovskaya, V., Horsefield, R., Törnroth, S., Luna-Chavez, C., Miyoshi, H., Léger, C., Byrne, B., Cecchini, G., Iwata, S., 2003. Architecture of Succinate Dehydrogenase and Reactive Oxygen Species Generation. Science 299, 700-704. Zhao, T., Mu, X., You, Q., 2017. Succinate: An initiator in tumorigenesis and progression. Oncotarget 8, 53819-53828. Zhou, Z., Ibekwe, E., Chornenkyy, Y., 2018. Metabolic Alterations in Cancer Cells and the Emerging Role of Oncometabolites as Drivers of Neoplastic Change. Antioxidants 7, 16. Zhu, W., Wang, Z., Chai, Y., Wang, X., Chen, D., Wu, H., 2015. Germline mutations and genotype– phenotype associations in head and neck paraganglioma patients with negative family history in China. European journal of medical genetics 58, 433-438. 28

ro

of

Figures legends

-p

Figure 1: The link between oxidative phosphorylation and Tricarboxylic acid cycle

re

(TCA). Oxidative phosphorylation joints electron transport through respiratory chain complexes including Complex I, II, III, and IV to ATP synthesis. For simplicity, only

Jo

ur na

lP

Complexes I, II, and III are shown.

Figure 2: Succinate signaling pathways that lead to tumorigenesis.

29

ro

of Jo

ur na

lP

re

-p

Figure 3: The links between succinate and apoptosis.

Figure 4: The links between succinate and GPCR signaling.

30

of ro

Jo

ur na

lP

re

-p

Figure 5: A mind map summary of the topics discussed in this article.

31