[SDHC](/genes/sdhc) encodes one of the membrane-anchoring subunits of mitochondrial Complex II (succinate dehydrogenase, SDH), the only respiratory-chain complex that is also a tricarboxylic acid (TCA) cycle enzyme. SDHC, together with SDHD, forms the membrane arm that receives electrons from SDHB and transfers them to ubiquinone. This dual TCA/OXPHOS position makes SDHC biologically important for both energy metabolism and redox signaling in the central nervous system.
Pathogenic SDHC variants are classically associated with hereditary paraganglioma syndromes, but SDH axis dysfunction is increasingly relevant to neurodegeneration research through mechanisms that include mitochondrial stress, succinate accumulation, pseudohypoxic signaling, and inflammatory rewiring.[@tretter2004][@letouz2013] In degenerative brain disease, these pathways intersect with [oxidative stress](/mechanisms/oxidative-stress), [neuroinflammation](/mechanisms/neuroinflammation-pathway), and impaired mitochondrial quality control.[@tretter2004][@lin2006]
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SDHC Protein
[SDHC](/genes/sdhc) encodes one of the membrane-anchoring subunits of mitochondrial Complex II (succinate dehydrogenase, SDH), the only respiratory-chain complex that is also a tricarboxylic acid (TCA) cycle enzyme. SDHC, together with SDHD, forms the membrane arm that receives electrons from SDHB and transfers them to ubiquinone. This dual TCA/OXPHOS position makes SDHC biologically important for both energy metabolism and redox signaling in the central nervous system.
Pathogenic SDHC variants are classically associated with hereditary paraganglioma syndromes, but SDH axis dysfunction is increasingly relevant to neurodegeneration research through mechanisms that include mitochondrial stress, succinate accumulation, pseudohypoxic signaling, and inflammatory rewiring.[@tretter2004][@letouz2013] In degenerative brain disease, these pathways intersect with [oxidative stress](/mechanisms/oxidative-stress), [neuroinflammation](/mechanisms/neuroinflammation-pathway), and impaired mitochondrial quality control.[@tretter2004][@lin2006]
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SDHC Protein
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Complex II catalyzes succinate oxidation to fumarate while funneling electrons into the ubiquinone pool.[@sun2005][@rutter2010] SDHC contributes to membrane anchoring and proper positioning of electron transfer components required for efficient coupling.[@sun2005][@yankovskaya2003] Disruption of SDHC can impair Complex II flux, alter mitochondrial membrane redox dynamics, and increase susceptibility to [ROS](/entities/reactive-oxygen-species)-mediated damage under metabolic stress.[@rutter2010][@tretter2004]
Compared with Complex I defects, SDHC dysfunction often presents with a different biochemical signature, including succinate-related signaling consequences that can extend beyond ATP production deficits.[@tretter2004][@letouz2013] This signaling dimension is particularly important in chronic disease states where metabolic and inflammatory programs co-evolve.
[Neurons](/entities/neurons) and glia rely on coordinated TCA-cycle and respiratory-chain function for neurotransmission, ion-gradient maintenance, and proteostasis.[@rutter2010][@lin2006] SDHC dysfunction can reduce metabolic flexibility and compromise adaptation to stressors such as excitotoxic load, inflammatory cytokines, and hypoxic episodes.[@tretter2004][@lin2006]
Accumulated succinate may also influence microglial and astrocytic inflammatory tone through immunometabolic pathways, potentially amplifying secondary neurodegenerative cascades.[@tretter2004][@letouz2013]
Germline SDHC variants are established drivers of hereditary paraganglioma/pheochromocytoma syndromes.[@letouz2013][@ricketts2016] In these disorders, SDH impairment promotes oncometabolic signaling and epigenetic rewiring, illustrating how mitochondrial enzyme defects can reshape cell-state programs.
Although SDHC is not a major monogenic cause of common AD/PD/ALS syndromes, the SDH pathway remains relevant because succinate metabolism, mitochondrial ROS, and inflammatory bioenergetics are recurrent motifs across neurodegenerative models.[@tretter2004][@lin2006] This makes SDHC a useful mechanistic node for hypothesis-driven studies in mixed pathologies and biomarker development.
There is no SDHC-specific approved neurodegeneration therapy. Current translational interest centers on pathway-level interventions:
For SDHC-axis dysfunction, biomarker frameworks should integrate metabolic, genomic, and inflammatory readouts rather than relying on one molecular feature. Succinate-related signatures may complement classical imaging and clinical progression markers in translational studies.[@tretter2004][@letouz2013]
SDHC biology is increasingly useful for understanding how mitochondrial metabolism shapes immune tone in the brain. When Complex II throughput is constrained, succinate can accumulate and function as a signaling metabolite rather than only a TCA intermediate.[@tretter2004][@letouz2013] In myeloid-like states, this shift supports pro-inflammatory programming and oxidative stress amplification, processes that are also observed in chronic neurodegenerative microenvironments.[@tretter2004][@lin2006]
This provides a mechanistic bridge between classical mitochondrial defects and modern immunometabolism frameworks. Rather than viewing SDHC dysfunction as purely energetic, it is more accurate to model it as a state transition driver that changes transcriptional and epigenetic programs under stress.[@letouz2013][@ricketts2016]
In neural circuits, SDHC dysfunction can couple reduced respiratory efficiency with altered glial-neuronal crosstalk. Neurons may face lower stress tolerance, while glia may adopt persistent inflammatory phenotypes sustained by altered mitochondrial substrate handling.[@tretter2004][@lin2006] Over time, this combination can lower resilience to proteotoxic and synaptic insults that define disorders such as [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), and related tauopathies.[@tretter2004][@lin2006]
Key translational implications include:
SDHC-focused translational work benefits from models that capture both metabolic and inflammatory outputs. Recommended systems include SDHC-perturbed cell models with integrated flux and cytokine profiling, neuron-glia co-cultures for stress-response mapping, and longitudinal in vivo paradigms where mitochondrial and behavioral phenotypes can be jointly tracked.[@rutter2010][@tretter2004]
For clinical studies, endpoint packages should include metabolic markers (for example succinate-related signatures), inflammatory markers, and functional neurologic measures. This multimodal approach is more likely to detect biologically meaningful responses than single-domain readouts.[@tretter2004][@letouz2013] It also aligns with the reality that SDHC-associated dysfunction propagates through coupled pathways, not isolated molecular defects.[@letouz2013][@lin2006]