Mitochondrial Complex V Dysfunction in Neurodegeneration: Secondary Bystander or Primary Driver?

Background/Objectives: Mitochondrial Complex V (Complex V [CX-V], or ATP synthase) is the terminal enzyme of oxidative phosphorylation and is responsible for the majority of cellular ATP production. An increasing body of evidence suggests that CX-V dysfunction may contribute to mitochondrial impairment observed in neurodegenerative disease. This review evaluated current research on the structure, regulation, and function of CX-V, examined the consequences of CX-V dysfunction, and assessed its proposed role in neurodegenerative disorders. Methods: A comprehensive review of the published literature was carried out, with emphasis on primary research investigating CX-V structure and function, inherited CX-V disorders, and experimental evidence linking CX-V dysfunction to neurodegenerative disease. The reviewed studies used a range of experimental approaches, including structural biology, biochemical studies, patient-derived cellular models, animal models and post-mortem human tissue. Results: Current evidence demonstrates that disruption of CX-V impairs ATP production, alters mitochondrial membrane potential, and oxidative phosphorylation, and that pathogenic variants cause primary mitochondrial disease. Across Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis/frontotemporal dementia, glaucoma and inherited optic neuropathies, alterations in CX-V activity, regulation and structural integrity are consistently associated with mitochondrial dysfunction. Direct evidence supporting CX-V as a primary driver of neurodegeneration remains very limited, with many observations originating from broader studies of general mitochondrial dysfunction. Conclusions: CX-V dysfunction represents a recurring feature of mitochondrial impairment across a variety of neurodegenerative disorders and may exacerbate neuronal vulnerability by disrupting cellular bioenergetics. Current evidence indicates that CX-V may serve as a common downstream target of multiple pathological pathways rather than acting as a primary pathological factor. Future studies require direct assessment of CX-V activity in clinically relevant human models and patient tissues to determine its contribution to disease progression and examine its potential as a therapeutic target.