Loss of succinyl-CoA synthase ADP-forming β subunit disrupts mtDNA stability and mitochondrial dynamics in neurons

Abstract

Succinyl Coenzyme A synthetase (SCS) is a key mitochondrial enzyme. Defected SCS ADP-forming β subunit (SCS A-β) is linked to lethal infantile Leigh or leigh-like syndrome. However, the impacts of SCS A-β deficiency on mitochondria specifically in neurons have not yet been comprehensively investigated. Here, by down-regulating the expression levels of SCS A-β in cultured mouse neurons, we have found that SCS A-β deficiency induces severe mitochondrial dysfunction including lowered oxidative phosphorylation (OXPHOS) efficiency, increased mitochondrial superoxide production, and mtDNA depletion as well as aberrations of mitochondrial fusion and fission proteins, which eventually leads to neuronal stress. Our data also suggest that the deregulation of mitochondrial nucleoside diphosphate kinase (NDPK) together with defects in mitochondrial transcription factors including mitochondrial DNA pol γ and Twinkle contribute to SCS A-β deficiency-mediated mtDNA instability. Furthermore, we have found that SCS A-β deficiency has detrimental influence on neuronal mitochondrial dynamics. Put together, the results have furnished our knowledge on the pathogenesis of SCS A-β deficiency-related mitochondrial diseases and revealed the vital role of SCS A-β in maintaining neuronal mitochondrial quality control and neuronal physiology.

Endonuclease G promotes mitochondrial genome cleavage and replication

“…HeLa cells were cultured on glass slides (12 mm, VWR), fixed with 3.7% Formaldehyde (AppliChem Panreac ITW companies), permeabilised with 0.5% Triton X-100 (Sigma-Aldrich), washed shortly with 0.05% Tween-20 (Merck) and blocked with 5% goat serum (Sigma-Aldrich) to avoid unspecific binding. For immunostaining slides were incubated for 1 h with the following primary antibodies (all from Santa Cruz): rabbit-anti-human mtSSB (sc-67101 [ 98 ]), TWINKLE (sc-134915 [ 99 ]) and APE1 (sc-334 [ 54 ]) as well as mouse-anti-human MFN2 (sc-100560 [ 100 ]) and OPA1 (sc-393296 [ 101 ]). Alexa Fluor 555 anti-mouse, Alexa Fluor 555 anti-rabbit and Alexa Fluor 488 anti-rabbit (all from Invitrogen) were used as secondary antibodies.…”

Metabolic stress is a primary pathogenic event in transgenic Caenorhabditis elegans expressing pan-neuronal human amyloid beta

“…The accumulation of aKG, coupled with the reduction in fumarate and malate, is consistent with a reduction in the activity of aKG dehydrogenase (aKGDH) or with alterations in enzymes downstream of aKG. Among those downstream enzymes, Succinyl CoA Synthetase (SCS) is an important regulator of mitochondrial integrity including in neurons (Zhao et al, 2017). Increased levels of another downstream enzyme, Malate Dehydrogenase (MDH), have previously been found in the brain of AD patients (Paterson et al, 2016).…”

Metabolic stress is a primary pathogenic event in transgenic Caenorhabditis elegans expressing pan-neuronal human amyloid beta

“…The accumulation of a-KG, coupled with the reduction in fumarate and malate, is consistent with a reduction in the activity of aKG dehydrogenase (aKGDH) or with alterations in enzymes downstream of aKG. Among those downstream enzymes, Succinyl CoA Synthetase (SCS) is an important regulator of mitochondrial integrity including in neurons 47 . Increased levels of another downstream enzyme, Malate Dehydrogenase (MDH), have previously been found in the brain of AD patients 48 .…”