The Mystery of Extramitochondrial Proteins Lysine Succinylation.

Lysine succinylation is a post-translational modification which alters protein function in both physiological and pathological processes. Mindful that it requires succinyl-CoA, a metabolite formed within the mitochondrial matrix that cannot permeate the inner mitochondrial membrane, the question arises as to how there can be succinylation of proteins outside mitochondria. The present mini-review examines pathways participating in peroxisomal fatty acid oxidation that lead to succinyl-CoA production, potentially supporting succinylation of extramitochondrial proteins. Furthermore, the influence of the mitochondrial status on cytosolic NAD availability affecting the activity of cytosolic SIRT5 iso1 and iso4-in turn regulating cytosolic protein lysine succinylations-is presented. Finally, the discovery that glia in the adult human brain lack subunits of both alpha-ketoglutarate dehydrogenase complex and succinate-CoA ligase-thus being unable to produce succinyl-CoA in the matrix-and yet exhibit robust pancellular lysine succinylation, is highlighted.