A Micropeptide Component of the OGDH Complex Modulates ATP Production in the TCA Cycle.

Since its elucidation, the tricarboxylic acid (TCA) cycle has been regarded as a fully defined enzymatic pathway. Here, we report the discovery of a previously unrecognized micropeptide component of this central metabolic system. Through analyzing ribosome profiling data from the mouse sORFs.org database, we discovered APPM (ATP production-promoting micropeptide), a 29-amino acid peptide encoded by a non-canonical small open reading frame within the mouse Ctsb gene. APPM localizes to the mitochondrial matrix and inner membrane, where it directly binds to the E1 subunit (OGDH) of the α-ketoglutarate dehydrogenase complex (OGDHc). This interaction modulates OGDHc enzymatic activity, thereby regulating NADH and ATP production. We identified tyrosine-13 as the critical residue mediating the APPM-OGDH interaction and functional activation. Exogenous APPM administration increased ATP levels in vivo and, in a mouse model of heart failure, restored cardiac function, outperforming the reference drug trimetazidine. Collectively, our findings identify APPM as the first micropeptide regulator of the OGDH complex, expanding the known repertoire of the TCA cycle and presenting a potential therapeutic strategy for diseases characterized by bioenergetic insufficiency.