GJA1-20k

**GJA1-20k** is an endogenous 20 kDa N-terminal truncated isoform of connexin-43 (Cx43, encoded by GJA1), generated via internal ribosome entry site-mediated translation from the same mRNA. It is a non-membrane-bound stress-response peptide that localizes to mitochondria and actin cytoskeleton, inducing non-canonical mitochondrial fission by stabilizing polymerized actin filaments around mitochondria, independent of DRP1. This results in smaller mitochondria with reduced reactive oxygen species (ROS) production, lower oxygen consumption, and metabolic quiescence, mimicking ischemic preconditioning to protect against ischemia-reperfusion (I/R) injury in heart, brain, and other organs. GJA1-20k also acts as an auxiliary trafficking subunit for full-length Cx43 to intercalated discs, maintaining gap junction intercellular communication (GJIC) and reducing arrhythmias. It is upregulated in response to ischemic stress and has been delivered therapeutically via AAV9 gene therapy or proposed as an intravenous peptide infusion ahead of anticipated ischemia. Developers include academic groups at University of Utah and others studying cardioprotection.[1][2][5][7]