Abstract P3178: Gja1-20k Is Downstream Of Drp1 And Can Rescue Drp1 Suppression In Mouse Heart

Abstract

Dynamin-Related Protein 1 (DRP1) is a major mediator of mitochondrial fission and its mutation results with hyper-fused mitochondria and, in mice, a dilated cardiomyopathy. GJA1-20k is the most abundant N-terminus truncated isoform of Connexin 43 (Cx43) formed by internal translation and was originally identified as a trafficking subunit of Cx43. It has been recently identified that GJA1-20k is located on the mitochondrial membrane and plays a role in mediating ischemia preconditioning by promoting a protective mitochondrial fission. Interestingly, GJA1-20k mediated fission occurs even under DRP1 inhibition in vitro. Here, we hypothesize that GJA1-20k is downstream of DRP1 and that exogenous GJA1-20k administration rescues hyper-fusion of mitochondria in DRP1-suppressed mouse hearts. Using an AAV9-mediated DRP1 dominant negative mutant (Drp1-K38A) to suppress DRP1, we confirmed that the Drp1-K38A mouse hearts have an increase in cardiac mitochondrial size (158.9 ± 3.7% of control) and decrease in cardiac function (ejection fraction is 43.1 ± 1.5% versus 64.0 ± 4.1% in control animals), as assayed by electron microscopy and in vivo echocardiography, respectively. However, the administration of exogenous GJA1-20k via AAV9 transduction normalizes mitochondrial size (net 14.1 ± 3.3% decrease from control group) and rescues cardiac function (ejection fraction 61.6 ± 2.7%), suggesting that the progression to the cardiomyopathy is prevented by GJA1-20k administration. In summary, GJA1-20k functions downstream of DRP1 and can rescue the effect DRP1 suppression on mitochondrial size and cardiac function.