Abstract P3057: Heat Shock Protein Is Involved In Gja1-20k Transport To Mitochondria

GJA1-20k is an internally translated, N-terminus truncated isoform of the gap junction protein Connexin 43 (Cx43). We have identified essential roles of GJA1-20k for Cx43 trafficking to cell membrane, actin stabilization, and regulation of mitochondrial dynamics. Recently, we found that GJA1-20k works with actin to induce a “protective” mitochondrial fission, protecting cells and hearts against ischemia-reperfusion (I/R) injury. This GJA1-20k mediated mitochondrial fission does not require the canonical fission mediator, Dynamin-Related Protein 1 (DRP1) pathway. At present, however, little is known how GJA1-20k occurs at mitochondrial membrane. Our in silico analysis indicates that the N-terminus of GJA1-20k contains a potent binding site to Heat Shock Protein 70 (HSP70). Since HSP70 is a well known mitochondrial transporter, we hypothesized that HSP70 interacts with GJA1-20k to support its translocation to mitochondria. To explore the involvement of HSP70, in HeLa cells we knocked down HSP70 in the presence of exogenous GJA1-20k. An absence of HSP70 inhibited GJA1-20k localization to mitochondrial membrane. In fact, in the absence of HSP70, most GJA1-20k was aggregated, suggesting a failure to distribute. Given that the expression of both HSP70 and GJA1-20k are upregulated during I/R injury, these data indicate that both stress-response proteins cooperate to localize GJA1-20k to mitochondrial membrane, initiating protective mitochondrial fission.