Mitochondrial Morphology During Stress is Regulated by GJA1-20k Interaction With Actin

Connexin (Cx) 43 is encoded by the GJA1 gene and GJA1-20k has been identified as an N-terminal truncation of Cx43 generated endogenously by internal translation. Previously we have found GJA1-20k increases with ischemic stress and induces actin organization and, in mice, mitochondrial biogenesis. In this study we explored the acute effect of GJA1-20k on mitochondria. We transfected GFP-tagged GJA1-20k plasmid into HEK293T cells and analyzed mitochondrial morphology by fluorescent microscopy. We found GJA1-20k results in mitochondria that are associated with actin and also are smaller and more circular than in GST-transfected control cells. In addition, quantitative analysis indicated preservation of mitochondrial area and thus enhanced mitochondrial fission in the presence of GJA1-20k. Disruption of actin polymerization inhibited the effect of GJA1-20k on mitochondrial fission as did use of the actin stabilizer phalloidin, indicating the need for robust actin dynamics for GJA1-20k to be effective. These data suggest that the interaction between GJA1-20k and actin cytoskeleton is necessary for stress related mitochondrial fission. The results indicate that, during stress, upregulated GJA1-20k recruits the actin cytoskeleton to directly affect mitochondrial dynamics and cellular metabolic function.