Dynamin and caveolae in cardiac ischemic preconditioning

Caveolae are specialized membranes enriched in lipids and proteins that regulate numerous signaling processes. Caveolae participate in clathrin‐independent endocytosis that is regulated by dynamin‐2, large GTPase proteins that induce membrane fission. We have previously shown that ischemic preconditioning (IPC) induces protection in cardiac myocytes via modulated formation of caveolae; however, the dynamics of caveolae formation and internalization by IPC is unknown. We hypothesize that IPC leads to the localization of dynamin to caveolae in cardiac myocytes. Adult male mice underwent 5 minutes of cardiac ischemia followed by 15 minutes of reperfusion or 20 minutes of sham surgery. For cell fractionation and SDS‐PAGE analysis, hearts were excised and homogenized in sodium carbonate buffer. The hearts that were used for immunofluorescence experiments were perfused and prepared for cryo‐sectioning. Western blot analysis of whole cell lysates confirmed equal dynamin expression in both samples. Following cell fractionation, there were higher levels of dynamin in caveolae rich fractions of IPC samples than in sham samples. Immunofluorescence images showed decreased cytosolic dynamin and increased amounts of dynamin along the plasma membrane, with caveolin‐3 co‐localization in IPC cardiac myocytes relative to sham cardiac myocytes. Our data suggests that IPC causes cytosolic dynamin to migrate to caveolae in cadiac myocytes, such migration may be key to modulation of caveolar mobilization from the plasma membrane that can affect cardiac protection.