Fig. 6

Potential mechanism by which cells capture and internalize exogenous mitochondria. Exogenous mitochondria are internalized into the cell via actin-related endocytosis or macropinocytosis. Macropinocytosis occurs in a nonselective manner. Following internalization, mitochondria are transported to endosomes and lysosomes. In cardiomyocytes, exogenous mitochondria can escape from these cellular compartments and integrate into the endogenous mitochondrial network, which necessitates the coordinated actions of MFN1, MFN2 and OPA1 to facilitate mitochondrial fusion in cardiomyocytes and fibroblasts. Some mitochondria are degraded by fusion with lysosomes and endosomes. Most exogenous mitochondria can escape from endosomes or lysosomes and fuse with the endogenous mitochondrial network through a process mediated by MFN1, MFN2, and OPA1