Vps13-Mcp1 interact at vacuole-mitochondria interfaces and bypass ER-mitochondria contact sites

Membrane contact sites between endoplasmic reticulum (ER) and mitochondria, mediated by the ER-mitochondria encounter structure (ERM ES) complex, are critical for mitochondrial homeostasis and cell growth. Defects in ERM ES can, however, be bypassed by point mutations in the endosomal protein Vps13 or by overexpression of the mitochondrial protein Mcp1. How this bypass operates remains unclear. Here we show that the mitochondrial outer membrane protein Mcp1 functions in the same pathway as Vps13 by recruiting it to mitochondria and promoting its association to vacuole-mitochondria contacts. Our findings support a model in which Mcp1 and Vps13 work as functional effectors of vacuole-mitochondria contact sites, while tethering is mediated by other factors, including Vps39. Tethered and functionally active vacuole-mitochondria interfaces then compensate for the loss of ERM ES-mediated ER-mitochondria contact sites.