ER-Mitochondria Contact Sites expand during mitosis

Membrane contact sites between various organelles define specialized spatially defined signaling hubs, they are of great interest to better understand inter-organelle communication and its implications on cellular physiology. ER-mitochondria contact sites (ERMCS) are one of the best studied and mediate Ca 2+ signaling that regulates mitochondrial bioenergetics. However, little is known about ERMCS during mitosis. Here we show that ERMCS expand during mitosis using transmission electron microscopy, serial EM coupled to 3D reconstruction, and ERMCS markers. ERMCS expansion in mitosis is functionally significant as it is associated with enhanced Ca 2+ coupling between the ER and mitochondria resulting in heightened activation of mitochondrial dehydrogenases. Our data suggest that ERMCS remodeling in mitosis is important to meet the increased energy needs during cell division.