Mitochondria-ER contact sites expand during mitosis

Abstract

Mitochondria-ER contact sites (MERCS) are involved in energy homeostasis, redox and Ca 2+ signaling, and inflammation. MERCS are heavily studied; however, little is known about their regulation during mitosis. Here, we show that MERCS expand during mitosis in three cell types using various approaches, including transmission electron microscopy, serial EM coupled to 3D reconstruction, and a split GFP MERCS marker. We further show enhanced Ca 2+ transfer between the ER and mitochondria using either direct Ca 2+ measurements or by quantifying the activity of Ca 2+ -dependent mitochondrial dehydrogenases. Collectively, our results support a lengthening of MERCS in mitosis that is associated with improved Ca 2+ coupling between the two organelles. This augmented Ca 2+ coupling could be important to support the increased energy needs of the cell during mitosis.