ER Tubules Mark Sites of Mitochondrial Division

TLDR

Mitochondrial division, driven by Dnm1/Drp1, is regulated at the network level, yet the determinants of fission sites remain unclear, despite the close dynamic coupling between the endoplasmic reticulum and mitochondria. We tested whether the endoplasmic reticulum influences mitochondrial division. We observed that mitochondrial fission occurs at ER tubule contact sites, where ER-mediated constriction precedes Drp1 recruitment, indicating that ER tubules actively define division sites.

Abstract

Mitochondrial structure and distribution are regulated by division and fusion events. Mitochondrial division is regulated by Dnm1/Drp1, a dynamin-related protein that forms helices around mitochondria to mediate fission. Little is known about what determines sites of mitochondrial fission within the mitochondrial network. The endoplasmic reticulum (ER) and mitochondria exhibit tightly coupled dynamics and have extensive contacts. We tested whether ER plays a role in mitochondrial division. We found that mitochondrial division occurred at positions where ER tubules contacted mitochondria and mediated constriction before Drp1 recruitment. Thus, ER tubules may play an active role in defining the position of mitochondrial division sites.