ATL2 Recruits TRAK1 to Promote Mitochondrial Transport at ER–Mitochondria Contact Sites

Mitochondrial transport and distribution are crucial for cellular homeostasis, yet whether and how they are regulated by endoplasmic reticulum (ER)-mitochondria contact sites remains unclear. Here, we demonstrate that the ER protein atlastin-2 (ATL2) orchestrates mitochondrial transport and distribution by promoting assembly of the transport machinery at ER-mitochondria contact sites. Mechanistically, ATL2 recruits the adaptor trafficking kinesin-binding protein 1 (TRAK1) to the ER membrane, strengthening the interaction of TRAK1 with the mitochondrial transport adaptor MIRO1 to promote anterograde mitochondrial transport. Loss of ATL2 disrupts this process, leading to perinuclear mitochondrial clustering. We further find that ATL2 stabilizes ER-mitochondria contact sites by interacting with MFN2, providing a platform for mitochondrial transport complex assembly. Moreover, in hypoxia, ATL2 is ubiquitinated at lysine 567 by the E3 ligase SYVN1, leading to its degradation and a resulting defect in mitochondrial distribution. Our findings elucidate a novel ER-mediated mechanism for mitochondrial transport.