Cnm1: A bridge between mitochondria and nuclear ER

Abstract

Few membrane contact sites have been defined at the molecular level. By using a high-throughput, microscopy-based screen, Eisenberg-Bord, Zung et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202104100) identify Cnm1 as a novel tethering protein that mediates contact between mitochondria and the nuclear ER in response to phospholipid levels.

Figure 1.

The ER and vacuole form multiple MCSs with mitochondria in budding yeast. The ER is depicted in green, and the mitochondrial network is depicted in gray. ERMES mediates an MCS between tubular ER and mitochondria. In addition to functions that are distinct from lipid trafficking, ERMES-mediated MCSs likely function to transport PS or PE between the organelles. Cnm1 mediates an MCS specifically between the nuclear ER and mitochondria and potentially functions in PC transport. The Vps13-Mcp1 vCLAMP mediates an MCS between mitochondria and the vacuole that likely functions in lipid transport and may have redundant functions with ERMES. The Vps39-Tom40 vCLAMP is a separate MCS between mitochondria and the vacuole that responds to different stress conditions, though its function is unknown.