The UbiB family member Cqd1 forms a novel membrane contact site in mitochondria

Abstract

Mitochondria are essential organelles of eukaryotic cells that are characterized by their unique and complex membrane system. They are confined from the cytosol by an envelope consisting of two membranes. Signals, metabolites, proteins and lipids have to be transferred across these membranes via proteinaceous contact sites to keep mitochondria functional. In the present study we identified a novel mitochondrial contact site that is formed by Cqd1 in the inner membrane and the outer membrane complex Por1-Om14. Cqd1 is a member of the highly conserved UbiB protein kinase-like family (also called aarF domain containing kinases). It was recently shown that Cqd1 in cooperation with Cqd2 controls the cellular distribution of coenzyme Q by a yet unknown mechanism. Our data suggest that Cqd1 besides its known function in coenzyme Q homeostasis is involved in the homeostasis of phospholipids, the organization of the mitochondrial inner membrane and the interaction of mitochondria with the endoplasmic reticulum.