MICOS and MIMAS, multifunctional assemblies linking mitochondrial biogenesis, architecture, and function

Mitochondrial cristae architecture is central for optimal oxidative phosphorylation and a healthy mitochondrial physiology. The intricate architecture of the inner mitochondrial membrane relies on protein complexes that compartmentalize the membrane by imposing membrane curvature, forming membrane contact sites or membrane subdomains, regulating the partitioning of mitochondrial proteins between the different subcompartments and thereby enabling functional asymmetry, and by governing membrane dynamics. Studies in recent years have expanded our understanding of the machineries and mechanisms underlying the manifold functions of the inner membrane. This review focuses on the mitochondrial contact site and cristae organizing system (MICOS), a protein complex that stabilizes the narrow entry gates of cristae, and on a novel inner membrane megacomplex, the mitochondrial multifunctional assembly (MIMAS), as well as on their roles in organizing the inner membrane.