MCUR1 Is a Scaffold Factor for the MCU Complex Function and Promotes Mitochondrial Bioenergetics

Highlights

• MCUR1 binds to MCU and EMRE and functions as a scaffold factor

• The coiled-coil domains of both MCU and MCUR1 are essential for MCU complex assembly

• Genetic deletion of MCUR1 severely impairs [Ca²⁺]_m uptake and I_MCU current

• MCUR1 deletion impairs bioenergetics and cell migration and elicits autophagy

Summary

Mitochondrial Ca²⁺ Uniporter (MCU)-dependent mitochondrial Ca²⁺ uptake is the primary mechanism for increasing matrix Ca²⁺ in most cell types. However, a limited understanding of the MCU complex assembly impedes the comprehension of the precise mechanisms underlying MCU activity. Here, we report that mouse cardiomyocytes and endothelial cells lacking MCU regulator 1 (MCUR1) have severely impaired [Ca²⁺]_m uptake and I_MCU current. MCUR1 binds to MCU and EMRE and function as a scaffold factor. Our protein binding analyses identified the minimal, highly conserved regions of coiled-coil domain of both MCU and MCUR1 that are necessary for heterooligomeric complex formation. Loss of MCUR1 perturbed MCU heterooligomeric complex and functions as a scaffold factor for the assembly of MCU complex. Vascular endothelial deletion of MCU and MCUR1 impaired mitochondrial bioenergetics, cell proliferation, and migration but elicited autophagy. These studies establish the existence of a MCU complex that assembles at the mitochondrial integral membrane and regulates Ca²⁺-dependent mitochondrial metabolism.