Structure and function of the N-terminal domain of the human mitochondrial calcium uniporter

EMBO Rep. 2015 Oct;16(10):1318-33. doi: 10.15252/embr.201540436. Epub 2015 Sep 3.

Abstract

The mitochondrial calcium uniporter (MCU) is responsible for mitochondrial calcium uptake and homeostasis. It is also a target for the regulation of cellular anti-/pro-apoptosis and necrosis by several oncogenes and tumour suppressors. Herein, we report the crystal structure of the MCU N-terminal domain (NTD) at a resolution of 1.50 Å in a novel fold and the S92A MCU mutant at 2.75 Å resolution; the residue S92 is a predicted CaMKII phosphorylation site. The assembly of the mitochondrial calcium uniporter complex (uniplex) and the interaction with the MCU regulators such as the mitochondrial calcium uptake-1 and mitochondrial calcium uptake-2 proteins (MICU1 and MICU2) are not affected by the deletion of MCU NTD. However, the expression of the S92A mutant or a NTD deletion mutant failed to restore mitochondrial Ca(2+) uptake in a stable MCU knockdown HeLa cell line and exerted dominant-negative effects in the wild-type MCU-expressing cell line. These results suggest that the NTD of MCU is essential for the modulation of MCU function, although it does not affect the uniplex formation.

Keywords: MCU; MCU domain‐like fold; crystal structure; mitochondrial calcium uptake; uniplex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism
  • Calcium Channels / chemistry*
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Calcium-Binding Proteins / metabolism
  • Crystallography, X-Ray
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Mitochondria / metabolism
  • Mitochondrial Membrane Transport Proteins / genetics
  • Mitochondrial Membrane Transport Proteins / metabolism*
  • Models, Molecular
  • Mutation
  • Protein Folding
  • Protein Interaction Domains and Motifs
  • Protein Structure, Secondary
  • Protein Structure, Tertiary

Substances

  • Calcium Channels
  • Calcium-Binding Proteins
  • Mitochondrial Membrane Transport Proteins
  • mitochondrial calcium uniporter
  • Calcium