The Mitochondrial Ca2+ Uniporter MCU Is Essential for Glucose-Induced ATP Increases in Pancreatic β-cells

PLoS One. 2012;7(7):e39722. doi: 10.1371/journal.pone.0039722. Epub 2012 Jul 19.

Abstract

Glucose induces insulin release from pancreatic β-cells by stimulating ATP synthesis, membrane depolarisation and Ca(2+) influx. As well as activating ATP-consuming processes, cytosolic Ca(2+) increases may also potentiate mitochondrial ATP synthesis. Until recently, the ability to study the role of mitochondrial Ca(2+) transport in glucose-stimulated insulin secretion has been hindered by the absence of suitable approaches either to suppress Ca(2+) uptake into these organelles, or to examine the impact on β-cell excitability. Here, we have combined patch-clamp electrophysiology with simultaneous real-time imaging of compartmentalised changes in Ca(2+) and ATP/ADP ratio in single primary mouse β-cells, using recombinant targeted (Pericam or Perceval, respectively) as well as entrapped intracellular (Fura-Red), probes. Through shRNA-mediated silencing we show that the recently-identified mitochondrial Ca(2+) uniporter, MCU, is required for depolarisation-induced mitochondrial Ca(2+) increases, and for a sustained increase in cytosolic ATP/ADP ratio. By contrast, silencing of the mitochondrial Na(+)-Ca(2+) exchanger NCLX affected the kinetics of glucose-induced changes in, but not steady state values of, cytosolic ATP/ADP. Exposure to gluco-lipotoxic conditions delayed both mitochondrial Ca(2+) uptake and cytosolic ATP/ADP ratio increases without affecting the expression of either gene. Mitochondrial Ca(2+) accumulation, mediated by MCU and modulated by NCLX, is thus required for normal glucose sensing by pancreatic β-cells, and becomes defective in conditions mimicking the diabetic milieu.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Animals
  • Calcium / metabolism
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Cells, Cultured
  • Female
  • Gene Silencing
  • Glucose / pharmacology*
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / metabolism*
  • Mice

Substances

  • Calcium Channels
  • mitochondrial calcium uniporter
  • Adenosine Triphosphate
  • Glucose
  • Calcium