When is high-Ca2+ microdomain required for mitochondrial Ca 2+ uptake?

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21 Citations (Scopus)

Abstract

Ca2+ release from IP3-sensitive stores in the endoplasmic reticulum (ER) induced by Ca2+-mobilizing agonists generates high-Ca2+ microdomains between ER vesicles and neighbouring mitochondria. Here we present a model that describes when such microdomains are required and when submicromolar [Ca2+] is sufficient for mitochondrial Ca2+ uptake. Mitochondrial Ca2+ uptake rate in angiotensin II-stimulated H295R adrenocortical cells correlates with the proximity between ER vesicles and the mitochondrion, reflecting the uptake promoting effect of high-Ca2+ peri-mitochondrial microdomains. Silencing or inhibition of p38 mitogen-activated protein kinase (MAPK) or inhibition of the novel isoforms of protein kinase C enhances mitochondrial Ca2+ uptake and abolishes the positive correlation between Ca 2+ uptake and ER-mitochondrion proximity. Inhibition of protein phosphatases attenuates mitochondrial Ca2+ uptake and also abolishes its positive correlation with ER-mitochondrion proximity. We postulate that during IP3-induced Ca2+ release, Ca2+ uptake is confined to ER-close mitochondria, because of the simultaneous activation of the protein kinases. Attenuation of Ca2+ uptake prevents Ca 2+ overload of mitochondria and thus protects the cell against apoptosis. On the other hand, all the mitochondria accumulate Ca2+ at a non-inhibited rate during physiological Ca2+ influx through the plasma membrane. Membrane potential is higher in ER-distant mitochondria, providing a bigger driving force for Ca2+ uptake. Our model explains why comparable mitochondrial Ca2+ signals are formed in response to K+ and angiotensin II (equipotent in respect to global cytosolic Ca2+ signals), although only the latter generates high-Ca 2+ microdomains.

Original languageEnglish
Pages (from-to)139-147
Number of pages9
JournalActa Physiologica
Volume195
Issue number1
DOIs
Publication statusPublished - Jan 1 2009

Keywords

  • Angiotensin II
  • Ca signalling
  • H295R cells
  • Mitochondria
  • Protein kinase C
  • p38 MAPK

ASJC Scopus subject areas

  • Physiology

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