Microscopic properties of elementary Ca2+ release sites in non-excitable cells

Curr Biol. 2000 Jan 13;10(1):8-15. doi: 10.1016/s0960-9822(99)00258-4.

Abstract

Background: Elementary Ca2+ signals, such as 'Ca2+ puffs', that arise from the activation of clusters of inositol 1 ,4,5,-trisphosphate (InsP3) receptors are the building blocks for local and global Ca2+ signalling. We previously found that one, or a few, Ca2+ puff sites within agonist-stimulated cells act as 'pacemakers' to initiate global Ca2+ waves. The factors that distinguish these pacemaker Ca2+ puff sites from the other Ca2+ release sites that simply participate in Ca2+ wave propagation are unknown.

Results: The spatiotemporal properties of Ca2+ puffs were investigated using confocal microscopy of fluo3-loaded HeLa cells. The same pacemaker Ca2+ puff sites were activated during stimulation of cells with different agonists. The majority of agonist-stimulated pacemaker Ca2+ puffs originated in a perinuclear location. The positions of such Ca2+ puff sites were stable for up to 2 hours, and were not affected by disruption of the actin cytoskeleton. A similar perinuclear distribution of Ca2+ puff sites was also observed when InsP3 receptors were directly stimulated with thimerosal or membrane-permeant InsP3 esters. Immunostaining indicated that the perinuclear position of pacemaker Ca2+ puffs was not due to the localised expression of InsP3 receptors.

Conclusions: The pacemaker Ca2+ puff sites that initiate Ca2+ responses are temporally and spatially stable within cells. These Ca2+ release sites are distinguished from their neighbours by an intrinsically higher InsP3 sensitivity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / pharmacology
  • Adenosine Triphosphate / pharmacology
  • Aluminum Compounds / pharmacology
  • Calcium Channels / analysis
  • Calcium Channels / physiology*
  • Calcium Signaling / physiology*
  • Cytochalasin D / pharmacology
  • Cytoskeleton / drug effects
  • Cytoskeleton / ultrastructure
  • Fluorides / pharmacology
  • HeLa Cells / drug effects
  • HeLa Cells / metabolism
  • HeLa Cells / ultrastructure*
  • Histamine / pharmacology
  • Humans
  • Inositol 1,4,5-Trisphosphate / analogs & derivatives
  • Inositol 1,4,5-Trisphosphate / pharmacology
  • Inositol 1,4,5-Trisphosphate Receptors
  • Periodicity
  • Receptors, Cytoplasmic and Nuclear / analysis
  • Receptors, Cytoplasmic and Nuclear / physiology*
  • Subcellular Fractions / drug effects
  • Subcellular Fractions / metabolism
  • Thimerosal / pharmacology

Substances

  • Aluminum Compounds
  • Calcium Channels
  • ITPR1 protein, human
  • Inositol 1,4,5-Trisphosphate Receptors
  • Receptors, Cytoplasmic and Nuclear
  • Cytochalasin D
  • Thimerosal
  • Histamine
  • Inositol 1,4,5-Trisphosphate
  • Adenosine Triphosphate
  • Acetylcholine
  • Fluorides
  • aluminum fluoride