Calcium-sensing receptor activation induces intracellular calcium oscillations

Am J Physiol Cell Physiol. 2001 Jun;280(6):C1412-21. doi: 10.1152/ajpcell.2001.280.6.C1412.

Abstract

Parathyroid hormone secretion is exquisitely sensitive to small changes in serum Ca2+ concentration, and these responses are transduced via the Ca2+-sensing receptor (CaR). We utilized heterologous expression in HEK-293 cells to determine the effects of small, physiologically relevant perturbations in extracellular Ca2+ on CaR signaling via phosphatidylinositol-phospholipase C, using changes in fura 2 fluorescence to quantify intracellular Ca2+. Chronic exposure of CaR-transfected cells to Ca2+ in the range from 0.5 to 3 mM modulated the resting intracellular Ca2+ concentration and the subsequent cellular responses to acute extracellular Ca2+ perturbations but had no effect on thapsigargin-sensitive Ca2+ stores. Modest, physiologically relevant increases in extracellular Ca2+ concentration (0.5 mM increments) caused sustained (30-40 min) low-frequency oscillations of intracellular Ca2+ (approximately 45 s peak to peak interval). Oscillations were eliminated by 1 microM thapsigargin but were insensitive to protein kinase inhibitors (staurosporine, KN-93, or bisindolylmaleimide I). Staurosporine did increase the fraction of cells oscillating at a given extracellular Ca2+ concentration. Serum Ca2+ concentrations thus chronically regulate cells expressing CaR, and small perturbations in extracellular Ca2+ alter both resting intracellular Ca2+ as well as Ca2+ dynamics.

Publication types

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

MeSH terms

  • Calcium / metabolism*
  • Calcium Signaling / physiology*
  • Cell Line
  • Enzyme Inhibitors / pharmacology
  • Fluorescent Dyes
  • Fura-2
  • Gene Expression / physiology
  • Humans
  • Kidney / cytology
  • Protein Kinase Inhibitors
  • Protein Kinases / metabolism
  • Receptors, Calcium-Sensing
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • Thapsigargin / pharmacology
  • Transfection

Substances

  • Enzyme Inhibitors
  • Fluorescent Dyes
  • Protein Kinase Inhibitors
  • Receptors, Calcium-Sensing
  • Receptors, Cell Surface
  • Thapsigargin
  • Protein Kinases
  • Calcium
  • Fura-2