Functional importance of the dihydropyridine-sensitive, yet voltage-insensitive store-operated Ca2+ influx of U937 cells

FEBS Lett. 1996 Sep 30;394(2):159-64. doi: 10.1016/0014-5793(96)00939-8.

Abstract

The Ca2+ current activated by Ca2+ store depletion in non-excitable cells is classically regarded as being dihydropyridine-insensitive, suggesting that store-operated Ca2+ channels (SOCs) are dissimilar to voltage-gated Ca2+ channels (VGCs) of excitable-cells. Here, we demonstrate dihydropyridine-sensitivity for the store-operated Ca2+ influx induced by ATP and thapsigargin (Tg) in the non-excitable U937 cell-line. Ca2+ store depletion by prior treatment of cells with either Tg or ATP, stimulated a Ca2+ entry mechanism that was inhibited by nicardipine, nifedipine, and the specific L-type Ca2+ channel blocker, calciseptine. A functional requirement for this Ca2+ influx mechanism in agonist-induced mitogenesis seemed likely, since nicardipine, a particularly potent inhibitor of store-operated Ca2+ influx in these cells, suppressed ATP- and Tg-stimulated cell proliferation. Depolarisation of cells with KCl, or gramicidin failed to elicit an increase in cytosolic Ca2+, suggesting that while the store-operated Ca2+ influx channel of U937 cells shares pharmacologic properties with the L-type Ca2+ channel, it is voltage-insensitive and therefore may resemble an L-type Ca2+ channel lacking a voltage sensor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Bridged-Ring Compounds / pharmacology
  • Calcium / analysis
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / drug effects
  • Calcium Channels / metabolism*
  • Calcium Channels, L-Type
  • Cell Division / drug effects
  • Cell Line
  • Dihydropyridines / pharmacology*
  • Egtazic Acid / pharmacology
  • Elapid Venoms / pharmacology
  • Humans
  • Manganese / pharmacology
  • Monocytes / metabolism*
  • Nicardipine / pharmacology
  • Norbornanes
  • Thapsigargin / pharmacology
  • Thiocarbamates
  • Thiones / pharmacology

Substances

  • Bridged-Ring Compounds
  • Calcium Channel Blockers
  • Calcium Channels
  • Calcium Channels, L-Type
  • Dihydropyridines
  • Elapid Venoms
  • Norbornanes
  • Thiocarbamates
  • Thiones
  • calciseptine
  • Manganese
  • Egtazic Acid
  • tricyclodecane-9-yl-xanthogenate
  • Thapsigargin
  • Adenosine Triphosphate
  • Nicardipine
  • Calcium