Calcium influx factor is synthesized by yeast and mammalian cells depleted of organellar calcium stores

Academic Article


  • Depletion of endoplasmic reticulum Ca2+ stores leads to the entry of extracellular Ca2+ into the cytoplasm, a process termed capacitative or store-operated Ca2+ entry. Partially purified extracts were prepared from the human Jurkat T lymphocyte cell line and yeast in which Ca2+ stores were depleted by chemical and genetic means, respectively. After microinjection into Xenopus laevis oocytes, the extracts elicited a wave of increased cytoplasmic free Ca2+ ([Ca2+](i)) that spread from the point of injection across the oocyte. Extracts from cells with replete organellar Ca2+ stores were inactive. The increases depended on extracellular Ca2+, were unaffected by the inositol 1,4,5-trisphosphate (IP3) inhibitor heparin or an anti-IP3 receptor antibody and were unchanged when the endoplasmic reticulum was segregated to the hemisphere opposite the injection site by centrifugation. Confocal microscopy revealed that [Ca2+](i) increases were most pronounced at the periphery of the oocyte. The patterns of [Ca2+](i) increases were replicated by computer simulations based on a diffusible messenger of about 700 Da that directly activates Ca2+ influx. In addition, I(CRAC), a Ca2+ release-activated Ca2+ current monitored in Jurkat cells by whole-cell patch clamp recordings, was more rapidly activated when active extracts were included in the patch pipette than by the inclusion of a Ca2+ chelator or IP3. These data support the existence in yeast and mammalian cells depleted of Ca2+ stores of a functionally conserved diffusible calcium influx factor that directly activates Ca2+ influx.
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    Author List

  • Csutora P; Su Z; Kim HY; Bugrim A; Cunningham KW; Nuccitelli R; Keizer JE; Hanley MR; Blalock JE; Marchase RB
  • Start Page

  • 121
  • End Page

  • 126
  • Volume

  • 96
  • Issue

  • 1