title: Calcium influx factor is synthesized by yeast and mammalian cells depleted of organellar calcium stores.
abstract: 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, ICRAC, 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.
authors.affiliation: Department of Cell Biology, University of Alabama, Birmingham, AL 35294-0005, USA.
authors.forename: P
authors.initials: P
authors.lastname: Csutora
authors.forename: Z
authors.initials: Z
authors.lastname: Su
authors.forename: H Y
authors.initials: HY
authors.lastname: Kim
authors.forename: A
authors.initials: A
authors.lastname: Bugrim
authors.forename: K W
authors.initials: KW
authors.lastname: Cunningham
authors.forename: R
authors.initials: R
authors.lastname: Nuccitelli
authors.forename: J E
authors.initials: JE
authors.lastname: Keizer
authors.forename: M R
authors.initials: MR
authors.lastname: Hanley
authors.forename: J E
authors.initials: JE
authors.lastname: Blalock
authors.forename: R B
authors.initials: RB
authors.lastname: Marchase
mesh_terms: D000818:Animals; D001685:Biological Factors / Q000096:biosynthesis*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002451:Cell Compartmentation; D004058:Diffusion; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015640:Ion Channel Gating; D019169:Jurkat Cells; D009865:Oocytes; D018408:Patch-Clamp Techniques; D013045:Species Specificity; D014982:Xenopus laevis; D015003:Yeasts
chemical_list: D001685:Biological Factors; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium