Calcium influx factor is synthesized by yeast and mammalian cells depleted of organellar calcium stores.
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.
Csutora
P
P
Department of Cell Biology, University of Alabama, Birmingham, AL 35294-0005, USA.
Su
Z
Z
Kim
H Y
HY
Bugrim
A
A
Cunningham
K W
KW
Nuccitelli
R
R
Keizer
J E
JE
Hanley
M R
MR
Blalock
J E
JE
Marchase
R B
RB
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
D001685:Biological Factors; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium