Regulation of receptor-mediated calcium influx across the plasma membrane in a human leukemic T-cell line: evidence of its dependence on an initial calcium mobilization from intracellular stores.
It has been repeatedly shown that stimulation of a human leukemic T-cell line, JURKAT, by lectins such as phytohaemagglutinin and anti-T3 antibody (OKT3) leads to an elevation in the concentration of cytosolic free Ca2. This Ca2+ transient results from both an intracellular mobilization and an influx of Ca2+ through specific membrane channels. The objective of this study was to investigate the mechanism by which receptor-mediated influx of Ca2+ is regulated in JURKAT cells, which demonstrably lack 'voltage-dependent calcium channels'. It was found that upon increased loading with quin2 or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate (BAPTA) there was a pronounced decline of both phytohaemagglutinin-stimulated and OKT3-stimulated influx of 45Ca2+. Using 15 microM quin2/AM or 30 microM BAPTA/AM, agonist-stimulated 45Ca2+ influx was almost totally abolished. At these concentrations of both quin2/AM or BAPTA/AM, phytohaemagglutinin and OKT3 could still induce a rise of cytosolic free Ca2+ above 200 nM. In the presence of La3+ (200 microM), which completely inhibited the agonist-induced 45Ca2+ influx, both phytohaemagglutinin and OKT3 were able to raise the concentrations of cytosolic free Ca2+ to well above 200 nM by merely mobilizing Ca2+ from intracellular stores alone. The data suggest that an agonist-induced increase in the concentration of cytosolic free Ca2+, due to mobilization from intracellular stores, could either directly or indirectly, initiate receptor-mediated Ca2+ influx across the plasma membrane in JURKAT cells.
Ng
J
J
Department of Immunology, Karolinska Institute, Stockholm, Sweden.
Fredholm
B B
BB
Jondal
M
M
Andersson
T
T
D000634:Aminoquinolines / Q000494:pharmacology; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000276:immunology; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D007202:Indicators and Reagents; D007811:Lanthanum / Q000494:pharmacology; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000502:physiology*; D014407:Tumor Cells, Cultured
D000634:Aminoquinolines; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D015220:Calcium Channels; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D010835:Phytohemagglutinins; D011956:Receptors, Cell Surface; D004533:Egtazic Acid; D007811:Lanthanum; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; C035739:Quin2; D002118:Calcium