Novel function of phosphoinositide 3-kinase in T cell Ca2+ signaling. A phosphatidylinositol 3,4,5-trisphosphate-mediated Ca2+ entry mechanism.
This study presents evidence that phosphoinositide (PI) 3-kinase is involved in T cell Ca(2+) signaling via a phosphatidylinositol 3,4, 5-trisphosphate PI(3,4,5)P(3)-sensitive Ca(2+) entry pathway. First, exogenous PI(3,4,5)P(3) at concentrations close to its physiological levels induces Ca(2+) influx in T cells, whereas PI(3,4)P(2), PI(4, 5)P(2), and PI(3)P have no effect on [Ca(2+)](i). This Ca(2+) entry mechanism is cell type-specific as B cells and a number of cell lines examined do not respond to PI(3,4,5)P(3) stimulation. Second, inhibition of PI 3-kinase by wortmannin and by overexpression of the dominant negative inhibitor Deltap85 suppresses anti-CD3-induced Ca(2+) response, which could be reversed by subsequent exposure to PI(3,4,5)P(3). Third, PI(3,4,5)P(3) is capable of stimulating Ca(2+) efflux from Ca(2+)-loaded plasma membrane vesicles prepared from Jurkat T cells, suggesting that PI(3,4,5)P(3) interacts with a Ca(2+) entry system directly or via a membrane-bound protein. Fourth, although D-myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4, 5)P(4)) mimics PI(3,4,5)P(3) in many aspects of biochemical functions such as membrane binding and Ca(2+) transport, we raise evidence that Ins(1,3,4,5)P(4) does not play a role in anti-CD3- or PI(3,4,5)P(3)-mediated Ca(2+) entry. This PI(3,4,5)P(3)-stimulated Ca(2+) influx connotes physiological significance, considering the pivotal role of PI 3-kinase in the regulation of T cell function. Given that PI 3-kinase and phospholipase C-gamma form multifunctional complexes downstream of many receptor signaling pathways, we hypothesize that PI(3,4,5)P(3)-induced Ca(2+) entry acts concertedly with Ins(1,4,5)P(3)-induced Ca(2+) release in initiating T cell Ca(2+) signaling. By using a biotinylated analog of PI(3,4,5)P(3) as the affinity probe, we have detected several putative PI(3,4,5)P(3)-binding proteins in T cell plasma membranes.
Hsu
A L
AL
Division of Pharmaceutical Sciences, College of Pharmacy and Department of Microbiology and Immunology, Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky 40536, USA.
Ching
T T
TT
Sen
G
G
Wang
D S
DS
Bondada
S
S
Authi
K S
KS
Chen
C S
CS
D000730:Androstadienes / Q000494:pharmacology; D017252:CD3 Complex / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016257:Fura-2; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates / Q000494:pharmacology; D019169:Jurkat Cells; D008081:Liposomes / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D013601:T-Lymphocytes / Q000201:enzymology*; D000077191:Wortmannin
D000730:Androstadienes; D017252:CD3 Complex; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; C506926:ITPR1 protein, human; D007093:Imidazoles; D007211:Indoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates; D008081:Liposomes; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D018160:Receptors, Cytoplasmic and Nuclear; C118500:inositol 3,4,5-trisphosphate; C118303:phosphoinositide-3,4,5-triphosphate; C118301:phosphoinositide-3,4-bisphosphate; C081655:inositol-1,3,4,5-tetrakisphosphate; D019869:Phosphatidylinositol 3-Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C048960:indo-1; D002118:Calcium; D016257:Fura-2; D000077191:Wortmannin