Breakdown of phosphatidylinositol 4,5-bisphosphate in a T-cell leukaemia line stimulated by phytohaemagglutinin is not dependent on Ca2+ mobilization.
Addition of phytohaemagglutinin (PHA) to the [32P]Pi-prelabelled JURKAT cells, a human T-cell leukaemia line, resulted in a decrease of [32P]phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] to about 35% of the control value. The decrease was almost complete within 30s after the PHA addition. This decrease was followed by an increase in the 32P-labelling of phosphatidic acid (maximally 2.8-fold at 2 min). The stimulation of myo-[2-3H]inositol-prelabelled JURKAT cells by PHA induced an accumulation of [2-3H]inositol trisphosphate in the presence of 5 mM-LiCl. The result indicates hydrolysis of PtdIns (4,5)P2 by a phospholipase C. The PHA stimulation of JURKAT cells induced about 6-fold increase in the cytosolic free Ca2+ concentration, [Ca2+]i, which was reported by Quin-2, a fluorescent Ca2+ indicator. Studies with partially Ca2+-depleted JURKAT cells, with the Ca2+ ionophore A23187, and with 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate indicate that the breakdown of PtdIns(4,5)P2 is not mediated through changes of [Ca2+]i. These results therefore indicate that the PHA-induced breakdown of PtdIns(4,5)P2 in JURKAT cells is not dependent on the Ca2+ mobilization.
Sasaki
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Hasegawa-Sasaki
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D000373:Agglutinins / Q000494:pharmacology*; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002855:Chromatography, Thin Layer; D006801:Humans; D007942:Leukemia, Experimental / Q000378:metabolism; D007962:Leukocytes; D010712:Phosphatidic Acids / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism*; D011506:Proteins; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
D000373:Agglutinins; D000634:Aminoquinolines; D010712:Phosphatidic Acids; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D011506:Proteins; C100155:leukoagglutinins, leukocytes; D000001:Calcimycin; D010738:Type C Phospholipases; C035739:Quin2; D002118:Calcium