TAILIEUCHUNG - Báo cáo Y học: Role of three isoforms of phospholipase A2 in capacitative calcium influx in human T-cells

The present study was conducted on human Jurkat T-cell lines in order to elucidate the role of phospholipase A2in capacitative calcium entry. We have employed thapsigar-gin (TG)that induces increases in [Ca 2+ ] i by emptying the calcium pool of endoplasmic reticulum, followed by capacitative calcium entry. We designed a Ca 2+ free/Ca 2+ reintroduction (CFCR)protocol for the experiments, conducted in Ca 2+ -free medium. | Eur. J. Biochem. 269 5557-5563 2002 FEBS 2002 doi Role of three isoforms of phospholipase A2 in capacitative calcium influx in human T-cells Aziz Hichami1 Beenu Joshi2 Anne Marie Simonin1 and Naim Akhtar Khan1 1UPRES Lipides Nutrition Universite de Bourgogne 21000 Dijon France 2Central Jalma Research Institute for Leprosy Agra UP India The present study was conducted on human Jurkat T-cell lines in order to elucidate the role of phospholipase A2 in capacitative calcium entry. We have employed thapsigar-gin TG that iducees iccreases m C a2 i by emptying the calcium pool of endoplasmic reticulum followed by capacitative calcium entry. We designed a Ca2 free Ca2 reintroduction CFCR protocol for the experiments conducted in Ca2 -free medium. By employing CFCR protocol we observed that addition of exogenous arachidonic acid AA stimulated TG-induced capacitative calcium influx. The liberation of endogenous AA and its autocrine action seems to be implicated during TG- induced capacitative calcium influx TG potentiates the induction of constitutively expressed mRNA of four PLA2 isoforms type 1B IV V VI the inhibitors of the three PLA2 isotypes type 1B V VI nhiibit TG-índuced eeteate of 3H AA into the extracellular medium and finally these PLA2 inhibitors do curtail TG-stimulated capacita-tive calcium entry in these cells. These results suggest that stimulation of three isoforms of PLA2 by thapsigargin liberates free AA that in turn induces capacitative calcium influx in human T-cells. Keywords Jurkat cells thapsigargin arachidonic acid. In T-lymphocytes a biphasic rise in concentrations of free calcium Ca2 i is elicited by the binding of antigen or polyclonal mitogens to the T-cell receptor 1 2 . Hence the rise in Ca2 i constitutes an essential triggering signal for T-cell differentiation and proliferation 3 . Raising Ca2 i has been found to increase the activity of a transcription factor the nuclear factor of activated T-cells NF-AT which

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