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 A2 in capacitative calcium entry. We have employed thapsigargin (TG) that induces increases in [Ca2+]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) inhibit TG-induced release of [3H]AA into the extracellular medium, and finally, these PLA2 inhibitors do curtail TG-stimulated capacitative 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.
Hichami
Aziz
A
UPRES Lipides & Nutrition, Université de Bourgogne 21000 Dijon, France; Central Jalma Research Institute for Leprosy, Agra, UP, India.
Joshi
Beenu
B
Simonin
Anne Marie
AM
Khan
Naim Akhtar
NA
D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D004594:Electrophysiology; D006801:Humans; D019169:Jurkat Cells; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D054467:Phospholipases A2; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
D020033:Protein Isoforms; D012333:RNA, Messenger; D016718:Arachidonic Acid; D019284:Thapsigargin; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium