Leukotriene D-4 triggers an association between G beta gamma subunits and phospholipase C-gamma 1 in intestinal epithelial cells

The proinflammatory mediator leukotriene D-4 (LTD4) binds to the seven tran smembrane receptor CYSLT1. Although this leukotriene plays an important bio logical role, its intracellular signaling pathways are only partly known. I n previous experiments, we found that LTD, induced tyrosine phosphorylation and translocation of phospholipase (PLC)-gamma 1 to a plasma membrane frac tion in a human epithelial cell line (Int 407). In the present study, we fu rther examined these signaling events and found that LTD, induced a rapid i nteraction between G beta gamma subunits and PLC-gamma 1; results obtained with GST fusion proteins of PLC-gamma 1 suggest that this interaction is me diated via the pleckstrin homology domain of PLC-gamma 1. Moreover, LTD4 in duced an increased association of c-Src with PLC-gamma 1, and the selective Src family tyrosine kinase inhibitor PP1 blocked both LTD4-induced tyro si ne phosphorylation of PLC-gamma 1 and the association of PLC-gamma 1 with G beta gamma subunits. The relevance of these observations in intracellular calcium signaling was investigated by microinjecting cells with anti-Gp, an ti-PLC-gamma 1, or anti-c-Src antibodies and by pretreatment with PPI, LTD4 -induced calcium mobilization was blocked by each of the indicated antibodi es (but not isotype-matched control antibodies) and by PP1, Our data sugges t that G beta gamma subunits can, directly or indirectly, serve as membrane -bound partners for PLC-gamma 1 and c-Src and that each of these proteins i s essential for LTD4-induced downstream PLC-gamma 1 signaling.