title: Up-regulation of Phosphatidylinositol-3 Kinase Signaling in plcg1 Gene Null Fibroblasts.
abstract: Phospholipase C-gamma1(PLC-gamma1) and phosphatidylinositol-3 kinase(PI-3K) play crucial role in growth factor-induced cell growth and proliferation. To investigate the complementary mechanism of PLC-gamma1 in cell growth and epidermal growth factor (EGF)-induced mitogenic signaling, PLC-gamma1 deficient mouse embryonic fibroblasts(PLC-gamma1(-/-)) and its wild type(PLC-gamma1(+/+)) were exposed to U73122, a phospholipase C-specific inhibitor, or wortmannin, a PI-3K inhibitor then the clonogenicity, viability, EGF-induced DNA synthesis of the two cell lines were determined by cloning formation, MTT method and (3)H -thymidine incorporation assay. Results showed that either U73122 or wortmannin inhibited PLC-gamma1(-/-) and PLC-gamma1(+/+) cells in terms of EGF-induced DNA synthesis, cloning formation and cell viability, but PLC-gamma1(-/-) cells were more dependent on PI-3K and less dependent on PLC compared with wild types. The PLC-gamma1 signaling pathway of PLC-gamma1(-/-) cells might be complemented by PI-3K pathway, because after EGF stimulation, the tyrosine phospholation of p85alpha PI-3K increased significantly in PLC-gamma1(-/-), but not in PLC-gamma2(-/-), as Western blotting showed that there was neither complementary PLC-gamma2 expression in PLC-gamma1(-/-) cells, nor other PLC isozymes such as PLC-beta and PLC-delta. These results suggest the redundancy of EGF-mediated signaling and the complementary mechanism of PLC-gamma1 pathway.
authors.affiliation: Department of Cell Biology and Medical Genetics, the First Military Medical University, Guangzhou 510515, China. baixc15@263.net
authors.forename: X C
authors.initials: XC
authors.lastname: Bai
authors.forename: S Q
authors.initials: SQ
authors.lastname: Luo
authors.forename: J
authors.initials: J
authors.lastname: Bai
authors.forename: F
authors.initials: F
authors.lastname: Deng
authors.forename: W S
authors.initials: WS
authors.lastname: Zheng
authors.forename: Q S
authors.initials: QS
authors.lastname: Ji