Up-regulation of
Phosphatidylinositol-3 Kinase Signaling in plcg1 Gene Null
Fibroblasts
BAI Xiao-Chun*, LUO Shen-Qiu, BAI Jie, DENG Fan,
ZHENG Wei-Shen, JI Qun-Shen1
( Department of Cell Biology and Medical Genetics, the First Military
Medical University, Guangzhou 510515, China；1Department of Biochemistry
Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA )
Abstract
Phospholipase C-γ1(PLC-γ1) and phosphatidylinositol-3 kinase(PI-3K) play
crucial role in growth factor-induced cell growth and proliferation. To
investigate the complementary mechanism of PLC-γ1 in cell growth and epidermal
growth factor (EGF)-induced mitogenic signaling, PLC-γ1 deficient mouse
embryonic fibroblasts(PLC-γ1-/-) and its wild type(PLC-γ1+/+)
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 ［3H］-thymidine incorporation
assay. Results showed that either U73122 or wortmannin inhibited PLC-γ1-/-
and PLC-γ1+/+ cells in terms of EGF-induced DNA synthesis, cloning
for mation and cell viability, but PLC-γ1-/- cells were more
dependent on PI-3K and less dependent on PLC compared with wild types. The
PLC-γ1 signaling pathway of PLC-γ1-/- cells might be complemented by
PI-3K pathway, because after EGF stimulation, the tyrosine phospholation of
p85α PI-3K increased significantly in PLC-γ1-/-, but not in PLC-γ2-/-,
as Western blotting showed that there was neither complementary PLC-γ2
expression in PLC-γ1-/- cells, nor other PLC isozymes such as PLC-β
and PLC-δ. These results suggest the redundancy of EGF-mediated signaling and
the complementary mechanism of PLC-γ1 pathway.
Key words phospholipase C-γ1； phosphatidylinositol-3 kinase； epidermal growth factor；plcg1 gene null mouse fibroblast； signal transduction
*Corresponding author： Tel, 86-20-87148207； e-mail, [email protected]