Epidermal growth factor and platelet-derived growth factor promote translocation of phospholipase C-γ from cytosol to membrane

Treatment of HER 14 cells with epidermal growth factor (EGF) or platelet-derived growth factor (PDGF) induced a translocation of phospholipase C-γ (PLC-γ) from cytosol to membrane. In such growth factor-treated cells, cytosolic PLC-γ was found to contain more phosphotyrosine than membrane-associated enzyme. Because these growth factors have been shown to promote both the physical association of PLC-γ with their receptors and the subsequent phosphorylation of the enzyme directly by the membrane-bound receptor tyrosine kinases, the membrane assocation of PLC-γ may simply be due to the formation of transient enzyme (receptor)-substrate (PLC-γ) complexes. If this is the case, membrane-associated PLC-γ would be expected to be released from membrane after undergoing tyrosine phosphorylation. However, tyrosine phosphorylation of membrane-associated PLC-γ by the EGF receptor in vitro did not result in the release of PLC-γ from membrane. Thus, the association of PLC-γ with membrane would appear to involve more than enzyme-substrate complex.