Epidermal growth factor-induced activation and translocation of phospholipase C-gamma 1 to the cytoskeleton in rat hepatocytes.
In this study, we have examined the relationship between epidermal growth factor (EGF)-induced tyrosine phosphorylation of phospholipase C-gamma 1 (PLC-gamma 1) and its translocation from the cytosol to the Triton X-100-insoluble cytoskeleton fraction in rat hepatocytes. The translocation of PLC-gamma 1 was specific for EGF stimulation, because a similar effect was not observed with insulin or vasopressin. EGF caused a transient increase of PLC activity in the cytoskeleton fraction which could be abolished by immunoprecipitating PLC-gamma 1. Tyrosine phosphorylated PLC-gamma 1 was seen only in the cytoskeleton fraction, suggesting that tyrosine phosphorylation is required for PLC-gamma 1 translocation to the cytoskeleton. This process may involve binding of PLC-gamma 1 to actin filaments, since actin was immunoprecipitated together with PLC-gamma 1 in the cytoskeleton after EGF treatment. EGF-induced translocation of PLC-gamma 1 to the cytoskeleton was not inhibited by pertussis toxin, but Gi alpha was translocated in an EGF-dependent manner, suggesting that the interaction of PLC-gamma 1 with its activated Gi-protein is downstream from both PLC-gamma 1 tyrosine phosphorylation and its translocation to the cytoskeleton. Taken together, the present studies indicate that EGF-induced tyrosine phosphorylation of PLC-gamma 1, its association with the cytoskeleton, and its interaction with activated Gi alpha protein are all obligatory for PLC-gamma 1 activation in hepatocytes.
Yang
L J
LJ
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104.
Rhee
S G
SG
Williamson
J R
JR
D000199:Actins / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D000199:Actins; D007527:Isoenzymes; D014443:Tyrosine; D004815:Epidermal Growth Factor; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins