Potential role of Gab1 and phospholipase C-gamma in osmotic shock-induced glucose uptake in 3T3-L1 adipocytes

Osmotic shock induces GLUT4 translocation and glucose uptake through a mech anism independent of PI 3-kinase, but dependent on tyrosine phosphorylation of cellular proteins. To identify the tyrosine phosphorylated proteins req uired for osmotic shock-stimulated glucose uptake, we examined tyrosine pho sphorylation of candidate proteins, and found that the 60-80 kDa species in cluding paxillin and the 120-130 kDa species including p130Cas, PYK2, FAK a nd Gab1 were tyrosine-phosphorylated in response to osmotic shock. Inhibiti on of actin polymerization by cytochalasin D significantly decreased the ty rosine phosphorylation of paxillin, p130Cas, PYK2 and FAK but not Gab1, but had no effect on 2-deoxyglucose (DOG) uptake, suggesting a role for Gab1 i n osmotic shock-induced glucose transport. Also, we found that osmotic shoc k increases the association of phospholipase C-gamma (PLC-gamma) with Gab1 and stimulates tyrosine phosphorylation of PLC-gamma itself. The PLC inhibi tor, U73122, inhibited osmotic shock-induced 2-DOG uptake. These results su ggest that tyrosine phosphorylation of Gab1 and subsequent recruitment and activation of PLC-gamma may play a role in osmotic shock-induced glucose tr ansport.