Potential Role of Gab1 and Phospholipase C-γ in Osmotic Shock-Induced Glucose Uptake in 3T3-L1 Adipocytes

Osmotic shock induces GLUT4 translocation and glucose uptake through a mechanism independent of PI 3-kinase, but dependent on tyrosine phosphorylation of cellular proteins. To identify the tyrosine phosphorylated proteins required for osmotic shock-stimulated glucose uptake, we examined tyrosine phosphorylation of candidate proteins, and found that the 60 - 80 kDa species including paxillin and the 120 - 130 kDa species including p130Cas, PYK2, FAK and Gab1 were tyrosine-phosphorylated in response to osmotic shock. Inhibition of actin polymerization by cytochalasin D significantly decreased the tyrosine phosphorylation of paxillin, p130Cas, PYK2 and FAK but not Gab1, but had no effect on 2-deoxyglucose (DOG) uptake, suggesting a role for Gab1 in osmotic shock-induced glucose transport. Also, we found that osmotic shock increases the association of phospholipase C-γ (PLC-γ) with Gab1 and stimulates tyrosine phosphorylation of PLC-γ itself. The PLC inhibitor, U73122, inhibited osmotic shock-induced 2-DOG uptake. These results suggest that tyrosine phosphorylation of Gab1 and subsequent recruitment and activation of PLC-γ may play a role in osmotic shock-induced glucose transport.

Osmotic Shock - Glucose Uptake - Adipocytes - Gab1 - Phospholipase C-γ

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