A role for phospholipase D in GLUT4 glucose transporter translocation

Based on recent studies showing that phospholipase D (PLD)1 is associated w ith intracellular membranes and promotes membrane budding from the trans-Go lgi, we tested its possible role in the membrane trafficking of GLUT4 gluco se transporters. Using immunofluorescence confocal microscopy, expressed My c epitope-tagged PLD1 was found to associate with intracellular vesicular s tructures by a mechanism that requires its N-terminal pleckstrin homology d omain, partial co-localization with expressed GLUT4 fused to green fluoresc ent protein in both 3T3-L1 adipocytes and Chinese hamster ovary cells was e vident. Furthermore, microinjection of purified FED into cultured adipocyte s markedly potentiated the effect of a submaximal concentration of insulin to stimulate GLUT4 translocation to cell surface membranes. Insulin stimula ted PLD activity in cells expressing high levels of insulin receptors but n o such insulin effect was detected in 3T3-L1 adipocytes, Taken together, th ese results are consistent with the hypothesis that PLD1 associated with GL UT4-containing membranes acts in a constitutive manner to promote the mecha nism of GLUT4 translocation by insulin.