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Journal of Cell Science

Year: 2009  |  Volume: 122  |  Issue: 13  |  Page No.: 2283 - 2291

The F-BAR protein CIP4 promotes GLUT4 endocytosis through bidirectional interactions with N-WASp and Dynamin-2

S. M Hartig, S Ishikura, R. S Hicklen, Y Feng, E. G Blanchard, K. A Voelker, C. S Pichot, R. W Grange, R. M Raphael, A Klip and S. J. Corey

Abstract

F-BAR proteins are a newly described family of proteins with unknown physiological significance. Because F-BAR proteins, including Cdc42 interacting protein-4 (CIP4), drive membrane deformation and affect endocytosis, we investigated the role of CIP4 in GLUT4 traffic by flow cytometry in GLUT4myc-expressing L6 myoblasts (L6 GLUT4myc). L6 GLUT4myc cells express CIP4a as the predominant F-BAR protein. siRNA knockdown of CIP4 increased insulin-stimulated 14C-deoxyglucose uptake by elevating cell-surface GLUT4. Enhanced surface GLUT4 was due to decreased endocytosis, which correlated with lower transferrin internalization. Immunoprecipitation of endogenous CIP4 revealed that CIP4 interacted with N-WASp and Dynamin-2 in an insulin-dependent manner. FRET confirmed the insulin-dependent, subcellular properties of these interactions. Insulin exposure stimulated specific interactions in plasma membrane and cytosolic compartments, followed by a steady-state response that underlies the coordination of proteins needed for GLUT4 traffic. Our findings reveal a physiological function for F-BAR proteins, supporting a previously unrecognized role for the F-BAR...

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