The small guanosine triphosphate-binding protein Rab4 is involved in insulin-induced GLUT4 translocation and actin filament rearrangement in 3T3-L1 cells

Endocrinology. 1997 Nov;138(11):4941-9. doi: 10.1210/endo.138.11.5493.


Insulin's stimulation of glucose transport involves the translocation of vesicles containing the glucose transporter GLUT4 to the plasma membrane. Small GTP-binding proteins have been implicated in the regulation of vesicular traffic. We studied the effects of microinjection of wild-type Rab4 glutathione S-transferase fusion protein (WT Rab4), a GTP-binding defective mutant (Rab4 N121I), a guanosine triphosphatase-defective mutant (Rab4 Q67L), and a Rab4 antibody on insulin-induced GLUT4 translocation in 3T3-L1 adipocytes. Microinjection of Rab4 N121I and Rab4 antibodies had no effect on basal GLUT4 staining, but inhibited insulin-induced GLUT4 translocation by 50% compared with that in control IgG-injected cells. WT Rab4 and Rab4 Q67L microinjection had no effect on either basal or insulin-induced GLUT4 translocation. Premixing and coinjection of the Rab4 antibody with WT Rab4 almost completely abolished its inhibitory effect on insulin-induced GLUT4 translocation. In contrast, microinjection of an antibody directed against the highly conserved region of Rab3 proteins had no effect on insulin-induced GLUT4. These results point to a direct role of Rab4 in insulin-induced GLUT4 translocation, and that this effect is dependent on nucleotide binding to the protein. We also studied the effect of microinjection of the same proteins on insulin-induced actin filament rearrangement (membrane ruffling) in the same cell line. Microinjection of Rab4 N121I and Rab4 antibodies inhibited insulin-induced membrane ruffling by 40%, whereas WT Rab4 or a Rab3 antibody injection had no effect on cytoskeletal rearrangement. In summary, 1) Rab4 is a necessary component of the insulin/GLUT4 translocation signaling pathway; 2) the function of Rab4 in this pathway requires GTP binding; 3) Rab4 also participates in the process of insulin-induced membrane ruffling; and 4) Rab3 proteins do not seem to be involved in these processes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Actins / physiology*
  • Adipocytes / metabolism
  • Adipocytes / physiology*
  • Animals
  • Antibodies / immunology
  • Antibodies / pharmacology
  • Biological Transport / drug effects
  • Biological Transport / physiology
  • Blotting, Western
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / pharmacology
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / immunology
  • GTP-Binding Proteins / physiology*
  • Glucose Transporter Type 4
  • Glutathione Transferase / pharmacology
  • Insulin / pharmacology*
  • Mice
  • Microinjections
  • Monosaccharide Transport Proteins / metabolism*
  • Muscle Proteins*
  • Mutation
  • rab3 GTP-Binding Proteins
  • rab4 GTP-Binding Proteins


  • Actins
  • Antibodies
  • Glucose Transporter Type 4
  • Insulin
  • Monosaccharide Transport Proteins
  • Muscle Proteins
  • Slc2a4 protein, mouse
  • Glutathione Transferase
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • rab3 GTP-Binding Proteins
  • rab4 GTP-Binding Proteins