title: Alpha-actinin-4 is selectively required for insulin-induced GLUT4 translocation.
abstract: Insulin induces GLUT4 translocation to the muscle cell surface. Using differential amino acid labeling and mass spectrometry, we observed insulin-dependent co-precipitation of actinin-4 (ACTN4) with GLUT4 (Foster, L. J., Rudich, A., Talior, I., Patel, N., Huang, X., Furtado, L. M., Bilan, P. J., Mann, M., and Klip, A. (2006) J. Proteome Res. 5, 64-75). ACTN4 links F-actin to membrane proteins, and actin dynamics are essential for GLUT4 translocation. We hypothesized that ACTN4 may contribute to insulin-regulated GLUT4 traffic. In L6 muscle cells insulin, but not platelet-derived growth factor, increased co-precipitation of ACTN4 with GLUT4. Small interfering RNA-mediated ACTN4 knockdown abolished the gain in surface-exposed GLUT4 elicited by insulin but not by platelet-derived growth factor, membrane depolarization, or mitochondrial uncoupling. In contrast, knockdown of alpha-actinin-1 (ACTN1) did not prevent GLUT4 translocation by insulin. GLUT4 colocalized with ACTN4 along the insulin-induced cortical actin mesh and ACTN4 knockdown prevented GLUT4-actin colocalization without impeding actin remodeling or Akt phosphorylation, maintaining GLUT4 in a tight perinuclear location. We propose that ACTN4 contributes to GLUT4 traffic, likely by tethering GLUT4 vesicles to the cortical actin cytoskeleton.
authors.affiliation: Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8.
authors.forename: Ilana
authors.initials: I
authors.lastname: Talior-Volodarsky
authors.affiliation: Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Varinder K
authors.initials: VK
authors.lastname: Randhawa
authors.affiliation: Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8.
authors.forename: Hilal
authors.initials: H
authors.lastname: Zaid
authors.affiliation: Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada. Electronic address: amira@sickkids.ca.
authors.forename: Amira
authors.initials: A
authors.lastname: Klip
mesh_terms: D000185:Actinin / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008954:Models, Biological; D009132:Muscles / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats
chemical_list: C491751:Actn4 protein, rat; D051275:Glucose Transporter Type 4; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D034741:RNA, Small Interfering; C495694:Slc2a4 protein, rat; D000185:Actinin; D005947:Glucose