APS facilitates c-Cbl tyrosine phosphorylation and GLUT4 translocation in response to insulin in 3T3-L1 adipocytes.
APS is a Cbl-binding protein that is tyrosine phosphorylated by the insulin receptor kinase. Insulin-stimulated phosphorylation of tyrosine 618 in APS is necessary for its association with c-Cbl and the subsequent tyrosine phosphorylation of Cbl by the insulin receptor in both 3T3-L1 adipocytes and CHO-IR cells. When overexpressed in these cells, wild-type APS but not an APS/Y(618)F mutant facilitated the tyrosine phosphorylation of coexpressed Cbl and its association with Crk upon insulin stimulation. APS-facilitated phosphorylation occurred on tyrosines 371, 700, and 774 in the Cbl protein. APS also interacted directly with the c-Cbl-associated protein (CAP) and colocalized with the protein in cells. The association was dependent on the SH3 domains of CAP and was independent of insulin treatment. Overexpression of the APS/Y(618)F mutant in 3T3-L1 adipocytes blocked the insulin-stimulated tyrosine phosphorylation of endogenous Cbl and binding to Crk. Moreover, the translocation of GLUT4 from intracellular vesicles to the plasma membrane was also inhibited by overexpression of the APS/Y(618)F mutant. These data suggest that APS serves as an adapter protein linking the CAP/Cbl pathway to the insulin receptor and, further, that APS-facilitated Cbl tyrosine phosphorylation catalyzed by the insulin receptor is a crucial event in the stimulation of glucose transport by insulin.
Liu
Jun
J
Department of Internal Medicine and Physiology, Life Science Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
Kimura
Akiko
A
Baumann
Christian A
CA
Saltiel
Alan R
AR
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D016466:CHO Cells; D002454:Cell Differentiation; D006224:Cricetinae; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl; D050737:Proto-Oncogene Proteins c-crk; D011972:Receptor, Insulin / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases
D048868:Adaptor Proteins, Signal Transducing; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; C488161:Sh2b2 protein, mouse; C495693:Slc2a4 protein, mouse; D014443:Tyrosine; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D011972:Receptor, Insulin; C067419:CBL protein, human; C493849:Cbl protein, mouse; D005947:Glucose