Abstract
The thiazolidinedione (TZD), rosiglitazone, has previously been found to tyrosine-phosphorylate Cbl and activate Cbl-dependent phosphatidylinositol (PI) 3-kinase and atypical protein kinase Cs (aPKCs) while stimulating glucose transport in 3T3/L1 adipocytes. Presently, the role of Cbl in rosiglitazone action was further assessed in both 3T3/L1 and human adipocytes by expressing Y371F and/or Y731F mutant forms of Cbl that nullified the functionality of canonical pYXXM motifs in Cbl. These mutants diminished the interaction of Cbl with the p85 subunit of PI 3-kinase and inhibited subsequent increases in Cbl-dependent PI 3-kinase activity, aPKC activity, and glucose transport. These mutants also inhibited the interaction of Cbl with Crk, which has been implicated in the activation of other PI 3-kinase-independent signaling factors that have been found to be required during activation of glucose transport by insulin and other agonists. We conclude that pYXXM motifs in Cbl serve to activate PI 3-kinase-dependent and possibly PI 3-kinase-independent pathways that are required for TZD-dependent glucose transport in adipocytes.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3-L1 Cells
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Adipocytes / drug effects
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Adipocytes / enzymology*
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Adipocytes / metabolism
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Amino Acid Motifs
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Animals
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Biological Transport / drug effects
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Cells, Cultured
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Deoxyglucose / antagonists & inhibitors
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Deoxyglucose / metabolism
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Enzyme Activation / drug effects
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Enzyme Activation / genetics
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Glucose / metabolism*
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Humans
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Insulin / pharmacology
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Isoenzymes
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Mice
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Mutagenesis, Site-Directed
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphoinositide-3 Kinase Inhibitors
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Protein Binding
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Protein Kinase C / metabolism*
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Protein Subunits / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins / physiology*
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Proto-Oncogene Proteins c-cbl
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Proto-Oncogene Proteins c-crk
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Thiazolidinediones / antagonists & inhibitors
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Thiazolidinediones / pharmacology*
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Ubiquitin-Protein Ligases*
Substances
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Insulin
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Isoenzymes
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Phosphoinositide-3 Kinase Inhibitors
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Protein Subunits
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-crk
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Thiazolidinediones
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Deoxyglucose
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2,4-thiazolidinedione
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Proto-Oncogene Proteins c-cbl
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Ubiquitin-Protein Ligases
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protein kinase C zeta
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PKC-3 protein
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Protein Kinase C
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protein kinase C lambda
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CBL protein, human
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Cbl protein, mouse
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Glucose