title: Tissue-specific differences in activation of atypical protein kinase C and protein kinase B in muscle, liver, and adipocytes of insulin receptor substrate-1 knockout mice.
abstract: Insulin receptor substrates (IRSs) 1 and 2 are postulated to control the activation of phosphatidylinositol 3-kinase (PI3K)-dependent signaling factors, namely, atypical protein kinase C (aPKC) and protein kinase B (PKB)/Akt, which mediate metabolic effects of insulin. However, it is uncertain whether aPKC and PKB are activated together or differentially in response to IRS-1 and IRS-2 activation in insulin-sensitive tissues. Presently, we examined insulin activation of aPKC and PKB in vastus lateralis muscle, adipocytes, and liver in wild-type and IRS-1 knockout mice, and observed striking tissue-specific differences. In muscle of IRS-1 knockout mice, the activation of both aPKC and PKB was markedly diminished. In marked contrast, only aPKC activation was diminished in adipocytes, and only PKB activation was diminished in liver. These results suggest that IRS-1 is required for: 1) activation of both aPKC and PKB in muscle; 2) aPKC, but not PKB, activation in adipocytes; and 3) PKB, but not aPKC, activation in liver. Presumably, IRS-2 or other PI3K activators account for the normal activation of aPKC in liver and PKB in adipocytes of IRS-1 knockout mice. These complexities in aPKC and PKB activation may be relevant to metabolic abnormalities seen in tissues in which IRS-1 or IRS-2 is specifically or predominantly down-regulated.
authors.affiliation: Research Service, James A. Haley Veterans Hospital and the Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
authors.forename: Mini P
authors.initials: MP
authors.lastname: Sajan
authors.forename: Mary L
authors.initials: ML
authors.lastname: Standaert
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miura
authors.forename: C Ron
authors.initials: CR
authors.lastname: Kahn
authors.forename: Robert V
authors.initials: RV
authors.lastname: Farese
mesh_terms: D017667:Adipocytes / Q000201:enzymology / Q000502:physiology; D000818:Animals; D004789:Enzyme Activation; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000201:enzymology / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000201:enzymology / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D017384:Sequence Deletion; D015398:Signal Transduction
chemical_list: D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C