Differential effects of constitutively active phosphatidylinositol 3-kinase on glucose transport, glycogen synthase activity, and DNA synthesis in 3T3-L1 adipocytes.
Abstract
Differential effects of constitutively active phosphatidylinositol 3-kinase on glucose transport, glycogen synthase activity, and DNA synthesis in 3T3-L1 adipocytes. E U Frevert and B B Kahn Department of Medicine, Beth Israel Hospital, Boston, Massachusetts 02215, USA. ABSTRACT Phosphatidylinositol 3-kinase (PI3K) activation is necessary for many insulin-induced metabolic and mitogenic responses. However, it is unclear whether PI3K activation is sufficient for any of these effects. To address this question we increased PI3K activity in differentiated 3T3-L1 adipocytes by adenovirus-mediated expression of both the inter-SH2 region of the regulatory p85 subunit of PI3K (iSH2) and the catalytic p110 alpha subunit (p110). Coexpression resulted in PI3K activity that exceeded insulin-stimulated activity by two- to fivefold in cytosol, total membranes, and the low density microsome (LDM) fraction, the site of greatest insulin stimulation. While insulin increased glucose transport 15-fold, coexpression of iSH2-p110 increased transport (5.2-) +/- 0.7-fold with a parallel increase in GLUT4 translocation to the plasma membrane. Constitutive activation of PI3K had no effect on maximally insulin-stimulated glucose transport. Neither basal nor insulin-stimulated activity of glycogen synthase or mitogen-activated protein kinase was altered by iSH2-p110 coexpression. DNA synthesis was increased twofold by insulin in control 3T3-L1 adipocytes transduced with beta-galactosidase-encoding recombinant adenovirus, while iSH2-p110 coexpression increased DNA synthesis fivefold. These data indicate that (i) increased PI3K activity is sufficient to activate some but not all metabolic responses to insulin, (ii) activation of PI3K to levels exceeding the effect of insulin in adipocyte LDM results in only a partial stimulation of glucose transport, and (iii) increased PI3K activity in the absence of growth factor or oncoprotein stimulation is a potent stimulus of DNA synthesis. CiteULike Connotea Delicious Digg Facebook Google+ Mendeley Reddit StumbleUpon Twitter What's this? « Previous | Next Article » Table of Contents This Article Mol. Cell. Biol. January 1997 vol. 17 no. 1 190-198 » Abstract PDF Services Email this article to a colleague Similar articles in ASM journals Alert me when this article is cited Alert me if a correction is posted Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of MCB Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Load citing article information Citing articles via Web of Science Citing articles via Google Scholar Google Scholar Articles by Frevert, E. U. Articles by Kahn, B. B. Search for related content PubMed PubMed citation Articles by Frevert, E. U. Articles by Kahn, B. B. Related Content Load related web page information Social Bookmarking CiteULike Connotea Delicious Digg Facebook Google+ Mendeley Reddit StumbleUpon Twitter What's this? current issue January 2012, volume 32, issue 1 Spotlights in the Current Issue Architecture of the Yeast RNA Polymerase II Open Complex State and Regulation by TFIIF GATA-1 Establishes Cell-Type-Specific Autophagy as a Developmental Program Prickle Phosphorylation Regulates Its Localization and β-Catenin-Independent Wnt Signaling Alert me to new issues of MCB About MCB Subscribers Authors Reviewers Advertisers Inquiries from the Press Permissions & Commercial Reprints ASM Journals Public Access Policy MCB RSS Feeds 1752 N Street N.W. • Washington DC 20036 202.737.3600 • 202.942.9355 fax • journals@asmusa.org Print ISSN: 0270-7306 Online ISSN: 1098-5549 Copyright © 2011 by the American Society for Microbiology. For an alternate route to MCB .asm.org, visit: http://intl- MCB .asm.org | More Info» var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); var pageTracker = _gat._getTracker("UA-5821458-11"); pageTracker._trackPageview();