A novel pleckstrin homology domain-containing protein enhances insulin-stimulated Akt phosphorylation and GLUT4 translocation in adipocytes
Department of Biochemistry and Molecular Pharmacology; Department of Physiology; Program in Molecular Medicine
3T3-L1 Cells; Adipocytes; Animals; Blood Proteins; Enzyme Activation; Gene Expression Regulation; Gene Silencing; Glucose; Glucose Transporter Type 4; Humans; Insulin; Intracellular Signaling Peptides and; Proteins; Mice; Phosphatidylinositol Phosphates; Phosphoproteins; Phosphorylation; Protein Structure, Tertiary; Protein Transport; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases, 70-kDa; Sequence Homology, Amino Acid
Life Sciences | Medicine and Health Sciences | Women's Studies
Protein kinase B/Akt protein kinases control an array of diverse functions, including cell growth, survival, proliferation, and metabolism. We report here the identification of pleckstrin homology-like domain family B member 1 (PHLDB1) as an insulin-responsive protein that enhances Akt activation. PHLDB1 contains a pleckstrin homology domain, which we show binds phosphatidylinositol PI(3,4)P(2), PI(3,5)P(2), and PI(3,4,5)P(3), as well as a Forkhead-associated domain and coiled coil regions. PHLDB1 expression is increased during adipocyte differentiation, and it is abundant in many mouse tissues. Both endogenous and HA- or GFP-tagged PHLDB1 displayed a cytoplasmic disposition in unstimulated cultured adipocytes but translocated to the plasma membrane in response to insulin. Depletion of PHLDB1 by siRNA inhibited insulin stimulation of Akt phosphorylation but not tyrosine phosphorylation of IRS-1. RNAi-based silencing of PHLDB1 in cultured adipocytes also attenuated insulin-stimulated deoxyglucose transport and Myc-GLUT4-EGFP translocation to the plasma membrane, whereas knockdown of the PHLDB1 isoform PHLDB2 failed to attenuate insulin-stimulated deoxyglucose transport. Furthermore, adenovirus-mediated expression of PHLDB1 in adipocytes enhanced insulin-stimulated Akt and p70 S6 kinase phosphorylation, as well as GLUT4 translocation. These results indicate that PHLDB1 is a novel modulator of Akt protein kinase activation by insulin.
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Citation: J Biol Chem. 2010 Sep 3;285(36):27581-9. Epub 2010 Jun 28. Link to article on publisher's site