title: A novel pleckstrin homology domain-containing protein enhances insulin-stimulated Akt phosphorylation and GLUT4 translocation in adipocytes.
abstract: 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.
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
authors.forename: Qiong L
authors.initials: QL
authors.lastname: Zhou
authors.forename: Zhen Y
authors.initials: ZY
authors.lastname: Jiang
authors.forename: Allan S
authors.initials: AS
authors.lastname: Mabardy
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Del Campo
authors.forename: David G
authors.initials: DG
authors.lastname: Lambright
authors.forename: John
authors.initials: J
authors.lastname: Holik
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Fogarty
authors.forename: Juerg
authors.initials: J
authors.lastname: Straubhaar
authors.forename: Sarah
authors.initials: S
authors.lastname: Nicoloro
authors.forename: Anil
authors.initials: A
authors.lastname: Chawla
authors.forename: Michael P
authors.initials: MP
authors.lastname: Czech
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001798:Blood Proteins / Q000737:chemistry; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D001798:Blood Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; C552438:PHLDB1 protein, mouse; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; C060974:phosphatidylinositol 3,4,5-triphosphate; C060980:phosphatidylinositol 3,4-diphosphate; C039077:platelet protein P47; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D005947:Glucose