title: Phosphatidylinositol 4,5-bisphosphate regulates adipocyte actin dynamics and GLUT4 vesicle recycling.
abstract: To investigate the potential role of phosphatidylinositol 4, 5-bisphosphate (PI(4,5)P2) in the regulation of actin polymerization and GLUT4 translocation, the type I phosphatidylinositol 4-phosphate 5-kinases (PIP5Ks) were expressed in 3T3L1 adipocytes. In preadipocytes (fibroblasts) PIP5K expression promoted actin polymerization on membrane-bound vesicles to form motile actin comets. In contrast, expression of PIP5K in differentiated 3T3L1 adipocytes resulted in the formation of enlarged vacuole-like structures coated with F-actin, cortactin, dynamin, and N-WASP. Treatment with either latrunculin B (an inhibitor for actin polymerization) or Clostridium difficile toxin B (a general Rho family inhibitor) resulted in a relatively slower disappearance of coated F-actin from these vacuoles, but the vacuoles themselves remained unaffected. Functionally, the increased PI(4,5)P2 levels resulted in an inhibition of transferrin receptor and GLUT4 endocytosis and a slow accumulation of these proteins in the PI(4,5)P2-enriched vacuoles along with the non-clathrin-derived endosome marker (caveolin) and the AP-2 adaptor complex. However, these structures were devoid of early endosome markers (EEA1, clathrin) and the biosynthetic membrane secretory machinery markers p115 (Golgi) and syntaxin 6 (trans-Golgi Network). Taken together, these data demonstrate that PI(4,5)P2 has distinct morphologic and functional properties depending upon specific cell context. In adipocytes, altered PI(4,5)P2 metabolism has marked effects on GLUT4 endocytosis and intracellular vesicle trafficking due to the derangement of actin dynamics.
authors.affiliation: Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794, USA. kanzaki@tubero.tohoku.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Kanzaki
authors.forename: Megumi
authors.initials: M
authors.lastname: Furukawa
authors.forename: William
authors.initials: W
authors.lastname: Raab
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Pessin
mesh_terms: D041721:3T3-L1 Cells / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D051356:Cortactin; D003603:Cytotoxins / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D051275:Glucose Transporter Type 4; D006056:Golgi Apparatus / Q000378:metabolism; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding; D050765:Qa-SNARE Proteins; D011990:Receptors, Transferrin / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D013997:Time Factors; D014162:Transfection; D033921:Vesicular Transport Proteins; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002352:Carrier Proteins; D002966:Clathrin; D051356:Cortactin; C495869:Cttn protein, mouse; D003603:Cytotoxins; D018076:DNA, Complementary; D051275:Glucose Transporter Type 4; D000077614:Golgi Matrix Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D050765:Qa-SNARE Proteins; D011990:Receptors, Transferrin; C495693:Slc2a4 protein, mouse; D013844:Thiazoles; D053778:Thiazolidines; D033921:Vesicular Transport Proteins; C495772:Wasl protein, mouse; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; C031815:toxB protein, Clostridium difficile; C091580:vesicular transport factor p115; D002784:Cholesterol; D034281:Dynamins; C037068:latrunculin B