title: Interaction of phosphatidylinositolglycan(-peptides) with plasma membrane lipid rafts triggers insulin-mimetic signaling in rat adipocytes.
abstract: The phosphoinositolglycan(-peptide) (PIG-P) portion of glycosylphosphatidylinositol-anchored plasma membrane (GPI) proteins or synthetic PIG(-P) molecules interact with proteinaceous binding sites which are located in high-cholesterol-containing detergent/carbonate-insoluble glycolipid-enriched raft domains (hcDIGs) of the plasma membrane. In isolated rat adipocytes, PIG(-P) induce the redistribution of GPI proteins from hcDIGs to low-cholesterol-containing DIGs (lcDIGs) and concomitantly provoke insulin-mimetic signaling and metabolic action. Using a set of synthetic PIG(-P) derivatives we demonstrate here that their specific binding to hcDIGs and their insulin-mimetic signaling/metabolic activity strictly correlate with respect to (i) translocation of the GPI proteins, Gce1 and 5(')-nucleotidase, from hcDIGs to lcDIGs, (ii) dissociation of the nonreceptor tyrosine kinase, pp59(Lyn), from caveolin residing at hcDIGs, (iii) translocation of pp59(Lyn) from hcDIGs to lcDIGs, (iv) activation of pp59(Lyn), (v) tyrosine phosphorylation of insulin receptor substrate proteins-1/2, and finally (vi) stimulation of glucose transport. The natural PIG(-P) derived from the carboxy-terminal tripeptide of Gce1, YCN-PIG, exhibits the highest potency followed by a combination of the separate peptidylethanolamidyl and PIG constituents. We conclude that efficient positive cross-talk of PIG(-P) to the insulin signaling cascade requires their interaction with hcDIGs. We suggest that PIG(-P) thereby displace GPI proteins from binding to hcDIGs leading to their release from hcDIGs for lateral movement to lcDIGs which initiates signal transduction from DIGs via caveolin and pp59(Lyn) to the insulin receptor substrate proteins of the insulin signaling pathway.
authors.affiliation: Aventis Pharma Germany, DG Metabolic Diseases, Industrial Park Höchst, Bldg. H825, 65926, Frankfurt am Main, Germany. Guenter.Mueller@aventis.com
authors.forename: Günter
authors.initials: G
authors.lastname: Müller
authors.forename: Christian
authors.initials: C
authors.lastname: Jung
authors.forename: Wendelin
authors.initials: W
authors.lastname: Frick
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Bandlow
authors.forename: Werner
authors.initials: W
authors.lastname: Kramer
mesh_terms: D017667:Adipocytes / Q000502:physiology*; D000818:Animals; D001692:Biological Transport; D051242:Caveolin 1; D022461:Caveolins / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D003847:Deoxyglucose / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D007700:Kinetics; D021962:Membrane Microdomains / Q000502:physiology*; D010455:Peptides / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D020239:Receptor Cross-Talk; D015398:Signal Transduction / Q000502:physiology*
chemical_list: C495537:Cav1 protein, rat; D051242:Caveolin 1; D022461:Caveolins; D003902:Detergents; D017261:Glycosylphosphatidylinositols; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010455:Peptides; D010750:Phosphoproteins; D003847:Deoxyglucose; D005947:Glucose