title: Essential role for membrane lipid rafts in interleukin-1beta-induced nitric oxide release from insulin-secreting cells: potential regulation by caveolin-1+.
abstract: We recently reported that the activation of H-Ras represents one of the signaling steps underlying the interleukin-1beta (IL-1beta)-mediated metabolic dysfunction of the islet beta-cell. In the present study, we examined potential contributory roles of membrane-associated, cholesterol-enriched lipid rafts/caveolae and their constituent proteins (e.g., caveolin-1 [Cav-1]) as potential sites for IL-1beta-induced nitric oxide (NO) release in the isolated beta-cell. Disruption of lipid rafts (e.g., with cyclodextrin) markedly reduced IL-1beta-induced gene expression of inducible NO synthase (iNOS) and NO release from beta-cells. Immunologic and confocal microscopic evidence also suggested a transient but significant stimulation of tyrosine phosphorylation of Cav-1 in beta-cells briefly (for 15 min) exposed to IL-1beta that was markedly attenuated by three structurally distinct inhibitors of protein tyrosine phosphorylation. Overexpression of an inactive mutant of Cav-1 lacking the tyrosine phosphorylation site (Y14F) or an siRNA-mediated Cav-1 knock down also resulted in marked attenuation of IL-1beta-induced iNOS gene expression and NO release from these cells, thus further implicating Cav-1 in this signaling cascade. IL-1beta treatment also increased (within 20 min) the translocation of H-Ras into lipid rafts. Here we provide the first evidence to suggest that tyrosine phosphorylation of Cav-1 and subsequent interaction among members of the Ras signaling pathway within the membrane lipid microdomains represent early signaling mechanisms of IL-1beta in beta-cells.
authors.affiliation: Department of Pharmaceutical Sciences, Wayne State University, 259 Mack Ave., Detroit, MI 48201, USA.
authors.forename: Rajakrishnan
authors.initials: R
authors.lastname: Veluthakal
authors.forename: Irina
authors.initials: I
authors.lastname: Chvyrkova
authors.forename: Marie
authors.initials: M
authors.lastname: Tannous
authors.forename: Phillip
authors.initials: P
authors.lastname: McDonald
authors.forename: Rajesh
authors.initials: R
authors.lastname: Amin
authors.forename: Timothy
authors.initials: T
authors.lastname: Hadden
authors.forename: Debbie C
authors.initials: DC
authors.lastname: Thurmond
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Quon
authors.forename: Anjaneyulu
authors.initials: A
authors.lastname: Kowluru
mesh_terms: D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation / Q000502:physiology; D011905:Genes, ras; D007375:Interleukin-1 / Q000502:physiology*; D007515:Islets of Langerhans / Q000502:physiology*; D008297:Male; D021962:Membrane Microdomains / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
chemical_list: D007375:Interleukin-1; D009569:Nitric Oxide; D011505:Protein-Tyrosine Kinases