Essential role for membrane lipid rafts in interleukin-1beta-induced nitric oxide release from insulin-secreting cells: potential regulation by caveolin-1+.
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.
Veluthakal
Rajakrishnan
R
Department of Pharmaceutical Sciences, Wayne State University, 259 Mack Ave., Detroit, MI 48201, USA.
Chvyrkova
Irina
I
Tannous
Marie
M
McDonald
Phillip
P
Amin
Rajesh
R
Hadden
Timothy
T
Thurmond
Debbie C
DC
Quon
Michael J
MJ
Kowluru
Anjaneyulu
A
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
D007375:Interleukin-1; D009569:Nitric Oxide; D011505:Protein-Tyrosine Kinases