P2Y2 receptor-mediated lymphotoxin-α secretion regulates intercellular cell adhesion molecule-1 expression in vascular smooth muscle cells.
The proinflammatory cytokine lymphotoxin-α (LTA) is thought to contribute to the pathogenesis of atherosclerosis. However, the mechanisms that regulate its expression in vascular smooth muscle cells (VSMC) are poorly understood. The ability of exogenous nucleotides to stimulate LTA production was evaluated in VSMC by ELISA. The P2Y(2) nucleotide receptor (P2Y(2)R) agonist UTP stimulates a strong and sustained release of LTA from WT but not P2Y(2)R(-/-) SMC. Assessment of LTA gene transcription by LTA promoter-luciferase construct indicated that LTA levels are controlled at the level of transcription. We show using RNAi techniques that knockdown of the actin-binding protein filamin-A (FLNa) severely impaired nucleotide-induced Rho activation and consequent Rho-mediated LTA secretion. Reintroduction of FLNa in FLNa RNAi SMC rescued UTP-induced LTA expression. In addition, we found that UTP-stimulated LTA secretion is not sensitive to brefeldin A, which blocks the formation of vesicles involved in protein transport from the endoplasmic reticulum to the Golgi apparatus, suggesting that P2Y(2)R/filamin-mediated secretion of LTA is independent of the endoplasmic reticulum/Golgi secretory vesicle route. Furthermore, UTP selectively induces ICAM-1 expression in WT but not SMC expressing a truncated P2Y(2)R deficient in LTA secretion. These data suggest that P2Y(2)R recruits FLNa to provide a cytoskeletal scaffold necessary for Rho signaling pathway upstream of LTA release and subsequent stimulation of ICAM-1 expression on vascular smooth muscle cells.
Departments of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202. Electronic address: cseye@iupui.edu.
Cheikh I
CI
Seye
Department of Veterinary Pathobiology, University of Missouri-Columbia, Columbia, Missouri 65201.
Yuksel
Y
Agca
Department of Veterinary Pathobiology, University of Missouri-Columbia, Columbia, Missouri 65201.
Cansu
C
Agca
Departments of Immunology and Microbiology, Indiana University School of Medicine, Indianapolis, Indiana 46202 and.
Wilbert
W
Derbigny
D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D003285:Contractile Proteins / Q000235:genetics / Q000378:metabolism; D064448:Filamins; D005786:Gene Expression Regulation / Q000502:physiology*; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis* / Q000235:genetics; D008233:Lymphotoxin-alpha / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D058921:Purinergic P2Y Receptor Antagonists; D058473:Receptors, Purinergic P2Y2 / Q000235:genetics / Q000378:metabolism*; D022142:Secretory Vesicles / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014544:Uridine Triphosphate / Q000494:pharmacology; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D003285:Contractile Proteins; D064448:Filamins; C090509:Icam1 protein, mouse; D008233:Lymphotoxin-alpha; D008840:Microfilament Proteins; D011500:Protein Synthesis Inhibitors; D058921:Purinergic P2Y Receptor Antagonists; D058473:Receptors, Purinergic P2Y2; D018799:Intercellular Adhesion Molecule-1; D020126:Brefeldin A; D020741:rho GTP-Binding Proteins; D014544:Uridine Triphosphate