Regulation of sphingosine 1-phosphate-induced endothelial cytoskeletal rearrangement and barrier enhancement by S1P1 receptor, PI3 kinase, Tiam1/Rac1, and alpha-actinin.
Endothelial cell (EC) barrier dysfunction results in increased vascular permeability observed in inflammation, tumor angiogenesis, and atherosclerosis. The platelet-derived phospholipid sphingosine-1-phosphate ( S1P) decreases EC permeability in vitro and in vivo and thus has obvious therapeutic potential. We examined S1P-mediated human pulmonary artery EC signaling and barrier regulation in caveolin-enriched microdomains (CEM). Immunoblotting from S1P-treated EC revealed S1P-mediated rapid recruitment (1 microM, 5 min) to CEMs of the S1P receptors S1P1 and S1P3, p110 PI3 kinase alpha and beta catalytic subunits, the Rac1 GEF, Tiam1, and alpha-actinin isoforms 1 and 4. Immunoprecipitated p110 PI3 kinase catalytic subunits from S1P-treated EC exhibited PIP3 production in CEMs. Immunoprecipitation of S1P receptors from CEM fractions revealed complexes containing Tiam1 and S1P1. PI3 kinase inhibition (LY294002) attenuated S1P- induced Tiam1 association with S1P1, Tiam1/Rac1 activation, alpha-actinin-1/4 recruitment, and EC barrier enhancement. Silencing of either S1P1 or Tiam1 expression resulted in the loss of S1P- mediated Rac1 activation and alpha-actinin-1/4 recruitment to CEM. Finally, silencing S1P1, Tiam1, or both alpha-actinin isoforms 1/4 inhibits S1P-induced cortical F-actin rearrangement and S1P-mediated barrier enhancement. Taken together, these results suggest that S1P- induced recruitment of S1P1 to CEM fractions promotes PI3 kinase- mediated Tiam1/Rac1 activation required for alpha-actinin-1/4-regulated cortical actin rearrangement and EC barrier enhancement.[1]References
- Regulation of sphingosine 1-phosphate-induced endothelial cytoskeletal rearrangement and barrier enhancement by S1P1 receptor, PI3 kinase, Tiam1/Rac1, and alpha-actinin. Singleton, P.A., Dudek, S.M., Chiang, E.T., Garcia, J.G. FASEB J. (2005) [Pubmed]
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