Lipopolysaccharide signaling without a nucleus: kinase cascades stimulate platelet shedding of proinflammatory XXXX -rich microparticles.

@entity1 @entity558 @entity10151 @entity1356 @entity5750 @entity4100 @entity1193 @entity584 @entity4101 @entity23983 @entity4725 @entity2939 @entity47529 @entity9302
Platelets contain unspliced heteronuclear @entity1356 RNA, which is rapidly spliced and translated upon activation. @entity558 is a superior agonist for this atypical platelet response, but how @entity558 induces proinflammatory cytokine production in anucleate cells lacking NF-kB is unknown. Platelets express functional @entity2939 , and stimulation by @entity558 induced rapid splicing, translation, and secretion of mature @entity1356 after @entity9302 processing. @entity558 stimulated microparticle shedding, and secreted @entity1356 was exclusively present in these particles. Microparticles from @entity558 -stimulated platelets induced @entity4725 production by cultured @entity1 endothelial cells, and blockade of endothelial @entity1356 receptor with @entity1193 completely suppressed endothelial activation. Splicing was posttranscriptional as the SR kinase inhibitor @entity47529 blocked @entity1356 RNA production by platelets, but not by monocytes, and was dependent on exogenous @entity5750 --a property of platelets. We used a combination of small-molecule inhibitors, cell-penetrating chimeric peptide inhibitors, and gene-targeted animals to show splicing required @entity4100 and @entity23983 , and @entity4101 /4, @entity584 , and JNK phosphorylation and activation. @entity10151 couples @entity4100 to the @entity584 pathway and, remarkably, a @entity10151 interacting peptide-antennapedia chimera was more effective than @entity558 in stimulating @entity1356 splicing. The @entity10151 chimera did not, however, stimulate microparticle shedding, nor was @entity1356 released. We conclude @entity558 -induced kinase cascades are sufficient to alter cellular responses, that three signals emanate from platelet @entity2939 , and that @entity584 and JNK activation are sufficient to initiate posttranscriptional splicing while another event couples microparticle shedding to @entity2939 activation. Platelets contribute to the inflammatory response to @entity558 through production of microparticles that promote endothelial cell activation.
