title: Bruton tyrosine kinase is essential for botrocetin/VWF-induced signaling and GPIb-dependent thrombus formation in vivo.
abstract: Botrocetin (bt)-facilitated binding of von Willebrand factor (VWF) to the platelet membrane glycoprotein (GP) Ib-IX-V complex on platelets in suspension initiates a signaling cascade that causes alphaIIbbeta3 activation and platelet aggregation. Previous work has demonstrated that bt/VWF-mediated agglutination activates alphaIIbbeta3 and elicits ATP secretion in a thromboxane A2 (TxA2)-dependent manner. The signaling that results in TxA2 production was shown to be initiated by Lyn, enhanced by Src, and propagated through Syk, SLP-76, PI3K, PLCgamma2, and PKC. Here, we demonstrate that the signaling elicited by GPIb-mediated agglutination that results in TxA2 production is dependent on Bruton tyrosine kinase (Btk). The results demonstrate that Btk is downstream of Lyn, Syk, SLP-76, and PI3K; upstream of ERK1/2, PLCgamma2, and PKC; and greatly enhances Akt phosphorylation. The relationship(s), if any, between ERK1/2, PLCgamma2, and PKC were not elucidated. The requirement for Btk and TxA2 receptor function in GPIb-dependent arterial thrombosis was confirmed in vivo by characterizing blood flow in ferric chloride-treated mouse carotid arteries. These results demonstrate that the Btk family kinase, Tec, cannot provide the function(s) missing because of the absence of Btk and that Btk is essential for both bt/VWF-mediated agglutination-induced TxA2 production and GPIb-dependent stable arterial thrombus formation in vivo.
authors.affiliation: Department of Biology, University of Memphis, Memphis, TN 38152, USA.
authors.forename: Junling
authors.initials: J
authors.lastname: Liu
authors.forename: Malinda E
authors.initials: ME
authors.lastname: Fitzgerald
authors.forename: Michael C
authors.initials: MC
authors.lastname: Berndt
authors.forename: Carl W
authors.initials: CW
authors.lastname: Jackson
authors.forename: T Kent
authors.initials: TK
authors.lastname: Gartner
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D002341:Carotid Artery Thrombosis / Q000097:blood / Q000209:etiology; D003435:Crotalid Venoms / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D051966:Phospholipase C gamma / Q000097:blood; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000502:physiology; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013927:Thrombosis / Q000097:blood* / Q000209:etiology; D013928:Thromboxane A2 / Q000097:blood; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D003435:Crotalid Venoms; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; D013928:Thromboxane A2; C030961:botrocetin; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse; D051966:Phospholipase C gamma