Receptor type protein tyrosine phosphatase, RPTPbeta on the surface of platelets:relationship to the Helicobacter pylori-related disease

据报道，幽门螺杆菌与胃溃疡/癌症、特发性血小板减少性紫癜和缺血性心脏病有关。我们推测，幽门螺杆菌相关疾病的原因之一是VacA通过与RPTPβ相互作用刺激血小板激活。2007年这项研究的目的是证明VacA通过与RPTPβ基因缺陷小鼠的RPTPβ相互作用来刺激血小板，2007年的研究目的是研究RPTPβ介导的信号转导途径。2006年，我们未能证明VacA通过与RPTPβ相互作用来刺激血小板，并失去了使用RPTPβ缺陷小鼠的机会。因此，我们试图鉴定血小板中的另一种VacA受体。MS/MS分析显示，一种大分子储存在血小板α颗粒(名为蛋白X)中，作为与VacA包被的珠子相关的蛋白质之一。用Biacore证实了VacA与GST-Protein X融合蛋白的结合。我们现在正在调查PRO…中的VacA结合位点在其他细胞中，据报道，在VacA刺激下，RPTPbeta下游的一种适配蛋白Git-1经历了酪氨酸磷酸化。虽然VacA不能刺激血小板Git 1的酪氨酸磷酸化，但它是由整合素αIIbβ3下游的外向内信号激活的。由于目前还没有关于Git 1在血小板中表达的报道，我们决定研究Git 1在血小板中的调控。我们发现Git 1在血小板中大量表达，并在整合素αIIbβ3下游发生酪氨酸磷酸化，这一过程被Src激酶抑制剂PP2抑制。此外，GIT1与RAC的鸟嘌呤核苷酸交换因子BetaPlX存在结构性关联。GIT1/betaPIX复合体与allbp3结合，伴随GIT1酪氨酸磷酸化。此外，GIT1和αIIbβ3在血小板聚集过程中都迅速转移到细胞骨架部分，而在没有聚集的情况下没有观察到这一点。这些结果表明，Src激酶对Git1的酪氨酸磷酸化可能通过使α-ββPlX靠近整合素来调节RAC-IIb-Git-3下游的细胞骨架重组。较少

Helicobacter pylori is reportedly related to gastric ulcer/cancer, idiopathic thrombocytopenic purpura, and ischemic heart disease. We hypothesized that one of the causes of pylori-related diseases is VacA-stimulated platelet activation through interaction with RPTPbeta. The aim of this study in 2007 is to prove that VacA stimulates platelets by interacting with RPTPbeta using RPTPbeta-deficient mice and that in 2007 is to investigate signal transduction pathway mediated through RPTPbeta. In 2006, we failed to prove that VacA stimulates platelets by interacting with RPTPbeta and lost opportunity to use RPTPbeta-deficient mice. Therefore, we sought to identify another VacA receptor in platelets. MS/MS analysis revealed a macromolecule that is stored in the platelet alpha granule (named protein X) as one of the proteins associated with VacA-coated beads. We confirmed the binding between VacA and GST-protein X fusion protein using Biacore. We are now investigating VacA binding site in pro … More tein X. In other cells, an adapter protein, Git 1 is reported to undergo tyrosine phosphorylation downstream of RPTPbeta upon stimulation with VacA. Although VacA did not stimulate tyrosine phosphorylation of Git 1 in platelets, it is tyrosine-phosphorylated by outside-in signals downstream of integrin αIIbβ3. Since there has been no report about Git 1 expression in platelets, we decided to investigate regulation of Git 1 in platelets. We found that GIT 1 was abundantly expressed in platelets and underwent tyrosine phosphorylation downstream of integrin αIIbβ3, which was inhibited by the Src kinase inhibitor PP2. Furthermore, GIT1 constitutively associated with betaPlX, a guanine nucleotide exchange factor for Rac. The GIT1/betaPIX complex associated with allbp3, concomitantly with GIT1 tyrosine phosphorylation. Moreover, both GIT1 and αIIbβ3 rapidly translocated to the cytoskeletal fraction during platelet aggregation, which was not observed in the absence of aggregation. These results suggest that tyrosine phosphorylation of GIT1 by Src kinases may regulate cytoskeletal reorganization downstream of αIIbβ3 by bringing the Rac GEF betaPlX to the vicinity of the integrin. Less