Signaling role for phospholipase Cγ2 in platelet glycoprotein Ibα calcium flux and cytoskeletal reorganization -: Involvement of a pathway distinct from FcRγ chain and FcγRIIA
Signaling role for phospholipase Cγ2 in platelet glycoprotein Ibα calcium flux and cytoskeletal reorganization -: Involvement of a pathway distinct from FcRγ chain and FcγRIIA
复制标题
DOI：
10.1074/jbc.m302333200
复制
发表时间：
2003-08-29
影响因子：
4.8
通讯作者：
Lanza, F
中科院分区：
文献类型：
--
作者：
Mangin, P;Yuan, YP;Lanza, F
血小板糖蛋白Ib - V - IX复合物与表面固定的血管性血友病因子（vWf）相互作用是捕获循环血小板及其后续激活所必需的。在先前的研究中发现，糖蛋白Ib/vWf介导的血小板黏附触发细胞内储存的Ca²⁺释放，导致细胞骨架重排和丝状伪足伸展。尽管糖蛋白Ib诱导的细胞骨架变化具有潜在的功能重要性，但调节这一过程的信号机制仍不明确。此处所呈现的研究表明，磷脂酶C（PLC）依赖的磷酸肌醇周转在糖蛋白Ib依赖的细胞骨架重塑中具有重要作用。以下发现支持了这一点：vWf - 糖蛋白Ib相互作用诱导肌醇1,4,5 - 三磷酸（IP₃）少量增加，并且用IP₃受体拮抗剂APB - 2或PLC抑制剂U73122处理血小板可阻断胞质Ca²⁺通量和血小板形状改变。在Gαₑ（-/-）小鼠血小板中观察到正常的形状改变，排除了PLCβ异构体在这一过程中的作用。然而，在缺乏PLCγ2的小鼠中观察到形状改变和Ca²⁺动员减少，表明该同种型在糖蛋白Ib信号传导中起重要作用，尽管作用不完全。糖蛋白Ib所利用的信号通路涉及Src激酶家族的一个或多个成员，因为血小板形状改变和Ca²⁺通量被Src激酶抑制剂PP1和PP2抑制。引人注目的是，形状改变和Ca²⁺释放独立于含免疫受体酪氨酸激活基序（ITAM）的受体发生，因为在用抗FcγRIIA阻断性单克隆抗体IV.3处理的人血小板以及缺乏FcRγ链的小鼠血小板中，这些血小板反应是正常的。综上所述，这些研究确定了PLCγ2在与血小板形状改变相关的糖蛋白Ib信号传导中的重要作用。此外，它们表明糖蛋白Ib依赖的钙通量和细胞骨架重排涉及一种不同于含ITAM受体所利用的信号通路。
Interaction of the platelet GPIb-V-IX complex with surface immobilized von Willebrand factor (vWf) is required for the capture of circulating platelets and their ensuing activation. In previous work, it was found that GPIb/vWf-mediated platelet adhesion triggers Ca2+ release from intracellular stores, leading to cytoskeletal reorganization and filopodia extension. Despite the potential functional importance of GPIb-induced cytoskeletal changes, the signaling mechanisms regulating this process have remained ill-defined. The studies presented here demonstrate an important role for phospholipase C ( PLC)-dependent phosphoinositide turnover for GPIb-dependent cytoskeletal remodeling. This is supported by the findings that the vWf-GPIb interaction induced a small increase in inositol 1,4,5-triphosphate (IP3) and that treating platelets with the IP3 receptor antagonist APB-2 or the PLC inhibitor U73122 blocked cytosolic Ca2+ flux and platelet shape change. Normal shape change was observed in Galpha(q)(-/-) mouse platelets, excluding a role for PLCbeta isoforms in this process. However, decreased shape change and Ca2+ mobilization were observed in mice lacking PLCgamma2, demonstrating that this isotype played an important, albeit incomplete, role in GPIb signaling. The signaling pathways utilized by GPIb involved one or more members of the Src kinase family as platelet shape change and Ca2+ flux were inhibited by the Src kinase inhibitors PP1 and PP2. Strikingly, shape change and Ca2+ release occurred independently of immunoreceptor tyrosine-based activation motif (ITAM)-containing receptors, because these platelet responses were normal in human platelets treated with the anti-FcgammaRIIA blocking monoclonal antibody IV.3 and in mouse platelets deficient in the FcRgamma chain. Taken together, these studies define an important role for PLCgamma2 in GPIb signaling linked to platelet shape change. Moreover, they demonstrate that GPIb-dependent calcium flux and cytoskeletal reorganization involves a signaling pathway distinct from that utilized by ITAM-containing receptors.