Orai1-induced store-operated Ca2+ entry enhances phospholipase activity and modulates canonical transient receptor potential channel6 function in murine platelets
Orai1-induced store-operated Ca2+ entry enhances phospholipase activity and modulates canonical transient receptor potential channel6 function in murine platelets
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DOI：
10.1111/jth.12525
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发表时间：
2014-04-01
影响因子：
10.4
通讯作者：
Braun, A.
中科院分区：
文献类型：
--
作者：
Chen, W.;Thielmann, I.;Braun, A.
背景Orai1 是血小板中主要的钙池操纵的 Ca2+ 进入 (SOCE) 通道，不仅对于增强多种信号通路至关重要，而且还可能调节受体操纵的 Ca2+ 进入 (ROCE)。 Orai1 信号体与规范瞬时受体电位通道 (TRPC) 的动态耦合被认为是 SOCE 和 ROCE 激活的重要步骤。然而，Orai与TRPC异构体之间的生化相互作用的功能意义仍存在争议。目的我们旨在阐明Orai1在二酰基甘油(DAG)介导的ROCE中的作用。方法制备Trpc6(-/-)、Orai1(-/-)和Orai1(-/-)/Trpc6(-/-)小鼠，并对其血小板进行分析。结果毒胡萝卜素(TG)诱导的SOCE与Orai1(-/-)血小板相比，Orai1(-/-)/Trpc6(-/-)血小板进一步减少，从而揭示TG诱导的信号通路可以激活TRPC6。毒胡萝卜素诱导的 SOCE 导致野生型血小板中磷脂酶 C 和 D 活性增强。 TG 刺激后，Orai1(-/-) 血小板中两种酶的活性显着降低，而受体诱导的磷脂酶活性不受影响。此外，TG诱导和糖蛋白VI介导的血栓素A(2)释放强烈依赖于Orai1介导的SOCE。结论TRPC6活性的调节可以独立于与Orai1的物理相互作用而发生。 TRPC6 通过磷脂酶激活 Orai1 诱导 DAG 产生，与 Orai1 串扰。 Orai1 诱导的 DAG 产生和血栓素释放放大了血小板中 Ca2+ 信号传导的第二阶段。
BackgroundOrai1, the major store-operated Ca2+ entry (SOCE) channel in platelets, is not only critical for enhancing diverse signaling pathways, but may also regulate receptor-operated Ca2+ entry (ROCE). Dynamic coupling of the Orai1 signalosome to canonical transient receptor potential channels (TRPCs) has been suggested as an essential step in the activation of SOCE and ROCE. However, the functional significance of the biochemical interaction between Orai and TRPC isoforms remains controversial.ObjectiveWe aimed to elucidate the role of Orai1 in diacylglycerol (DAG)-mediated ROCE.MethodsTrpc6(-/-), Orai1(-/-) and Orai1(-/-)/Trpc6(-/-) mice were generated, and their platelets were analyzed.ResultsThapsigargin (TG)-induced SOCE was further reduced in Orai1(-/-)/Trpc6(-/-) platelets as compared with Orai1(-/-) platelets, thus revealing that TG-induced signaling pathways can activate TRPC6. Thapsigargin-induced SOCE leads to enhanced phospholipaseC and D activity in wild-type platelets. The activity of both enzymes was significantly reduced in Orai1(-/-) platelets upon TG stimulation, whereas receptor-induced phospholipase activity was not affected. Furthermore, TG-induced and glycoproteinVI-mediated thromboxaneA(2) release was strongly dependent on Orai1-mediated SOCE.ConclusionThe regulation of TRPC6 activity can occur independently of the physical interaction with Orai1. TRPC6 operates in crosstalk with Orai1 through Orai1-induced DAG production via phospholipase activation. Orai1-induced DAG production and thromboxane release amplify the second phase of Ca2+ signaling in platelets.