From the Institute of Experimental Biomedicine, University Hospital of Würzburg (S.K.G., W.C., I.C.B., K.W., S.S., B.N., A.B.), Rudolf Virchow Center (S.K.G., W.C., I.C.B., K.W., S.S., B.N., A.B.), and Institute of Clinical Epidemiology and Biometry, Comprehensive Heart Failure Center (P.K.), University of Würzburg, Germany; Department of Hepatology (H.M.H.) and Department of Neurology (P.K., G.S.), University Hospital of Würzburg, Germany; Walther-Straub-Institute for Pharmacology and Toxicology, Ludwig Maximilian University of Munich, Germany (S.Z., V.C., T.G.); Department of Immunology and Microbiology, University of Colorado, Denver (D.R., A.-L.P., C.S.); National Jewish Health, Denver, CO (D.R., A.-L.P., C.S.); Department of Molecular and Cellular Physiology, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan (M.M.); Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., Dortmund, Germany (R.P.Z.); School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, United Kingdom (P.J.N., M.G.T.); and Department of Bioinformatics, Functional Genomics and Systems Biology Group, University of Würzburg Biocenter, Germany (T.D.).
Arterioscler Thromb Vasc Biol. 2018 Feb;38(2):344-352. doi: 10.1161/ATVBAHA.117.310391. Epub 2017 Nov 16.
TRPM7 (transient receptor potential cation channel, subfamily M, member 7) is a ubiquitously expressed bifunctional protein comprising a transient receptor potential channel segment linked to a cytosolic α-type serine/threonine protein kinase domain. TRPM7 forms a constitutively active Mg and Ca permeable channel, which regulates diverse cellular processes in both healthy and diseased conditions, but the physiological role of TRPM7 kinase remains largely unknown.
Here we show that point mutation in TRPM7 kinase domain deleting the kinase activity in mice ( ) causes a marked signaling defect in platelets. platelets showed an impaired PIP2 (phosphatidylinositol-4,5-bisphosphate) metabolism and consequently reduced Ca mobilization in response to stimulation of the major platelet receptors GPVI (glycoprotein VI), CLEC-2 (C-type lectin-like receptor), and PAR (protease-activated receptor). Altered phosphorylation of Syk (spleen tyrosine kinase) and phospholipase C γ2 and β3 accounted for these global platelet activation defects. In addition, direct activation of STIM1 (stromal interaction molecule 1) with thapsigargin revealed a defective store-operated Ca entry mechanism in the mutant platelets. These defects translated into an impaired platelet aggregate formation under flow and protection of the mice from arterial thrombosis and ischemic stroke in vivo.
Our results identify TRPM7 kinase as a key modulator of phospholipase C signaling and store-operated Ca entry in platelets. The protection of mice from acute ischemic disease without developing intracranial hemorrhage indicates that TRPM7 kinase might be a promising antithrombotic target.
TRPM7（瞬时受体电位阳离子通道，亚家族 M，成员 7）是一种广泛表达的双功能蛋白，由瞬时受体电位通道片段与细胞质α型丝氨酸/苏氨酸蛋白激酶结构域相连组成。TRPM7 形成组成型激活的 Mg 和 Ca 通透性通道，调节健康和患病状态下的多种细胞过程，但 TRPM7 激酶的生理作用在很大程度上仍不清楚。
我们在这里表明，在小鼠中突变 TRPM7 激酶结构域以消除激酶活性（）导致血小板中明显的信号缺陷。血小板显示出 PIP2（磷脂酰肌醇-4,5-二磷酸）代谢受损，并且随后对主要血小板受体 GPVI（糖蛋白 VI）、CLEC-2（C 型凝集素样受体）和 PAR（蛋白酶激活受体）的刺激反应性 Ca 动员减少。Syk（脾酪氨酸激酶）和磷脂酶 Cγ2 和β3 的磷酸化改变解释了这些整体血小板激活缺陷。此外，用 thapsigargin 直接激活 STIM1（基质相互作用分子 1）揭示了突变血小板中存在有缺陷的储存操纵的 Ca 内流机制。这些缺陷转化为在流动下血小板聚集形成受损，并且在体内保护小鼠免受动脉血栓形成和缺血性中风。
我们的结果确定 TRPM7 激酶是血小板中磷脂酶 C 信号和储存操纵的 Ca 内流的关键调节剂。没有发生颅内出血的 小鼠对急性缺血性疾病的保护表明，TRPM7 激酶可能是一种有前途的抗血栓形成靶点。
