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Orai1‐induced store‐operated Ca 2+ entry enhances phospholipase activity and modulates canonical transient receptor potential channel 6 function in murine platelets
Author(s) -
Chen W.,
Thielmann I.,
Gupta S.,
Subramanian H.,
Stegner D.,
Kruchten R.,
Dietrich A.,
Gambaryan S.,
Heemskerk J. W. M.,
Hermanns H. M.,
Nieswandt B.,
Braun A.
Publication year - 2014
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.12525
Subject(s) - orai1 , trpc , trpc6 , microbiology and biotechnology , transient receptor potential channel , diacylglycerol kinase , stim1 , phospholipase c , platelet , chemistry , thapsigargin , platelet activation , phospholipase d , calcium signaling , signal transduction , receptor , biology , biochemistry , protein kinase c , intracellular , endoplasmic reticulum , immunology
Summary Background Orai1, the major store‐operated Ca 2+ entry ( SOCE ) channel in platelets, is not only critical for enhancing diverse signaling pathways, but may also regulate receptor‐operated Ca 2+ entry ( ROCE ). Dynamic coupling of the O rai1 signalosome to canonical transient receptor potential channels ( TRPC s) has been suggested as an essential step in the activation of SOCE and ROCE . However, the functional significance of the biochemical interaction between O rai and TRPC isoforms remains controversial. Objective We aimed to elucidate the role of O rai1 in diacylglycerol ( DAG )‐mediated ROCE . Methods Trpc6 −/− , Orai1 −/− and Orai1 −/− /Trpc6 −/− mice were generated, and their platelets were analyzed. Results Thapsigargin ( TG )‐induced SOCE was further reduced in Orai1 −/− / Trpc6 −/− platelets as compared with Orai1 −/− platelets, thus revealing that TG ‐induced signaling pathways can activate TRPC 6. Thapsigargin‐induced SOCE leads to enhanced phospholipase C 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 glycoprotein VI ‐mediated thromboxane A 2 release was strongly dependent on Orai1‐mediated SOCE . Conclusion The regulation of TRPC 6 activity can occur independently of the physical interaction with Orai1. TRPC 6 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 Ca 2+ signaling in platelets.