Orai1‐induced store‐operated Ca2+ entry enhances phospholipase activity and modulates canonical transient receptor potential channel 6 function in murine platelets. (April 2014)

• Record Type: Journal Article
• Authors: Chen, W.; Thielmann, I.; Gupta, S.; Subramanian, H.; Stegner, D.; van, R.; Dietrich, A.; Gambaryan, S.; Heemskerk, J. W. M.; Hermanns, H. M.; Nieswandt, B.; Braun, A.
• Is Part Of: Journal of thrombosis and haemostasis. Volume 12:Number 4(2014:Apr.)
• Page Start: 528
• Page End: 539
• Publication Date: 2014-04
• Subjects: Thrombosis -- Periodicals; Hemostasis -- Periodicals; Blood coagulation disorders -- Periodicals; 616.1
• DOI: 10.1111/jth.12525
• Languages: English
• ISSNs: 1538-7933

Abstract

<abstract abstract-type="main" id="jth12525-abs-0001"> <title>Summary</title> <sec id="jth12525-sec-0001" sec-type="section"> <title>Background</title> <p>Orai1, the major store‐operated Ca<sup>2+</sup> entry (SOCE) channel in platelets, is not only critical for enhancing diverse signaling pathways, but may also regulate receptor‐operated Ca<sup>2+</sup> 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.</p> </sec> <sec id="jth12525-sec-0002" sec-type="section"> <title>Objective</title> <p>We aimed to elucidate the role of Orai1 in diacylglycerol (DAG)‐mediated ROCE.</p> </sec> <sec id="jth12525-sec-0003" sec-type="section"> <title>Methods</title> <p> <italic>Trpc6</italic> <sup> <italic>−/−</italic> </sup>, <italic>Orai1</italic><sup><italic>−/−</italic></sup> and <italic>Orai1</italic><sup><italic>−/−</italic></sup><italic>/Trpc6</italic><sup><italic>−/−</italic></sup> mice were generated, and their platelets were analyzed.</p> </sec> <sec id="jth12525-sec-0004" sec-type="section"> <title>Results</title> <p>Thapsigargin (TG)‐induced SOCE was further reduced in <italic>Orai1</italic><sup><italic>−/−</italic></sup>/<italic>Trpc6</italic><sup><italic>−/−</italic></sup> platelets as compared with <italic>Orai1</italic><sup><italic>−/−</italic></sup> platelets, thus revealing that TG‐induced signaling pathways can activate TRPC6. Thapsigargin‐induced SOCE leads to enhanced phospholipase C and D activity in wild‐type platelets. The activity of both enzymes was significantly reduced in <italic>Orai1</italic><sup><italic>−/−</italic></sup> platelets upon TG stimulation, whereas receptor‐induced phospholipase activity was not affected. Furthermore, TG‐induced and glycoprotein VI‐mediated thromboxane A<sub>2</sub> release was strongly dependent on Orai1‐mediated SOCE.</p> </sec> <sec id="jth12525-sec-0005" sec-type="section"> <title>Conclusion</title> <p>The 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 Ca<sup>2+</sup> signaling in platelets.</p> </sec> </abstract>