Defective diacylglycerol-induced Ca2+entry but normal agonist-induced activation responses in TRPC6-deficient mouse platelets

. Background: Platelet adhesion, activation and aggregation at sites of vascular injury are essential processes for primary hemostasis. Elevation of the intracellular Ca2+ concentration is a central event in platelet activation but the underlying mechanisms are not fully understood. Store-operated calcium entry (SOCE) through Orai1 was shown to be the main Ca2+ influx pathway in murine platelets, but there are additional non-store-operated Ca2+ (non-SOC) and receptor operated Ca2+ (ROC) channels expressed in the platelet plasma membrane.Objective: Canonical transient receptor potential (TRPC) channel 6 is found both in human and murine platelets and has been proposed to mediate diacylglycerol (DAG) activated ROCE but also a role in the regulation of SOCE has been suggested.Methods: To investigate the function of TRPC6 in platelet Ca2+ signaling and activation, we analyzed platelets from mice deficient in TRPC6 using a wide range of in vitro and in vivo assays.Results: In the mutant platelets, DAG activated Ca2+ influx was found to be abolished. However, this did not significantly affect SOCE or agonist induced Ca2+ responses. Platelet function in vitro and in vivo was also unaltered in the absence of TRPC6.Conclusion: Our results indicate that DAG activated ROCE is mediated exclusively by TRPC6 in murine platelets, but this Ca2+ influx has no major functional relevance for hemostasis and thrombosis. Further, in contrast to previous suggestions, based on studies with human platelets, TRPC6 appears to play an insignificant role in the regulation of SOCE in murine platelets.