Referenced in: none

Automatically associated channels: TRP , TRPC , TRPC3 , TRPC6

Title: Transient receptor potential channels function as a coincidence signal detector mediating phosphatidylserine exposure.

Authors: Matthew T Harper, Juan E Camacho Londoño, Kathryn Quick, Julia Camacho Londoño, Veit Flockerzi, Stephan E Philipp, Lutz Birnbaumer, Marc Freichel, Alastair W Poole

Journal, date & volume: Sci Signal, 2013 Jun 25 , 6, ra50

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/23800468

Abstract
Blood platelet aggregation must be tightly controlled to promote clotting at injury sites but avoid inappropriate occlusion of blood vessels. Thrombin, which cleaves and activates Gq-coupled protease-activated receptors, and collagen-related peptide, which activates the receptor glycoprotein VI, stimulate platelets to aggregate and form thrombi. Coincident activation by these two agonists synergizes, causing the exposure of phosphatidylserine on the cell surface, which is a marker of cell death in many cell types. Phosphatidylserine exposure is also essential to produce additional thrombin on platelet surfaces, which contributes to thrombosis. We found that activation of either thrombin receptors or glycoprotein VI alone produced a calcium signal that was largely dependent only on store-operated Ca(2+) entry. In contrast, experiments with platelets from knockout mice showed that the presence of both ligands activated nonselective cation channels of the transient receptor potential C (TRPC) family, TRPC3 and TRPC6. These channels principally allowed entry of Na(+), which coupled to reverse-mode Na(+)/Ca(2+) exchange to allow calcium influx and thereby contribute to Ca(2+) signaling and phosphatidylserine exposure. Thus, TRPC channels act as coincidence detectors to coordinate responses to multiple signals in cells, thereby indirectly mediating in platelets an increase in intracellular calcium concentrations and exposure of prothrombotic phosphatidylserine.