Relationship between calcium mobilization and platelet α- and δ-granule secretion. A role for TRPC6 in thrombin-evoked δ-granule exocytosis

• Published in: Archives of biochemistry and biophysics 2015-11, Vol.585, p.75-81
• Main Authors: Lopez, E., Bermejo, N., Berna-Erro, A., Alonso, N., Salido, G.M., Redondo, P.C., Rosado, J.A.
• Format: Article
• Language: English
• Subjects: Antibodies, Neutralizing - pharmacology; Blood Platelets - cytology; Blood Platelets - drug effects; Blood Platelets - metabolism; Calcium; Calcium - metabolism; Calcium Signaling; Exocytosis - drug effects; Gene Expression; Humans; Ion Transport; Platelet Activation - drug effects; Platelets; Secretory Vesicles - drug effects; Secretory Vesicles - metabolism; Thrombin; Thrombin - pharmacology; TRPC Cation Channels - antagonists & inhibitors; TRPC Cation Channels - genetics; TRPC Cation Channels - metabolism; TRPC6; TRPC6 Cation Channel; α-granules; δ-granules
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2015.09.012

Changes in cytosolic Ca2+ concentration ([Ca2+]c) regulate granule secretion in different cell types. Thrombin activates PAR1 and PAR4 receptors and promotes release of Ca2+ from distinct intracellular stores, which, in turn, activates store-operated Ca2+ entry (SOCE). A crucial step during platelet function is the release of physiological agonists stored in secretory granules to the extracellular compartment during activation. We aim to study the role of Ca2+ mobilization from the extracellular compartment or from different intracellular stores in platelet granule secretion. By using flow cytometry, we have found that α- and δ-granules are secreted in thrombin-stimulated platelets in the absence of extracellular Ca2+, and in a concentration-dependent manner. Our findings show that thrombin-stimulated granule secretion depends on Ca2+ mobilization from intracellular stores. Analysis of the kinetics of granule secretion reveals that platelet stimulation with thrombin results in rapid release of α-granules which precedes the secretion of δ-granules. Incubation of platelets with a specific antibody, which recognizes the extracellular amino acid sequence 573–586 of TRPC6, inhibited thrombin-evoked δ-granule exocytosis. Our results indicate that the mechanisms underlying thrombin-induced α- and δ-granule secretion show differences in dependency on Ca2+ mobilization. •Activated platelets degranulate to release agents important for primary haemostasis.•Intracellular Ca2+ mobilization is essential for α- and δ-granule secretion.•α-granule secretion occurs rapidly upon platelets stimulation with thrombin.•Exogenous Ca2+ entry is necessary for the exocytosis of δ-granule but not α-granules.•Canonical transient receptor potential-6 (TRPC6) function is important for δ-granule secretion.