title: Relationship between calcium mobilization and platelet α- and δ-granule secretion. A role for TRPC6 in thrombin-evoked δ-granule exocytosis.
abstract: Changes in cytosolic Ca(2+) concentration ([Ca(2+)]c) regulate granule secretion in different cell types. Thrombin activates PAR1 and PAR4 receptors and promotes release of Ca(2+) from distinct intracellular stores, which, in turn, activates store-operated Ca(2+) 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 Ca(2+) 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 Ca(2+), and in a concentration-dependent manner. Our findings show that thrombin-stimulated granule secretion depends on Ca(2+) 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 Ca(2+) mobilization.
authors.affiliation: Department of Physiology, University of Extremadura, Phycell, 10003, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Lopez
authors.affiliation: Department of Hematology, Hospital San Pedro de Alcantara, 10003 Cáceres, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Bermejo
authors.affiliation: Department of Physiology, University of Extremadura, Phycell, 10003, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Berna-Erro
authors.affiliation: Department of Hematology, Hospital Infanta Cristina, 06006 Badajoz, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Alonso
authors.affiliation: Department of Physiology, University of Extremadura, Phycell, 10003, Spain.
authors.forename: G M
authors.initials: GM
authors.lastname: Salido
authors.affiliation: Department of Physiology, University of Extremadura, Phycell, 10003, Spain.
authors.forename: P C
authors.initials: PC
authors.lastname: Redondo
authors.affiliation: Department of Physiology, University of Extremadura, Phycell, 10003, Spain. Electronic address: jarosado@unex.es.
authors.forename: J A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D057134:Antibodies, Neutralizing / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D005089:Exocytosis / Q000187:drug effects; D015870:Gene Expression; D006801:Humans; D017136:Ion Transport; D015539:Platelet Activation / Q000187:drug effects; D022142:Secretory Vesicles / Q000187:drug effects* / Q000378:metabolism; D050052:TRPC Cation Channels / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000074287:TRPC6 Cation Channel; D013917:Thrombin / Q000494:pharmacology*
chemical_list: D057134:Antibodies, Neutralizing; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; D013917:Thrombin; D002118:Calcium
keywords: Calcium; Platelets; TRPC6; Thrombin; α-granules; δ-granules