title: The membrane potential modulates thrombin-stimulated Ca²⁺ mobilization and platelet aggregation.
abstract: G protein-coupled receptors can be directly modulated by changes in transmembrane voltage in a variety of cell types. Here we show that, while changes in the membrane voltage itself do not induce detectable modifications in the cytosolic Ca(2+) concentration, platelet stimulation with thrombin or the PAR-1 and PAR-4 agonist peptides SFLLRN and AYPGKF, respectively, results in Ca(2+) release from intracellular stores that is sensitive to the membrane depolarisation. Direct activation of G proteins or phospholipase C by AlF4(-) and m-3M3FBS, respectively, leads to Ca(2+) release that is insensitive to changes in the membrane potential. Thapsigargin-, as well as OAG-induced Ca(2+) entry are affected by the membrane voltage, probably as a result of the modification in the driving force for Ca(2+) influx; however, hyperpolarisation does not enhance thrombin- or OAG-evoked Ca(2+) entry probably revealing the presence of a voltage-sensitive regulatory mechanism. Transmembrane voltage also modulates the activity of the plasma membrane Ca(2+)-ATPase (PMCA) most likely due to a decrease in the phosphotyrosine content of the pump. Thrombin-stimulated platelet aggregation is modulated by membrane depolarisation by a mechanism that is, at least partially, independent of Ca(2+). These observations indicate that PAR-1 and PAR-4 receptors are modulated by the membrane voltage in human platelets.
authors.affiliation: Department of Physiology (Cell Physiology Research Group), University of Extremadura, 10003 Cáceres, Spain.
authors.forename: Letizia
authors.initials: L
authors.lastname: Albarrán
authors.forename: Natalia
authors.initials: N
authors.lastname: Dionisio
authors.forename: Esther
authors.initials: E
authors.lastname: López
authors.forename: Ginés M
authors.initials: GM
authors.lastname: Salido
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D006801:Humans; D008564:Membrane Potentials; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000378:metabolism; D010974:Platelet Aggregation; D044463:Receptor, PAR-1 / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism*
chemical_list: D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; D013917:Thrombin; D053499:Plasma Membrane Calcium-Transporting ATPases; C112908:protease-activated receptor 4; D002118:Calcium
keywords: Aggregation; Ca(2+) entry; Ca(2+) release; Human platelets; Membrane potential; Thrombin