Role of the ERK pathway in the activation of store-mediated calcium entry in human platelets.
Extracellular signal-regulated kinases (ERKs), are common participants in a broad variety of signal transduction pathways. Several studies have demonstrated the presence of ERKs in human platelets and their activation by the physiological agonist thrombin. Here we report the involvement of the ERK cascade in store-mediated Ca(2+) entry in human platelets. Treatment of dimethyl-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid-loaded platelets with thapsigargin to deplete the intracellular Ca(2+) stores resulted in a time- and concentration-dependent activation of ERK1 and ERK2. Incubation with either U0126 or PD 184352, specific inhibitors of mitogen-activated protein kinase kinase (MEK), prevented thapsigargin-induced ERK activation. Furthermore, U0126 and PD 184352 reduced Ca(2+) entry stimulated by thapsigargin or thrombin, in a concentration-dependent manner. The role of ERK in store-mediated Ca(2+) entry was found to be independent of phosphatidylinositol 3- and 4-kinases, the tyrosine kinase pathway, and actin polymerization but sensitive to treatment with inhibitors of Ras, suggesting that the ERK pathway might be a downstream effector of Ras in mediating store-mediated Ca(2+) entry in human platelets. In addition, we have found that store depletion stimulated ERK activation does not require PKC activity. This study demonstrates for the first time a novel mechanism for regulation of store-mediated Ca(2+) entry in human platelets involving the ERK cascade.
Department of Physiology, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom.
J A
JA
Rosado
S O
SO
Sage
D000199:Actins / Q000097:blood; D001549:Benzamides / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002070:Butadienes / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D015638:Cytochalasin D / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005204:Farnesol / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000097:blood; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000097:blood*; D009570:Nitriles / Q000494:pharmacology; D015539:Platelet Activation; D019284:Thapsigargin / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D000199:Actins; D001549:Benzamides; D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; C113580:U 0126; C112353:farnesylthioacetic acid; D015638:Cytochalasin D; D005204:Farnesol; D019284:Thapsigargin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D013917:Thrombin; D002118:Calcium