title: A role for the actin cytoskeleton in the initiation and maintenance of store-mediated calcium entry in human platelets. Evidence for conformational coupling.
abstract: The nature of the mechanism underlying store-mediated Ca(2+) entry has been investigated in human platelets through a combination of cytoskeletal modifications. Inhibition of actin polymerization by cytochalasin D or latrunculin A had a biphasic time-dependent effect on Ca(2+) entry, showing an initial potentiation followed by inhibition of Ca(2+) entry. Moreover, addition of these agents after induction of store-mediated Ca(2+) entry inhibited the Ca(2+) influx mechanism. Jasplakinolide, which reorganizes actin filaments into a tight cortical layer adjacent to the plasma membrane, prevented activation of store-mediated Ca(2+) entry but did not modify this process after its activation. In addition, jasplakinolide prevented cytochalasin D-induced inhibition of store-mediated Ca(2+) entry. Calyculin A, an inhibitor of protein serine/threonine phosphatases 1 and 2 which activates translocation of existing F-actin to the cell periphery without inducing actin polymerization, also prevented activation of store-mediated Ca(2+) entry. Finally, inhibition of vesicular transport with brefeldin A inhibited activation of store-mediated Ca(2+) entry but did not alter this mechanism once initiated. These data suggest that store-mediated Ca(2+) entry in platelets may be mediated by a reversible trafficking and coupling of the endoplasmic reticulum with the plasma membrane, which shows close parallels to the events mediating secretion.
authors.affiliation: Department of Physiology, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom.
authors.forename: J A
authors.initials: JA
authors.lastname: Rosado
authors.forename: S
authors.initials: S
authors.lastname: Jenner
authors.forename: S O
authors.initials: SO
authors.lastname: Sage
mesh_terms: D000199:Actins / Q000378:metabolism*; D001692:Biological Transport; D001792:Blood Platelets / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D047630:Depsipeptides; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008387:Marine Toxins; D008954:Models, Biological; D010080:Oxazoles / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D047630:Depsipeptides; D008387:Marine Toxins; D010080:Oxazoles; D010456:Peptides, Cyclic; D013844:Thiazoles; D053778:Thiazolidines; C057531:jasplakinolide; D020126:Brefeldin A; D015638:Cytochalasin D; C059041:calyculin A; D015544:Inositol 1,4,5-Trisphosphate; C037067:latrunculin A; D002118:Calcium