A role for the actin cytoskeleton in the initiation and maintenance of store-mediated calcium entry in human platelets. Evidence for conformational coupling

• Published in: The Journal of biological chemistry 2000-03, Vol.275 (11), p.7527-7533
• Main Authors: Rosado, J A, Jenner, S, Sage, S O
• Format: Article
• Language: English
• Subjects: Actins - metabolism; Biological Transport; Blood Platelets - metabolism; Brefeldin A - pharmacology; Bridged Bicyclo Compounds, Heterocyclic - pharmacology; Calcium - metabolism; Cell Membrane - metabolism; Cytochalasin D - pharmacology; Cytoskeleton - metabolism; Depsipeptides; Endoplasmic Reticulum - metabolism; Humans; Inositol 1,4,5-Trisphosphate - metabolism; Marine Toxins; Models, Biological; Oxazoles - pharmacology; Peptides, Cyclic - pharmacology; Thiazoles - pharmacology; Thiazolidines
• ISSN: 0021-9258
• DOI: 10.1074/jbc.275.11.7527

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.