title: Thrombin-induced activation of RhoA in platelet shape change.
abstract: Thrombin-induced activation of RhoA and its involvement in the regulation of myosin II light chain(20) phosphorylation (MLC-P) in alpha-toxin permeabilized platelets was investigated. Permeabilized platelets, expressing normal levels of P-selectin, displayed a Ca(2+)-dependent increase in shape change and MLC-P. Thrombin activated RhoA as measured by a rhotekin-binding assay within 30 s of stimulation under conditions of constant [Ca(2+)](i). Under the same conditions and timecourse, thrombin or GTPgammaS induced an increase in MLC-P and platelet shape change which was not dependent on an increase in [Ca(2+)](i). The thrombin- and GTPgammaS-induced MLC-P in constant [Ca(2+)](i) was inhibited by the addition of Y27632, a Rho-kinase inhibitor. This study directly demonstrates that thrombin can activate RhoA in platelets in a timecourse compatible with a role in increasing MLC-P and shape change (not involving an increase in [Ca(2+)](i)). This is also Rho-kinase-dependent.
authors.affiliation: Department of Biomedical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: S L
authors.initials: SL
authors.lastname: Bodie
authors.forename: I
authors.initials: I
authors.lastname: Ford
authors.forename: M
authors.initials: M
authors.lastname: Greaves
authors.forename: G F
authors.initials: GF
authors.lastname: Nixon
mesh_terms: D000577:Amides / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability; D048429:Cell Size / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D018994:Myosin Light Chains / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D018994:Myosin Light Chains; D011725:Pyridines; C108830:Y 27632; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013917:Thrombin; D009218:Myosins; D020742:rhoA GTP-Binding Protein; D002118:Calcium