Platelet shape change is mediated by both calcium-dependent and -independent signaling pathways. Role of p160 Rho-associated coiled-coil-containing protein kinase in platelet shape change.
Platelets undergo shape change upon activation with agonists. During shape change, disc-shaped platelets turn into spiculated spheres with protruding filopodia. When agonist-induced cytosolic Ca(2+) increases were prevented using the cytosolic Ca(2+) chelator, 5, 5'-dimethyl-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (5, 5'-dimethyl-BAPTA), platelets still underwent shape change, although the onset was delayed and the initial rate was dramatically decreased. In the absence of cytosolic Ca(2+), agonist-stimulated myosin light chain phosphorylation was significantly inhibited. The myosin light chain was maximally phosphorylated at 2 s in control platelets compared with 30 s in 5,5'-dimethyl-BAPTA-treated platelets. ADP, thrombin, or U46619-induced Ca(2+)-independent platelet shape change was significantly reduced by staurosporine, a nonselective kinase inhibitor, by the selective p160 Rho-associated coiled-coil-containing protein kinase inhibitor Y-27632, or by HA 1077. Both Y-27632 and HA 1077 reduced peak levels of ADP-induced platelet shape change and myosin light chain phosphorylation in control platelets. In 5,5'-dimethyl-BAPTA-treated platelets, Y-27632 and HA 1077 completely abolished both ADP-induced platelet shape change and myosin light chain phosphorylation. Our results indicate that Ca(2+)/calmodulin-stimulated myosin light chain kinase and p160 Rho-associated coiled-coil-containing protein kinase independently contribute to myosin light chain phosphorylation and platelet shape change, through Ca(2+)-sensitive and Ca(2+)-insensitive pathways, respectively.
Paul
B Z
BZ
Department of Pharmacology, Temple University Medical School, Philadelphia, Pennsylvania 19140, USA.
Daniel
J L
JL
Kunapuli
S P
SP
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology*; D002118:Calcium / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009218:Myosins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D054460:rho-Associated Kinases
D000577:Amides; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C108830:Y 27632; D004533:Egtazic Acid; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C058180:5,5'-dimethyl-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009218:Myosins; C049347:fasudil; D002118:Calcium