title: GPIb-dependent platelet activation is dependent on Src kinases but not MAP kinase or cGMP-dependent kinase.
abstract: Glycoprotein Ib-IX-V (GPIb-IX-V) mediates platelet tethering to von Willebrand factor (VWF), recruiting platelets into the thrombus, and activates integrin alphaIIbbeta3 through a pathway that is dependent on Src kinases. In addition, recent reports indicate that activation of alphaIIbbeta3 by VWF is dependent on protein kinase G (PKG) and mitogen-activated protein (MAP) kinases. The present study compares the importance of these signaling pathways in the activation of alphaIIbbeta3 by GPIb-IX-V. In contrast to a recent report, VWF did not promote an increase in cyclic guanosine monophosphate (cGMP), while agents that elevate cGMP, such as the nitrous oxide (NO) donor glyco-SNAP-1 (N-(beta-D-glucopyranosyl)-N2-acetyl-S-nitroso-D,L-penicillaminamide) or the type 5 phosphosdiesterase inhibitor, sildenafil, inhibited rather than promoted activation of alphaIIbbeta3 by GPIb-IX-V and blocked aggregate formation on collagen at an intermediate rate of shear (800 s(-1)). Additionally, sildenafil increased blood flow in a rabbit model of thrombus formation in vivo. A novel inhibitor of the MAP kinase pathway, which is active in plasma, PD184161, had no effect on aggregate formation on collagen under flow conditions, whereas a novel inhibitor of Src kinases, which is also active in plasma, PD173952, blocked this response. These results demonstrate a critical role for Src kinases but not MAP kinases in VWF-dependent platelet activation and demonstrate an inhibitory role for cGMP-elevating agents in regulating this process.
authors.affiliation: Department of Pharmacology, University of Oxford, UK.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Marshall
authors.forename: Yotis A
authors.initials: YA
authors.lastname: Senis
authors.forename: Jocelyn M
authors.initials: JM
authors.lastname: Auger
authors.forename: Robert
authors.initials: R
authors.lastname: Feil
authors.forename: Franz
authors.initials: F
authors.lastname: Hofmann
authors.forename: Gary
authors.initials: G
authors.lastname: Salmon
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Peterson
authors.forename: Frank
authors.initials: F
authors.lastname: Burslem
authors.forename: Steve P
authors.initials: SP
authors.lastname: Watson
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D006152:Cyclic GMP / Q000097:blood; D017869:Cyclic GMP-Dependent Protein Kinases / Q000097:blood* / Q000172:deficiency / Q000235:genetics; D006801:Humans; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000097:blood*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D015539:Platelet Activation / Q000502:physiology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000502:physiology*; D010980:Platelet Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell / Q000097:blood; D014841:von Willebrand Factor / Q000494:pharmacology
chemical_list: D020030:Nitric Oxide Donors; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell; C032193:glycoprotein receptor GPIb-IX; D014841:von Willebrand Factor; D017869:Cyclic GMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D006152:Cyclic GMP