title: Differential involvement of tyrosine and serine/threonine kinases in platelet integrin alphaIIbbeta3 exposure.
abstract: The relative contributions of protein tyrosine kinases (PTKs) and protein kinase C isoenzymes (PKCs), a family of serine/threonine kinases, in integrin alpha(IIb)beta3 (glycoprotein IIb/IIIa) exposure are the subject of much controversy. In the present study we measured the effect of the PTK inhibitor herbimycin A and the PKC inhibitor bisindolylmaleimide I on 125I-fibrinogen binding to alpha(IIb)beta3 and on aggregation/secretion induced by different agonists. Dose-response studies showed complete inhibition of alpha(IIb)beta3 exposure by 30 micromol/L (ADP stimulation) and 35 to 40 micromol/L (alpha-thrombin stimulation) herbimycin A. In contrast, inhibition of exposure by bisindolylmaleimide I varied from none (for ADP and epinephrine), to 30% (for platelet-activating factor), and to approximately 80% (for alpha-thrombin). Studies with a submaximal dose of herbimycin A (approximately 50% inhibition of the ADP-response) and a maximal dose of bisindolylmaleimide I showed that optical aggregation had a similar sensitivity to the inhibitors as alpha(IIb)beta3 exposure with minimal interference by secreted ADP. Thus, the relative contributions of tyrosine and serine/threonine kinases in alpha(IIb)beta3 exposure and aggregation differ among the different agonists, with an exclusive role for PTKs in ADP- and epinephrine-induced responses and a role for both PTKs and PKCs in responses induced by platelet-activating factor and alpha-thrombin.
authors.affiliation: Department of Haematology, University Hospital Utrecht, and the Institute for Biomembranes, Utrecht University, The Netherlands.
authors.forename: I
authors.initials: I
authors.lastname: Hers
authors.forename: J
authors.initials: J
authors.lastname: Donath
authors.forename: G
authors.initials: G
authors.lastname: van Willigen
authors.forename: J W
authors.initials: JW
authors.lastname: Akkerman
mesh_terms: D001792:Blood Platelets / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005340:Fibrinogen / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011493:Protein Kinase C / Q000009:adverse effects / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000009:adverse effects / Q000502:physiology; D013928:Thromboxane A2 / Q000096:biosynthesis; D014443:Tyrosine / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D014443:Tyrosine; D013928:Thromboxane A2; D005340:Fibrinogen; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C