title: Evidence for a selective inhibitory effect of thrombin on megakaryocyte progenitor growth mediated by the thrombin receptor.
abstract: An efficient method for the culture of human megakaryocyte precursors in serum-free medium has been developed facilitating study of the effect of regulators of megakaryocyte growth and maturation without interference by serum-derived factors. We have investigated how megakaryocytes and their precursors respond to the procoagulant enzyme, thrombin. In addition to its already documented agonist effect on mature megakaryocytes, thrombin was found to have a marked inhibitory effect on the growth of megakaryocyte colonies from CD34+ bone marrow cells stimulated by IL3. This inhibitory effect, not previously reported, was selective for megakaryocytic cells. The growth of granulomonocytic and erythroid colonies was not affected. A monoclonal antibody which neutralized the effect of exogenous transforming growth factor beta (TGF beta) was unable to fully neutralize the inhibitory effect of thrombin. With the use of a synthetic peptide, corresponding to the tethered thrombin receptor ligand, and of a recombinant inactive form of thrombin, we provide direct evidence that both the inhibitory effect of thrombin on megakaryocyte proliferation and its agonist effect on mature megakaryocytes are mediated by a receptor analogous to the recently cloned platelet thrombin receptor.
authors.affiliation: CEA, Laboratoire d'Hématologie, INSERM U217, Département de Biologie Moléculaire et Structurale, Grenoble, France.
authors.forename: J L
authors.initials: JL
authors.lastname: Plantier
authors.forename: R
authors.initials: R
authors.lastname: Berthier
authors.forename: Y
authors.initials: Y
authors.lastname: Rival
authors.forename: A
authors.initials: A
authors.lastname: Schweitzer
authors.forename: M J
authors.initials: MJ
authors.lastname: Rabiet
mesh_terms: D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34; D001854:Bone Marrow Cells; D003114:Colony-Forming Units Assay; D016895:Culture Media, Serum-Free; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008533:Megakaryocytes / Q000166:cytology / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000032:analysis; D018179:Receptors, Thrombin / Q000502:physiology*; D013234:Stem Cells / Q000187:drug effects*; D013917:Thrombin / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D016895:Culture Media, Serum-Free; D010980:Platelet Membrane Glycoproteins; D018179:Receptors, Thrombin; D016212:Transforming Growth Factor beta; D013917:Thrombin