title: The urokinase-receptor (CD87) is expressed in cells of the megakaryoblastic lineage.
abstract: Megakaryocytopoiesis is governed in the bone marrow microenvironment by cellular interactions that include various adhesion receptor systems and pericellular proteolysis for proper regulation of cell motility and differentiation. In order to define the role of cell surface molecules required for these processes, we searched for protease receptors on these cells. In an in vitro system utilizing different cell lines of the megakaryoblastic lineage (MEG-01, Dami), low level surface expression of the urokinase (uPA) receptor was noted. Following stimulation with phorbolester (PMA), a 3-6 fold higher expression of uPA receptor over a period of up to 5 days could be observed by fluorescent activated cell-sorting as well as by direct ligand-binding of amino-terminal fragment of uPA or vitronectin. Together with elevated expression of alpha IIb beta 3-integrin (glycoprotein IIb/IIIa complex), double immuno-fluorescence staining of stimulated cells confirmed the increased cell surface localization of uPA receptor. Semi-quantitative RT-PCR, ligand blot analysis and measurement of cell-bound proteolytic activity revealed a differentiation-dependent upregulation of the uPA receptor expression in megakaryoblastic cell lines as in monocytic cells. Due to its glycolipid anchorage, incubation with phosphatidylinositol-specific phospholipase C reduced uPA receptor-mediated ligand binding by about 60%, uPA receptor mRNA was expressed in cultured megakaryocytes derived from bone marrow, whereas no uPA receptor mRNA was detectable in platelets. These results indicate a differentiation-dependent increase in the expression of uPA receptor in megakaryoblastic cells. The characteristics of surface expression and functionality of the receptor on megakaryocytic cells may influence their maturation by regulating cellular communication in the bone marrow micro-environment.
authors.affiliation: Haemostasis Research Unit, Kerckhoff-Klinik, MPI, Bad Nauheim, Germany.
authors.forename: K D
authors.initials: KD
authors.lastname: Wohn
authors.forename: S M
authors.initials: SM
authors.lastname: Kanse
authors.forename: V
authors.initials: V
authors.lastname: Deutsch
authors.forename: T
authors.initials: T
authors.lastname: Schmidt
authors.forename: A
authors.initials: A
authors.lastname: Eldor
authors.forename: K T
authors.initials: KT
authors.lastname: Preissner
mesh_terms: D002454:Cell Differentiation; D002460:Cell Line; D004792:Enzyme Precursors / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D006801:Humans; D008533:Megakaryocytes / Q000378:metabolism*; D010960:Plasminogen Activators / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*; D019096:Vitronectin / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; C524898:PLAUR protein, human; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D019096:Vitronectin; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate