Expression of a functional N-methyl-D-aspartate-type glutamate receptor bybone marrow megakaryocytes

Better understanding of hemostasis will be possible by the identification o f new lineage-specific stimuli that regulate platelet formation. We describ e a novel functional megakaryocyte receptor that belongs to a family of ion otropic glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype resp onsible for synaptic neurotransmission in the central nervous system (CNS). Northern blotting and reverse-transcriptase polymerase chain reaction (RT- PCR) studies identified expression of NMDAR1 and NMDAR2D type subunit mRNA in rat marrow, human megakaryocytes, and MEG-01 clonal megakaryoblastic cel ls. Immunohistochemistry and in vivo autoradiographic binding of the NMDA r eceptor-specific antagonist MK-801 confirmed that megakaryocytes expressed open channel-forming NMDA receptors in vivo, Western blots indicated that m egakaryocyte NMDAR1 was either unglycosylated or only glycosylated to low l evels, and of identical size to CNS-type NMDAR1 after deglycosylation with endoglycosidase F/peptide-N-glycosidase F, In functional studies, we demons trated that NMDA receptor activity was necessary for phorbol myristate acet ate (PMA)-induced differentiation of megakaryoblastic cells; NMDA receptor blockade by specific antagonists significantly inhibited PMA-mediated incre ases in cell size, CD41 expression, and adhesion of MEG-01 cells, These res ults provide evidence for a novel pathway by which megakaryocytopoiesis and platelet production may be regulated, (C) 1999 by The American Society of Hematology.