title: Differential roles of cAMP and cGMP in megakaryocyte maturation and platelet biogenesis.
abstract: The cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) regulate the activity of protein kinase A (PKA) and protein kinase G (PKG), respectively. This process helps maintain circulating platelets in a resting state. Here we studied the role of cAMP and cGMP in the regulation of megakaryocyte (MK) differentiation and platelet formation. Cultured, platelet-producing MKs were differentiated from fetal livers harvested from 13.5 days postcoital mouse embryos. MK development was accompanied by a dramatic increase in cAMP production and expression of soluble guanylate cyclase, PKG, and PKA as well as their downstream targets vasodilator-stimulated phosphoprotein (VASP) and MENA. Stimulation of prostaglandin E(1) receptor/adenylyl cyclase or soluble guanylate cyclase/PKG in cultured MKs increased VASP phosphorylation, indicating that these components share a common signaling pathway. To dissect out the role of cyclic nucleotides in MK differentiation, cAMP/PKA and cGMP/PKG signaling were alternately blocked in cultured MKs. Down-regulation of cAMP pathway effectors decreased MK numbers and ploidy. Notably, cGMP levels increased at the beginning of MK development and returned to basal levels in parallel with MK maturation. However, inhibition of cGMP pathway effectors had no effect on MK development. In addition, platelet release from mature MKs was enhanced by cGMP and inhibited by cAMP. Our data suggest that cAMP plays an important role in MK differentiation, while cAMP and cGMP have opposite effects on platelet production. Identifying the signaling pathways that underpin MK development and proplatelet formation will provide greater insights into thrombopoiesis and may potentially yield useful therapeutic targets.
authors.affiliation: Institute of Clinical Biochemistry and Pathobiochemistry, University of Würzburg, Würzburg, Germany. abegonja@rics.bwh.harvard.edu
authors.forename: Antonija Jurak
authors.initials: AJ
authors.lastname: Begonja
authors.forename: Stepan
authors.initials: S
authors.lastname: Gambaryan
authors.forename: Harald
authors.initials: H
authors.lastname: Schulze
authors.forename: Sunita
authors.initials: S
authors.lastname: Patel-Hett
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Italiano
authors.forename: John H
authors.initials: JH
authors.lastname: Hartwig
authors.forename: Ulrich
authors.initials: U
authors.lastname: Walter
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002454:Cell Differentiation; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis; D006152:Cyclic GMP / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000032:analysis; D005260:Female; D008533:Megakaryocytes / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011247:Pregnancy; D013926:Thrombopoietin / Q000502:physiology; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; C102176:Enah protein, mouse; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D013926:Thrombopoietin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP