title: Timing and expression level of protein kinase C epsilon regulate the megakaryocytic differentiation of human CD34 cells.
abstract: Protein kinase C (PKC)-mediated intracellular signaling participates in several key steps of hematopoietic cell differentiation. The epsilon isoform of PKC has been associated with erythroid differentiation as well as with the early phases of megakaryocytic (MK) lineage commitment. Here, we worked on the hypothesis that PKCepsilon expression levels might be modulated during MK differentiation, with a specific role in the early as well as in the late phases of thrombopoiesis. We demonstrate that--at variance with the erythroid lineage development--PKCepsilon is completely downmodulated in TPO-induced CD34 cells from day 6 onward. The forced expression of PKCepsilon in the late phases of MK differentiation delays the phenotypic differentiation of progenitors likely via Bcl-xL upregulation. Moreover, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), known as a negative regulator of early erythroid expansion, is not apoptogenic for thrombopoietin-induced CD34 cells, but rather accelerates their maturation. However, PKCepsilon levels negatively interfere also with the effects of TRAIL in MK differentiation. PKCepsilon can therefore be considered a signaling intermediate whose expression levels are finely tuned, with a virtually opposite kinetic, in erythroid versus megakaryocytic lineages, to adequately respond to the signaling requirements of the specific hematopoietic lineage.
authors.affiliation: Department of Anatomy, Pharmacology & Forensic Medicine, Human Anatomy Section, University of Parma, Ospedale Maggiore, Via Gramsci, 14, I-43100 Parma, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Gobbi
authors.forename: Prisco
authors.initials: P
authors.lastname: Mirandola
authors.forename: Ivonne
authors.initials: I
authors.lastname: Sponzilli
authors.forename: Cristina
authors.initials: C
authors.lastname: Micheloni
authors.forename: Chiara
authors.initials: C
authors.lastname: Malinverno
authors.forename: Lucio
authors.initials: L
authors.lastname: Cocco
authors.forename: Marco
authors.initials: M
authors.lastname: Vitale
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000502:physiology; D006410:Hematopoiesis / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008533:Megakaryocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000235:genetics* / Q000502:physiology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D013926:Thrombopoietin / Q000494:pharmacology; D013997:Time Factors; D051020:bcl-X Protein / Q000235:genetics
chemical_list: D018952:Antigens, CD34; C494811:BCL2L1 protein, human; D053221:TNF-Related Apoptosis-Inducing Ligand; D051020:bcl-X Protein; D013926:Thrombopoietin; D051744:Protein Kinase C-epsilon