title: PKCepsilon controls protection against TRAIL in erythroid progenitors.
abstract: Apoptosis plays a central role in the regulation of the size of the hematopoietic stem cell pool as well as in the processes of cell differentiation along the various hematopoietic lineages. TRAIL is a member of the TNF family of cytokines with a known apoptogenic role against a variety of malignant cells and an emerging role in the modulation of normal hematopoiesis. Here we worked on the hypothesis that PKCepsilon could act as a switch of the cellular response to TRAIL during erythropoiesis. We demonstrate that EPO-induced erythroid CD34 cells are insensitive to the apoptogenic effect of TRAIL at day 0 due to the lack of specific receptor expression. From day 3 onward, erythroid cells express surface death receptors and become sensitive to TRAIL up to day 7/8 when, notwithstanding death-receptor expression, the EPO-driven up-regulation of PKCepsilon intracellular levels renders differentiating erythroid cells resistant to TRAIL likely via Bcl-2 up-regulation. Our conclusion is that in human CD34 cells, EPO promotes a series of events that, being finely regulated in their kinetics, restricts the sensitivity of these cells to TRAIL to a specific period of time, which therefore represents the "TRAIL window" for the negative regulation of erythroid-cell numbers.
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: Prisco
authors.initials: P
authors.lastname: Mirandola
authors.forename: Giuliana
authors.initials: G
authors.lastname: Gobbi
authors.forename: Cristina
authors.initials: C
authors.lastname: Ponti
authors.forename: Ivonne
authors.initials: I
authors.lastname: Sponzilli
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; D000970:Antineoplastic Agents / Q000378:metabolism*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D015153:Blotting, Western; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000378:metabolism*; D004920:Erythropoiesis / Q000502:physiology*; D004921:Erythropoietin / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors / Q000235:genetics / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D018952:Antigens, CD34; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D004921:Erythropoietin; D051744:Protein Kinase C-epsilon