title: Hsp70 regulates erythropoiesis by preventing caspase-3-mediated cleavage of GATA-1.
abstract: Caspase-3 is activated during both terminal differentiation and erythropoietin-starvation-induced apoptosis of human erythroid precursors. The transcription factor GATA-1, which performs an essential function in erythroid differentiation by positively regulating promoters of erythroid and anti-apoptotic genes, is cleaved by caspases in erythroid precursors undergoing cell death upon erythropoietin starvation or engagement of the death receptor Fas. In contrast, by an unknown mechanism, GATA-1 remains uncleaved when these cells undergo terminal differentiation upon stimulation with Epo. Here we show that during differentiation, but not during apoptosis, the chaperone protein Hsp70 protects GATA-1 from caspase-mediated proteolysis. At the onset of caspase activation, Hsp70 co-localizes and interacts with GATA-1 in the nucleus of erythroid precursors undergoing terminal differentiation. In contrast, erythropoietin starvation induces the nuclear export of Hsp70 and the cleavage of GATA-1. In an in vitro assay, Hsp70 protects GATA-1 from caspase-3-mediated proteolysis through its peptide-binding domain. The use of RNA-mediated interference to decrease the Hsp70 content of erythroid precursors cultured in the presence of erythropoietin leads to GATA-1 cleavage, a decrease in haemoglobin content, downregulation of the expression of the anti-apoptotic protein Bcl-X(L), and cell death by apoptosis. These effects are abrogated by the transduction of a caspase-resistant GATA-1 mutant. Thus, in erythroid precursors undergoing terminal differentiation, Hsp70 prevents active caspase-3 from cleaving GATA-1 and inducing apoptosis.
authors.affiliation: CNRS UMR 8147, Faculté de Médecine et Université René Descartes Paris V, Institut Fédérative Necker, 75270 Paris, France.
authors.forename: Jean-Antoine
authors.initials: JA
authors.lastname: Ribeil
authors.forename: Yael
authors.initials: Y
authors.lastname: Zermati
authors.forename: Julie
authors.initials: J
authors.lastname: Vandekerckhove
authors.forename: Severine
authors.initials: S
authors.lastname: Cathelin
authors.forename: Joelle
authors.initials: J
authors.lastname: Kersual
authors.forename: Michaël
authors.initials: M
authors.lastname: Dussiot
authors.forename: Séverine
authors.initials: S
authors.lastname: Coulon
authors.forename: Ivan Cruz
authors.initials: IC
authors.lastname: Moura
authors.forename: Ann
authors.initials: A
authors.lastname: Zeuner
authors.forename: Thomas
authors.initials: T
authors.lastname: Kirkegaard-Sørensen
authors.forename: Bruno
authors.initials: B
authors.lastname: Varet
authors.forename: Eric
authors.initials: E
authors.lastname: Solary
authors.forename: Carmen
authors.initials: C
authors.lastname: Garrido
authors.forename: Olivier
authors.initials: O
authors.lastname: Hermine
mesh_terms: D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004900:Erythroblasts / Q000166:cytology / Q000378:metabolism; D004920:Erythropoiesis; D004921:Erythropoietin / Q000172:deficiency / Q000378:metabolism; D050982:GATA1 Transcription Factor / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding
chemical_list: D050982:GATA1 Transcription Factor; D018840:HSP70 Heat-Shock Proteins; D004921:Erythropoietin; D053148:Caspase 3