EPO receptor circuits for primary erythroblast survival.
EPO functions primarily as an erythroblast survival factor, and its antiapoptotic actions have been proposed to involve predominantly PI3-kinase and BCL-X pathways. Presently, the nature of EPO-regulated survival genes has been investigated through transcriptome analyses of highly responsive, primary bone marrow erythroblasts. Two proapoptotic factors, Bim and FoxO3a, were rapidly repressed not only via the wild-type EPOR, but also by PY-deficient knocked-in EPOR alleles. In parallel, Pim1 and Pim3 kinases and Irs2 were induced. For this survival gene set, induction failed via a PY-null EPOR-HM allele, but was restored upon reconstitution of a PY343 STAT5-binding site within a related EPOR-H allele. Notably, EPOR-HM supports erythropoiesis at steady state but not during anemia, while EPOR-H exhibits near wild-type EPOR activities. EPOR-H and the wild-type EPOR (but not EPOR-HM) also markedly stimulated the expression of Trb3 pseudokinase, and intracellular serpin, Serpina-3G. For SERPINA-3G and TRB3, ectopic expression in EPO-dependent progenitors furthermore significantly inhibited apoptosis due to cytokine withdrawal. BCL-XL and BCL2 also were studied, but in highly responsive Kit(pos)CD71(high)Ter119(neg) erythroblasts, neither was EPO modulated. EPOR survival circuits therefore include the repression of Bim plus FoxO3a, and EPOR/PY343/STAT5-dependent stimulation of Pim1, Pim3, Irs2 plus Serpina-3G, and Trb3 as new antiapoptotic effectors.
Sathyanarayana
Pradeep
P
Stem and Progenitor Cell Biology Program, Molecular Medicine Division, Maine Medical Center Research Institute, Scarborough, ME 04074, USA.
Dev
Arvind
A
Fang
Jing
J
Houde
Estelle
E
Bogacheva
Olga
O
Bogachev
Oleg
O
Menon
Madhu
M
Browne
Sarah
S
Pradeep
Anamika
A
Emerson
Christine
C
Wojchowski
Don M
DM
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002470:Cell Survival; D004900:Erythroblasts / Q000502:physiology*; D005434:Flow Cytometry; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D017467:Receptors, Erythropoietin / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017467:Receptors, Erythropoietin