Identification of tyrosine residues within the intracellular domain of the erythropoietin receptor crucial for STAT5 activation.

Abstract

FDCP‐1 cells are hematopoietic progenitor cells which require interleukin‐3 for survival and proliferation. FDCP‐1 cells stably transfected with the murine erythropoietin receptor cDNA survive and proliferate in the presence of erythropoietin. Erythropoietin induces the activation of the short forms (80 kDa) of STAT5 in the cells. Erythropoietin‐induced activation of STAT5 was strongly reduced in cells expressing mutated variants of the erythropoietin receptors in which tyrosine residues in their intracellular domain have been eliminated. We determined that the erythropoietin receptor tyrosine residues 343 and 401 are independently necessary for STAT5 activation. The amino acid sequences surrounding these two tyrosine residues are very similar. Peptides comprising either phosphorylated Tyr343 or phosphorylated Tyr401, but not their unphosphorylated counterparts, inhibited the STAT5 activation. We propose that these two tyrosine residues of the erythropoietin receptor constitute docking sites for the STAT5 SH2 domain. The growth stimulus mediated by erythropoietin was decreased in cells expressing erythropoietin receptors lacking both Tyr343 and Tyr401. This suggests that STAT5 activation could be involved in the growth control of FDCP‐1 cells.

Activation of Stat5 by platelet-derived growth factor (PDGF) is dependent on phosphorylation sites in PDGF β-receptor juxtamembrane and kinase insert domains

“…For several receptors mediating Stat5 activation, phosphorylation of speci®c tyrosine residues have been shown to be necessary for the activation of Stat5. Tyr392 and Tyr510 in the interleukin-2 receptor, Tyr409 in the interleukin-7 receptor (Friedmann et al, 1996;Lin et al, 1995), Tyr116 in the interleukin-9 receptor (Demoulin et al, 1996), Tyr382 in the Nb2 form and Tyr580 in the long form of the prolactin receptor (Lebrun et al, 1995), and Tyr343 and Tyr401 in the erythropoietin receptor (Gobert et al, 1996;Quelle et al, 1996), have been shown to be important for Stat5 activation, probably by creating binding sites for the SH2-domain of Stat5. Comparing the sequences surrounding these tyrosine residues with those surrounding Tyr579, Tyr581 and Tyr775 in the PDGF b-receptor, reveals a similarity between Tyr581 in the PDGF b-receptor (YVDP) and Tyr382/Tyr580 in the prolactin receptor (YLDP) (Lebrun et al, 1995).…”

Spi-1 transgenic mice develop a clonal erythroleukemia which does not depend on p53 mutation

“…Although in the HS1 step of the erythroleukemia developing in spi-1 transgenic mice, erythroblasts remained totally dependent upon Epo for their survival and proliferation both in vivo and in vitro, we checked whether alterations in the signaling pathway from the Epo receptor could be detected. Stat5 is a transcription factor whose activity is speci®cally induced by Epo in Epo-dependent cell lines (Gobert et al, 1996). Studies were performed with HS1 Epo-dependent cell lines derived from R33 and R83 spleens.…”

IL-3 dependent regulation of Bcl-xL gene expression by STAT5 in a bone marrow derived cell line

“…Conicting results were obtained on the role of STAT5 in the proliferation of hematopoietic cell lines. The use of cytokine receptor mutants unable to activate STAT5, or the use of dominant negative form of STAT5, indicated that STAT5 activation was required for Epo, IL-2-or IL-3-induced cell proliferation, while other studies suggested that STAT5 was not essential for this e ect (Friedmann et al, 1996;Fujii et al, 1995;Gobert et al, 1996;Mui et al, 1996;Quelle et al, 1996). Studies with dominant negative STAT5 and receptor mutants also demonstrated a role of STAT5 in erythroid di erentiation Iwatsuki et al, 1997).…”