Multiple tyrosine residues in the cytosolic domain of the erythropoietin receptor promote activation of STAT5.
Signaling through the erythropoietin receptor (EPO-R) is crucial for proliferation, differentiation, and survival of erythroid progenitor cells. EPO induces homodimerization of the EPO-R, triggering activation of the receptor-associated kinase JAK2 and activation of STAT5. By mutating the eight tyrosine residues in the cytosolic domain of the EPO-R, we show that either Y343 or Y401 is sufficient to mediate maximal activation of STAT5; tyrosine residues Y429 and Y431 can partially activate STAT5. Comparison of the sequences surrounding these tyrosines reveals YXXL as the probable motif specifying recruitment of STAT5 to the EPO-R. Expression of a mutant EPO-R lacking all eight tyrosine residues in the cytosolic domain supported a low but detectable level of EPO-induced STAT5 activation, indicating the existence of an alternative pathway for STAT5 activation independent of any tyrosine in the EPO-R. The kinetics of STAT5 activation and inactivation were the same, regardless of which tyrosine residue in the EPO-R mediated its activation or whether the alternative pathway was used. The ability of mutant EPO-Rs to activate STAT5 did not directly correlate with their mitogenic potential.
Klingmüller
U
U
Whitehead Institute for Biomedical Research, Nine Cambridge Center, MA 02142, USA.
Bergelson
S
S
Hsiao
J G
JG
Lodish
H F
HF
D000595:Amino Acid Sequence; D001483:Base Sequence; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D008894:Milk Proteins; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000737:chemistry; D019000:Phosphotyrosine / Q000737:chemistry; D017354:Point Mutation; D011485:Protein Binding; D017467:Receptors, Erythropoietin / Q000737:chemistry / Q000378:metabolism*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry; D018909:src Homology Domains
D004268:DNA-Binding Proteins; D008894:Milk Proteins; D015345:Oligonucleotide Probes; D017467:Receptors, Erythropoietin; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D019000:Phosphotyrosine; D014443:Tyrosine