Erythropoietin induces activation of Stat5 through association with specific tyrosines on the receptor that are not required for a mitogenic response.
The cytoplasmic domain of the erythropoietin receptor (EpoR) contains a membrane-distal region that is dispensable for mitogenesis but is required for the recruitment and tyrosine phosphorylation of a variety of signaling proteins. The membrane-proximal region of 96 amino acids is necessary and sufficient for mitogenesis as well as Jak2 activation, induction of c-fos, c-myc, cis, the T-cell receptor gamma locus (TCR-gamma), and c-pim-1. The studies presented here demonstrate that this region is also necessary and sufficient for the activation of Stat5A and Stat5B. The membrane-proximal domain contains a single tyrosine, Y-343, which when mutated eliminates the ability of the receptor to couple Epo binding to the activation of Stat5. Furthermore, peptide competitions demonstrate that this site, when phosphorylated, can disrupt Stat5 DNA binding activity, consistent with a role of Y-343 as a site of recruitment to the receptor. Cells expressing the truncated, Y343F mutant (a mutant with a Y-to-F alteration at position 343) proliferate in response to Epo in a manner comparable to that of the controls. However, in these cells, Epo stimulation does not induce the appearance of transcripts for cis, TCR-gamma, or c-fos, suggesting a role for Stat5 in their regulation.
Quelle
F W
FW
Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Wang
D
D
Nosaka
T
T
Thierfelder
W E
WE
Stravopodis
D
D
Weinstein
Y
Y
Ihle
J N
JN
D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000235:genetics*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004921:Erythropoietin / Q000494:pharmacology*; D006801:Humans; D053614:Janus Kinase 2; D008894:Milk Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000378:metabolism*
D004268:DNA-Binding Proteins; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D016692:Receptors, Antigen, T-Cell, gamma-delta; D017467:Receptors, Erythropoietin; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; C494095:STAT5B protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D004921:Erythropoietin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2