Dominant negative variants of the SHP-2 tyrosine phosphatase inhibit prolactin activation of Jak2 (janus kinase 2) and induction of Stat5 (signal transducer and activator of transcription 5)-dependent transcription.
PRL plays a central role in the regulation of milk protein gene expression in mammary epithelial cells and in the growth and differentiation of lymphocytes. It confers its activity through binding to a specific transmembrane, class I hematopoietic receptor. Ligand binding leads to receptor dimerization and activation of the tyrosine kinase Jak (janus kinase) 2, associated with the membrane-proximal, intracellular domain of the receptor. Jak2 phosphorylates and activates Stat5, a member of the Stat (signal transducers and activators of transcription) family. PRL receptor also activates SHP-2, a cytosolic tyrosine phosphatase. We investigated the connection between these two signaling events and derived a dominant negative mutant of SHP-2 comprising the two SH2 domains [SHP-2(SH2)2]. An analogous variant of the SHP-1 phosphatase [SHP-1(SH2)2] was used as a control. The dominant negative mutant of SHP-2 was found to inhibit the induction of tyrosine phosphorylation and DNA-binding activity of m-Stat5a, m-Stat5b, and the carboxyl-terminal deletion variant m-Stat5adelta749, as well as the transactivation potential of m-Stat5a and m-Stat5b. The dominant negative mutant SHP-1(SH2)2 had no effect. The kinase activity of Jak2 is also dependent on a functional SHP-2 phosphatase. We propose that SHP-2 relieves an inhibitory tyrosine phosphorylation event in Jak2 required for Jak2 activity, Stat5 phosphorylation, and transcriptional induction.
Berchtold
S
S
Institute for Experimental Cancer Research, Tumor Biology Center and Department of Biology, University of Freiburg, Germany.
Volarevic
S
S
Moriggl
R
R
Mercep
M
M
Groner
B
B
D000818:Animals; D019556:COS Cells; D002364:Caseins / Q000187:drug effects / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D005799:Genes, Dominant; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D019169:Jurkat Cells; D008894:Milk Proteins; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011388:Prolactin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D011981:Receptors, Prolactin / Q000378:metabolism; D050799:STAT5 Transcription Factor; D017384:Sequence Deletion; D015534:Trans-Activators / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000378:metabolism
D002364:Caseins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D011981:Receptors, Prolactin; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; C494095:STAT5B protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D014443:Tyrosine; D011388:Prolactin; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases