title: Phosphorylation of Y372 is critical for Jak2 tyrosine kinase activation.
abstract: Jak2 tyrosine kinase plays an important role in cytokine mediated signal transduction. There are 49 tyrosine residues in Jak2 and phosphorylation of some of these are known to play important roles in the regulation of Jak2 kinase activity. Here, using mass spectrometry, we identified tyrosine residues Y372 and Y373 as novel sites of Jak2 phosphorylation. Mutation of Y372 to F (Y372F) significantly inhibited Jak2 phosphorylation, including that of Y1007, whereas the Jak2-Y373F mutant displayed only modest reduction in phosphorylation. Relative to Jak2-WT, the ability of Jak2-Y372F to bind to and phosphorylate STAT1 was decreased, resulting in reduced Jak2-mediated downstream gene transcription. While the Y372F mutation had no effect on receptor-independent, hydrogen peroxide-mediated Jak2 activation, it impaired interferon-gamma (IFNγ) and epidermal growth factor (EGF)-dependent Jak2 activation. Interestingly however, the Y372F mutant exhibited normal receptor binding properties. Finally, co-expression of SH2-Bβ only partially restored the activation of the Jak2-Y372F mutant suggesting that the mechanism whereby phosphorylation of Y372 is important for Jak2 activation is via dimerization. As such, our results indicate that Y372 plays a critical yet differential role in Jak2 activation and function via a mechanism involving Jak2 dimerization and stabilization of the active conformation.
authors: Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32610, USA.
authors: Jacqueline
authors: J
authors: Sayyah
authors: Kavitha
authors: K
authors: Gnanasambandan
authors: Sushama
authors: S
authors: Kamarajugadda
authors: Shigeharu
authors: S
authors: Tsuda
authors: Jennifer
authors: J
authors: Caldwell-Busby
authors: Peter P
authors: PP
authors: Sayeski
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D019281:Dimerization; D004789:Enzyme Activation / Q000187:drug effects* / Q000235:genetics; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005786:Gene Expression Regulation; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D053614:Janus Kinase 2 / Q000737:chemistry / Q000172:deficiency / Q000235:genetics; D013058:Mass Spectrometry; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism*; D014616:Vaccinia virus
chemical_list: D050794:STAT1 Transcription Factor; D014443:Tyrosine; D004815:Epidermal Growth Factor; D007371:Interferon-gamma; D006861:Hydrogen Peroxide; D053614:Janus Kinase 2