Sekine Yuichi, Tsuji Satoshi, Ikeda Osamu, Kakisaka Michinori, Sugiyama Kenji, Yoshimura Akihiko, Matsuda Tadashi
Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Biochem Biophys Res Commun. 2007 May 4;356(2):517-22. doi: 10.1016/j.bbrc.2007.03.031. Epub 2007 Mar 12.
Signal transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein that contains Pleckstrin and Src homology 2 (SH2)-like domains as well as a YXXQ motif in its C-terminal region. Our previous studies revealed that STAP-2 binds to signal transducer and activator of transcription 3 (STAT3) and STAT5, and regulates their signaling pathways. In the present study, we identified tyrosine-250 (Tyr250) in STAP-2 as a major site of phosphorylation by v-src and Jak2, using a phospho-specific antibody against STAP-2 phosphorylated at Tyr250. Mutational analyses revealed that Tyr250 was involved in the STAT3-enhancing activity of STAP-2. We further found that leukemia inhibitory factor (LIF) stimulated STAP-2 Tyr250 phosphorylation in 293T and Hep3B cells. Moreover, endogenous STAP-2 was phosphorylated at Tyr250 following LIF stimulation of murine M1 cell line. Taken together, our findings demonstrate that endogenous STAP-2 is phosphorylated at Tyr250 and that this phosphorylation is involved in its function.
信号转导衔接蛋白2（STAP-2）是一种最近鉴定出的衔接蛋白，其在C末端区域包含普列克底物蛋白和Src同源2（SH2）样结构域以及一个YXXQ基序。我们之前的研究表明，STAP-2与信号转导子和转录激活子3（STAT3）以及STAT5结合，并调节它们的信号通路。在本研究中，我们使用针对在酪氨酸250（Tyr250）处磷酸化的STAP-2的磷酸化特异性抗体，将STAP-2中的酪氨酸250（Tyr250）鉴定为v-src和Jak2磷酸化的主要位点。突变分析表明，Tyr250参与了STAP-2的STAT3增强活性。我们进一步发现，白血病抑制因子（LIF）刺激293T和Hep3B细胞中STAP-2 Tyr250的磷酸化。此外，在对小鼠M1细胞系进行LIF刺激后，内源性STAP-2在Tyr250处被磷酸化。综上所述，我们的研究结果表明，内源性STAP-2在Tyr250处被磷酸化，并且这种磷酸化涉及其功能。
