STAP-2 is phosphorylated at tyrosine-250 by Brk and modulates Brk-mediated STAT3 activation.
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. STAP-2 is also known as breast tumor kinase (Brk) substrate (BKS). Our previous studies revealed that STAP-2 binds to signal transducer and activator of transcription 3 (STAT3) and STAT5, and regulates the signaling pathways downstream of them. In the present study, we identified tyrosine-250 (Tyr250) in STAP-2 as a major site of phosphorylation by Brk, using a series of STAP-2 YF mutants and anti-phospho-STAP-2 Tyr250 antibody. Furthermore, overexpression of the STAP-2 Y250F mutant protein affected Brk-mediated STAT3 activation. Importantly, small-interfering RNA-mediated reduction of endogenous STAP-2 expression decreased Brk-mediated STAT3 activation. Taken together, our findings demonstrate that STAP-2 is phosphorylated at Tyr250 by Brk, and plays an important role in Brk-mediated STAT3 activation.
Ikeda
Osamu
O
Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Miyasaka
Yuto
Y
Sekine
Yuichi
Y
Mizushima
Akihiro
A
Muromoto
Ryuta
R
Nanbo
Asuka
A
Yoshimura
Akihiko
A
Matsuda
Tadashi
T
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D009363:Neoplasm Proteins; D010750:Phosphoproteins; C413897:STAP2 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C088375:PTK6 protein, human