Research Project
Grant-in-Aid for Scientific Research (C)
The murine sak gene encodes a putative serine-threonine kinase which is homologous to the members of the Plk/Polo family. Although Sak protein is presumed to be involved in cell growth mechanism, efforts have failed to demonstrate its kinase activity. Little has been, therefore, elucidated how Sak is regulated and how Sak contributes to cell proliferation. Tec is a cytoplasmic protein-tyrosine kinase(PTK) which becomes activated by the stimulation of cytokine receptors, lymphocyte surface antigens, heterotrimeric G protein-linked receptors, and integrins. To clarify the in vivo function of Tec, we have tried to isolate the second messengers of Tec by using the yeast two-hybrid screening. One of such Tec-binding proteins turned out to be Sak. In human kidney 293 cells, Sak became tyrosine-phosphorylated by Tec, and the serine-threonine kinase activity of Sak was detected only under the presence of Tec, suggesting Sak to be an effector molecule of Tec. In addition, Tec activity efficiently protects Sak from the "PEST" sequence-dependent proteolysis. Internal deletion of the PEST sequences led to the stabilization of Sak proteins, and expression of these mutants acted suppressive to cell growth. Our data collectively supports a novel role of Sak acting in the PTK-mediated signaling pathway.
All 2005 2004 Other
All Journal Article (15 results) Publications (6 results)
J Biol Chem. 280
Pages: 12621-12629
J Biol Chem (Epub 12005 Jan 12621) 280
Cancer Biol Ther. 3
Pages: 96-101
Genes Cells 9
Pages: 1167-1174
Exp Hematol. 32
Pages: 828-835
Blood. 103
Pages: 2973-2980
Leukemia 18
Pages: 556-565
Cancer Biol Ther (Epub 2004 Jan 2029) 3
Exp Hematol 32
Blood (Epub 2003 Dec 2930) 103
Blood 103