2000 Fiscal Year Final Research Report Summary
Multinucleation induced by Chk overexpression in hematopoietic cells
| Project/Area Number |
11470212
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Hematology
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| Research Institution | Chiba University (2000)
University of Shizuoka (1999) |
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Principal Investigator |
YAMAGUCHI Naoto Faculty of Pharmaceutical Sciences, Professor, 薬学部, 教授 (00166620)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Cell growth / Chromosome / Csk / Multinucleation / Intracellular localization / CSk homologous kinase (Chk) / Src family tyrosine kinase / Tyrosine phosphorylation |
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| Research Abstract |
Src family protein-tyrosine kinases play crucial roles in regulating proliferation and differentiation of multiple cell types including hematopoietic cells. The activity of Src family kinases is tightly regulated by tyrosine phosphorylation and dephosphorylation events. The C-terminal src kinase (Csk), which is expressed ubiquitously, has been shown to phosphorylate the C-terminal negative regulatory tyrosine residue of Src family kinases and suppress their kinase activity. A second member of the Csk family expressed in hematopoietic cells was recently identified as the Csk homologous kinase (Chk). Like Csk, Chk suppresses the catalytic activity of Src family kinases by phosphorylating their C-terminal negative regulatory tyrosine residues. Ectopic and transient expression of Chk in COS-1 cells showed nuclear localization of Chk and growth inhibition. To further explore the role of Chk in cell growth, we overexpressed Chk in human immature myeloid KMT-2 cells. Chk overexpression brought about growth retardation and aberrant chromosome movement leading to multinucleation, and these events were accompanied by insufficient formation of mitotic spindles. In vitro kinase assays showed that Chk overexpression suppressed the tyrosine kinase activity of Lyn, a member of the Src family, immunoprecipitated from Triton X-100 lysates. Subcellular fractionation studies revealed that a fraction of Chk and Lyn, resistant to Triton X-100 solubilization, are associated with mitotic chromosome scaffolds and spindles. Chk overexpression induced a decrease in autophosphorylation of Lyn and concomitant changes in levels of tyrosine phosphorylation of proteins associated with both fractions. These results indicate that Chk, Lyn and the tyrosine-phosphorylated proteins localize to mitotic chromosomes and spindles, suggesting that Chk-dependent tyrosine phosphorylation presumably through Lyn may be involved in chromosome dynamics.
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Research Products
(12 results)
