Objective Machado-Joseph disease （MJD）/Spinocerebellar ataxia type 3 （SCA3） is an autosomal dominant neurodegenerative disorder caused by an expansion of polyglutamine tract near the C-terminus of the MJD1 gene pr...Objective Machado-Joseph disease （MJD）/Spinocerebellar ataxia type 3 （SCA3） is an autosomal dominant neurodegenerative disorder caused by an expansion of polyglutamine tract near the C-terminus of the MJD1 gene product, ataxin-3. The precise mechanism of the MJD/SCA3 pathogenesis remains unclear. A growing body of evidence demonstrates that phosphorylation plays an important role in the pathogenesis of many neurodegenerative diseases. However, few kinases are known to phosphorylate ataxin-3. The present study is to explore whether ataxin-3 is a substrate of casein kinase 2 （CK2）. Methods The interaction between ataxin-3 and CK2 was identified by glutathione S-transferase （GST） pull-down assay and co-immunoprecipition assay. The phosphorylation of ataxin-3 by CK2 was measured by in vitro phosphorylation assays. Results （1） Both wild type and expanded ataxin-3 interacted with CK2α and CK2β in vitro. （2） In 293 cells, both wild type and expanded ataxin-3 interacted with CK2β, but not CK2α. （3） CK2 phosphorylated wild type and expanded ataxin-3. Conclusion Ataxin-3 is a substrate of protein kinase CK2.展开更多
ErbB2, a member of the receptor tyrosine kinase family, is frequently over-expressed in breast cancer. Proteolysis ofthe extracellular domain of ErbB2 results in constitutive activation of ErbB2 kinase. Recent study r...ErbB2, a member of the receptor tyrosine kinase family, is frequently over-expressed in breast cancer. Proteolysis ofthe extracellular domain of ErbB2 results in constitutive activation of ErbB2 kinase. Recent study reported that ErbB2is found in the nucleus. Here, we showed that ErbB2 is imported into the nucleus through a nuclear localization signal(NLS)-mediated mechanism. The NLS sequence KRRQQKIRKYTMRR (aa655-668) contains three clusters of basicamino acids and it is sufficient to target GFP into the nucleus. However, mutation in any basic amino acid cluster of thisNLS sequence significantly affects its nuclear localization. Furthermore, it was found that this NLS is essential for thenuclear localization of ErbB2 since the intracellular domain of Erb2 lacking NLS completely abrogates its nucleartranslocation. Taken together, our study identified a novel nuclear localization signal and reveals a novel mechanismunderlying ErbB2 nuclear trafficking and localization.展开更多
基金the National Natural Sciences Foundation of China (No. 30770664)a grant from Educational Committee of Anhui Province, China (No. ZD2008008-2).
文摘Objective Machado-Joseph disease （MJD）/Spinocerebellar ataxia type 3 （SCA3） is an autosomal dominant neurodegenerative disorder caused by an expansion of polyglutamine tract near the C-terminus of the MJD1 gene product, ataxin-3. The precise mechanism of the MJD/SCA3 pathogenesis remains unclear. A growing body of evidence demonstrates that phosphorylation plays an important role in the pathogenesis of many neurodegenerative diseases. However, few kinases are known to phosphorylate ataxin-3. The present study is to explore whether ataxin-3 is a substrate of casein kinase 2 （CK2）. Methods The interaction between ataxin-3 and CK2 was identified by glutathione S-transferase （GST） pull-down assay and co-immunoprecipition assay. The phosphorylation of ataxin-3 by CK2 was measured by in vitro phosphorylation assays. Results （1） Both wild type and expanded ataxin-3 interacted with CK2α and CK2β in vitro. （2） In 293 cells, both wild type and expanded ataxin-3 interacted with CK2β, but not CK2α. （3） CK2 phosphorylated wild type and expanded ataxin-3. Conclusion Ataxin-3 is a substrate of protein kinase CK2.
基金This work was supported by Hi-Tech Research and Development Program of China(2004AA215260).
文摘ErbB2, a member of the receptor tyrosine kinase family, is frequently over-expressed in breast cancer. Proteolysis ofthe extracellular domain of ErbB2 results in constitutive activation of ErbB2 kinase. Recent study reported that ErbB2is found in the nucleus. Here, we showed that ErbB2 is imported into the nucleus through a nuclear localization signal(NLS)-mediated mechanism. The NLS sequence KRRQQKIRKYTMRR (aa655-668) contains three clusters of basicamino acids and it is sufficient to target GFP into the nucleus. However, mutation in any basic amino acid cluster of thisNLS sequence significantly affects its nuclear localization. Furthermore, it was found that this NLS is essential for thenuclear localization of ErbB2 since the intracellular domain of Erb2 lacking NLS completely abrogates its nucleartranslocation. Taken together, our study identified a novel nuclear localization signal and reveals a novel mechanismunderlying ErbB2 nuclear trafficking and localization.
