the alternative splice variant of protein tyrosine kinase 6 negatively regulates growth and enhances ptk6-mediated inhibition of β-catenin选择拼接变异的蛋白质酪氨酸激酶6负调节生长和提高ptk6-mediatedβ-catenin的抑制.pdf

The Alternative Splice Variant of Protein Tyrosine Kinase 6 Negatively Regulates Growth and Enhances PTK6- Mediated Inhibition of b-Catenin 1 1 1 1 2 Patrick M. Brauer , Yu Zheng , Mark D. Evans , Carmen Dominguez-Brauer , Donna M. Peehl , Angela L. Tyner1* 1 Department of Biochemistry and Molecular Genetics, University of Illinois College of Medicine, Chicago, Illinois, United States of America, 2 Department of Urology, Stanford University School of Medicine, Stanford, California, United States of America Abstract Protein tyrosine kinase 6 (PTK6), also called breast tumor kinase (BRK), is expressed in epithelial cells of various tissues including the prostate. Previously it was shown that PTK6 is localized to epithelial cell nuclei in normal prostate, but becomes cytoplasmic in human prostate tumors. PTK6 is also primarily cytoplasmic in the PC3 prostate adenocarcinoma cell line. Sequencing revealed expression of wild type full-length PTK6 transcripts in addition to an alternative transcript lacking exon 2 in PC3 cells. The alternative transcript encodes a 134 amino acid protein, referred to here as ALT-PTK6, which shares the first 77 amino acid residues including the SH3 domain with full length PTK6. RT-PCR was used to show that ALT-PTK6 is coexpressed with full length PTK6 in established human prostate and colon cell lines, as well as in primary cell lines derived from human prostate tissue and tumors. Although interaction between full-length PTK6 and ALT-PTK6 was not detected, ALT-PTK6 associates with the known PTK6 substrates Sam68 and b-catenin in GST pull-down assays. Coexpression of PTK6 and ALT-PTK6 led to suppression of PTK6 activity and reduced association of PTK6 with tyrosine phosphorylated proteins.