PMID- 10022129 OWN - NLM STAT- MEDLINE DCOM- 19990302 LR - 20161124 IS - 0950-9232 (Print) IS - 0950-9232 (Linking) VI - 18 IP - 5 DP - 1999 Feb 4 TI - Activation of Src in human breast tumor cell lines: elevated levels of phosphotyrosine phosphatase activity that preferentially recognizes the Src carboxy terminal negative regulatory tyrosine 530. PG - 1227-37 AB - Elevated levels of Src kinase activity have been reported in a number of human cancers, including colon and breast cancer. We have analysed four human breast tumor cell lines that exhibit high levels of Src kinase activity, and have determined that these cell lines also exhibit a high level of a phosphotyrosine phosphatase activity that recognizes the Src carboxy-terminal P-Tyr530 negative regulatory site. Total Src kinase activity in these cell lines is elevated as much as 30-fold over activity in normal control cells and specific activity is elevated as much as 5.6-fold. When the breast tumor cells were grown in the presence of the tyrosine phosphatase inhibitor vanadate, Src kinase activity was reduced in all four breast tumor cell lines, suggesting that Src was being activated by a phosphatase which could recognize the Tyr530 negative regulatory site. In fractionated cell extracts from the breast tumor cells, we found elevated levels of a membrane associated tyrosine phosphatase activity that preferentially dephosphorylated a Src family carboxy-terminal phosphopeptide containing the regulatory tyrosine 530 site. Src was hypophosphorylated in vivo at tyrosine 530 in at least two of the tumor cell lines, further suggesting that Src was being activated by a phosphatase in these cells. In preliminary immunoprecipitation and antibody depletion experiments, we were unable to correlate the major portion of this phosphatase activity with several known phosphatases. FAU - Egan, C AU - Egan C AD - Department of Medical Biochemistry, University of Calgary Medical Centre, Alberta, Canada. FAU - Pang, A AU - Pang A FAU - Durda, D AU - Durda D FAU - Cheng, H C AU - Cheng HC FAU - Wang, J H AU - Wang JH FAU - Fujita, D J AU - Fujita DJ LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't PL - England TA - Oncogene JT - Oncogene JID - 8711562 RN - 0 (Cell Cycle Proteins) RN - 0 (Intracellular Signaling Peptides and Proteins) RN - 0 (Peptide Fragments) RN - 0 (Phosphopeptides) RN - 0 (Receptors, Cell Surface) RN - EC 2.7.10.2 (src-Family Kinases) RN - EC 3.1.3.16 (Phosphoprotein Phosphatases) RN - EC 3.1.3.48 (CDC25B protein, human) RN - EC 3.1.3.48 (PTPN11 protein, human) RN - EC 3.1.3.48 (PTPN6 protein, human) RN - EC 3.1.3.48 (PTPRA protein, human) RN - EC 3.1.3.48 (Protein Tyrosine Phosphatase, Non-Receptor Type 11) RN - EC 3.1.3.48 (Protein Tyrosine Phosphatase, Non-Receptor Type 6) RN - EC 3.1.3.48 (Protein Tyrosine Phosphatases) RN - EC 3.1.3.48 (Receptor-Like Protein Tyrosine Phosphatases, Class 4) RN - EC 3.1.3.48 (cdc25 Phosphatases) SB - IM MH - Breast Neoplasms/*enzymology MH - Cell Cycle Proteins/metabolism MH - Female MH - Humans MH - Intracellular Signaling Peptides and Proteins MH - Peptide Fragments/metabolism MH - Phosphopeptides/metabolism MH - Phosphoprotein Phosphatases/metabolism MH - Phosphorylation MH - Protein Tyrosine Phosphatase, Non-Receptor Type 11 MH - Protein Tyrosine Phosphatase, Non-Receptor Type 6 MH - Protein Tyrosine Phosphatases/*metabolism MH - Receptor-Like Protein Tyrosine Phosphatases, Class 4 MH - *Receptors, Cell Surface MH - Substrate Specificity MH - Tumor Cells, Cultured MH - *cdc25 Phosphatases MH - src-Family Kinases/*metabolism EDAT- 1999/02/18 00:00 MHDA- 1999/02/18 00:01 CRDT- 1999/02/18 00:00 PHST- 1999/02/18 00:00 [pubmed] PHST- 1999/02/18 00:01 [medline] PHST- 1999/02/18 00:00 [entrez] AID - 10.1038/sj.onc.1202233 [doi] PST - ppublish SO - Oncogene. 1999 Feb 4;18(5):1227-37. doi: 10.1038/sj.onc.1202233.