Profile and Differential Expression of Protein Tyrosine Phosphatases in Mouse Pancreatic Islet Tumor Cell Lines:

Summary Protein tyrosine phosphatases (PTPs) play important roles in cell growth and differentiation of normal and tumor cells. In this study, we analyzed the PTP profile in two pancreatic islet tumor cell lines. Transcripts were isolated from αTC- 1 (glucagon-secreting) and βTC-1 (insulin-secreting) cell lines for templates. A pair of degenerative primers, based on the conserved regions of known PTPs, was used to amplify the transcripts by polymerase chain reaction. A total of 1,620 clones was examined by restriction enzyme analysis and cDNA sequencing. Twenty-one PTPs were identified, including nine cytosolic PTPs (TcPTP, P19PTP, PTP1B, PTPMEG, PTPIC, SYP, PTPH1, PTPLI, and PTPD1), nine transmembrane PTPs (FTPδ, PTPλ, PTPK, DEP-1, IA-2, LAR, PTPα, PTPNE3, and PTPε), and three new PTPs-PTPμ-like PTPK-like, and IA-2β. An RNase protection assay demonstrated that some of these PTPs were expressed predominantly in glucagonoma (i.e., PTPδ and IA-2) and others in insulinoma (i.e., PTP1C, PTPk, and PTPNE3) cells. In this report, we present the first profile of PTPs in α and p tumor cell lines.