title: Protein tyrosine phosphatase 1B is located with glucagon vesicles, and its concentration is inversely correlated with the rate of glucagon secretion of INR1G9 cells.
abstract: High concentrations of protein tyrosine phosphatase (PTP) were found with secretory vesicles of glucagon-producing INR1G9 cells by electron microscopic immunocytochemistry, using a polyclonal antiserum specific for the PTP1B/T-cell (TC)PTP subfamily of PTP. Since TCPTP protein and mRNA were below the detection limit in the cells but significant amounts of PTP1B and mRNA were recognised by a specific monoclonal antibody and a mRNA probe we conclude, that the PTP associated with the vesicles is PTP1B. Only reverse transcriptase (RT)-PCR with primers specific for PTP1B yielded a product of the expected nucleotide sequence. Thus, we conclude that the PTP associated with the vesicles is PTP1B. The presence of vanadate for 48 h attenuated PTP1B expression and caused reduction of steady-state levels of the phosphatase. These conditions also led to a continuing increase in the steady-state rate of glucagon release by the cells. This rate and tyrosine phosphatase levels showed an inverse relationship, suggesting a suppressive role of PTP1B on the regulated secretion of glucagon by INR1G9 cells.
authors.affiliation: University of Giessen, Institute of Anatomy and Cell Biology, D-35385 Giessen, Germany. Monika.Wimmer@anatomie.med.uni-giessen.de
authors.forename: M
authors.initials: M
authors.lastname: Wimmer
authors.forename: C
authors.initials: C
authors.lastname: Tag
authors.forename: D
authors.initials: D
authors.lastname: Schreiner
authors.forename: H W
authors.initials: HW
authors.lastname: Hofer
mesh_terms: D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D045744:Cell Line, Tumor; D006224:Cricetinae; D005934:Glucagon / Q000378:metabolism*; D015151:Immunoblotting / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D010179:Pancreas / Q000201:enzymology* / Q000378:metabolism; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012636:Secretory Rate; D014638:Vanadates / Q000494:pharmacology
chemical_list: D012333:RNA, Messenger; D014638:Vanadates; D005934:Glucagon; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases