Protein tyrosine phosphatase 1B is located with glucagon vesicles, and its concentration is inversely correlated with the rate of glucagon secretion of INR1G9 cells

in Journal of Endocrinology
Authors:
M Wimmer
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C Tag
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D Schreiner
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HW Hofer
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DOI:
https://doi.org/10.1677/joe.0.1810437
Volume/Issue:
Volume 181: Issue 3
Article Type:
Other
Page Range:
437–447
Online Publication Date:
01 Jun 2004
Free access

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.

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Print ISSN:
0022-0795
Online ISSN:
1479-6805
Page(s):
11
Article Type:
Other
Print Publication Date:
01 Jun 2004
Online Publication Date:
01 Jun 2004