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Molecular cloning of phogrin, a protein-tyrosine phosphatase homologue localized to insulin secretory granule membranes.

Authors: Wasmeier, C  Hutton, JC 
Citation: Wasmeier C and Hutton JC, J Biol Chem 1996 Jul 26;271(30):18161-70.
Pubmed: (View Article at PubMed) PMID:8663434

An insulin granule membrane protein-tyrosine phosphatase (PTP) homologue, phogrin, was cloned by expression screening of a rat insulinoma cDNA library. The 3723-base pair cDNA encoded a transmembrane glycoprotein of 1004 amino acids (Mr 111876) that underwent post-translational proteolysis to 60-64-kDa products after a 30-min delay. The kinetics of proteolytic conversion (t1/2 = 45 min) and turnover (t1/2 = 12 h) were consistent with sorting and conversion in a late compartment of the secretory pathway. Studies on the native beta-cell protein suggested that the COOH-terminal PTP domain was on the cytosolic face of the secretory granule. The lumenal segment was comprised of a protease-resistant globular domain of around 25 kDa. Its localization and topology is thus consistent with a transmembrane receptor function related to granule biogenesis, exocytosis, or subsequent membrane recovery, and it should prove to be a useful cell biological marker for the granule membrane. High expression of the mRNA (5.4 kilobases) and protein was evident in islets, pancreatic alpha- and beta-cell tumor lines, brain cells, and other cells of neuroendocrine lineage. It is closely related to the diabetic autoantigen ICA512 (IA-2) (42% identity overall; 80% in the 260-amino acid PTP domain) and thus a potential target of autoimmunity in diabetes mellitus.

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RGD Object Information
RGD ID: 61724
Created: 2001-04-10
Species: All species
Last Modified: 2001-04-10
Status: ACTIVE



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