title: Processing of thyrotropin-releasing hormone prohormone (pro-TRH) in the adult rat pancreas: identification and localization of pro-TRH-related peptides in beta-cells of pancreatic islets.
abstract: Rat TRH prohormone (pro-TRH) contains five separate copies of the TRH progenitor sequence, Gln-His-Pro-Gly. All five sequences are flanked by paired basic amino acid cleavage sites and linked together by connecting sequences. RIAs to synthetic TRH and prepro-TRH-(178-199) were used to investigate pro-TRH processing in the endocrine pancreas of adult rats. HPLC analysis of adult rat pancreatic extracts showed the presence of a major immunoreactive peptide eluting at the position of prepro-TRH-(178-199). An additional peak coeluting with [less than Glu172]prepro-TRH-(172-199) (less than Glu = pyroglutamyl) revealed the presence of a C-terminally extended form of TRH. Quantification of TRH in pancreatic extracts indicated the presence of 22 mol TRH/mol prepro-TRH-(178-199) and 17 mol TRH/mol [less than Glu172]prepro-TRH-(172-199). Treatment of rats with streptozotocin markedly reduced the pancreatic content of both immunoreactive TRH (-84%) and immunoreactive prepro-TRH-(178-199) (-62%). Light microscopic immunocytochemistry showed that prepro-TRH-(178-199)-like immunoreactivity was exclusively located within insulin-containing cells of the pancreatic islets. At the electron microscopic level, prepro-TRH-(178-199) immunoreactivity appeared to be concentrated in secretory granules. The present study demonstrates that processing of pro-TRH generates both non-TRH- and TRH-related peptides in the adult rat pancreas. Our data also indicate that beta-cells of the endocrine pancreas are the major source of TRH- and pro-TRH-derived peptides.
authors.affiliation: Laboratoire d'Histologie-Embryologie, CNRS URA 559, Faculté de Médecine Lyon-Sud, Oullins, France.
authors.forename: P
authors.initials: P
authors.lastname: Leduque
authors.forename: M
authors.initials: M
authors.lastname: Bulant
authors.forename: P M
authors.initials: PM
authors.lastname: Dubois
authors.forename: P
authors.initials: P
authors.lastname: Nicolas
authors.forename: H
authors.initials: H
authors.lastname: Vaudry
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D007150:Immunohistochemistry; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000032:analysis / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D015183:Restriction Mapping; D013973:Thyrotropin-Releasing Hormone / Q000032:analysis / Q000235:genetics*
chemical_list: D011498:Protein Precursors; D013973:Thyrotropin-Releasing Hormone; C046418:pro-thyrotropin releasing hormone; D011761:Pyrrolidonecarboxylic Acid