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Scientific article
English

Des-(27-31)C-peptide. A novel secretory product of the rat pancreatic beta cell produced by truncation of proinsulin connecting peptide in secretory granules

Published inThe Journal of biological chemistry, vol. 271, no. 44, p. 27475-27481
Publication date1996
Abstract

Insulin and connecting peptide (C-peptide) are produced in equimolar amounts during proinsulin conversion in the pancreatic beta cell secretory granule. To determine whether insulin and C-peptide are equally stable in beta cell granules (and thus secreted in equimolar amounts), neonatal and adult rat beta cells were pulse-chased, and radiolabeled insulin and C-peptide analyzed by high performance liquid chromatography. A novel truncated C-peptide was identified and shown by mass spectrometry to be des-(27-31)C-peptide (loss of 5 C-terminal amino acids). Des-(27-31)C-peptide is a major beta cell secretory product, accounting for 37.4 +/- 1.6% (neonatal) and 8.5 +/- 0.6% (adult) of total labeled C-peptide in secretory granules after 10 h of chase. Des-(27-31)C-peptide is also secreted in a glucose-sensitive manner from the perfused adult rat pancreas, accounting for approximately 10% of total C-peptide immunoreactivity secreted. Human C-peptide is also a substrate for truncation in granules. Thus, when human proinsulin was expressed (infection with recombinant adenovirus) in transformed (INS) rat beta cells, human des-(27-31)C-peptide was secreted along with the intact human peptide and both intact and truncated rat C-peptide. In addition to truncation, 33.1 +/- 1.2% of C-peptide in neonatal but not adult rat beta cell granules was further degraded. Such degradation was completely inhibited by ammonium chloride (known to neutralize intra-granular pH), whereas truncation was only partially inhibited by approximately 50%. In conclusion, a novel beta cell secretory product, des-(27-31)C-peptide, has been identified and should be considered as a potential bioactive peptide. Both truncation and degradation of C-peptide are responsible for non-equimolar secretion of insulin and C-peptide in rat beta cells.

Keywords
  • Aging/ physiology
  • Amino Acid Sequence
  • Animals
  • Animals, Newborn
  • C-Peptide/ biosynthesis/chemistry/genetics/secretion
  • Cells, Cultured
  • Chromatography, High Pressure Liquid
  • Cytoplasmic Granules/ metabolism
  • Humans
  • Insulin/ biosynthesis/chemistry/secretion
  • Islets of Langerhans/growth & development/ metabolism/secretion
  • Molecular Sequence Data
  • Peptide Fragments/ biosynthesis/chemistry/genetics
  • Proinsulin/biosynthesis/ metabolism
  • Protein Processing, Post-Translational
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Proteins/biosynthesis/chemistry
  • Sequence Homology, Amino Acid
  • Transfection
Citation (ISO format)
VERCHERE, C. B. et al. Des-(27-31)C-peptide. A novel secretory product of the rat pancreatic beta cell produced by truncation of proinsulin connecting peptide in secretory granules. In: The Journal of biological chemistry, 1996, vol. 271, n° 44, p. 27475–27481. doi: 10.1074/jbc.271.44.27475
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Identifiers
ISSN of the journal0021-9258
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