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Imaging secretory vesicles by fluorescent protein insertion in propeptide rather than mature secreted peptide

Academic Article
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Overview

authors

  • Watkins, S.
  • Geng, X. H.
  • Li, L. H.
  • Papworth, G.
  • Robbins, Paul D.
  • Drain, P.

publication date

  • July 2002

journal

  • Traffic  Journal

abstract

  • We combined confocal and live-cell imaging with a novel molecular strategy aimed at revealing mechanisms underlying glucose-regulated insulin vesicle secretion. The 'Ins-C-GFP' reporter monitors secretory peptide targeting, trafficking, and exocytosis without directly tagging the mature secreted peptide. We trapped a green fluorescent protein (GFP) reporter in equimolar quantity within the secretory vesicle by fusing it within the C peptide of proinsulin which only after nascent vesicle sealing and acidification is cleaved from the mature secreted A and B chains of insulin. Ins-C-GFP expression in mouse islets without fail exhibited punctate distribution of green fluorescence by confocal microscopy. Ins-C-GFP colocalized GFP with insulin at vesicle dense cores by immuno-electron microscopy. Glucose stimulation decreased vesicle fluorescence coordinately with enhanced secretion from islets of C-GFP detected by anti-GFP Western blots, and of insulin detected by anti-insulin radioimmunoassay. An insulin secretagogue with a red fluorescent label, glibenclamide BODIPY TR, was applied to islets expressing Ins-C-GFP. The stimulus response was imaged as a rise in red secretagogue leading to marked loss in green granules. Since neuropeptides as well as peptide hormones are processed from propeptides after sealing of secretory granules, vesicle trapping likely is widely applicable for studies on targeting, trafficking, and regulated release of secretory peptides.

subject areas

  • Animals
  • C-Peptide
  • Exocytosis
  • Glucose
  • Green Fluorescent Proteins
  • In Vitro Techniques
  • Insulin
  • Islets of Langerhans
  • Kinetics
  • Luminescent Proteins
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Microscopy, Confocal
  • Microscopy, Immunoelectron
  • Recombinant Fusion Proteins
  • Secretory Vesicles
  • Sulfonylurea Compounds
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Research

keywords

  • diabetes
  • exocytosis
  • granule
  • kinetic imaging
  • neuropeptide
  • proinsulin
  • secretion
  • secretory peptide trafficking
  • secretory vesicle
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Identity

International Standard Serial Number (ISSN)

  • 1398-9219

Digital Object Identifier (DOI)

  • 10.1034/j.1600-0854.2002.30703.x

PubMed ID

  • 12047554
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Additional Document Info

start page

  • 461

end page

  • 471

volume

  • 3

issue

  • 7

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