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Scientific article
English

Proinsulin modified by analogues of arginine and lysine is degraded rapidly in pancreatic B-cells

Contributors

Halban, Philippe A.; Amherdt, M.; Orci, Lelio; Renold, A. E.

Published in

Biochemical journal, vol. 219, no. 1, p. 91-97

Publication date

1984

Abstract

Modified cytosolic proteins are known to be degraded more rapidly than their native counterparts. In order to determine whether the same applies to a modified protein within the potentially protective environment of secretory granules, rat islets were labelled [( 3H]leucine) in the presence or absence (controls) of 3 mM-canavanine and 3 mM-thialysine (analogues of arginine and lysine respectively), followed by a 24h 'chase' period without analogues. The results showed the following. (1) Incorporation of the analogues into newly synthesized labelled proinsulin inhibited its conversion into insulin during the chase period. (2) Despite this block in conversion, the modified proinsulin was released from islets at the same rate as native proinsulin and insulin from control islets. (3) Morphometric analysis of high-resolution autoradiographs showed that products labelled in the presence of analogues were sequestered into secretory granules at the same rate as native products in control B-cells. (4) Only 7% of prelabelled proinsulin had been degraded within islet cells during the chase period in control islets, compared with 36% for proinsulin prelabelled in the presence of analogues. (5) Control experiments showed that the analogues had no effect on the release or intracellular degradation of unmodified stored insulin (present in islets before exposure to the analogues). (6) Despite sequestration into secretory granules, modified proinsulin, if not released from B-cells, is thus degraded more rapidly than native products.

Keywords

  • Animals
  • Canavanine/ metabolism
  • Chemical Precipitation
  • Culture Techniques
  • Cysteine/ analogs & derivatives/metabolism
  • Cytoplasmic Granules/metabolism
  • Insulin/metabolism
  • Islets of Langerhans/ metabolism
  • Leucine/metabolism
  • Proinsulin/ metabolism
  • Rats

UNIGE affiliation entities

Citation (ISO format)

HALBAN, Philippe A. et al. Proinsulin modified by analogues of arginine and lysine is degraded rapidly in pancreatic B-cells. In: Biochemical journal, 1984, vol. 219, n° 1, p. 91–97. doi: 10.1042/bj2190091

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Additional URL for this publication

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1153452/pdf/biochemj00330-0096.pdf

Journal ISSN

0264-6021
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Technical informations

Creation

12/07/2010 11:58:07

First validation

12/07/2010 11:58:07

Update

14/03/2023 15:51:11

Status update

14/03/2023 15:51:10

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