Proinsulin is converted to insulin by the two endoproteases PC2 and PC3. For complete conversion to insulin, cleavage must occur at both the B-chain/C-peptide and C-peptide/A-chain junctions of proinsulin. Studies in vitro have shown the specificity of PC3 for the B-chain/C-peptide junction and that of PC2 for the C-peptide/A-chain junction. In contrast, studies in vivo have suggested that the proinsulin cleavage substrate specificity of these two endoproteases might be more complex. We have now used recombinant adenovirus to overexpress PC2 or PC3 in the rat insulinoma cell line INS. These cells convert proinsulin more slowly than primary pancreatic β-cells, possibly reflecting their lower levels of PC3. Infection of INS cells with the corresponding recombinant adenovirus led to 5–10-fold and 20–40-fold increases in PC2 and PC3 expression respectively. Recombinant adenovirus is thus an effective tool for expressing proteins at high levels in slow-growing INS cells. Overexpression of either PC2 or PC3 in INS cells led to a striking acceleration of conversion of proinsulin to insulin and to a decreased accumulation of the conversion intermediate des-64.65-split proinsulin (cleaved only at the A-chain/C-peptide junction). There was no detectable accumulation of des-31.32-split proinsulin (cleaved only at the B-chain/C-peptide junction) after overexpression of either enzyme. Taken together, the data indicate that when expressed at high levels, both PC2 and PC3 seem to be able to cleave proinsulin at both its junctions in vivo.
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November 1996
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Research Article|
November 15 1996
Proinsulin processing in the rat insulinoma cell line INS after overexpression of the endoproteases PC2 or PC3 by recombinant adenovirus Available to Purchase
Jean-Claude IRMINGER;
Jean-Claude IRMINGER
*
1Laboratoires de Recherche Louis Jeantet, University of Geneva Medical Center, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
*To whom correspondence should be addressed.
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Katharina MEYER;
Katharina MEYER
1Laboratoires de Recherche Louis Jeantet, University of Geneva Medical Center, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
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Philippe HALBAN
Philippe HALBAN
1Laboratoires de Recherche Louis Jeantet, University of Geneva Medical Center, 1 rue Michel Servet, 1211 Geneva 4, Switzerland
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Publisher: Portland Press Ltd
Received:
April 30 1996
Revision Received:
June 28 1996
Accepted:
July 23 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 320 (1): 11–15.
Article history
Received:
April 30 1996
Revision Received:
June 28 1996
Accepted:
July 23 1996
Citation
Jean-Claude IRMINGER, Katharina MEYER, Philippe HALBAN; Proinsulin processing in the rat insulinoma cell line INS after overexpression of the endoproteases PC2 or PC3 by recombinant adenovirus. Biochem J 15 November 1996; 320 (1): 11–15. doi: https://doi.org/10.1042/bj3200011
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