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Enhanced expression of a furin-cleavable proinsulin
1Department of Molecular and Cell Biology, University of Aberdeen, Institute for Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK.
Journal of Molecular Endocrinology
|December 11, 2003
Summary
Engineering cells for diabetes treatment faces challenges in proinsulin processing. Researchers identified specific amino acid changes hindering furin cleavage, enabling efficient insulin production in engineered cells for potential gene therapy.
Area of Science:
- Biotechnology
- Molecular Biology
- Endocrinology
Background:
- Diabetes mellitus treatment can be advanced by cell engineering or gene therapy.
- Current limitations include the inability of non-neuroendocrine cells to process proinsulin into insulin due to a lack of specific endoproteases (PC3/1 and PC2).
- Engineering proinsulin to be cleaved by the ubiquitous protease furin is a potential solution, but previous attempts resulted in significantly reduced expression.
Purpose of the Study:
- To investigate the causes of reduced expression of furin-cleavable proinsulin constructs.
- To engineer a furin-cleavable proinsulin construct that overcomes expression limitations and is efficiently processed to mature insulin.
Main Methods:
- Engineered several furin-cleavable rat proinsulin I cDNAs.
- Transfected human HEK293, rat L6, and mouse C(2)C(12) cell lines with engineered cDNAs.
- Assessed mRNA stability using RT-PCR and actinomycin D treatment.
- Evaluated insulin-like immunoreactivity in transfected cell lines.
- Examined the impact of amino acid substitutions on furin cleavage and expression.
Main Results:
- mRNA stability of wild-type and furin-cleavable proinsulin was not significantly different.
- Additional CpG islands in the furin-cleavable construct did not affect expression levels.
- Amino acid substitutions, specifically the addition of basic residues at the C-peptide/A-chain junction, were identified as the cause of reduced furin-cleavable proinsulin production.
- An engineered cDNA for furin-cleavable rat proinsulin I demonstrated efficient processing to mature insulin and expression levels comparable to wild-type proinsulin.
Conclusions:
- The reduced expression of previously engineered furin-cleavable proinsulin was primarily due to specific amino acid substitutions, not mRNA instability or CpG islands.
- Overcoming these substitutions allows for the development of efficient furin-cleavable proinsulin constructs.
- This engineered proinsulin holds promise for cell engineering and gene therapy strategies in treating diabetes mellitus.