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Increased expression of polypyrimidine tract binding protein results in higher insulin mRNA levels
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
2005 (English)In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 328, no 1, 38-42 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to further elucidate the role of the polypyrimidine tract binding protein (PTB) in the control of insulin mRNA stability. We observed that the glucose- or interleukin-1β-induced increase in insulin mRNA was paralleled by an increase in PTB mRNA. To further test the hypothesis that PTB controls insulin gene expression, βTC-6 cells were treated with a PTB-specific siRNA to modify the β-cell content of PTB. Surprisingly, we observed an increase in PTB mRNA and PTB protein levels in response to the siRNA treatment. In addition, the PTB-siRNA treatment also increased insulin mRNA. We conclude that expression of the PTB gene controls insulin production.

Place, publisher, year, edition, pages
2005. Vol. 328, no 1, 38-42 p.
Keyword [en]
Insulin mRNA, Polypyrimidine tract binding protein, mRNA stability, siRNA, β-cell
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-79787DOI: 10.1016/j.bbrc.2004.12.147PubMedID: 15670747OAI: oai:DiVA.org:uu-79787DiVA: diva2:107700
Available from: 2006-04-13 Created: 2006-04-13 Last updated: 2013-11-20Bibliographically approved
In thesis
1. The Role of RNA Binding Proteins in Insulin Messenger Stability and Translation
Open this publication in new window or tab >>The Role of RNA Binding Proteins in Insulin Messenger Stability and Translation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although the reason for insufficient release of insulin in diabetes mellitus may vary depending on the type and stage of the disease, it is of vital importance that an amplified insulin biosynthesis can meet the increased need during periods of hyperglycemia. The insulin mRNA is highly abundant in beta cells and changes in insulin mRNA levels are, at least in part, controlled by altered rates of mRNA degradation. Since the mechanisms behind the control of insulin messenger stability and translation are still largely obscure, the work presented in this thesis therefore aimed to further investigate the role of insulin mRNA binding proteins in the control of insulin mRNA break-down and utilization for insulin biosynthesis.

To clarify how glucose regulates insulin mRNA stability and translation we studied the correlation between polypyrimidine tract binding protein (PTB) gene expression and insulin mRNA levels. It was found that an increase in PTB mRNA and protein levels is paralleled by an increase in insulin mRNA levels. It was also found that PTB binds to the 5’-untranslated region of the insulin mRNA and that insulin mRNA can be translated through a cap-independent mechanism in human islets of Langerhans, possibly due to the interaction with PTB. Further it was discovered that the suppressed insulin biosynthesis in human islets during glucotoxicity is partly due to an induction of the microRNA miR-133a. This induction leads to decreased levels of PTB and insulin biosynthesis rates in human islets. Finally, we were able to identify two proteins, hnRNP U and TIAR, that bind specifically to the insulin mRNA in vitro, and show that the stability and translation of insulin mRNA is oppositely affected by these proteins.

In conclusion, insulin producing cells seem to be able to regulate insulin messenger stability and translation by a control mechanism in which the binding of specific proteins to the insulin messenger dictates the outcome. A better understanding of the events leading to insulin production may in the future aid in optimal diagnosis and treatment of type 2 diabetes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 44 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 596
National Category
Cell and Molecular Biology
Research subject
Medical Cell Biology
Identifiers
urn:nbn:se:uu:diva-130234 (URN)978-91-554-7885-8 (ISBN)
Public defence
2010-10-15, B22, BMC, Husargatan 3, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2010-09-23 Created: 2010-09-05 Last updated: 2011-03-04

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Fred, Rikard GWelsh, Nils

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