
Anna Wendt
Assistant researcher

MiR-335 overexpression impairs insulin secretion through defective priming of insulin vesicles
Author
Summary, in English
MicroRNAs contribute to the maintenance of optimal cellular functions by fine-tuning protein expression levels. In the pancreatic β-cells, imbalances in the exocytotic machinery components lead to impaired insulin secretion and type 2 diabetes (T2D). We hypothesize that dysregulated miRNA expression exacerbates β-cell dysfunction, and have earlier shown that islets from the diabetic GK-rat model have increased expression of miRNAs, including miR-335- 5p (miR-335). Here, we aim to determine the specific role of miR-335 during development of T2D, and the influence of this miRNA on glucose-stimulated insulin secretion and Ca2+-dependent exocytosis. We found that the expression of miR-335 negatively correlated with secretion index in human islets of individuals with prediabetes. Overexpression of miR-335 in human KndoC- (βH\ and in rat INS-1 832/13 cells (OE335) resulted in decreased glucose-sti- mulated insulin secretion, and OE335 cells showed concomitant reduction in three exocytotic proteins: SNAP25, Syntaxin-binding protein 1 (STXBPl), and synaptotagmin 11 (SYTll). Single-cell capacitance measurements, complemented with TIRF microscopy of the granule marker NPY-mEGFP demonstrated a significant reduction in exocytosis in OE335 cells. The reduction was not associated with defective docking or decreased Ca2+ current More likely, it is a direct consequence of impaired priming of already docked granules. Earlier reports have proposed reduced granular priming as the cause of reduced first-phase insulin secretion during prediabetes. Here, we show a specific role of miR-335 in regulating insulin secretion during this transition period. Moreover, we can conclude that miR-335 has the capacity to modulate insulin secretion and Ca2+-dependent exocytosis through effects on granular priming.
Department/s
- Diabetes - Islet Cell Exocytosis
- EXODIAB: Excellence of Diabetes Research in Sweden
Publishing year
2017-11-01
Language
English
Publication/Series
Physiological Reports
Volume
5
Issue
21
Document type
Journal article
Publisher
John Wiley & Sons Inc.
Topic
- Cell and Molecular Biology
- Endocrinology and Diabetes
Keywords
- Beta cell
- Exocytosis
- Insulin secretion
- MicroRNA
- Patch-clamp
- SNAP25
- STXBP1
- TIRF
- Type 2 Diabetes
Status
Published
Research group
- Diabetes - Islet Cell Exocytosis
ISBN/ISSN/Other
- ISSN: 2051-817X