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The F-actin modifier villin regulates insulin granule dynamics and exocytosis downstream of islet cell autoantigen 512.

Mol. Metab. 5, 656-68 (2016)
Publishers Version Research data DOI PMC
Open Access Gold
Creative Commons Lizenzvertrag
as soon as is submitted to ZB.
OBJECTIVE: Insulin release from pancreatic islet β cells should be tightly controlled to avoid hypoglycemia and insulin resistance. The cortical actin cytoskeleton is a gate for regulated exocytosis of insulin secretory granules (SGs) by restricting their mobility and access to the plasma membrane. Prior studies suggest that SGs interact with F-actin through their transmembrane cargo islet cell autoantigen 512 (Ica512) (also known as islet antigen 2/Ptprn). Here we investigated how Ica512 modulates SG trafficking and exocytosis. METHODS: Transcriptomic changes in Ica512 (-/-) mouse islets were analyzed. Imaging as well as biophysical and biochemical methods were used to validate if and how the Ica512-regulated gene villin modulates insulin secretion in mouse islets and insulinoma cells. RESULTS: The F-actin modifier villin was consistently downregulated in Ica512 (-/-) mouse islets and in Ica512-depleted insulinoma cells. Villin was enriched at the cell cortex of β cells and dispersed villin (-/-) islet cells were less round and less deformable. Basal mobility of SGs in villin-depleted cells was enhanced. Moreover, in cells depleted either of villin or Ica512 F-actin cages restraining cortical SGs were enlarged, basal secretion was increased while glucose-stimulated insulin release was blunted. The latter changes were reverted by overexpressing villin in Ica512-depleted cells, but not vice versa. CONCLUSION: Our findings show that villin controls the size of the F-actin cages restricting SGs and, thus, regulates their dynamics and availability for exocytosis. Evidence that villin acts downstream of Ica512 also indicates that SGs directly influence the remodeling properties of the cortical actin cytoskeleton for tight control of insulin secretion.
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Publication type Article: Journal article
Document type Scientific Article
Keywords D, Diffusion Coefficient ; Egfp, Enhanced Green Fluorescent Protein ; F-actin ; Granules ; Ipgtt, Intraperitoneal Glucose Tolerance Test ; Ivgtt, Intravenous Glucose Tolerance Test ; Ica512 ; Ica512, Islet Cell Autoantigen ; Insulin ; Ogtt, Oral Glucose Tolerance Test ; Rt-dc, Real-time Deformability Cytometry ; Se, Standard Error ; Sg, Secretory Granules ; Secretion ; Tirfm, Total Internal Reflection Fluorescence Microscopy ; Villin; Beta-cells; Glucose-transporter; Targeted Disruption; Chromaffin Cells; Plasma-membrane; Secretion; Ica512; Gelsolin; Protein; Ia-2
Reviewing status
Institute(s) Institute for Pancreatic Beta Cell Research (IPI)