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Cell surface trafficking of Fas in NIT-1 cells and dissection of surface and total Fas expression
P Augstein1, A Dunger, C Salzsieder
1Gerhardt Katsch Institute of Diabetes-Karlsburg e. V., Greifswalder Strasse 11e, 17495 Karlsburg, Germany. augstein@mail.uni-greifswald.de
Abstract:
The appearance of Fas receptor at the surface of pancreatic beta-cells affected by progressive insulitis strongly suggests that Fas-mediated beta-cell apoptosis plays an important role in the pathogenesis of type 1 diabetes. In support of this concept, the present study has shown that islet cells from NOD mice and the beta-cell line NIT-1 respond to the proinflammatory cytokines IL-1beta and IFN-gamma with Fas surface expression in a dose- and time-dependent manner. Moreover, the prevention of cytokine-induced surface Fas expression by actinomycin D, cycloheximide, and brefeldin A demonstrated that trafficking of Fas to the beta-cell surface requires RNA and protein synthesis and, in addition is critically dependent on intracellular protein transport. Compared with total cellular Fas protein, the amount of Fas at the cell surface was relatively small and indicated that Fas is preferentially expressed in cytoplasmic compartments of NIT-1 cells. It is concluded that inflammatory insults specifically induce translocation of Fas to the beta-cell surface and that interference with cell surface Fas expression is a new strategy to improve beta-cell survival in inflamed islets.
Insights
Fas receptor on pancreatic beta-cells triggers apoptosis, contributing to type 1 diabetes. Blocking Fas expression on beta-cells may improve survival in inflamed islets.
Area of Science:
- Immunology
- Endocrinology
- Cell Biology
Background:
- Progressive insulitis in type 1 diabetes involves pancreatic beta-cell apoptosis.
- Fas receptor expression on beta-cells suggests a role in disease pathogenesis.
Purpose of the Study:
- To investigate the role of Fas receptor expression in pancreatic beta-cell apoptosis.
- To determine the mechanisms regulating Fas surface expression in response to inflammatory cytokines.
Main Methods:
- Utilized NOD mice and NIT-1 beta-cell line.
- Administered proinflammatory cytokines (IL-1beta and IFN-gamma).
- Assessed Fas surface expression and inhibited its induction using actinomycin D, cycloheximide, and brefeldin A.
Main Results:
- NOD mouse islet cells and NIT-1 cells showed dose- and time-dependent Fas surface expression upon cytokine stimulation.
- Inhibition of RNA/protein synthesis and intracellular transport blocked cytokine-induced Fas surface expression.
- Fas protein was predominantly found in cytoplasmic compartments, with a smaller amount on the cell surface.
Conclusions:
- Inflammatory insults induce specific translocation of Fas to the beta-cell surface.
- Interfering with cell surface Fas expression presents a novel strategy for enhancing beta-cell survival in inflamed islets.
- This finding offers a potential therapeutic target for type 1 diabetes.