Fas-associated death receptor signaling evoked by human amylin in islet beta-cells.
OBJECTIVE
Aggregation of human amylin (hA) into beta-sheet-containing oligomers is linked to islet beta-cell dysfunction and the pathogenesis of type 2 diabetes. Here, we investigated possible contributions of Fas-associated death-receptor signaling to the mechanism of hA-evoked beta-cell apoptosis.


METHODS
We measured responses to hA in isolated mouse islets and two insulinoma cell lines, wherein we measured Fas/Fas ligand (FasL) and Fas-associated death domain (FADD) expression by quantitative RT-PCR, Western blotting, and immunofluorescence staining. We used two anti-Fas/FasL blocking antibodies and the Fas/FasL antagonist Kp7-6 to probe roles of Fas interactions in the regulation of apoptosis in hA-treated beta-cells and measured Kp7-6-mediated effects on beta-sheet formation and aggregation using circular dichroism and thioflavin-T binding.


RESULTS
hA treatment stimulated Fas and FADD expression in beta-cells. Both blocking antibodies suppressed hA-evoked apoptosis but did not modify its aggregation. Therefore, Fas receptor interactions played a critical role in induction of this pathway. Interestingly, hA-evoked beta-cell apoptosis was suppressed and rescued by Kp7-6, which also impaired hA beta-sheet formation.


CONCLUSIONS
This is the first report linking hA-evoked induction and activation of Fas and FADD to beta-cell apoptosis. We have identified a Fas/FasL antagonist, Kp7-6, as a potent inhibitor of hA aggregation and related beta-cell death. These results also support an interaction between hA and Fas on the surface of apoptotic beta-cells. Increased expression and activation of Fas in beta-cells could constitute a molecular event common to the pathogenesis of both type 1 and type 2 diabetes, although the mode of pathway activation may differ between these common forms of diabetes.
Zhang
Shaoping
S
School of Biological Sciences, University of Auckland, Level 4, 3A Symonds St., Private Bag 92019, Auckland 1142, New Zealand.
Liu
Hong
H
Yu
Hua
H
Cooper
Garth J S
GJ
D000682:Amyloid / Q000494:pharmacology*; D000818:Animals; D045744:Cell Line, Tumor; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics; D053200:Fas-Associated Death Domain Protein / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007340:Insulinoma; D058228:Islet Amyloid Polypeptide; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D000682:Amyloid; D053200:Fas-Associated Death Domain Protein; D058228:Islet Amyloid Polypeptide