Abstract:
The formation of
amyloid fibrils plays a role in a wide range of diseasescollectively known as amyloidosis. Amyloid fibrils are formed
when peptides or proteinsmisfold and deposit in tissues and organs. These deposits are a characteristic feature of a
number of diseases including Type II diabetes, Alzheimer's disease, and Parkinson's disease. Our lab studies
the amyloidogenic peptides Islet Amyloid Polypeptide (IAPP) from type II diabetes and the Aá 40 and
Aá42
peptides from Alzheimer's disease. There is intriguing, albeit indirect, evidence that suggests that inhibitors of
IAPP amyloid formation may also inhibit amyloid formation by Aá. If true, this suggests a new strategy for
designing inhibitors; specifically inhibitors of amyloid formation by one peptide can be used against the other.Insulin
is known to be an inhibitor of IAPP. It is made up of an A and B chain andthe B chain displays potent inhibitory
effects. In addition, a short segment located in theB chain has been showed to bind IAPP and thus might inhibit amyloid
formation.Based on these findings, experiments were conducted to test the possible inhibitoryeffects of insulin, the
insulin B chain, and a short fragment from the insulin B chain onAá40 and IAPP.Solid phase peptide synthesis was
used to synthesize thee Aβ40 peptide and a 12-residue fragment of the insulin B chain (IBSF). A
new
protocol
was developed andemployed to obtain the kinetic curve of Aá40 amyloid formation using
Thioflavin-Tbinding
fluorescence assays. Aá40 was incubated with insulin, the insulin B chain, and IBSF. Transmission electron
microscopy was used to observe what had occurred during the incubation and confirm the results of the fluorescence
assays. Similar experiments with IAPP were done as well, however, the rate of fibrillization was found to be much
slower. This suggested that there is indeed an interaction between these two peptides. Thus, concentration dependent
studies and further experimentation were done to better observe and assess these interactions.
