(72b) A Peptide Probe for Rapid Detection of Various Amyloid Oligomers

Aggregation of amyloid is implicated in the pathology of various neurodegenerative diseases. A considerable amount of data has identified soluble amyloid oligomers as potentially significant toxic agents. Rapid, specific and quantitative detection is preferred for accurate profiling of structurally unstable oligomers as well as for implementation of high-throughput assays for pharmaceutical applications. PG46 is an engineered beta-amyloid (Abeta) variant, constructed by integrating Abeta self-recognition sequences with the conformation-sensitive biarsenical fluorescent dye, FlAsH. PG46 was found to be an effective peptide probe for rapid, specific and quantitative detection of Abeta oligomers. However, PG46 was highly aggregation-prone and displayed a limited repertoire of detectable Abeta oligomers. Here, we report the creation of a novel molecular probe, PG44, by C-terminal truncation of PG46. PG44 exhibited a reduced self-aggregation propensity and a different conformation when compared to PG46, and generated specific FlAsH fluorescence signals as a result of binding to various Abeta oligomers, including those not readily detectable by PG46. We also show that sensitivity of PG44 for detection of certain Abeta oligomers may be increased by lowering PG44 concentration and thus decreasing the extent of self-aggregation of PG44. Our results suggest that PG44 can serve as an important molecular probe with a broadened repertoire of detectable Abeta oligomeric aggregates. We believe that detection of Abeta oligomers using our peptide probe would potentially contribute toward a better understanding of the molecular basis of Abeta oligomerization and the development of Abeta oligomer-based early diagnostics as well as therapeutic drugs targeting Abeta oligomers. We will also discuss our efforts to create a molecular probe for rapid, specific and quantitative detection of oligomers formed by other amyloid proteins.