Amy Fluet

Expression of the human beta amyloid peptide (A beta) in transgenic Caenorhabditis elegans animals can lead to the formation of intracellular immunoreactive deposits as well as the formation of intracellular amyloid. We have used this model to identify proteins that interact with intracellular A beta in vivo. Mass spectrometry analysis of proteins that specifically coimmunoprecipitate with A beta has identified six likely chaperone proteins: two members of the HSP70 family, three alpha B-crystallin-related small heat shock proteins (HSP-16s), and a putative ortholog of a mammalian small glutamine-rich tetratricopeptide repeat-containing protein proposed to regulate HSP70 function. Quantitative reverse transcription-PCR analysis shows that the small heat shock proteins are also transcriptionally induced by A beta expression. Immunohistochemistry demonstrates that HSP-16 protein closely colocalizes with intracellular A beta in this model. Transgenic animals expressing a nonaggregating A beta variant, a single-chain A beta dimer, show an altered pattern of coimmunoprecipitating proteins and an altered cellular distribution of HSP-16. Double-stranded RNA inhibition of R05F9.10, the putative C. elegans ortholog of the human small glutamine-rich tetratricopeptide-repeat-containing protein (SGT), results in suppression of toxicity associated with A beta expression. These results suggest that chaperone function can play a role in modulating intracellular A beta metabolism and toxicity.

Transgenic Caenorhabditis elegans animals have been engineered to express wild-type and single-amino acid variants of a long form of human beta-amyloid peptide (A beta 1-42). These animals express high levels (approximately 300 ng of A beta/mg of total protein) of apparently full-length peptide, as determined by quantitative immunoblot. Expression of wild-type A beta in these animals leads to rapid production of amyloid deposits reactive with Congo red and thioflavin S. This model system has been used to examine the effect of Leu17Pro, Leu17Val, Ala30Pro, Met35Cys, and Met35Leu substitutions on the in vivo production of amyloid deposits. We find that the Leu17Pro and Met35Cys substitutions completely block the formation of thioflavin S-reactive deposits, implicating these as key residues for in vivo amyloid formation. We have also constructed transgenic strains expressing a novel A beta variant, the single-chain dimer. Animals expressing high levels of this variant also fail to produce thioflavin S-reactive deposits.