The Buxbaum Laboratory

Research

Molecular Basis of Acquired and Hereditary Human Disease

In the broadest sense our laboratory is focused on the investigation of the interface between genetics and environment as reflected in disorders of protein conformation. More specifically we examine hereditary and sporadic disorders that exhibit a degree of age-dependence and are characterized by protein misfolding. The amyloidoses were the first recognized examples of protein deposition diseases, being defined as extracellular, histologically homogeneous tissue deposits that bind the dyes Thioflavine S, T and Congo red, the latter with positive birefringence under polarized light. The deposits also contain the serum amyloid P component (SAP), apolipoprotein E (ApoE) and the heparan sulfate proteoglycan, perlecan. Electron microscopy of the deposits revealed a discrete fibrillar structure. In almost all cases the deposits are formed from proteins produced for secretion. Deposition with tissue compromise may be local but is frequently at a distance from the site of synthesis. Twenty three human proteins have been associated with local or systemic deposition associated with tissue dysfunction. Our current protein of interest is transthyretin, the normal carrier of retinol-binding protein charged with retinol and a portion of the human thyroid hormone thyroxine (T4). In humans there have been over 80 specific mutations occurring at 55 different positions in the 127 amino acid protein. In addition 10 to 25% of individuals above the age of 80 have fibrils composed of the wild type molecule in their hearts, frequently compromising normal function.

Our goals are to understand the process of protein misfolding leading to deposition in vivo, the genetic factors involved and the role of aging, all with the notion of learning how to control it, either physiologically or with small molecules developed by our colleagues.

We have analyzed the transthyretin gene as well as other potential candidate accessory genes for their impact on the development of disease in human populations. Our experimental systems include in vitro systems to study aggregation, cell culture systems to analyze the events that result in cell damage and apoptosis on exposure of cells to the amyloidogenic proteins and transgenic mice expressing amyloidogenic human transthyretins that develop age dependent tissue deposition. In collaboration with the Kelly laboratory at TSRI we are using these tools to develop small molecule therapies for these disorders.

It is our belief that by using an integrated approach using genetics, protein chemistry, cell biology and experimental pathology we can gain insight into the combination of phenomena responsible for the disordered protein conformation that seems to be associated with certain aspects of the aging process.