Abstract 1643 Monitoring β2m Aggregation Kinetics in vitro

Beta-2-microglobulin (β2m) is a 99-residue globular protein component of Major Histocompatibility Complex Class 1 which is found in all nucleated cells of the human body. Following apoptosis, β2m enters circulation where it can be degraded and excreted from the body through the renal system. In people with renal failure who undergo hemodialysis treatment, this protein cannot be properly filtered from circulation. Accumulation of β2m in in the human body leads to the development of Dialysis Related Amyloidosis (DRA), a protein misfolding disease. DRA presents in patients as aggregated protein plaques primarily comprised of misfolded β2m that deposit in cartilaginous joints. These protein plaques form in various tissues causing arthritis-like symptoms. Protein misfolding diseases, such as Alzheimer's and Parkinson's, are characterized by cross β-sheet protein associations between individual misfolded protein monomers at highly amyloidogenic regions. This mechanism results in extended fibril protein aggregates that impair the functions of tissues where they deposit. This structure is also observed in β2m plaques. The aggregation mechanism of β2m in vivo is poorly understood prompting systematic investigation into highly amyloidogenic amino acid residue sequences and their contribution to aggregation. This work probes the β2m aggregation kinetics of mutations made to the wild type (WT) amino acid residues 62-67, a region enriched with aromatic residues previously demonstrated to be highly amyloidogenic. Thioflavin (ThT) fluorescence was utilized at 2.5 pH in vitro to cause spontaneous aggregation. Three mutations to aromatic residues within this region, F62K, Y66H, and Y67S, were selected for either steric or electrostatic modification. The introduction of a charged residue to this region slows the aggregation while a steric modification has little effect on the overall aggregation rate indicating the electrostatic importance of uncharged residues in this region to β2m fibril extension. This research project is funded by the Austin College Department of Chemistry.