BIOCHEMICAL CHARACTERIZATION OF BENCE JONES PROTEINS FROM DIFFERENT LIGHT CHAIN DISEASES

Clonal proliferation of monoclonal plasma cells can result in the deposition of immunoglobulin light chains and/or the excretion of Bence Jones proteins in the urine. Multiple Myeloma (MM), Light Chain Deposition Disease (LCDD) and Light Chain Amyloidosis (AL) are three light chain related diseases that fall into this category.

The characteristics of each light chain disease vary: MM shows bone lesions, hypercalcemia, renal failure, and anemia; LCDD is localized in the basement membrane of the kidney and it forms granular, amorphous aggregates; while AL has deposition of immunoglobulin light chains as amyloid fibrils in vital organs leading to organ failure and death. However, all of them involve clonal proliferation of light chains. Kappa light chains are more prevalent in LCDD and MM while lambda light chains are more prevalent in AL .

We are interested in comparing protein stability and amyloid/aggregate conditions and pathways for MM, LCDD, and AL proteins. According to the literature, LCDD may favor an off-pathway intermediate formation that leads to aggregation rather than amyloid formation. The LCDD intermediate is suggested to be partially unfolded or misfolded. Our study involved isolating and purifying proteins from various patients' urine samples for all three diseases. We are characterizing 2 proteins for both MM and AL and 1 protein for LCDD. Protein unfolding/refolding was followed by thermal and chemical denaturation using Circular Dichroism and Fluorescence Spectroscopy. We have performed amyloid/aggregate formation in vitro for all proteins using Thioflavine T dye binding assays as well as Electron Microscopy.

We have the LCDD protein to be the most thermodynamically stable protein out of our MM and AL proteins. Currently, we are interested in studying and understanding the possible differences that will result in different pathways/morphologies between fibrils and LCDD aggregates.