Light chain (AL) amyloidosis is an incurable human disease characterized by the misfolding and systemic amyloid aggregation of immunoglobulin light chains. Several studies have reported that soluble light chain internalize into renal and cardiac cells; but the correlation between proteins toxicity, their biophysical and cellular internalization properties, and the mechanisms triggering the AL cytotoxicity still remains unclear. Previously, we demonstrated that AL proteins internalize into mouse cardiomyocytes and localize into lysosomes; somatic mutations play a role on the internalization rates.<br/>Here, we extended this study following the internalization of AL proteins (full length (FL) and variable domain (VL)) into human cardiomyocytes (AC16 cell line) by real-time live-cell image analysis (IncuCyte<sup>TM</sup>). Our preliminary results show that Oregon Green labeled (OG)-AL-09 VL internalizes faster than its germline OG-κI O18/O8 VL, and both localize in perinuclear compartments. In addition, we studied the internalization of preformed amyloid fibrils and their effect when co-incubated with soluble protein. External aggregates surround the cell membrane and internalize more rapidly compared to soluble proteins. Interestingly, the presence of fibrils recruits soluble protein and dramatically accelerates its internalization. Furthermore, we used endocytic inhibitors to determine the endocytic mechanisms being used by AL proteins. Initial experiments using Dynasore and MitMAB indicate that soluble protein does not clearly internalize by a dynamin dependent endocytic pathway, which leads us to extend our studies to other mechanisms.<br/>This study would help us to understand the specific mechanism of AL light chain internalization, reflecting the different biophysical properties and somatic mutations of each AL protein. In addition, we expect to clarify whether or not the amyloid fibrils play a protective or detrimental role in the disease process, and then, elucidate the hypothesis that soluble protein internalization is required for cytotoxicity in AL amyloidosis.

Light chain internalizes into human cardiomyocytes in a Dynamin-independent way. Amyloid fibrils recruit soluble protein in media and accelerate its internalization

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.