Light chain (AL) amyloidosis is characterized by the misfolding of immunoglobulin light chains, accumulating as amyloid fibrils in vital organs. Multiple reports have indicated that amyloidogenic light chains internalize into a variety of cell types, but these studies used urine-derived proteins without indicating any protein sequence information. As a result, the role of somatic mutations in amyloidogenic protein internalization has not been yet studied. We characterized the internalization of AL-09, an AL amyloidosis protein into mouse cardiomyocytes. We also characterized the internalization of the germline protein κI O18/O8, devoid of somatic mutations, and three AL-09 restorative mutations (I34N, Q42K, and H87Y) previously characterized for their role in protein structure, stability, and amyloid formation kinetics. All proteins shared a common internalization pathway into lysosomal compartments. The proteins caused different degrees of lysosomal expansion. Oregon green (OG) labeled AL-09 showed the most rapid internalization, while OG-Q42K presented the slowest rate of internalization.
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