Why the study?
Do amyloidogenic cardiotoxic immunoglobulin light chains establish nonphysiologic protein-protein interactions and cause mitochondrial damage in human cardiac cells compared to noncardiotoxic light chains?
Do amyloidogenic cardiotoxic immunoglobulin light chains establish nonphysiologic protein-protein interactions and cause mitochondrial damage in human cardiac cells compared to noncardiotoxic light chains?
Cardiotoxic immunoglobulin light chains in AL amyloidosis directly interact with mitochondrial proteins in cardiac cells, causing ultrastructural damage and providing new mechanistic insights into AL cardiomyopathy.
Does not support clinical translation; leaves open mitochondrial interactions as a mechanism in AL cardiomyopathy.
In immunoglobulin (Ig) light-chain (LC) (AL) amyloidosis, AL deposition translates into life-threatening cardiomyopathy. Clinical and experimental evidence indicates that soluble cardiotoxic LCs are themselves harmful for cells, by which they are internalized. Hypothesizing that interaction of soluble cardiotoxic LCs with cellular proteins contributes to damage, we characterized their interactome in cardiac cells. LCs were purified from patients with AL amyloidosis cardiomyopathy or multiple myeloma without amyloidosis (the nonamyloidogenic/noncardiotoxic LCs served as controls) and employed at concentrations in the range observed in AL patients' sera. A functional proteomic approach, based on direct and inverse coimmunoprecipitation and mass spectrometry, allowed identifying LC-protein complexes. Findings were validated by colocalization, fluorescence lifetime imaging microscopy (FLIM)-fluorescence resonance energy transfer (FRET), and ultrastructural studies, using human primary cardiac fibroblasts (hCFs) and stem cell-derived cardiomyocytes. Amyloidogenic cardiotoxic LCs interact in vitro with specific intracellular proteins involved in viability and metabolism. Imaging confirmed that, especially in hCFs, cardiotoxic LCs (not controls) colocalize with mitochondria and spatially associate with selected interactors: mitochondrial optic atrophy 1-like protein and peroxisomal acyl-coenzyme A oxidase 1 (FLIM-FRET efficiencies 11 and 6%, respectively). Cardiotoxic LC-treated hCFs display mitochondrial ultrastructural changes, supporting mitochondrial involvement. We show that cardiotoxic LCs establish nonphysiologic protein-protein contacts in human cardiac cells, offering new clues on the pathogenesis of AL cardiomyopathy.
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Lavatelli et al. (2015) studied this question.
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