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Novel mitochondrial protein interactors of immunoglobulin light chains causing heart amyloidosis
Author(s) -
Lavatelli Francesca,
Imperiini Esther,
Orrù Stefania,
Rogi Paola,
Sarnataro Daniela,
Palladini Giuseppina,
Malpasso Giuseppe,
Soriano Maria Eugenia,
Di Fonzo Andrea,
Valentini Veronica,
Gnecchi Massimiliano,
Perlini Stefano,
Salvatore Francesco,
Merlini Giampaolo
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.15-272179
Subject(s) - al amyloidosis , microbiology and biotechnology , colocalization , mitochondrion , chemistry , immunoprecipitation , immunoglobulin light chain , biochemistry , biology , antibody , gene , immunology
ABSTRACT 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.—Lavatelli, F., Imperlini, E., Orrù, S., Rognoni, P., Sarnataro, D., Palladini, G., Malpasso, G., Soriano, M. E., Di Fonzo, A., Valentini, V., Gnecchi, M., Perlini, S., Salvatore, F., Merlini, G. Novel mitochondrial protein interactors of immunoglobulin light chains causing heart amyloidosis. FASEB J. 29, 4614‐4628 (2015). www.fasebj.org