Mass spectrometry characterization of light chain fragmentation sites in cardiac AL amyloidosis: Insights into the timing of proteolysis

Francesca Lavatelli, Giulia Mazzini, Stefano Ricagno, Federica Iavarone, Paola Rognoni, Paolo Milani, Mario Nuvolone, Paolo Swuec, Serena Caminito, Masayoshi Tasaki, Antonio Sanjuan Chaves, Andrea Urbani, Giampaolo Merlini, Giovanni Palladini

Research output: Contribution to journalArticlepeer-review

Abstract

Amyloid fibrils are polymeric structures originating from aggregation of misfolded proteins. In vivo, proteolysis may modulate amyloidogenesis and fibril stability. In light chain (AL) amyloidosis, fragmented light chains (LCs) are abundant components of amyloid deposits; however, site and timing of proteolysis are debated. Identification of the N and C termini of LC fragments is instrumental to understanding involved processes and enzymes. We investigated theN and C terminome of the LC proteoforms in fibrils extracted from the hearts of two AL cardiomyopathy patients, using a proteomic approach based on derivatization of N- and C-terminal residues, followed by mapping of fragmentation sites on the structures of native and fibrillar relevant LCs. We provide the first high-specificity map of proteolytic cleavages in natural AL amyloid. Proteolysis occurs both on the LC variable and constant domains, generating a complex fragmentation pattern. The structural analysis indicates extensive remodeling by multiple proteases, largely taking place on poorly folded regions of the fibril surfaces. This study adds novel important knowledge on amyloid LC processing: although our data do not exclude that proteolysis of native LC dimers may destabilize their structure and favor fibril formation, the data show that LC deposition largely precedes the proteolytic events documentable in mature AL fibrils.

Original languageEnglish
Pages (from-to)16572-16584
Number of pages13
JournalJournal of Biological Chemistry
Volume295
Issue number49
DOIs
Publication statusPublished - Dec 4 2020

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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