Unusual duplication mutation in a surface loop of human transthyretin leads to an aggressive drug-resistant amyloid disease

Elena S. Klimtchuk, Tatiana Prokaeva, Nicholas M. Frame, Hassan A. Abdullahi, Brian Spencer, Surendra Dasari, Haili Cui, John L. Berk, Paul J. Kurtin, Lawreen H. Connors, Olga Gursky

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Transthyretin (TTR) is a globular tetrameric transport protein in plasma. Nearly 140 single amino acid substitutions in TTR cause life-threatening amyloid disease. We report a one-of-a-kind pathological variant featuring a Glu51, Ser52 duplication mutation (Glu51_Ser52dup). The proband, heterozygous for the mutation, exhibited an unusually aggressive amyloidosis that was refractory to treatment with the small-molecule drug diflunisal. To understand the poor treatment response and expand therapeutic options, we explored the structure and stability of recombinant Glu51_Ser52dup. The duplication did not alter the protein secondary or tertiary structure but decreased the stability of the TTR monomer and tetramer. Diflunisal, which bound with near-micromolar affinity, partially restored tetramer stability. The duplication had no significant effect on the free energy and enthalpy of diflunisal binding, and hence on the drug–protein interactions. However, the duplication induced tryptic digestion of TTR at near-physiological conditions, releasing a C-terminal fragment 49–129 that formed amyloid fibrils under conditions in which the full-length protein did not. Such C-terminal fragments, along with the full-length TTR, comprise amyloid deposits in vivo. Bioinformatics and structural analyses suggested that increased disorder in the surface loop, which contains the Glu51_Ser52dup duplication, not only helped generate amyloid-forming fragments but also decreased structural protection in the amyloidogenic residue segment 25–34, promoting misfolding of the full-length protein. Our studies of a unique duplication mutation explain its diflunisal-resistant nature, identify misfolding pathways for amyloidogenic TTR variants, and provide therapeutic targets to inhibit amyloid fibril formation by variant TTR.

Original languageEnglish (US)
Pages (from-to)E6428-E6436
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number28
DOIs
StatePublished - Jul 10 2018

Keywords

  • Kinetic stability
  • Protein misfolding disease
  • Protein structural disorder
  • Proteolysis
  • Small-molecule drug binding

ASJC Scopus subject areas

  • General

Fingerprint Dive into the research topics of 'Unusual duplication mutation in a surface loop of human transthyretin leads to an aggressive drug-resistant amyloid disease'. Together they form a unique fingerprint.

Cite this