1. Nanobody interaction unveils structure, dynamics and proteotoxicity of the Finnish-type amyloidogenic gelsolin variant.
- Author
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Giorgino T, Mattioni D, Hassan A, Milani M, Mastrangelo E, Barbiroli A, Verhelle A, Gettemans J, Barzago MM, Diomede L, and de Rosa M
- Subjects
- Amino Acid Substitution genetics, Amyloid genetics, Amyloid metabolism, Amyloidosis metabolism, Amyloidosis, Familial genetics, Amyloidosis, Familial metabolism, Animals, Caenorhabditis elegans, Calcium chemistry, Calcium metabolism, Corneal Dystrophies, Hereditary metabolism, Crystallography, X-Ray, Finland, Furin chemistry, Furin metabolism, Gelsolin toxicity, Humans, Models, Molecular, Molecular Dynamics Simulation, Mutant Proteins chemistry, Mutant Proteins genetics, Mutant Proteins metabolism, Mutant Proteins toxicity, Protein Binding, Protein Conformation drug effects, Protein Folding drug effects, Proteolysis drug effects, Single-Domain Antibodies chemistry, Single-Domain Antibodies pharmacology, Amyloid toxicity, Amyloidosis genetics, Corneal Dystrophies, Hereditary genetics, Gelsolin chemistry, Gelsolin genetics, Gelsolin metabolism, Single-Domain Antibodies metabolism
- Abstract
AGel amyloidosis, formerly known as familial amyloidosis of the Finnish-type, is caused by pathological aggregation of proteolytic fragments of plasma gelsolin. So far, four mutations in the gelsolin gene have been reported as responsible for the disease. Although D187N is the first identified variant and the best characterized, its structure has been hitherto elusive. Exploiting a recently-developed nanobody targeting gelsolin, we were able to stabilize the G2 domain of the D187N protein and obtained, for the first time, its high-resolution crystal structure. In the nanobody-stabilized conformation, the main effect of the D187N substitution is the impairment of the calcium binding capability, leading to a destabilization of the C-terminal tail of G2. However, molecular dynamics simulations show that in the absence of the nanobody, D187N-mutated G2 further misfolds, ultimately exposing its hydrophobic core and the furin cleavage site. The nanobody's protective effect is based on the enhancement of the thermodynamic stability of different G2 mutants (D187N, G167R and N184K). In particular, the nanobody reduces the flexibility of dynamic stretches, and most notably decreases the conformational entropy of the C-terminal tail, otherwise stabilized by the presence of the Ca
2+ ion. A Caenorhabditis elegans-based assay was also applied to quantify the proteotoxic potential of the mutants and determine whether nanobody stabilization translates into a biologically relevant effect. Successful protection from G2 toxicity in vivo points to the use of C. elegans as a tool for investigating the mechanisms underlying AGel amyloidosis and rapidly screen new therapeutics., (Copyright © 2019 Elsevier B.V. All rights reserved.)- Published
- 2019
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