Trans -Suppression of Misfolding in an Amyloid Disease

Abstract

The transthyretin (TTR) amyloid diseases, representative of numerous misfolding disorders, are of considerable interest because there are mutations that cause or suppress disease. The Val30 --> Met30 (V30M) TTR mutation is the most prevalent cause of familial amyloid polyneuropathy in heterozygotes, whereas a Thr119 --> Met119 (T119M) mutation on the second TTR allele protects V30M carriers from disease. Here, we show that the incorporation of one or more T119M TTR subunits into a predominantly V30M tetramer strongly stabilized the mixed tetramer against dissociation. Dissociation is required for amyloid formation, so these findings provide a molecular explanation for intragenic trans-suppression of amyloidosis. The data also suggest a potential therapeutic strategy, provide insight into tissue-specific deposition and amyloid composition, and support the validity of the amyloid hypothesis in human disease.

Discovery and characterization of a mammalian amyloid disaggregation activity

“…[1][2][3][4][5][6][7][8][9][10]23,[33][34][35][36][37][43][44][45] The prevention of amyloidogenesis by a kinetic stabilizer approach has recently been demonstrated to halt the progression of nervous system degeneration in familial amyloid polyneuropathy associated with the amyloidogenesis of transthyretin. Thus, it is logical that the removal of protein aggregates would be crucial for protein homeostasis.…”

“…Many age-related diseases (including Alzheimer's disease, the transthyretin amyloidoses, Parkinson's disease, Huntington's disease, and familial amyloidosis of Finnish type) are associated with amyloidogenesis, a process by which proteins misassemble or misfold and misassemble into both soluble and insoluble cross-b-sheet fibrillar aggregates called amyloid. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Amyloid is toxic when applied exogenously to or when formed within cultured cells. [19][20][21][22][23][24][25][26][27][28][29][30][31][32] Mouse and C. elegans models of amyloid diseases show that the cytotoxicity associated with amyloidogenesis increases with organismal age.…”

Clinicopathological features of senile systemic amyloidosis: an ante- and post-mortem study

“…14 This chemical compound reportedly prevented dissociation of native transthyretin tetramers into monomers, which is a key factor in promoting amyloid fibrillogenesis. 15 Effective medical treatment of patients with transthyretin amyloidosis requires an accurate diagnosis with the use of various examinations, including histopathology, echocardiography, scintigraphy, genetic testing, mass spectrometry, and serum protein analyses. 6 Histopathological examinations have a critical role in obtaining direct evidence of amyloid deposits and determining the type of amyloid-causing protein.…”

Quantification of the Thermodynamically Linked Quaternary and Tertiary Structural Stabilities of Transthyretin and Its Disease-Associated Variants: The Relationship between Stability and Amyloidosis

“…The thermodynamic linkage of the TTR tetramer dissociation and monomer unfolding equilibria make it challenging to extract thermodynamic data from the urea denaturation curves (7). How disease-associated mutations influence quaternary and tertiary structural stability and how folding and tetramerization energetics correlate with disease phenotypes is some of the valuable information sought herein.Generally, rate-limiting tetramer dissociation enables monomer misfolding that is required for TTR to form amyloid (5,(16)(17)(18)(19)(20)(21)(22), by a very efficient downhill polymerization process (23).Most of the disease-associated TTR mutations form normal tetrameric structures based on crystallographic analysis (24) and function normally, including transporting and binding thyroid hormone and holo retinol binding protein in the plasma and cerebrospinal fluid (CSF). Thus, it is the propensity of these variants to misfold, not their inability to fold and function, that results in disease through a gain of toxic function mechanism(s), the details of which remain elusive but appear to be associated with TTR aggregation (7,17,18,25,26).…”

“…Two such small molecules are currently being tested as agents to ameliorate FAP in placebo-controlled clinical trials (see http://www.clinicaltrials.gov/). This approach is expected to be efficacious because kinetic stabilization of tetrameric transthyretin incorporating disease-associated subunits by interallelic trans suppression (the incorporation of T119M TTR subunits) ameliorates FAP symptoms (17,18,20,35).Since TTR tetramer dissociation, partial monomer denaturation and amyloidogenesis are associated with several familial gain-of-function proteotoxicity diseases, we set out to examine [36][37][38][39][40]. Systematic urea denaturation studies were therefore carried out as a function of the concentration of TTR.…”