Polymorphic fibrillation of the destabilized fourth fasciclin-1 domain mutant A546T of the Transforming growth factor-β-induced protein (TGFBIp) occurs through multiple pathways with different oligomeric intermediates.
Mutations in the transforming growth factor β-induced protein (TGFBIp) are linked to the development of corneal dystrophies in which abnormal protein deposition in the cornea leads to a loss of corneal transparency and ultimately blindness. Different mutations give rise to phenotypically distinct corneal dystrophies. Most mutations are located in the fourth fasciclin-1 domain (FAS1-4). The amino acid substitution A546T in the FAS1-4 domain is linked to the development of lattice corneal dystrophy with amyloid deposits in the superficial and deep stroma, classifying it as an amyloid disease. Here we provide a detailed description of the fibrillation of the isolated FAS1-4 domain carrying the A546T substitution. The A546T substitution leads to a significant destabilization of FAS1-4 and induces a partially folded structure with increased surface exposure of hydrophobic patches. The mutation also leads to two distinct fibril morphologies. Long straight fibrils composed of pure β-sheet structure are formed at lower concentrations, whereas short and curly fibrils containing a mixture of α-helical and β-sheet structures are formed at higher concentrations. The formation of short and curly fibrils is preceded by the formation of a small number of oligomeric species with high membrane permeabilization potential and rapid fibril formation. The long straight fibrils are formed more slowly and through progressively bigger oligomers that lose their membrane permeabilization potential as fibrillation proceeds beyond the lag phase. These different fibril classes and associated biochemical differences may lead to different clinical symptoms associated with the mutation.
Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark.
Maria
M
Andreasen
Søren B
SB
Nielsen
Kasper
K
Runager
Gunna
G
Christiansen
Niels Chr
NC
Nielsen
Jan J
JJ
Enghild
Daniel E
DE
Otzen
D019943:Amino Acid Substitution; D000682:Amyloid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D003315:Cornea / Q000378:metabolism / Q000473:pathology; D003317:Corneal Dystrophies, Hereditary / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016326:Extracellular Matrix Proteins / Q000737:chemistry* / Q000378:metabolism; D020125:Mutation, Missense; D010539:Permeability; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D016212:Transforming Growth Factor beta / Q000737:chemistry* / Q000378:metabolism; D000099222:betaIG-H3 Protein
D000682:Amyloid; D016326:Extracellular Matrix Proteins; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein