Human phenotypically distinct TGFBI corneal dystrophies are linked to the stability of the fourth FAS1 domain of TGFBIp.
Mutations in the human TGFBI gene encoding TGFBIp have been linked to protein deposits in the cornea leading to visual impairment. The protein consists of an N-terminal Cys-rich EMI domain and four consecutive fasciclin 1 (FAS1) domains. We have compared the stabilities of wild-type (WT) human TGFBIp and six mutants known to produce phenotypically distinct deposits in the cornea. Amino acid substitutions in the first FAS1 (FAS1-1) domain (R124H, R124L, and R124C) did not alter the stability. However, substitutions within the fourth FAS1 (FAS1-4) domain (A546T, R555Q, and R555W) affected the overall stability of intact TGFBIp revealing the following stability ranking R555W>WT>R555Q>A546T. Significantly, the stability ranking of the isolated FAS1-4 domains mirrored the behavior of the intact protein. In addition, it was linked to the aggregation propensity as the least stable mutant (A546T) forms amyloid fibrils while the more stable variants generate non-amyloid amorphous deposits in vivo. Significantly, the data suggested that both an increase and a decrease in the stability of FAS1-4 may unleash a disease mechanism. In contrast, amino acid substitutions in FAS1-1 did not affect the stability of the intact TGFBIp suggesting that molecular the mechanism of disease differs depending on the FAS1 domain carrying the mutation.
Center for Insoluble Protein Structures, Department of Molecular Biology, Aarhus University, 8000 Aarhus, Denmark.
Kasper
K
Runager
Rajiv V
RV
Basaiawmoit
Taru
T
Deva
Maria
M
Andreasen
Zuzana
Z
Valnickova
Charlotte S
CS
Sørensen
Henrik
H
Karring
Ida B
IB
Thøgersen
Gunna
G
Christiansen
Jarl
J
Underhaug
Torsten
T
Kristensen
Niels Chr
NC
Nielsen
Gordon K
GK
Klintworth
Daniel E
DE
Otzen
Jan J
JJ
Enghild
D019943:Amino Acid Substitution; D000682:Amyloid / Q000235:genetics / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism*; D003317:Corneal Dystrophies, Hereditary / Q000235:genetics / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D020125:Mutation, Missense; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D000099222:betaIG-H3 Protein
D000682:Amyloid; D016326:Extracellular Matrix Proteins; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein