The structures of R124H and R555W TGFBIp suggest a direct role of the mutated residues in the aggregation of TGFBIp in granular corneal dystrophy

ABSTRACT: Protein aggregation in the outermost layers of the cornea, leading to cloudy vision and in severe cases blindness, is linked to mutations in the extracellular matrix protein, transforming growth factor-β-induced protein (TGFBIp). Among the most frequent disease-causing mutations are R124H and R555W, both associated with granular corneal dystrophy (GCD) characterized by early-onset amorphous aggregation. The molecular mechanisms of protein aggregation in GCD are largely unknown. In this study, we determined the crystal structures of R124H and R555W. Whereas no structural changes of mutated monomeric TGFBIp can explain its aggregation propensity, the two mutations facilitate a new dimer interface in the crystal packing, not appearing in the wild-type structure. The interface in both R124H and R555W structures are centered on residue 124 in one TGFBIp molecule and 555 in a second TGFBIp molecule. This unique interface of R124H and R555W is not compatible with arginines at positions 124 and 555 as seen in wild-type TGFBIp. Hence, this intermolecular interaction may underlie the similar aggregation behavior exhibited by the two TGFBIp mutants in vivo. Using cross-linking mass spectrometry, we identified and characterized a dimer of TGFBIp wild-type and mutants in solution. The soluble dimers also involve interactions between the N- and C-terminal domains of two TGFBIp molecules but is not identical to the crystal packing dimer interface involving R124H and R555W. Targeting of the crystal packing dimer interface might offer new opportunities for therapeutic intervention to treat patients with GCD.

INSTRUMENT(S): Orbitrap Eclipse

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Nadia Sukusu Nielsen  

LAB HEAD: Jan J. Enghild

PROVIDER: PXD022976 | Pride | 2021-09-08

REPOSITORIES: Pride