Epigallocatechin gallate remodels fibrils of Lattice Corneal Dystrophy protein, facilitating proteolytic degradation and preventing formation of membrane-permeabilizing species

Lattice Corneal Dystrophy is associated with painful recurrent corneal erosions and amyloid corneal opacities induced by transforming growth factor β induced protein (TGFBIp) that impairs vision. The exact mechanism of amyloid fibril formation in Corneal Dystrophy is unknown but has been associated with destabilizing mutations in the fourth fasciclin 1 (Fas1-4) domain of TGFBIp. The green tea compound Epigallo-catechin gallate (EGCG) has been found to inhibit fibril formation of various amyloidogenic proteins in vitro. In this study we investigated the effect of EGCG as a potential treatment in Lattice Corneal Dystrophy (LCD) using Fas1-4 with the naturally occurring LCD-inducing A546T mutation. A few molar excess of EGCG were found to inhibit fibril formation in vitro by directing Fas1-4 A546T into stable EGCG-bound protein oligomers. Incubation with two molar equivalent EGCG led to a 4-fold reduction in the aggregates' membrane disruptive potential, potentially indicative of significantly lower cytotoxicity with regards to corneal erosions. EGCG did not induce oligomer formation by wildtype Fas1-4, indicating that treatment with EGCG would not interfere with the native function of the wild-type protein. Addition of EGCG to 10-day old fibrils reduced fibril content in a dose-dependent manner. Proteinase K was found to reduce the light scattering of non-treated fibrils by 31%, but reduced that of fibrils treated with eight molar equivalents of EGCG by 85%. This suggests that EGCG remodeling of fibril structure can facilitate aggregate removal by endogenous proteases and thus alleviate the protein deposits' light scattering symptoms.