METHODS: TTase KO model was established in this laboratory. TTase KO and WT mice were examined and the lens opacity was classified by using a slit lamp. Each lens was homogenized in lysis buffer and processed for measurement of glutathione(GSH)level. Examination of Protein-GSH mixed disulfides(PSSG)formation in the lens by Western blot analysis. Immunoprecipitation was used to identify the proteins formed PSSG. Dethiolation of lens proteins was carried out using purified recombinant human lens TTase(RHLT).

RESULTS: The slit lamp examination showed an age-dependent nuclear cataract development in both eyes of the WT and TTase KO mice. The onset of cataract was 4mo in the KO mice and 9mo in the WT mice. The GSH loss showed in both groups during aging and was prominent in the TTase KO mice after 9mo old. PSSG in the lenses of both groups showed progressive elevation, whereas the lenses of the KO group had a higher level of PSSG after 9mo. These GSH-conjugated proteins were confirmed as actin and glyceraldehyes 3-phosphate dehydrogenase(GAPDH)by immunoprecipitation and they could be eliminated when the homogenates were treated with RHLT.

CONCLUSION: The results showed that deletion of TTase gene in the mouse could lead to an early age-dependent cataract formation and the PSSG formation in these lenses appeared to link directly to lens opacity. The PSSG could be dethiolated by TTase. This data strengthens that TTase plays an essential role in maintaining lens clarity.