Congenital cataract-causing mutation βB1-L116P is prone to amyloid fibrils aggregation and protease degradation with low structural stability

Congenital cataract, a common disease with lens opacification, causes blindness in the newborn worldwide and is mainly caused by abnormal aggregation of crystallin. As the main structural protein in the mammalian lens, psicrystallin has an important role in the maintenance of lens transparency. Recently, the L116P mutation in beta B1-CRY was found in a Chinese family with congenital nuclear cataracts, while its underlying pathogenic mechanism remains unclear. In the current study, the beta B1 wild-type protein was purified, and the mutated form, beta B1-CRY, was examined for examining the effect on structural stability and susceptibility against environmental stresses. Our results reveal low solubility and structural stability of beta B1-L116P at physiological temperature, which markedly impaired the protein structure and the oligomerization of beta B1-crystallin. Under guanidine hydrochloride-induced denaturing conditions, beta B1-L116P mutation perturbed the protein unfolding process, making it prone to amyloid fibrils aggregation. More importantly, the L116P mutation increased susceptibility of beta B1-crystallin against UV radiation. beta B1-L116P overexpression led to the formation of more serious intracellular aggresomes under UV radiation or oxidative stress. Furthermore, the beta B1-L116P mutation increased the sensitivity to the proteolysis process. These results indicate that the low structural stability, susceptibility to amyloid fibrils aggregation, and protease degradation of beta B1-L116P may contribute to cataract development and associated symptoms.

Automated summary

Congenital cataract, caused by abnormal aggregation of crystallin, is a common disease that leads to blindness in newborns worldwide. The L116P mutation in β B1-CRY affects the protein's structural stability, susceptibility to amyloid fibrils aggregation, and protease degradation, potentially contributing to cataract development and associated symptoms.