Cataract-causing G91del mutant destabilised βA3 heteromers formation linking with structural stability and cellular viability

• Published in: British journal of ophthalmology Vol. 106; no. 10; pp. 1473 - 1478
• Main Authors: Wang, Huaxia, Tian, Qing, Xu, Jingjie, Xu, Wanyue, Yao, Ke, Chen, Xiangjun
• Format: Journal Article
• Language: English
• Published: BMA House, Tavistock Square, London, WC1H 9JR BMJ Publishing Group Ltd 01.10.2022; BMJ Publishing Group LTD
• Subjects: Apoptosis; biochemistry; Cataracts; Chromatography; experimental – laboratory; Flow cytometry; genetics; Laboratory science; lens and zonules; Mutation; Proteins; Simulation; Spectrum analysis; China; Japan
• ISSN: 0007-1161; 1468-2079
• DOI: 10.1136/bjophthalmol-2021-320033

Background/aimsCongenital cataracts, which are genetically heterogeneous eye disorders, result in visual loss in childhood around the world. CRYBA1/BA3 serves as an abundant structural protein in the lens, and forms homomers and heteromers to maintain lens transparency. In previous study, we identified a common cataract-causing mutation, βA3-glycine at codon 91 (G91del) (c.271–273delGAG), which deleted a highly conserved G91del and led to perinuclear zonular cataract. In this study, we aimed to explore the underlying pathogenic mechanism of G91del mutation.MethodsProtein purification, size-exclusion chromatography, spectroscopy and molecular dynamics simulation assays were used to investigate the effects on the heteromers formation and the protein structural properties of βA3-crystallin caused by G91del mutation. Intracellular βA3-G91del overexpression, MTT (3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide) and cell apoptosis were used to investigate the cellular functions of βA3-G91del.ResultsβA3-crystallin and βB2-crystallin could form heteromers, which have much more stable structures than βA3 homomers. Interestingly, βA3/βB2 heteromers improved their resistance against the thermal stress and the guanidine hydrochloride treatment. However, the pathogenic mutation βA3-G91del destroyed the interaction with βB2, and thereby decreased its structural stability as well as the resistance of thermal or chemical stress. What’s more, the βA3-G91del mutation induced cell apoptosis and escaped from the protection of βB2-crystallin.ConclusionsβA3/βB2 heteromers play an indispensable role in maintaining lens transparency, while the βA3-G91del mutation destabilises heteromers formation with βB2-crystallin, impairs cellular viability and induces cellular apoptosis. These all might contribute to cataract development.