Oxidative stress is an important factor triggering the aggregation of cataract-causing γ-crystallin mutants

【作者】 赵维杰； 闫永彬；

【机构】 State Key Laboratory of Biomembrane and Membrane Biotechnology,School of Life Sciences, Tsinghua University；

【摘要】 Crystallins are the major structural proteins in mammalian lens and their stability is essentialfor the lens to maintain transparency throughout one individual’s lifespan.In normallens,the crystallins are protected from oxidization by the high concentration of glutathione(GSH)within the lens.While in the case of aging cataract lens,the GSH concentrationis decreased and proteins including crystallins undergo oxidization and lose the abilityto maintain stable and soluble.Considering that many cataract-causing mutations are substituted by oxidable residues,here we asked whether oxidization plays a role in the onset of congenital cataract.Thisproblem was addressed by studying the behaviors ofγC andγD crystallin and variouscataract-causing mutatants under oxidative conditions.Our results showed that under oxidativestress,theγD mutants R14C and G60C formed dimer via intermolecular disulfidebond,while the WTγD and the mutant R58H didn’t.All proteins showed decreasedthermo stability and the impairment was ever serious.R58H showed no significant differencewith WT protein in thermo stability in absence of oxidization,while became lessstable than WT after oxidization.We further found that theγC proteins were more sensitiveto oxidization thenγD proteins.Both the WT and mutated proteins were crosslinkedafter oxidization.All the cataract-causing mutants exhibited a much lower thermo stabilitythan the WT protein.Our results suggested that the cataract-causing mutations significantlyincreased the sensitivity to oxidative stress.Oxidization might be an importantfactors involved in the progression of congenital cataract caused by inherited mutations.更多还原

【Abstract】 Crystallins are the major structural proteins in mammalian lens and their stability is essentialfor the lens to maintain transparency throughout one individual’s lifespan.In normallens,the crystallins are protected from oxidization by the high concentration of glutathione(GSH)within the lens.While in the case of aging cataract lens,the GSH concentrationis decreased and proteins including crystallins undergo oxidization and lose the abilityto maintain stable and soluble.Considering that many cataract-causing mutations are substituted by oxidable residues,here we asked whether oxidization plays a role in the onset of congenital cataract.Thisproblem was addressed by studying the behaviors ofγC andγD crystallin and variouscataract-causing mutatants under oxidative conditions.Our results showed that under oxidativestress,theγD mutants R14C and G60C formed dimer via intermolecular disulfidebond,while the WTγD and the mutant R58H didn’t.All proteins showed decreasedthermo stability and the impairment was ever serious.R58H showed no significant differencewith WT protein in thermo stability in absence of oxidization,while became lessstable than WT after oxidization.We further found that theγC proteins were more sensitiveto oxidization thenγD proteins.Both the WT and mutated proteins were crosslinkedafter oxidization.All the cataract-causing mutants exhibited a much lower thermo stabilitythan the WT protein.Our results suggested that the cataract-causing mutations significantlyincreased the sensitivity to oxidative stress.Oxidization might be an importantfactors involved in the progression of congenital cataract caused by inherited mutations.更多还原