Biochemistry Division, National Institute of Nutrition, Hyderabad, 500007, India.
School of Chemistry, University of Hyderabad, Hyderabad, 500046, India.
Biochemistry (Mosc). 2022 Feb;87(2):131-140. doi: 10.1134/S0006297922020055.
Loss of eye lens transparency due to cataract is the leading cause of blindness all over the world. While aggregation of lens crystallins is the most common endpoint in various types of cataracts, chaperone-like activity (CLA) of α-crystallin preventing protein aggregation is considered to be important for maintaining the eye lens transparency. Osmotic stress due to increased accumulation of sorbitol under hyperglycemic conditions is believed to be one of the mechanisms for diabetic cataract. In addition, compromised CLA of α-crystallin in diabetic cataract has been reported. However, the effect of sorbitol on the structure and function of α-crystallin has not been elucidated yet. Hence, in the present exploratory study, we described the effect of varying concentrations of sorbitol on the structure and function of α-crystallin. Alpha-crystallin purified from the rat lens was incubated with varying concentrations of sorbitol in the dark under sterile conditions for up to 5 days. At the end of incubation, structural properties and CLA were evaluated by spectroscopic methods. Interestingly, different concentrations of sorbitol showed contrasting results: at lower concentrations (5 and 50 mM) there was a decrease in CLA and subtle alterations in secondary and tertiary structure but not at higher concentrations (500 mM). Though, these results shed a light on the effect of sorbitol on α-crystallin structure-function, further studies are required to understand the mechanism of the observed effects and their implication to cataractogenesis.
由于白内障导致的眼睛晶状体透明度丧失是全世界失明的主要原因。虽然晶状体蛋白聚集是各种类型白内障的最常见终点，但α-晶状体蛋白的伴侣样活性 (CLA) 可防止蛋白质聚集，被认为对维持眼睛晶状体透明度很重要。高血糖条件下山梨醇积累导致的渗透应激被认为是糖尿病性白内障的机制之一。此外，据报道糖尿病性白内障中α-晶状体蛋白的 CLA 受损。然而，山梨醇对α-晶状体蛋白结构和功能的影响尚未阐明。因此，在本探索性研究中，我们描述了山梨醇浓度变化对α-晶状体蛋白结构和功能的影响。在黑暗无菌条件下，将从大鼠晶状体中纯化的α-晶状体蛋白与不同浓度的山梨醇孵育长达 5 天。孵育结束时，通过光谱方法评估结构特性和 CLA。有趣的是，不同浓度的山梨醇表现出相反的结果：在较低浓度（5 和 50mM）时，CLA 下降，二级和三级结构发生细微改变，但在较高浓度（500mM）时则没有。尽管这些结果揭示了山梨醇对α-晶状体蛋白结构-功能的影响，但需要进一步的研究来了解观察到的效应的机制及其对白内障形成的影响。
