Santhoshkumar Puttur, Udupa Padmanabha, Murugesan Raju, Sharma K Krishna
Department of Ophthalmology, University of Missouri-Columbia School of Medicine, Columbia, MO 65212, USA.
J Biol Chem. 2008 Mar 28;283(13):8477-85. doi: 10.1074/jbc.M705876200. Epub 2008 Jan 28.
Analysis of aged and cataract lenses shows the presence of increased amounts of crystallin fragments in the high molecular weight aggregates of water-soluble and water-insoluble fractions. However, the significance of accumulation and interaction of low molecular weight crystallin fragments in aging and cataract development is not clearly understood. In this study, 23 low molecular mass (<3.5-kDa) peptides in the urea-soluble fractions of young, aged, and aged cataract human lenses were identified by mass spectroscopy. Two peptides, alphaB-(1-18) (MDIAIHHPWIRRPFFPFH) and betaA3/A1-(59-74) (SD(N)AYHIERLMSFRPIC), present in aged and cataract lens but not young lens, and a third peptide, gammaS-(167-178) (SPAVQSFRRIVE) present in all three lens groups were synthesized to study the effects of interaction of these peptides with intact alpha-, beta-, and gamma-crystallins and alcohol dehydrogenase, a protein used in aggregation studies. Interaction of alphaB-(1-18) and betaA3/A1-(59-74) peptides increased the scattering of light by beta- and gamma-crystallin and alcohol dehydrogenase. The ability of alpha-crystallin subunits to function as molecular chaperones was significantly reduced by interaction with alphaB-(1-18) and betaA3/A1-(59-74) peptides, whereas gammaS peptide had no effect on chaperone-like activity of alpha-crystallin. The betaA3/A1-(59-74 peptide caused a 5.64-fold increase in alphaB-crystallin oligomeric mass and partial precipitation. Replacing hydrophobic residues in alphaB-(1-18) and betaA3/A1-(59-74) peptides abolished their ability to induce crystallin aggregation and light scattering. Our study suggests that interaction of crystallin-derived peptides with intact crystallins could be a key event in age-related protein aggregation in lens and cataractogenesis.
对老年和白内障晶状体的分析表明，在水溶性和水不溶性部分的高分子量聚集体中存在数量增加的晶状体蛋白片段。然而，低分子量晶状体蛋白片段在衰老和白内障发展过程中的积累及相互作用的意义尚未完全明确。在本研究中，通过质谱鉴定了年轻、老年和老年白内障人晶状体尿素可溶部分中的23种低分子量（<3.5 kDa）肽段。两种肽段，即存在于老年和白内障晶状体而非年轻晶状体中的αB-(1-18)（MDIAIHHPWIRRPFFPFH）和βA3/A1-(59-74)（SD(N)AYHIERLMSFRPIC），以及存在于所有三组晶状体中的第三种肽段γS-(167-178)（SPAVQSFRRIVE）被合成出来，以研究这些肽段与完整的α-、β-和γ-晶状体蛋白以及醇脱氢酶（一种用于聚集研究的蛋白质）相互作用的影响。αB-(1-18)和βA3/A1-(59-74)肽段的相互作用增加了β-和γ-晶状体蛋白以及醇脱氢酶引起的光散射。与αB-(1-18)和βA3/A1-(59-74)肽段相互作用后，α-晶状体蛋白亚基作为分子伴侣发挥功能的能力显著降低，而γS肽段对α-晶状体蛋白的伴侣样活性没有影响。βA3/A1-(59-74)肽段使αB-晶状体蛋白的寡聚体质量增加了5.64倍并导致部分沉淀。替换αB-(1-18)和βA3/A1-(59-74)肽段中的疏水残基消除了它们诱导晶状体蛋白聚集和光散射的能力。我们的研究表明，晶状体蛋白衍生肽段与完整晶状体蛋白的相互作用可能是晶状体中与年龄相关的蛋白质聚集和白内障形成过程中的关键事件。
