Attanasio Francesco, Cataldo Sebastiano, Fisichella Salvatore, Nicoletti Silvia, Nicoletti Vincenzo Giuseppe, Pignataro Bruno, Savarino Anna, Rizzarelli Enrico
Institute of Biostructures and Bioimaging (IBB), CNR, 95125 Catania, Italy.
Biochemistry. 2009 Jul 14;48(27):6522-31. doi: 10.1021/bi900343n.
Mildly denaturing conditions induce bovine alpha-crystallin, the major structural lens protein, to self-assemble into fibrillar structures in vitro. The natural dipeptide l-carnosine has been shown to have potential protective and therapeutic significance in many diseases. Carnosine derivatives have been proposed as potent agents for ophthalmic therapies of senile cataracts and diabetic ocular complications. Here we report the inhibitory effect induced by the peptide (l- and d-enantiomeric form) on alpha-crystallin fibrillation and the almost complete restoration of the chaperone activity lost after denaturant and/or heat stress. Scanning force microscopy (SFM), thioflavin T, and a turbidimetry assay have been used to determine the morphology of alpha-crystallin aggregates in the presence and absence of carnosine. DSC and a near-UV CD assay evidenced that the structural precursors of amyloid fibrils are polypeptide chain segments that lack stable structural elements. Moreover, we have found a disassembling effect of carnosine on alpha-crystallin amyloid fibrils. Finally, we show the ability of carnosine to restore most of the lens transparency in organ-cultured rat lenses exposed to similar denaturing conditions that were used for the in vitro experiments.
轻度变性条件可诱导牛α-晶体蛋白（晶状体的主要结构蛋白）在体外自组装成纤维状结构。天然二肽L-肌肽已被证明在许多疾病中具有潜在的保护和治疗意义。肌肽衍生物已被提议作为治疗老年性白内障和糖尿病眼部并发症的有效药物。在此我们报告了该肽（L-和D-对映体形式）对α-晶体蛋白纤维化的抑制作用，以及在变性剂和/或热应激后丧失的伴侣活性几乎完全恢复。扫描力显微镜（SFM）、硫黄素T和比浊法已用于确定在有和没有肌肽存在的情况下α-晶体蛋白聚集体的形态。差示扫描量热法（DSC）和近紫外圆二色性（CD）分析证明，淀粉样纤维的结构前体是缺乏稳定结构元件的多肽链段。此外，我们发现肌肽对α-晶体蛋白淀粉样纤维有拆解作用。最后，我们展示了肌肽能够使在器官培养的大鼠晶状体中恢复大部分透明度，该晶状体暴露于与体外实验相同的变性条件下。
