Beta A3/A1–Crystallin sequence SNAYHIERLMSFRPIC present in aged and cataract human lenses can modulate protein aggregation.

Abstract

Abstract: : Purpose: The presence of increasing quantities of crystallin fragments in aged and cataract human lenses has been known for some time. We have isolated several crystallin fragments (Mr <3 kDa) from normal and cataract human lenses. The purpose of this study was to investigate the properties of one of those peptides, SNAYHIERLMSFRPIC, betaA3/A1 sequence 59–74. Methods: Beta–L–crystallin purified from bovine lenses was subjected to denaturation at 37^o C or 55^o C in presence and absence of betaA3/A1 peptide and the aggregation was monitored as light scattering at 360 nm. Alpha crystallin was also included in some assays to determine whether the peptide–induced aggregation can be suppressed by the presence of a chaperone protein. Following the aggregation assay the precipitate was collected and analyzed by HPLC. To confirm the interaction of beta A3/A1 peptide with denaturing beta–L–crystallins, sulfo–SBED modified peptide was allowed to complex with beta–L–crystallin at 55^o C, photolyzed and analyzed by SDS–PAGE and westernblot techniques. Results: Beta A3/A1 peptide increased the heat–induced aggregation of beta–L–crystallins at 37^o C and 55^o C in a concentration dependent manner. 75 µg of the peptide increased the aggregation of 100 µg of beta–L–crystallin at 55^o C by 100%. At 37^oC, the presence of 100 µg of the peptide in the assay mixture resulted in a 5 fold increase in aggregation of 100 µg of beta–L–crystallin. Increased peptide–induced aggregation of beta–L–crystallin was also observed when a known amount of alpha–crystallin, that would normally suppress the aggregation of beta–L–crystallin, was included in the assay. The sulfo–SBED labeling study and the HPLC analysis of the precipitate from reaction mixture showed that the increased aggregation of beta–L–crystallin was due to its interaction with betaA3/A1–peptide. Conclusions:These results show that the in vivo generated beta A3/A1–crystallin peptide has the ability to interact with denaturing beta–L–crystallins and increase their insolubilization. This is the first evidence of the modulation of beta–L–crystallin aggregation by a peptide (SNAYHIERLMSFRPIC) present in vivo.

Keywords: crystallins • cataract • chaperones