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·α-crystallin is the predominant structural protein in the lens.lt is a member of small heat shock proteins ( sHSPs) which has the common functions of HSPs.lt also has anti-apoptotic activity etc.Recently, it has been proved to combine with the cellular membrane of retinal ganglion cells ( RGCs ) to enhance the survival of RGCs and the regeneration of axons, thereby partly restore visual function.But we haven’t come to a unified conclusion of the mechanism.This review is focused on structure and functions of α-crystallin, the protection function and mechanism of α-crystallin towards RGCs after the optic nerve injury.
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αB-crystallin is the structural protein of vertebrate lens, w hich is w idely expressed in non-lens tissue. As one of the heat shock protein fam ily m em bers,αB-crystallin possesses biological proper-ties of m olecular chaperones and anti-apoptotic effects. Multi-factor injuries, such as retinopathy, inflam-m ation and nervous system diseases, have a closely relationship w ith αB-crystallin. T his paper review s the research progress of the expression and m echanism ofαB-crystallin in retina and extraocular tissues and organs.
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Background Ultraviolet radiation is one of factors of the formation of age-related cataract.Indole-3-carbinol(I3C) is a plant chemical material with inhibitory effect on oxidative-induced cell damage and formation of amyloid fibrils,and the oxidative damage and amyloid fibrils are associated with cataract.However,the relationship between I3C and α-crystallin is in study. Objective This study was to evaluate the effects of ultraviolet-B laser irradiation on the secondary structure of α-crystallin and to explore the protection of I3C to chaperone activity of α-crystallin. Methods The fresh eyeballs were obtained from 1-year-old cattle to prepare the purified lens α-crystallin by gel chromatography.α-Crystallin was isolated from cattle lenses using gel chromatography.The purified α-crystallin was collected using fast protein liquid chromatography ( FPLC ) and exposed to 1:308 nmultraviolet-B at different irradiation intensities ( 23.75,118.75,475.00,1187.50,2375.00,4750.00,11 875.00,23 750.00 mJ/cm2 ) and then to ultraviolet-B 2:308 nm with irradiation intensities of 28 535.00,6730.00,3435.00,1910.00,1040.00 mJ/cm2.Ultraviolet-absorbance spectra,tryptophan fluorescence and N-formylkynurenine (N-FK)fluorescence spectra of both irradiated and non-irradiated α-crystallin were measured.I3C at the concentrations of 50 μmol/L and 100 μmoL/L were added to the α-crystallin solution to perform a catalase (CAT) thermal aggregation to confirm the chaperone activity of the α-crystallin,and the α-crystallin solution without any I3C was used as control.The ratios of A360 between various intervene groups with control group were calculated using spectrophotometry.Results The A280 values of the α-crystallin declined to 10％ at the ultraviolet-B irradiation intensity of 1187.5 mJ/cm2 and that at the intensity of 23.75 J/cm2 lowed to 2％.A negative correlation was seen between the ultraviolet-B irradiation intensity and the A280 value of the α-crystallin (R2=0.925 ) and a positive correlation was found between ultraviolet-B with N-FK ( R2 =0.949 ).Ultraviolet-B irradiation intensity showed a negative correlation with Trp fluorescence intensity (R2 =0.996 ).CAT hot condensed experiment revealed that after addition of different concentrations of indole-3-carbinol,the relative A360 values at various ultraviolet-B irradiation group were significantly higher than those of the control group (P =0.000),and the decreasing degree of chaperone activity of α-crystallin was lower than that of the control group ( P =0.000 ). Conclusions The study suggests that I3C can protect the chaperone activity of α-crystallin from photooxidation,and the ultraviolet-B laser may be a good exposure source compared with ultraviolet lamp.The ultraviolet-B laser irradiation causes the alteration of structure and chaperone activity of α-crystallin.
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Background There is no effective method to regenerate the optic nerve after injury. It has been recently reported that α-crystallin could promote the survive rate and axon regeneration of retinal ganglion cells (RGCs) effectively. However,the molecular mechanism is not clear. Objective This study was to identify the site of RGCs where the exogenous α-crystallin bind to. Methods RGCs was isolated from retinas of two 2-day-old Long Evans rats and primarily cultured. The positive rate of the RGCs was assessed by counting the number of positive cells for fluorescently-labeled thy1. 1 and cy3 under the fluorescence microscope. The biotinylated exogenous α-crystallin was evaluated by direct coloration and the activity of molecular chaperones was measured by insulin test.After identifying the success of biotinylation along with the activity of molecular chaperones,biotinylated α-crystallin was co-incubated with RGCs and the cells then were reacted to fluorescently labeled avidin for the observation of binding site of exogenous α-crystallin under the laser confocal microscope. Results RGCs of 94% were survived through primary culture. The coloration of biotinylated α-crystallin labeled by the direct coloration method was more intensive, and the value of A450 descended as the decrease of biotinylated α-crystallin concentration,indicating that the α-crystallin was biotinylated successfully. The activity of molecular chaperones of biotinylated α-crystallin was significantly strong but no significant change after being biotinylated after co-incubation of RGCs with biotinylated α-crystallin. Laser confocal microscope examination revealed that co-incubated RGCs with biotinylated α-crystallin showed the red fluorescence on membrane and axon of RGCs rather than cytoplasm and nucleus. The absent response was seen in the control group. Conclusion Exogenous α-crystallin can specifically combine with the membrane of RGCs to play the biological function,but its binding mode and mechanism need further study.
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AIM: To explore whether carnosine can protect α -crys-tallin modification and decreased chaperone by a steroid,and whether carnosine could directly react with a steroid.METHODS: Bovine lens α L-crystallin was separated by size-exclusion chromatography on a Sephacyl S-300 HR column. α L-Crystallin was incubated with different concentrations of prednisolone-21-hemisuccinate (P-21-H)with or without carnosine for different times. The chaperone activity of α L-crystallin was monitored using the prevention thermal aggregation of α L-crystallin. The modified α L-crystallinwas examined by SDS-PAGE and fluorescence measurements. The absorbance spectra of solutions of carnosine and P-21-H were investigated.RESULTS: P-21-H decreased the chaperone activity ofα L-crystallin in a concentration- and time-dependent fashion. Carnosine only worsened this effect. The tryptophan fluorescence intensity of α L-crystallin modified by P-21-H was significantly decreased compared to unmodified crystallin, whereas its non-tryptophan fluorescence was increased with a shift to longer wavelengths in a time- and dose-dependent manner, suggesting that new fluorophores are possibly formed. Carnosine readily reacted with P-21-H thereby inhibiting steroid-mediated protein modification as revealed electrophoretically. The increased absorbance was time-dependent, suggesting adducts may be formed between carnosine and P-21-H.CONCLUSION: Carnosine reacts with P-21-H, which suggests carnosine's potential as a possible anti-seroid agent.