Low activity by the calpain system in primate lenses causes resistance to calcium-induced proteolysis

Nakajima, Emi; Walkup, Ryan D.; Ma, Hong; Shearer, Thomas R.; Azuma, Mitsuyoshi

doi:10.1016/j.exer.2006.02.014

Cited by 24 publications

(18 citation statements)

References 23 publications

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“…Furthermore, tertiary structural elements rather than primary amino acid sequences are likely responsible for directing the cleavage of protein substrates by calpains (Cuerrier et al, 2005), which may explain the high degree of specificity that we have observed for the αA, αB and βA3 peptides. However, the activity of calpain in the primate lens has been reported to be largely inhibited by high levels of the endogenous calpain inhibitor -calpastatin Nakajima et al, 2006), indicating that other mechanisms may be responsible for these cleavages.…”

Section: Discussionmentioning

confidence: 99%

Localization of low molecular weight crystallin peptides in the aging human lens using a MALDI mass spectrometry imaging approach

McArthur

Aquilina

2010

Experimental Eye Research

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This article was originally published as Su, S.P., McArthur, J.D., Aquilina, J.A., Localization of low molecular weight crystallin peptides in the aging human lens using a MALDI mass spectrometry imaging approach, Experimental Eye Research, 91(1), 2010, 97-103. Original item available here Localization of low molecular weight crystallin peptides in the aging human lens using a MALDI mass spectrometry imaging approach AbstractLow molecular weight (LMW) peptides, derived from the breakdown of the major eye lens proteins, the crystallins, accumulate in the human lens with age. These LMW peptides are associated with age-related lens opacity and cataract, with some shown to inhibit the chaperone activity of α-crystallin. However, the mechanism(s) giving rise to the production of these peptides, as well as their distribution within the lens, are not well understood. In this study, we have mapped the distribution of these crystallin-derived peptides present in human lenses of different ages using matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS). Our data showed that most of these LMW peptides emerge in the lens at early middle-age, with peptides greater than 1778 Da in mass being confined to the water insoluble fractions, and to a lesser extent the water soluble fractions of older lenses. MALDI-IMS analyses showed that four peptides, derived from αA-, αB-and γS crystallins, were confined to the lens nuclear fibre cells upon emergence during early middle-age, but were present in both the cortex and nucleus of old lenses. In contrast, another major peptide, derived from the C-terminal breakdown of βA3-crystallin, was present in the cortical and nuclear regions of both young and old lenses. A comparison between age-matched cataractous and non-cataractous lenses showed no distinct differences in LMW peptide profiles, indicating that although cataract may be a potential consequence caused by the emergence of these peptides, it does not contribute directly to the peptide-generating process. AbstractLow molecular weight (LMW) peptides, derived from the breakdown of the major eye lens proteins, the crystallins, accumulate in the human lens with age. These LMW peptides are associated with age-related lens opacity and cataract, with some shown to inhibit the chaperone activity of α-crystallin. However, the mechanism(s) giving rise to the production of these peptides, as well as their distribution within the lens, are not well understood. In this study, we have mapped the distribution of these crystallin-derived peptides present in human lenses of different ages using matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS).Our data showed that most of these LMW peptides emerge in the lens at early middle-age, with peptides greater than 1778 Da in mass being confined to the water insoluble fractions, and to a lesser extent the water soluble fractions of older lenses.MALDI-IMS analyses showed that four peptides, derived from αA-, αB-and γS-crystallins, were confined to t...

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Section: Discussionmentioning

confidence: 99%

Localization of low molecular weight crystallin peptides in the aging human lens using a MALDI mass spectrometry imaging approach

McArthur

Aquilina

2010

Experimental Eye Research

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“…When the CS knockdown-HLE B-3 were cultured with ionomycin, calpain 2 was activated, calpain-specific proteolysis of a-spectrin was induced, and cell death ensued (Figs. 5,6). The calpain-preferred inhibitor SNJ-1945 reduced calpaininduced proteolysis in the CS knockdown-HLE B-3 cells.…”

Section: Discussionmentioning

confidence: 98%

“…6 We now must identify those patients in which environmental factors or human conditions reduce CS activity in their lens epithelium. Numerous factors have been shown to reduce CS in other tissues: Animal experiments support that aging could be such a factor.…”

Section: Discussionmentioning

confidence: 99%

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Loss of Calpastatin Leads to Activation of Calpain in Human Lens Epithelial Cells

Nakajima

Shearer

Azuma

2014

Invest. Ophthalmol. Vis. Sci.

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“…70,71 Although there is considerable evidence of calpain-mediated crystallin truncation in mouse or rat lenses, there is far less evidence for calpainmediated cleavage in human lenses, because there are no active calpain-3 isoforms in human lenses. 72 Calpain-2, the enzyme that may produce aA , has much lower activity in the human lens. Thus, the levels of aA in human lens are very low.…”

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confidence: 99%

Oligomerization with wt αA- and αB-Crystallins Reduces Proteasome-Mediated Degradation of C-Terminally Truncated αA-Crystallin

Zhang

Bian

et al. 2012

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. We previously demonstrated that the ubiquitinproteasome pathway (UPP) is a general protein quality control system that selectively degrades damaged or abnormal lens proteins, including C-terminally truncated aA-crystallin. The objective of this work was to determine the effects of wt aAand aB-crystallins on the degradation of C-terminally truncated aA-crystallin (aA ) and vice versa.METHODS. Recombinant wt aA, aB, and aA 1-162 were expressed in Escherichia coli and purified to homogeneity by chromatography. Subunit exchange and oligomerization were detected by fluorescence resonance energy transfer (FRET), multianglelight scattering and coprecipitation assays. Protein substrates were labeled with 125 I and lens epithelial cell lysates were used as the source of the UPP for degradation assays.RESULTS. FRET, multiangle light scattering, and coprecipitation assays showed that aA 1-162 exchanged subunits with wt aA-or wt aB-crystallin to form hetero-oligomers. aA 1-162 was more susceptible than wt aA-crystallin to degradation by the UPP. When mixed with wt aA-crystallin at 1:1 or 1:4 (aA 1-162 : wt) ratios to form hetero-oligomers, the degradation of aA 1-162 was significantly decreased. Conversely, formation of hetero-oligomers with aA 1-162 enhanced the degradation of wt aAcrystallin. The presence of aA 1-162 , but not wt aA-crystallin, decreased the degradation of wt aB-crystallin.CONCLUSIONS. aA 1-162 forms hetero-oligomers with wt aA-and aB-crystallins. Oligomerization with wt aA-or aB-crystallins reduces the susceptibility of aA 1-162 to degradation by the UPP. In addition, the presence of aA 1-162 in the hetero-oligomers also affects the degradation of wt aA-and aB-crystallins. (Invest Ophthalmol Vis Sci. 2012;53:2541-2550) DOI: 10.1167/iovs.11-9147 L ens fiber cells contain high concentrations of crystallins in the cytoplasm. These crystallins provide the lens with a high refractive index and minimize light scattering at the membranecytoplasm interface. The proper packing of these proteins in cells is essential for maintaining lens transparency.1,2 Disruption of the proper arrangement of these crystallins by adverse modifications is causally related to cataractogenesis.3-6 With aging and environmental insults, lens proteins undergo various modifications, such as oxidation, glycation, deamidation, and truncations. [7][8][9][10][11][12][13][14][15][16] These modified or damaged proteins are usually unstable in aqueous solution and tend to aggregate and precipitate. The aggregation and precipitation of damaged/ modified proteins accounts for a large portion of the age-and cataract-related increases in water-insoluble proteins in the lens.17-24 Thus, efficient removal or repair of the damaged or adversely modified proteins before their aggregation and precipitation appears to be essential for lens transparency.The ubiquitin-proteasome pathway (UPP) is an important protein quality control mechanism that selectively recognizes and degrades proteins with abnormal structures. [25][26][27][28][29][30][31] W...

show abstract

Low activity by the calpain system in primate lenses causes resistance to calcium-induced proteolysis

Cited by 24 publications

References 23 publications

Localization of low molecular weight crystallin peptides in the aging human lens using a MALDI mass spectrometry imaging approach

Localization of low molecular weight crystallin peptides in the aging human lens using a MALDI mass spectrometry imaging approach

Loss of Calpastatin Leads to Activation of Calpain in Human Lens Epithelial Cells

Oligomerization with wt αA- and αB-Crystallins Reduces Proteasome-Mediated Degradation of C-Terminally Truncated αA-Crystallin

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