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

Nakajima, Takeshi; Shearer, Thomas R.; Azuma, Mitsuyoshi

doi:10.1167/iovs.14-14778

Cited by 5 publications

(6 citation statements)

References 25 publications

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“…For example, activation of the UPR has been detected in lenses of mice that accumulate mutant forms of alpha- or beta-crystallins (30, 33, 34). It is noteworthy, however, that in contrast to rodent lenses, primate lenses are resistant to calpain activation since they lack calpain-3 activity and human lens epithelial cells contain high constitutive levels of the calpain inhibitor, calpastatin (67). Such variability in calpain activation between rodents and primates may, in part, explain the increased severity of lens opacities in the Lop/+ mouse when compared with those observed in human families segregating MIP mutations.…”

Section: Discussionmentioning

confidence: 99%

Lens ER-stress response during cataract development in Mip-mutant mice

Zhou

Bennett

Shiels

2016

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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Major intrinsic protein (MIP) is a functional water-channel (AQP0) that also plays a key role in establishing lens fiber cell architecture. Genetic variants of MIP have been associated with inherited and age-related forms of cataract; however, the underlying pathogenic mechanisms are unclear. Here we have used lens transcriptome profiling by microarray-hybridization and qPCR to identify pathogenic changes during cataract development in Mip-mutant (Lop/+) mice. In postnatal Lop/+ lenses (P7) 99 genes were up-regulated and 75 were down-regulated (>2-fold, p=<0.05) when compared with wild-type. A pathway analysis of up-regulated genes in the Lop/+ lens (P7) was consistent with endoplasmic reticulum (ER)-stress and activation of the unfolded protein response (UPR). The most up-regulated UPR genes (>4-fold) in the Lop/+ lens included Chac1 > Ddit3 > Atf3 > Trib3 > Xbp1 and the most down-regulated genes (>5-fold) included two anti-oxidant genes, Hspb1 and Hmox1. Lop/+ lenses were further characterized by abundant TUNEL-positive nuclei within central degenerating fiber cells, glutathione depletion, free-radical overproduction, and calpain hyper-activation. These data suggest that Lop/+ lenses undergo proteotoxic ER-stress induced cell-death resulting from prolonged activation of the Eif2ak3/Perk-Atf4-Ddit3-Chac1 branch of the UPR coupled with severe oxidative-stress.

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Section: Discussionmentioning

confidence: 99%

Lens ER-stress response during cataract development in Mip-mutant mice

Zhou

Bennett

Shiels

2016

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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“…To determine whether activated calpain 3 proteolyzed any other lens proteins, the proteolysis of α-spectrin was determined. The rationale was that α-spectrin is a preferred lens protein substrate for calpain 3, which has been used in past studies as the signature protein substrate for in vivo calpain 3 activation and its induced proteolysis [ 33 , 34 ]. As shown in Fig 8 , intact α-spectrin (M r 250 kDa) was observed in lens water soluble and water insoluble fractions of wild type lenses after incubation with 150 mM Ca 2+ plus EGTA whereas it was absent in these two fractions of homogenates incubated with 150 mM Ca 2+ alone (α-spectrin band of 250 kDa identified by arrow in ( Fig 8 ).…”

Section: Resultsmentioning

confidence: 99%

“…Among these, Lp-82 has been identified as the major calpain that on activation causes proteolysis of lens proteins and opacity [ 46 ]. The major in vivo substrates of calpain-3 in the lens have been identified as α-spectrin, vimentin, and α- and β-crystallins [ 33 , 34 , 47 – 49 ]. Evidence also show that the uncontrolled crystallin degradation by calpain Lp82 but not by m-calpain leads insolubilization of crystallins and cataract development in rat lenses [ 50 ].…”

Section: Discussionmentioning

confidence: 99%

Section: Activation Of Calpain-3 By Elevated Calcium Levels In Vitro ...mentioning

confidence: 99%

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Lens-specific βA3/A1-conditional knockout mice: Phenotypic characteristics and calpain activation causing protein degradation and insolubilization

et al. 2023

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βA3/A1-crystallin is a lens structural protein that plays an important role in maintaining lens transparency via interactions with other crystallins. While the function of βA3/A1-crystallin in the retina is well studied, its functions in the lens, other than as a structural protein, remain unclear. In the current study, we generated the lens-specific βA3/A1-crystallin conditional knockout mouse (named βA3/A1ckO) and explored phenotypic changes and the function of the crystallin in the lens. The βA3/A1ckO mice showed congenital cataract at birth and exhibited truncation of lens proteins. Several truncated protein fragments were recovered as a pellet during a low-speed centrifugation (800 rpm, 70 x g) followed by a relatively higher speed centrifugation (5000 rpm, 2744 x g). Mass spectrometric analysis of pellets recovered following the two centrifugations showed that among the fragments with Mr < 20 kDa, the majority of these were from β-tubulin, and some from phakinin, αA-crystallin, and calpain-3. Further, we observed that in vitro activation of calpain-3 by calcium treatment of the wild-type-lens homogenate resulted in the degradation of calpain-3, αA-crystallin and β-tubulin and insolubilization of these proteins. Based on these results, it was concluded that the activation of calpain 3 resulted in proteolysis of β-tubulin, which disrupted cellular microtubular structure, and caused proteolysis of other lens proteins (αA-crystallin and phakinin). These proteolyzed protein fragments become insoluble, and together with the disruption of microtubular structure, and could be the causative factors in the development of congenital nuclear cataract in βA3/A1cKO mice.

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“…In order for calpains to activate, a high level of calcium is required (Obrosova et al, 2010). Studies demonstrate that the privation of an endogenous inhibitor of calpain, named calpastatin, could be linked to the initial changes that cause cataract (Nakajima et al, 2014). Some antioxidants have been reported to regulate calcium influx in selenite induced cataracts, for instance the flavonoid fraction of Brassica oleracea (Vibin et al, 2010).…”

Section: Cataract – Pathogenesismentioning

confidence: 99%

Medicinal Plants and Natural Products Used in Cataract Management

et al. 2019

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Cataract is the leading reason of blindness worldwide and is defined by the presence of any lens opacities or loss of transparency. The most common symptoms of cataract are impaired vision, decreased contrast sensitivity, color disturbance, and glare. Oxidative stress is among the main mechanisms involved in the development of age-related cataract. Surgery through phacoemulsification and intraocular lens implantation is the most effective method for cataract treatment, however, there are chances of serious complications and irreversible loss of vision associated with the surgery. Natural compounds consisting of antioxidant or anti-inflammatory secondary metabolites can serve as potential leads for anticataract agents. In this review, we tried to document medicinal plants and plant-based natural products used for cataract treatment worldwide, which are gathered from available ethnopharmacological/ethnobotanical data. We have extensively explored a number of recognized databases like Scifinder, PubMed, Science Direct, Google Scholar, and Scopus by using keywords and phrases such as “cataract”, “blindness”, “traditional medicine”, “ethnopharmacology”, “ethnobotany”, “herbs”, “medicinal plants”, or other relevant terms, and summarized the plants/phytoconstituents that are evaluated in different models of cataract and also tabulated 44 plants that are traditionally used in cataract in various folklore medical practices. Moreover, we also categorized the plants according to scientific studies carried out in different cataract models with their mechanisms of action.

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

Cited by 5 publications

References 25 publications

Lens ER-stress response during cataract development in Mip-mutant mice

Lens ER-stress response during cataract development in Mip-mutant mice

Lens-specific βA3/A1-conditional knockout mice: Phenotypic characteristics and calpain activation causing protein degradation and insolubilization

Medicinal Plants and Natural Products Used in Cataract Management

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