Age-Related Cataracts in α3Cx46-Knockout Mice Are Dependent on a Calpain 3 Isoform

Tang, Yajun; Li, Xiangyang; Zoltoski, Rebecca K.; Novak, L.A.; Herrera, Raúl; Richard, Isabelle; Kuszak, J.R.; Kumar, Nalin M.

doi:10.1167/iovs.06-0926

Cited by 34 publications

(33 citation statements)

References 43 publications

(72 reference statements)

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“…Any or all of these phenomena might require the developmentally regulated activation of calpains. This is consistent with our previous observation that in calpain 3 knock-out mice the transition zone is altered, suggesting a change in the differentiation program (35).…”

supporting

confidence: 93%

Calpain Expression and Activity during Lens Fiber Cell Differentiation

María

Shi

Kumar

et al. 2009

Journal of Biological Chemistry

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In animal models, the dysregulated activity of calcium-activated proteases, calpains, contributes directly to cataract formation. However, the physiological role of calpains in the healthy lens is not well defined. In this study, we examined the expression pattern of calpains in the mouse lens. Real time PCR and Western blotting data indicated that calpain 1, 2, 3, and 7 were expressed in lens fiber cells. Using controlled lysis, depth-dependent expression profiles for each calpain were obtained. These indicated that, unlike calpain 1, 2, and 7, which were most abundant in cells near the lens surface, calpain 3 expression was strongest in the deep cortical region of the lens. We detected calpain activities in vitro and showed that calpains were active in vivo by microinjecting fluorogenic calpain substrates into cortical fiber cells. To identify endogenous calpain substrates, membrane/cytoskeleton preparations were treated with recombinant calpain, and cleaved products were identified by twodimensional difference electrophoresis/mass spectrometry. Among the calpain substrates identified by this approach was ␣II-spectrin. An antibody that specifically recognized calpaincleaved spectrin was used to demonstrate that spectrin is cleaved in vivo, late in fiber cell differentiation, at or about the time that lens organelles are degraded. The generation of the calpain-specific spectrin cleavage product was not observed in lens tissue from calpain 3-null mice, indicating that calpain 3 is uniquely activated during lens fiber differentiation. Our data suggest a role for calpains in the remodeling of the membrane cytoskeleton that occurs with fiber cell maturation.

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confidence: 93%

Calpain Expression and Activity during Lens Fiber Cell Differentiation

María

Shi

Kumar

et al. 2009

Journal of Biological Chemistry

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“…In lenses from young Cx46 KO mice, a cataract forms in central fiber cells, where intracellular Ca 2+ exceeds 1 μM (Gao et al 2004), and its formation is dependent on activation of the lens-specific calpain Lp82 (Tang et al 2007; Baruch et al 1992). Lenses from young GPX-1 KO mice are transparent, but intracellular Ca 2+ has accumulated to very near 1 μM in their central fiber cells.…”

Section: Discussionmentioning

confidence: 99%

The Effects of GPX-1 Knockout on Membrane Transport and Intracellular Homeostasis in the Lens

et al. 2008

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Glutathione peroxidase-1 (GPX-1) is an enzyme that protects the lens against H2O2-mediated oxidative damage. The purpose of the present study was to determine the effects of GPX-1 knockout (KO) on lens transport and intracellular homeostasis. To investigate these lenses we used (1) whole lens impedance studies to measure membrane conductance, resting voltage and fiber cell gap junction coupling conductance; (2) osmotic swelling of fiber cell membrane vesicles to determine water permeability; and (3) injection of Fura2 and Na+-binding benzofuran isophthalate (SBFI) into fiber cells to measure [Ca2+]i and [Na+]i, respectively, in intact lenses. These approaches were used to compare wild-type (WT) and GPX-1 KO lenses from mice around 2 months of age. There were no significant differences in clarity, size, resting voltage, membrane conductance or fiber cell membrane water permeability between WT and GPX-1 KO lenses. However, in GPX-1 KO lenses, coupling conductance was 72% of normal in the outer shell of differentiating fibers and 45% of normal in the inner core of mature fibers. Quantitative Western blots showed that GPX-1 KO lenses had about 50% as much labeled Cx46 and Cx50 protein as WT, whereas they had equivalent labeled AQP0 protein as WT. Both Ca2+ and Na+ accumulated significantly in the core of GPX-1 KO lenses. In summary, the major effect on lens transport of GPX-1 KO was a reduction in gap junction coupling conductance. This reduction affected the lens normal circulation by causing [Na+]i and [Ca2+]i to increase, which could increase cataract susceptibility in GPX-1 KO lenses.

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“…An increase in mRNA expression of calpains has been reported for lenses in the early stages of cataractogenesis [68] and in rodent models, lens-specific splice variants of calpain 3 are activated in experimental cataracts [62]. In addition, knockout of calpain 3 is known to delay the formation of cataracts [69]. However, the splice variants of calpain 3 (Lp82 & Lp85) are not present in human lens [66].…”

Section: Introductionmentioning

confidence: 99%

Calpains: Attractive Targets for the Development of Synthetic Inhibitors

Pietsch

Chua²,

Abell

2010

CTMC

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The physiological roles of calpains are discussed, as are the associated pathological disorders that result from their over-activation. We also present practical information for establishing functional inhibition assays and an overview of X-ray crystal structures of calpain-inhibitor complexes to aid inhibitor design. These structures reveal the expected extended beta-strand conformation for the inhibitor backbone, a geometry that has been engineered into inhibitors with the introduction of either an N-terminal heterocycle or a macrocycle that links the P(1) and P(3) residues. The structure and function of all the main classes of inhibitors are reviewed, with most examples being classified according to the nature of the C-terminal reactive warhead group that reacts with the active site cysteine of calpains. These inhibitor classes include epoxysuccinate derivatives, aldehydes, aldehyde prodrugs (hemiacetals) and alpha-keto carbonyl compounds. Inhibitors derived from the endogenous inhibitor calpastatin and examples lacking a warhead, are now known and these are also discussed.

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Age-Related Cataracts in α3Cx46-Knockout Mice Are Dependent on a Calpain 3 Isoform

Cited by 34 publications

References 43 publications

Calpain Expression and Activity during Lens Fiber Cell Differentiation

Calpain Expression and Activity during Lens Fiber Cell Differentiation

The Effects of GPX-1 Knockout on Membrane Transport and Intracellular Homeostasis in the Lens

Calpains: Attractive Targets for the Development of Synthetic Inhibitors

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