April 2010
Volume 51, Issue 13
ARVO Annual Meeting Abstract  |   April 2010
Calpain and Caspase-12 Activation Mediates Apoptosis in Transgenic Mouse Lens Expressing a Dominant-Negative Mutant of FGFR
Author Affiliations & Notes
  • L. W. Reneker
    Ophthalmology, University of Missouri-Columbia, Columbia, Missouri
  • H. Chen
    Ophthalmology, University of Missouri-Columbia, Columbia, Missouri
  • Footnotes
    Commercial Relationships  L.W. Reneker, None; H. Chen, None.
  • Footnotes
    Support  NIH Grants EY13146 and EY14795, and Research to Prevent Blindness (RPB)
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 2617. doi:
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      L. W. Reneker, H. Chen; Calpain and Caspase-12 Activation Mediates Apoptosis in Transgenic Mouse Lens Expressing a Dominant-Negative Mutant of FGFR. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2617.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Expressing a dominant negative (DN) mutant of FGFR, which is a truncated form of FGFR1, in the transgenic mouse lens can induce cell death in the lens fiber cells. Previously we demonstrated that DN-FGFR-induced cell death is independent of the classical mitochondrial apoptosis mechanism. The alternative cell death mechanism is investigated in this study.

Methods: : Water-soluble proteins were prepared from newborn wild type (WT) and DN-FGFR mouse lenses. Calpain activation was evaluated by the presence of cleaved crystalline fragments. Cleaved (active) caspase-12 in the lens homogenate was detected by western blot. Caspase-12 localization in mouse lens was demonstrated by immunofluorescence.

Results: : alpha- and beta-crystallin breakdown products were detected by western blot in the DN-FGFR lenses. The same crystallin proteolytic patterns were seen in the WT lens proteins after incubation with 1 mM calcium at 37°C for one hour. These results suggested that abnormal activation of calpain occurred in the DN-FGFR lens. A low level of cleaved caspase-12 was present in the WT lens. In comparison, the level was significantly increased in the DN-FGFR transgenic lens. Immunostaining showed that, in the WT lens, caspase-12 was found in the lens epithelial cells. During fiber cell differentiation, caspase-12 was localized to the nuclei of the fiber cells. In contrast to the WT lens, caspase-12 immunofluorescence in the DN-FGFR lens did not co-localize with the cell nuclear staining, suggesting that caspase-12 released from the cell nuclei can be cleaved (activated) by the calpain in the cytoplasm in the presence of calcium.

Conclusions: : We have identified a new calpain activated caspase-12 mediated apoptosis pathway in the lens fiber cells. We propose that accumulation of folding-incompetent DN-FGFR proteins in the lens fiber cells can induce ER stress, disrupt calcium homeostasis, and result in the activation of calpain and caspase-12 which contributes to the mechanism of apoptosis.

Keywords: apoptosis/cell death • stress response • transgenics/knock-outs 

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