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Invest Ophthalmol Vis Sci. 2010 Aug;51(8):3977-85. doi: 10.1167/iovs.09-4919. Epub 2010 Apr 7.

C-terminal cleavage of DeltaNp63alpha is associated with TSA-induced apoptosis in immortalized corneal epithelial cells.

Author information

  • 1Department of Ophthalmology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057, USA. danielle.robertson@utsouthwestern.edu

Abstract

PURPOSE:

In the central human corneal epithelium, loss of DeltaNp63 occurs in all surface epithelial cells preparing to undergo desquamation, suggesting a potential role for DeltaNp63 isoforms in mediating surface cell apoptotic shedding. In this study, the authors investigated a role for DeltaNp63 isoforms in caspase-mediated apoptosis in a telomerase-immortalized corneal epithelial cell line.

METHODS:

For in vitro studies, hTCEpi cells were cultured in KGM-2 serum-free culture media containing 0.15 mM calcium. To assess dynamic protein interactions among individual DeltaNp63 isoforms, DeltaNp63-EGFP expression plasmids were transiently expressed in hTCEpi cells and evaluated by FRAP. Trichostatin-A (TSA; 3.31 muM) was used to induce cell death as measured by caspase activity. Cleavage and loss of endogenous DeltaNp63alpha, DeltaNp63-EGFP expression plasmids, and p53 were assessed after treatment with TSA and siRNA.

RESULTS:

Transient expression of DeltaNp63-EGFP alpha and beta isoforms resulted in the formation of a smaller isoform similar in size to DeltaNp63gamma-EGFP. FRAP demonstrated that DeltaNp63alpha-EGFP has greater immobile fraction than beta or gamma. TSA induced caspase-mediated apoptotic pathways; caspase induction was accompanied by a decrease in endogenous DeltaNp63alpha and p53. TSA upregulated DeltaNp63-EGFP plasmid expression; this was accompanied by a selective increase in cleavage of DeltaNp63alpha-EGFP. siRNA knockdown of DeltaNp63alpha correlated with a reduction in p53 independently of TSA.

CONCLUSIONS:

DeltaNp63alpha is the dominant active isoform in corneal epithelial cell nuclei. Loss of DeltaNp63alpha occurs during apoptotic signaling by cleavage at the C terminus. The corresponding loss of p53 suggests that a significant relationship appears to exist between these two regulatory proteins.

PMID:
20375332
[PubMed - indexed for MEDLINE]
PMCID:
PMC2910636
Free PMC Article

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