Human Aldehyde Dehydrogenase 3A1 Inhibits Proliferation and Promotes Survival of Human Corneal Epithelial Cells

Aglaia Pappa, Donald Brown, Yiannis Koutalos, James DeGregori, Carl White, Vasilis Vasiliou
2005 Journal of Biological Chemistry  
Aldehyde dehydrogenase 3A1 (ALDH3A1) is a NAD(P) ؉ -dependent enzyme that is highly expressed in mammalian corneal epithelial cells and has been shown to protect against UV-and 4-hydroxynonenal-induced cellular damage, mainly by metabolizing toxic lipid peroxidation aldehydes. Here we report a novel function of ALDH3A1 as a negative cell cycle regulator. We noticed a reduction in ALDH3A1 gene expression in actively proliferating primary human corneal epithelium explant cultures, indicating that
more » ... ALDH3A1 expression is inversely correlated with replication. To examine this further, a human corneal epithelial cell line (HCE) lacking endogenous ALDH3A1 was stably transfected to express ALDH3A1 at levels similar to those found in vivo. ALDH3A1-transfected cells exhibited an elongated cell cycle, decreased plating efficiency, and reduced DNA synthesis compared with the mock-transfected cells. These effects were associated with reduced cyclin Aand cyclin B-dependent kinase activities and reduced phosphorylation of the retinoblastoma protein (pRb) as well as decreased protein levels of cyclins A, B, and E, the transcription factor E2F1, and the cyclin-dependent kinase inhibitor p21. These observations were further expanded and confirmed on human keratinocyte cells (NCTC-2544) overexpressing ALDH3A1. Consistent with a protective role of an elongated cell cycle, ALDH3A1transfected cells exhibited increased resistance to the cytotoxic effects of the DNA-damaging agents mitomycin C and Vp-16. Immunohistochemistry and biochemical fractionation revealed that ALDH3A1 is localized both in the nucleus and cytosol of ALDH3A1-transfected cells, implying a possible association between the nuclear localization of the enzyme and its proliferationsuppressive functions. In conclusion, these results suggest that ALDH3A1 may protect corneal epithelial cells against oxidative damage not only through its metabolic function but also by prolonging the cell cycle. 1 The abbreviations used are: ALDH3A1, aldehyde dehydrogenase 3A1; ROS, reactive oxygen species; HCE, human corneal epithelial cell line; NCTC-2544, human skin keratinocyte cell line; 4-HNE, 4-hydroxynonenal; BrdUrd, bromodeoxyuridine; pRb, retinoblastoma protein; DAPI, 4,6-diamidino-2-phenylindole; PBS, phosphate-buffered saline.
doi:10.1074/jbc.m503698200 pmid:15905174 fatcat:uag5po4dwbd7leqcy5fjjb5y6i