Mechanisms involved in the protection of UV-induced protein inactivation by the corneal crystallin ALDH3A1.
Various lines of evidence have shown that ALDH3A1 (aldehyde dehydrogenase 3A1) plays a critical and multifaceted role in protecting the cornea from UV-induced oxidative stress. ALDH3A1 is a corneal crystallin, which is defined as a protein recruited into the cornea for structural purposes without losing its primary function (i.e. metabolism). Although the primary role of ALDH3A1 in the metabolism of toxic aldehydes has been clearly demonstrated, including the detoxification of aldehydes produced during UV-induced lipid peroxidation, the structural role of ALDH3A1 in the cornea remains elusive. We therefore examined the potential contribution of ALDH3A1 in maintaining the optical integrity of the cornea by suppressing the aggregation and/or inactivation of other proteins through chaperone-like activity and other protective mechanisms. We found that ALDH3A1 underwent a structural transition near physiological temperatures to form a partially unfolded conformation that is suggestive of chaperone activity. Although this structural transition alone did not correlate with any protection, ALDH3A1 substantially reduced the inactivation of glucose-6-phosphate dehydrogenase by 4-hydroxy-2-nonenal and malondialdehyde when co-incubated with NADP(+), reinforcing the importance of the metabolic function of this corneal enzyme in the detoxification of toxic aldehydes. A large excess of ALDH3A1 also protected glucose-6-phosphate dehydrogenase from inactivation because of direct exposure to UVB light, which suggests that ALDH3A1 may shield other proteins from damaging UV rays. Collectively, these data demonstrate that ALDH3A1 can reduce protein inactivation and/or aggregation not only by detoxification of reactive aldehydes but also by directly absorbing UV energy. This study provides for the first time mechanistic evidence supporting the structural role of the corneal crystallin ALDH3A1 as a UV-absorbing constituent of the cornea.
Estey
Tia
T
Center for Pharmaceutical Biotechnology and Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262.
Cantore
Miriam
M
Molecular Toxicology and Environmental Health Sciences Program, Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262 and the.
Weston
Philip A
PA
Molecular Toxicology and Environmental Health Sciences Program, Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262 and the.
Carpenter
John F
JF
Center for Pharmaceutical Biotechnology and Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262.
Petrash
J Mark
JM
Department of Ophthalmology and Visual Science, Washington University School of Medicine, St. Louis, Missouri 63119.
Vasiliou
Vasilis
V
Center for Pharmaceutical Biotechnology and Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262; Molecular Toxicology and Environmental Health Sciences Program, Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, Colorado 80262 and the. Electronic address: vasilis.vasiliou@uchsc.edu.
D000444:Aldehyde Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000447:Aldehydes / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D003315:Cornea / Q000201:enzymology*; D003459:Crystallins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D015227:Lipid Peroxidation / Q000528:radiation effects; D008315:Malondialdehyde / Q000737:chemistry / Q000494:pharmacology; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009249:NADP / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000528:radiation effects; D013329:Structure-Activity Relationship; D014466:Ultraviolet Rays / Q000009:adverse effects
D000447:Aldehydes; D003459:Crystallins; D015853:Cysteine Proteinase Inhibitors; D018832:Molecular Chaperones; D008315:Malondialdehyde; D009249:NADP; D005954:Glucosephosphate Dehydrogenase; C480021:ALDH3A1 protein, human; D000444:Aldehyde Dehydrogenase; C027576:4-hydroxy-2-nonenal