The Molecular Background of the Differential UV Absorbance of the Human Lens in the 240-400 nm Range

• Published in: Photochemistry and photobiology Vol. 89; no. 4; pp. 856 - 863
• Main Authors: Pajer, Viktor, Tiboldi, Ákos, Bae, Narkhyun, Li, Kongzhao, Kang, Sung Ung, Hopp, Béla, Kolozsvári, Lajos, Lubec, Gert, Nógrádi, Antal
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.07.2013
• Subjects: Adult; Biochemistry; Electrophoresis, Gel, Two-Dimensional; Gene expression; Humans; Lens, Crystalline - chemistry; Mass spectrometry; Middle Aged; Photobiology; Proteins; Spectrophotometry, Atomic; Ultraviolet radiation; Ultraviolet Rays
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.12063

The ultraviolet (UV) absorption of various sections of the human lens was studied and compared with protein expression paralleling differential UV absorbance in anterior and posterior lenticular tissue. The UV absorbance of serial lens cryostat sections (60 μm) and that of lens capsules was determined using a Shimadzu scanning spectrophotometer, and the absorption coefficients were calculated. Two‐dimensional gel electrophoresis was performed using two pooled lenticular protein extracts (anterior and posterior sections). Protein spots were quantified and significantly different spots were identified by mass spectrometry following in‐gel digestion with trypsin and chymotrypsin. The UV‐C and UV‐B absorption of the human lens increased toward the posterior parts of the lens. The anterior and posterior lens capsules also effectively absorbed UV radiation. Levels of molecular chaperone proteins Beta‐crystallin B2 (UniProtKB ID:P43320), A3 (UniProtKB ID:P05813) and of glyceraldehyde 3‐phosphate dehydrogenase (UniProtKB ID:P04406) were significantly higher in the anterior part of the lens, whereas lens proteins Beta‐crystallin B1 (UniProtKB ID:P53674) and Alpha‐crystallin A chain (UniProtKB ID:P02489) were higher in the posterior sections. These results provide evidence that differential UV absorption in the anterior and posterior lens is accompanied by differential protein expression. Although the cornea absorbs most of the ultraviolet (UV) radiation, still considerable radiation may reach the lens. By measuring the UV absorption of human lens sections we found that the UV‐C and UV‐B absorption of the human lens increased toward the posterior parts of the lens. Two‐dimensional gel electrophoresis and mass spectroscopy analysis identified significantly different protein spots in the anterior and posterior section pools. Beta‐crystallin B2 and A3 along with glyceraldehyde 3‐phosphate dehydrogenase were enriched in the anterior part of the lens while elevated levels of Alpha‐crystallin A chain and Beta‐crystallin B1 proteins were found in the posterior portion.