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J.R. Dunlevy, J.A. Rada; Interaction of Lumican with Aggrecan in the Aging Human Sclera . Invest. Ophthalmol. Vis. Sci. 2003;44(13):413.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To characterize changes in the scleral extracellular matrix with increasing age, the lumican (keratan sulfate proteoglycan) core protein was examined in different regions of the human sclera from donors aged 6 – 89 years. Methods: Lumican was immunoaffinity purified from 4 M guanidine-HCL extracts of human sclera using antisera specific for a c-terminal region of human lumican (generously supplied by Dr. Peter J. Roughley, Shriner’s Hospitals for Children, Montreal, Canada), and characterized by western blot analysis with and without prior digestion with chondroitinase ABC, keratanase I, II, and/or endo-B-galactosidase. Additionally, lumican was characterized in scleral extracts of human donors 6 – 89 years old. The presence of aggrecan was evaluated in purified lumican fractions and in scleral extracts by western blotting with antisera specific for regions of the human aggrecan core protein (Robin Poole, and John Sandy). Results:Lumican was present in the human sclera as an ~66 kDa core protein with short low or unsulfated keratan sulfate side chains. Additionally, a larger >200 kDa species was apparent on western blots that was immunologically related to lumican. This high molecular weight material increased in amount in scleral extracts with increasing age of the donor. This high molecular weight complex was most abundant in unreduced samples, and about 2/3rds of the ~66 kDa lumican core protein could be released from the complex upon reduction of the scleral extract with 0.49 M DTT. Further characterization of the >200 kDa lumican-immunopurified complex indicated that aggrecan (the cartilage proteoglycan) was covalently associated with lumican. Conclusions:Reducible and nonreducible lumican-aggrecan interactions occur in the scleral extracellular matrix and result in the formation of high molecular weight complexes that increase with age. These results represent the first report showing lumican-aggrecan interactions, and suggest they may play a role in age-related scleral extracellular matrix changes.
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