title: Spatial distributions of phosphorylated membrane proteins aquaporin 0 and MP20 across young and aged human lenses.
abstract: In the human ocular lens it is now realized that post-translational modifications can alter protein function and/or localization in fiber cells that no longer synthesize proteins. The specific sites of post-translational modification to the abundant ocular lens membrane proteins AQP0 and MP20 have been previously identified and their functional effects are emerging. To further understand how changes in protein function and/or localization induced by these modifications alter lens homeostasis, it is necessary to determine the spatial distributions of these modifications across the lens. In this study, a quantitative LC-MS approach was used to determine the spatial distributions of phosphorylated AQP0 and MP20 peptides from manually dissected, concentric layers of fiber cells from young and aged human lenses. The absolute amounts of phosphorylation were determined for AQP0 Ser235 and Ser229 and for MP20 Ser170 in fiber cells from the lens periphery to the lens center. Phosphorylation of AQP0 Ser229 represented a minor portion of the total phosphorylated AQP0. Changes in spatial distributions of phosphorylated APQ0 Ser235 and MP20 Ser170 correlated with regions of physiological interest in aged lenses, specifically, where barriers to water transport and extracellular diffusion form.
authors.affiliation: Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, BSB 358 MSC 509, 173 Ashley Ave., Charleston, SC 29425, USA.
authors.forename: Danielle B
authors.initials: DB
authors.lastname: Gutierrez
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Donita L
authors.initials: DL
authors.lastname: Garland
authors.affiliation: Department of Biostatistics and Epidemiology, Medical University of South Carolina, Cannon Place 303C, 135 Cannon St., Charleston, SC 29425, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Schwacke
authors.affiliation: Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Suite 9160 MRBIII, 465 21st Ave. So., Nashville, TN 37240-7916, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Hachey
authors.affiliation: Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Suite 9160 MRBIII, 465 21st Ave. So., Nashville, TN 37240-7916, USA. Electronic address: k.schey@vanderbilt.edu.
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Schey
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000378:metabolism*; D020346:Aquaporins / Q000378:metabolism*; D015153:Blotting, Western; D002853:Chromatography, Liquid; D005136:Eye Proteins / Q000378:metabolism*; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008875:Middle Aged; D054464:Peroxiredoxins / Q000378:metabolism*; D010766:Phosphorylation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D055815:Young Adult
chemical_list: D020346:Aquaporins; D005136:Eye Proteins; D008565:Membrane Proteins; C030328:aquaporin 0; C515974:PRDX5 protein, human; D054464:Peroxiredoxins
keywords: Aquaporin 0; MP20; Mass spectrometry; Membrane protein; Ocular lens; Phosphorylation