Age-related changes in the retinal pigment epithelium (RPE).
BACKGROUND
Age-related changes in the retina are often accompanied by visual impairment but their mechanistic details remain poorly understood.


METHODS
Proteomic studies were pursued toward a better molecular understanding of retinal pigment epithelium (RPE) aging mechanisms. RPE cells were isolated from young adults (3-4 month-old) and old (24-25 month-old) F344BN rats, and separated into subcellular fractions containing apical microvilli (MV) and RPE cell bodies (CB) lacking their apical microvilli. Proteins were extracted in detergent, separated by SDS-PAGE, digested in situ with trypsin and analyzed by LC MS/MS. Select proteins detected in young and old rat RPE were further studied using immunofluorescence and Western blot analysis.


RESULTS
A total of 356 proteins were identified in RPE MV from young and 378 in RPE MV from old rats, 48% of which were common to each age group. A total of 897 proteins were identified in RPE CB from young rats and 675 in old CB, 56% of which were common to each age group. Several of the identified proteins, including proteins involved in response to oxidative stress, displayed both quantitative and qualitative changes in overall abundance during RPE aging. Numerous proteins were identified for the first time in the RPE. One such protein, collectrin, was localized to the apical membrane of apical brush border of proximal tubules where it likely regulates several amino acid transporters. Elsewhere, collectrin is involved in pancreatic β cell proliferation and insulin secretion. In the RPE, collectrin expression was significantly modulated during RPE aging. Another age-regulated, newly described protein was DJ-1, a protein extensively studied in brain where oxidative stress-related functions have been described.


CONCLUSIONS
The data presented here reveals specific changes in the RPE during aging, providing the first protein database of RPE aging, which will facilitate future studies of age-related retinal diseases.
The Cole Eye Institute, Department of Ophthalmic Research, Cleveland Clinic, Cleveland, Ohio, United States of America.
Xiaorong
X
Gu
Nikolas J
NJ
Neric
John S
JS
Crabb
John W
JW
Crabb
Sanjoy K
SK
Bhattacharya
Mary E
ME
Rayborn
Joe G
JG
Hollyfield
Vera L
VL
Bonilha
D000375:Aging / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000502:physiology*; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000302:isolation & purification / Q000378:metabolism*; D000071617:Protein Deglycase DJ-1; D051381:Rats; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000502:physiology*; D053719:Tandem Mass Spectrometry
C504406:Cltrn protein, rat; D008562:Membrane Glycoproteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; C404267:PARK7 protein, rat; D000071617:Protein Deglycase DJ-1