Identification and characterization of an increased glycoprotein in aging: age-associated translocation of cathepsin D.
We found that 14 N-glycosylated proteins were accumulated in the rat cerebral cortex cytosolic fraction in the aging process by a comparative study with two-dimensional gel electrophoresis and concanavalin A staining. All proteins had high mannose and/or hybrid-type N-glycans, as indicated by the fact that they were sensitive to endoglycosidase H digestion. Three of these cytosolic glycoproteins were identified as cathepsin D, a lysosomal protease, by tryptic digestion and nano liquid chromatography electrospray ionization quadrupole time of flight mass spectrometry. The increase of cytosolic cathepsin D during aging was not due to lysosomal membrane disruption, as shown by the fact that the activities of beta-hexosaminidase and beta-glucuronidase, other lysosomal enzymes, did not increase in the cytosolic fraction. Although the total amount of cathepsin D increased during aging, the amount of cathepsin D in the microsomal fraction did not change, indicating a selective increase of cytosolic cathepsin D. This phenomenon was also observed in the hippocampus, cerebellum, kidney, liver, and spleen. Based on these results, we propose that cytosolic cathepsin D is a new biomarker of aging.
Sato
Yuji
Y
Research Team for Functional Genomics, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotion of Human Welfare, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan.
Suzuki
Yusuke
Y
Ito
Emi
E
Shimazaki
Sayaka
S
Ishida
Masami
M
Yamamoto
Takaki
T
Yamamoto
Haruhiko
H
Toda
Tosifusa
T
Suzuki
Minoru
M
Suzuki
Akemi
A
Endo
Tamao
T
D000375:Aging; D000818:Animals; D015415:Biomarkers; D001921:Brain / Q000378:metabolism; D002402:Cathepsin D / Q000737:chemistry* / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry / Q000502:physiology*; D006026:Glycoside Hydrolases / Q000737:chemistry; D008247:Lysosomes / Q000201:enzymology / Q000378:metabolism; D008358:Mannose / Q000737:chemistry; D008861:Microsomes / Q000378:metabolism; D010447:Peptide Hydrolases / Q000737:chemistry; D021381:Protein Transport; D051381:Rats; D014357:Trypsin / Q000737:chemistry
D015415:Biomarkers; D006023:Glycoproteins; D006026:Glycoside Hydrolases; D010447:Peptide Hydrolases; D014357:Trypsin; D002402:Cathepsin D; D008358:Mannose