Identification and characterization of an increased glycoprotein in aging: age-associated translocation of cathepsin D |
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Authors: | Sato Yuji Suzuki Yusuke Ito Emi Shimazaki Sayaka Ishida Masami Yamamoto Takaki Yamamoto Haruhiko Toda Tosifusa Suzuki Minoru Suzuki Akemi Endo Tamao |
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Institution: | 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. |
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Abstract: | 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. |
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Keywords: | Glycoprotein 2-D PAGE Lectin Cathepsin D Translocation Brain CNS |
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