Shin-Ichi Makino1,2,3, Naritoshi Shirata2,4, Juan Alejandro Oliva Trejo2,5, Kanae Yamamoto-Nonaka2,3, Hiroyuki Yamada1,2,3, Takafumi Miyake2,3, Kiyoshi Mori2,6,7, Takahiko Nakagawa2,8, Yoshitaka Tashiro9, Hirofumi Yamashita9, Motoko Yanagita2,3,10, Ryosuke Takahashi9, Katsuhiko Asanuma11,2. 1. Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan. 2. The Laboratory for Kidney Research (TMK project), Medical Innovation Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan. 3. Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan. 4. Sohyaku, Innovative Research Division, Mitsubishi Tanabe Pharmaceutical Corporation, Saitama, Japan. 5. Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan. 6. Department of Molecular and Clinical Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan. 7. Department of Nephrology, Shizuoka General Hospital, Shizuoka, Japan. 8. Department of Nephrology, Rakuwakai Otowa Hospital, Kyoto, Japan. 9. Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan. 10. Institute for the Advanced Study of Human Biology, Kyoto University, Kyoto, Japan. 11. Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan kasanuma@chiba-u.jp.
Abstract
BACKGROUND: The ubiquitin-proteasome system (UPS) and the autophagy-lysosomal system (APLS) are major intracellular degradation procedures. The importance of the APLS in podocytes is established, but the role of the UPS is not well understood. METHODS: To investigate the role of the UPS in podocytes, mice were generated that had deletion of Rpt3 (Rpt3 pdKO), which encodes an essential regulatory subunit required for construction of the 26S proteasome and its deubiquitinating function. RESULTS: Rpt3 pdKO mice showed albuminuria and glomerulosclerosis, leading to CKD. Impairment of proteasome function caused accumulation of ubiquitinated proteins and of oxidative modified proteins, and it induced podocyte apoptosis. Although impairment of proteasome function normally induces autophagic activity, the number of autophagosomes was lower in podocytes of Rpt3pdKO mice than in control mice, suggesting the autophagic activity was suppressed in podocytes with impairment of proteasome function. In an in vitro study, antioxidant apocynin and autophagy activator rapamycin suppressed podocyte apoptosis induced by proteasome inhibition. Moreover, rapamycin ameliorated the glomerular injury in the Rpt3 pdKO mice. The accumulation of ubiquitinated proteins and of oxidative modified proteins, which were detected in the podocytes of Rpt3 pdKO mice, is a characteristic feature of aging. An aging marker was increased in the podocytes of Rpt3 pdKO mice, suggesting that impairment of proteasome function promoted signs of aging in podocytes. CONCLUSIONS: Impairment of proteasome function in podocytes led to CKD, and antioxidants and autophagy activators can be therapeutic agents for age-dependent CKD.
BACKGROUND: The ubiquitin-proteasome system (UPS) and the autophagy-lysosomal system (APLS) are major intracellular degradation procedures. The importance of the APLS in podocytes is established, but the role of the UPS is not well understood. METHODS: To investigate the role of the UPS in podocytes, mice were generated that had deletion of Rpt3 (Rpt3 pdKO), which encodes an essential regulatory subunit required for construction of the 26S proteasome and its deubiquitinating function. RESULTS: Rpt3 pdKO mice showed albuminuria and glomerulosclerosis, leading to CKD. Impairment of proteasome function caused accumulation of ubiquitinated proteins and of oxidative modified proteins, and it induced podocyte apoptosis. Although impairment of proteasome function normally induces autophagic activity, the number of autophagosomes was lower in podocytes of Rpt3pdKO mice than in control mice, suggesting the autophagic activity was suppressed in podocytes with impairment of proteasome function. In an in vitro study, antioxidant apocynin and autophagy activator rapamycin suppressed podocyte apoptosis induced by proteasome inhibition. Moreover, rapamycin ameliorated the glomerular injury in the Rpt3 pdKO mice. The accumulation of ubiquitinated proteins and of oxidative modified proteins, which were detected in the podocytes of Rpt3 pdKO mice, is a characteristic feature of aging. An aging marker was increased in the podocytes of Rpt3 pdKO mice, suggesting that impairment of proteasome function promoted signs of aging in podocytes. CONCLUSIONS: Impairment of proteasome function in podocytes led to CKD, and antioxidants and autophagy activators can be therapeutic agents for age-dependent CKD.
Authors: P Mundel; J Reiser; A Zúñiga Mejía Borja; H Pavenstädt; G R Davidson; W Kriz; R Zeller Journal: Exp Cell Res Date: 1997-10-10 Impact factor: 3.905