Age-related TFEB downregulation in proximal tubules causes systemic metabolic disorders and occasional apolipoprotein A4–related amyloidosis
Jun Nakamura, Takeshi Yamamoto, Yoshitsugu Takabatake, Tomoko Namba-Hamano, Atsushi Takahashi, Jun Matsuda, Satoshi Minami, Shinsuke Sakai, Hiroaki Yonishi, Shihomi Maeda, Sho Matsui, Hideaki Kawai, Isao Matsui, Tadashi Yamamuro, Ryuya Edahiro, Seiji Takashima, Akira Takasawa, Yukinori Okada, Tamotsu Yoshimori, Andrea Ballabio, Yoshitaka Isaka
Jun Nakamura, Takeshi Yamamoto, Yoshitsugu Takabatake, Tomoko Namba-Hamano, Atsushi Takahashi, Jun Matsuda, Satoshi Minami, Shinsuke Sakai, Hiroaki Yonishi, Shihomi Maeda, Sho Matsui, Hideaki Kawai, Isao Matsui, Tadashi Yamamuro, Ryuya Edahiro, Seiji Takashima, Akira Takasawa, Yukinori Okada, Tamotsu Yoshimori, Andrea Ballabio, Yoshitaka Isaka
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Research Article Metabolism Nephrology

Age-related TFEB downregulation in proximal tubules causes systemic metabolic disorders and occasional apolipoprotein A4–related amyloidosis

Abstract

With the aging of society, the incidence of chronic kidney disease (CKD), a common cause of death, has been increasing. Transcription factor EB (TFEB), the master transcriptional regulator of the autophagy/lysosomal pathway, is regarded as a promising candidate for preventing various age-related diseases. However, whether TFEB in the proximal tubules plays a significant role in elderly patients with CKD remains unknown. First, we found that nuclear TFEB localization in proximal tubular epithelial cells (PTECs) declined with age in both mice and humans. Next, we generated PTEC-specific Tfeb-deficient mice and bred them for up to 24 months. We found that TFEB deficiency in the proximal tubules caused metabolic disorders and occasionally led to apolipoprotein A4 (APOA4) amyloidosis. Supporting this result, we identified markedly decreased nuclear TFEB localization in the proximal tubules of elderly patients with APOA4 amyloidosis. The metabolic disturbances were accompanied by mitochondrial dysfunction due to transcriptional changes involved in fatty acid oxidation and oxidative phosphorylation pathways, as well as decreased mitochondrial clearance. This decreased clearance was reflected by the accumulation of mitochondria–lysosome-related organelles, which depended on lysosomal function. These results shed light on the presumptive mechanisms of APOA4 amyloidosis pathogenesis and provide a therapeutic strategy for CKD-related metabolic disorders and APOA4 amyloidosis.

Authors

Jun Nakamura, Takeshi Yamamoto, Yoshitsugu Takabatake, Tomoko Namba-Hamano, Atsushi Takahashi, Jun Matsuda, Satoshi Minami, Shinsuke Sakai, Hiroaki Yonishi, Shihomi Maeda, Sho Matsui, Hideaki Kawai, Isao Matsui, Tadashi Yamamuro, Ryuya Edahiro, Seiji Takashima, Akira Takasawa, Yukinori Okada, Tamotsu Yoshimori, Andrea Ballabio, Yoshitaka Isaka

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Figure 2

TFEB downregulation in PTECs causes apolipoprotein A4 (APOA4) amyloidosis with age.

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TFEB downregulation in PTECs causes apolipoprotein A4 (APOA4) amyloidosi...
(A, B, and E) Representative images of PAS staining (A), Congo red staining (B), and APOA4 immunostaining (E) in the kidneys of aged Tfebfl/fl KAP mice with (A, B, and E) or without (E) amyloid deposits. (B) Amyloid deposition scores (n = 9–15). (C) Representative electron micrographs of the amyloid deposits. Fibril diameters were measured (n = 20). (D) Schematic illustration of the LMD–LC-MS/MS procedure. The glomeruli with amyloid deposits were isolated and processed for proteomics. (F) Representative images from the cortical regions of human autopsy kidney samples. (G and H) Representative Western blot images from HK-2 cells transfected with (H) or without (G) TFEB siRNA after treatment with recombinant human APOA4 protein (with His-Tag) for 3 hours (n = 3). This experiment was repeated 3 times. Blots were set up in parallel and run contemporaneously (H). (I) Apoa4 mRNA levels relative to Actb in the livers of mice (n = 5–10). (J) APOA4 concentrations in the plasma of mice (n = 5–10). Scale bars: 50 μm (A, B, and D–F) and 1 μm (C). Data are shown bar graphs, showing mean ± SEM. Values are normalized by the mean value of HK-2 cells transfected with siControl (H) or young Tfebfl/fl mice (I). *P < 0.05 versus age-matched Tfebfl/fl control littermates or siControl HK-2 cells; #P < 0.05 versus young mice or siControl HK-2 cells (B, I, and J, 1-way ANOVA followed by the Tukey-Kramer test; H, 2-tailed Student’s t test). Sections were counterstained with hematoxylin. Bright-field images of Congo red staining were captured along with corresponding apple-green birefringence under polarized light. F/F, Tfebfl/fl mice; F/F;KAP, Tfebfl/fl KAP mice; eGFR, estimated glomerular filtration rate.