SMAD3 promotes autophagy dysregulation by triggering lysosome depletion in tubular epithelial cells in diabetic nephropathy

Autophagy. 2021 Sep;17(9):2325-2344. doi: 10.1080/15548627.2020.1824694. Epub 2020 Oct 12.

Abstract

Macroautophagy/autophagy dysregulation has been noted in diabetic nephropathy; however, the regulatory mechanisms controlling this process remain unclear. In this study, we showed that SMAD3 (SMAD family member 3), the key effector of TGFB (transforming growth factor beta)-SMAD signaling, induces lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis. The pharmacological inhibition or genetic deletion of SMAD3 restored lysosome biogenesis activity by alleviating the suppression of TFEB, thereby protecting lysosomes from depletion and improving autophagic flux in renal tubular epithelial cells in diabetic nephropathy. Mechanistically, we found that SMAD3 directly binds to the 3'-UTR of TFEB and inhibits its transcription. Silencing TFEB suppressed lysosome biogenesis and resulted in a loss of the protective effects of SMAD3 inactivation on lysosome depletion under diabetic conditions. In conclusion, SMAD3 promotes lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis; this may be an important mechanism underlying autophagy dysregulation in the progression of diabetic nephropathy.Abbreviations: AGEs: advanced glycation end products; ATP6V1H: ATPase H+ transporting V1 subunit H; CTSB: cathepsin B; ChIP: chromatin immunoprecipitation; Co-BSA: control bovine serum albumin; DN: diabetic nephropathy; ELISA: enzyme-linked immunosorbent assay; FN1: fibronectin 1; HAVCR1/TIM1/KIM-1: hepatitis A virus cellular receptor 1; LAMP1: lysosomal associated membrane protein 1; LMP: lysosome membrane permeabilization; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; NC: negative control; SIS3: specific inhibitor of SMAD3; SMAD3: SMAD family member 3; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TECs: tubular epithelial cells; TFEB: transcription factor EB; TGFB1: transforming growth factor beta 1; TGFBR1: transforming growth factor beta receptor 1; UTR: untranslated region; VPS11: VPS11 core subunit of CORVET and HOPS complexes.

Keywords: Autophagy; SMAD3; TFEB; diabetic nephropathy; lysosome; tubular epithelial cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autophagy*
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / metabolism
  • Diabetes Mellitus* / metabolism
  • Diabetic Nephropathies*
  • Epithelial Cells / metabolism
  • Humans
  • Lysosomes / metabolism
  • Signal Transduction
  • Smad3 Protein* / metabolism

Substances

  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • SMAD3 protein, human
  • Smad3 Protein
  • TFEB protein, human

Grants and funding

This work was supported by grants from the National Natural Science Foundation of China [No. 81700627, 81670654, and 81974095]; the Funds for Natural Science Foundation of Guangdong Province[2019A1515010678]; the Research Grants Council of Hong Kong, University Grants Committee[GRF 14163317, 14117418, 14104019, C7018-16G, and R4012-18F], the Health and Medical Research Fund of Hong Kong [05161326 and 14152321], and the Guangdong-Hong Kong-Macao-Joint Labs Program from Guangdong Science and Technology Department [2019B121205005].