Rictor/mTORC2 signaling mediates TGFβ1-induced fibroblast activation and kidney fibrosis

Kidney Int. 2015 Sep;88(3):515-27. doi: 10.1038/ki.2015.119. Epub 2015 May 13.

Abstract

The mammalian target of rapamycin (mTOR) was recently identified in two structurally distinct multiprotein complexes: mTORC1 and mTORC2. Previously, we found that Rictor/mTORC2 protects against cisplatin-induced acute kidney injury, but the role and mechanisms for Rictor/mTORC2 in TGFβ1-induced fibroblast activation and kidney fibrosis remains unknown. To study this, we initially treated NRK-49F cells with TGFβ1 and found that TGFβ1 could activate Rictor/mTORC2 signaling in cultured cells. Blocking Rictor/mTORC2 signaling with Rictor or Akt1 small interfering RNAs markedly inhibited TGFβ1-induced fibronection and α-smooth muscle actin expression. Ensuing western blotting or immunostaining results showed that Rictor/mTORC2 signaling was activated in kidney interstitial myofibroblasts from mice with unilateral ureteral obstruction. Next, a mouse model with fibroblast-specific deletion of Rictor was generated. These knockout mice were normal at birth and had no obvious kidney dysfunction or kidney morphological abnormality within 2 months of birth. Compared with control littermates, the kidneys of Rictor knockout mice developed less interstitial extracellular matrix deposition and inflammatory cell infiltration at 1 or 2 weeks after ureteral obstruction. Thus our study suggests that Rictor/mTORC2 signaling activation mediates TGFβ1-induced fibroblast activation and contributes to the development of kidney fibrosis. This may provide a therapeutic target for chronic kidney diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Line
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Fibroblasts / drug effects*
  • Fibroblasts / enzymology
  • Fibroblasts / pathology
  • Fibronectins / metabolism
  • Fibrosis
  • Kidney / drug effects*
  • Kidney / enzymology
  • Kidney / pathology
  • Kidney Diseases / enzymology*
  • Kidney Diseases / etiology
  • Kidney Diseases / pathology
  • Male
  • Mechanistic Target of Rapamycin Complex 2
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Multiprotein Complexes / metabolism*
  • Myofibroblasts / drug effects
  • Myofibroblasts / enzymology
  • Myofibroblasts / pathology
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA Interference
  • Rapamycin-Insensitive Companion of mTOR Protein
  • Signal Transduction / drug effects*
  • TOR Serine-Threonine Kinases / metabolism*
  • Time Factors
  • Transfection
  • Transforming Growth Factor beta1 / pharmacology*
  • Ureteral Obstruction / complications

Substances

  • Actins
  • Carrier Proteins
  • Fibronectins
  • Multiprotein Complexes
  • Rapamycin-Insensitive Companion of mTOR Protein
  • TGFB1 protein, human
  • Transforming Growth Factor beta1
  • rictor protein, mouse
  • rictor protein, rat
  • smooth muscle actin, rat
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins c-akt