Abstract: TH-PO269

The Yes Associated Protein (YAP) Facilitates Kidney Fibrosis in a Kidney Injury Molecule-1 (KIM-1) Dependent Manner

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Akinfolarin, Akinwande A., Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Sabbisetti, Venkata, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Ajay, Amrendra Kumar, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Christie, Emily, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Bonventre, Joseph V., Brigham and Women's Hospital, Boston, Massachusetts, United States
Background

The Salvador-Warts-Hippo (SWH) pathway controls organ size by modulating cell proliferation and apoptosis. The nuclear localization of the YAP drives cell proliferation through the transcriptional co-activation of the TEA domain family, a regulator of TGF-β signaling. Following cell confluence, the SWH pathway acts as a negative feedback system to cause nucleo-cytoplasmic shuttling, phosphorylation and inactivation of YAP. Chronic epithelial expression of the KIM-1 is associated with the development of murine kidney fibrosis. In this study we show that the presence of epithelial KIM-1 is associated with nuclear accumulation of YAP and development of kidney fibrosis in mice

Methods

C57B6 wild type (WT) mice or mice with a mutation of the mucin domain of KIM-1 (KIM-1Δmucin) were examined either 14 days after 26 min of bilateral ischemia (I/R) or 10 days after unilateral ureteral obstruction (UUO). LLC-PK1 and HEK cells were transduced with human KIM-1 full length cDNA (LLC-PK1-KIM1 and HEK-KIM1) or an empty pcDNA3 vector (PK1-pcDNA and HEK-pcDNA). Experiments with short hairpin RNA against YAP and inhibition of YAP signaling with a small molecule, verteporfin was also done in PK1 and HEK cells. These kidney cells were then examined for proliferation after TGF-β stimulation and Cisplatin treatment

Results

Proximal tubule (PT) expression of YAP was increased in WT mice that had more kidney fibrosis as compared to their KIM-1Δmucin littermates when examined by Masson’s trichrome (MT) and Periodic Acid Schiff (PAS) staining after I/R and UUO. Western blot analysis of whole kidney cortex revealed greater levels of fibrogenic factors including CTGF, fibronectin and ACTA2 in the WT mice as compared with the KIM-1Δmucin mice. These animal data were supported by in vitro experiments which revealed less cell proliferation and production of pro fibrotic factors with either YAP knock down or inhibition when compared with WT, following TGF-β stimulation. KIM-1 expressing cells had increased nuclear YAP and CTGF levels as compared to cells expressing the control vector

Conclusion

YAP is up regulated in murine kidney fibrosis, more so in proximal tubule cells expressing KIM-1. Pharmacologic depletion of YAP or enhancement of SWH signaling may be of therapeutic importance in attenuating kidney fibrosis

Funding

  • NIDDK Support