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Kidney Week

Abstract: PO1990

TRPC6 Is a Key Mediator of a PAR-1 Activation Pathway in Podocytes That Is Responsible for FSGS

Session Information

  • Podocyte Biology
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • May, Carl J., University of Bristol, Bristol, Bristol, United Kingdom
  • Chesor, Musleeha, University of Bristol, Bristol, Bristol, United Kingdom
  • Welsh, Gavin Iain, University of Bristol, Bristol, Bristol, United Kingdom
  • Saleem, Moin, University of Bristol, Bristol, Bristol, United Kingdom
Background

There is good evidence for the role of a circulating factor in the pathogenesis of idiopathic nephrotic syndrome (iNS). We have previously presented our work hypothesising the role of circulating plasma proteases. An active form of the protease activated receptor, PAR-1 expressed in the podocytes of SV129 mice (PAR-1Active ) led to proteinuria, sclerosis and death at 42 days. It was found that the signalling response to PAR-1 agonist treatment of podocytes in vitro was also present in the kidney IHC sections from the PAR-1Active mouse, and in human podocytes treated with post-transplant recurrence plasma. This response includes the phosphorylation of VASP, JNK and Paxillin. We hypothesised that the downstream response to PAR-1 signalling involves activation of TRPC6.

Methods

Conditionally immortalised human WT podocytes and TRPC6 KO mouse podocytes were treated with a PAR-1 agonist (15 µM PAR-3931-PI Peptides International). The PAR-1Active mouse was crossed with a TRPC6 KO on a C57 Bl6 background to develop the NPHS2 Cre PAR-1Active TRPC6 KO mouse.
Biopsy tissue was obtained via the UK Nephrotic Syndrome Study, NephroS, housed within the UK Renal Rare Disease Registry, RaDaR.

Results

We present data confirming activation of the same signalling pathways in vitro in podocytes treated with a PAR-1 agonist, and in vivo in our NPHS2 Cre PAR-1Active mouse. Then in vivo in human nephropathy biopsies pVASP and pJNK signalling was significantly higher in FSGS and Minimal Change Disease biopsies when compared to IgA nephropathy biopsies.
TRPC6 is a calcium channel that can be found at the slit diaphragm and can signal to the actin cytoskeleton. TRPC6 Knock Out (T6KO) podocytes showed an altered response to PAR-1 agonist treatment. There was no phosphorylation of VASP and only brief phosphorylation of JNK and no phosphorylation of Paxillin. When we crossed a T6KO mouse with our NPHS2 Cre PAR-1 Active mouse we saw significantly increased survival from a median of 40 days in the NPHS2 Cre PAR-1 Active mouse to 60 days when TRPC6 is knocked out.

Conclusion

We have identified a common signalling response to PAR-1 activation in podocytes in vitro and in vivo, including in human disease. We identified TRPC6 as being a key player in the response, suggesting a unique role of this ion channel in mediating circulating factor disease, and a direct therapeutic target.