Changes in podocyte TRPC channels evoked by plasma and sera from patients with recurrent FSGS and by putative glomerular permeability factors

Biochim Biophys Acta Mol Basis Dis. 2017 Sep;1863(9):2342-2354. doi: 10.1016/j.bbadis.2017.06.010. Epub 2017 Jun 16.


Primary forms of focal and segmental glomerulosclerosis (FSGS) are driven by circulating factors that cause dysfunction or loss podocytes. Rare genetic forms of FSGS can be caused by mutations in TRPC6, which encodes a Ca2+-permeable cationic channel expressed in mesangial cells and podocytes; and NPHS2, which encodes podocin, a TRPC6-binding protein expressed in podocyte slit diaphragm domains. Here we observed that exposing immortalized mouse podocytes to serum or plasma from recurrent FSGS patients for 24h increased the steady-state cell-surface abundance of TRPC6, accompanied by an increase in currents through endogenous TRPC6 channels evoked by a hypoosmotic stretch stimulus. These effects were mimicked by the soluble urokinase receptor (suPAR) and by tumor necrosis factor (TNF), circulating factors implicated in nephrotic syndromes. Most but not all of the recurrent FSGS plasma samples that we examined also caused a loss of podocin over a period of several hours. The loss of podocin was also seen following exposure to suPAR but not TNF. However, TNF increased the effects of suPAR on TRPC6 and podocin, and TNF and suPAR are required for the full effects of one of the recurrent FSGS plasma samples. The actions of FSGS plasma, suPAR and TNF on surface abundance of TRPC6 were blocked by cilengitide, an inhibitor of αvβ3-integrin signaling. These data suggest that primary FSGS is a heterogeneous condition mediated by multiple circulating factors, and support TRPC6 and αvβ3-integrin as potential therapeutic targets.

Keywords: Chronic kidney disease; Integrin; Podocin; TNF; TRPC6; suPAR.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Cell Line, Transformed
  • Female
  • Glomerulosclerosis, Focal Segmental / metabolism*
  • Glomerulosclerosis, Focal Segmental / pathology
  • Humans
  • Integrin alphaVbeta3 / metabolism
  • Intracellular Signaling Peptides and Proteins / biosynthesis
  • Male
  • Membrane Proteins / biosynthesis
  • Nephrotic Syndrome / metabolism*
  • Nephrotic Syndrome / pathology
  • Permeability
  • Plasma*
  • Podocytes / metabolism*
  • Podocytes / pathology
  • Receptors, Urokinase Plasminogen Activator / biosynthesis
  • Serum*
  • TRPC6 Cation Channel / metabolism*
  • Tumor Necrosis Factor-alpha / metabolism


  • Integrin alphaVbeta3
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • NPHS2 protein
  • Receptors, Urokinase Plasminogen Activator
  • TRPC6 Cation Channel
  • TRPC6 protein, human
  • Tumor Necrosis Factor-alpha