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Abstract: TH-PO1081

The JAK-STAT Pathway in Podocytes Is Activated and Modulated by Monomeric Cardiotrophin-Like Cytokine Factor 1 (CLCF1)

Session Information

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Sharma, Mukut, KCVA Medical Center, Kansas City, Missouri, United States
  • Zhou, Jianping, KCVA Medical Center, Kansas City, Missouri, United States
  • Chen, Maohui, KCVA Medical Center, Kansas City, Missouri, United States
  • Sharma, Ram, KCVA Medical Center, Kansas City, Missouri, United States
  • Srivastava, Tarak, Children's Mercy Hospital, Kansas City, Missouri, United States
  • McCarthy, Ellen T., University of Kansas Medical Center, Kansas City, Kansas, United States
  • Gauchat, Jean-francois, University of Montreal/Montreal Neurological Institute, Montreal, Quebec, Canada
  • Savin, Virginia J., KC VA Medical Center, Kansas City, Kansas, United States
Background

We detected CLCF1 in recurrent FSGS plasma and showed that it increased glomerular permeability (Palb). Cytokine Receptor-Like Factor 1 (CRLF1) was not detected although it may be secreted and circulate as a heterodimer with CLCF1. CLCF1-CRLF1 or JAK2/STAT3 inhibitors blocked the increase in Palb induced by FSGS serum or by monomeric CLCF1 (Sharma et al, Trans Res 2015;166:384-398). A role for JAK-STAT signaling is supported by its activation in PBMC and kidney tissue of FSGS patients (Tao et al, 2018 Kid Int 94:795-808). The current studies aimed to determine the podocyte effects of CLCF1, CLCF1-CRLF1 and JAK inhibitors on the JAK-STAT system.

Methods

Immortalized murine podocytes were treated with CLCF1, CLCF1-CRLF1 or JAK inhibitors Tofacitinib (Tofa), Baricitinib (Bari) and Ruxolitinib (Rux). Total and phosphorylated (p) STATs and JAKs and expression of SOC and PIAS were analyzed using SDS-PAGE and Western blotting with β-actin as the loading control. Expression of CLCF1 receptor sub-units was determined using RT-qPCR and immunofluorescence.

Results

Podocytes express the components of the CLCF1 receptor complex, CNTFRα, gp130 and LIFRβ, and express (in order of protein expression) JAK2>JAk3>JAK1, and STAT3>STAT1>STAT6 >STAT5, as well as SOCS isoforms (3>2>1) and PIAS (3>4>1). CLCF1 (10-1000ng/mL) upregulated pJAK2 (max at 100ng/mL CLCF1) and pJAK3 (max at 1000ng/mL CLCF1) (each P<0.001). Tyr1007 was the major site of phosphorylation on JAK2. CLCF1 (10-1000ng/mL) upregulated pSTAT3 Tyr705 in a time-dependent manner (max at 100ng/mL CLCF1, 15 min, P<0.001).
Heterodimer CLCF1-CRLF1 attenuated CLCF1-induced phosphorylation of JAK2Tyr1007 and STAT3Tyr705 in a dose-dependent manner (max at 1:2 mol, P<0.001). JAK inhibitors Tofa, Bari, and Rux also attenuated CLCF1-induced pSTAT3Tyr705. SOCS were upregulated by CLCF1 (100ng/mL) in the order SOCS3>SOC2 (P<0.001). CLCF1 (100ng/mL, 15 min) upregulated only PIAS3.

Conclusion

Monomeric CLCF1 influences FSGS-associated podocyte pathophysiology through JAK-STATs and their modulators. CRLF1 may inhibit these effects while clinically available JAK inhibitors may provide effective therapy. Podocyte-specific expression of JAK, STAT, SOCS and PIAS isoforms provides opportunity for developing additional targets for treating FSGS.

Funding

  • NIDDK Support