Abstract: TH-PO062

TRPM4 Is Expressed at the Apical Surface of Podocyte Just Above Slit Diaphragm, and Its Altered Expression Is Involved in Podocyte Injury

Session Information

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • Zhang, Ying, Kidney Research Center, Niigata University, Niigata, Japan
  • Fukusumi, Yoshiyasu, Kidney Research Center, Niigata University, Niigata, Japan
  • Kawachi, Hiroshi, Kidney Research Center, Niigata University, Niigata, Japan
Background

TRPC6, a member of TRP channels is reported to play an important role in regulating the slit diaphragm (SD) function. To explore novel molecules involved in the development of proteinuria, we performed cDNA subtraction assay and RNA-seq analysis. 293 molecules were identified to be decreased to less than 20 % in PAN nephropathy. We found transient receptor potential melastatin 4 (TRPM4), another member of TRP channels was clearly downregulated. In this study we examined the expression and localization of TRPM4 in glomeruli and its possible roles in pathogenesis of proteinuria.

Methods

The expression and the localization of TRPM4 under the physiological and pathological conditions were analyzed by real-time PCR, dual-labeling immunofluorescence and Western blot. We prepared three rat models, PAN nephropathy, a mimic of MCNS, ADR nephropathy, a mimic of FSGS and anti-nephrin antibody (ANA) induced nephropathy, which is characterized as a slit diaphragm specific dysfunction.

Results

The mRNA expression of TRPM4 in glomeruli was more extensive than that in renal cortex and other tissues. The expression of TRPM4 was also detected in cultured mouse podocytes. Immunostaining of TRPM4 in renal cortex was restricted to glomeruli, and it was observed to be a discontinuous linear pattern along the glomerular capillary loops. TRPM4 staining was slightly aside from nephrin, an extracellular component of the SD, and some portions of TRPM4 were colocalized with podocyte apical membrane marker podocalyxin. TRPM4 first appeared in the presumptive podocytes in early S-shaped body stage, when nephrin was not detected yet. The mRNA expression of TRPM4 was evidently decreased immediately after disease induction (1h: 10 % in ANA, 31 % in PAN) and the decrease was still detected when proteinuria peaked (42 %, 57 %). The immunostaining of TRPM4 shifted to a discontinuous patchy pattern in PAN nephropathy. The staining intensity of TRPM4 was lowered in ANA nephropathy and ADR nephropathy.

Conclusion

TRPM4 is expressed at the apical surface of podocyte just above slit diaphragm. The mRNA expression of TRPM4 was clearly decreased before the onset of proteinuria. The immunostaining of TRPM4 was altered in proteinuric states. It is conceivable that the altered expression of TRPM4 is involved in initiating the slit diaphragm dysfunction.

Funding

  • Government Support - Non-U.S.