Kidney Week

Abstract: SA-PO306

Claudin 10b Is a Target for Parathyroid Hormone (PTH) in the Cortical Thick Ascending Limb (CTAL)

Session Information

• Fluid and Electrolytes: Basic - II
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid and Electrolytes

• 901 Fluid and Electrolytes: Basic

Authors

• Prot-Bertoye, Caroline, INSERM, UMRS1138- CNRS- ERL8228, Paris, France

Caroline Prot-Bertoye,

• Figueres, Lucile, INSERM, UMRS1138- CNRS- ERL8228, Paris, France

Lucile Figueres,

• Ferriere, Elsa, INSERM, UMRS1138- CNRS- ERL8228, Paris, France

Elsa Ferriere,

• Brideau, Gaëlle, INSERM, UMRS1138- CNRS- ERL8228, Paris, France

Gaëlle Brideau,

• Griveau, Camille, INSERM, UMRS1138- CNRS- ERL8228, Paris, France

Camille Griveau,

• Chaussain, Catherine, 3 EA 2496, Laboratory Orofacial Pathologies, Imaging and Biotherapies, Dental School, Paris Descartes University, Paris, France

Catherine Chaussain,

• Bardet, Claire, 3 EA 2496, Laboratory Orofacial Pathologies, Imaging and Biotherapies, Dental School, Paris Descartes University, Paris, France

Claire Bardet,

• Breiderhoff, Tilman, Department of Pediatric Nephrology, Charité - Universitätsmedizin Berlin, Berlin, Germany

Tilman Breiderhoff,

• Müller, Dominik, Department of Pediatric Nephrology, Charité - Universitätsmedizin Berlin, Berlin, Germany

Dominik Müller,

• Houillier, Pascal, INSERM, UMRS1138- CNRS- ERL8228, Paris, France

Pascal Houillier,

Background

In the CTAL, 25% of the filtered calcium is reabsorbed, along the paracellular pathway ; the reabsorption is driven by the lumen-positive transepithelial voltage (Vte). Vte depends on the back diffusion of sodium (Na) along the paracellular pathway. The expression of claudin 10b (Cldn10b) at tight junction makes the paracellular permeability to Na (P_Na) greater than that of chloride (P_Cl). PTH increases calcium reabsorption across the CTAL but the mechanisms involved are uncertain.
We assessed whether the effect of PTH in the CTAL involves Cldn10b, which determines Vte and P_Na/P_Cl, and aimed at identifying the underlying mechanisms.

Methods

CTAL dissected from Cldn10^+/+ and Cldn10^-/- male mice were microperfused in vitro to measure Vte and P_Na/P_Cl under asymmetrical conditions with 0.1 mM furosemide in the lumen. All measurements were made under control and/or after peritubular addition of PTH (10^-10M), phorbol 12-Myristate 13-Acetate (PMA, 10^-6M), dibutyryl cAMP (dbcAMP 5.10^-4M), ionomycin (10^-7M), PKI 14-22 amide (a protein kinase A inhibitor, 10^-6M), trifluoroperazine (TFP, a calcium-calmodulin kinase antagonist, 10^-4M), or Dyngo4a (a clathrin-mediated endocytosis inhibitor, 10^-5 M).The ratio of permeabilities P_Na/P_Cl was calculated according to the Goldman-Hodgkin-Katz equation.

Results

PTH significantly increased P_Na/P_Cl in Cldn10^+/+ CTAL (p=0.0002) but not in Cldn10^-/- CTAL. This effect was reproduced by dbcAMP (p=0.02) and ionomycin (p=0.047), but not by PMA. PKI, TFP and Dyngo4a inhibited the effect of PTH on P_Na/P_Cl.

Conclusion

We conclude that, in the mouse CTAL, PTH increases P_Na/P_Cl via a cAMP-, and calcium calmodulin kinase-dependent effect on Cldn10b. Inhibition of the clathrin-mediated endocytosis prevents this effect.
Our results show that the properties of intercellular tight junctions can be directly and rapidly altered by intracellular signaling pathways and changes in intracellular protein trafficking.

Funding

• Government Support - Non-U.S.