Zymogen-locked mutant prostasin (Prss8) leads to incomplete proteolytic activation of the epithelial sodium channel (ENaC) and severely compromises triamterene tolerance in mice.

Abstract

AIM:

The serine protease prostasin (Prss8) is expressed in the distal tubule and stimulates proteolytic activation of the epithelial sodium channel (ENaC) in co-expression experiments in vitro. The aim of this study was to explore the role of prostasin in proteolytic ENaC activation in the kidney in vivo.

METHODS:

We used genetically modified knockin mice carrying a Prss8 mutation abolishing proteolytic activity (Prss8-S238A) or a mutation leading to a zymogen-locked state (Prss8-R44Q). Mice were challenged with low sodium diet and diuretics. Regulation of ENaC activity by Prss8-S238A and Prss8-R44Q was studied in vitro using the Xenopus laevis oocyte expression system.

RESULTS:

Co-expression of murine ENaC with Prss8-wt or Prss8-S238A in oocytes caused maximal proteolytic ENaC activation, whereas ENaC was activated only partially in oocytes co-expressing Prss8-R44Q. This was paralleled by a reduced proteolytic activity at the cell surface of Prss8-R44Q expressing oocytes. Sodium conservation under low sodium diet was preserved in Prss8-S238A and Prss8-R44Q mice but with higher plasma aldosterone concentrations in Prss8-R44Q mice. Treatment with the ENaC inhibitor triamterene over four days was tolerated in Prss8-wt and Prss8-S238A mice, whereas Prss8-R44Q mice developed salt wasting and severe weight loss associated with hyperkalemia and acidosis consistent with impaired ENaC function and renal failure.

CONCLUSION:

Unlike proteolytically inactive Prss8-S238A, zymogen-locked Prss8-R44Q produces incomplete proteolytic ENaC activation in vitro and causes a severe renal phenotype in mice treated with the ENaC inhibitor triamterene. This indicates that Prss8 plays a role in proteolytic ENaC activation and renal function independent of its proteolytic activity.

• Authors: Daniel Essigke, Alexandr V Ilyaskin, Matthias Wörn, Bernhard N Bohnert, Mengyun Xiao, Christoph Daniel, Kerstin Amann, Andreas L Birkenfeld, Roman Szabo, Thomas H Bugge, Christoph Korbmacher, Ferruh Artunc
• Journal: Acta physiologica (Oxford, England) (Acta Physiol (Oxf)) Vol. 232 Issue 1 Pg. e13640 (05 2021) ISSN: 1748-1716 [Electronic] England
• PMID: 33650216 (Publication Type: Journal Article, Research Support, N.I.H., Intramural, Research Support, Non-U.S. Gov't)
• Copyright: © 2021 The Authors. Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.

Chemical References

• Enzyme Precursors
• Epithelial Sodium Channels
• Serine Endopeptidases
• prostasin
• Triamterene

Topics

• Animals
• Enzyme Precursors
• Epithelial Sodium Channels
• Mice
• Oocytes (metabolism)
• Serine Endopeptidases (metabolism)
• Triamterene
• Xenopus laevis (metabolism)