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Claudin function in the thick ascending limb of Henle's loop
Dorothee Günzel1, Lea Haisch, Sandra Pfaffenbach
1Institute of Clinical Physiology, Charité, Berlin, Germany. dorothee.guenzel@charite.de
Annals of the New York Academy of Sciences
|June 23, 2009
Summary
Claudins, particularly claudin-16 and claudin-19, are crucial for kidney cation handling. Mutations impairing these claudins cause renal mineral imbalances, with mechanisms still under investigation.
Area of Science:
- Nephrology
- Molecular Biology
- Cell Biology
Background:
- Claudins are key regulators of paracellular permeability in epithelia.
- Kidney nephron segments express distinct claudin patterns.
- The thick ascending limb of Henle's loop (TAL) has high cation permeability and co-expresses multiple claudins, including claudin-10, -16, and -19.
Purpose of the Study:
- To summarize the function of kidney claudins, focusing on claudin-16 and -19.
- To review mutations in claudin-16 and -19 genes and their clinical consequences.
- To explore the mechanistic links between claudin-16/-19 function and renal mineral handling disorders.
Main Methods:
- Review of in vitro functional studies on kidney claudins.
- Analysis of reported mutations in human CLDN16 and CLDN19 genes.
- Synthesis of clinical data on hypomagnesemia, hypercalciuria, and nephrocalcinosis.
Main Results:
- Mutations in claudin-16 and claudin-19 genes lead to impaired renal calcium and magnesium handling, causing hypomagnesemia, hypercalciuria, and nephrocalcinosis.
- Reported mutations affect claudin localization, membrane stability, or function.
- In vitro studies show varied effects of claudin-16 and -19 on ion permeability, suggesting complex roles in paracellular transport.
Conclusions:
- Claudin-16 and -19 are essential for normal renal magnesium and calcium homeostasis.
- The precise mechanisms linking claudin-16/-19 dysfunction to clinical symptoms remain unclear.
- A hypothesized mechanism involves paracellular back-leak of magnesium and calcium in the distal convoluted tubule due to altered TAL function.
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