The function of 7D-cadherins: a mathematical model predicts physiological importance for water transport through simple epithelia

Background 7D-cadherins like LI-cadherin are cell adhesion molecules and represent exceptional members of the cadherin superfamily. Although LI-cadherin was shown to act as a functional $ Ca^{2+} $-dependent adhesion molecule, linking neighboring cells together, and to be dysregulated in a variety o...
Ausführliche Beschreibung

Background 7D-cadherins like LI-cadherin are cell adhesion molecules and represent exceptional members of the cadherin superfamily. Although LI-cadherin was shown to act as a functional $ Ca^{2+} $-dependent adhesion molecule, linking neighboring cells together, and to be dysregulated in a variety of diseases, the physiological role is still enigmatic. Interestingly 7D-cadherins occur only in the lateral plasma membranes of cells from epithelia of water transporting tissues like the gut, the liver or the kidney. Furthermore LI-cadherin was shown to exhibit a highly cooperative $ Ca^{2+} $-dependency of the binding activity. Thus it is tempting to assume that LI-cadherin regulates the water transport through the epithelium in a passive fashion by changing its binding activity in dependence on the extracellular $ Ca^{2+} $. Results We developed a simple mathematical model describing the epithelial lining of a lumen with a content of variable osmolarity covering an interstitium of constant osmolarity. The width of the lateral intercellular cleft was found to influence the water transport significantly. In the case of hypertonic luminal content a narrow cleft is necessary to further increase concentration of the luminal content. If the cleft is too wide, the water flux will change direction and water is transported into the lumen. Electron microscopic images show that in fact areas of the gut can be found where the lateral intercellular cleft is narrow throughout the lateral cell border whereas in other areas the lateral intercellular cleft is widened. Conclusions Our simple model clearly predicts that changes of the width of the lateral intercellular cleft can regulate the direction and efficiency of water transport through a simple epithelium. In a narrow cleft the cells can increase the concentration of osmotic active substances easily by active transport whereas if the cleft is wide, friction is reduced but the cells can hardly build up high osmotic gradients. It is now tempting to speculate that 7D-cadherins, owing to their location and their $ Ca^{2+} $-dependence, will adapt their binding activity and thereby the width of the lateral intercellular cleft automatically as the $ Ca^{2+} $-concentration is coupled to the overall electrolyte concentration in the lateral intercellular cleft. This could provide a way to regulate the water resorption in a passive manner adapting to different osmotic conditions. Ausführliche Beschreibung

Autor*in:	Ahl, Mareike [verfasserIn] Weth, Agnes Walcher, Sebastian Baumgartner, Werner

Format:	E-Artikel
Sprache:	Englisch

Erschienen:	2011

Schlagwörter:	Water Transport Water Flux Electrolyte Concentration Osmotic Gradient Luminal Content

Anmerkung:	© Ahl et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (

Übergeordnetes Werk:	Enthalten in: Theoretical biology and medical modelling - London : BioMed Central, 2004, 8(2011), 1 vom: 10. Juni
Übergeordnetes Werk:	volume:8 ; year:2011 ; number:1 ; day:10 ; month:06

Links:	Volltext

DOI / URN:	10.1186/1742-4682-8-18

Katalog-ID:	SPR029127874