Specific DRM lipid composition is essential to maintain the integrity of epithelial cell adhesion structures in rat renal papilla

M.G. MÁRQUEZ, F. LEOCATA, N FAVALE, M.C. FERNÁNDEZ-TOMÉ, N. STERIN-SPEZIALE

Pecs, Hungria

Congreso; 47 th International Conference on the Bioscience of Lipids; 2006

International Conference on the Bioscience of Lipids (ICBL)

Adherens junctions (AJ) and focal adhesions (FA) mediate cell-cell and cell-extracellular matrix adhesion respectively. FA structure is associated with detergent resistant microdomains (DRM), but lesser information is available about AJ proteins. In previous work we described, in rat renal papilla, a specific DRM enriched in sphingomyelin and cholesterol, that contained FA proteins. Changes in DRM lipid composition provoked by cyclodextrin (CD), neomycin (Neo) and LiCl induced dissipation of FA structures from cultured collecting duct cells. Now, we show that this specific DRM also contains AJ proteins E-cadherin and b-catenin. Western blot analysis shows that changes in DRM lipid composition induced by CD provokes a 10% and 50% decrease in the amount of E-cadherin and b-catenin present in DRM, respectively. Neo induces a more important decrease in b-catenin than in E-cadherin, while LiCl induces no changes in E-cadherin and a decrease in almost 25% of b-catenin. Immunofluorescence analysis of control cultured collecting duct cells shows continuous E-cadherin and b-catenin immunostaining at cell borders marking the AJ. CD and Neo induce relocation of E-cadherin and cells cannot adhere to each other, but minor changes are observed after LiCl treatment. b-catenin staining localizes in a submembrane region after CD treatment, suggesting delocalization from the plasma membrane, becomes discontinuous after Neo treatment, and remains along cell boundaries with a lesser intensity after LiCl incubation. Our results provide evidence that changes in the lipidic composition of DRM modulates the behaviour of proteins involved in cell adhesion structures, essential to maintain renal papillary tubular organization.