Raft-phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) is essential for the maintenance of mature focal adhesión (FA) plaque

MÁRQUEZ MG; LEOCATA NIETO, FRANCISCO; GAGLIANO L; FERNANDEZ TOME M DEL CARMEN; FAVALE NICOLAS; NORMA STERIN-SPEZIALE

Ajaccio, Corsega

Congreso; 46th INTERNATIONAL CONFERENCE ON THE BIOSCIENCE OF LIPIDS (ICBL); 2005

INTERNATIONAL CONFERENCE ON THE BIOSCIENCE OF LIPIDS

Renal papilla is a highly organized tissue whose functionality depends on tubular organization by cell attachment to the extracellular matrix. Mature focal adhesion plaques (FA) are the most stable cell-matrix points of adhesion which involves the FA-protein vinculin (V). PI-4,5-P2, a minor membrane phospholipid usually implicated in cell signaling, is now recognized to be a principal molecule in tissue organization since is required for activation of vinculin. Since, it has been found that raft-microdomains are enriched in PI-4,5-P2 it has been recently suggested that FA have a lipid-raft like composition, however, no direct evidence is available respect to FA localization in specific raft microdomains in any cellular type. In the present work we describe, in rat renal papilla a specific FA-enriched in the typical raft lipids: sphingomyelin and cholesterol. Such microdomains are also largely enriched in PI-4P and PI-4,5-P2 (32 and 5-fold incrase) and in unsaturated phosphatidylethanolamine. Immunofluorescence analysis of cultured collecting duct cells treated with cyclodextrin evoked disappearance of FA but V and PI-4,5-P2 still remained in the plasma membrane denoting that FA assembly needs raft integrity. LiCl or neomycin treatment decreased the amount of raft associated-V and induced FA dissipation, reflecting that such proteins have to be bound to PI-4,5-P2 to be assembled in a FA structure. The results demonstrate that the existence of PI-4,5-P2 enriched-raft is a requirement for the maintenance of mature FA plaques that ensures the tubular organization of adult renal tissue.