Raft-phosphatidylinositol-4,5-bisphosphate (PIP2) is essential for tubular organization of renal papilla

MARÍA GABRIELA MÁRQUEZ; FRANCISCO LEOCATA NIETO; FERNANDEZ TOME M DEL CARMEN; NORMA BEATRIZ STERIN-SPEZIALE

Pinamar, Buenos Aires, Argentina

Congreso; XLI REUNIÓN DE LA SOCIEDAD ARGENTINA DE INVESTIGACIONES BIOQUÍMICAS Y BIOLOGÍA MOLECULAR; 2005

SOCIEDAD ARGENTINA DE INVESTIGACIONES BIOQUÍMICAS Y BIOLOGÍA MOLECULAR (SAIB)

Tubular organization of renal papilla depends on cell-cell and cell matrix attachment, which are principally mediated by adherent junctions (AJ) and focal adhesions (FA), respectively. Vinculin (V) is present in both type of adhesions, and talin (T) only in FA. To investigate whether PIP2 constitutes a molecular platform for the assembly of FA and AJ, we treated cultured collecting duct cells with the raft-disruption agent cyclodextrin (CD), and cell adhesion structures were observed by confocal microscopy. CD caused important changes in cell morphology with loss of cell-cell adhesions and cell retraction, dissipation of V, T and PIP2 from FA accompanied by a distribution in certain zones of the plasma membrane suggesting a delocalization of these proteins from raft, where FA were located before treatment. We also treated cultured cells with the specific plasmmalemal PIP2 sequestering agent neomycin, and with the PIP2 synthesis inhibitor LiCl. Neomycin induced an almost complete loss of V from FA and AJ, and T from FA, and intensity of fluorescence of PIP2 staining appeared to be increased. LiCl induced a dissipation of V from FA and AJ, whereas T ? immunostaining FA remained intact, and PIP2 immunoreactivity was substantially reduced. These results demonstrate that the existence of PIP2-enriched raft is a requirement for the maintenance of FA and AJ that ensures the tubular organization of adult renal tissue.