uPA binding increases uPAR localization to lipid rafts and modifies the receptor microdomain composition.

SAHORES MM; PRINETTI A; CHIABRANDO GA; BLASI F; SONNINO S

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

Elsevier

Lugar: Reino Unido; Año: 2008 vol. 1778 p. 250 - 259

0005-2736

UPAR is a GPI anchored protein which is found in both lipid rafts and the more fluid regions of the plasma membrane. We have studied the role of the ligand uPA on uPAR localization and on the composition of the lipid membrane microdomains. We have analyzed the (glyco)sphingolipid environment of uPAR in detergent resistant membrane (DRM) fractions prepared by cell lysis with 1% Triton X-100 and fractionated by sucrose gradient centrifugation. The uPAR specific lipid membrane microdomain has been separated from the total DRM fraction by immunoprecipitation with an anti-uPAR specific antibody under conditions that preserve membrane integrity. Our results show that in HEK293-uPAR cells, uPAR is partially associated with DRM and this association increases after ligand binding, independent of the catalytic activity of uPA. In the absence of ligands, uPAR experiences a lipid environment very similar to that of total DRM, enriched in sphingomyelin and glycosphingolipids. However, after treatment of cells with uPA or ATF the lipid environment is strongly impoverished of neutral glycosphingolipids.