Association of MUC-1 and PSGL-1 with low-density microdomain in T-lymphocytes: A preliminary note

Two mucin-type glycoproteins, MUC-1 and P-selectin glycoprotein ligand-1 (P SGL-1), and glycosphingolipids (GSLs), expressed in human T-cell line HUT78 , were highly enriched in low-density buoyant fraction (termed "GEM"), toge ther with CD45, Yes, Fyn, and Ick(56). Enrichment of MUC-1, PSGL-1 and GSLs , together with these signal transducer molecules in low-density membrane f raction was observable when fraction was prepared from cells either in noni onic detergent Brij 58 or in hypertonic alkaline conditions (500 mM Na2CO3) . On pretreatment of cells with cholesterol-binding reagent methyl beta -cy clodextrin, levels of MUC-1 and PSGL-1 together with the above signal trans ducers in GEM was greatly reduced, and they were translocated into high-den sity membrane fraction. Similar association of lck(58), Yes, Fyn, and cSrc together with MUC-1 was also found in GEM fraction of mouse T-cell lymphoma EL4 cells expressing MUC-1 through transfection of its gene. These finding s indicate the presence of another glycosyl cluster ("glycocluster"), in ad dition to the previously well-established GSL cluster organized with signal transducer molecules in GEM fraction, and its possible functional role in T-cells. (C) 2001 Academic Press.