Glycosylation affects translocation of integrin, Src, and caveolin into orout of GEM

Endogenous GM3 synthesis and full N-glycosylation in membrane receptors occ urred in "4-epimerase-less" ldlD (Krieger's CHO mutant) cells cultured in G al-containing medium, whereby components of detergent-insoluble, low-densit y, buoyant membrane fraction, termed "glycolipid-enriched microdomain (GEM) ," varied significantly by translocation into or out of GEM. Integrins alph a 3 and alpha 5 were translocated into GEM in the presence of 0.5 or 0.25% Triton X-100, particularly in the absence of Gal, whereby integrins are und erglycosylated and GlcCer is the major glycolipid component in GEM. Src fam ily kinase was translocated into and enriched in GEM fractions when prepare d in 0.5 or 0.25% Triton X-100 from cells grown in Gal-containing medium, w hereby GM3 synthesis is induced. In contrast, caveolin is highly enriched i n GEM when GM3 synthesis does not occur, and is translocated into high-dens ity membrane fraction when GM3 synthesis occurs. The results suggest that l evels of key molecules controlling cell adhesion and signaling are defined by translocation into or out of GEM, which depends on glycosylation state. (C) 2000 Academic Press.