Segregation of leading-edge and uropod components into specific lipid rafts during T cell polarization

Redistribution of specialized molecules in migrating cells develops asymmet ry between two opposite cell poles, the leading edge and the uropod. We sho w that acquisition of a motile phenotype in T lymphocytes results in the as ymmetric redistribution of ganglioside GM3- and GM1-enriched raft domains t o the leading edge and to the uropod, respectively. This segregation to eac h cell pole parallels the specific redistribution of membrane proteins asso ciated to each raft subfraction. Our data suggest that raft partitioning is a major determinant for protein redistribution in polarized T cells, as ec topic expression of raft-associated proteins results in their asymmetric re distribution, whereas non-raft-partitioned mutants of these proteins are di stributed homogeneously in the polarized cell membrane. Both acquisition of a migratory phenotype and SDF-1 alpha -induced chemotaxis are cholesterol depletion-sensitive. Finally, GM3 and GM1 raft redistribution requires an i ntact actin cytoskeleton, but is insensitive to microtubule disruption. We propose that membrane protein segregation not only between raft and nonraft domains but also between distinct raft subdomains may be an organizational principle that mediates redistribution of specialized molecules needed for T cell migration.