title: Capping of cholera toxin-ganglioside GM1 complexes on mouse lymphocytes is accompanied by co-capping of alpha-actinin.
abstract: We used cholera toxin, which binds exclusively and with a high affinity to the ganglioside GM1, as a probe to investigate the distribution of this glycolipid on the surface of mouse lymphocytes. When lymphocytes are incubated with cholera toxin (or its B subunit) and then sequentially with horse anti-toxin and FITC-swine anti-horse Ig at 37 degrees C, the cholera toxin-ganglioside GM1 complex is redistributed to a cap at one pole of the cell. The capping of cholera toxin-GM1 complexes is slower than the capping of surface-Ig complexes, requires two antibodies, and is inhibited at high toxin concentrations. Cholera toxin-GM1, like surface-Ig capping, is an energy-dependent process and is inhibited by sodium azide, low temperatures, or cytochalasin B, but is unaffected by demecolcine. An affinity-purified antibody against alpha-actinin was used to examine the distribution of this cytoskeletal component during the capping process. 88% of the cells that had a surface Ig cap displayed a co-cap of alpha-actinin, and 57% of the cells that had a cholera toxin-GM1 cap displayed a co-cap of alpha-actinin. Time course studies revealed similar kinetics of external ligand cap formation and the formation of alpha-actinin co-caps. We conclude that capping of a cell-surface glycolipid is associated with a reorganization of the underlying cytoskeleton. The implications of such an association are discussed in the context of current models of the mechanism of capping.
mesh_terms: D000185:Actinin / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D007152:Immunologic Capping; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000276:immunology / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009124:Muscle Proteins / Q000378:metabolism*
chemical_list: D005732:Gangliosides; D008563:Membrane Lipids; D009124:Muscle Proteins; D000185:Actinin; D005677:G(M1) Ganglioside; D002772:Cholera Toxin