Intercellular adhesion in the cellular slime mold Polysphondylium pallidum inhibited by interaction of asialofetuin or specific univalent antibody with endogenous cell surface lectin☆

摘要

Previousworkhasshownthat,asamoebaeofthecellularslimemoldPolysphondyliumpallidumbecomeaggregationcompetent,theyaccumulateontheircellsurfaceacarbohydrate-bindingprotein(lectin)namedpallidin.Theseamoebaealsopossesscellsurfacereceptors,presumedtocontaincomplexoligosaccharideswithahighaffinityfortheendogenouslectin.Iflectin-receptorinteractionsmediatecell-cellcontact,thenappropriateconcentrationsofpallidininhibitorsshouldblockcellcohesion.Twopotentmacromolecularantagonistsofthelectinwereemployed:thedesialylatedformoftheglycoproteinfetuinandtheunivalentantibody(Fab)preparedagainstpallidin.Westudiedtheeffectsoftheseinhibitorsonrotation-mediatedaggregationofP.pallidumamoebaeunderavarietyofassayconditions.Amoebaeexposedtohypertonicconditionsortoantimetabolites(a€?Permissiveconditionsa€?)wereselectivelyblockedfromassociatingbymicrogramquantitiesofthelectininhibitors,whereascellsinisotonicbuffer(a€?nonpermissiveconditiona€?)wereonlyslightlyaffected.Acomparisonofthemorphologyofagglutinatesformedunderthevariousconditionsallowsseveralexplanationsforthedifferentsusceptibilitiestoinhibitionbyantipallidinreagents.Althoughnotconclusive,theworksupportsamodelofcelladhesioninthissimpleeukaryoticsystembasedatleastinpartonspecificinteractionsbetweencarbohydrate-bindingproteinsandreceptorsonadjoiningcells.