title: Shed gangliosides provide detergent-independent evidence for type-3 glycosynapses.
abstract: Membrane microdomains, or rafts, at the plasma membrane have been invoked to explain many cellular processes. Protein-protein interactions within such microdomains including, for example, the tetraspanin web are reported to provide a scaffold for signal transduction. However, the nature of such protein-protein interactions is not fully elucidated. Hakomori [S.I. Hakomori, The glycosynapse, Proc. Natl. Acad. Sci. USA 99 (2002) 225-232] has advanced the concept that glycosphingolipids, particularly gangliosides, provide the intermediary link between transmembrane receptors and signal transducers and has redefined membrane rafts as Type-1, -2 or -3 glycosynapses. Here, using simple immunofluorescent analysis of the ganglioside complexes naturally released from cellular microprocesses (termed "footprints") we show that the ganglioside can determine the nature of protein-protein associations. Specifically, we demonstrate that CD36 and the tetraspanin CD151, both of which interact with beta1 integrins, associate together only in the presence of the gangliosides GD2/GD3. These results substantiate the glycosynapse hypothesis and suggest that the nature of the tetraspanin web may be determined by gangliosides.
authors.affiliation: Cancer Research Unit, School of Biomedical Sciences, The University of Newcastle, NSW, Australia. Rick.Thorne@newcastle.edu.au
authors.forename: Rick F
authors.initials: RF
authors.lastname: Thorne
authors.forename: Nizar M
authors.initials: NM
authors.lastname: Mhaidat
authors.forename: Kylie J
authors.initials: KJ
authors.lastname: Ralston
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Burns
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D018955:CD36 Antigens / Q000378:metabolism; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D003902:Detergents / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019084:Fluorescent Antibody Technique, Indirect; D005732:Gangliosides / Q000737:chemistry / Q000378:metabolism*; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors; D006028:Glycosphingolipids / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009025:Morpholines / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D060185:Tetraspanin 24
chemical_list: D015703:Antigens, CD; C554715:CD151 protein, human; D018955:CD36 Antigens; D003902:Detergents; D004791:Enzyme Inhibitors; D005732:Gangliosides; D006028:Glycosphingolipids; D009025:Morpholines; D011956:Receptors, Cell Surface; D060185:Tetraspanin 24; C033110:RV 538; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase