title: p56lck, LFA-1 and PI3K but not SHP-2 interact with GM1- or GM3-enriched microdomains in a CD4-p56lck association-dependent manner.
abstract: We previously showed that the association of CD4 and G(M3) ganglioside induced by CD4 ligand binding was required for the down-regulation of adhesion and that aggregation of ganglioside-enriched domains was accompanied by transient co-localization of LFA-1 (lymphocyte function-associated antigen-1), PI3K (phosphoinositide 3-kinase) and CD4. We also showed that these proteins co-localized with the G(M1) ganglioside that partially co-localized with G(M3) in these domains. In the present study, we show that CD4-p56(lck) association in CD4 signalling is required for the redistribution of p56(lck), PI3K and LFA-1 in ganglioside-enriched domains, since ganglioside aggregation and recruitment of these proteins were not observed in a T-cell line (A201) expressing the mutant form of CD4 that does not bind p56(lck). In addition, we show that although these proteins associated in different ways with G(M1) and G(M3), all of the associations were dependent on CD4-p56(lck) association. Gangliosides could associate with these proteins that differ in affinity binding and could be modified following CD4 signalling. Our results suggest that through these associations, gangliosides transiently sequestrate these proteins and consequently inhibit LFA-1-dependent adhesion. Furthermore, while structural diversity of gangliosides may allow association with distinct proteins, we show that the tyrosine phosphatase SHP-2 (Src homology 2 domain-containing protein tyrosine phosphatase 2), also required for the down-regulation of LFA-1-dependent adhesion, transiently and partially co-localized with PI3K and p56(lck) in detergent-insoluble membranes without association with G(M1) or G(M3). We propose that CD4 ligation and binding with p56(lck) and their interaction with G(M3) and/or G(M1) gangliosides induce recruitment of distinct proteins important for CD4 signalling to form a multimolecular signalling complex.
authors.affiliation: Inserm, U768, Paris, F-75015, France.
authors.forename: Christiane
authors.initials: C
authors.lastname: Barbat
authors.forename: Maylis
authors.initials: M
authors.lastname: Trucy
authors.forename: Maurizio
authors.initials: M
authors.lastname: Sorice
authors.forename: Tina
authors.initials: T
authors.lastname: Garofalo
authors.forename: Valeria
authors.initials: V
authors.lastname: Manganelli
authors.forename: Alain
authors.initials: A
authors.lastname: Fischer
authors.forename: Fabienne
authors.initials: F
authors.lastname: Mazerolles
mesh_terms: D000906:Antibodies / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000378:metabolism*; D005679:G(M3) Ganglioside / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011485:Protein Binding; D054648:Protein Phosphatase 2; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism
chemical_list: D000906:Antibodies; D015704:CD4 Antigens; D005679:G(M3) Ganglioside; D047908:Intracellular Signaling Peptides and Proteins; D016169:Lymphocyte Function-Associated Antigen-1; D005677:G(M1) Ganglioside; D019869:Phosphatidylinositol 3-Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D054648:Protein Phosphatase 2; C516724:PTPN11 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases