title: CXCL12-induced partitioning of flotillin-1 with lipid rafts plays a role in CXCR4 function.
abstract: Lipid rafts play an important role in signal integration and in the cellular activation of a number of cytokine and growth factor receptors. It has recently been demonstrated that flotillin proteins are recruited to lipid raft microdomains upon cellular activation and play a role in neural cell regeneration, receptor signaling and lymphocyte activation. However, little is known about the relevance of the flotillin proteins during T cell responses to chemoattractant stimulation. To this end, cytoplasmic and lipid raft fractions from human T cells were analyzed for flotillin protein redistribution prior to and after CXCL12 stimulation. Flotillin-1, but not flotillin-2, redistributes to lipid rafts upon CXCR4 ligation. Moreover, in CXCL12-treated T cells, flotillin-1 also associates with several raft proteins including LAT, CD48 and CD11a but not Lck. In addition, an increase in CXCR4 association with flotillin-1 in lipid rafts was observed after chemokine treatment. RNAi technology was also utilized to inhibit the expression of flotillin-1, resulting in an inhibition of CXCL12-mediated signaling, function and CXCR4 recruitment into lipid rafts. Together, these data suggest that the increased association of cellular flotillin-1 with lipid raft microdomains during chemokine exposure may play an important role in chemokine receptor signaling and receptor partitioning with lipid rafts.
authors.affiliation: Laboratory of Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
authors.forename: Banabihari
authors.initials: B
authors.lastname: Giri
authors.forename: Vishwa D
authors.initials: VD
authors.lastname: Dixit
authors.forename: Manik C
authors.initials: MC
authors.lastname: Ghosh
authors.forename: Gary D
authors.initials: GD
authors.lastname: Collins
authors.forename: Islam U
authors.initials: IU
authors.lastname: Khan
authors.forename: Karen
authors.initials: K
authors.lastname: Madara
authors.forename: Ashani T
authors.initials: AT
authors.lastname: Weeraratna
authors.forename: Dennis D
authors.initials: DD
authors.lastname: Taub
mesh_terms: D015153:Blotting, Western; D002448:Cell Adhesion / Q000276:immunology; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000276:immunology* / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D008213:Lymphocyte Activation / Q000276:immunology; D021962:Membrane Microdomains / Q000276:immunology* / Q000378:metabolism; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism; D021381:Protein Transport / Q000276:immunology; D034741:RNA, Small Interfering; D019718:Receptors, CXCR4 / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D014162:Transfection
chemical_list: C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D019718:Receptors, CXCR4; C106354:flotillins