title: Direct interaction, instrumental for signaling processes, between LacCer and Lyn in the lipid rafts of neutrophil-like cells.
abstract: Lactosylceramide [LacCer; β-Gal-(1-4)-β-Glc-(1-1)-Cer] has been shown to contain very long fatty acids that specifically modulate neutrophil properties. The interactions between LacCer and proteins and their role in cell signaling processes were assessed by synthesizing two molecular species of azide-photoactivable tritium-labeled LacCer having acyl chains of different lengths. The lengths of the two acyl chains corresponded to those of a short/medium and very long fatty acid, comparable to the lengths of stearic and lignoceric acids, respectively. These derivatives, designated C18-[(3)H]LacCer-(N3) and C24-[(3)H]LacCer-(N3), were incorporated into the lipid rafts of plasma membranes of neutrophilic differentiated HL-60 (D-HL-60) cells. C24-[(3)H]LacCer-(N3), but not C18-[(3)H]LacCer-(N3), induced the phosphorylation of Lyn and promoted phagocytosis. Incorporation of C24-[(3)H]LacCer-(N3) into plasma membranes, followed by illumination, resulted in the formation of several tritium-labeled LacCer-protein complexes, including the LacCer-Lyn complex, into plasma membrane lipid rafts. Administration of C18-[(3)H]LacCer-(N3) to cells, however, did not result in the formation of the LacCer-Lyn complex. These results suggest that LacCer derivatives mimic the biological properties of natural LacCer species and can be utilized as tools to study LacCer-protein interactions, and confirm a specific direct interaction between LacCer species containing very long fatty acids, and Lyn protein, associated with the cytoplasmic layer via myristic/palmitic chains.
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Chiricozzi
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Ciampa
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Brasile
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Compostella
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Prinetti
authors.affiliation: Institute for Environmental Gender-Specific Medicine, Juntendo University Graduate School of Medicine, Chiba, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nakayama
authors.affiliation: Institute for Environmental Gender-Specific Medicine, Juntendo University Graduate School of Medicine, Chiba, Japan.
authors.forename: Roudy C
authors.initials: RC
authors.lastname: Ekyalongo
authors.affiliation: Institute for Environmental Gender-Specific Medicine, Juntendo University Graduate School of Medicine, Chiba, Japan.
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Iwabuchi
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Sonnino
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, University of Milan, Milano, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Mauri
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D001386:Azides / Q000737:chemistry; D002470:Cell Survival / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D007790:Lactosylceramides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology* / Q000276:immunology; D010587:Phagocytosis / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D015398:Signal Transduction / Q000187:drug effects; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D001386:Azides; D007790:Lactosylceramides; C009744:CDw17 antigen; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases
keywords: C24 fatty acid chain; interdigitation; lactosylceramide; photoactivable sphingolipids