title: Involvement of the Galbeta1 - 3GalNAcbeta structure in the recognition of apoptotic bodies by THP-1 cells.
abstract: A specific apoptotic glycosylation pattern may play an assistant or even a causative role in phagocytosis of apoptotic bodies. To elucidate the role of macrophages in lectin-mediated phagocytosis, an experimental system was used, where monocyte-derived THP-1 cells engulf the apoptotic bodies from the melanoma cell line MELJUSO. A flow cytometry assay was performed to reveal lectin expression and quantify the phagocytosis of apoptotic bodies. Taking into account that siglecs, a mannose receptor and galectins expressed on macrophages could be involved in engulfment of apoptotic bodies we studied their potential expression on THP-1 cells by means of polyacrylamide glycoconjugates. A strong binding of the cells to siglec ligands (3'SiaLac, 6'SiaLac, [Neu5Acalpha2-8]2) and galectin ligands (LacNAc, GalNAcbeta1 - 4GlcNAc, Galbeta1 - 3GalNAcbeta and asialoGM1) was observed. To reveal the corresponding targets on apoptotic bodies, the carbohydrate pattern of MELJUSO cells was analyzed. The apoptotic membrane was characterized by a high level of glycans terminated by galactose or sialic acid. To study lectin-mediated phagocytosis of apoptotic bodies by THP-1 cells, an inhibitory phagocytosis assay was performed. Binding of Galbeta1 - 3GalNAc- or LacNAc-specific reagents (lectins and antibodies) to apoptotic bodies abolished their engulfment by the THP-1 cells whereas blocking of Neu5Acalpha2 - 6 or Neu5Acalpha2 - 3 sites by the corresponding lectins was not effective. Furthermore, Galbeta1 - 3GalNAcbeta-PAA or asialoGM1-PAA binding to the THP-1 cells decreased phagocytosis, whereas two other potent THP-1-binding probes, LacNAc-PAA and GalNAcbeta1 - 4GlcNAc-PAA did not inhibit phagocytosis. Thus, Galbeta1 - 3GalNAcbeta-terminated chains represented on the apoptotic bodies but not the other tested galectin ligands appear to be a target for THP-1 cells.
authors.affiliation: Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Rapoport
authors.forename: Sergei
authors.initials: S
authors.lastname: Khaidukov
authors.forename: Olga
authors.initials: O
authors.lastname: Baidina
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bojenko
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Moiseeva
authors.forename: Galina
authors.initials: G
authors.lastname: Pasynina
authors.forename: Uwe
authors.initials: U
authors.lastname: Karsten
authors.forename: Nikolay
authors.initials: N
authors.lastname: Nifant'ev
authors.forename: Jacques
authors.initials: J
authors.lastname: LePendue
authors.forename: Nicolai
authors.initials: N
authors.lastname: Bovin
mesh_terms: D017209:Apoptosis; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry; D002460:Cell Line; D005434:Flow Cytometry / Q000379:methods; D037161:Galectins / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D002241:Carbohydrates; D037161:Galectins; D013755:Tetradecanoylphorbol Acetate