RESUMO
Disialosyl globopentaosylceramide (DSGb5) is often expressed by renal cell carcinomas. To investigate properties of DSGb5, we have prepared its oligosaccharide moiety by chemically synthesizing Gb5 which was enzymatically sialylated using the mammalian sialyltransferases ST3Gal1 and ST6GalNAc5. Glycan microarray binding studies indicate that Siglec-7 does not recognize DSGb5, and preferentially binds Neu5Acα(2,8)Neu5Ac containing glycans.
Assuntos
Carcinoma de Células Renais/química , Inibidores Enzimáticos/farmacologia , Globosídeos/farmacologia , Neoplasias Renais/química , Oligossacarídeos/farmacologia , Sialiltransferases/antagonistas & inibidores , Antígenos de Neoplasias , Configuração de Carboidratos , Inibidores Enzimáticos/química , Globosídeos/síntese química , Globosídeos/química , Células HEK293 , Humanos , Análise em Microsséries , Oligossacarídeos/química , Sialiltransferases/metabolismo , beta-Galactosídeo alfa-2,3-SialiltransferaseRESUMO
Isoglobotrihexosylceramide (iGb3) is an endogenous antigen of mammalian cells and can stimulate invariant natural killer T (iNKT) cells to evoke autoimmune activities by the release of T helper 1 (Th1) and Th2 cytokines. Th1 cytokines are correlated with the antitumor and antiviral response, while Th2 cytokines are correlated with the amelioration of autoimmune diseases. iGb3 is a very weak agonist compared to the exogenous alpha-galactosylceramide; however, modification of the ceramide moiety has been advocated as one of the approaches to improve its stimulatory activity and to change the bias of release of Th1 and Th2 cytokines. Two analogues of iGb3, 2H-iGb3 and HO-iGb3 with different ceramide moieties, were synthesized. Bioassay results showed that HO-iGb3 was much more effective in stimulating iNKT cells than iGb3 at low concentration. The assay also showed that the CD1d/2H-iGb3 complexes are remarkably efficient in stimulating iNKT cells.
Assuntos
Globosídeos/síntese química , Células Matadoras Naturais/efeitos dos fármacos , Ativação Linfocitária/efeitos dos fármacos , Receptores de Antígenos de Linfócitos T/agonistas , Triexosilceramidas/síntese química , Antígenos CD1/metabolismo , Antígenos CD1d , Sequência de Carboidratos , Linhagem Celular , Globosídeos/química , Globosídeos/farmacologia , Humanos , Interferon gama/biossíntese , Interleucina-4/biossíntese , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Ligação Proteica , Estereoisomerismo , Relação Estrutura-Atividade , Triexosilceramidas/química , Triexosilceramidas/farmacologiaRESUMO
The pentasaccharide glycoside corresponding to galactosylgloboside (SSEA-3), beta-D-Gal p-(1-->3)-beta-D-Gal pNAc-(1-->3)-alpha-D-Gal p-(1-->4)-beta-D-Gal p-(1-->4)-beta-D-Glc p-1-OCH2CH2Si-(CH3)3 (4), was synthesized via glycosylation (87%) of 2-(trimethylsilyl)ethyl 2,3,6-tri-O-benzyl-4-O-[2,3,6-tri-O-benzyl-4-O-(2,4, 6-tri-O-benzyl-alpha-D-galactopyranosyl)-beta-D-galactopyranosyl]-beta-D - glucopyranoside (2) with the glycosyl donor methyl 4,6-di-O-acetyl-2-deoxy-2-phthalimido-3-O-(2,3,4, 6-tetra-O-acetyl-beta-D-galactopyranosyl)-1-thio-beta-D-galactopyranosid e (1), followed by removal of protecting groups. Compound 4 was transformed into the spacer glycoside beta-D-Gal p(1-->3)-beta-D-Gal pNAc-(1-->3)-alpha-D-Gal p-(1-->4)-beta-D-Gal p-(1-->4)-beta-D-Glc p-1-SCH2CH2COOH (10), which was coupled to bovine serum albumin (BSA), and Sepharose beads, to give the corresponding neoglycoprotein (11, 6 mol of saccharide/mol of BSA), and glycosylated Sepharose (12, 2.7 mumol of saccharide/mL of sedimented beads), respectively. An improved synthesis of a protected globotetraoside beta-D-Gal pNAc-(1-->3)-alpha-D-Gal p-(1-->4)-beta-D-Gal p-(1-->4)-beta-D-Glc p-1-OCH2CH2SiMe3 is also reported.