Tatsushi Toyokuni

A role of carbohydrate-carbohydrate interaction in the process of specific cell recognition during embryogenesis and organogenesis: a preliminary note

A possible role of cell surface glycoconjugates in cell recognition has been envisioned based on recognition of carbohydrates by cell surface proteins such as endogenous lectins, glycosyltransferases, and hydrolases (refs. 18-22 in text). A new possibility that a specific carbohydrate at the cell surface could be recognized by the same or similar carbohydrate on the counterpart cell surface is now suggested by specific interaction between Lex and Lex, but not between Lex and sialylated or non-substituted type 2 chain. A new hypothesis is hereby proposed for carbohydrate-carbohydrate interactions as recognition signals during embryogenesis and organogenesis.

Synthetic vaccines: I. Synthesis of multivalent Tn antigen cluster-lysyllysine conjugates☆

Monomer, dimer, and trimer of Tn antigen (GalNAcα1→O-Ser) were coupled to L-lysyllysine to construct multivalent and clustering structures of Tn antigen. The method has made it possible to provide pertinent carbohydrate antigens for the development of synthetic vaccines against tumors.

Synthesis of multivalent β-lactosyl clusters as potential tumor metastasis inhibitors

A beta-lactosyl residue was linked to the amino groups of L-lysyl-L-lysine through spacer arms of three different lengths (C2, C4, and C9) to give trivalent beta-lactosyl clusters in order to increase the inhibitory activity of the beta-lactosyl group against tumor cell colonization. Thus, O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-(1-->4)-2,3, 6-tri-O-acetyl-glucopyranosyl trichloroacetimidate was treated with methyl or benzyl hydroxyethanoate, methyl or benzyl 4-hydroxybutanoate, and methyl 9-hydroxynonanoate, respectively, in the presence of trimethylsilyl trifluoromethanesulfonate to give the corresponding beta-lactosides. These were coupled to L-lysyl-L-lysine, after conversion to the N-hydroxysuccinimide esters, to yield the corresponding trivalent beta-lactosyl-L-lysyl-L-lysine conjugates in good yields. The beta-lactosyl group with a C4 spacer arm was also coupled similarly to poly(L-lysine) (M(r) 3800) to form a polyvalent beta-lactosyl cluster. Coinjection of the trivalent (with C2 and C4 spacer arms) and polyvalent beta-lactosyl clusters with the highly metastatic B16 murine melanoma cells inhibited the formation of lung colonies in C57/BL mice, whereas the trivalent cluster with a C9 spacer arm displayed no activity.

Solid-phase synthesis and immunoreactivity of penta-O-(N-acetyl-α-D-galactosaminyl)-MUC1 eicosapeptide, a glycosylated counter part of the highly immunogenic tandem repeat sequence of carcinoma-associated mucin

Abstract Penta- O -glycosylated MUC1 peptide HVal-Thr * -Ser * -Ala-Pro-Asp-Thr * -Arg-Pro-Ala-Pro-Gly-Ser * -Thr * -Ala-Pro-Pro-Ala-His-Gly-OH ( * α- D -GalNA cp ) ( 2 ) has been synthesized by a solid-phase method on Sasrin resin using Fmoc-glycoaminoacids 3 and 4 as building blocks. The monoclonal antibodies SM3 and HMPV, specific to the MUC1 peptide 1 , also react strongly with 2 .

Synthesis of trifluoromethyl analogue of L-fucose and 6-deoxy-D-altrose

Trifluoromethylation of the acyclic derivative of D-lyxose, 3, with trifluoromethyltrimethylsilane in the presence of tetrabutylammonium fluoride yielded a mixture of trifluoromethyl adducts, 5a and b, which was converted to 6,6,6-trifluoro-L-fucose 9a and 6-deoxy-6,6,6-trifluoro-D-altrose 9bvia selective oxidation of the primary hydroxy group involving treatment of the trimethylsiloxy derivatives, 7a and b, with Collins reagent.

Use of fumonisin B1 to test the intercellular transfer of sphingosine

Sphingosine, a core unit of sphingolipids, has been shown to mediate intracellular signaling events. It is conceivable that sphingosine could act as an intracellular messenger as well as an intracellular modulator, if sphingosine were to be transferred intercellularly. Murine interleukin-2 (IL-2) dependent T-lymphocyte CTLL cells, murine fibroblasts Swiss 3R3 cells, and murine fibroblast BALB/C A31 cells metabolize exogenously added sphingosine to ceramide. Fumonisin B2, a mycotoxin produced by Fusarium moniliforme, blocks the conversion of sphingosine to ceramide. In the study described here, CTLL cells exhibiting the conversion of sphingosine to ceramide were used as recipient cells, whereas fumonisin B1-treated cells (A31 cells, Swiss 3T3 cells and CTLL cells), in which the conversion was blocked were used as donor cells. To demonstrate intercellular transfer of sphingosine through the conversion pathway of sphingosine to ceramide, fumonisin B1-treated donor cells incorporating radioactive sphingosine were co-incubated with CTLL cells and the ceramide response was examined. These experiments demonstrated that it is possible to prove the intercellular transfer of sphingosine by using different activities in the cellular conversion pathway of sphingosine to ceramide.