We have previously demonstrated that annexin IV, one of the calcium/phospholipid-binding annexin family proteins, binds to glycosaminoglycans (GAGs) in a calcium-dependent manner (Kojima, K., Yamamoto, K., Irimura, T., Osawa, T., Ogawa, H., and Matsumoto, I. (1996) J. Biol. Chem. 271, 7679 -7685). In this study, we investigated the GAG binding specificities of annexins IV, V, and VI by affinity chromatography and solid phase assays. Annexin IV was found to bind in a calcium-dependent manner to all the GAG columns tested. Annexin V bound to heparin and heparan sulfate columns but not to chondroitin sulfate columns. Annexin VI was adsorbed to heparin and heparan sulfate columns in a calcium-independent manner, and to chondroitin sulfate columns in a calcium-dependent manner. An N-terminal half fragment (A6NH) and a C-terminal half fragment (A6CH) of annexin VI, each containing four units, were prepared by digestion with V8 protease and examined for GAG binding activities. A6NH bound to heparin in the presence of calcium but not to chondroitin sulfate C, whereas A6CH bound to heparin calcium-independently and to chondroitin sulfate C calcium-dependently. The results showed that annexin IV, V, and VI have different GAG binding properties. Some annexins have been reported to be detected not only in the cytoplasm but also on the cell surface or in extracellular components. The findings suggest that the some annexins function as recognition elements for GAGs in extracellular space.

The structural requirements for the interaction of asparagine-linked oligosaccharide moieties of glycoproteins with wheat germ agglutinin (WGA) were investigated by using affinity chromatography on a WGA-Sepharose column. So-called hybrid-type glycopeptides obtained from ovalbumin [Yamashita, K., Tachibana, Y., & Kobata, A. (1978) J. Biol. Chem. 253, 3862--3869] were found to have high affinity for WGA--Sepharose, whereas high mannose-type and complex-type glycopeptides were shown to have low affinity. The elution profiles of various glycopeptides modified by glycosidase treatment, Smith periodate degradation, acetolysis, and hydrazinolysis showed that the GlcNAcbeta 1--4Manbeta 1--4GlcNAc beta 1--4GlcNAc-Asn structure was essential for the binding of glycopeptides to a WGA-Sepharose column. Thus, it was revealed that both the N,N'-diacetylchitobiose moiety and the beta-N-acetylglucosaminyl residue linked to C-4 of the beta-linked mannose residue contributed to the interaction of the glycopeptide with WGA-Sepharose. The substitution at C-6 of the innermost beta-N-acetylglucosaminyl residue by an alpha-fucosyl residue or at C-6 of the beta-linked mannose residue by another mannose residue in the above structure reduced the affinity of glycopeptides for the column.

T cell progenitors in the adult thymus (AT) are not well characterized. In the present study, we show that the earliest progenitors in the murine AT are, like those in fetal thymus (FT), unable to generate B or myeloid cells, but still retain the ability to generate NK cells and dendritic cells. However, AT progenitors are distinct from those in FT or fetal liver, in that they are able to produce ∼100 times larger numbers of T cells than progenitors in fetuses. Such a capability to generate a large number of T cells was mainly attributed to their potential to extensively proliferate before the TCRβ chain gene rearrangement. We propose that the AT is colonized by T/NK/dendritic cell tripotential progenitors with much higher potential to form diversity in TCRβ chains than FT progenitors.

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