Involvement of tyrosines at fucose-binding sites of Aleuria aurantia lectin: non-equal response to site-directed mutagenesis among five sites

Since the involvement of Tyr residues in the fucose-binding of Aleuria aurantia lectin (AAL) was proved by chemical modification using the Tyr-specific reagent tetranitromethane, site-directed mutagenesis was attempted. Since the tertiary structure of AAL was determined recently to be a six-bladed beta-propeller fold, and five fucose-binding sites per subunit were found, based on positions of Tyr residues in the tertiary structure, three classes of mutants were constructed: 1) Tyr on the 2nd beta-strand of each blade (beta-2 mutants), 2) Tyr or Trp on the 3rd beta-strand (beta-3 mutants), and 3) Tyr outside of binding sites (other-Y mutants). The mutagenized cDNA was expressed in Escherichia coli as His-tag-AAL, and the hemagglutinating activity was assayed. Among 14 mutants, three beta-2 mutants (Y26A, Y79A, and Y181A), and three beta-3 mutants (Y92A, W149A, and Y241A) showed decreased activity. These mutated residues resided at Sites 1, 2, and 4, at the same locations relatively in the binding sites. Mutagenesis of Tyr or Trp at the corresponding locations in Sites 3 and 5 did not lead to a reduction in activity. Results indicate that the properties of Sites 1, 2, and 4 are different from those of Sites 3 and 5, and that the contribution of these two sites to the hemagglutination reaction was minor.     

Tie2/angiopoietin-1 signaling regulates hematopoietic stem cell quiescence in the bone marrow niche

The quiescent state is thought to be an indispensable property for the maintenance of hematopoietic stem cells (HSCs). Interaction of HSCs with their particular microenvironments, known as the stem cell niches, is critical for adult hematopoiesis in the bone marrow (BM). Here, we demonstrate that HSCs expressing the receptor tyrosine kinase Tie2 are quiescent and antiapoptotic, and comprise a side-population (SP) of HSCs, which adhere to osteoblasts (OBs) in the BM niche. The interaction of Tie2 with its ligand Angiopoietin-1 (Ang-1) induced cobblestone formation of HSCs in vitro and maintained in vivo long-term repopulating activity of HSCs. Furthermore, Ang-1 enhanced the ability of HSCs to become quiescent and induced adhesion to bone, resulting in protection of the HSC compartment from myelosuppressive stress. These data suggest that the Tie2/Ang-1 signaling pathway plays a critical role in the maintenance of HSCs in a quiescent state in the BM niche.     

Comparison of competitive ability between native and introduced salmonids: evidence from pairwise contests

Brown trout, Salmo trutta, and rainbow trout, Oncorhynchus mykiss, have been introduced to freshwaters in Hokkaido, Japan. Today, it is recognized that these introduced salmonids have negative impacts on native salmonids such as white-spotted charr, Salvelinus leucomaenis, and masu salmon, O. masou. In particular, interspecific competition may be an important mechanism that could contribute to the exclusion for native salmonids. In this study, experimental pairwise contests were conducted to compare interference competitive ability between native and introduced salmonids. We demonstrated that brown trout were competitively superior to white-spotted charr and masu salmon whereas rainbow trout were superior to white-spotted charr. We suggest that introduced brown trout negatively impact both white-spotted charr and masu salmon, and introduced rainbow trout negatively impact white-spotted charr.     

Distribution of lichen flora on South Korea

After an overview on the temporary situation of the lichenology in South Korea, localities of 95 macrolichen taxa are reported for South Korea. In this revised lichen flora of South Korea, 16 species are apparently new to the territory. Voucher specimens have been deposited in the Korean Lichen Research Institute (KoLRI) at Sunchon National University in Korea, and duplicates have also been donated to the National History Museum and Institute, in Chiba, (CBM) Japan.     

Induction of IL-10-producing CD4+CD25+ T cells in animal model of collagen-induced arthritis by oral administration of type II collagen

Induction of oral tolerance has long been considered a promising approach to the treatment of chronic autoimmune diseases, including rheumatoid arthritis (RA). Oral administration of type II collagen (CII) has been proven to improve signs and symptoms in RA patients without troublesome toxicity. To investigate the mechanism of immune suppression mediated by orally administered antigen, we examined changes in serum IgG subtypes and T-cell proliferative responses to CII, and generation of IL-10-producing CD4+CD25+ T-cell subsets in an animal model of collagen-induced arthritis (CIA). We found that joint inflammation in CIA mice peaked at 5 weeks after primary immunization with CII, which was significantly less in mice tolerized by repeated oral feeding of CII before CIA induction. Mice that had been fed with CII also exhibited increased serum IgG1 and decreased serum IgG2a as compared with nontolerized CIA animals. The T-cell proliferative response to CII was suppressed in lymph nodes of tolerized mice also. Production of IL-10 and of transforming growth factor-beta from mononuclear lymphocytes was increased in the tolerized animals, and CD4+ T cells isolated from tolerized mice did not respond with induction of IFN-gamma when stimulated in vitro with CII. We also observed greater induction of IL-10-producing CD4+CD25+ subsets among CII-stimulated splenic T cells from tolerized mice. These data suggest that when these IL-10-producing CD4+CD25+ T cells encounter CII antigen in affected joints they become activated to exert an anti-inflammatory effect.     

C(8)-substituted 1-azabicyclo[3.3.1]non-3-enes: a novel scaffold for muscarinic receptor ligands

The [3.3.1]-bicyclic amine, exo-8-benzyloxymethyl-3-ethoxycarbonyl-4-hydroxy-1-azabicyclo[3.3.1]non-3-ene (1), has been shown to be a potent competitive antagonist against the hM(1)-hM(5) muscarinic receptors. This heterocyclic system has not been extensively evaluated despite the notable activities reported for other bicyclic amines. Synthetic strategies permitted the selective alteration of five structural sites in 1. Pharmacological evaluation demonstrated that modification of either the C(3) alkoxycarbonyl or the C(4) enol units in 1 gave compounds with high affinity for the hM(1)-hM(5) muscarinic receptors with selectivity for the hM(2) receptor.