Embryonic stem (ES) cells are pluripotent-undifferentiated cells that have a great interest for the investigation of developmental biology. Murine ES cells maintain their pluripotency by the supplementation of the leukemia inhibitory factor (LIF). LIF is reported to act as a matrix-anchored form, and immobilized cytokines are useful to sustain their signaling on target cells. In this study, we used the immobilizable fusion protein composed of LIF and IgG-Fc region, which was used as a model of the matrix-anchored form of LIF to establish a novel system for ES cell culture and to investigate the effect of immobilized LIF on maintenance of ES cell pluripotency. Mouse ES cells maintained their undifferentiated state on the surface coated with LIF-Fc. Furthermore, when cultured on the co-immobilized surface with LIF-Fc and E-cadherin-Fc, mouse ES cells showed characteristic scattering morphologies without colony formation, and they could maintain their undifferentiated state and pluripotency without additional LIF supplementation. The activation of LIF signaling was sustained on the co-immobilized surface. These results indicate that immobilized LIF and E-cadherin can maintain mouse ES cells efficiently and that the immobilizable LIF-Fc fusion protein is useful for the investigation of signaling pathways of an immobilized form of LIF in the maintenance of ES cell pluripotency. ES3 cells are pluripotent-undifferentiated cells derived from the inner cell mass of a blastocyst, and they retain the potentiality of multilineage differentiation in vitro and self-renewal activity (1, 2). For the maintenance of pluripotency, mouse ES cells are cultured on a feeder layer of mouse embryonic fibroblasts (MEF) or incubated with LIF that is produced by MEF.LIF is a pleiotropic cytokine, which induces the differentiation of leukemia cell lines into macrophages (3) and the expression of acute phase proteins in hepatocytes (4), as well as inhibits proliferation of endothelial cells (5).Several studies suggest that the biological signals of growth factors and cytokines are mediated by two different forms, the secreted form and the cell membrane-or matrix-anchored forms, which stimulate different signal transduction cascades (6 -8). It is reported that the LIF signal is mediated by either a soluble form or by a form bound to extracellular matrices, both of which induce different effects on cells (9, 10).Recently, we reported the application of immobilizable fusion proteins for the analysis of cell function, and we also reported the establishment of a culture system for stem cells (11-13). When cells were cultured on the fusion protein of E-cadherin and IgG Fc domain (E-cad-Fc), they showed scattering behavior and high proliferative ability (11). We also reported the novel method of immobilizing epidermal growth factor as a juxtacrine model, and we applied this system to the analysis of the function of immobilized epidermal growth factor on hepatocytes (13).In this study, we focused on the effect of the immobilized form of LIF on the m...

Hitherto three variant forms of ABCG2 have been documented on the basis of their amino acid moieties (i.e., Arg, Gly, and Thr) at the position 482. In the present study, we have generated those variants of ABCG2 by site-directed mutagenesis and expressed them in Sf9 insect cells. The apparent molecular weight of the expressed ABCG2 variants was 130,000 under non-reductive conditions, whereas it was reduced to 65, 000 by treatment with mercaptoethanol. It is suggested that ABCG2 exists in the plasma membrane of Sf9 cells as a homodimer bound through cysteinyl disulfide bond(s). Both ATPase activity and drug transport of ABCG2 variants were examined by using plasma membrane fractions prepared from ABCG2-overexpressing Sf9 cells. The ATPase activity of the plasma membrane expressing ABCG2 (Gly-482) was significantly enhanced by prazosin. In contrast, ABCG2 (Arg-482) transports [(3)H]methotrexate in an ATP-dependent manner; however, no transport activity was observed with the other variants (Gly-482 and Thr-482). It is strongly suggested that the amino acid moiety at the position of 482 is critical for the substrate specificity of ABCG2.

ABSTRACT. We cloned five new subtypes of cDNA encoding canine interferon-α (CaIFN-α) from a canine epithelial cell line. CaIFN-αs were divided into two groups by amino acid sequences and a molecular phylogenic tree. Two subtypes of them were expressed in Escherichia coli, and IFN proteins were purified. Recombinant CaIFN-αs were highly species-specific and showed antiviral activity against Vesicular stomatitis New Jersey virus and canine adenovirus-1 , but not against canine herpesvirus-1.