Fatty acid ethyl esters in the liverwort Conocephalum conicum

A series of fatty acid ethyl esters ranging from C₁₄ to C₂₄ was isolated from a hexane extract of the liverwort Conocephalum conicum, these esters accounted for 77% of the extract. The ethyl esters consisting of even-numbered fatty acids were predominant and ethyl palmitate was the major constituent.     

The Electrophoretical Analysis of Esterase and Catalase and Its Use in Taxonomical Studies of Mycobacteria

The zymogram patterns of esterases and catalases of mycobacterial strains were studied using the thin layer agar electrophoresis. Though there were some variations, Mycobacterium hominis, M. bovis, M. kansasii, M. fortuitum, M. runyonii, M. avium, M. phlei and M. smegmatis seemed to show species-specific patterns consisting of 2 to 6 esterase bands and one or more catalase bands. The patterns of scotochromogens and nonchromogens were rather variable.     

Partial silencing of fucosyltransferase 8 gene expression inhibits proliferation of Ishikawa cells,a cell line of endometrial cancer

Endometrial cancer is the most common gynecologic malignancy and is associated with increased morbidity each year, including young people. However, its mechanisms of proliferation and progression are not fully elucidated. It is well known that abnormal glycosylation is involved in oncogenesis, and fucosylation is one of the most important types of glycosylation. In particular, fucosyltransferase 8 (FUT8) is the only FUT responsible for α1, 6-linked fucosylation (core fucosylation), and it is involved in various physiological as well as pathophysiological processes, including cancer biology. Therefore, we aimed to identify the expression of FUT8 in endometrial endometrioid carcinoma and investigate the effect of the partial silencing of the FUT8 gene on the cell proliferation of Ishikawa cells, an epithelial-like endometrial cancer cell line. Quantitative real-time PCR analysis showed that FUT8 gene expression was significantly elevated in the endometrial endometrioid carcinoma, compared to the normal endometrium. The immunostaining of FUT8 and Ulex europaeus Agglutinin 1 (UEA-1), a kind of lectin family specifically binding to fucose, was detected endometrial endometrioid carcinoma. The proliferation assay showed FUT8 partial knockdown by transfection of siRNA significantly suppressed the proliferation of Ishikawa cells, concomitant with the upregulation in the gene expressions associated with the interesting pathways associated with de-ubiquitination, aspirin trigger, mesenchymal-epithelial transition (MET) et al. It was suggested that the core fucosylation brought about by FUT8 might be involved in the proliferation of endometrial endometrioid carcinoma cells.     

The tyrosine kinase v-Src modifies cytotoxicities of anticancer drugs targeting cell division

v-Src oncogene causes cell transformation through its strong tyrosine kinase activity. We have revealed that v-Src-mediated cell transformation occurs at a low frequency and it is attributed to mitotic abnormalities-mediated chromosome instability. v-Src directly phosphorylates Tyr-15 of cyclin-dependent kinase 1 (CDK1), thereby causing mitotic slippage and reduction in Eg5 inhibitor cytotoxicity. However, it is not clear whether v-Src modifies cytotoxicities of the other anticancer drugs targeting cell division. In this study, we found that v-Src restores cancer cell viability reduced by various microtubule-targeting agents (MTAs), although v-Src does not alter cytotoxicity of DNA-damaging anticancer drugs. v-Src causes mitotic slippage of MTAs-treated cells, consequently generating proliferating tetraploid cells. We further demonstrate that v-Src also restores cell viability reduced by a polo-like kinase 1 (PLK1) inhibitor. Interestingly, treatment with Aurora kinase inhibitor strongly induces cell death when cells express v-Src. These results suggest that the v-Src modifies cytotoxicities of anticancer drugs targeting cell division. Highly activated Src-induced resistance to MTAs through mitotic slippage might have a risk to enhance the malignancy of cancer cells through the increase in chromosome instability upon chemotherapy using MTAs.     

Cooperation of the IFT-A complex with the IFT-B complex is required for ciliary retrograde protein trafficking and GPCR import

Cilia sense and transduce extracellular signals via specific receptors. The intraflagellar transport (IFT) machinery mediates not only bidirectional protein trafficking within cilia but also the import/export of ciliary proteins across the ciliary gate. The IFT machinery is known to comprise two multisubunit complexes, namely, IFT-A and IFT-B; however, little is known about how the two complexes cooperate to mediate ciliary protein trafficking. We here show that IFT144–IFT122 from IFT-A and IFT88–IFT52 from IFT-B make major contributions to the interface between the two complexes. Exogenous expression of the IFT88(Δα) mutant, which has decreased binding to IFT-A, partially restores the ciliogenesis defect of IFT88-knockout (KO) cells. However, IFT88(Δα)-expressing IFT88-KO cells demonstrate a defect in IFT-A entry into cilia, aberrant accumulation of IFT-B proteins at the bulged ciliary tips, and impaired import of ciliary G protein–coupled receptors (GPCRs). Furthermore, overaccumulated IFT proteins at the bulged tips appeared to be released as extracellular vesicles. These phenotypes of IFT88(Δα)-expressing IFT88-KO cells resembled those of IFT144-KO cells. These observations together indicate that the IFT-A complex cooperates with the IFT-B complex to mediate the ciliary entry of GPCRs as well as retrograde trafficking of the IFT machinery from the ciliary tip.     

Structural requirement of C‐terminal region of chicken lysozyme signal peptide

Abstract

The mechanisms of signal peptide cleavage has not been fully elucidated yet. In previous investigation, we have examined the effect of chicken lysozyme signal peptide mutations on the secretion of human lysozyme. During this study, we determined that the hydrophobic bulky amino acid Val at position ‐1 inhibited the function of signal peptide. To determine why the ‐1Val suppressed the function of signal peptide, turn‐promoting amino acids Pro and Gly were introduced after ‐lVal to prevent the signal peptide from forming α‐helix and induce β‐turn around the cleavage site. This mutation resulted in no processing of signal peptide and no secretion of human lysozyme. However, the replacement of ‐1Val with Ala permitted a functional signal. Based on these results, three dimensional models around the cleavage site of each signal peptide were made, which show that bulky side chain at ‐1 residue of signal peptide limits the reaction space for signal peptidase and suppresses cleavage by steric hindrance. We suggest that the bulky side chain at ‐1 residue suppresses the signal peptide cleavage by its local steric hindrance and not by a change in whole structure around the cleavage site. On the other hand, introduction of Pro at position +1 did not inhibit signal cleavage completely resulting in poor secretion and processing efficiency although Pro in position +1 has been recently reported to block cleavage of the prokaryotic signal peptide. The mechanism of cleavage of prokaryotic signal may be different than that of eukaryotic signal.