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81.
Carruthers MD Tracy EN Dickson AC Ganser KB Munson RS Bakaletz LO 《Journal of bacteriology》2012,194(8):1927-1933
We previously demonstrated that one or more products of the genes in the pil and com gene clusters of the opportunistic human respiratory pathogen nontypeable Haemophilus influenzae (NTHI) are required for type IV pilus (Tfp) biogenesis and function. Here, we have now demonstrated that the pilABCD and comABCDEF gene clusters are operons and that the product of each gene is essential for normal pilus function. Mutants with nonpolar deletions in each of the 10 pil and com genes had an adherence defect when primary human airway cells were used as the target. These mutants were also diminished in their ability to form a biofilm in vitro and, additionally, were deficient in natural transformation. Collectively, our data demonstrate that the product of each gene within these operons is required for the normal biogenesis and/or function of NTHI Tfp. Based on the similarity of PilA to other type IV pilins, we further predicted that the product of the pilA gene would be the major pilin subunit. Toward that end, we also demonstrated by immunogold labeling and mass spectrometry that PilA is indeed the majority type IV pilin protein expressed by NTHI. These new observations set the stage for experiments designed to dissect the function of each of the proteins encoded by genes within the pil and com gene clusters. The ability to characterize individual proteins with vital roles in NTHI colonization or pathogenesis has the potential to reduce the burden of NTHI-induced diseases through development of a Tfp-derived vaccine or a pilus-directed therapeutic. 相似文献
82.
Logan Fletcher Peter Carruthers 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2012,367(1594):1366-1378
This article considers the cognitive architecture of human meta-reasoning: that is, metacognition concerning one''s own reasoning and decision-making. The view we defend is that meta-reasoning is a cobbled-together skill comprising diverse self-management strategies acquired through individual and cultural learning. These approximate the monitoring-and-control functions of a postulated adaptive system for metacognition by recruiting mechanisms that were designed for quite other purposes. 相似文献
83.
At any instant, the human erythrocyte sugar transporter presents at least one sugar export site but multiple sugar import sites. The present study asks whether the transporter also presents more than one sugar exit site. We approached this question by analysis of binding of [3H]cytochalasin B (an export conformer ligand) to the human erythrocyte sugar transporter and by analysis of cytochalasin B modulation of human red blood cell sugar uptake. Phloretin-inhibitable cytochalasin B binding to human red blood cells, to human red blood cell integral membrane proteins, and to purified human red blood cell glucose transport protein (GluT1) displays positive cooperativity at very low cytochalasin B levels. Cooperativity between sites and K(d(app)) for cytochalasin B binding are reduced in the presence of intracellular ATP. Red cell sugar uptake at subsaturating sugar levels is inhibited by high concentrations of cytochalasin B but is stimulated by lower (<20 nM) concentrations. Increasing concentrations of the e1 ligand forskolin also first stimulate then inhibit sugar uptake. Cytochalasin D (a cytochalasin B analogue that does not interact with GluT1) is without effect on sugar transport over the same concentration range. Cytochalasin B and ATP binding are synergistic. ATP (but not AMP) enhances [3H]cytochalasin B photoincorporation into GluT1 while cytochalasin B (but not cytochalasin D) enhances [gamma-32P]azidoATP photoincorporation into GluT1. We propose that the red blood cell glucose transporter is a cooperative tetramer of GluT1 proteins in which each protein presents a translocation pathway that alternates between uptake (e2) and export (e1) states but where, at any instant, two subunits must present uptake (e2) and two subunits must present exit (e1) states. 相似文献
84.
A Carruthers 《Trends in biochemical sciences》1988,13(11):426-428
85.
Richard L. Bennett Aubrey L. Carruthers Teng Hui Krystal R. Kerney Xiangfei Liu W. Stratford May Jr 《PloS one》2012,7(9)
It has been reported that the expression and activity of the interferon-inducible, dsRNA-dependent protein kinase, PKR, is increased in mammary carcinoma cell lines and primary tumor samples. To extend these findings and determine how PKR signaling may affect breast cancer cell sensitivity to chemotherapy, we measured PKR expression by immunohistochemical staining of 538 cases of primary breast cancer and normal tissues. Significantly, PKR expression was elevated in ductal, lobular and squamous cell carcinomas or lymph node metastases but not in either benign tumor specimens or cases of inflammation compared to normal tissues. Furthermore, PKR expression was increased in precancerous stages of mammary cell hyperplasia and dysplasia compared to normal tissues, indicating that PKR expression may be upregulated by the process of tumorigenesis. To test the function of PKR in breast cancer, we generated MCF7, T-47D and MDA-MB-231 breast cancer cell lines with significantly reduced PKR expression by siRNA knockdown. Importantly, while knockdown of PKR expression had no effect on cell proliferation under normal growth conditions, MCF7, T-47D or MDA-MB-231 cells with reduced PKR expression or treated with a small molecule PKR inhibitor were significantly less sensitive to doxorubicin or H2O2-induced toxicity compared to control cells. In addition, the rate of eIF2α phosphorylation following treatment with doxorubicin was delayed in breast cancer cell lines with decreased PKR expression. Significantly, treatment of breast cancer lines with reduced PKR expression with either interferon-α, which increases PKR expression, or salubrinal, which increases eIF2α phosphorylation, restored doxorubicin sensitivity to normal levels. Taken together these results indicate that increased PKR expression in primary breast cancer tissues may serve as a biomarker for response to doxorubicin-containing chemotherapy and that future therapeutic approaches to promote PKR expression/activation and eIF2α phosphorylation may be beneficial for the treatment of breast cancer. 相似文献
86.
Robert A. Jones Dennis M. Burns Daryl J. Carruthers Ifor R. Beacham 《FEMS microbiology letters》1993,114(3):299-3047
Abstract Most isolates of Salmonella contain two unrelated UDP-sugar hydrolases, one of which, encoded by the ushB gene, is inner membrane-associated. Previous studies showed that this enzyme contains a typical N-terminal signal peptide; the evidence also indicated, however, that this peptide is not cleaved, and serves to anchor the UshB protein in the inner membrane. In this report, we present strong evidence that this is indeed the case by using ushB'-'blaM fusions to demonstrate that this signal peptide is capable of localising β-lactamase to the inner membrane. We also present evidence that UshB is located on the exterior (periplasmic) side of the membrane, and hence has an 'N-terminus inside/C-terminus outside' membrane orientation, consistent with a role in the degradation of external substrates. 相似文献
87.
Jill A. Jablonowski Kiev S. Ly Michael Bogenstaetter Curt A. Dvorak Jamin D. Boggs Lisa K. Dvorak Brian Lord Kirsten L. Miller Curt Mazur Sandy J. Wilson Timothy W. Lovenberg Nicholas I. Carruthers 《Bioorganic & medicinal chemistry letters》2009,19(3):903-907
A novel series of imidazole containing histamine H3 receptor ligands were investigated and found to be potent functional antagonists. After improving the stability of these molecules towards liver microsomes, these compounds were found to have no appreciable affinity for CYP P450s. Subsequent in vivo experiments showed significant brain uptake of (4-chloro-phenyl)-[2-(1-isopropyl-piperidin-4-ylmethoxy)-3-methyl-3H-imidazol-4-yl]-methanone 22. 相似文献
88.
89.
90.
Olivia L. McGovern Yolanda Rivera‐Cuevas Geetha Kannan Andrew J. Narwold Jr Vern B. Carruthers 《Traffic (Copenhagen, Denmark)》2018,19(5):336-353
Host cytosolic proteins are endocytosed by Toxoplasma gondii and degraded in its lysosome‐like compartment, the vacuolar compartment (VAC), but the dynamics and route of endocytic trafficking remain undefined. Conserved endocytic components and plant‐like features suggest T. gondii endocytic trafficking involves transit through early and late endosome‐like compartments (ELCs) and potentially the trans‐Golgi network (TGN) as in plants. However, exocytic trafficking to regulated secretory organelles, micronemes and rhoptries, also proceeds through ELCs and requires classical endocytic components, including a dynamin‐related protein, DrpB. Here, we show that host cytosolic proteins are endocytosed within 7 minutes post‐invasion, trafficked through ELCs en route to the VAC, and degraded within 30 minutes. We could not definitively interpret if ingested protein is trafficked through the TGN. We also found that parasites ingest material from the host cytosol throughout the parasite cell cycle. Ingested host proteins colocalize with immature microneme proteins, proM2AP and proMIC5, in transit to the micronemes, but not with the immature rhoptry protein proRON4, indicating that endocytic trafficking of ingested protein intersects with exocytic trafficking of microneme proteins. Finally, we show that conditional expression of a DrpB dominant negative mutant increases T. gondii ingestion of host‐derived proteins, suggesting that DrpB is not required for parasite endocytosis. 相似文献