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101.
Unique pattern of convergent envelope evolution in simian immunodeficiency virus-infected rapid progressor macaques: association with CD4-independent usage of CCR5 下载免费PDF全文
The rate of disease development in simian immunodeficiency virus (SIV) infection of macaques varies considerably among individual macaques. While the majority of macaques inoculated with pathogenic SIV develop AIDS within a period of 1 to 2 years, a minority exhibit a rapid disease course characterized by absence or transience of humoral and cellular immune responses and high levels of virus replication with widespread dissemination of SIV in macrophages and multinucleated giant cells. The goal of this study was to examine viral evolution in three SIVsmE543-3-inoculated rapid progressors to determine the contribution of viral evolution to the development of rapid disease and the effect of the absence of immune pressure upon viral evolution. PCR was used to amplify and clone the entire SIV genome from tissues collected at necropsy, and the course of viral evolution was assessed by env sequences cloned from sequential plasma samples of one rapid progressor (RP) macaque. The majority of sequence changes in RP macaques occurred in the envelope gene. Substitutions were observed in all three animals at specific conserved residues in envelope, including loss of a glycosylation site in V1/V2, a D-to-N/V substitution in a highly conserved GDPE motif, and a P-to-V/H/T substitution in the V3 loop analog. A cell-cell fusion assay revealed that representative env clones utilized CCR5 as a coreceptor, independent of CD4. The selection of specific substitutions in envelope in RP macaques suggests novel selection pressures on virus in such animals and suggests that viral variants that evolve in these animals may play a role in disease progression. 相似文献
102.
Gimeno RE Hirsch DJ Punreddy S Sun Y Ortegon AM Wu H Daniels T Stricker-Krongrad A Lodish HF Stahl A 《The Journal of biological chemistry》2003,278(49):49512-49516
Fatty acid transport protein-4 (FATP4) is the major FATP in the small intestine. We previously demonstrated, using in vitro antisense experiments, that FATP4 is required for fatty acid uptake into intestinal epithelial cells. To further examine the physiological role of FATP4, mice carrying a targeted deletion of FATP4 were generated. Deletion of one allele of FATP4 resulted in 48% reduction of FATP4 protein levels and a 40% reduction of fatty acid uptake by isolated enterocytes. However, loss of one FATP4 allele did not cause any detectable effects on fat absorption on either a normal or a high fat diet. Deletion of both FATP4 alleles resulted in embryonic lethality as crosses between heterozygous FATP4 parents resulted in no homozygous offspring; furthermore, no homozygous embryos were detected as early as day 9.5 of gestation. Early embryonic lethality has been observed with deletion of other genes involved in lipid absorption in the small intestine, namely microsomal triglyceride transfer protein and apolipoprotein B, and has been attributed to a requirement for fat absorption early in embryonic development across the visceral endoderm. In mice, the extraembryonic endoderm supplies nutrients to the embryo prior to development of a chorioallantoic placenta. In wild-type mice we found that FATP4 protein is highly expressed by the epithelial cells of the visceral endoderm and localized to the brush-border membrane of extraembryonic endodermal cells. This localization is consistent with a role for FATP4 in fat absorption in early embryogenesis and suggests a novel requirement for FATP4 function during development. 相似文献
103.
Presynaptic kainate receptors that enhance the release of GABA on CA1 hippocampal interneurons 总被引:9,自引:0,他引:9
We report that kainate receptors are present on presynaptic GABAergic terminals contacting interneurons and that their activation increases GABA release. Application of kainate increased the frequency of miniature inhibitory postsynaptic currents recorded in CA1 interneurons. Local applications of glutamate but not of AMPA or NMDA also increased GABA quantal release. Application of kainate as well as synaptically released glutamate reduced the number of failures of GABAergic neurotransmission between interneurons. Thus, activation of presynaptic kainate receptors increases the probability of GABA release at interneuron-interneuron synapses. Glutamate may selectively control the communication between interneurons by increasing their mutual inhibition. 相似文献
104.
A competitive PCR (cPCR) assay was developed to quantify the nematophagous fungus Verticillium chlamydosporium in soil. A gamma-irradiated soil was seeded with different numbers of chlamydospores from V. chlamydosporium isolate 10, and samples were obtained at time intervals of up to 8 weeks. Samples were analyzed by cPCR and by plating onto a semiselective medium. The results suggested that saprophytic V. chlamydosporium growth did occur in soil and that the two methods detected different phases of growth. The first stage of growth, DNA replication, was demonstrated by the rapid increase in cPCR estimates, and the presumed carrying capacity (PCC) of the soil was reached after only 1 week of incubation. The second stage, an increase in fungal propagules presumably due to cell division, sporulation, and hyphal fragmentation, was indicated by a less rapid increase in CFU, and 3 weeks was required to reach the PCC. Experiments with field soil revealed that saprophytic fungal growth was limited, presumably due to competition from the indigenous soil microflora, and that the PCR results were less variable than the equivalent plate count results. In addition, the limit of detection of V. chlamydosporium in field soil was lower than that in gamma-irradiated soil, suggesting that there was a background population of the fungus in the field, although the level was below the limit of detection. Tomatoes were infected with the root knot nematode (RKN) or the potato cyst nematode (PCN) along with a PCN-derived isolate of the fungus (V. chlamydosporium isolate Jersey). Increases in fungal growth were observed in the rhizosphere of PCN-infested plants but not in the rhizosphere of RKN-infested plants after 14 weeks using cPCR. In this paper we describe for the first time PCR-based quantification of a fungal biological control agent for nematodes in soil and the rhizosphere, and we provide evidence for nematode host specificity that is highly relevant to the biological control efficacy of this fungus. 相似文献
105.
A single-chain class II MHC-IgG3 fusion protein inhibits autoimmune arthritis by induction of antigen-specific hyporesponsiveness 总被引:1,自引:0,他引:1
Zuo L Cullen CM DeLay ML Thornton S Myers LK Rosloniec EF Boivin GP Hirsch R 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(5):2554-2559
T cells play a central role in many autoimmune diseases. A method to specifically target the function of autoreactive T cell clones would avoid the global immunosuppression associated with current therapies. To develop a molecule capable of inhibiting autoreactive T cell responses in vivo, single-chain peptide-I-A-IgG3 fusion proteins were constructed and expressed in both mammalian and insect cells. The fusion proteins were designed with an IgG3 Fc moiety to make them divalent, allowing TCR cross-linking, while lacking FcR binding and costimulation. The fusion proteins stimulated T cell hybridomas in vitro in a peptide-specific, MHC-restricted manner but failed to do so in soluble form. In vivo administration of an I-A(q) fusion protein, containing an immunodominant collagen II peptide, significantly delayed the onset and reduced the severity of collagen-induced arthritis in DBA/1 mice by induction of Ag-specific hyporesponsiveness. Such fusion proteins may be useful to study novel therapeutic approaches for T cell-mediated autoimmune diseases. 相似文献
106.
The inhibition of telomerase activity in actively dividing cells leads to suppression of cell growth after a time delay (inhibitory delay) required to reach a threshold telomeric DNA size. We developed a mathematical model of the dynamics of telomere size distribution and cell growth in the presence of telomere inhibitors that allowed quantification of the inhibitory delay. The model based on the solution of a system of differential equations described quantitatively recent experimental data on dynamics of cultured cells in presence of telomerase inhibitors. The analysis of the data by this model suggested the existence of at least two distinct subpopulations of cells with different proliferative activity. Size distribution of telomeres, fraction of proliferating cells, and tumor doubling times are of critical importance for the dynamics of cancer cells growth in presence of telomerase inhibitors. Rapidly growing cells with large telomeric DNA heterogeneity and small proliferating fractions as well as those with very short homogeneous telomeres would be the most sensitive to telomerase inhibitors. 相似文献
107.
Prior vaccination increases the epitopic breadth of the cytotoxic T-lymphocyte response that evolves in rhesus monkeys following a simian-human immunodeficiency virus infection 下载免费PDF全文
Santra S Barouch DH Kuroda MJ Schmitz JE Krivulka GR Beaudry K Lord CI Lifton MA Wyatt LS Moss B Hirsch VM Letvin NL 《Journal of virology》2002,76(12):6376-6381
Although recent evidence has confirmed the importance of cytotoxic T-lymphocyte (CTL) responses in controlling human immunodeficiency virus type 1 and simian immunodeficiency virus replication, the relevance of the epitopic breadth of those CTL responses remains unexplored. In the present study, we sought to determine whether vaccination can expand CTL populations which recognize a repertoire of viral epitopes that is greater than is typically generated in the course of a viral infection. We demonstrate that potent secondary CTL responses to subdominant epitopes are rapidly generated following a pathogenic simian-human immunodeficiency virus challenge of rhesus monkeys vaccinated with plasmid DNA or recombinant modified vaccinia virus Ankara vaccines. These data indicate that prior vaccination can increase the breadth of the CTL response that evolves after an AIDS virus infection. 相似文献
108.
Lum MR Li Y Larue TA David-Schwartz R Kapulnik Y Hirsch AM 《Integrative and comparative biology》2002,42(2):295-303
The nitrogen-fixing symbiosis between Rhizobiaceae and legumes is one of the best-studied interactions established between prokaryotes and eukaryotes. The plant develops root nodules in which the bacteria are housed, and atmospheric nitrogen is fixed into ammonia by the rhizobia and made available to the plant in exchange for carbon compounds. It has been hypothesized that this symbiosis evolved from the more ancient arbuscular mycorrhizal (AM) symbiosis, in which the fungus associates with roots and aids the plant in the absorption of mineral nutrients, particularly phosphate. Support comes from several fronts: 1) legume mutants where Nod(-) and Myc(-) co-segregate, and 2) the fact that various early nodulin (ENOD) genes are expressed in legume AM. Both strongly argue for the idea that the signal transduction pathways between the two symbioses are conserved. We have analyzed the responses of four classes of non-nodulating Melilotus alba (white sweetclover) mutants to Glomus intraradices (the mycorrhizal symbiont) to investigate how Nod(-) mutations affect the establishment of this symbiosis. We also re-examined the root hair responses of the non-nodulating mutants to Sinorhizobium meliloti (the nitrogen-fixing symbiont). Of the four classes, several sweetclover sym mutants are both Nod(-) and Myc(-). In an attempt to decipher the relationship between nodulation and mycorrhiza formation, we also performed co-inoculation experiments with mutant rhizobia and Glomus intraradices on Medicago sativa, a close relative of M. alba. Even though sulfated Nod factor was supplied by some of the bacterial mutants, the fungus did not complement symbiotically defective rhizobia for nodulation. 相似文献
109.
Schindler JF Godbey A Hood WF Bolten SL Broadus RM Kasten TP Cassely AJ Hirsch JL Merwood MA Nagy MA Fok KF Saabye MJ Morgan HM Compton RP Mourey RJ Wittwer AJ Monahan JB 《Biochimica et biophysica acta》2002,1598(1-2):88-97
The kinetic mechanism of mitogen-activated protein kinase activated protein kinase-2 (MAPKAPK2) was investigated using a peptide (LKRSLSEM) based on the phosphorylation site found in serum response factor (SRF). Initial velocity studies yielded a family of double-reciprocal lines that appear parallel and indicative of a ping-pong mechanism. The use of dead-end inhibition studies did not provide a definitive assignment of a reaction mechanism. However, product inhibition studies suggested that MAPKAPK2 follows an ordered bi-bi kinetic mechanism, where ATP must bind to the enzyme prior to the SRF-peptide and the phosphorylated product is released first, followed by ADP. In agreement with these latter results, surface plasmon resonance measurements demonstrate that the binding of the inhibitor peptide to MAPKAPK2 requires the presence of ATP. Furthermore, competitive inhibitors of ATP, adenosine 5'-(beta,gamma-imino)triphosphate (AMPPNP) and a staurosporine analog (K252a), can inhibit this ATP-dependent binding providing further evidence that the peptide substrate binds preferably to the E:ATP complex. 相似文献
110.
AGAP1, an endosome-associated,phosphoinositide-dependent ADP-ribosylation factor GTPase-activating protein that affects actin cytoskeleton 总被引:7,自引:0,他引:7
Nie Z Stanley KT Stauffer S Jacques KM Hirsch DS Takei J Randazzo PA 《The Journal of biological chemistry》2002,277(50):48965-48975
We have identified three members of the AGAP subfamily of ASAP family ADP-ribosylation factor GTPase-activating proteins (Arf GAPs). In addition to the Arf GAP domain, these proteins contain GTP-binding protein-like, ankyrin repeat and pleckstrin homology domains. Here, we have characterized the ubiquitously expressed AGAP1/KIAA1099. AGAP1 had Arf GAP activity toward Arf1>Arf5>Arf6. Phosphatidylinositol 4,5-bisphosphate and phosphatidic acid synergistically stimulated GAP activity. As found for other ASAP family Arf GAPs, the pleckstrin homology domain was necessary for activity. Deletion of the GTP-binding protein-like domain affected lipid dependence of Arf GAP activity. In vivo effects of AGAP1 were distinct from other ASAP family Arf GAPs. Overexpressed AGAP1 induced the formation of and was associated with punctate structures containing the endocytic markers transferrin and Rab4. AP1 was redistributed from the trans-Golgi to the punctate structures. Like other ASAP family members, AGAP1 overexpression inhibited the formation of PDGF-induced ruffles. However, distinct from other ASAP family members, AGAP1 also induced the loss of actin stress fibers. Thus, AGAP1 is a phosphoinositide-dependent Arf GAP that impacts both the endocytic compartment and actin. 相似文献