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951.
Duchez S Rodrigues M Bertrand F Valitutti S 《Journal of immunology (Baltimore, Md. : 1950)》2011,187(9):4571-4580
Cognate interactions between T and B lymphocytes lead to the formation of the immunological synapse (IS) where bidirectional activation signals are exchanged. Although the molecular architecture and the function of the IS have been studied extensively on the T cell side, little is known about events occurring during synapse formation in Ag-presenting B cells. We investigated the impact of BCR and TLR signaling on human B cell activation and on the T and B cell side of the IS. On the T cell side, we observed that T cells polarized toward both naive and previously activated B cells. Nevertheless, when T cells interacted with different B cells simultaneously, T cells selectively polarized their secretory machinery toward preactivated B cells. Furthermore, both naive and preactivated B cells reoriented their microtubule-organizing center toward the synaptic T cell during cognate interactions. This phenomenon was rapid and not dependent on T cell secretory activity. Interestingly, not only the microtubule-organizing center but also the Golgi apparatus and Lamp-3(+) and MHC class II(+) vesicles all repositioned beneath the IS, suggesting that the entire endocytic/exocytic B cell compartment was reoriented toward the T cell. Taken together, our results show that the B cell activation status fine-tunes T cell polarization responses and reveal the capacity of naive and activated B cells to polarize toward T cells during cognate interactions. 相似文献
952.
Bordiec S Paquis S Lacroix H Dhondt S Ait Barka E Kauffmann S Jeandet P Mazeyrat-Gourbeyre F Clément C Baillieul F Dorey S 《Journal of experimental botany》2011,62(2):595-603
Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms that colonize the rhizosphere of many plant species and confer beneficial effects, such as an increase in plant growth. PGPR are also well known as inducers of systemic resistance to pathogens in plants. However, the molecular mechanisms involved locally after direct perception of these bacteria by plant cells still remain largely unknown. Burkholderia phytofirmans strain PsJN is an endophytic PGPR that colonizes grapevine and protects the plant against the grey mould disease caused by Botrytis cinerea. This report focuses on local defence events induced by B. phytofirmans PsJN after perception by the grapevine cells. It is demonstrated that, after addition to cell suspension cultures, the bacteria were tightly attaching to plant cells in a way similar to the grapevine non-host bacteria Pseudomonas syringae pv. pisi. B. phytofirmans PsJN perception led to a transient and monophasic extracellular alkalinization but no accumulation of reactive oxygen species or cell death were detected. By contrast, challenge with P. syringae pv. pisi induced a sustained and biphasic extracellular alkalinization, a two phases oxidative burst, and a HR-like response. Perception of the PGPR also led to the production of salicylic acid (SA) and the expression of a battery of defence genes that was, however, weaker in intensity compared with defence gene expression triggered by the non-host bacteria. Some defence genes up-regulated after B. phytofirmans PsJN challenge are specifically induced by exogenous treatment with SA or jasmonic acid, suggesting that both signalling pathways are activated by the PGPR in grapevine. 相似文献
953.
The folding and interactions of amyloid proteins are at the heart of the debate as to how these proteins may or may not become toxic to their host. Although little is known about this issue, the structure seems to be clearly involved with effects on molecular events. To understand how an amyloid may be toxic, we previously generated a yeast toxic amyloid (mutant 8) from the nontoxic HET-s(218-289) prion domain of Podospora anserina. Here, we performed a comprehensive structure-toxicity study by mutating individually each of the 10 mutations found in mutant 8. The study of the library of new mutants generated allowed us to establish a clear link between Fourier transform infrared antiparallel signature and amyloid toxicity. All of the mutants that form parallel β-sheets are not toxic. Double mutations may be sufficient to shift a parallel structure to antiparallel amyloids, which are toxic to yeast. Our findings also suggest that the toxicity of antiparallel structured mutants may be linked to interaction with membranes. 相似文献
954.
Fan J Stukas S Wong C Chan J May S DeValle N Hirsch-Reinshagen V Wilkinson A Oda MN Wellington CL 《Journal of lipid research》2011,52(9):1605-1616
Lipid transport in the brain is coordinated by glial-derived lipoproteins that contain apolipoprotein E (apoE) as their primary protein. Here we show that apoE is secreted from wild-type (WT) primary murine mixed glia as nascent lipoprotein subspecies ranging from 7.5 to 17 nm in diameter. Negative-staining electron microscropy (EM) revealed rouleaux, suggesting a discoidal structure. Potassium bromide (KBr) density gradient ultracentrifugation showed that all subspecies, except an 8.1 nm particle, were lipidated. Glia lacking the cholesterol transporter ABCA1 secreted only 8.1 nm particles, which were poorly lipidated and nondiscoidal but could accept lipids to form the full repertoire of WT apoE particles. Receptor-associated-protein (RAP)-mediated inhibition of apoE receptor function blocked appearance of the 8.1 nm species, suggesting that this particle may arise through apoE recycling. Selective deletion of the LDL receptor (LDLR) reduced the level of 8.1 nm particle production by approximately 90%, suggesting that apoE is preferentially recycled through the LDLR. Finally, apoA-I stimulated secretion of 8.1 nm particles in a dose-dependent manner. These results suggest that nascent glial apoE lipoproteins are secreted through multiple pathways and that a greater understanding of these mechanisms may be relevant to several neurological disorders. 相似文献
955.
Ursø B Ilondo MM Holst PA Christoffersen CT Ouwens M Giorgetti S Van Obberghen E Naor D Tornqvist H De Meyts P 《Cellular signalling》2003,15(4):385-394
Insulin and growth hormone (GH) induce mitogenic and metabolic signals in cells, GH either directly or indirectly via IGF-I production. We have studied a spontaneous murine T-cell lymphoma (LB cells) devoid of IGF-1 receptors in which proliferation is maintained by insulin [Int. J. Cancer 50 (1992) 80], and show that GH is more potent than insulin, with both GH and insulin dose-response curves for thymidine incorporation being bell-shaped. Binding showed somatogenic rather than lactogenic GH receptors. Insulin stimulated phosphorylation of the insulin receptor and of a 160-kDa protein, identified as the IRS-4 protein. This phosphorylated IRS-4 associated with PI3-kinase, which was activated along with the downstream p70(S6) kinase, whereas the Ras-MAPK pathway was not. Using selective inhibitors, the PI3-kinase, but not p70(S6) kinase or MEK, was found to be involved in insulin-stimulated DNA synthesis. GH induced tyrosine phosphorylation of IRS-4 and nuclear translocation of STAT5. The LB cells constitute a new model for studying GH and insulin signalling without interference of IGF-1 receptors. 相似文献
956.
Yous S Durieux-Poissonnier S Lipka-Belloli E Guelzim H Bochu C Audinot V Boutin JA Delagrange P Bennejean C Renard P Lesieur D 《Bioorganic & medicinal chemistry》2003,11(5):753-759
Tetrahydronaphthalenic analogues of melatonin have been synthesized and evaluated as melatonin receptor ligands. Introduction of a phenyl substituent in the 3-position of the tetraline ring allows to obtain MT(2) selective ligands. Activity and MT(2) selectivity can be modulated with suitable modifications of the N-acyl substituent. The (+)-(RR)-cis enantiomer of the N-[2-(7-methoxy-3-phenyl-1,2,3,4-tetrahydro-naphthalen-1-yl)ethyl]cyclobutyl carboxamide (14) is one of the most MT(2) selective ligands described until now and behaves as an antagonist. 相似文献
957.
The histone hairpin binding protein (HBP, also called SLBP, which stands for stem-loop binding protein) binds specifically to a highly conserved hairpin structure located in the 3' UTR of the cell-cycle-dependent histone mRNAs. HBP consists of a minimal central RNA binding domain (RBD) flanked by an N- and C-terminal domain. The yeast three-hybrid system has been used to investigate the critical residues of the human HBP involved in the binding of its target hairpin structure. By means of negative selections followed by positive selections, we isolated mutant HBP species. Our results indicate tight relationships between the RBD and the N- and C-terminal domains. 相似文献
958.
Jessie Lilly Hannele H. Honkanen Jessica R. Rodger Diego del Villar Patrick Boylan Amy Green Diego Pereiro Lorna Wilkie Richard Kennedy Andrea Barkley Robert Rosell Niall Ó. Maoiléidigh Ross O'Neill Catherine Waters Deirdre Cotter David Bailey William Roche Ross McGill James Barry Samantha V. Beck Jim Henderson Debbie Parke Frederick G. Whoriskey Brian Shields Philip Ramsden Silas Walton Melanie Fletcher Ken Whelan Colin W. Bean Sophie Elliott Adrian Bowman Colin E. Adams 《Journal of fish biology》2024,104(1):265-283
The freshwater phase of the first seaward migration of juvenile Atlantic salmon (Salmo salar) is relatively well understood when compared with our understanding of the marine phase of their migration. In 2021, 1008 wild and 60 ranched Atlantic salmon smolts were tagged with acoustic transmitters in 12 rivers in England, Scotland, Northern Ireland and Ireland. Large marine receiver arrays were deployed in the Irish Sea at two locations: at the transition of the Irish Sea into the North Atlantic between Ireland and Scotland, and between southern Scotland and Northern Ireland, to examine the early phase of the marine migration of Atlantic salmon smolts. After leaving their natal rivers' post-smolt migration through the Irish Sea was rapid with minimum speeds ranging from 14.03 to 38.56 km.day−1 for Atlantic salmon smolts that entered the Irish Sea directly from their natal river, to 9.69–39.94 km.day−1 for Atlantic salmon smolts that entered the Irish Sea directly from their natal estuary. Population minimum migration success through the study area was strongly correlated with the distance of travel, populations further away from the point of entry to the open North Atlantic exhibited lower migration success. Post-smolts from different populations experienced different water temperatures on entering the North Atlantic. This was largely driven by the timing of their migration and may have significant consequences for feeding and ultimately survivorship. The influence of water currents on post-smolt movement was investigated using data from previously constructed numerical hydrodynamic models. Modeled water current data in the northern Irish Sea showed that post-smolts had a strong preference for migrating when the current direction was at around 283° (west-north-west) but did not migrate when exposed to strong currents in other directions. This is the most favorable direction for onward passage from the Irish Sea to the continental shelf edge current, a known accumulation point for migrating post-smolts. These results strongly indicate that post-smolts migrating through the coastal marine environment are: (1) not simply migrating by current following (2) engage in active directional swimming (3) have an intrinsic sense of their migration direction and (4) can use cues other than water current direction to orientate during this part of their migration. 相似文献
959.
960.
Immune memory has traditionally been the domain of the adaptive immune system, present only in antigen‐specific T and B cells. The purpose of this review is to summarize the evidence for immunological memory in lower organisms (which are not thought to possess adaptive immunity) and within specific cell subsets of the innate immune system. A special focus will be given to recent findings in both mouse and humans for specificity and memory in natural killer (NK) cells, which have resided under the umbrella of innate immunity for decades. The surprising longevity and enhanced responses of previously primed NK cells will be discussed in the context of several immunization settings. 相似文献