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1.
Nat Commun ; 14(1): 508, 2023 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-36720884

RESUMO

Global environmental change is identified as a driver of physical transformation of coral reef islands over the past half-century, and next 100 years, posing major adaptation challenges to island nations. Here we resolve whether these recent documented changes in islands are unprecedented compared with the pre-industrial era. We utilise radiometric dating, geological, and remote sensing techniques to document the dynamics of a Maldivian reef island at millennial to decadal timescales. Results show the magnitude of island change over the past half-century (±40 m movement) is not unprecedented compared with paleo-dynamic evidence that reveals large-scale changes in island dimension, shape, beach levels, as well as positional changes of ±200 m since island formation ~1,500 years ago. Results highlight the value of a multi-temporal methodological approach to gain a deeper understanding of the dynamic trajectories of reef islands, to support development of adaptation strategies at timeframes relevant to human security.


Assuntos
Aclimatação , Povo Asiático , Humanos , Recifes de Corais , Geologia
2.
Biochem Cell Biol ; 95(1): 5-11, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28129513

RESUMO

Pathogenic bacteria from the families Neisseriaeceae and Moraxellaceae acquire iron from their host using surface receptors that have the ability to hijack iron from the iron-sequestering host proteins transferrin (Tf) and lactoferrin (Lf). The process of acquiring iron from Tf has been well-characterized, including the role of the surface lipoprotein transferrin-binding protein B (TbpB). In contrast, the only well-defined role for the homologue, LbpB, is in its protection against cationic antimicrobial peptides, which is mediated by regions present in some LbpBs that are highly enriched in glutamic or aspartic acid. In this study we compare the Tf-TbpB and the Lf-LbpB interactions and examine the protective effect of LbpB against extracts from human and transgenic mouse neutrophils to gains insights into the physiological roles of LbpB. The results indicate that in contrast to the Tf-TbpB interaction, Lf-LbpB interaction is sensitive to pH and varies between species. In addition, the results with transgenic mouse neutrophils raise the question of whether there is species specificity in the cleavage of Lf to generate cationic antimicrobial peptides or differences in the potency of peptides derived from mouse and human Lf.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Transporte/metabolismo , Lactoferrina/metabolismo , Neisseria meningitidis/metabolismo , Neutrófilos/metabolismo , Proteína B de Ligação a Transferrina/metabolismo , Transferrina/metabolismo , Animais , Anti-Infecciosos/metabolismo , Células Cultivadas , Humanos , Infecções Meningocócicas/microbiologia , Camundongos , Camundongos Transgênicos , Neisseria meningitidis/patogenicidade , Neutrófilos/citologia
3.
J Exp Bot ; 67(8): 2231-46, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26962208

RESUMO

Previous studies have shown that the beneficial effect of suppression of the Arabidopsis phytoglobin 2 gene, PGB2, on somatic embryogenesis occurs through the accumulation of nitric oxide (NO) within the embryogenic cells originating from the cultured explant. NO activates the expression of Allene oxide synthase (AOS) and Lipoxygenase 2 (LOX2), genes encoding two key enzymes of the jasmonic acid (JA) biosynthetic pathway, elevating JA content within the embryogenic tissue. The number of embryos in the single aos1-1 mutant and pgb2-aos1-1 double mutant declined, and was not rescued by increasing levels of NO stimulating embryogenesis in wild-type tissue. NO also influenced JA responses by up-regulating PLANT DEFENSIN 1 (PDF1) and JASMONATE-ZIM-PROTEIN (JAZ1), as well as down-regulating MYC2. The NO and JA modulation of MYC2 and JAZ1 controlled embryogenesis. Ectopic expression of JAZ1 or suppression of MYC2 promoted the formation of somatic embryos, while repression of JAZ1 and up-regulation of MYC2 reduced the embryogenic performance. Sustained expression of JAZ1 induced the transcription of several indole acetic acid (IAA) biosynthetic genes, resulting in higher IAA levels in the embryogenic cells. Collectively these data fit a model integrating JA in the PGB2 regulation of Arabidopsis embryogenesis. Suppression of PGB2 increases JA through NO. Elevated levels of JA repress MYC2 and induce JAZ1, favoring the accumulation of IAA in the explants and the subsequent production of somatic embryos.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/embriologia , Arabidopsis/metabolismo , Ciclopentanos/metabolismo , Leghemoglobina/metabolismo , Oxilipinas/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Vias Biossintéticas/efeitos dos fármacos , Vias Biossintéticas/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Ácidos Indolacéticos/metabolismo , Leghemoglobina/genética , Modelos Biológicos , Óxido Nítrico/farmacologia , Transcrição Gênica/efeitos dos fármacos
4.
Mucosal Immunol ; 9(4): 1051-64, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26693700

RESUMO

Women with asymptomatic Neisseria gonorrhoeae infection are at risk of developing pelvic inflammatory disease (PID) if the bacteria ascend from the endocervix into the uterus and oviducts. Factors that affect disease severity, ranging from mild discomfort to severe inflammation, pain, and infertility, remain elusive. Herein we perform direct transcervical inoculation of N. gonorrhoeae into the uterus of mice to establish an infection that leads to PID. Profoundly different disease outcomes were apparent at different stages of the reproductive cycle. Mice that were infected during the diestrus stage of the reproductive cycle displayed extensive gonococcal penetration into the submucosa, severe inflammation, and clinical signs reflecting discomfort. Meanwhile, infection during the intervening estrus stage showed only modest effects. Furthermore, a gonococcal-specific humoral response was only elicited following the penetrative upper genital tract (UGT) infection during diestrus but not estrus. Strikingly, the potential for antibodies to contribute to protection during re-infection also depends upon the reproductive stage, as antigonococcal antibodies within the genital tract were markedly higher when mice were in diestrus. Combined, this work establishes a robust new model reflecting gonococcal PID in humans and reveals how the reproductive cycle determines the pathogenic outcome of gonococcal infections of the UGT.


Assuntos
Diestro/imunologia , Genitália Feminina/imunologia , Gonorreia/imunologia , Neisseria gonorrhoeae/imunologia , Doença Inflamatória Pélvica/imunologia , Animais , Anticorpos Antibacterianos/sangue , Doenças Assintomáticas , Modelos Animais de Doenças , Estro/imunologia , Feminino , Genitália Feminina/microbiologia , Imunidade Humoral , Memória Imunológica , Camundongos , Camundongos Endogâmicos
5.
Methods Mol Biol ; 1224: 59-66, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25416249

RESUMO

Plants are susceptible to infection by a broad range of fungal pathogens. A range of proteins have been evaluated that can enhance tolerance to these pathogens by heterologous expression in transgenic carrot tissues. The protocols for carrot transformation with Arabidopsis NPR1 (Non-Expressor of Pathogenesis-Related Proteins 1) are described in this chapter, using the herbicide resistance gene bar, which encodes phosphinothricin acetyltransferase, as a selectable marker. In this protocol, petiole segments (0.5-1.0 cm long) from aseptically grown carrot seedlings are exposed to Agrobacterium tumefaciens strain LBA4404 for 10-30 min and cocultivated for 2-3 days. Herbicide selection is then imposed for 8-12 weeks on a series of different tissue culture media until embryogenic calli are produced. The transfer of the embryogenic calli to hormone-free medium results in embryo development which eventually gives rise to transgenic plantlets. Embryogenic calli can also be propagated in suspension cultures. This protocol has yielded transgenic carrot plants with defined T-DNA inserts at the rate of between 1 and 3 Southern-positive independent events out of 100.


Assuntos
Daucus carota/crescimento & desenvolvimento , Daucus carota/genética , Engenharia Genética/métodos , Transformação Genética , Acetiltransferases/genética , Agrobacterium tumefaciens/genética , Proteínas de Arabidopsis/genética , Resistência a Herbicidas/genética , Esterilização
6.
Plant Physiol ; 165(2): 810-825, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24784758

RESUMO

Programmed cell death (PCD) in multicellular organisms is a vital process in growth, development, and stress responses that contributes to the formation of tissues and organs. Although numerous studies have defined the molecular participants in apoptotic and PCD cascades, successful identification of early master regulators that target specific cells to live or die is limited. Using Zea mays somatic embryogenesis as a model system, we report that the expressions of two plant hemoglobin (Hb) genes (ZmHb1 and ZmHb2) regulate the cell survival/death decision that influences somatic embryogenesis through their cell-specific localization patterns. Suppression of either of the two ZmHbs is sufficient to induce PCD through a pathway initiated by elevated NO and Zn2+ levels and mediated by production of reactive oxygen species. The effect of the death program on the fate of the developing embryos is dependent on the localization patterns of the two ZmHbs. During somatic embryogenesis, ZmHb2 transcripts are restricted to a few cells anchoring the embryos to the subtending embryogenic tissue, whereas ZmHb1 transcripts extend to several embryonic domains. Suppression of ZmHb2 induces PCD in the anchoring cells, allowing the embryos to develop further, whereas suppression of ZmHb1 results in massive PCD, leading to abortion. We conclude that regulation of the expression of these ZmHbs has the capability to determine the developmental fate of the embryogenic tissue during somatic embryogenesis through their effect on PCD. This unique regulation might have implications for development and differentiation in other species.

7.
Plant Signal Behav ; 8(8)2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23759548

RESUMO

Plant hemoglobins are ubiquitous molecules involved in several aspects of plant development and stress responses. Studies on the functional aspects of plant hemoglobins at the cellular level in these processes are limited, despite their ability to scavenge nitric oxide (NO), an important signal molecule interfering with hormone synthesis and sensitivity. This mini-review summarizes current knowledge on plant hemoglobins, analyzes their participation in plant pathogen interaction and embryogenesis and proposes a possible model centering on jasmonic acid (JA) as a downstream component of hemoglobin responses.


Assuntos
Hemoglobinas/metabolismo , Interações Hospedeiro-Patógeno , Plantas/embriologia , Plantas/metabolismo , Ciclopentanos/metabolismo , Modelos Biológicos , Óxido Nítrico/metabolismo , Oxilipinas/metabolismo
8.
Planta ; 237(4): 1065-82, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23242073

RESUMO

Altered expression of Brassica napus (Bn) SHOOTMERISTEMLESS (STM) affects the morphology and behaviour of microspore-derived embryos (MDEs). While down-regulation of BnSTM repressed the formation of the shoot meristem (SAM) and reduced the number of Brassica MDEs able to regenerate viable plants at germination, over-expression of BnSTM enhanced the structure of the SAM and improved regeneration frequency. Within dissected SAMs, the induction of BnSTM up-regulated the expression of many transcription factors (TFs) some of which directly involved in the formation of the meristem, i.e. CUP-SHAPED COTYLEDON1 and WUSCHEL, and regulatory components of the antioxidant response, hormone signalling, and cell wall synthesis and modification. Opposite expression patterns for some of these genes were observed in the SAMs of MDEs down-regulating BnSTM. Altered expression of BnSTM affected transcription of cell wall and lignin biosynthetic genes. The expression of PHENYLALANINE AMMONIA LYASE2, CINNAMATE 4-4HYDROXYLASE, and CINNAMYL ALCOHOL DEHYDROGENASE were repressed in SAMs over-expressing BnSTM. Since lignin formation is a feature of irreversible cell differentiation, these results suggest that one way in which BnSTM promotes indeterminate cell fate may be by preventing the expression of components of biochemical pathways involved in the accumulation of lignin in the meristematic cells. Overall, these studies provide evidence for a novel function of BnSTM in enhancing the quality of in vitro produced meristems, and propose that this gene can be used as a potential target to improve regeneration of cultured embryos.


Assuntos
Proteínas de Arabidopsis/metabolismo , Brassica napus/metabolismo , Proteínas de Homeodomínio/metabolismo , Meristema/metabolismo , Brassica napus/embriologia , Brassica napus/ultraestrutura , Parede Celular/metabolismo , Regulação para Baixo , Perfilação da Expressão Gênica , Microdissecção e Captura a Laser , Lignina/biossíntese , Meristema/ultraestrutura
9.
PLoS One ; 7(8): e43990, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22952840

RESUMO

Liuwei Dihuang (LWDH), a classic Chinese medicinal formula, has been used to improve or restore declined functions related to aging and geriatric diseases, such as impaired mobility, vision, hearing, cognition and memory. Here, we report on the effect and possible mechanisms of LWDH mediated protection of ß-amyloid (Aß) induced paralysis in Caenorhabditis elegans using ethanol extract (LWDH-EE) and water extract (LWDH-WE). Chemical profiling and quantitative analysis revealed the presence of different levels of bioactive components in these extracts. LWDH-WE was rich in polar components such as monosaccharide dimers and trimers, whereas LWDH-EE was enriched in terms of phenolic compounds such as gallic acid and paeonol. In vitro studies revealed higher DPPH radical scavenging activity for LWDH-EE as compared to that found for LWDH-WE. Neither LWDH-EE nor LWDH-WE were effective in inhibiting aggregation of Aß in vitro. By contrast, LWDH-EE effectively delayed Aß induced paralysis in the transgenic C. elegans (CL4176) model which expresses human Aß1-42. Western blot revealed no treatment induced reduction in Aß accumulation in CL4176 although a significant reduction was observed at an early stage with respect to ß-amyloid deposition in C. elegans strain CL2006 which constitutively expresses human Aß1-42. In addition, LWDH-EE reduced in vivo reactive oxygen species (ROS) in C. elegans (CL4176) that correlated with increased survival of LWDH-EE treated N2 worms under juglone-induced oxidative stress. Analysis with GFP reporter strain TJ375 revealed increased expression of hsp16.2::GFP after thermal stress whereas a minute induction was observed for sod3::GFP. Quantitative gene expression analysis revealed that LWDH-EE repressed the expression of amy1 in CL4176 while up-regulating hsp16.2 induced by elevating temperature. Taken together, these results suggest that LWDH extracts, particularly LWDH-EE, alleviated ß-amyloid induced toxicity, in part, through up-regulation of heat shock protein, antioxidant activity and reduced ROS in C. elegans.


Assuntos
Peptídeos beta-Amiloides/toxicidade , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/genética , Medicamentos de Ervas Chinesas/farmacologia , Sequestradores de Radicais Livres/farmacologia , Fragmentos de Peptídeos/toxicidade , Peptídeos beta-Amiloides/química , Animais , Animais Geneticamente Modificados , Compostos de Bifenilo/química , Caenorhabditis elegans/metabolismo , Química Farmacêutica , Medicamentos de Ervas Chinesas/análise , Medicamentos de Ervas Chinesas/química , Medicamentos de Ervas Chinesas/uso terapêutico , Etanol/química , Sequestradores de Radicais Livres/análise , Sequestradores de Radicais Livres/química , Sequestradores de Radicais Livres/uso terapêutico , Estresse Oxidativo/efeitos dos fármacos , Paralisia/induzido quimicamente , Paralisia/tratamento farmacológico , Fragmentos de Peptídeos/química , Picratos/química , Multimerização Proteica/efeitos dos fármacos , Estrutura Secundária de Proteína , Água/química
10.
Mucosal Immunol ; 5(3): 320-31, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22354319

RESUMO

Infection with Neisseria gonorrhoeae does not induce specific immunity or immune memory. Our previous studies in a murine model of vaginal gonococcal infection showed that innate immunity governed by Th17 cells was a critical aspect of the immune response elicited by this pathogen. Herein we show that N. gonorrhoeae selectively inhibited Th1 and Th2 cells and enhanced Th17 cell development through the induction of TGF-ß. Whereas Th17 responses depended on gonococcal lipooligosaccharide acting through TLR4, the inhibitory effect of N. gonorrhoeae on Th1/Th2 responses involved gonococcal Opa proteins. In vitro Th17 responses to N. gonorrhoeae could be diverted to Th1/Th2 by blockade of TGF-ß, but not by blockade of IL-17. The results reveal that N. gonorrhoeae suppresses Th1/Th2-mediated adaptive immune response through mechanisms dependent on TGF-ß, and that this effect can be manipulated to promote the development of adaptive immunity.


Assuntos
Gonorreia/imunologia , Neisseria gonorrhoeae/imunologia , Células Th1/imunologia , Células Th17/imunologia , Células Th2/imunologia , Fator de Crescimento Transformador beta/metabolismo , Imunidade Adaptativa , Animais , Células Cultivadas , Modelos Animais de Doenças , Humanos , Evasão da Resposta Imune , Imunidade Inata , Memória Imunológica , Imunomodulação , Camundongos , Camundongos Endogâmicos , Camundongos Knockout , Células Th1/microbiologia , Células Th17/microbiologia , Células Th2/microbiologia , Fator de Crescimento Transformador beta/genética
11.
J Biol Chem ; 276(26): 24331-40, 2001 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-11306560

RESUMO

Neisseria gonorrhoeae express opacity-associated (Opa) protein adhesins that mediate binding to various members of the carcinoembryonic antigen-related cellular adhesion molecule (CEACAM; previously CD66) receptor family. Although human umbilical vein endothelial cells express little CEACAM receptor in vitro, we found neisserial infection to induce expression of CEACAM1, CEACAM1-3L, and CECAM1-4L splice variants. This mediates an increased Opa(52)-dependent binding of gonococci by these cells. The induced receptor expression did not require bacterial Opa expression, but it was more rapid with adherent bacteria. Because the time course of induction was similar to that seen for induced proinflammatory cytokines, we tested whether CEACAM1 expression could be controlled by a similar mechanism. Gonococcal infection activated a nuclear factor-kappaB (NF-kappaB) heterodimer consisting of p50 and p65, and inhibitors that prevent the nuclear translocation of activated NF-kappaB complex inhibited CEACAM1 transcript expression. Each of these effects could be mimicked by using culture filtrates or purified lipopolysaccharide instead of intact bacteria. Together, our results support a model whereby the outer membrane "blebs" that are actively released by gonococci trigger a Toll-like receptor-4-dependent activation of NF-kappaB, which up-regulates the expression of CEACAM1 to allow Opa(52)-mediated neisserial binding. The regulation of CEACAM1 expression by NF-kappaB also implies a broader role for this receptor in the general inflammatory response to infection.


Assuntos
Antígenos CD/biossíntese , Antígenos de Diferenciação/biossíntese , Aderência Bacteriana , Proteínas de Drosophila , Endotélio Vascular/microbiologia , NF-kappa B/metabolismo , Neisseria gonorrhoeae/patogenicidade , Antígenos de Bactérias/fisiologia , Antígenos CD/genética , Antígenos de Diferenciação/genética , Proteínas da Membrana Bacteriana Externa/fisiologia , Moléculas de Adesão Celular , Células Cultivadas , Citocinas/biossíntese , Citocinas/genética , Endotélio Vascular/metabolismo , Humanos , Proteínas Imediatamente Precoces/metabolismo , Cinética , Glicoproteínas de Membrana/fisiologia , Modelos Biológicos , Isoformas de Proteínas/biossíntese , Isoformas de Proteínas/genética , RNA Mensageiro/biossíntese , Receptores de Superfície Celular/fisiologia , Receptor 4 Toll-Like , Receptores Toll-Like , Ativação Transcricional , Fator de Necrose Tumoral alfa/biossíntese , Fator de Necrose Tumoral alfa/genética
12.
Mol Microbiol ; 38(1): 103-13, 2000 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11029693

RESUMO

Helicobacter pylori can colonize the gastric epithelium of humans, leading to the induction of an intense inflammatory response with the infiltration of mainly polymorphonuclear leucocytes (PMNs) and monocytes. These professional phagocytes appear to be a primary cause of the damage to surface epithelial layers, and probably contribute to the pathogenesis associated with persistent H. pylori infections. We have shown previously that H. pylori adheres to professional phagocytes, but is not engulfed efficiently, suggesting an antiphagocytic escape mechanism that is dependent on the pathogen's type IV secretion system. Here, we show that H. pylori induces the generation and extracellular release of oxygen metabolites as a consequence of its attachment to phagocytic cells, but is capable of surviving this response. The catalase activity of H. pylori is apparently essential for survival at the phagocytes' cell surface. Opsonization of H. pylori leads to an increased burst, and the inhibition of bacterial protein synthesis to a decreased one. Ca2+ concentration, cytoskeleton rearrangement and protein kinase C (PKC) are involved in the H. pylori-induced oxidative burst in both monocytes and PMNs. This survival phenomenon has important implications for both the persistence of this important pathogen and the host tissue damage that accompanies persistent H. pylori infection.


Assuntos
Catalase/metabolismo , Helicobacter pylori/fisiologia , Fagócitos/metabolismo , Espécies Reativas de Oxigênio , Helicobacter pylori/enzimologia , Explosão Respiratória
13.
Mol Microbiol ; 37(6): 1389-404, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10998171

RESUMO

Gastric infections by Helicobacter pylori are characteristically associated with an intense inflammation and infiltration of mainly polymorphonuclear lymphocytes (PMNs) and monocytes. The inflammatory response by infiltrated immune cells appears to be a primary cause of the damage to surface epithelial layers and may eventually result in gastritis, peptic ulcer, gastric cancer and/or MALT-associated gastric lymphoma. Our analysis of the interaction between H. pylori and PMNs and monocytes revealed that H. pylori inhibits its own uptake by these professional phagocytes. To some degree, this effect resembles antiphagocytosis by Yersinia enterocolitica. Increasing numbers of bacteria associated per cell are more efficient at blocking their own engulfment. In H. pylori, bacterial protein synthesis is necessary to block phagocytic uptake, as shown by the time and concentration dependence of the bacteriostatic protein synthesis inhibitor chloramphenicol. Furthermore, H. pylori appears broadly to inhibit the phagocytic function of monocytes and PMNs, as infection with H. pylori abrogates the phagocytes' ability to engulf latex beads or adherent Neisseria gonorrhoeae cells. This antiphagocytic phenotype depends on distinct virulence (vir) genes, such as virB7 and virB11, encoding core components of a putative type IV secretion apparatus. Our data indicate that H. pylori exhibits an antiphagocytic activity that may play an essential role in the immune escape of this persistent pathogen.


Assuntos
Helicobacter pylori/metabolismo , Helicobacter pylori/patogenicidade , Fagócitos/microbiologia , Fagocitose/fisiologia , Fatores de Virulência , Aderência Bacteriana , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/efeitos dos fármacos , Proteínas de Bactérias/genética , Antígenos de Grupos Sanguíneos , Cloranfenicol/farmacologia , Helicobacter pylori/efeitos dos fármacos , Humanos , Microscopia Confocal , Microscopia Eletrônica de Varredura , Monócitos/microbiologia , Mutação , Neutrófilos/microbiologia , Inibidores da Síntese de Proteínas/farmacologia , Especificidade da Espécie , Virulência/genética
15.
Subcell Biochem ; 33: 61-96, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10804852

RESUMO

As outlined in this review, various experimental techniques have been employed in an attempt to understand neisserial pathogenesis. In vitro genetic analysis has been used to study the genetic basis for the structural variability of cell surface components. Transformed or primary epithelial cell cultures have provided the simplest model to analyze bacterial adherence and invasion, while the infection of polarized epithelial monolayers, fallopian tube and nasopharyngeal organ cultures, and ureteral tissue have each been used to more closely represent the events which occur in vivo. Finally, the in vivo infection of human volunteers with N. gonorrhoeae has provided a powerful means to confirm and expand the results obtained in vitro. By these various approaches, a number of neisserial adhesins (i.e. pilli, Opa, Opc and P36) and additional putative virulence determinants which affect bacterial adherence and invasion into host cells (i.e. LOS, capsule, PorB) have been identified. Clearly, neisserial surface variation serves as an adaptive mechanism which can modulate tissue tropism, immune evasion and survival in the changing host environment. Important progress has been made in recent years with respect to the host cellular receptors and subsequent signal transduction processes which are involved in neisserial adherence, invasion and transcytosis. This has led to the identification of (i) CD46 as a receptor for pilus which allows adherence to epithelial and endothelial cells, (ii) HSPGs, in cooperation with vitronectin and fibronectin, as receptors for a particular subset of Opa proteins and Opc, which may both mediate invasion into most epithelial and endothelial cells, and (iii) CD66 as the receptors for most Opa variants, potentially being involved in cellular interactions including adherence, invasion and transcytosis with epithelial, endothelial and phagocytic cells. As most of these data have been obtained using transformed cell lines growing in vitro, attempts must be made to translate these basic observations into a more natural situation. It can be expected that the successful ongoing integration of laboratory findings from the various infection models with human volunteer studies will further increase our understanding of the biology of neisserial infection. Perhaps the most difficult but also most rewarding challenge for the future will be to use volunteer studies to identify and understand the role of host factors which are important for the infectious process. Hopefully, insights gained from each of these studies will reveal new and useful strategies for the preventive and/or therapeutic intervention into infection and disease by these fascinating microbes.


Assuntos
Neisseria gonorrhoeae/patogenicidade , Neisseria meningitidis/patogenicidade , Animais , Humanos
16.
Infect Immun ; 68(6): 3601-7, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10816518

RESUMO

The carcinoembryonic antigen (CEA) family member CEACAM1 (previously called biliary glycoprotein or CD66a) was previously shown to function as a receptor that can mediate the binding of Opa protein-expressing Neisseria meningitidis to both neutrophils and epithelial cells. Since neutrophils and polarized epithelia have both been shown to coexpress multiple CEACAM receptors, we have now extended this work to characterize the binding specificity of meningococcal Opa proteins with other CEA family members. To do so, we used recombinant Escherichia coli expressing nine different Opa variants from three meningococcal strains and stably transfected cell lines expressing single members of the CEACAM family. These infection studies demonstrated that seven of the nine Opa variants bound to at least one CEACAM receptor and that binding to each of these receptors is sufficient to trigger the Opa-dependent bacterial uptake by these cell lines. The other two Opa variants do not appear to bind to either CEACAM receptors or heparan sulfate proteoglycan receptors, which are bound by some gonococcal Opa variants, thus implying a novel class of Opa proteins. We have also extended previous studies by demonstrating induction of CEACAM1 expression after stimulation of human umbilical vein endothelial cells with the proinflammatory cytokine tumor necrosis factor alpha, which is present in high concentrations during meningococcal disease. This induced expression of CEACAM1 leads to an increased Opa-dependent bacterial binding and invasion into the primary endothelia, implying that these interactions may play an important role in the pathogenesis of invasive meningococcal disease.


Assuntos
Antígenos de Bactérias/metabolismo , Proteínas da Membrana Bacteriana Externa/metabolismo , Antígeno Carcinoembrionário/metabolismo , Endotélio Vascular/microbiologia , Neisseria meningitidis/patogenicidade , Receptores de Superfície Celular/metabolismo , Antígenos de Bactérias/genética , Aderência Bacteriana , Proteínas da Membrana Bacteriana Externa/genética , Citocinas , Endotélio Vascular/efeitos dos fármacos , Escherichia coli/genética , Variação Genética , Humanos , Ligação Proteica , Proteínas Recombinantes/metabolismo , Fator de Necrose Tumoral alfa/farmacologia
17.
Cell Microbiol ; 1(2): 169-81, 1999 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11207550

RESUMO

The carcinoembryonic antigen (CEA) gene family members, CEACAM1, CEACAM3, CEACAM5 and CEACAM6, are bound by the Opa outer membrane proteins of pathogenic Neisseria spp., whereas CEACAM8 is not. In this study, we demonstrate that the closely related CEACAM4 and CEACAM7, which are also members of the CEA family, are not Opa receptors. We exploited the high conservation between CEACAM6 and CEACAM8 to generate an extensive set of chimeric receptors in order to delineate the sequences necessary for Opa binding. Using a transfection-based infection system, we showed that binding of Opa52 involves residues 27-42, which are predicted to form beta-strand C and short loops adjacent to it, and residues lying between amino acids 60 and 108 in the amino-terminal domain. The replacement of residues 27-29 in CEACAM6 with the CEACAM1 or CEACAM5 sequences generated recombinant CEACAM6 receptors that are bound by CEACAM1/CEACAM5-specific Opa variants. Together, our data demonstrate that Opa proteins bind to residues exposed on the GFCC' face of the N-terminal domain of CEACAM receptors, and identify an amino acid triplet sequence that is responsible for the differential binding of Opa proteins to CEACAM1, CEACAM5 and CEACAM6.


Assuntos
Antígenos de Bactérias/química , Proteínas da Membrana Bacteriana Externa/química , Antígeno Carcinoembrionário/metabolismo , Neisseria gonorrhoeae/química , Sequência de Aminoácidos , Animais , Antígenos de Bactérias/metabolismo , Proteínas da Membrana Bacteriana Externa/metabolismo , Antígeno Carcinoembrionário/genética , Linhagem Celular , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Neisseria gonorrhoeae/metabolismo , Ligação Proteica , Estrutura Secundária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Alinhamento de Sequência
18.
Mol Microbiol ; 30(3): 657-71, 1998 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-9822830

RESUMO

We have analysed the capacity of the 11 phase-variable, opacity-associated (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to mediate traversal across polarized monolayers of the human colonic carcinoma T84 cell line. Gonococci expressing either the heparan sulphate proteoglycan (HSPG) binding Opa protein (Opa50) or no Opa protein (Opa-) did not interact with the apical pole of T84 monolayers, whereas the 10 variant Opa proteins previously shown to bind CD66 receptors were found to mediate efficient gonococcal adherence and transepithelial traversal. Consistent with this, T84 cells were shown by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting to co-express CD66a (BGP), CD66c (NCA) and CD66e (CEA). The recruitment of CD66 receptors by Opa-expressing gonococci indicates their involvement in mediating adherence to the surface of T84 cells, and these bacterial interactions could be inhibited completely using polyclonal antibodies cross-reacting with all of the CD66 proteins co-expressed on T84 cells. Consistent results were obtained when Opa proteins were expressed in Escherichia coli, suggesting that the Opa-CD66 interaction is sufficient to mediate bacterial traversal. Transcytosis of Opa-expressing N. gonorrhoeae or E. coli did not disrupt the barrier function of infected monolayers, as indicated by a sustained transepithelial electrical resistance (TEER) throughout the course of infection, and confocal laser scanning and electron microscopy both suggest a transcellular rather than a paracellular route of traversal across the monolayers. Parallels between the results seen here and previous work done with organ cultures confirm that T84 monolayers provide a valid model for studying neisserial interactions with the mucosal surface, and suggest that CD66 receptors contribute to this process in vivo.


Assuntos
Antígenos de Bactérias/metabolismo , Antígenos CD/metabolismo , Antígenos de Diferenciação/metabolismo , Neisseria gonorrhoeae/patogenicidade , Anticorpos/farmacologia , Antígenos CD/imunologia , Antígenos de Diferenciação/imunologia , Aderência Bacteriana/fisiologia , Infecções Bacterianas/microbiologia , Moléculas de Adesão Celular , Membrana Celular/ultraestrutura , Endocitose/fisiologia , Escherichia coli/genética , Imunofluorescência , Regulação Bacteriana da Expressão Gênica/genética , Humanos , Microscopia Confocal , Microscopia Eletrônica , Neisseria gonorrhoeae/metabolismo , RNA Mensageiro/genética , Receptores de Superfície Celular/metabolismo , Fatores de Tempo , Células Tumorais Cultivadas
19.
Trends Microbiol ; 6(12): 489-95, 1998 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-10036728

RESUMO

Pathogenic Neisseria spp. possess a repertoire of phase-variable Opa proteins that mediate various pathogen--host cell interactions, including bacterial engulfment by epithelial cells and opsonin-independent phagocytosis by professional phagocytes. Recent studies have identified cellular targets recognized by defined Opa proteins and have begun to reveal host signalling events involved in mediating these Opa-dependent cellular processes.


Assuntos
Antígenos de Bactérias/fisiologia , Neisseria gonorrhoeae/fisiologia , Neisseria meningitidis/fisiologia , Animais , Antígenos CD/metabolismo , Antígenos de Diferenciação/metabolismo , Moléculas de Adesão Celular , Células Epiteliais/microbiologia , Proteoglicanas de Heparan Sulfato/metabolismo , Humanos
20.
Mol Microbiol ; 25(5): 979-87, 1997 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-9364922

RESUMO

Ferric-binding proteins (FbpA) have been implicated in the transferrin receptor-mediated iron acquisition pathways of Haemophilus influenzae and Neisseria spp. These proteins are believed to function by shuttling iron from outer membrane transferrin receptors to a specific inner membrane permease complex. However, the role of these proteins has not been conclusively resolved, as attempts at creating isogenic mutants in the fbpA genes of both species have been unsuccessful, prompting the hypothesis that FbpA may play a critical role in H. influenzae and Neisseria spp. This study describes the construction and characterization of an H. influenzae isogenic fbpA mutant. It is demonstrated that this mutant is deficient in its ability to use human transferrin as a sole iron source, even though the strain is still competent for binding human transferrin. It is also demonstrated that this mutant is impaired in its ability to use ferric citrate as an iron source, and grows at a reduced rate relative to wild type in broth supplemented with protoporphyrin rather than haemin.


Assuntos
Compostos Férricos , Haemophilus influenzae/genética , Metaloproteínas/genética , Sequência de Bases , Divisão Celular/fisiologia , Teste de Complementação Genética , Haemophilus influenzae/química , Immunoblotting , Metaloproteínas/análise , Mutagênese/genética , Mutação
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