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1.
Summary. Complete depolymerization of actin filaments (AFs) at low temperature (0 °C) is followed by the formation of transient actin
structures at 25 °C in tobacco BY-2 cells (Nicotiana tabacum L.). Using antibodies against fission yeast actin-related proteins (ARP2 and ARP3), we show here that transient actin structures
(dots, dotted filaments, rods) colocalize with epitopes stained by these antibodies and thus are likely to represent sites
of actin filament nucleation (SANs). In contrast to the cold-induced disassembly of AFs, no transient actin structures were
detectable during recovery of AFs from latrunculin B-induced depolymerization. However, the staining pattern obtained with
ARP antibodies in latrunculin B-treated cells was similar to that in controls and cold-treated cells. This suggests that,
in addition to the complete depolymerization of AFs, disruption of other cellular structures is needed for the formation of
transient actin structures during the early phase of recovery from cold treatment.
Correspondence and reprints: Department of Plant Physiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague
2, Czech Republic. 相似文献
2.
The organization of cortical microtubules at wound sites in Nitella pseudoflabellata(A. Br. & Nordst.) em. R.D.W. and N. flexilis(L.) Ag. internodal cells was examined in relation to the regeneration of actin filament bundles in order to identify the mechanisms
by which microtubules are oriented. Actin bundle regrowth occurs prior to that of microtubules, so it was considered possible
that microtubule alignment is actin-dependent, perhaps mediated by cross-linking proteins. In all types of wounds investigated,
subcortical actin bundles regenerated parallel to the direction of cytoplasmic streaming. Microtubule orientation patterns,
however, varied according to the nature of wound formation and the type of wound wall eventually produced. In chloroplast-free
windows induced by blue light irradiation, microtubule orientation varied according to the size of the window. Microtubules
were randomized in 10- to 30-μm-wide windows where exposure to cytoplasmic flow is minimal, but were aligned more or less
parallel to regenerated actin bundles in 80- to 100-μm-wide windows. Where co-alignment between microtubules and actin bundles
was obvious after fluorescence labelling, electron micrographs revealed that microtubules and actin bundles were too widely
spaced to account for any cross-linkages. Furthermore, treatments that inhibited or reduced cytoplasmic streaming without
altering the direction of actin bundles caused randomization of microtubules previously oriented in the streaming direction,
even in the presence of taxol. When evenly flat wound walls were induced by 10−4 M chlortetracycline, microtubules were co-aligned with nearby actin bundles at the surface of the wound wall. At wounds induced
by treatment with 5 × 10−2 M CaCl2, however, microtubules were randomly oriented and preferentially located in the narrow clefts between the wound-wall protuberances,
up to several micrometers away from the actin bundles near the wound-wall tips. These results indicate that microtubules regenerated
in wounds are merely co-aligned with actin filament bundles because they are passively aligned by the hydrodynamic forces
created by cytoplasmic flow.
Received: 4 August 1998 / Accepted: 30 January 1999 相似文献
3.
Summary. Pollen and skeletal muscle actins were purified and labeled with fluorescent dyes that have different emission wavelengths. Observation by electron microscopy shows that the fluorescent actins are capable to polymerize into filamentous actin in vitro, bind to myosin S-1 fragments, and have a critical concentration similar to unlabeled actin, indicating that they are functionally active. The globular actins from two sources were mixed and polymerized by the addition of ATP and salts. The copolymerization experiment shows that when excited by light of the appropriate wavelength, both red actin filaments (pollen actin) and green actin filaments (muscle actin) can be visualized under the microscope, but no filaments exhibiting both green and red colors are detected. Furthermore, coprecipitations of labeled pollen actin with unlabeled pollen and skeletal muscle actin were performed. Measurements of fluorescent intensity show that the amount of labeled pollen actin precipitating with pollen actin was much higher than that with skeletal muscle actin, indicating that pollen and muscle actin tend not to form heteropolymers. Injection of labeled pollen actin into living stamen hair cells results in the formation of normal actin filaments in transvacuolar strands and the cortical cytoplasm. In contrast, labeled skeletal muscle actin has detrimental effects on the cellular architecture. The results from coinjection of the actin-disrupting reagent cytochalasin D with pollen actin show that overexpression of pollen actin prolongs the displacement of the nucleus and facilitates the recovery of the nuclear position, actin filament architecture, and transvacuolar strands. However, muscle actin perturbs actin filaments when injected into stamen hair cells. Moreover, nuclear displacement occurs more rapidly when cytochalasin D and muscle actin are coinjected into the cell. It is concluded that actins from plant and animal sources behave differently in vitro and in vivo and that they are functionally not interchangeable. 相似文献
4.
Seiji Sonobe 《Journal of plant research》1996,109(4):437-448
Vacuoles in plant cells can be eliminated by centrifugation of protoplasts through a density gradient. In this review, properties
of evacuolated protoplasts, named ‘miniprotoplasts’, and the significant roles in plant cytoskeleton studies are described.
Miniprotoplasts, prepared from tobacco BY-2 cells whose cell-cycle had been synchronized at late anaphase, continued to divide
to form two daughter cells. In the presence of cytochalasin B cytokinetic cleavage was enhanced, suggesting a role of actin
filaments in plant cytokinesis. In the cytoplasmic extract of miniprotoplasts both tubulin and actin could be polymerized
to form microtubules (MTs) and actin filaments (AFs), respectively. A purification method for tubulin, actin and related proteins
was developed using the extract. To investigate the interaction between cortical microtubules and the plasma membrane, an
experimental system in which MTs were reconstructed on membrane ghosts was developed by combination of membrane ghosts and
the extract. 相似文献
5.
Summary. Plant cells typically contain a large central vacuole that confines the cytoplasm and organelles to the periphery of the cell and the vicinity of the nucleus. These two domains are often connected by transvacuolar strands (TVS), thin tubular structures that traverse the vacuole. The TVS are thought to act as important transport routes for the distribution of organelles and metabolites, and also to play a role in the positioning of the nucleus. Most TVS depend on internal actin filaments for their existence, and rearrangements of TVS can therefore indicate modifications in the actin cytoskeleton. In this study we describe time-lapse observations of tobacco BY-2 suspension-cultured cells that document the dynamic behavior of TVS. The TVS formed, branched, and collapsed, and their attachment points in the nuclear or cortical cytoplasm, as well as on other TVS, moved around. These dynamic rearrangements were inhibited within 5min by the myosin inhibitor 2,3-butanedione monoxime (BDM). In particular, the movements of TVS attachment points and the variations in TVS length were significantly reduced in the presence of the drug. Similarly, movements of the nucleus were reduced by two thirds in BDM-treated cells. The number of TVS, together with the number of attachment and branch points, also dropped during BDM treatment. All effects of BDM on TVS dynamics were reversible upon removal of the drug. These results suggest a role for myosin motors in the rearrangement of TVS, which is likely to occur through their interaction with actin filaments.Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1007/s00709-004-0068-0Present address: Zentrum für Molekulare Biologie, Universität Heidelberg, Heidelberg, Federal Republic of Germany. 相似文献
6.
Summary. The effects of aluminium on the actin filament (AF) cytoskeleton of Triticum turgidum meristematic root tip cells were examined. In short treatments (up to 2 h) with 50–1000 μM AlCl3·6H2O, interphase cells displayed numerous AFs arrayed in thick bundles that lined the plasmalemma and traversed the endoplasm
in different directions. Measurements using digital image analysis and assessment of the overall AF fluorescence revealed
that, in short treatments, the affected cells possessed 25–30% more AFs than the untreated ones. The thick AF bundles were
not formed in the Al-treated cells in the presence of the myosin inhibitors 2,3-butanedione monoxime (BDM) and 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine
(ML-7), a fact suggesting that myosins are involved in AF bundling. In longer Al treatments, the AF bundles were disorganised,
forming granular actin accumulations, a process that was completed after 4 h of treatment. In the Al-treated cells, increased
amounts of callose were uniformly deposited along the whole surface of the cell walls. In contrast, callose formed local deposits
in the Al-treated cells in the presence of cytochalasin B, BDM, or ML-7. These results favour the hypothesis that the actomyosin
system in the Al-treated cells, among other roles, participates in the mechanism controlling callose deposition.
Correspondence and reprints: Department of Botany, Faculty of Biology, University of Athens, Athens 157 84, Greece. 相似文献
7.
A. Pérez-García S. Pereira J. Pissarra A. García Gutiérrez F. M. Cazorla R. Salema A. de Vicente F. M. Cánovas 《Planta》1998,206(3):426-434
In tomato (Lycopersicon esculentum Mill.) leaves, the predominant glutamine synthetase (GS; EC 6.3.1.2) is chloroplastic (GS2; 45 kDa) whereas the cytosolic
isoform (GS1; 39 kDa) is represented as a minor enzyme. Following either infection by Pseudomonas syringae pv. tomato (Pst) or treatment with phosphinothricin (PPT), a GS inhibitor, GS1 accumulated in the leaves. In contrast to
healthy control leaves, where GS1 was restricted to the veins, in infected and PPT-treated leaves the GS1 polypeptide was
also detected in the leaf blade; moreover, it was more abundant than GS2. Different immunological approaches were therefore
used to investigate whether or not the GS1 polypeptide expressed in Pst-infected and PPT-treated tomato leaves was distributed
among different tissues and subcellular compartments in the same way as the constitutive GS1 expressed in healthy leaves.
By tissue-printing analysis, a similar GS immunostaining was observed in epidermis, mesophyll and phloem of leaflet midrib
cross-sections of control, infected and PPT-treated leaves. Immunocytochemical localization revealed that GS protein was present
in the chloroplast of mesophyll cells and the cytoplasm of phloem cells in healthy leaves; however, in Pst-infected or PPT-treated
leaves, a strong labelling was observed in the cytoplasm of mesophyll cells. Two-dimensional analysis of GS polypeptides showed
that, in addition to the constitutive GS1, a GS1 polypeptide different in charge was present in tomato leaflets after microbial
infection or herbicide treatment. All these results indicate that a novel cytosolic GS is induced in mesophyll cells of Pst-infected
or PPT-treated leaves. A possible role for this new cytosolic GS in the remobilization of leaf nitrogen during infection is
proposed.
Received: 16 January 1998 / Accepted 21 April 1998 相似文献
8.
The orientation of microtubules (MTs) was examined in epidermal cells of azuki bean (Vigna angularis Ohwi et Ohashi) epicotyls. The orientation of MTs adjacent to the outer tangential wall of the cells, which has a crossed
polylamellate structure with lamellae of longitudinal cellulose microfibrils alternating with lamellae of transverse cellulose
microfibrils, differed from one cell to another. Treatment with an auxin-free solution caused the accumulation of cells with
longitudinal MTs and subsequent treatment with a solution that contained auxin resulted in the accumulation of cells with
transverse MTs, showing that sequential treatments with auxin-free and auxin-containing solutions can synchronize the reorientation
of MTs. The MTs, once reoriented from longitudinal to transverse, returned to longitudinal and then back to transverse once
again, the duration of the cycle being about 6 h. Gibberellic acid, known to increase the percentage of cells with transverse
MTs, promoted reorientation of MTs from longitudinal to transverse and inhibited that from transverse to longitudinal. Cytochalasin
D, an agent that disrupts actin filaments, speeded up the reorientation from transverse to longitudinal and slowed down that
from longitudinal to transverse. It caused an increase in the percentage of cells with MTs in mixed orientation, and the percentage
of such cells was highest when the percentage of cells with longitudinal MTs was decreasing and that of cells with transverse
MTs was increasing.
Received: 27 November 1997 / Accepted: 7 January 1998 相似文献
9.
The influence of the mycorrhizal fungus Gigaspora margarita on cytoskeleton organisation in epidermal cells of Lotus japonicus roots was compared between plants of the wild type Gifu and the mutant Ljsym4-2, in which the fungus is confined to the epidermal cells. Immunofluorescence labelling of plant microtubules and microfilaments showed only limited alterations in the peripheral cytoskeleton of epidermal cells during early stages of fungal interaction with the wild type. Later, microtubules and microfilaments enveloped the growing hypha, while the host cell nucleus moved close to the fungus. In contrast, epidermal cells of the mutant responded with disorganisation and disassembly of microtubules and microfilaments before and during fungal penetration attempts. The fungus penetrated only as far as to epidermal cells, whose cytoplasm became devoid of tubulin and actin, suggesting cell death. The close relationship between host cytoskeleton organisation and compatibility with the fungus suggests that a functional Ljsym4 gene is necessary for correct reorganisation of the epidermal cell cytoskeleton in the presence of the fungus and for avoiding hypersensitivity-like reactions. 相似文献
10.
In many types of plant cell, bundles of actin filaments (AFs) are generally involved in cytoplasmic streaming and the organization
of transvacuolar strands. Actin cross-linking proteins are believed to arrange AFs into the bundles. In root hair cells of
Hydrocharis dubia (Blume) Baker, a 135-kDa polypeptide cross-reacted with an antiserum against a 135-kDa actin-bundling protein (135-ABP),
a villin homologue, isolated from lily pollen tubes. Immunofluorescence microscopy revealed that the 135-kDa polypeptide co-localized
with AF bundles in the transvacuolar strand and in the sub-cortical region of the cells. Microinjection of antiserum against
135-ABP into living root hair cells induced the disappearance of the transvacuolar strand. Concomitantly, thick AF bundles
in the transvacuolar strand dispersed into thin bundles. In the root hair cells, AFs showed uniform polarity in the bundles,
which is consistent with the in-vitro activity of 135-ABP. These results suggest that villin is a factor responsible for bundling
AFs in root hair cells as well as in pollen tubes, and that it plays a key role in determining the direction of cytoplasmic
streaming in these cells.
Received: 16 September 1999 / Accepted: 3 December 1999 相似文献
11.
Cytoskeletal alterations in interphase cells of the green alga Spirogyra decimina in response to heavy metals exposure: I. The effect of cadmium 总被引:1,自引:0,他引:1
Summary. The aim of the study was to elucidate the effect of cadmium ions on the arrangement of the actin and tubulin cytoskeleton,
as well as the relationships between cytoskeletal changes and growth processes in the green filamentous alga Spirogyra decimina. Batch cultures of algae were carried out under defined conditions in the presence of various cadmium concentrations. In
control cells, the cytoskeleton appeared to be a transversely oriented pattern of both microtubules and actin filaments of
various thickness in the cell cortex; colocalization of cortical microtubules and actin filaments was apparent. Microtubules
were very sensitive to the presence of cadmium ions. Depending on the cadmium concentration and the time of exposure, microtubules
disintegrated into short rod-shaped fragments or they completely disappeared. A steep increase in cell width and a decrease
in growth rate accompanied (and probably ensued) a very rapid disintegration of microtubules. Actin filaments were more stable
because they were disturbed several hours later than microtubules at any cadmium concentration used. When cadmium ions were
washed out, the actin cytoskeleton was rebuilt even in cells in which actin filaments were completely disintegrated at higher
cadmium concentrations (40 or 100 μM). The much more sensitive microtubules were regenerated after treatment with lower cadmium
concentrations (10 or 15 μM) only.
Correspondence and reprints: Centre of Phycology, Institute of Botany, Academy of Sciences of the Czech Republic, Dukelská
135, 379 82 Třeboň, Czech Republic. 相似文献
12.
Cell wall pectins and xyloglucans are internalized into dividing root cells and accumulate within cell plates during cytokinesis 总被引:7,自引:0,他引:7
Baluska F Liners F Hlavacka A Schlicht M Van Cutsem P McCurdy DW Menzel D 《Protoplasma》2005,225(3-4):141-155
Recently, we have reported that cell wall pectins are internalized into apical meristem root cells. In cells exposed to the fungal metabolite brefeldin A, all secretory pathways were inhibited, while endocytic pathways remained intact, resulting in accumulation of internalized cell wall pectins within brefeldin A-induced compartments. Here we report that, in addition to the already published cell wall epitopes, rhamnogalacturonan I and xyloglucans also undergo large-scale internalization into dividing root cells. Interestingly, multilamellar endosomes were identified as compartments internalizing arabinan cell wall pectins reactive to the 6D7 antibody, while large vacuole-like endosomes internalized homogalacturonans reactive to the 2F4 antibody. As all endosomes belong topographically to the exocellular space, cell wall pectins deposited in these "cell wall islands", enclosed by the plasma-membrane-derived membrane, are ideally suited to act as temporary stores for rapid formation of cell wall and generation of new plasma membrane. In accordance with this notion, we report that all cell wall pectins and xyloglucans that internalize into endosomes are highly enriched within cytokinetic cell plates and accumulate within brefeldin A compartments. On the other hand, only small amounts of the pectins reactive to the JIM7 antibody, which are produced in the Golgi apparatus, localize to cell plates and they do not accumulate within brefeldin A compartments. In conclusion, meristematic root cells have developed pathways for internalization and recycling of cell wall molecules which are relevant for plant-specific cytokinesis. 相似文献
13.
Summary. In most higher-plant cells, cortical microtubules form a tightly focused preprophase band (PPB) that disappears with the onset
of prometaphase, but whose location defines the future location of the cell plate at the end of cytokinesis. It is unclear
whether the PPB microtubules themselves designate the precise area where the cell plate will insert, or rather if these microtubules
are responding to a hierarchical signal(s). Here we show that narrowing of the microtubules within the PPB zone is not necessary
for proper division plane determination. In cultured tobacco BY-2 cells in which PPB microtubules are depolymerized, the phragmoplast
can still accurately locate and insert at the proper site. The data do not support a role for PPB microtubule narrowing in
focusing the signal that is used later by the phragmoplast to position the cell plate; rather, proper phragmoplast positioning
is more likely a consequence of a non-microtubule positional element. Although the PPB microtubules do not directly mark the
division site, we show that they are required for accurate spindle positioning, an activity that presets the future growth
trajectory of the phragmoplast and is necessary for insuring high-fidelity cell plate positioning.
Correspondence and reprints: Department of Biology, Pennsylvania State University, University Park, PA 16802, U.S.A.
Present address: Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia, U.S.A. 相似文献
14.
Summary. In higher-plant cells, microtubules, actin microfilaments, and vacuoles play important roles in a variety of cellular events,
including cell division, morphogenesis, and cell differentiation. These intracellular structures undergo dynamic changes in
their shapes and functions during cell division and differentiation, and to analyse these sequential structural changes, the
vital labelling technique, using the green-fluorescent protein or other fluorescent proteins, has commonly been used to follow
the localisation and translocation of specific proteins. To visualise microtubules, actin filaments, and vacuoles, several
strategies are available for selecting the appropriate fluorescent-protein fusion partner: microtubule-binding proteins, tubulin,
and plus-end-tracking proteins are most suitable for microtubule labelling; the actin binding domain of mouse talin and plant
fimbrin for actin microfilament visualisation; and the tonoplast-intrinsic proteins and syntaxin-related proteins for vacuolar
imaging. In addition, three-dimensional reconstruction methods are indispensable for localising the widely distributed organelles
within the cell. The maximum intensity projection method is suitable for cytoskeletal structures, while contour-based surface
modelling possesses many advantages for vacuolar membranes. In this article, we summarise the recent progress in living cell
imaging of the plant cytoskeleton and vacuoles using various fusions with green-fluorescent proteins and three-dimensional
imaging techniques.
Correspondence and reprints: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo,
Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8562, Japan. 相似文献
15.
Vadim Y. Kryukov Marsel R. Kabilov Natalya Smirnova Oksana G. Tomilova Maksim V. Tyurin Yuriy B. Akhanaev Olga V. Polenogova Viktor P. Danilov Saule K. Zhangissina Tatiana Alikina Olga N. Yaroslavtseva Viktor V. Glupov 《Fungal biology》2019,123(12):927-935
Strains of entomopathogenic fungi may have substantial differences in their final stages of mycosis. Insect cadavers are usually overgrown with mycelium after colonization of the insect body, but in many cases, bacterial decomposition of the colonized hosts occurs. We used two Metarhizium robertsii strains in the work: Mak-1 (cadavers become overgrown with mycelium and conidia) and P-72 (cadavers decay after fungal colonization). We conducted a comparative analysis of gut and cadaver microbiota in Colorado potato beetle larvae using 16S rRNA gene sequencing after infection with these strains. In addition, we estimated the content of different forms of nitrogen in cadavers and the influence of cadavers on the growth of Solanum lycopersicum on sand substrates under laboratory conditions. It was shown that infections did not lead to a significant shift in the midgut bacterial communities of infected insects compared to those of untreated insects. Importantly, bacterial communities were similar in both types of cadaver, with predominantly enterobacteria. Decomposing cadavers (P-72) were characterized by increased nitrate and ammonium, and they had a stronger growth-promoting effect on plants compared to cadavers overgrown with mycelium and conidia (Mak-1). We also estimated the colonization and growth of plants after treatment with conidia of both strains cultivated on artificial medium. Both cultures successfully colonized plants, but strain P-72 showed stronger growth promotion than Mak-1. We propose that the use of deviant strains that are unable to sporulate on cadavers leads to a faster (though only passive) flow of nitrogen from killed insects to plants. 相似文献
16.
Summary. Human SH-SY5Y neuroblastoma cells were used to study the effects of altered gravity on the actin and microtubule cytoskeleton
dynamics. A cholinergic stimulation of the cells during a 6 min period of changing gravity (3 parabolas) resulted in an enhanced
actin-driven protrusion of evoked lamellipodia. Likewise, the spontaneous protrusive activity of nonactivated cells was promoted
during exposure to changing gravity (6 up to 31 parabolas). Ground-based experiments revealed a similar enhancement of the
spontaneous and evoked lamellar protrusive activity when the cells were kept at 2 g hypergravity for at least 6 min. This gravity response was independent of the direction of the acceleration vector in respect
to the cells. Exposure of the cells to “simulated weightlessness” (clinorotation) had no obvious influence on this type of
lamellar actin cytoskeleton dynamics. A 20 min exposure of the cells to simulated weightlessness or to changing gravity (6
to 31 parabolas) – but not to 2 g (hypergravity, centrifugation) – resulted in an altered arrangement of microtubules indicated by bending, turning, and loop
formation. A similar altered arrangement was shown by microtubules which had polymerized into lamellipodia after release from
a taxol block at simulated weightlessness (clinorotation) or during changing gravity (5 parabolas). Our data suggest that
in human SH-SY5Y neuroblastoma cells, microgravity affects the dynamics and spatial arrangement of microtubules but has no
influence on the Rac-controlled lamellar actin cytoskeleton dynamics and cell spreading. The latter, however, seems to be
promoted at hypergravity.
Correspondence and reprints: Cell and Developmental Neurobiology, Institute of Zoology, University of Hohenheim, Garbenstrasse
30, 70593 Stuttgart, Federal Republic of Germany. 相似文献
17.
Rhizoids and protonemata of characean algae: model cells for research on polarized growth and plant gravity sensing 总被引:1,自引:0,他引:1
Gravitropically tip-growing rhizoids and protonemata of characean algae are well-established unicellular plant model systems for research on gravitropism. In recent years, considerable progress has been made in the understanding of the cellular and molecular mechanisms underlying gravity sensing and gravity-oriented growth. While in higher-plant statocytes the role of cytoskeletal elements, especially the actin cytoskeleton, in the mechanisms of gravity sensing is still enigmatic, there is clear evidence that in the characean cells actin is intimately involved in polarized growth, gravity sensing, and the gravitropic response mechanisms. The multiple functions of actin are orchestrated by a variety of actin-binding proteins which control actin polymerisation, regulate the dynamic remodelling of the actin filament architecture, and mediate the transport of vesicles and organelles. Actin and a steep gradient of cytoplasmic free calcium are crucial components of a feedback mechanism that controls polarized growth. Experiments performed in microgravity provided evidence that actomyosin is a key player for gravity sensing: it coordinates the position of statoliths and, upon a change in the cell's orientation, directs sedimenting statoliths to specific areas of the plasma membrane, where contact with membrane-bound gravisensor molecules elicits short gravitropic pathways. In rhizoids, gravitropic signalling leads to a local reduction of cytoplasmic free calcium and results in differential growth of the opposite subapical cell flanks. The negative gravitropic response of protonemata involves actin-dependent relocation of the calcium gradient and displacement of the centre of maximal growth towards the upper flank. On the basis of the results obtained from the gravitropic model cells, a similar fine-tuning function of the actomyosin system is discussed for the early steps of gravity sensing in higher-plant statocytes. 相似文献
18.
Kawakami K Kinjo Y Uezu K Yara S Miyagi K Koguchi Y Nakayama T Taniguchi M Saito A 《Microbiology and immunology》2002,46(3):207-210
We elucidated the contribution of Valpha14 NKT cells to Th1 response and host resistance against mycobacterial infection. In Valpha14 NKT cell-deficient mice, host defense and DTH response to Mycobacterium bovis BCG were not different from wild-type mice after pulmonary infection. There was no significant difference in the lung concentrations of IFN-gamma between the two strains of mice. In addition, host defense to systemic infection with M. tuberculosis was similar to that of M. bovis. Our results indicate that Valpha14 NKT cells play only a marginal role, if any, in the Th1 response and host resistance to mycobacterial infection. 相似文献
19.
20.
Ceramide has been proposed to be an important signaling intermediate in tumor necrosis factor (TNF)-induced apoptosis in human MCF-7 breast adenocarcinoma cells. We compared cell death and signal transduction pathways induced by TNF and ceramide in TNF-sensitive, parental MCF-7 cells to those in TNF-resistant, MCF-7 cells (3E9). TNF caused proteolysis of the caspase substrate, polyADP-ribose polymerase (PARP) in parental cells, but not in 3E9 cells. Both apoptosis and PARP cleavage were strongly prevented by co-incubation with caspase inhibitors. In contrast, ceramide-induced cell death was neither affected by TNF resistance nor was it associated with PARP cleavage, and death could not be prevented by co-incubation with caspase inhibitors in either cell line. TNF was able to activate JNK/SAPK approximately 30-fold and approximately 5-fold in parental MCF-7 and 3E9 cells, respectively; in contrast, cell-permeable ceramide only weakly stimulated JNK/SAPK activity in either cell type. Although JNK was activated by TNF, pharmacological blockade of the JNK pathway did not inhibit TNF- or ceramide-mediated cell death. Using mass spectroscopic analysis for ceramide, no increase, rather, a decrease in total ceramide content in TNF-treated parental cells was observed. These results suggest that the cell death signaling and execution pathways utilized by ceramide are distinct from those activated by TNF in MCF-7 cells. 相似文献