The inhibitory effects of N-ethylmaleimide, colchicine and cytochalasins on human T-cell functions

Freed, Brian M.; Lempert, Neil; Lawrence, David A.

doi:10.1016/0192-0561(89)90174-4

Cited by 26 publications

(18 citation statements)

References 21 publications

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Section: Discussioncontrasting

confidence: 43%

“…Cytochalasin A is chemically similar to the thiol-alkylating agent N-ethylmaleimide (NEM) and has secondary effects on cell metabolism and thiol alkylation in mammalian cells that are unrelated to effects on actin (18,32,35). In this study, unlike studies with mammalian cells in which NEM did not interfere with actin filaments (18), NEM did in fact interfere with actin polymerization in C. albicans (not shown). The differential effect of NEM on actin from C. albicans compared to mammalian cells points to an intrinsic difference in sensitivity to oxidation between the two actins in their respective environments that may reflect the observation by us and others (32) that yeast and fungi are sensitive to cytochalasin A but not to cytochalasin B.…”

Section: Discussioncontrasting

confidence: 43%

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Role of Actin Cytoskeletal Dynamics in Activation of the Cyclic AMP Pathway and HWP1 Gene Expression in Candida albicans

Wolyniak

Sundstrom

2007

Eukaryot Cell

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Changes in gene expression during reversible bud-hypha transitions of the opportunistic fungal pathogen Candida albicans permit adaptation to environmental conditions that are critical for proliferation in host tissues. Our previous work has shown that the hypha-specific adhesin gene HWP1 is up-regulated by the cyclic AMP (cAMP) signaling pathway. However, little is known about the potential influences of determinants of cell morphology on HWP1 gene expression. We found that blocking hypha formation with cytochalasin A, which destabilizes actin filaments, and with latrunculin A, which sequesters actin monomers, led to a loss of HWP1 gene expression. In contrast, high levels of HWP1 gene expression were observed when the F-actin stabilizer jasplakinolide was used to block hypha formation, suggesting that HWP1 expression could be regulated by actin structures. Mutants defective in formin-mediated nucleation of F-actin were reduced in HWP1 gene expression, providing genetic support for the importance of actin structures. Kinetic experiments with wildtype and actin-deficient cells revealed two distinct phases of HWP1 gene expression, with a slow, actinindependent phase preceding a fast, actin-dependent phase. Low levels of HWP1 gene expression that appeared to be independent of stabilized actin and cAMP signaling were detected using indirect immunofluorescence. A connection between actin structures and the cAMP signaling pathway was shown using hyper-and hypomorphic cAMP mutants, providing a possible mechanism for up-regulation of HWP1 gene expression by stabilized actin. The results reveal a new role for F-actin as a regulatory agent of hypha-specific gene expression at the bud-hypha transition.Candida albicans is an opportunistic fungal pathogen with a tropism for the gastrointestinal mucosa. The progression to candidiasis from the usual state of commensalism is prompted by changes in the immune status of the host that relay signals for proliferation and culminate in tissue invasion. Growth in host tissues is characterized by the presence of yeast, pseudohyphal, and hyphal morphologies in response to a number of environmental parameters within the host that may include temperature, pH, and nutrition (31,33,66) as well as other unknown factors. The different morphologies of C. albicans are accompanied by differences in gene expression patterns that are critical to the development of candidiasis. The mechanisms that mediate changes in gene expression in concert with changes in morphology are directly relevant to the regulation of virulence of C. albicans.The hypha-specific gene HWP1 (hyphal wall protein 1) is an attractive candidate for studying morphology-specific gene regulation since it is abundantly expressed in hyphal growth mode and is barely detectable in the yeast morphology (73, 74). Pseudohyphae vary in the level of HWP1 gene expression (71). HWP1 encodes a glycosylphosphatidylinositol-linked cell wall protein that serves as a transglutaminase substrate and enables C. albicans to form covalent attachments ...

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Section: Discussioncontrasting

confidence: 43%

Section: Discussioncontrasting

confidence: 43%

Role of Actin Cytoskeletal Dynamics in Activation of the Cyclic AMP Pathway and HWP1 Gene Expression in Candida albicans

Wolyniak

Sundstrom

2007

Eukaryot Cell

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“…Note, however, that F-actin binding of a second costimulation-related actin-binding protein, L-Plastin (30), is not reduced by CPH (data not shown). Moreover, the effects of CPH clearly differ from those of cytochalasins, well accepted inhibitors of actin polymerization (40,41). Thus, although in parallel experiments cytochalasins inhibited T cell proliferation, they did not reduce IL-2 production (data not shown).…”

Section: Discussionmentioning

confidence: 82%

Cofilin peptide homologs interfere with immunological synapse formation and T cell activation

Eibert

Lee

Pipkorn

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

106

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The formation of supramolecular activation clusters within the immunological synapse, crucial for sustained signaling and T lymphocyte activation, requires costimulation-dependent reorganization of the actin cytoskeleton. Here we have identified the actin-remodeling protein cofilin as a key player in this process. Cell-permeable peptides that block costimulation-induced cofilin͞ F-actin interactions in untransformed human T lymphocytes impair receptor capping and immunological synapse formation at the interface between T cells and antigen-presenting cells. As a consequence, T cell activation, as measured by cytokine production and proliferation, is inhibited.

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“…Cytochalasin B depolymerizes microfilaments, a process which has a number of effects that inhibit antigen uptake and processing (14,17,54). However, low concentrations of cytochalasin B enhance T-cell responses to mitogens such as ConA (17,24,47,51).…”

Section: Resultsmentioning

confidence: 99%

Phagocytosis and Protein Processing Are Required for Presentation ofCryptococcus neoformansMitogen to T Lymphocytes

Syme

Spurrell

Ling³

et al. 2000

Infect Immun

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In addition to eliciting antigen specific T-cell-mediated immunity, Cryptococcus neoformans possesses a mitogen (CnM) that activates naive T cells to proliferate. This mechanism of T-cell activation is accessory cell dependent and major histocompatibility complex unrestricted. CnM-induced T-cell proliferation correlates with internalization of the organism, suggesting that intracellular processing is required to liberate CnM prior to presentation to T cells. To determine whether phagocytosis and processing are required, various inhibitors of accessory cell uptake and processing were used. C. neoformans was observed within the accessory cells. Paraformaldehyde fixation of the accessory cell abrogated presentation of CnM to T cells, indicating that a dynamic accessory cell surface was required. A lysosomotropic agent abrogated the response to CnM but had no effect on a control stimulus that did not require processing. Both aspartic acid and cysteine protease inhibitors blocked effective processing of CnM, so that it was unable to stimulate T cells. Finally, an inhibitor of microfilament polymerization abrogated proliferation to CnM. These results indicate that the mitogenic activity of C. neoformans requires phagocytosis of the organism, lysosomal or endosomal processing, proteolytic activity, and microfilament polymerization and intracellular transport as a prerequisite for T-cell proliferation.Cryptococcus neoformans is a pathogenic yeast that causes one of the leading fatal mycoses in AIDS (9,12,18,38). This clinical observation, in addition to animal studies, has made it clear that T-cell-mediated immunity is of paramount importance in host defense against C. neoformans (1,7,15,19,20,22,28,31). T-cell immunity is antigen specific; however, we have recently shown that T cells are also capable of responding to C. neoformans by an alternate mechanism of activation (36). Specifically, when T cells from a previously unexposed individual are placed in culture with C. neoformans, the organism induces a mitogenic response. The mitogenic T-cell response is accessory cell (AC) dependent but not major histocompatibility complex restricted (36). Since the whole organism is capable of mediating this mitogenic effect, it raises questions about how the C. neoformans mitogen (CnM) might be liberated or displayed prior to T-cell activation.We had previously shown that CnM was confined to the cell wall of the organism (32). Since CnM may be displayed on the cell wall, it is possible that it cross-links surface molecules on the T cell and AC analogous to superantigens. Alternately, the AC might produce an enzyme that results in extracellular degradation and release of CnM, with liberation of the molecule into the surrounding milieu, where it exerts its mitogenic effect. Finally, we considered the possibility that the organism must be taken up by the AC and degraded internally, with subsequent presentation of CnM by the AC to the T cell. We have previously shown that lymphocyte proliferation in response to C. neoformans correlate...

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The inhibitory effects of N-ethylmaleimide, colchicine and cytochalasins on human T-cell functions

Cited by 26 publications

References 21 publications

Role of Actin Cytoskeletal Dynamics in Activation of the Cyclic AMP Pathway and HWP1 Gene Expression in Candida albicans

Role of Actin Cytoskeletal Dynamics in Activation of the Cyclic AMP Pathway and HWP1 Gene Expression in Candida albicans

Cofilin peptide homologs interfere with immunological synapse formation and T cell activation

Phagocytosis and Protein Processing Are Required for Presentation ofCryptococcus neoformansMitogen to T Lymphocytes

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