Microtubules and actin cytoskeleton in Cryptococcus neoformans compared with ascomycetous budding and fission yeasts

Kopecká, Marie; Gabriel, Miroslav; Takeo, Kanji; Yamaguchi, Masashi; Svoboda, Augustín; Ohkusu, Misako; Hata, Kunihiko; Yoshida, Soichi

doi:10.1078/0171-9335-00157

Cited by 47 publications

(65 citation statements)

References 43 publications

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“…Furthermore, consistent with the idea that in U. maydis high levels of Clb1 interfere with microtubule assembly, we showed that overexpression of clb1 resulted in cells that were hypersensitive to the microtubule inhibitor benomyl and had anomalous DNA content. A general feature observed in basidiomycete yeast is the presence of an extensive microtubule network in G2 that disassembles prior to mitosis and then forms the mitotic spindle (Steinberg et al, 2001;Kopecká et al, 2001;Banuett and Herskowitz, 2002). We entertained the idea that an initial step to enter in mitosis could be the premitotic activation of Cdk1-Clb1 that could induce the disassembly of the cytoplasmic microtubule network.…”

Section: Discussionmentioning

confidence: 99%

Characterization of B-type cyclins in the smut fungusUstilago maydis: roles in morphogenesis and pathogenicity

García‐Muse

Steinberg

Pérez-Martı́n

2004

Journal of Cell Science

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Pathogenesis, morphogenesis and cell cycle are connected in the fungal pathogen Ustilago maydis. Here we report the characterization of the catalytic subunit of the cyclin-dependent kinase, encoded by the gene cdk1, and the two B-type cyclins present in this organism, encoded by the genes clb1 and clb2. These cyclins are not redundant and appears to be essential for cell cycle. The analysis of conditional mutants in cyclin genes indicates that Clb1 is required for G1 to S and G2 to M transitions, while Clb2 is specifically required for the onset of mitosis. Both Clb1 and Clb2 carry functional destruction boxes, and expression of derivatives lacking D-boxes arrested cell cycle at a post-replicative stage. High levels of Clb1 generated cells with anomalous DNA content that were hypersensitive to microtubule-destabilizing drugs. In contrast, high levels of Clb2 induce premature entry into mitosis, suggesting that Clb2 is a mitotic inducer in U. maydis. In addition, Clb2 affects morphogenesis, and overexpression of clb2 induces filamentous growth. Furthermore, we have found that appropriate levels of Clb2 cyclin are critical for a successful infection. Mutant strains with half a dose of clb2 or high level of clb2 expression are impaired at distinct stages in the infection process. These data reinforces the connections between cell cycle, morphogenesis and virulence in this smut fungus.

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Section: Discussionmentioning

confidence: 99%

Characterization of B-type cyclins in the smut fungusUstilago maydis: roles in morphogenesis and pathogenicity

García‐Muse

Steinberg

Pérez-Martı́n

2004

Journal of Cell Science

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“…Previous studies suggested that C. neoformans maintains actin dynamics similar to those of model yeasts (21,47). In wild-type strains, F-actin is present in polarized patches enriched in the early, emerging daughter cell and at the contractile ring ( Fig.…”

Section: Wsp1 Coresides With and Functions Downstream Of Cin1 In Endomentioning

confidence: 95%

Wsp1 Is Downstream of Cin1 and Regulates Vesicle Transport and Actin Cytoskeleton as an Effector of Cdc42 and Rac1 in Cryptococcus neoformans

et al. 2012

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ABSTRACTHuman Wiskott-Aldrich syndrome protein (WASP) is a scaffold linking upstream signals to the actin cytoskeleton. In response to intersectin ITSN1 and Rho GTPase Cdc42, WASP activates the Arp2/3 complex to promote actin polymerization. The human pathogenCryptococcus neoformanscontains the ITSN1 homolog Cin1 and the WASP homolog Wsp1, which share more homology with human proteins than those of other fungi. Here we demonstrate that Cin1, Cdc42/Rac1, and Wsp1 function in an effector pathway similar to that of mammalian models. In thecin1mutant, expression of the autoactivated Wsp1-B-GBD allele partially suppressed the mutant defect in endocytosis, and expression of the constitutively activeCDC42Q61Lallele restored normal actin cytoskeleton structures. Similar phenotypic suppression can be obtained by the expression of a Cdc42-green fluorescent protein (GFP)-Wsp1 fusion protein. In addition, Rac1, which was found to exhibit a role in early endocytosis, activates Wsp1 to regulate vacuole fusion. Rac1 interacted with Wsp1 and depended on Wsp1 for its vacuolar membrane localization. Expression of the Wsp1-B-GBD allele restored vacuolar membrane fusion in therac1mutant. Collectively, our studies suggest novel ways in which this pathogenic fungus has adapted conserved signaling pathways to control vesicle transport and actin organization, likely benefiting survival within infected hosts.

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“…Attempts have been made to visualize yeast actin filaments by thinsection electron microscopy (Adams and Pringle, 1984;Mulholland et al, 1994). However, actin filaments do not show up well in the crowded yeast cytoplasm, except for rare actin cables in Saccharomyces cerevisiae and pathogenic yeasts (Adams and Pringle, 1984;Kopecka et al, 2001;Yamaguchi et al, 2002), cytoplasmic "filasomes" distinct from cortical patches in fission yeast (Kanbe et al, 1989;Takagi et al, 2003), and aberrant filamentous actin structures in mutant budding yeast defective in endocytosis (Sekiya-Kawasaki et al, 2003). Immunolabeled thin sections have in some cases revealed finger-like invaginations of the plasma membrane apparently entwined in an actin helix (Mulholland et al, 1994).…”

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confidence: 99%

Actin and Septin Ultrastructures at the Budding Yeast Cell Cortex

Rodal

Kozubowski

Goode

et al. 2005

MBoC

174

162

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Budding yeast has been a powerful model organism for studies of the roles of actin in endocytosis and septins in cell division and in signaling. However, the depth of mechanistic understanding that can be obtained from such studies has been severely hindered by a lack of ultrastructural information about how actin and septins are organized at the cell cortex. To address this problem, we developed rapid-freeze and deep-etch techniques to image the yeast cell cortex in spheroplasted cells at high resolution. The cortical actin cytoskeleton assembles into conical or mound-like structures composed of short, cross-linked filaments. The Arp2/3 complex localizes near the apex of these structures, suggesting that actin patch assembly may be initiated from the apex. Mutants in cortical actin patch components with defined defects in endocytosis disrupted different stages of cortical actin patch assembly. Based on these results, we propose a model for actin function during endocytosis. In addition to actin structures, we found that septin-containing filaments assemble into two kinds of higher order structures at the cell cortex: rings and ordered gauzes. These images provide the first high-resolution views of septin organization in cells. INTRODUCTIONBudding yeast has been used for over 20 yr as a model organism to study cytoskeletal function because the genes encoding many components of the cytoskeleton are conserved and because yeast cells are readily amenable to parallel genetic, biochemical, and cell biological analyses. Despite rapid advances in defining the components of the yeast cytoskeleton, its ultrastructure has been difficult to image at the resolution of the electron microscope, with the exception of microtubules (O'Toole et al., 1999). This may be due to the low abundance of the cytoskeleton in yeast relative to mammalian cells, to the presence of a cell wall that complicates extraction procedures, and to high ribosome density in the yeast cytoplasm. As a result, there has been a conspicuous deficit in our understanding of the higher order organization of actin and septin polymers in vivo (Pruyne and Bretscher, 2000). Thus, although it is possible to rapidly identify and mutate cytoskeletal proteins in yeast, there is no method by which to examine the ultrastructural consequences of these mutations. This gap could be filled by developing an approach to image the yeast cytoskeleton at high resolution.The yeast actin cytoskeleton is organized into three distinct structures: motile cortical patches that are polarized in the growing bud, actin cables that run along the motherdaughter cell axis, and a contractile cytokinetic ring at the neck of dividing cells (reviewed in Pruyne and Bretscher, 2000). Cortical actin patches contain many of the actin-associated proteins common to all eukaryotes (Goode and Rodal, 2001) and are composed of actin filaments that undergo rapid turnover (Ayscough et al., 1997). Actin is essential for yeast endocytosis (Kubler and Riezman, 1993). A number of recent studies suggest that act...

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Microtubules and actin cytoskeleton in Cryptococcus neoformans compared with ascomycetous budding and fission yeasts

Cited by 47 publications

References 43 publications

Characterization of B-type cyclins in the smut fungusUstilago maydis: roles in morphogenesis and pathogenicity

Characterization of B-type cyclins in the smut fungusUstilago maydis: roles in morphogenesis and pathogenicity

Wsp1 Is Downstream of Cin1 and Regulates Vesicle Transport and Actin Cytoskeleton as an Effector of Cdc42 and Rac1 in Cryptococcus neoformans

Actin and Septin Ultrastructures at the Budding Yeast Cell Cortex

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