Eukaryotic Cell (Eukaryot Cell )

Publisher: American Society for Microbiology, American Society for Microbiology

Journal description

Eukaryotic Cell (EC) focuses on eukaryotic microbiology and presents reports of basic research on simple eukaryotic microorganisms such as yeasts, fungi, algae, protozoa, and social amoebae. The journal also covers viruses of these organisms and their organelles and their interactions with other living systems, where the focus is on the eukaryotic cell.

Current impact factor: 3.18

Impact Factor Rankings

2015 Impact Factor Available summer 2015
2013 / 2014 Impact Factor 3.179
2012 Impact Factor 3.586
2011 Impact Factor 3.604
2010 Impact Factor 3.395
2009 Impact Factor 3.806
2008 Impact Factor 3.83

Impact factor over time

Impact factor
Year

Additional details

5-year impact 3.77
Cited half-life 5.40
Immediacy index 0.65
Eigenfactor 0.02
Article influence 1.32
Website Eukaryotic Cell website
Other titles Eukaryotic cell (Online), Eukaryotic cell
ISSN 1535-9786
OCLC 47259667
Material type Document, Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

Publisher details

American Society for Microbiology

  • Pre-print
    • Author cannot archive a pre-print version
  • Post-print
    • Author can archive a post-print version
  • Conditions
    • Cannot archive before publication
    • Author's version
    • Author's post-print on funder's repositories, institutional repository or subject-based repositories
    • Non-commercial
    • Publisher's version/PDF may be used
    • Publisher's version/PDF may be used on author's personal website or employers website
    • Recommended that author's post-prints submitted to PubMed or institutional repositories are made available 6 months after publication
    • Reviewed on 30th June 2014
  • Classification
    ​ blue

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Reversible phosphorylation of the phospholipid phosphatidylinositol (PI) is a key event in the determination of organelle identity and an underlying regulatory feature in many biological processes. Here, we investigate the role of PI signaling in the regulation of the mitogen activated protein kinase (MAPK) pathway that controls filamentous growth in yeast. Lipid kinases that generate PI (4)P at the Golgi (Pik1p) or PI(4,5)P2 at the plasma membrane (PM, Mss4p and Stt4p), were required for filamentous growth MAPK pathway signaling. Introduction of a conditional allele of PIK1 (pik1-83) into the filamentous (Σ1278b) background reduced MAPK activity and caused defects in invasive growth and biofilm/mat formation. MAPK regulatory proteins that function at the PM, including Msb2p, Sho1p, and Cdc42p, were mis-localized in the pik1-83 mutant, which may account for the signaling defects of the PI (4)P kinase mutants. Other PI kinases (Fab1p and Vps34p), and combinations of PIP (synaptojanin-type) phosphatases, also influenced the filamentous growth MAPK pathway. Loss of these proteins caused defects in cell polarity, which may underlie the MAPK signaling defect seen in these mutants. In line with this possibility, disruption of the actin cytoskeleton by Latrunculin A (LatA) dampened the filamentous growth pathway. Various PIP signaling mutants were also defective for axial budding in haploid cells, cell wall construction, or proper regulation of the high osmolarity glycerol response (HOG) pathway. Altogether, the study extends the roles of PI signaling to a differentiation MAPK pathway and other cellular processes. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: ATP-binding cassette transporters Pdr5 and Yor1 from Saccharomyces cerevisiae control the asymmetric distribution of phospholipids across the plasma membrane as well as serving as ATP-dependent drug efflux pumps. Mutant strains lacking these transporter proteins were found to exhibit very different resistant phenotypes to two inhibitors of sphingolipid biosynthesis that act either late (aureobasidin A:AbA) or early (myriocin: Myr) in the pathway leading to production of these important plasma membrane lipids. These pdr5Δ yor1 strains were highly AbA resistant but extremely sensitive to Myr. We provide evidence that these phenotypic changes are likely due to modulation of the plasma membrane flippase complexes: Dnf1/Lem3 and Dnf2/Lem3. Flippases act to move phospholipids from the outer to the inner leaflet of the plasma membrane. Genetic analyses indicate that lem3Δ mutant strains are highly AbA sensitive and Myr resistant. These phenotypes are fully epistatic to those seen in pdr5Δ yor1 strains. Direct analysis of AbA-induced signaling demonstrated that loss of Pdr5 and Yor1 inhibited the AbA-triggered phosphorylation of the AGC kinase Ypk1 and its substrate Orm1. Microarray experiments found that a pdr5Δ yor1 strain induced a Pdr1-dependent induction of the entire Pdr regulon. Our data support the view that Pdr5/Yor1 negatively regulate flippase function and activity of the nuclear Pdr1 transcription factor. Together, these data argue that the interaction of the ABC transporters Pdr5 and Yor1 with the Lem3-dependent flippases regulate permeability of AbA via control of plasma membrane protein function as seen for the high-affinity tryptophan permease Tat2. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: Hemoglobin degradation during the asexual cycle of Plasmodium falciparum is an obligate process for parasite development and survival. It is established that hemoglobin is transported from the host erythrocyte to the parasite digestive vacuole (DV), but this biological process is not well characterized. Three-dimensional reconstructions made from serial, thin-section, electron micrographs of untreated, trophozoite stage P. falciparum infected erythrocytes (IRBC) or IRBC treated with different pharmacological agents provide new insight into the organization and regulation of the hemoglobin transport pathway. Hemoglobin internalization commences with the formation of cytostomes from localized, electron-dense collars at the interface of the parasite plasma- and parasitophorous vacuolar- membranes. The cytostomal collar does not function as a site of vesicle fission, but rather serves to stabilize the maturing cytostome. We provide the first evidence that hemoglobin transport to the DV utilizes an actin-myosin motor system. Short-lived, hemoglobin-filled vesicles form from the distal end of the cytostomes, through actin and dynamin-mediated processes. Results from IRBC treated with N-ethylmaleimide (NEM) suggest that fusion of hemoglobin containing vesicles with the DV may involve a SNARE- dependent mechanism. In this investigation, we identify new key components of the hemoglobin transport pathway and provide a detailed characterization of its morphological organization and regulation. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: Certain Saccharomyces cerevisiae strains secrete different killer proteins of double-stranded RNA origin. These proteins confer a growth advantage to their host by increasing its survival. K2 toxin affects the target cell by binding to the cell surface, disrupting the plasma membrane integrity, and inducing ion leakage. In this study, we have determined that K2 toxin saturates the yeast cell surface receptors in 10 minutes. The apparent amount of K2 toxin, bound to a single cell of wild type yeast under saturating conditions, was estimated to be 435-460 molecules. It was found that increased level of β-1,6-glucan directly correlates with the number of toxin molecules bound, thereby impacting the morphology and determining the fate of the yeast cell. We observed that the binding of K2 toxin to the yeast surface receptors proceeds in a similar manner as in case of the related K1 killer protein. It was demonstrated that the externally supplied pustulan, a poly-β-1,6-glucan, but not the glucans bearing other linkage types (such as laminarin, chitin, and pullulan) efficiently inhibits the K2 toxin killing activity. In addition, the analysis of toxin binding to the intact cells and spheroplasts confirmed that majority of K2 protein molecules attach to the β-1,6-glucan, when compared to the plasma membrane-localized receptors. Taken together, our results revealed that β-1,6-glucan is a primary target of K2 toxin and is important for the execution of its killing property. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: Two-component signaling pathways generally include sensor histidine kinases and response regulators. We identified an ortholog of the response regulator protein Skn7, which we named it MrSkn7, in the insect pathogenic fungus Metarhizium robertsii. Gene deletion assays and functional characterizations indicated that MrSkn7 functions as a transcription factor. MrSkn7 null mutant of M. robertsii lost the ability to sporulate and had defects in cell wall biosynthesis but was not sensitive to oxidative and osmotic stresses when compared to the wild type. However, the mutant was able to produce spores under salt stress. Insect bioassays using these spores showed that the mutant virulence was significantly impaired when compared to the wild type due to the failures to form the infection structure appressorium and evade host immunity. In particular, deletion of MrSkn7 triggered cell autolysis with typical features such as cell vacuolization, down-regulation of repressor genes, and up-regulation of autolysis-related genes such as extracellular chitinases and proteases. Promoter binding assays confirmed that MrSkn7 could directly or indirectly control different putative target genes. Taken together, the results of this study help us understand the functional divergence of Skn7 orthologs as well as the mechanisms underlying the development and control of virulence in insect pathogenic fungi. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: The endoplasmic reticulum responds to errors in protein folding or processing by induction of the unfolded protein response (UPR). During conditions of ER stress, unconventional splicing of an mRNA encoding the UPR-responsive transcription factor occurs at the ER surface resulting in activation of the UPR. UPR activation is necessary for adaptation to ER stress, and for the pathogenic fungus Cryptococcus neoformans, is an absolute requirement for temperature adaptation and virulence. In this study, we have determined that C. neoformans has co-opted a conserved PUF RNA binding protein to regulate the post-transcriptional processing of the mRNA encoding the UPR transcription factor, HXL1. PUF elements were identified in both the 5' and 3' untranslated regions of the HXL1 transcript and both elements bound Puf4. Deletion of PUF4 resulted in delayed unconventional splicing of HXL1 mRNA and delayed induction of Hxl1 target genes. In addition, the HXL1 transcript was stabilized in the absence of Puf4. The puf4Δ mutant exhibited temperature sensitivity, but was as virulent as the wild type despite a reduction in fungal burden in the brains of infected mice. Our results reveal a novel regulatory role in which a PUF protein influences the unconventional splicing of the mRNA encoding the UPR-responsive transcription factor. These data suggest a unique role for a PUF protein in controlling UPR kinetics via the post-transcriptional regulation of the mRNA encoding the UPR transcription factor, Hxl1. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: Alternaria species are mainly saprophytic fungi but some are plant pathogens. Seven pathotypes of Alternaria alternata use secondary metabolites of host-specific toxins as pathogenicity factors. These toxins kill host cells prior to colonization. Genes associated with toxin synthesis reside on conditionally dispensable chromosomes, supporting the notion that pathogenicity might have been acquired several times by A. alternata. Alternaria brassicicola, however, seems to employ a different mechanism. Evidence on the use of host-specific toxins as pathogenicity factors remains tenuous, even after a diligent search aided by full genome sequencing and efficient reverse genetics approaches. Similarly, no individual genes encoding lipases or cell wall-degrading enzymes have been identified as strong virulence factors although these enzymes have been considered important for fungal pathogenesis. This review describes our current understanding of toxins, lipases, and cell wall-degrading enzymes and their roles in the pathogenesis of A. brassicicola, as compared to other pathogenic fungi. It also describes a set of genes that affect pathogenesis in A. brassicicola. They are involved in various cellular functions that are likely important in most organisms and probably indirectly associated with pathogenesis. Mutants of these genes are weakly virulent and appear to be sensitive to the defense mechanisms of host plants. Finally, this review discusses the implications of a recent discovery of three important transcription factors associated with pathogenesis and the putative downstream genes they regulate. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: Malaria parasites replicating inside RBCs export a large subset of proteins into the erythrocyte cytoplasm to facilitate parasite growth and survival. PTEX, the parasite encoded translocon, mediates protein transport across the parasitophorous vacuolar membrane (PVM) in Plasmodium falciparum infected erythrocytes. Proteins exported into the erythrocyte cytoplasm have been localized to membranous structures such as Maurer's clefts, small vesicles and a tubovesicular network. Comparable studies of protein trafficking in Plasmodium vivax infected reticulocytes are limited. With Plasmodium yoelii infected reticulocytes, we identified exported protein 2 (Exp2) in a proteomic screen of proteins putatively transported across the PVM. Immunofluorescence studies showed that PyExp2 was primarily localized to the PVM. Unexpectedly, PyExp2 was also associated with distinct, membrane-bound vesicles in the reticulocyte cytoplasm. This is in contrast to P. falciparum in mature RBCs where PfExp2 is exclusively localized to the PVM. Two P. yoelii exported proteins, PY04481 (pyst-a) and PY06203 (PypAg-1) partially co-localized with these PyExp2 positive vesicles. Further analysis revealed that with P. yoelii, P. berghei and P. falciparum, cytoplasmic Exp2 positive vesicles were primarily observed in CD71(+) reticulocytes versus mature RBCs. In transgenic P. yoelii 17X parasites, the association of hemagglutinin-tagged PyExp2 with the PVM and cytoplasmic vesicles was retained but the pyexp2 gene was refractory to deletion. These data suggest that the localization of Exp2 in mouse and human RBCs can be influenced by the host cell environment. Exp2 may function at multiple points in the pathway by which parasites traffic proteins into and through the reticulocyte cytoplasm. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 02/2015;
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    ABSTRACT: Candida albicans adapts to the human host by environmental sensing using the Msb2 signal mucin that regulates fungal morphogenesis and resistance characteristics. Msb2 is anchored within the cytoplasmic membrane by a single transmembrane (TM) region dividing it into a large N-terminal exodomain, which is shed, and a small cytoplasmic domain. Analyses of strains carrying deleted Msb2 variants revealed an exodomain segment required for cleavage, shedding and all functions of Msb2. Phosphorylation of the MAP kinase Cek1 was regulated by three distinct regions in Msb2: in unstressed cells, N-terminal sequences repressed phosphorylation, while its induction under cell wall stress required the cytoplasmic tail and sequences N-terminally flanking the TM region, downstream of the proposed cleavage site. Within the latter Msb2 region, overlapping but not identical sequences were also required for hyphal morphogenesis, basal resistance to antifungals and, in unstressed cells, downregulation of the PMT1 transcript encoding protein O-mannosyltransferase-1. Deletion of two-thirds of the exodomain generated a truncated Msb2 variant with a striking ability to induce hyperfilamentous growth, which depended on the presence of the Msb2 interacting protein Sho1, on MAP kinase Cek1 and the Efg1 transcription factor. Under cell wall stress, the cytoplasmic tail relocalized partially to the nucleus and contributed to regulation of 117 genes as revealed by transcriptomal analyses. Genes regulated by the C-tail contained binding sites for the Ace2 and Azf1 transcription factors and included MSB2 and ALS cell wall genes. It is concluded that Msb2 fulfills its numerous functions by employing functional domains that are distributed over its entire length. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: In recent years, the emergence of fungal resistance has become frequent partly due to the widespread clinical use of fluconazole, which is minimally toxic and effective in prevention and treatment of Candida albicans infections. The limited selection of antifungal drugs for clinical fungal infection therapy has prompted us to search for new antifungal targets that can be targeted by new antifungal drugs. Calcium, which acts as the second messenger in both mammals and fungi, plays a direct role in controlling the expression patterns of its signaling systems and important roles in cell survival. In addition, calcium and some of the components, mainly calcineurin, in the fungal calcium signaling pathway mediate fungal resistance to antifungal drugs. Therefore, an overview of the components of the fungal calcium-calcineurin signaling network, and their potential roles as antifungal targets is urgently needed. The calcium-calcineurin signaling pathway consists of various channels, transporters, pumps and other proteins or enzymes. Many transcriptional profiles have indicated that mutant strains that lack some of these components are sensitized to fluconazole or other antifungal drugs. In addition, many researchers have identified efficient compounds that exhibit antifungal activity by themselves or in combination with antifungal drugs by targeting some of the components in the fungal calcium-calcineurin signaling pathway. This targeting disrupts Ca(2+) homeostasis, which suggests that this pathway contains potential antifungal targets for the development of new antifungal drugs. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: The highly conserved ADP/ATP carrier (AAC) is a key energetic link between the mitochondrial (mt) and cytosolic compartments of all aerobic eukaryotic cells, as it exchanges the ATP generated inside the organelle for the cytosolic ADP. Trypanosoma brucei, a parasitic protist of medical and veterinary importance, possesses a single functional TbAAC protein that is related to the human and yeast ADP/ATP carriers. However, unlike previous studies performed with these model organisms, it appears that TbAAC is most likely not a stable component of either the respiratory supercomplex III+IV or the ATP synthasome, but rather functions as a physically separate entity in this highly diverged eukaryote. Therefore, TbAAC RNAi ablation in the insect stage of T. brucei does not impair the activity or arrangement of the respiratory chain complexes. Nevertheless, RNAi silencing of TbAAC caused a severe growth defect that coincides with a significant reduction of mt ATP synthesis by both substrate and oxidative phosphorylation. Furthermore, TbAAC down-regulation resulted in a decreased level of cytosolic ATP, a higher mt membrane potential, an elevated amount of reactive oxygen species and a reduced consumption of oxygen in the mitochondria. Interestingly, while TbAAC has previously been demonstrated to serve as the sole ADP/ATP carrier for ADP influx into the mitochondria, our data suggests a second carrier for ATP influx may be present and active in the T. brucei mitochondrion. Overall, this study provides more insight into the delicate balance of the functional relationship between TbAAC and the OXPHOS pathway in an early diverged eukaryote. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: The molecular mechanisms of membrane merger during somatic cell fusion in eukaryotic species are poorly understood. In the filamentous fungus Neurospora crassa, somatic cell fusion occurs between genetically identical germinated asexual spores (germlings) and between hyphae to form the interconnected network characteristic of a filamentous fungal colony. In N. crassa, two proteins have been identified to function at the step of membrane fusion during somatic cell fusion: PRM1 and LFD-1. The absence of either one of these two proteins results in an increase of germling pairs arrested during cell fusion with tightly appressed plasma membranes and an increase in the frequency of cell lysis of adhered germlings. The level of cell lysis in ΔPrm1 or Δlfd-1 germlings is dependent on the extracellular calcium concentration. An available transcriptional profile dataset was used to identify genes encoding predicted transmembrane proteins that showed reduced expression levels in germlings cultured in the absence of extracellular calcium. From these analyses, we identified a mutant (late fusion defect-2) that showed a calcium-dependent cell lysis phenotype. lfd-2 encodes a protein with a Fringe domain and showed ER and Golgi localization. Deletion of an additional gene predicted to encode a low affinity calcium transporter gene, fig 1, also resulted in a strain that showed a calcium-dependent cell lysis phenotype. Genetic analyses showed that LFD-2 and FIG 1 likely function in separate pathways to regulate aspects of membrane merger and repair during cell fusion. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: We identified genes encoding components of the Hap complex, CbHAP2, CbHAP3, and CbHAP5 as transcription factors regulating methanol-inducible gene expression in the methylotrophic yeast Candida boidinii. We found that gene disrupted strains, Cbhap2Δ, Cbhap3Δ, and Cbhap5Δ, showed severe growth defects on methanol but not on glucose and nonfermentable carbon sources such as ethanol and glycerol. In these disruptants, transcriptional activities of methanol-inducible promoters significantly decreased compared to the wild-type strain, indicating that CbHap2p, CbHap3p, and CbHap5p play indispensable roles in methanol-inducible gene expression. Further molecular and biochemical analysis demonstrated that CbHap2p, CbHap3p, and CbHap5p localized to the nucleus and bound to the promoter regions of methanol-inducible genes regardless of the carbon source, and heterotrimer formation was suggested to be necessary for binding to DNA. Unexpectedly, distinct from Saccharomyces cerevisiae, the Hap complex functioned in methanol-specific induction rather than glucose derepression in C. boidinii. Our results shed light on a novel function of the Hap complex in methanol-inducible gene expression in methylotrophic yeasts. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: Trypanosoma brucei, a parasitic protozoon that causes African trypanosomiasis, possesses a single member of the presequence and amino acid transporter (PRAT) protein family, which is referred to as TbTim17. In contrast, three homologous proteins, Tim23, Tim17, and Tim22 are found in Saccharomyces cerevisiae and higher eukaryotes. Here, we show that TbTim17 cannot rescue Tim17, Tim23, or Tim22 mutants of S. cerevisiae. We expressed S. cerevisiae Tim23, Tim17, and Tim22 in T. brucei. These heterologous proteins were properly imported into mitochondria in the parasite. Further analysis revealed that although ScTim23 and ScTim17 were integrated into the mitochondrial inner membrane and assembled into a protein complex similar in size to TbTim17, only ScTim17 was stably associated with TbTim17. In contrast, ScTim22 existed as a protease-sensitive soluble protein in T. brucei mitochondrion. In addition, the growth defect caused by TbTim17 knockdown in T. brucei was partially restored by the expression of ScTim17, but not by the expression of either ScTim23 or ScTim22. Whereas, expression of TbTim17 fully complemented the growth defect caused by TbTim17 knockdown, as anticipated. Similar to cell growth, the defect in the import of mitochondrial proteins due to depletion of TbTim17 was in part restored by the expression of ScTim17 but was not complemented by the expression of either ScTim23 or ScTim22. Together, these results suggest that TbTim17 is divergent compared to ScTim23 but closer in function to ScTim17. In addition, ScTim22 couldn't be sorted properly in T. brucei mitochondrion, thus failed to complement the function of TbTim17. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: The anillin-related protein Bud4 of Saccharomyces cerevisiae is required for axial bud-site selection by linking the axial landmark to the septins, which localize at the mother-bud neck. Recent studies indicate that Bud4 plays a role in septin organization during cytokinesis. Here we show that Bud4 is also involved in septin organization during bud growth prior to cytokinesis, as bud4Δ shs1Δ cells displayed an elongated-bud morphology and defective septin organization at 18°C. Bud4 overexpression also affected septin organization during bud growth in shs1Δ cells at 30°C. Bud4 is previously thought to associate with the septins via its central region while the C-terminal anillin-related region is not involved in septin association. Surprisingly, we found that the central region of Bud4 alone targets to the bud neck throughout the cell cycle, unlike full-length Bud4, which only localizes to the bud neck during G2/M. We identified the anillin-related region as a second targeting domain that cooperates with the central region for proper septin association. In addition, the anillin-related region could largely mediate Bud4's function in septin organization during bud growth and bud-site selection. We show that this region interacts with the C-terminus of Bud3 and the two segments depend on each other for association with the septins. Moreover, bud3Δ genetically interacts with shs1Δ and cdc12-6 mutants in septin organization similar to bud4Δ, suggesting that Bud4 and Bud3 may cooperate for septin organization during bud growth. These observations provide new insights on the interaction of Bud4 with the septins and Bud3. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: Human-infecting microbial pathogens all face a serious problem of elimination by the host immune response. Antigenic variation is an effective immune evasion mechanism, where the pathogen regularly switches its major surface antigen. In many cases, the major surface antigen is encoded by genes from the same gene family and its expression is strictly monoallelic. Among pathogens that undergo antigenic variation, Trypanosoma brucei (a Kinetoplastid) that causes human African trypanosomiasis, Plasmodium falciparum (an Apicomplexan) that causes malaria, Pneumocystis jirovecii (a fungus) that causes pneumonia, and Borrelia burgdorferi (a bacterium) that causes Lyme disease also express their major surface antigens from loci next to the telomere. Except for Plasmodium, DNA recombination-mediated gene conversion is a major pathway for surface antigen switching in these pathogens. In the last decade, more sophisticated molecular and genetic tools have been developed in T. brucei, and our knowledge of functions of DNA recombination in antigenic variation has been greatly advanced. VSG is the major surface antigen in T. brucei. In subtelomeric VSG expression sites (ESs), VSG genes are invariably flanked by long stretch of upstream 70 bp repeats. Recent studies have shown that DNA double-strand breaks (DSBs), particularly those in 70 bp repeats in the active ES, are a natural potent trigger for antigenic variation in T. brucei. In addition, telomere proteins can influence VSG switching by reducing the DSB amount at subtelomeric regions. These findings will be summarized and their implications will be discussed in this review. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Eukaryotic Cell 01/2015;
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    ABSTRACT: Sarcolemmal membrane-associated protein (SLMAP) is a tail-anchored protein involved in fundamental cellular processes such as myoblast fusion, cell cycle progression, and chromosomal inheritance. Further, SLMAP mis-expression is associated with endothelial dysfunctions in diabetes and cancer. SLMAP is part of the conserved striatin-interacting phosphatase and kinase (STRIPAK) complex required for specific signaling pathways in yeasts, filamentous fungi, insects, and mammals. In filamentous fungi, STRIPAK was initially discovered in Sordaria macrospora – a model system for fungal differentiation. Here, we functionally characterize the STRIPAK subunit PRO45, a homolog of human SLMAP. We show that PRO45 is required for sexual propagation and cell-to-cell fusion, and that its forkhead-associated (FHA) domain is essential for these processes. Protein-protein interaction studies revealed that PRO45 binds to STRIPAK subunits PRO11 and SmMOB3, which are also required for sexual propagation. Super-resolution structured-illumination microscopy (SIM) further established that PRO45 localizes to the nuclear envelope, ER, and mitochondria. SIM also showed that localization to the nuclear envelope required STRIPAK subunits PRO11 and PRO22, whereas for mitochondria it did not. Taken together, our study provides important insights into fundamental roles of the fungal SLMAP homolog PRO45 and suggests STRIPAK-related and STRIPAK-unrelated functions.
    Eukaryotic Cell 12/2014;
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    ABSTRACT: Toxoplasma gondii is an obligate intracellular parasite that causes serious opportunistic infections, birth defects and blindness in humans. Microtubules are critically important components of diverse structures that are used throughout the Toxoplasma life cycle. As in other eukaryotes, spindle microtubules are required for chromosome segregation during replication. Additionally, a set of membrane-associated microtubules is essential for the elongated shape of invasive zoites and motility follows a spiral trajectory that reflects the path of these microtubules. Toxoplasma zoites also construct an intricate, tubulin-based apical structure termed the conoid which is important for host cell invasion and associates with proteins typically found in the flagellar apparatus. Lastly, microgametes specifically construct a microtubule-containing flagellar axoneme in order to fertilize macrogametes, permitting genetic recombination. The specialized roles of these microtubule populations are mediated by distinct sets of associated proteins. This review summarizes our current understanding of the role of tubulin, microtubule populations, and associated proteins in Toxoplasma; these components are used for both novel and broadly conserved processes that are essential for parasite survival.
    Eukaryotic Cell 11/2014;