Cell Structure and Function
Online ISSN : 1347-3700
Print ISSN : 0386-7196
ISSN-L : 0386-7196
Volume 28 , Issue 5
Showing 1-9 articles out of 9 articles from the selected issue
PREFACE
REVIEW
  • Kaoru Takegawa, Tomoko Iwaki, Yasuko Fujita, Tomotake Morita, Akira Ho ...
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 399-417
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    The vacuole of Saccharomyces cerevisiae plays essential roles not only for osmoregulation and ion homeostasis but also down-regulation (degradation) of cell surface proteins and protein and organellar turnover. Genetic selections and genome-wide screens in S. cerevisiae have resulted in the identification of a large number of genes required for delivery of proteins to the vacuole. Although the complete genome sequence of the fission yeast Schizosaccharomyces pombe has been reported, there have been few reports on the proteins required for vacuolar protein transport and vacuolar biogenesis in S. pombe. Recent progress in the S. pombe genome project of has revealed that most of the genes required for vacuolar biogenesis and protein transport are conserved between S. pombe and S. cerevisiae. This suggests that the basic machinery of vesicle-mediated protein delivery to the vacuole is conserved between the two yeasts. Identification and characterization of the fission yeast counterparts of the budding yeast Vps and Vps-related proteins have facilitated our understanding of protein transport pathways to the vacuole in S. pombe. This review focuses on the recent advances in vesicle-mediated protein transport to the vacuole in S. pombe.
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  • Fubito Nakatsu, Hiroshi Ohno
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 419-429
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    Adaptor protein (AP) complexes are cytosolic heterotetramers that mediate the sorting of membrane proteins in the secretory and endocytic pathways. AP complexes are involved in the formation of clathrin-coated vesicles (CCVs) by recruiting the scaffold protein, clathrin. AP complexes also play a pivotal role in the cargo selection by recognizing the sorting signals within the cytoplasmic tail of integral membrane proteins. Six distinct AP complexes have been identified. AP-2 mediates endocytosis from the plasma membrane, while AP-1, AP-3 and AP-4 play a role in the endosomal/lysosomal sorting pathways. Moreover, tissue-specific sorting events such as the basolateral sorting in polarized epithelial cells and the biogenesis of specialized organelles including melanosomes and synaptic vesicles are also regulated by members of AP complexes. The application of a variety of methodologies have gradually revealed the physiological role of AP complexes.
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  • Kazuhisa Nakayama, Soichi Wakatsuki
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 431-442
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    GGAs (Golgi-localizing, γ-adaptin ear homology domain, ARF-binding proteins) are a family of monomeric clathrin adaptor proteins that are conserved from yeasts to humans. Data published during the past four years have provided detailed pictures of the localization, domain organization and structure-function relationships of GGAs. GGAs possess four conserved functional domains, each of which interacts with cargo proteins including mannose 6-phosphate receptors, the small GTPase ARF, clathrin, or accessory proteins including Rabaptin-5 and γ-synergin. Together with or independent of the adaptor protein complex AP-1, GGAs regulate selective transport of cargo proteins, such as mannose 6-phosphate receptors, from the trans-Golgi network to endosomes mediated by clathrin-coated vesicles.
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  • Kyohei Umebayashi
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 443-453
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    After cell surface receptors are internalized for endocytosis, they are accurately sorted in endosomes. Some are recycled to the plasma membrane and others are downregulated by delivery to lysosomes. Evidence is rapidly accumulating that ubiquitination of cargo proteins acts as a sorting signal during endocytosis. Sorting devices that recognize ubiquitin are distributed to various compartments, probably acting in a concerted manner. Cholesterol is enriched in the plasma membrane and endosomes, and is involved in protein sorting by forming microdomains called lipid rafts. Ubiquitin and cholesterol hold the key to control the endocytic sorting, and they are likely acting cooperatively.
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  • Ge-Hong Sun-Wada, Yoh Wada, Masamitsu Futai
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 455-463
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    Mammals contain various cells differentiated in both morphology and function, which play vital roles in tissue-specific functions. Late endosome/lysosome and lysosomal-related organelles are involved in these specialized functions including antigen presentation, bone remodeling and hormone regulation. To fulfill these diverse roles, lysosomes are present at different levels in different tissues and cell types; however, their morphology within these different tissues varies and the regulation of their activities differs with lysosomal compartments in some cells also functioning as secretory compartments. The luminal acidification of these organelles is closely correlated with their functions. This review will discuss the functions of lysosomes and lysosomal-related organelles, with particular emphasis on the major proton pump, the vacuolar-type proton ATPase (V-ATPase), which is responsible for luminal acidification.
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  • Tetsuro Izumi, Hiroshi Gomi, Kazuo Kasai, Shin Mizutani, Seiji Torii
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 465-474
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    Regulated secretory pathways are highly developed in multicellular organisms as a means of intercellular communication. Each of these pathways harbors unique store organelles, such as granules in endocrine and exocrine tissues and melanosomes in melanocytes. It has recently been shown that the monomeric GTPase Rab27 subfamily regulates the exocytosis of these cell-specific store organelles. Furthermore, genetic alterations of Rab27a cause Griscelli syndrome in humans that manifests as pigmentary dilution of the skin and the hair and variable immunodeficiency due to defects in the transport of melanosomes in melanocytes and lytic granules in cytotoxic T-lymphocytes. Rab27 acts through organelle-specific effector proteins, such as granuphilin in pancreatic beta cells and melanophilin in melanocytes. The Rab27 and effector complex then interacts with proteins that are essential for membrane transport and fusion, such as syntaxin 1a and Munc18-1 for granuphilin and myosin Va for melanophilin. Genome information suggests that other putative Rab27 effector proteins, tentatively termed as exophilins or Slp/Slac2, are predicted to exist because these proteins share the conserved N-terminal Rab27-binding domain and show Rab27-binding activity in vitro or when overexpressed in cell lines. These findings suggest that the Rab27 subfamily regulates various exocytotic pathways using multiple organelle-specific effector proteins.
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REGULAR ARTICLES
  • Tadashi Tamura, Naoko Tsuruta, Kaori Hirano, Kenichi Yamaguchi, Tatsuy ...
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 475-485
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    We found that the treatment with 1 mM butyric acid for 2 days renders Vero cells highly sensitive to ricin-induced apoptosis reflected by cytolysis concomitant with apoptotic cellular and nuclear morphological changes, DNA fragmentation, and increase in caspase-3 like activity, whereas butyric acid alone had no cytotoxic effect on Vero cells. During the treatment with butyric acid, gradual increase in alkaline phosphatase activity, an indicator for butyric acid-induced differentiation, was observed in Vero cells. Although the potency of ricin-mediated protein synthesis was increased in butyric acid-treated Vero cells as compared to untreated cells, the binding and internalization of ricin to the cells were not much affected. Furthermore, DNA fragmentation caused by other protein synthesis inhibitors such as diphtheria toxin and anisomysin were also highly potentiated in butyric acid-treated Vero cells, whereas the potencies of these toxins to inhibit the protein synthesis were not affected by butyric acid treatment. These results suggest that the apoptosis signaling pathway, which may be triggered by cytotoxic stress response caused by toxins, is sensitized in butyric acid-treated cells, while the pathways leading to the protein synthesis inhibition by these toxins are relatively unchanged. No significant differences in the expression levels of p21, p53, and Bcl-2 proteins were observed between butyric acid-treated and untreated Vero cells. The treatment with ricin resulted in the activation of p38 MAP kinase, and this activation occurred on an accelerated time schedule in butyric acid-treated Vero cells than in untreated cells. The specific inhibitor of p38 MAP kinase SB203580 showed a partial inhibitory effect on ricin-induced apoptosis in control Vero cells, but it was less effective in butyric acid-treated Vero cells. Taken together, our results suggest that butyric acid-treatment may result in sensitization of multiple intracellular signal transduction pathways including apoptotic signaling pathways and p38 MAP kinase pathway.
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  • Yuko Inazawa, Masami Nakatsu, Etsuko Yasugi, Kumiko Saeki, Akira Yuo
    Type: scientific monograph
    Subject area: Cell Structure and Function
    2003 Volume 28 Issue 5 Pages 487-493
    Published: 2003
    Released: January 26, 2004
    JOURNALS FREE ACCESS
    All trans retinoic acid (ATRA), a differentiation inducer for human myeloid NB4 cells, induced accumulation of lipid droplet as determined by positivity of Nile Red and Oil Red O in this cell line. Granulocyte colony-stimulating factor (G-CSF), although not having detectable effect by itself, exerted the additive effects on lipid droplet formation in NB4 cells when combined with ATRA. mRNA analysis for peroxisome proliferator-activated receptors (PPARs) revealed the initial transient downregulation followed by upregulation of the transcript for PPARγ2, a master molecule for adipogenesis, and upregulation of PPARα. BADGE, a synthetic antagonist for PPARγ, potently inhibited lipid droplet formation in NB4 cells stimulated by ATRA and/or G-CSF, but not the functional differentiation of the cells by ATRA and/or G-CSF. These results suggest that ATRA and G-CSF induce lipid droplet formation via certain PPARγ-mediated specific mechanisms in human myeloid NB4 cells during functional differentiation.
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