scholarly journals A Role for Exocytosis in the Spatial Regulationof Actin Organization

2003 ◽  
Vol 3 ◽  
pp. 1359-1362 ◽  
Author(s):  
Xiang-Dong Gao ◽  
Stefan Albert
Keyword(s):  
Actin Cytoskeleton ◽  
Cellular Functions ◽  
Efficient Organization ◽  
Actin Organization ◽  
Spatial Regulation ◽  
A Cell ◽  
Yeast Mutants

The efficient organization of the actin cytoskeleton is important for many cellular functions. However, how the local actin organization is regulated in a cell is not well understood. By using yeast mutants defective in actin organization and secretion, we demonstrated that exocytosis plays a role in the spatial regulation of actin organization. Our findings suggest that the actin cytoskeleton, exocytosis, and perhaps endocytosis, may depend on each other for efficiency and reinforce each other.

scholarly journals F-Actin Cytoskeleton Network Self-Organization Through Competition and Cooperation

2020 ◽  
Vol 36 (1) ◽  
pp. 35-60
Author(s):  
Rachel S. Kadzik ◽  
Kaitlin E. Homa ◽  
David R. Kovar
Keyword(s):  
Actin Binding ◽  
Filamentous Actin ◽  
Cellular Functions ◽  
Actin Organization ◽  
Actin Networks ◽  
Cellular Processes ◽  
Competition And Cooperation ◽  
A Cell ◽  
Overlapping Sets

Many fundamental cellular processes such as division, polarization, endocytosis, and motility require the assembly, maintenance, and disassembly of filamentous actin (F-actin) networks at specific locations and times within the cell. The particular function of each network is governed by F-actin organization, size, and density as well as by its dynamics. The distinct characteristics of different F-actin networks are determined through the coordinated actions of specific sets of actin-binding proteins (ABPs). Furthermore, a cell typically assembles and uses multiple F-actin networks simultaneously within a common cytoplasm, so these networks must self-organize from a common pool of shared globular actin (G-actin) monomers and overlapping sets of ABPs. Recent advances in multicolor imaging and analysis of ABPs and their associated F-actin networks in cells, as well as the development of sophisticated in vitro reconstitutions of networks with ensembles of ABPs, have allowed the field to start uncovering the underlying principles by which cells self-organize diverse F-actin networks to execute basic cellular functions.

Polycystin expression is temporally and spatially regulated during renal development

1997 ◽  
Vol 272 (5) ◽  
pp. F602-F609 ◽  
Author(s):  
J. Van Adelsberg ◽  
S. Chamberlain ◽  
V. D'Agati
Keyword(s):  
Plasma Membranes ◽  
Predicted Amino Acid Sequence ◽  
Renal Development ◽  
Polycystic Kidney ◽  
Fetal Kidney ◽  
Spatial Regulation ◽  
Adult Kidney ◽  
A Cell ◽  
Autosomal Dominant Polycystic Kidney ◽  
Membrane Spanning

Mutations in PKD1 cause autosomal dominant polycystic kidney disease (ADPKD), a common genetic disease in which cysts form from kidney tubules. The predicted product of this gene is a novel protein with cell-adhesive and membrane-spanning domains. To test the hypothesis that polycystin, the product of the PKD1 gene, is a cell adhesion molecule, we raised antibodies against peptides derived from the unduplicated, membrane-spanning portion of the predicted amino acid sequence. These antibodies recognized membrane-associated polypeptides of 485 and 245 kDa in human fetal kidney homogenates. Expression was greater in fetal than adult kidney by both Western blot analysis and immunofluorescence. In fetal kidney, polycystin was localized to the plasma membranes of ureteric bud and comma and S-shaped bodies. However, in more mature tubules in fetal kidney, in adult kidney, and in polycystic kidney, the majority of polycystin staining was intracellular. The temporal and spatial regulation of polycystin expression during renal development lead us to speculate that polycystin may play a role in nephrogenesis.

Sterol and lipid trafficking in mammalian cells

2006 ◽  
Vol 34 (3) ◽  
pp. 335-339 ◽  
Author(s):  
F.R. Maxfield ◽  
M. Mondal
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Vesicular Transport ◽  
Cholesterol Content ◽  
Cellular Functions ◽  
Lipid Trafficking ◽  
Sterol Transport ◽  
A Cell ◽  
Asymmetrically Distributed

The pathways involved in the intracellular transport and distribution of lipids in general, and sterols in particular, are poorly understood. Cholesterol plays a major role in modulating membrane bilayer structure and important cellular functions, including signal transduction and membrane trafficking. Both the overall cholesterol content of a cell, as well as its distribution in specific organellar membranes are stringently regulated. Several diseases, many of which are incurable at present, have been characterized as results of impaired cholesterol transport and/or storage in the cells. Despite their importance, many fundamental aspects of intracellular sterol transport and distribution are not well understood. For instance, the relative roles of vesicular and non-vesicular transport of cholesterol have not yet been fully determined, nor are the non-vesicular transport mechanisms well characterized. Similarly, whether cholesterol is asymmetrically distributed between the two leaflets of biological membranes, and if so, how this asymmetry is maintained, is poorly understood. In this review, we present a summary of the current understanding of these aspects of intracellular trafficking and distribution of lipids, and more specifically, of sterols.

scholarly journals Proteomic Signatures of Clostridium difficile Stressed with Metronidazole, Vancomycin, or Fidaxomicin

Cells ◽  
2018 ◽  
Vol 7 (11) ◽  
pp. 213 ◽  
Author(s):  
Sandra Maaß ◽  
Andreas Otto ◽  
Dirk Albrecht ◽  
Katharina Riedel ◽  
Anke Trautwein-Schult ◽  
...  
Keyword(s):  
Clostridium Difficile ◽  
Antibiotic Treatment ◽  
Antimicrobial Agents ◽  
Cell Envelope ◽  
Protein Biosynthesis ◽  
Cellular Functions ◽  
Antibiotic Resistant ◽  
Incidence And Mortality ◽  
A Cell ◽  
Proteomic Response

The anaerobic pathogen Clostridium difficile is of growing significance for the health care system due to its increasing incidence and mortality. As C. difficile infection is both supported and treated by antibiotics, a deeper knowledge on how antimicrobial agents affect the physiology of this important pathogen may help to understand and prevent the development and spreading of antibiotic resistant strains. As the proteomic response of a cell to stress aims at counteracting the harmful effects of this stress, it can be expected that the pattern of a pathogen’s responses to antibiotic treatment will be dependent on the antibiotic mechanism of action. Hence, every antibiotic treatment is expected to result in a specific proteomic signature characterizing its mode of action. In the study presented here, the proteomic response of C. difficile 630∆erm to vancomycin, metronidazole, and fidaxomicin stress was investigated on the level of protein abundance and protein synthesis based on 2D PAGE. The quantification of 425 proteins of C. difficile allowed the deduction of proteomic signatures specific for each drug treatment. Indeed, these proteomic signatures indicate very specific cellular responses to each antibiotic with only little overlap of the responses. Whereas signature proteins for vancomycin stress fulfil various cellular functions, the proteomic signature of metronidazole stress is characterized by alterations of proteins involved in protein biosynthesis and protein degradation as well as in DNA replication, recombination, and repair. In contrast, proteins differentially expressed after fidaxomicin treatment can be assigned to amino acid biosynthesis, transcription, cell motility, and the cell envelope functions. Notably, the data provided by this study hint also at so far unknown antibiotic detoxification mechanisms.

scholarly journals Permeabilization of rat hepatocytes with Staphylococcus aureus alpha-toxin.

1985 ◽  
Vol 100 (6) ◽  
pp. 1922-1929 ◽  
Author(s):  
B F McEwen ◽  
W J Arion
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Alpha Toxin ◽  
Cellular Functions ◽  
Transmembrane Channel ◽  
Selective Permeability ◽  
Treatment Conditions ◽  
Transmission Electron ◽  
A Cell

Pathogenic staphylococci secrete a number of exotoxins, including alpha-toxin. alpha-Toxin induces lysis of erythrocytes and liposomes when its 3S protein monomers associate with the lipid bilayer and form a hexomeric transmembrane channel 3 nm in diameter. We have used alpha-toxin to render rat hepatocytes 93-100% permeable to trypan blue with a lactate dehydrogenase leakage less than or equal to 22%. Treatment conditions included incubation for 5-10 min at 37 degrees C and pH 7.0 with an alpha-toxin concentration of 4-35 human hemolytic U/ml and a cell concentration of 13-21 mg dry wt/ml. Scanning electron microscopy revealed signs of swelling in the treated hepatocytes, but there were no large lesions or gross damage to the cell surface. Transmission electron microscopy indicated that the nucleus, mitochondria, and cytoplasm were similar in control and treated cells and both had large regions of well-defined lamellar rough endoplasmic reticulum. Comparisons of the mannose-6-phosphatase and glucose-6-phosphatase activities demonstrated that 5-10 U/ml alpha-toxin rendered cells freely permeable to glucose-6-phosphate, while substantially preserving the selective permeability of the membranes of the endoplasmic reticulum and the functionality of the glucose-6-phosphatase system. Thus, alpha-toxin appears to have significant potential as a means to induce selective permeability to small ions. It should make possible the study of a variety of cellular functions in situ.

scholarly journals Mechanics defines the spatial pattern of compensatory proliferation

2021 ◽  
Author(s):  
Takumi Kawaue ◽  
Ivan Yow ◽  
Anh Phuong Le ◽  
Yuting Lou ◽  
Mavis Loberas ◽  
...  
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
Cell Loss ◽  
Spatial Inhomogeneity ◽  
Cellular Functions ◽  
Cell Numbers ◽  
Compensatory Proliferation ◽  
A Cell ◽  
Growth Promoting ◽  
Open Question

The number of cells in tissues is tightly controlled by cell division and cell death, and misregulation of cell numbers could lead to pathological conditions such as cancer. To maintain cell numbers in a tissue, a cell elimination process named programmed cell death or apoptosis, stimulates the proliferation of neighboring cells. This mechanism is called apoptosis-induced compensatory proliferation, which was originally reported more than 40 years ago. While only a limited number of the neigboring cells need to divide to compensate for apoptotic cell loss, the mechanisms that select cells for undergoing division remain an open question. Here we found that the spatial inhomogeneity in mechanotransduction through a growth-promoting transcription co-activator Yes-associated protein (YAP) in the neighboring tissue, accounts for the inhomogeneity of compensatory proliferation. Such inhomogeneous mechanotransduction arises from the combination of the non-uniform distribution of nuclear size, which is inherent in tissues, and the non-uniform pattern of mechanical force applied to the neighboring cells upon apoptosis. Our findings from a mechanical perspective complement the current biochemical understanding of compensatory growth and provide additional insights into cellular functions of how tissue precisely maintains its homeostasis.

scholarly journals Solubility and Bioactivity of the Pseudomonas Quinolone Signal Are Increased by a Pseudomonas aeruginosa-Produced Surfactant

2005 ◽  
Vol 73 (2) ◽  
pp. 878-882 ◽  
Author(s):  
M. Worth Calfee ◽  
John G. Shelton ◽  
James A. McCubrey ◽  
Everett C. Pesci
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Aqueous Solutions ◽  
Opportunistic Pathogen ◽  
Homoserine Lactone ◽  
Cellular Functions ◽  
Pseudomonas Quinolone Signal ◽  
Serious Infections ◽  
Enhanced Solubility ◽  
Apoptosis Assay ◽  
A Cell

ABSTRACT Pseudomonas aeruginosa is a gram-negative bacterium that causes serious infections in immunocompromised individuals and cystic fibrosis patients. This opportunistic pathogen controls many of its virulence factors and cellular functions through the activity of three cell-to-cell signals, N-(3-oxododecanoyl)-l-homoserine lactone, N-butyryl-l-homoserine lactone, and the Pseudomonas quinolone signal (PQS). The activity of these signals is dependent upon their ability to dissolve in and freely diffuse through the aqueous solution in which P. aeruginosa happens to reside. Despite this, our data indicated that PQS was relatively insoluble in aqueous solutions, which led us to postulate that P. aeruginosa could be producing a PQS-solubilizing factor. In this report, we show that the P. aeruginosa-produced biosurfactant rhamnolipid greatly enhances the solubility of PQS in aqueous solutions. The enhanced solubility of PQS led to an increase in PQS bioactivity, as measured by both a gene induction assay and an apoptosis assay. This is the first demonstration of the importance of a bacterial surfactant in the solubilization and bioactivity of a cell-to-cell signal.

scholarly journals Bundling up the Role of the Actin Cytoskeleton in Primary Root Growth

2021 ◽  
Vol 12 ◽  
Author(s):  
Judith García-González ◽  
Kasper van Gelderen
Keyword(s):  
Root Growth ◽  
Actin Cytoskeleton ◽  
Cell Elongation ◽  
Feedback Loop ◽  
Primary Root ◽  
Actin Binding ◽  
Actin Network ◽  
Actin Organization ◽  
Primary Root Growth

Primary root growth is required by the plant to anchor in the soil and reach out for nutrients and water, while dealing with obstacles. Efficient root elongation and bending depends upon the coordinated action of environmental sensing, signal transduction, and growth responses. The actin cytoskeleton is a highly plastic network that constitutes a point of integration for environmental stimuli and hormonal pathways. In this review, we present a detailed compilation highlighting the importance of the actin cytoskeleton during primary root growth and we describe how actin-binding proteins, plant hormones, and actin-disrupting drugs affect root growth and root actin. We also discuss the feedback loop between actin and root responses to light and gravity. Actin affects cell division and elongation through the control of its own organization. We remark upon the importance of longitudinally oriented actin bundles as a hallmark of cell elongation as well as the role of the actin cytoskeleton in protein trafficking and vacuolar reshaping during this process. The actin network is shaped by a plethora of actin-binding proteins; however, there is still a large gap in connecting the molecular function of these proteins with their developmental effects. Here, we summarize their function and known effects on primary root growth with a focus on their high level of specialization. Light and gravity are key factors that help us understand root growth directionality. The response of the root to gravity relies on hormonal, particularly auxin, homeostasis, and the actin cytoskeleton. Actin is necessary for the perception of the gravity stimulus via the repositioning of sedimenting statoliths, but it is also involved in mediating the growth response via the trafficking of auxin transporters and cell elongation. Furthermore, auxin and auxin analogs can affect the composition of the actin network, indicating a potential feedback loop. Light, in its turn, affects actin organization and hence, root growth, although its precise role remains largely unknown. Recently, fundamental studies with the latest techniques have given us more in-depth knowledge of the role and organization of actin in the coordination of root growth; however, there remains a lot to discover, especially in how actin organization helps cell shaping, and therefore root growth.

The SAC3 gene encodes a nuclear protein required for normal progression of mitosis

1996 ◽  
Vol 109 (6) ◽  
pp. 1575-1583
Author(s):  
A. Bauer ◽  
R. Kolling
Keyword(s):  
Cell Cycle ◽  
Actin Cytoskeleton ◽  
Nuclear Protein ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Cell Cycle Delay ◽  
A Cell ◽  
Single Nucleus ◽  
Microtubule Function ◽  
Mitotic Defect

The SAC3 gene of Saccharomyces serevisiae has been implicated in actin function by genetic experiments showing that a temperature sensitive mutation in the essential actin gene (actl-1) can be suppressed by mutations in SAC3. An involvement of SAC3 in actin function is further suggested by the observation that the actin cytoskeleton is altered in SAC3 mutants. Our fractionation experiments, however, point to a nuclear localization of Sac3p. On sucrose density gradients Sac3p co-fractionated with the nuclear organelle markers examined. Furthermore, Sac3p was enriched 10-fold in a nuclei preparation along with the nuclear protein Nop1p. In this report we further show that SAC3 function is required for normal progression of mitosis. SAC3 mutants showed a higher fraction of large-budded cells in culture, indicative of a cell cycle delay. The predominant population among the large-budded sac3 cells were cells with a single nucleus at the bud-neck and a short intranuclear spindle. This suggests that a cell cycle delay occurs in mitosis prior to anaphase. The observation that SAC3 mutants lose chromosomes with higher frequency than wild-type is another indication for a mitotic defect in SAC3 mutants. We further noticed that SAC3 mutants are more resistant against the microtubule destabilizing drug benomyl. This finding suggests that SAC3 is involved, directly or indirectly, in microtubule function. In summary, our data indicate that SAC3 is involved in a process which affects both the actin cytoskeleton and mitosis.

The actin cytoskeleton is required to elaborate and maintain spatial patterning during trichome cell morphogenesis in Arabidopsis thaliana

Development ◽  
1999 ◽  
Vol 126 (24) ◽  
pp. 5559-5568 ◽  
Author(s):  
J. Mathur ◽  
P. Spielhofer ◽  
B. Kost ◽  
N. Chua
Keyword(s):  
Arabidopsis Thaliana ◽  
Actin Cytoskeleton ◽  
Spatial Patterning ◽  
Actin Microfilaments ◽  
Cell Morphogenesis ◽  
Actin Organization ◽  
Cytoskeleton Organization ◽  
Branch Formation ◽  
Actin Cytoskeleton Organization ◽  
Trichome Cell

Arabidopsis thaliana trichomes provide an attractive model system to dissect molecular processes involved in the generation of shape and form in single cell morphogenesis in plants. We have used transgenic Arabidopsis plants carrying a GFP-talin chimeric gene to analyze the role of the actin cytoskeleton in trichome cell morphogenesis. We found that during trichome cell development the actin microfilaments assumed an increasing degree of complexity from fine filaments to thick, longitudinally stretched cables. Disruption of the F-actin cytoskeleton by actin antagonists produced distorted but branched trichomes which phenocopied trichomes of mutants belonging to the ‘distorted’ class. Subsequent analysis of the actin cytoskeleton in trichomes of the distorted mutants, alien, crooked, distorted1, gnarled, klunker and wurm uncovered actin organization defects in each case. Treatments of wild-type seedlings with microtubule-interacting drugs elicited a radically different trichome phenotype characterized by isotropic growth and a severe inhibition of branch formation; these trichomes did not show defects in actin cytoskeleton organization. A normal actin cytoskeleton was also observed in trichomes of the zwichel mutant which have reduced branching. ZWICHEL, which was previously shown to encode a kinesin-like protein is thought to be involved in microtubule-linked processes. Based on our results we propose that microtubules establish the spatial patterning of trichome branches whilst actin microfilaments elaborate and maintain the overall trichome pattern during development.

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