scholarly journals Actin modulates shape and mechanics of tubular membranes

2019 ◽  
Author(s):  
A. Allard ◽  
M. Bouzid ◽  
T. Betz ◽  
C. Simon ◽  
M. Abou-Ghali ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Plant Cells ◽  
Tube Surface ◽  
Apparent Contradiction ◽  
Single Tube ◽  
Tubular Membrane ◽  
Tubular Membranes

The actin cytoskeleton shapes cells and also organizes internal membranous compartments. In particular, it interacts with membranes in intracellular transport of material in mammalian cells, yeast or plant cells. Tubular membrane intermediates, pulled along microtubule tracks, are involved during these processes, and destabilize into vesicles. While the role of actin in this destabilization process is still debated, literature also provide examples of membranous structures stabilization by actin. To directly address this apparent contradiction, we mimic the geometry of tubular intermediates with preformed membrane tubes. The growth of an actin sleeve at the tube surface is monitored spatio-temporally. Depending on network cohesiveness, actin is able to stabilize, or maintain membrane tubes under pulling. Indeed, on a single tube, thicker portions correlate with the presence of actin. Such structures relax over several minutes, and may provide enough time and curvature geometries for other proteins to act on tube stability.

scholarly journals Actin modulates shape and mechanics of tubular membranes

2020 ◽  
Vol 6 (17) ◽  
pp. eaaz3050
Author(s):  
A. Allard ◽  
M. Bouzid ◽  
T. Betz ◽  
C. Simon ◽  
M. Abou-Ghali ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Plant Cells ◽  
Tube Surface ◽  
Apparent Contradiction ◽  
Single Tube ◽  
Tubular Membrane ◽  
Tubular Membranes

The actin cytoskeleton shapes cells and also organizes internal membranous compartments. In particular, it interacts with membranes for intracellular transport of material in mammalian cells, yeast, or plant cells. Tubular membrane intermediates, pulled along microtubule tracks, are formed during this process and destabilize into vesicles. While the role of actin in tubule destabilization through scission is suggested, literature also provides examples of actin-mediated stabilization of membranous structures. To directly address this apparent contradiction, we mimic the geometry of tubular intermediates with preformed membrane tubes. The growth of an actin sleeve at the tube surface is monitored spatiotemporally. Depending on network cohesiveness, actin is able to entirely stabilize or locally maintain membrane tubes under pulling. On a single tube, thicker portions correlate with the presence of actin. These structures relax over several minutes and may provide enough time and curvature geometries for other proteins to act on tube stability.

Immunolocalization of the intracellular sites of accumulation of mutant influenza hemagglutinins by Electron Microscopy

1989 ◽  
Vol 47 ◽  
pp. 968-969
Author(s):  
K. McCammon ◽  
M. Segal ◽  
J. Sambrook ◽  
M. J. Gething ◽  
A. McDowall
Keyword(s):  
Electron Microscopy ◽  
Golgi Apparatus ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Secretory Pathway ◽  
Cysteine Residue ◽  
Homologous Sequence ◽  
Golgi Compartment ◽  
Golgi Network

The hemagglutinin (HA) of influenza virus has been used as a model system to study the biosynthesis and intracellular transport of integral membrane proteins in mammalian cells. To investigate the role of protein structure in facilitating transport along the secretory pathway, we have examined the expression in monkey CV-1 cells of a large number of mutant HA molecules. The majority of the HA mutants do not progress along the secretory pathway and accumulate in the endoplasmic reticulum (ER), and we have shown that assembly of newly-synthesized HA monomers into correctly folded trimeric structures is required for transport of the protein to the Golgi apparatus. By contrast, only one HA mutant has beegn characterized whose transport is blocked at a post-Golgi stage of the pathway and thus little is known about the factors involved in the sorting of the HA molecule from the Golgi apparatus to the plasma membrane (PM). In this study we are using electron microscopy to precisely define the intracellular site of accumulation of two mutant HAs whose transport is blocked at different stages of the secretory pathway. In mutant HAJS67, a cysteine residue (cys67) involved in a key disulfide bond has been substituted by a serine residue. In mutant HA164, the 10 amino acid cytoplasmic tail of the wild-type HA has been replaced by a non-homologous sequence of 16 amino acids. Biochemical and immunof1uoresence analyses have indicated that HAJS67 molecules remain in the ER compartment while HA164 is largely confined to a post-Golgi compartment, possibly the trans Golgi network (TGN).

Early steps in cold sensing by plant cells: the role of actin cytoskeleton and membrane fluidity

2000 ◽  
Vol 23 (6) ◽  
pp. 785-794 ◽  
Author(s):  
Bjorn Larus Orvar ◽  
Veena Sangwan ◽  
Franz Omann ◽  
Rajinder S. Dhindsa
Keyword(s):  
Actin Cytoskeleton ◽  
Membrane Fluidity ◽  
Plant Cells ◽  
Cold Sensing

Cell surface transport, oligomerization, and endocytosis of chimeric type II glycoproteins: role of cytoplasmic and anchor domains

1991 ◽  
Vol 11 (5) ◽  
pp. 2675-2685
Author(s):  
A Kundu ◽  
M A Jabbar ◽  
D P Nayak
Keyword(s):  
Influenza Virus ◽  
Cell Surface ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Cytoplasmic Domain ◽  
Type Ii ◽  
Human Influenza Virus ◽  
Chimeric Genes ◽  
Signal Anchor

We investigated the role of cytoplasmic and anchor domains of type II glycoproteins in intracellular transport, oligomerization, and endocytosis by expressing the wild-type and chimeric genes in mammalian cells. Chimeric genes were constructed by exchanging the DNA segments that encode the cytoplasmic and anchor domains between the human influenza virus (A/WSN/33) neuraminidase (NA) and transferrin receptor (TR). The chimeric proteins in which domains were exchanged precisely were productively targeted to the cell surface. However, the proteins appeared to assemble differently in the intracellular compartment. For example, while TR existed predominantly as a dimer, NATR delta 90, containing the cytoplasmic and signal-anchor domains of NA and the ectodomain of TR, was present as a tetramer, a dimer, and a monomer. Similarly, the influenza virus NA existed predominantly as a tetramer but TRNA delta 35, in which the cytoplasmic and signal-anchor domains of TR were joined to the ectodomain of NA, existed predominantly as a dimer, suggesting that the cytoplasmic and anchor domains of type II glycoproteins affect the subunit assembly of heterologous ectodomains. In addition, we analyzed the role of the cytoplasmic domain in endocytosis. NA and NATR delta 90 did not undergo endocytosis, whereas both TR and TRNA delta 35 were internalized efficiently, demonstrating that the NH2 cytoplasmic domain of TR was capable of internalizing a heterologous ectodomain (NA) from the cell surface.

90. Role of the actin cytoskeleton on freeze-induced dehydration of mammalian cells

Cryobiology ◽  
2008 ◽  
Vol 57 (3) ◽  
pp. 333-334
Author(s):  
Vishard Ragoonanan ◽  
Alptekin Aksan
Keyword(s):  
Actin Cytoskeleton ◽  
Mammalian Cells

Probing cytoplasmic organization and the actin cytoskeleton of plant cells with optical tweezers

2010 ◽  
Vol 38 (3) ◽  
pp. 823-828 ◽  
Author(s):  
Tijs Ketelaar ◽  
Hannie S. van der Honing ◽  
Anne Mie C. Emons
Keyword(s):  
Actin Cytoskeleton ◽  
Physical Properties ◽  
Optical Tweezers ◽  
Intracellular Transport ◽  
Plant Cells ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Structural Basis ◽  
Actin Organization ◽  
Cytoplasmic Organization

In interphase plant cells, the actin cytoskeleton is essential for intracellular transport and organization. To fully understand how the actin cytoskeleton functions as the structural basis for cytoplasmic organization, both molecular and physical aspects of the actin organization have to be considered. In the present review, we discuss literature that gives an insight into how cytoplasmic organization is achieved and in which actin-binding proteins have been identified that play a role in this process. We discuss how physical properties of the actin cytoskeleton in the cytoplasm of live plant cells, such as deformability and elasticity, can be probed by using optical tweezers. This technique allows non-invasive manipulation of cytoplasmic organization. Optical tweezers, integrated in a confocal microscope, can be used to manipulate cytoplasmic organization while studying actin dynamics. By combining this with mutant studies and drug applications, insight can be obtained about how the physical properties of the actin cytoskeleton, and thus the cytoplasmic organization, are influenced by different cellular processes.

scholarly journals Dynamics and organization of actin-labelled granules as a rapid transport mode of actin cytoskeleton components in Foraminifera

2019 ◽  
Author(s):  
Jan Goleń ◽  
Jarosław Tyszka ◽  
Ulf Bickmeyer ◽  
Jelle Bijma
Keyword(s):  
Actin Cytoskeleton ◽  
Intracellular Transport ◽  
Plant Cells ◽  
Fluorescent Imaging ◽  
Electron Microscopic ◽  
Cytoskeleton Organization ◽  
Wide Range ◽  
Rapid Transport ◽  
Tubulin Paracrystals

Abstract. Recent advances in fluorescent imaging facilitate actualistic studies on organisms used for palaeoceanographic reconstructions. Observations of cytoskeleton organization and dynamics in living foraminifera foster understanding of morphogenetic and biomineralization principles. This paper describes the organisation of a foraminiferal actin cytoskeleton using in vivo staining based on fluorescent SiR-actin. Surprisingly, the most distinctive feature in the organisation of actin in Foraminifera is the prevalence of actin-labelled granules (ALGs) within pseudopodial structures. Fluorescent signal obtained from granules dominate over dispersed signal from the actin meshwork. Actin-labelled granules are small (around 1 µm in diameter) actin-rich organelles demonstrating a wide range of motility behaviours from almost stationary oscillating around certain points to exhibiting rapid motion. These structures are present both in Globothalamea (Amphistegina, Ammonia) and Tubothalamea (Quinqueloculina). They are found to be active in all kinds of pseudopodial ectoplasmic structures, including granuloreticulopodia, globopodia, and lamellipodia, as well as within the endoplasm itself. Two hypotheses regarding their function are proposed: (1) They are involved in endocytosis and intracellular transport of different kinds of cargo; (2) They transport prefabricated and/or recycled actin fibres to the sites where they are needed. These hypothesis are not mutually exclusive. The first hypothesis is based on the presence of similar actin structures in fungi, fungi-like protists and some plant cells. The later hypothesis is based on the assumption that actin granules are analogous to tubulin paracrystals responsible for efficient transport of tubulin. Actin patches transported in that manner are most likely involved in maintaining shape, rapid reorganization, and elasticity of pseudopodial structures, as well as in adhesion to the substrate. Finally, our comparative studies suggest that a large proportion of actin-labelled granules probably represent fibrillar vesicles and elliptical fuzzy coated vesicles often identified in TEM images. Correlative fluorescent electron microscopic observations are proposed to verify this interpretation.

scholarly journals Cell surface transport, oligomerization, and endocytosis of chimeric type II glycoproteins: role of cytoplasmic and anchor domains.

1991 ◽  
Vol 11 (5) ◽  
pp. 2675-2685 ◽  
Author(s):  
A Kundu ◽  
M A Jabbar ◽  
D P Nayak
Keyword(s):  
Influenza Virus ◽  
Cell Surface ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Cytoplasmic Domain ◽  
Type Ii ◽  
Human Influenza Virus ◽  
Chimeric Genes ◽  
Signal Anchor

We investigated the role of cytoplasmic and anchor domains of type II glycoproteins in intracellular transport, oligomerization, and endocytosis by expressing the wild-type and chimeric genes in mammalian cells. Chimeric genes were constructed by exchanging the DNA segments that encode the cytoplasmic and anchor domains between the human influenza virus (A/WSN/33) neuraminidase (NA) and transferrin receptor (TR). The chimeric proteins in which domains were exchanged precisely were productively targeted to the cell surface. However, the proteins appeared to assemble differently in the intracellular compartment. For example, while TR existed predominantly as a dimer, NATR delta 90, containing the cytoplasmic and signal-anchor domains of NA and the ectodomain of TR, was present as a tetramer, a dimer, and a monomer. Similarly, the influenza virus NA existed predominantly as a tetramer but TRNA delta 35, in which the cytoplasmic and signal-anchor domains of TR were joined to the ectodomain of NA, existed predominantly as a dimer, suggesting that the cytoplasmic and anchor domains of type II glycoproteins affect the subunit assembly of heterologous ectodomains. In addition, we analyzed the role of the cytoplasmic domain in endocytosis. NA and NATR delta 90 did not undergo endocytosis, whereas both TR and TRNA delta 35 were internalized efficiently, demonstrating that the NH2 cytoplasmic domain of TR was capable of internalizing a heterologous ectodomain (NA) from the cell surface.

Confocal microscopy of the cytoskeleton in living plant cells following microinjection of fluorescent probes

1993 ◽  
Vol 51 ◽  
pp. 130-131
Author(s):  
Ann Cleary
Keyword(s):  
Cell Division ◽  
Fluorescent Probes ◽  
Actin Filaments ◽  
Intracellular Transport ◽  
Cell Structure ◽  
Plant Cells ◽  
Cell Plate ◽  
Cell Cortex ◽  
Living Plant ◽  
Rhodamine Phalloidin

Microinjection of fluorescent probes into living plant cells reveals new aspects of cell structure and function. Microtubules and actin filaments are dynamic components of the cytoskeleton and are involved in cell growth, division and intracellular transport. To date, cytoskeletal probes used in microinjection studies have included rhodamine-phalloidin for labelling actin filaments and fluorescently labelled animal tubulin for incorporation into microtubules. From a recent study of Tradescantia stamen hair cells it appears that actin may have a role in defining the plane of cell division. Unlike microtubules, actin is present in the cell cortex and delimits the division site throughout mitosis. Herein, I shall describe actin, its arrangement and putative role in cell plate placement, in another material, living cells of Tradescantia leaf epidermis.The epidermis is peeled from the abaxial surface of young leaves usually without disruption to cytoplasmic streaming or cell division. The peel is stuck to the base of a well slide using 0.1% polyethylenimine and bathed in a solution of 1% mannitol +/− 1 mM probenecid.

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