scholarly journals Assembly and Function of the Actin Cytoskeleton of Yeast: Relationships between Cables and Patches

1998 ◽  
Vol 142 (6) ◽  
pp. 1501-1517 ◽  
Author(s):  
Tatiana S. Karpova ◽  
James G. McNally ◽  
Samuel L. Moltz ◽  
John A. Cooper
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Cell Types ◽  
Eukaryotic Cells ◽  
Filamentous Actin ◽  
Functional Relationships ◽  
Highly Correlated ◽  
Actin Cables ◽  
And Function ◽  
Different Parts

Actin in eukaryotic cells is found in different pools, with filaments being organized into a variety of supramolecular assemblies. To investigate the assembly and functional relationships between different parts of the actin cytoskeleton in one cell, we studied the morphology and dynamics of cables and patches in yeast. The fine structure of actin cables and the manner in which cables disassemble support a model in which cables are composed of a number of overlapping actin filaments. No evidence for intrinsic polarity of cables was found. To investigate to what extent different parts of the actin cytoskeleton depend on each other, we looked for relationships between cables and patches. Patches and cables were often associated, and their polarized distributions were highly correlated. Therefore, patches and cables do appear to depend on each other for assembly and function. Many cell types show rearrangements of the actin cytoskeleton, which can occur via assembly or movement of actin filaments. In our studies, dramatic changes in actin polarization did not include changes in filamentous actin. In addition, the concentration of actin patches was relatively constant as cells grew. Therefore, cells do not have bursts of activity in which new parts of the actin cytoskeleton are created.

scholarly journals Overexpression of cofilin stimulates bundling of actin filaments, membrane ruffling, and cell movement in Dictyostelium.

1996 ◽  
Vol 132 (3) ◽  
pp. 335-344 ◽  
Author(s):  
H Aizawa ◽  
K Sutoh ◽  
I Yahara
Keyword(s):  
Actin Filaments ◽  
Cell Movement ◽  
Structure And Function ◽  
Cross Linking ◽  
Low Molecular Weight ◽  
Filamentous Actin ◽  
Membrane Ruffling ◽  
And Function

Cofilin is a low molecular weight actin-modulating protein whose structure and function are conserved among eucaryotes. Cofilin exhibits in vitro both a monomeric actin-sequestering activity and a filamentous actin-severing activity. To investigate in vivo functions of cofilin, cofilin was overexpressed in Dictyostelium discoideum cells. An increase in the content of D. discoideum cofilin (d-cofilin) by sevenfold induced a co-overproduction of actin by threefold. In cells over-expressing d-cofilin, the amount of filamentous actin but not that of monomeric actin was increased. Overexpressed d-cofilin co-sedimented with actin filaments, suggesting that the sequestering activity of d-cofilin is weak in vivo. The overexpression of d-cofilin increased actin bundles just beneath ruffling membranes where d-cofilin was co-localized. The overexpression of d-cofilin also stimulated cell movement as well as membrane ruffling. We have demonstrated in vitro that d-cofilin transformed latticework of actin filaments cross-linked by alpha-actinin into bundles probably by severing the filaments. D. discoideum cofilin may sever actin filaments in vivo and induce bundling of the filaments in the presence of cross-linking proteins so as to generate contractile systems involved in membrane ruffling and cell movement.

scholarly journals Comparison of actin and cell surface dynamics in motile fibroblasts.

1992 ◽  
Vol 119 (2) ◽  
pp. 367-377 ◽  
Author(s):  
J A Theriot ◽  
T J Mitchison
Keyword(s):  
Actin Cytoskeleton ◽  
Dynamic Behavior ◽  
Actin Filaments ◽  
Half Life ◽  
Dorsal Surface ◽  
Cell Types ◽  
3T3 Cells ◽  
3T3 Fibroblasts ◽  
Continuous Filament ◽  
Time Required

We have investigated the dynamic behavior of actin in fibroblast lamellipodia using photoactivation of fluorescence. Activated regions of caged resorufin (CR)-labeled actin in lamellipodia of IMR 90 and MC7 3T3 fibroblasts were observed to move centripetally over time. Thus in these cells, actin filaments move centripetally relative to the substrate. Rates were characteristic for each cell type; 0.66 +/- 0.27 microns/min in IMR 90 and 0.36 +/- 0.16 microns/min in MC7 3T3 cells. In neither case was there any correlation between the rate of actin movement and the rate of lamellipodial protrusion. The half-life of the activated CR-actin filaments was approximately 1 min in IMR 90 lamellipodia, and approximately 3 min in MC7 3T3 lamellipodia. Thus continuous filament turnover accompanies centripetal movement. In both cell types, the length of time required for a section of the actin meshwork to traverse the lamellipodium was several times longer than the filament half-life. The dynamic behavior of the dorsal surface of the cell was also observed by tracking lectin-coated beads on the surface and phase-dense features within lamellipodia of MC7 3T3 cells. The movement of these dorsal features occurred at rates approximately three times faster than the rate of movement of the underlying bulk actin cytoskeleton, even when measured in the same individual cells. Thus the transport of these dorsal features must occur by some mechanism other than simple attachment to the moving bulk actin cytoskeleton.

scholarly journals Schizosaccharomyces pombe Pak-related protein, Pak1p/Orb2p, phosphorylates myosin regulatory light chain to inhibit cytokinesis

2008 ◽  
Vol 183 (5) ◽  
pp. 785-793 ◽  
Author(s):  
Tsui-Han Loo ◽  
Mohan Balasubramanian
Keyword(s):  
Actin Cytoskeleton ◽  
Schizosaccharomyces Pombe ◽  
Light Chain ◽  
Myosin Ii ◽  
Regulatory Light Chain ◽  
Eukaryotic Cells ◽  
Myosin Regulatory Light Chain ◽  
Related Protein ◽  
Filamentous Actin

p21-activated kinases (Paks) have been identified in a variety of eukaryotic cells as key effectors of the Cdc42 family of guanosine triphosphatases. Pak kinases play important roles in regulating the filamentous actin cytoskeleton. In this study, we describe a function for the Schizosaccharomyces pombe Pak-related protein Pak1p/Orb2p in cytokinesis. Pak1p localizes to the actomyosin ring during mitosis and cytokinesis. Loss of Pak1p function leads to accelerated cytokinesis. Pak1p mediates phosphorylation of myosin II regulatory light chain Rlc1p at serine residues 35 and 36 in vivo. Interestingly, loss of Pak1p function or substitution of serine 35 and serine 36 of Rlc1p with alanines, thereby mimicking a dephosphorylated state of Rlc1p, leads to defective coordination of mitosis and cytokinesis. This study reveals a new mechanism involving Pak1p kinase that helps ensure the fidelity of cytokinesis.

scholarly journals Bee1, a Yeast Protein with Homology to Wiscott-Aldrich Syndrome Protein, Is Critical for the Assembly of Cortical Actin Cytoskeleton

1997 ◽  
Vol 136 (3) ◽  
pp. 649-658 ◽  
Author(s):  
Rong Li
Keyword(s):  
Actin Cytoskeleton ◽  
Protein Function ◽  
Actin Filaments ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Yeast Protein ◽  
Wiskott Aldrich Syndrome ◽  
Striking Change ◽  
And Function ◽  
Syndrome Protein

Yeast protein, Bee1, exhibits sequence homology to Wiskott-Aldrich syndrome protein (WASP), a human protein that may link signaling pathways to the actin cytoskeleton. Mutations in WASP are the primary cause of Wiskott-Aldrich syndrome, characterized by immuno-deficiencies and defects in blood cell morphogenesis. This report describes the characterization of Bee1 protein function in budding yeast. Disruption of BEE1 causes a striking change in the organization of actin filaments, resulting in defects in budding and cytokinesis. Rather than assemble into cortically associated patches, actin filaments in the buds of Δbee1 cells form aberrant bundles that do not contain most of the cortical cytoskeletal components. It is significant that Δbee1 is the only mutation reported so far that abolishes cortical actin patches in the bud. Bee1 protein is localized to actin patches and interacts with Sla1p, a Src homology 3 domain–containing protein previously implicated in actin assembly and function. Thus, Bee1 protein may be a crucial component of a cytoskeletal complex that controls the assembly and organization of actin filaments at the cell cortex.

Tropomyosin-Based Regulation of the Actin Cytoskeleton in Time and Space

2008 ◽  
Vol 88 (1) ◽  
pp. 1-35 ◽  
Author(s):  
Peter Gunning ◽  
Geraldine O’neill ◽  
Edna Hardeman
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Coiled Coil ◽  
Cell Types ◽  
Actin Binding ◽  
Regulation Of Expression ◽  
Wide Range ◽  
Muscle Tropomyosin ◽  
The Many

Tropomyosins are rodlike coiled coil dimers that form continuous polymers along the major groove of most actin filaments. In striated muscle, tropomyosin regulates the actin-myosin interaction and, hence, contraction of muscle. Tropomyosin also contributes to most, if not all, functions of the actin cytoskeleton, and its role is essential for the viability of a wide range of organisms. The ability of tropomyosin to contribute to the many functions of the actin cytoskeleton is related to the temporal and spatial regulation of expression of tropomyosin isoforms. Qualitative and quantitative changes in tropomyosin isoform expression accompany morphogenesis in a range of cell types. The isoforms are segregated to different intracellular pools of actin filaments and confer different properties to these filaments. Mutations in tropomyosins are directly involved in cardiac and skeletal muscle diseases. Alterations in tropomyosin expression directly contribute to the growth and spread of cancer. The functional specificity of tropomyosins is related to the collaborative interactions of the isoforms with different actin binding proteins such as cofilin, gelsolin, Arp 2/3, myosin, caldesmon, and tropomodulin. It is proposed that local changes in signaling activity may be sufficient to drive the assembly of isoform-specific complexes at different intracellular sites.

SRO9, a Multicopy Suppressor of the Bud Gpowth Defect in the Saccharomyces cerevisiae rho3-Deficient Cells, Shows Strong Genetic Interactions With Tropomyosin Genes, Suggesting Its Role in Organization of the Actin Cytoskeleton

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1003-1016
Author(s):  
Mitsuhiro Kagami ◽  
Akio Toh-e ◽  
Yasushi Matsui
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Rna Binding ◽  
Small Gtpase ◽  
Growth Defect ◽  
Cortical Actin ◽  
Cytoplasmic Factor ◽  
Multicopy Suppressor ◽  
Actin Cables

RHO3 encodes a Rho-type small GTPase in the yeast Saccharomyces cerevisiae and is involved in the proper organization of the actin cytoskeleton required for bud growth. SRO9 (YCL37c) was isolated as a multicopy suppressor of a rho3Δ mutation. An Sro9p domain required for function is similar to a domain in the La protein (an RNA-binding protein). Disruption of SRO9 did not affect vegetative growth, even with the simultaneous disruption of an SRO9 homologue, SRO99. However, sro9Δ was synthetically lethal with a disruption of TPM1, which encodes tropomyosin; sro9Δ tpm1Δ cells did not distribute cortical actin patches properly and lysed. We isolated TPM2, the other gene for tropomyosin, as a multicopy suppressor of a tpm1Δ sro9Δ double mutant. Genetic analysis suggests that TPM2 is functionally related to TPM1 and that tropomyosin is important but not essential for cell growth. Overexpression of SRO9 suppressed the growth defect in tpm1Δ tpm2Δ cells, disappearance of cables of actin filaments in both rho3Δ cells and tpm1Δ cells, and temperature sensitivity of actin mutant cells (act1-1 cells), suggesting that Sro9p has a function that overlaps or is related to tropomyosin function. Unlike tropomyosin, Sro9p does not colocalize with actin cables but is diffusely cytoplasmic. These results suggest that Sro9p is a new cytoplasmic factor involved in the organization of actin filaments.

scholarly journals GPCR-induced calcium transients trigger nuclear actin assembly for chromatin dynamics

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Ying Wang ◽  
Alice Sherrard ◽  
Bing Zhao ◽  
Michael Melak ◽  
Jonathan Trautwein ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Calcium Release ◽  
Nuclear Actin ◽  
Actin Assembly ◽  
Filamentous Actin ◽  
Cell Nuclei ◽  
Chromatin Dynamics ◽  
Surface Receptors ◽  
Rapid Responses ◽  
And Function

AbstractAlthough the properties of the actin cytoskeleton in the cytoplasm are well characterized, the regulation and function of nuclear actin filaments are only recently emerging. We previously demonstrated serum-induced, transient assembly of filamentous actin within somatic cell nuclei. However, the extracellular cues, cell surface receptors as well as underlying signaling mechanisms have been unclear. Here we demonstrate that physiological ligands for G protein-coupled receptors (GPCRs) promote nuclear F-actin assembly via heterotrimeric Gαq proteins. Signal-induced nuclear actin responses require calcium release from the endoplasmic reticulum (ER) targeting the ER-associated formin INF2 at the inner nuclear membrane (INM). Notably, calcium signaling promotes the polymerization of linear actin filaments emanating from the INM towards the nuclear interior. We show that GPCR and calcium elevations trigger nuclear actin-dependent alterations in chromatin organization, uncovering a general cellular mechanism by which physiological ligands and calcium promote nuclear F-actin assembly for rapid responses towards chromatin dynamics.

Versatile roles for myosin Va in dense core vesicle biogenesis and function

2010 ◽  
Vol 38 (1) ◽  
pp. 199-204 ◽  
Author(s):  
Tanja Kögel ◽  
Claudia Margarethe Bittins ◽  
Rüdiger Rudolf ◽  
Hans-Hermann Gerdes
Keyword(s):  
Actin Filaments ◽  
Current Knowledge ◽  
Cell Types ◽  
Dense Core ◽  
Dense Core Vesicle ◽  
Experimental Systems ◽  
Vesicle Biogenesis ◽  
Myosin Va ◽  
And Function ◽  
Different Cell Types

The motor protein myosin Va is involved in multiple successive steps in the development of dense-core vesicles, such as in the membrane remodelling during their maturation, their transport along actin filaments and the regulation of their exocytosis. In the present paper, we summarize the current knowledge on the roles of myosin Va in the different steps of dense-core vesicle biogenesis and exocytosis, and compare findings obtained from different cell types and experimental systems.

scholarly journals Fyn Mediates High Glucose-Induced Actin Cytoskeleton Reorganization of Podocytes via Promoting ROCK Activation In Vitro

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Zhimei Lv ◽  
Mengsi Hu ◽  
Xiaoxu Ren ◽  
Minghua Fan ◽  
Junhui Zhen ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
High Glucose ◽  
Tyrosine Kinases ◽  
Cell Types ◽  
Filamentous Actin ◽  
Reversal Effect ◽  
Podocyte Damage ◽  
Cytoskeleton Reorganization ◽  
Cytoskeleton Remodeling

Fyn, a member of the Src family of tyrosine kinases, is a key regulator in cytoskeletal remodeling in a variety of cell types. Recent studies have demonstrated that Fyn is responsible for nephrin tyrosine phosphorylation, which will result in polymerization of actin filaments and podocyte damage. Thus detailed involvement of Fyn in podocytes is to be elucidated. In this study, we investigated the potential role of Fyn/ROCK signaling and its interactions with paxillin. Our results presented that high glucose led to filamentous actin (F-actin) rearrangement in podocytes, accompanied by paxillin phosphorylation and increased cell motility, during which Fyn and ROCK were markedly activated. Gene knockdown of Fyn by siRNA showed a reversal effect on high glucose-induced podocyte damage and ROCK activation; however, inhibition of ROCK had no significant effects on Fyn phosphorylation. These observations demonstrate that in vitro Fyn mediates high glucose-induced actin cytoskeleton remodeling of podocytes via promoting ROCK activation and paxillin phosphorylation.

scholarly journals Clathrin plaques and associated actin anchor intermediate filaments in skeletal muscle

2019 ◽  
Vol 30 (5) ◽  
pp. 579-590 ◽  
Author(s):  
Agathe Franck ◽  
Jeanne Lainé ◽  
Gilles Moulay ◽  
Eline Lemerle ◽  
Michaël Trichet ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Cell Biology ◽  
Striated Muscle ◽  
Three Dimensional ◽  
Cell Types ◽  
Contractile Apparatus ◽  
Cortical Actin ◽  
Muscle Formation ◽  
And Function ◽  
Dynamin 2

Clathrin plaques are stable features of the plasma membrane observed in several cell types. They are abundant in muscle, where they localize at costameres that link the contractile apparatus to the sarcolemma and connect the sarcolemma to the basal lamina. Here, we show that clathrin plaques and surrounding branched actin filaments form microdomains that anchor a three-dimensional desmin intermediate filament (IF) web. Depletion of clathrin plaque and branched actin components causes accumulation of desmin tangles in the cytoplasm. We show that dynamin 2, whose mutations cause centronuclear myopathy (CNM), regulates both clathrin plaques and surrounding branched actin filaments, while CNM-causing mutations lead to desmin disorganization in a CNM mouse model and patient biopsies. Our results suggest a novel paradigm in cell biology, wherein clathrin plaques act as platforms capable of recruiting branched cortical actin, which in turn anchors IFs, both essential for striated muscle formation and function.

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