scholarly journals Microtubule-based actin transport and localization in a spherical cell

2020 ◽  
Vol 7 (11) ◽  
pp. 201730
Author(s):  
Marco Saltini ◽  
Bela M. Mulder
Keyword(s):  
Actin Filaments ◽  
Cell Polarization ◽  
Spherical Cell ◽  
Cell Cortex ◽  
Biomolecular Systems ◽  
Cellular Processes ◽  
Synthetic Cells ◽  
Underlying Mechanisms ◽  
Cellular Cytoskeleton

The interaction between actin filaments and microtubules is crucial for many eukaryotic cellular processes, such as, among others, cell polarization, cell motility and cellular wound healing. The importance of this interaction has long been recognized, yet very little is understood about both the underlying mechanisms and the consequences for the spatial (re)organization of the cellular cytoskeleton. At the same time, understanding the causes and the consequences of the interaction between different biomolecular components are key questions for in vitro research involving reconstituted biomolecular systems, especially in the light of current interest in creating minimal synthetic cells. In this light, recent in vitro experiments have shown that the actin-microtubule interaction mediated by the cytolinker TipAct, which binds to actin lattice and microtubule tips, causes the directed transport of actin filaments. We develop an analytical theory of dynamically unstable microtubules, nucleated from the centre of a spherical cell, in interaction with actin filaments. We show that, depending on the balance between the diffusion of unbound actin filaments and propensity to bind microtubules, actin is either concentrated in the centre of the cell, where the density of microtubules is highest, or becomes localized to the cell cortex.

scholarly journals The actin-binding ERM protein Moesin binds to and stabilizes microtubules at the cell cortex

2013 ◽  
Vol 202 (2) ◽  
pp. 251-260 ◽  
Author(s):  
Sara Solinet ◽  
Kazi Mahmud ◽  
Shannon F. Stewman ◽  
Khaled Ben El Kadhi ◽  
Barbara Decelle ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Metastatic Potential ◽  
Actin Binding ◽  
Cell Cortex ◽  
Shape Transformation ◽  
Erm Proteins ◽  
Cellular Processes ◽  
Anaphase Onset

Ezrin, Radixin, and Moesin (ERM) proteins play important roles in many cellular processes including cell division. Recent studies have highlighted the implications of their metastatic potential in cancers. ERM’s role in these processes is largely attributed to their ability to link actin filaments to the plasma membrane. In this paper, we show that the ERM protein Moesin directly binds to microtubules in vitro and stabilizes microtubules at the cell cortex in vivo. We identified two evolutionarily conserved residues in the FERM (4.1 protein and ERM) domains of ERMs that mediated the association with microtubules. This ERM–microtubule interaction was required for regulating spindle organization in metaphase and cell shape transformation after anaphase onset but was dispensable for bridging actin filaments to the metaphase cortex. These findings provide a molecular framework for understanding the complex functional interplay between the microtubule and actin cytoskeletons mediated by ERM proteins in mitosis and have broad implications in both physiological and pathological processes that require ERMs.

scholarly journals MiRNA-143 mediates the proliferative signaling pathway of FSH and regulates estradiol production

2017 ◽  
Vol 234 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Li Zhang ◽  
XiaoXin Zhang ◽  
Xuejing Zhang ◽  
Yu Lu ◽  
Lei Li ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Granulosa Cell ◽  
Granulosa Cells ◽  
Loss Of Function ◽  
Cellular Processes ◽  
Cell Functions ◽  
Genes Expression ◽  
Underlying Mechanisms

MicroRNAs (MiRNAs) play important regulatory roles in many cellular processes. MiR-143 is highly enriched in the mouse ovary, but its roles and underlying mechanisms are not well understood. In the current study, we show that miR-143 is located in granulosa cells of primary, secondary and antral follicles. To explore the specific functions of miR-143, we transfected miR-143 inhibitor into primary cultured granulosa cells to study the loss of function of miR-143 and the results showed that miR-143 silencing significantly increased estradiol production and steroidogenesis-related gene expression. Moreover, our in vivo and in vitro studies showed that follicular stimulating hormone (FSH) significantly decreased miR-143 expression. This function of miR-143 is accomplished by its binding to the 3’-UTR of KRAS mRNA. Furthermore, our results demonstrated that miR-143 acts as a negative regulating molecule mediating the signaling pathway of FSH and affecting estradiol production by targeting KRAS. MiR-143 also negatively acts in regulating granulosa cells proliferation and cell cycle-related genes expression. These findings indicate that miR-143 plays vital roles in FSH-induced estradiol production and granulosa cell proliferation, providing a novel mechanism that involves miRNA in regulating granulosa cell functions.

scholarly journals Proline-rich tyrosine kinase2 is involved in F-actin organization during in vitro maturation of rat oocyte

Reproduction ◽  
2006 ◽  
Vol 132 (6) ◽  
pp. 859-867 ◽  
Author(s):  
Xiao-Qian Meng ◽  
Ke-Gang Zheng ◽  
Yong Yang ◽  
Man-Xi Jiang ◽  
Yan-Ling Zhang ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Actin Filaments ◽  
Laser Scanning ◽  
Polar Body ◽  
Laser Scanning Microscopy ◽  
Meiotic Spindle ◽  
Confocal Laser ◽  
Cell Cortex ◽  
First Polar Body

Microfilaments (actin filaments) regulate various dynamic events during meiotic maturation. Relatively, little is known about the regulation of microfilament organization in mammalian oocytes. Proline-rich tyrosine kinase2 (Pyk2), a protein tyrosine kinase related to focal adhesion kinase (FAK) is essential in actin filaments organization. The present study was to examine the expression and localization of Pyk2, and in particular, its function during rat oocyte maturation. For the first time, by using Western blot and confocal laser scanning microscopy, we detected the expression of Pyk2 in rat oocytes and found that Pyk2 and Try402 phospho-Pyk2 were localized uniformly at the cell cortex and surrounded the germinal vesicle (GV) or the condensed chromosomes at the GV stage or after GV breakdown. At the metaphase and the beginning of anaphase, Pyk2 distributed asymmetrically both in the ooplasm and the cortex with a marked staining associated with the chromosomes and the region overlying the meiotic spindle. At telophase, Pyk2 was observed in the cleavage furrows in addition to its cortex and cytoplasm localization. The dynamics of Pyk2 were similar to that of F-actin, and this kinase was found to co-localize with microfilaments in several developmental stages during rat oocyte maturation. Microinjection of Pyk2 antibody demolished the microfilaments assembly and also inhibited the first polar body (PB1) emission. These findings suggest an important role of Pyk2 for rat oocyte maturation by regulating the organization of actin filaments.

scholarly journals A barbed end interference mechanism reveals how capping protein promotes nucleation in branched actin networks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Johanna Funk ◽  
Felipe Merino ◽  
Matthias Schaks ◽  
Klemens Rottner ◽  
Stefan Raunser ◽  
...  
Keyword(s):  
Structural Biology ◽  
Actin Filaments ◽  
Actin Network ◽  
Essential Factor ◽  
Actin Networks ◽  
Capping Protein ◽  
Cellular Processes ◽  
In Vitro Reconstitution ◽  
Interference Mechanism

AbstractHeterodimeric capping protein (CP/CapZ) is an essential factor for the assembly of branched actin networks, which push against cellular membranes to drive a large variety of cellular processes. Aside from terminating filament growth, CP potentiates the nucleation of actin filaments by the Arp2/3 complex in branched actin networks through an unclear mechanism. Here, we combine structural biology with in vitro reconstitution to demonstrate that CP not only terminates filament elongation, but indirectly stimulates the activity of Arp2/3 activating nucleation promoting factors (NPFs) by preventing their association to filament barbed ends. Key to this function is one of CP’s C-terminal “tentacle” extensions, which sterically masks the main interaction site of the terminal actin protomer. Deletion of the β tentacle only modestly impairs capping. However, in the context of a growing branched actin network, its removal potently inhibits nucleation promoting factors by tethering them to capped filament ends. End tethering of NPFs prevents their loading with actin monomers required for activation of the Arp2/3 complex and thus strongly inhibits branched network assembly both in cells and reconstituted motility assays. Our results mechanistically explain how CP couples two opposed processes—capping and nucleation—in branched actin network assembly.

Analysis of Cytoskeleton-Destabilizing Agents by Optimized Optical Navigation and AFM Force Measurements

2010 ◽  
Vol 18 (2) ◽  
pp. 34-37 ◽  
Author(s):  
A. Berquand ◽  
A. Holloschi ◽  
M. Trendelenburg ◽  
P. Kioschis
Keyword(s):  
Cancer Cells ◽  
Actin Filaments ◽  
Elastic Moduli ◽  
Ex Vivo ◽  
Optical Navigation ◽  
Force Measurements ◽  
Cellular Processes ◽  
Physical Interactions ◽  
Cellular Pathology

Mechanical properties of cells are determined by the dynamic behavior of the cytoskeleton and physical interactions with the environment. The cytoskeleton, composed of actin filaments, intermediate filaments, and microtubules, is vital for numerous key cellular processes, such as cell division, vesicle trafficking, cell contraction, cell motility, and cell signaling. There is increasing evidence that deregulation of cytoskeletal components like disassembly of actin and tubulin filaments is an important parameter in cellular pathology. Thus, significant alterations of the mechanical phenotype of the cell and its surrounding microenvironment are reported to be involved in aberrant cellular processes and successively contribute to onset and progression of diseases such as cancer, malaria, and possibly neurodegeneration. In vitro and ex vivo biomechanical studies have shown that cancer cells have significantly decreased elastic moduli than their normal counterparts, a characteristic that is attributed to the ability of cancer cells to metastasize or spread.

Actin Dynamics, Architecture, and Mechanics in Cell Motility

2014 ◽  
Vol 94 (1) ◽  
pp. 235-263 ◽  
Author(s):  
Laurent Blanchoin ◽  
Rajaa Boujemaa-Paterski ◽  
Cécile Sykes ◽  
Julie Plastino
Keyword(s):  
Mechanical Properties ◽  
Actin Filaments ◽  
Molecular Motor ◽  
Actin Dynamics ◽  
Tight Coupling ◽  
Actin Organization ◽  
Cellular Processes ◽  
Shock Absorbers ◽  
Cellular Environment

Tight coupling between biochemical and mechanical properties of the actin cytoskeleton drives a large range of cellular processes including polarity establishment, morphogenesis, and motility. This is possible because actin filaments are semi-flexible polymers that, in conjunction with the molecular motor myosin, can act as biological active springs or “dashpots” (in laymen's terms, shock absorbers or fluidizers) able to exert or resist against force in a cellular environment. To modulate their mechanical properties, actin filaments can organize into a variety of architectures generating a diversity of cellular organizations including branched or crosslinked networks in the lamellipodium, parallel bundles in filopodia, and antiparallel structures in contractile fibers. In this review we describe the feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro, then we integrate this knowledge into our current understanding of cellular actin organization and its physiological roles.

scholarly journals Enhancement of Actin-depolymerizing Factor/Cofilin-dependent Actin Disassembly by Actin-interacting Protein 1 Is Required for Organized Actin Filament Assembly in the Caenorhabditis elegans Body Wall Muscle

2006 ◽  
Vol 17 (5) ◽  
pp. 2190-2199 ◽  
Author(s):  
Kurato Mohri ◽  
Kanako Ono ◽  
Robinson Yu ◽  
Sawako Yamashiro ◽  
Shoichiro Ono
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Muscle Cells ◽  
Actin Depolymerizing Factor ◽  
Interacting Protein ◽  
Cellular Processes ◽  
Cytoskeletal Dynamics ◽  
End Capping

Regulated disassembly of actin filaments is involved in several cellular processes that require dynamic rearrangement of the actin cytoskeleton. Actin-interacting protein (AIP) 1 specifically enhances disassembly of actin-depolymerizing factor (ADF)/cofilin-bound actin filaments. In vitro, AIP1 actively disassembles filaments, caps barbed ends, and binds to the side of filaments. However, how AIP1 functions in the cellular actin cytoskeletal dynamics is not understood. We compared biochemical and in vivo activities of mutant UNC-78 proteins and found that impaired activity of mutant UNC-78 proteins to enhance disassembly of ADF/cofilin-bound actin filaments is associated with inability to regulate striated organization of actin filaments in muscle cells. Six functionally important residues are present in the N-terminal β-propeller, whereas one residue is located in the C-terminal β-propeller, suggesting the presence of two separate sites for interaction with ADF/cofilin and actin. In vitro, these mutant UNC-78 proteins exhibited variable alterations in actin disassembly and/or barbed end-capping activities, suggesting that both activities are important for its in vivo function. These results indicate that the actin-regulating activity of AIP1 in cooperation with ADF/cofilin is essential for its in vivo function to regulate actin filament organization in muscle cells.

scholarly journals The Rho-GEF Gef3 interacts with the septin complex and activates the GTPase Rho4 during fission yeast cytokinesis

2015 ◽  
Vol 26 (2) ◽  
pp. 238-255 ◽  
Author(s):  
Ning Wang ◽  
Mo Wang ◽  
Yi-Hua Zhu ◽  
Timothy W. Grosel ◽  
Daokun Sun ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Cell Polarization ◽  
Nucleotide Exchange ◽  
Cellular Processes ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rho Gef

Rho GTPases, activated by Rho guanine nucleotide exchange factors (GEFs), are conserved molecular switches for signal transductions that regulate diverse cellular processes, including cell polarization and cytokinesis. The fission yeast Schizosaccharomyces pombe has six Rho GTPases (Cdc42 and Rho1–Rho5) and seven Rho GEFs (Scd1, Rgf1–Rgf3, and Gef1–Gef3). The GEFs for Rho2–Rho5 have not been unequivocally assigned. In particular, Gef3, the smallest Rho GEF, was barely studied. Here we show that Gef3 colocalizes with septins at the cell equator. Gef3 physically interacts with septins and anillin Mid2 and depends on them to localize. Gef3 coprecipitates with GDP-bound Rho4 in vitro and accelerates nucleotide exchange of Rho4, suggesting that Gef3 is a GEF for Rho4. Consistently, Gef3 and Rho4 are in the same genetic pathways to regulate septum formation and/or cell separation. In gef3∆ cells, the localizations of two potential Rho4 effectors—glucanases Eng1 and Agn1—are abnormal, and active Rho4 level is reduced, indicating that Gef3 is involved in Rho4 activation in vivo. Moreover, overexpression of active Rho4 or Eng1 rescues the septation defects of mutants containing gef3∆. Together our data support that Gef3 interacts with the septin complex and activates Rho4 GTPase as a Rho GEF for septation in fission yeast.

scholarly journals Copine A Interacts with Actin Filaments and Plays a Role in Chemotaxis and Adhesion

Cells ◽  
2019 ◽  
Vol 8 (7) ◽  
pp. 758 ◽  
Author(s):  
Matthew J. Buccilli ◽  
April N. Ilacqua ◽  
Mingxi Han ◽  
Andrew A. Banas ◽  
Elise M. Wight ◽  
...  
Keyword(s):  
Protein Function ◽  
Actin Filaments ◽  
Model Organism ◽  
Dependent Manner ◽  
Developmental Defects ◽  
Calcium Dependent ◽  
Cellular Processes ◽  
Eukaryotic Organisms ◽  
Von Willebrand

Copines make up a family of calcium-dependent, phospholipid-binding proteins found in numerous eukaryotic organisms. Copine proteins consist of two C2 domains at the N-terminus followed by an A domain similar to the von Willebrand A domain found in integrins. We are studying copine protein function in the model organism, Dictyostelium discoideum, which has six copine genes, cpnA-cpnF. Previous research showed that cells lacking the cpnA gene exhibited a cytokinesis defect, a contractile vacuole defect, and developmental defects. To provide insight into the role of CpnA in these cellular processes, we used column chromatography and immunoprecipitation to isolate proteins that bind to CpnA. These proteins were identified by mass spectrometry. One of the proteins identified was actin. Purified CpnA was shown to bind to actin filaments in a calcium-dependent manner in vitro. cpnA− cells exhibited defects in three actin-based processes: chemotaxis, cell polarity, and adhesion. These results suggest that CpnA plays a role in chemotaxis and adhesion and may do so by interacting with actin filaments.

scholarly journals Synergies between Aip1p and capping protein subunits (Acp1p and Acp2p) in clathrin-mediated endocytosis and cell polarization in fission yeast

2014 ◽  
Vol 25 (22) ◽  
pp. 3515-3527 ◽  
Author(s):  
Julien Berro ◽  
Thomas D. Pollard
Keyword(s):  
Fission Yeast ◽  
Actin Filaments ◽  
Cell Polarization ◽  
Cellular Functions ◽  
Protein Subunits ◽  
Capping Protein ◽  
New Methods ◽  
Data Alignment

Aip1p cooperates with actin-depolymerizing factor (ADF)/cofilin to disassemble actin filaments in vitro and in vivo, and is proposed to cap actin filament barbed ends. We address the synergies between Aip1p and the capping protein heterodimer Acp1p/Acp2p during clathrin-mediated endocytosis in fission yeast. Using quantitative microscopy and new methods we have developed for data alignment and analysis, we show that heterodimeric capping protein can replace Aip1p, but Aip1p cannot replace capping protein in endocytic patches. Our quantitative analysis reveals that the actin meshwork is organized radially and is compacted by the cross-linker fimbrin before the endocytic vesicle is released from the plasma membrane. Capping protein and Aip1p help maintain the high density of actin filaments in meshwork by keeping actin filaments close enough for cross-linking. Our experiments also reveal new cellular functions for Acp1p and Acp2p independent of their capping activity. We identified two independent pathways that control polarization of endocytic sites, one depending on acp2+ and aip1+ during interphase and the other independent of acp1+, acp2+, and aip1+ during mitosis.

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