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Jushuo Wang, Yingli Fan, Jean M Sanger, Joseph W Sanger
De novo assembly of contractile myofibrils begins with the formation of premyofibrils where filaments of non-muscle myosin (NM II), and actin organize in sarcomeric patterns with Z-Bodies containing muscle-specific alpha-actinin. Interactions of muscle specific myosin (MM II) with NM II occur in a nascent myofibril stage that precedes the assembly of mature myofibrils. By the final stage of myofibrillogenesis, the only myosin II present in the mature myofibrils is MM II. In this current study of myofibril assembly, the three vertebrate isoforms of NM II (A, B, and C) and sarcomeric alpha-actinin, ligated to GFP family proteins, were coexpressed in avian embryonic skeletal and cardiac muscle cells...
May 21, 2018: Cytoskeleton
Camilla B Mitchell, Justine R Stehn, Geraldine M O'Neill
The migration and invasion of cells through tissues in the body is facilitated by a dynamic actin cytoskeleton. The actin-associating protein, tropomyosin Tpm3.1 has emerged to play important roles in cell migration and invasion. To date, investigations have focused on single cell migration and invasion where Tpm3.1 expression is inversely associated with Rac GTPase-mediated cell invasion. While single cell and collective cell invasion have many features in common, collective invasion is additionally impacted by cell-cell adhesion, and the role of Tpm3...
May 12, 2018: Cytoskeleton
Damián Lobato-Márquez, Sina Krokowski, Andrea Sirianni, Gerald Larrouy-Maumus, Serge Mostowy
Shigella flexneri, a Gram-negative enteroinvasive pathogen, causes inflammatory destruction of the human intestinal epithelium. During infection of epithelial cells, Shigella escape from the phagosome to the cytosol, where they reroute host cell glycolysis to obtain nutrients for proliferation. Septins, a poorly understood component of the cytoskeleton, can entrap cytosolic Shigella targeted to autophagy in cage-like structures to restrict bacterial proliferation. Although bacterial entrapment by septin caging has been the subject of intense investigation, the role of septins and the autophagy machinery in the proliferation of non-caged Shigella is mostly unknown...
May 12, 2018: Cytoskeleton
Megha Abbey, Matthias Gaestel, Manoj B Menon
Septins are conserved cytoskeletal proteins with unique filament forming capabilities and roles in cytokinesis and cell morphogenesis. Septins undergo hetero-oligomerization and assemble into higher order structures including filaments, rings and cages. Hetero- and homotypic interactions of septin isoforms involve alternating GTPase (G)-domain interfaces and those mediated by N- and C-terminal extensions. While most septins bind GTP, display weak GTP-hydrolysis activity and incorporate guanine nucleotides in their interaction interfaces, studies using GTPase-inactivating mutations have failed to conclusively establish a crucial role for GTPase activity in mediating septin functions...
May 10, 2018: Cytoskeleton
Keren Tazat, Susanne Schindler, Reinhard Deppeing, Nicola J Mabjeesh
We have shown previously that septin 9 isoform 1 (SEPT9_i1) protein associates with hypoxia-inducible factor (HIF)-1α to augment HIF-1 transcriptional activity by driving its importin-α-mediated nuclear translocation. Using in vitro and in vivo binding assays we identified that HIF-1α interacts with importin-α5 and importin-α7 in prostate cancer cells but only importin-α7 interacts with SEPT9_i1. The interaction with importin-α7 was dependent on the first 25 amino acids of SEPT9_i1 that are unique compared to other members of the mammalian septin family...
May 9, 2018: Cytoskeleton
Matt Greenlee, Annabel Alonso, Maliha Rahman, Nida Meednu, Kayla Davis, Victoria Tabb, River Cook, Rita K Miller
Stu2p is the yeast member of the XMAP215/Dis1/ch-TOG family of microtubule-associated proteins that promote microtubule polymerization. However, the factors that regulate its activity are not clearly understood. Here we report that Stu2p in the budding yeast Saccharomyces cerevisiae interacts with SUMO by covalent and non-covalent mechanisms. Stu2p interacted by two-hybrid analysis with the yeast SUMO Smt3p, its E2 Ubc9p, and the E3 Nfi1p. A region of Stu2p containing the dimerization domain was both necessary and sufficient for interaction with SUMO and Ubc9p...
May 5, 2018: Cytoskeleton
J Daniel Fenn, Paula C Monsma, Anthony Brown
Neurofilaments are flexible cytoskeletal polymers that are capable of folding and unfolding between their bouts of bidirectional movement along axons. Here we present a detailed characterization of this behavior in cultured neurons using kymograph analysis with 30 ms temporal resolution. We analyzed 781 filaments ranging from 0.6-42 µm in length. We observed complex behaviors including pinch folds, hairpin folds, orientation changes (flips), and occasional severing and annealing events. On average, the filaments spent approximately 40% of their time in some sort of folded configuration...
April 23, 2018: Cytoskeleton
Jiayan Guo, Hong Seok Kim, Reto Asmis, Richard F Ludueña
Microtubules are a major component of the neuronal cytoskeleton. Tubulin, the subunit protein of microtubules, is an α/β heterodimer. Both α and β exist as families of isotypes, whose members are encoded by different genes and have different amino acid sequences. The βII and βIII isotypes are very prominent in the nervous system. Our previous work has suggested that βII may play a role in neuronal differentiation, but the role of βIII in neurons is not well understood. In the work reported here, we examined the roles of the different β-tubulin isotypes in response to glutamate/glycine treatment, and found that both βII and βIII bind to glutathione in the presence of ROS, especially βIII...
April 16, 2018: Cytoskeleton
Harald Preisner, Jörn Habicht, Sriram G Garg, Sven B Gould
Metazoans evolved from a single protist lineage. While all eukaryotes share a conserved actin and tubulin-based cytoskeleton, it is commonly perceived that intermediate filaments (IFs), including lamin, vimentin or keratin among many others, are restricted to metazoans. Actin and tubulin proteins are conserved enough to be detectable across all eukaryotic genomes using standard phylogenetic methods, but IF proteins, in contrast, are notoriously difficult to identify by such means. Since the 1950s, dozens of cytoskeletal proteins in protists have been identified that seemingly do not belong to any of the IF families described for metazoans, yet, from a structural and functional perspective fit criteria that define metazoan IF proteins...
March 23, 2018: Cytoskeleton
Maiko Kitaoka, Rebecca Heald, Romain Gibeaux
Egg extracts of the African clawed frog Xenopus laevis have provided a cell-free system instrumental in elucidating events of the cell cycle, including mechanisms of spindle assembly. Comparison with extracts from the diploid Western clawed frog, Xenopus tropicalis, which is smaller at the organism, cellular and subcellular levels, has enabled the identification of spindle size scaling factors. We set out to characterize the Marsabit clawed frog, Xenopus borealis, which is intermediate in size between the two species, but more recently diverged in evolution from X...
March 23, 2018: Cytoskeleton
Cynthia P Hsu, Behzad Moghadaszadeh, John H Hartwig, Alan H Beggs
The α-actinin proteins are a highly conserved family of actin crosslinkers that mediate interactions between several cytoskeletal and sarcomeric proteins. Nonsarcomeric α-actinin-1 and α-actinin-4 crosslink actin filaments in the cytoskeleton, while sarcomeric α-actinin-2 and α-actinin-3 serve a crucial role in anchoring actin filaments to the muscle Z-line. To assess the difference in turnover dynamics and structure/function properties between the α-actinin isoforms at the sarcomeric Z-line, we used Fluorescence Recovery After Photobleaching (FRAP) in primary myofiber cultures...
May 2018: Cytoskeleton
Sandeep M Nalluri, Joseph W O'Connor, Gage A Virgi, Samantha E Stewart, Dan Ye, Esther W Gomez
Epithelial-mesenchymal transition (EMT) is an important process that mediates organ development and wound healing, and in pathological contexts, it can contribute to the progression of fibrosis and cancer. During EMT, cells exhibit marked changes in cytoskeletal organization and increased expression of a variety of actin associated proteins. Here, we sought to determine the role of caldesmon in mediating EMT in response to transforming growth factor (TGF)-β1. We find that the expression level and phosphorylation state of caldesmon increase as a function of time following induction of EMT by TGFβ1 and these changes in caldesmon correlate with increased focal adhesion number and size and increased cell contractility...
May 2018: Cytoskeleton
P W Gunning, E C Hardeman
No abstract text is available yet for this article.
April 2018: Cytoskeleton
Bipasha Barua, Maria Sckolnick, Howard D White, Kathleen M Trybus, Sarah E Hitchcock-DeGregori
Muscle contraction, cytokinesis, cellular movement, and intracellular transport depend on regulated actin-myosin interaction. Most actin filaments bind one or more isoform of tropomyosin, a coiled-coil protein that stabilizes the filaments and regulates interactions with other actin-binding proteins, including myosin. Isoform-specific allosteric regulation of muscle myosin II by actin-tropomyosin is well-established while that of processive myosins, such as myosin V, which transport organelles and macromolecules in the cell periphery, is less certain...
April 2018: Cytoskeleton
Anastassiia Vertii, Paul D Kaufman, Heidi Hehnly, Stephen Doxsey
Traditionally, we imagine that cell division gives rise to two identical daughter cells. Nevertheless, all cell divisions, to some degree, display asymmetry. Asymmetric cell division is defined as the generation of two daughter cells with different physical content and/or developmental potential. Several organelles and cellular components including the centrosome, non-coding RNA, chromatin, and recycling endosomes are involved in the process of asymmetric cell division. Disruption of this important process is known to induce profound defects in development, the immune response, regeneration of tissues, aging, and cancer...
March 2018: Cytoskeleton
Mary T Doolin, Kimberly M Stroka
The in vivo microenvironment is critical for providing physico-chemical signaling cues which ultimately regulate human mesenchymal stem cell (hMSC) behavior in clinically-relevant applications. hMSCs experience mechanical confinement of the cell body and nucleus in three dimensional (3D) tissues during homing and in porous tissue engineered scaffolds, yet the effects of this mechanical cue on hMSC migration are not known. Here, we use a microchannel device to systematically examine the effect of confinement on hMSC migration and cytoskeletal organization...
March 2018: Cytoskeleton
Amir Shamloo, Behzad Mehrafrooz
Actin is known as the most abundant essentially protein in eukaryotic cells. Actin plays a crucial role in many cellular processes involving mechanical forces such as cell motility, adhesion, muscle contraction, and intracellular transport. However, little is known about the mechanical properties of this protein when subjected to mechanical forces in cellular processes. In this article, a series of large-scale molecular dynamics simulations are carried out to elucidate nanomechanical behavior such as elastic and viscoelastic properties of a single actin filament...
March 2018: Cytoskeleton
Yuka Yamagishi, Hiroshi Abe
During Xenopus oocyte maturation, the microtubule organizing center and transient microtubule array (MTOC-TMA) forms at the vegetal side of the nucleus and we have previously demonstrated that this formation requires actin reorganization. However, the molecular mechanism that coordinates actin filaments with microtubules (MTs) during oocyte maturation is unknown. Here we show that the actin nucleation promoting factor WASH is involved in MTOC-TMA assembly. WASH depletion disrupted the alignment of actin filaments and MT at the base of MTOC-TMA...
March 2018: Cytoskeleton
Yong Zhang, Hong Liu, Wei Li, Zhengang Zhang, Shiyang Zhang, Maria E Teves, Courtney Stevens, James A Foster, Gregory E Campbell, Jolene J Windle, Rex A Hess, Gregory J Pazour, Zhibing Zhang
Intraflagellar transport (IFT) is a conserved mechanism essential for the assembly and maintenance of most eukaryotic cilia and flagella. However, little is known about its role in sperm flagella formation and male fertility. IFT140 is a component of IFT-A complex. In mouse, it is highly expressed in the testis. Ift140 gene was inactivated specifically in mouse spermatocytes/spermatids. The mutant mice did not show any gross abnormalities, but all were infertile and associated with significantly reduced sperm number and motility...
February 2018: Cytoskeleton
Xuan Liang, Sajini Kiru, Guillermo A Gomez, Alpha S Yap
Adherens junctions in epithelia are contractile structures, where coupling of adhesion to the actomyosin cytoskeleton generates mechanical tension for morphogenesis and homeostasis. In established monolayers, junctional contractility is supported by the interplay between cell signals and scaffolding proteins. However, less is known about how contractile junctions develop, especially during the establishment of epithelial monolayers. Here, we show that junctional tension increases concomitant with accumulation of actomyosin networks as Caco-2 epithelia become confluent...
February 2018: Cytoskeleton
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