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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. Non-sarcomeric 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...
March 8, 2018: Cytoskeleton
P W Gunning, E C Hardeman
No abstract text is available yet for this article.
March 7, 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...
March 3, 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...
February 21, 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...
January 23, 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 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...
January 6, 2018: Cytoskeleton
Tianchen Hu, Philip V Bayly
It remains unclear how flagella generate propulsive, oscillatory waveforms. While it is well known that dynein motors, in combination with passive cytoskeletal elements, drive the bending of the axoneme by applying shearing forces and bending moments to microtubule doublets, the origin of rhythmicity is still mysterious. Most conceptual models of flagellar oscillation involve dynein regulation or switching, so that dynein activity first on one side of the axoneme, then the other, drives bending. In contrast, a "viscoelastic flutter" mechanism has recently been proposed, based on a dynamic structural instability...
January 5, 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 paper, 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...
December 22, 2017: 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...
December 21, 2017: 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
Yan Feng, Sorin Mitran
A beam element is constructed for microtubules based upon data reduction of the results from atomistic simulation of the carbon backbone chain of αβ-tubulin dimers. The database of mechanical responses to various types of loads from atomistic simulation is reduced to dominant modes. The dominant modes are subsequently used to construct the stiffness matrix of a beam element that captures the anisotropic behavior and deformation mode coupling that arises from a microtubule's spiral structure. In contrast to standard Euler-Bernoulli or Timoshenko beam elements, the link between forces and node displacements results not from hypothesized deformation behavior, but directly from the data obtained by molecular scale simulation...
February 2018: Cytoskeleton
M S Budamagunta, F Guo, N Sun, B Shibata, P G FitzGerald, J C Voss, J F Hess
Proteins predicted to be composed of large stretches of coiled-coil structure have often proven difficult to crystallize for structural determination. We have successfully applied EPR spectroscopic techniques to the study of the structure and assembly of full-length human vimentin assembled into native 11 nm filaments, in physiologic solution, circumventing the limitations of crystallizing shorter peptide sequences. Tektins are a small family of highly alpha helical filamentous proteins found in the doublet microtubules of cilia and related structures...
January 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 associated with significantly reduced sperm number and motility...
December 13, 2017: Cytoskeleton
Syamalima Dube, Lynn Abbott, Samender Randhawa, Yingli Fan, Jushuo Wang, Jean M Sanger, Joseph W Sanger, Bernard J Poiesz, Dipak K Dube
Cloning and sequencing of various tropomyosin isoforms expressed in chickens have been described since the early 1980s. However, to the best of our knowledge, this is the first report on the molecular characterization and the expression of the sarcomeric isoform of the TPM3 gene in cardiac and skeletal muscles from developing as well as adult chickens. Expression of TPM3α was performed by conventional RT-PCR as well as qRT-PCR using relative expression (by ΔCT as well as ΔΔCT methods) and by determining absolute copy number...
December 8, 2017: Cytoskeleton
Janice E Friend, Wasim A Sayyad, Rajesh Arasada, Chad D McCormick, John E Heuser, Thomas D Pollard
Myosin-II is required for the assembly and constriction of cytokinetic contractile rings in fungi and animals. We used electron microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS) to characterize the physical properties of Myo2 from fission yeast Schizosaccharomyces pombe. By electron microscopy, Myo2 has two heads and a coiled-coiled tail like myosin-II from other species. The first 65 nm of the tail is a stiff rod, followed by a flexible, less-ordered region up to 30 nm long...
December 4, 2017: Cytoskeleton
Dimitrios Vavylonis
No abstract text is available yet for this article.
December 1, 2017: Cytoskeleton
Makoto Suzuki, George Mogami, Hideyuki Ohsugi, Takahiro Watanabe, Nobuyuki Matubayasi
We propose a driving force hypothesis based on previous thermodynamics, kinetics and structural data as well as additional experiments and calculations presented here on water-related phenomena in the actomyosin systems. Although Szent-Györgyi pointed out the importance of water in muscle contraction in 1951, few studies have focused on the water science of muscle because of the difficulty of analyzing hydration properties of the muscle proteins, actin, and myosin. The thermodynamics and energetics of muscle contraction are linked to the water-mediated regulation of protein-ligand and protein-protein interactions along with structural changes in protein molecules...
December 2017: Cytoskeleton
Mahito Kikumoto, Fumio Oosawa
We measured the critical concentration of actin polymerized with different polymerization ions and bound divalent cations at low temperatures and estimated thermodynamic parameters. The entropy and enthalpy changes of actin polymerization were 36-55 (cal/mol K) and 2-8 (kcal/mol), respectively, with some exceptions. Both the entropy and enthalpy changes of the polymerization of Ca2+ -actin were sensitive to the polymerization ion (K+ or Na+ ): ΔS = 39 or 36 (cal/mol K), ΔΗ= 3.9 or 2.7 (kcal/mol). The entropy and enthalpy changes (cal/mol K, kcal/mol) of Mg2+ -actin were also sensitive to the polymerization ion in the following order: Mg2+ (55, 7...
December 2017: Cytoskeleton
Rika Hirakawa, Yusuke Nishikawa, Taro Q P Uyeda, Kiyotaka Tokuraku
Heavy meromyosin (HMM) forms clusters along actin filaments under low ATP concentrations. Here, we observed the growth of HMM clusters under low concentrations of ATP in real time using fluorescence microscopy. When actin filaments were loosely immobilized on positively charged lipid bilayers, clusters of HMM-GFP were readily formed. Time-lapse observation revealed that the clusters grew unidirectionally. When we used a mixture of actin filaments and copolymers of actin and acto-S1dC, a chimeric protein of actin and the myosin motor domain, HMM-GFP preferentially formed clusters along the copolymers...
December 2017: Cytoskeleton
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