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Lydia Smith, Paul Maddox
In the last decade, computational processing of big datasets has facilitated the analyses of unprecedented quantities of biological data. Thus, automation and big data analysis have been revolutionary in detecting and quantifying subtle phenotypes in cell biological contexts. Analyzing similar quantities of data in larger and more complicated biological systems such as developing embryos has been more challenging due to experimental limitations on both ensemble data collection and analysis. These challenges include photosensitivity of living samples and of the fluorescently-tagged proteins under study, collectively limiting the number of images that can be acquired in a single time-lapse series...
September 10, 2018: Cytoskeleton
Adriano Vissa, Maximiliano Giuliani, Carol D Froese, Moshe S Kim, Forooz Soroor, Peter K Kim, William S Trimble, Christopher M Yip
Septins are a conserved family of GTPases that associate with numerous components of the cytoskeleton and the inner leaflet of the plasma membrane. These proteins are involved in many biological processes including cell division and membrane trafficking, and serving as a scaffolding component of the cytoskeleton used to recruit other proteins and form diffusion barriers to maintain the composition of membrane domains. In order to carry out their cellular functions, septins undergo interactions via their NC or G interfaces to form heteromeric rod-like structures that can polymerize into filaments and associate laterally into bundles...
September 3, 2018: Cytoskeleton
Siddheshwari Advani, Thomas J Maresca, Jennifer L Ross
Current methods to disrupt the microtubule cytoskeleton do not easily provide rapid, local control with standard cell manipulation reagents. Here, we develop a new microtubule-disruption tool based on katanin p60 severing activity and demonstrate proof-of-principle by targeting it to kinetochores in Drosophila melanogaster S2 cells. Specifically, we show that human katanin p60 can remove microtubule polymer mass in S2 cells and an increase in misaligned chromosomes when globally overexpressed. When targeted to the kinetochores via Mis12, we were able to recapitulate the misalignment only when using a phosphorylation-resistant mutant...
September 3, 2018: Cytoskeleton
Stephen M King
Ciliary and flagellar motility is caused by the ensemble action of inner and outer dynein arm motors acting on axonemal doublet microtubules. The switch point or switching hypothesis, for which much experimental and computational evidence exists, requires that dyneins on only one side of the axoneme are actively working during bending, and that this active motor region propagate along the axonemal length. Generation of a reverse bend results from switching active sliding to the opposite side of the axoneme...
September 3, 2018: Cytoskeleton
Alexander Zielinski, Christina Linnartz, Catharina Pleschka, Georg Dreissen, Ronald Springer, Rudolf Merkel, Bernd Hoffmann
Any cell within a tissue is constantly confronted with a variety of mechanical stimuli. Sensing of these diverse stimuli plays an important role in cellular regulation. Besides shear stress, cells of the vascular endothelium are particularly exposed to a permanent cyclic straining originating from the interplay of outwards pushing blood pressure and inwards acting contraction by smooth musculature. Perpendicular alignment of cells as structural adaptation to this condition is a basic prerequisite in order to withstand deformation forces...
September 3, 2018: Cytoskeleton
Alexander Mela, Michelle Momany
Septins are highly conserved GTP-binding proteins that are a component of the cytoskeletal systems of virtually all eukaryotes (except higher plants). Septins play important roles in a multitude of cellular processes, including cytokinesis, establishment of cell polarity, and cellular partitioning. The ease of genetic screens and a fully-sequenced genome have made Saccharomyces cerevisiae one of the most extensively studied and well-annotated model organisms in eukaryotic biology. Here we present a synopsis of the known point mutations in the seven S...
August 31, 2018: Cytoskeleton
Emily S Melzer, Caralyn E Sein, James J Chambers, M Sloan Siegrist
In many model organisms, diffuse patterning of cell wall peptidoglycan synthesis by the actin homolog MreB enables the bacteria to maintain their characteristic rod shape. In Caulobacter crescentus and Escherichia coli, MreB is also required to sculpt this morphology de novo. Mycobacteria are rod-shaped but expand their cell wall from discrete polar or sub-polar zones. In this genus, the tropomyosin-like protein DivIVA is required for the maintenance of cell morphology. DivIVA has also been proposed to direct peptidoglycan synthesis to the tips of the mycobacterial cell...
August 30, 2018: Cytoskeleton
Chun-Hsiang Lin, Yi-Ru Shen, Han-Yu Wang, Chi-Wu Chiang, Chia-Yih Wang, Pao-Lin Kuo
The sperm annulus, a septin-based ring structure, is important for reproductive physiology. It is composed of SEPT12-based septin core complex followed by assembling as octameric filament. In clinical examinations, mutations of Septin12 result in male infertility, immotile sperm, as well as sperm with defective annuli. The dynamic assembly of septin filaments is regulated by several posttranslational modifications, including sumoylation, acetylation, and phosphorylation. Here, we briefly review the biological significance and the regulation of SEPT12 phosphorylation in the mammalian sperm physiology...
August 30, 2018: Cytoskeleton
Eichi Watabe, Shoichiro Ono, Hidehito Kuroyanagi
Tropomyosin isoforms contribute to generation of functionally divergent actin filaments. In the nematode Caenorhabditis elegans, multiple isoforms are produced from lev-11, the single tropomyosin gene, by combination of two separate promoters and alternative pre-mRNA splicing. In this study, we report that alternative splicing of lev-11 is regulated in a tissue-specific manner so that a particular tropomyosin isoform is expressed in each tissue. Reverse-transcription polymerase chain reaction analysis of lev-11 mRNAs confirms five previously reported isoforms (LEV-11A, LEV-11C, LEV-11D, LEV-11E, and LEV-11O) and identifies a new sixth isoform LEV-11T...
August 29, 2018: Cytoskeleton
Konstantinos Nakos, Marshall Rosenberg, Elias T Spiliotis
Septins are GTP-binding proteins that associate with the microtubule (MT) and actin cytoskeleton. Septins affect MT organization and post-translational modifications, but their role in MT dynamics is less understood. Here, we reconstituted MT dynamics in the presence of the MT-binding septin (SEPT9) using an in vitro cell-free assay, which images the polymerization of tubulin from GMPCPP-stabilized MT seeds. We found that submicromolar concentrations of SEPT9 suppress MT catastrophe and enhance the growth of MT plus ends to great lengths, while low micromolar concentrations of SEPT9 stabilize MTs by inhibiting dynamic instability...
August 24, 2018: Cytoskeleton
Aidan M Fenix, Dylan T Burnette
How cellular contractile systems assemble has fascinated scientists for generations. The major molecule responsible for cellular force generation is the molecular motor, non-muscle myosin II (NMII). NMII molecules are organized into single myosin filaments and larger arrays of filaments called NMII I stacks, which are capable of generating increasing amounts of force. The textbook model of NMII stack assembly is the Network Contraction Model, where ensembles of distinct NMII filaments condense into a NMII stack by pulling on actin filaments...
August 20, 2018: Cytoskeleton
B J Mann, P Wadsworth
The mitotic spindle is a dynamic bipolar structure that mediates chromosome segregation in mitosis. In most organisms, spindle formation requires the action of kinesin-5 motor proteins that generate outward force on antiparallel microtubules to establish spindle bipolarity. Previous work has shown that Eg5 and TPX2, a spindle microtubule-associated protein that suppresses Eg5 motor activity, are enriched on parallel microtubules near spindle poles. This distribution is inconsistent with the requirement for Eg5-dependent force production during mitosis...
August 19, 2018: Cytoskeleton
Julian David Baur, Reinhild Rösler, Sebastian Wiese, Nils Johnsson, Thomas Gronemeyer
Septins are a conserved family of GTP-binding proteins that assemble into an ordered array of filaments at the mother bud neck in Saccharomyces cerevisiae cells. They are present in all higher eukaryotes except plants. Septins belong structurally to the P-Loop NTPases like Rab and Ras. However, unlike other small GTPases septins are supposed to act as scaffolds rather than signalling mediators. This is why they are considered as the fourth class of cytoskeletal proteins. It is assumed that septins fulfil their functions independently of the bound nucleotide...
August 9, 2018: Cytoskeleton
Maxine Lam, Fernando Calvo
Cells exist in dynamic three-dimensional environments where they experience variable mechanical forces due to their interaction with the extracellular matrix, neighboring cells and physical stresses. The ability to constantly and rapidly alter cellular behavior in response to the mechanical environment is therefore crucial for cell viability, tissue development and homeostasis. Mechanotransduction is the process whereby cells translate mechanical inputs into biochemical signals. These signals in turn adjust cell morphology and cellular functions as diverse as proliferation, differentiation, migration and apoptosis...
August 9, 2018: Cytoskeleton
Thomas Arnesen, Ronen Marmorstein, Roberto Dominguez
Humans express six highly conserved actin isoforms, which differ the most at their N-termini. Actin's N-terminus undergoes co- and post-translational processing unique among eukaryotic proteins. During translation, the initiator methionine of the two cytoplasmic isoforms is N-terminally acetylated (Nt-acetylated) and that of the four muscle isoforms is removed and the exposed cysteine is Nt-acetylated. Then, an unidentified acetylaminopeptidase post-translationally removes the Ac-Met (or Ac-Cys), and all six isoforms are re-acetylated at the N-terminus...
August 7, 2018: Cytoskeleton
Alexandre Beber, Maryam Alqabandi, Coline Prévost, Fanny Viars, Daniel Lévy, Patricia Bassereau, Aurélie Bertin, Stéphanie Mangenot
Septins constitute a novel class of cytoskeletal proteins. Budding yeast septins self-assemble into non-polar filaments bound to the inner plasma membrane through specific interactions with l-α-phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Biomimetic in vitro assays using giant unilamellar vesicles (GUVs) are relevant tools to dissect and reveal insights in proteins-lipids interactions, membrane mechanics and curvature sensitivity. GUVs doped with PI(4,5)P2 are challenging to prepare. This report is dedicated to optimize the incorporation of PI(4,5)P2 lipids into GUVs by probing the proteins-PI(4,5)P2 GUVs interactions...
August 1, 2018: Cytoskeleton
Karl F Lechtreck, Ilaria Mengoni, Batare Okivie, Kiersten B Hilderhoff
Radial spokes (RSs) are multiprotein complexes that regulate dynein activity. In the cell body, RS proteins (RSPs) are present in a 12S precursor, which enters the flagella and converts into the axoneme-bound 20S spokes consisting of a head and stalk. To study RS dynamics in vivo, we expressed fluorescent protein (FP)-tagged versions of the head protein RSP4 and the stalk protein RSP3 to rescue the corresponding Chlamydomonas mutants pf1, lacking spoke heads, and pf14, lacking RSs entirely. RSP3 and RSP4 mostly co-migrated by intraflagellar transport (IFT)...
August 1, 2018: Cytoskeleton
Katharina Neubauer, Björn Neubauer, Maximilian Seidl, Barbara Zieger
Chronic kidney disease (CKD) is characterized by the loss of nephrons and worsening organ-fibrosis that leads to deterioration and ultimately the total breakdown of kidney function. Renal fibrosis has become a major public health problem worldwide and necessitates hemodialysis and kidney transplantation in affected patients. CKD is mainly characterized by the activation and proliferation of interstitial fibroblasts and by excessive synthesis and accumulation of extracellular matrix components, causing the disruption of the normal tissue architecture of the kidney...
July 18, 2018: Cytoskeleton
Katharina Neubauer, Doris Böckelmann, Udo Koehler, Julia Kracht, Janbernd Kirschner, Manuela Pendziwiat, Barbara Zieger
Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant disorder associated with episodic, recurrent, and painful neuropathies affecting the nerves of the brachial plexus. In this study, we report on a family of Lebanese descent with HNA onset in early childhood. The affected family members presented with platelet dysfunction. Platelet aggregation was reduced after stimulation with the agonists ADP and epinephrine in all affected family members. Flow cytometric analyses revealed impaired platelet δ-secretion...
July 18, 2018: Cytoskeleton
Michael A Mkrtschjan, Christopher Solís, Admasu Y Wondmagegn, Janki Majithia, Brenda Russell
The stiffness of the microenvironment surrounding a cell can result in cytoskeletal remodeling, leading to altered cell function and tissue macrostructure. In this study, we tuned the stiffness of the underlying substratum on which neonatal rat cardiomyocytes were grown in culture in order to mimic normal (10 kPa), pathological stiffness of fibrotic myocardium (100 kPa), and a non-physiological extreme (glass). Cardiomyocytes were then challenged by beta adrenergic stimulation through isoproterenol treatment to investigate the response to acute work demand for cells grown on surfaces of varying stiffness...
July 18, 2018: Cytoskeleton
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