scholarly journals Loss of supervillin causes myopathy with myofibrillar disorganization and autophagic vacuoles

Brain ◽  
2020 ◽  
Vol 143 (8) ◽  
pp. 2406-2420 ◽  
Author(s):  
Carola Hedberg-Oldfors ◽  
Robert Meyer ◽  
Kay Nolte ◽  
Yassir Abdul Rahim ◽  
Christopher Lindberg ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Actin Binding ◽  
Cell Physiology ◽  
Muscle Fibres ◽  
Loss Of Function ◽  
Electron Microscopic ◽  
Autophagic Vacuoles ◽  
Associated Proteins ◽  
Characteristic Features

Abstract The muscle specific isoform of the supervillin protein (SV2), encoded by the SVIL gene, is a large sarcolemmal myosin II- and F-actin-binding protein. Supervillin (SV2) binds and co-localizes with costameric dystrophin and binds nebulin, potentially attaching the sarcolemma to myofibrillar Z-lines. Despite its important role in muscle cell physiology suggested by various in vitro studies, there are so far no reports of any human disease caused by SVIL mutations. We here report four patients from two unrelated, consanguineous families with a childhood/adolescence onset of a myopathy associated with homozygous loss-of-function mutations in SVIL. Wide neck, anteverted shoulders and prominent trapezius muscles together with variable contractures were characteristic features. All patients showed increased levels of serum creatine kinase but no or minor muscle weakness. Mild cardiac manifestations were observed. Muscle biopsies showed complete loss of large supervillin isoforms in muscle fibres by western blot and immunohistochemical analyses. Light and electron microscopic investigations revealed a structural myopathy with numerous lobulated muscle fibres and considerable myofibrillar alterations with a coarse and irregular intermyofibrillar network. Autophagic vacuoles, as well as frequent and extensive deposits of lipoproteins, including immature lipofuscin, were observed. Several sarcolemma-associated proteins, including dystrophin and sarcoglycans, were partially mis-localized. The results demonstrate the importance of the supervillin (SV2) protein for the structural integrity of muscle fibres in humans and show that recessive loss-of-function mutations in SVIL cause a distinctive and novel myopathy.

scholarly journals Villin Severing Activity Enhances Actin-based Motility In Vivo

2007 ◽  
Vol 18 (3) ◽  
pp. 827-838 ◽  
Author(s):  
Céline Revenu ◽  
Matthieu Courtois ◽  
Alphée Michelot ◽  
Cécile Sykes ◽  
Daniel Louvard ◽  
...  
Keyword(s):  
Shigella Flexneri ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Loss Of Function ◽  
Mesenchymal Transition ◽  
Capping Protein ◽  
Function Strategy ◽  
In Cells

Villin, an actin-binding protein associated with the actin bundles that support microvilli, bundles, caps, nucleates, and severs actin in a calcium-dependant manner in vitro. We hypothesized that the severing activity of villin is responsible for its reported role in enhancing cell plasticity and motility. To test this hypothesis, we chose a loss of function strategy and introduced mutations in villin based on sequence comparison with CapG. By pyrene-actin assays, we demonstrate that this mutant has a strongly reduced severing activity, whereas nucleation and capping remain unaffected. The bundling activity and the morphogenic effects of villin in cells are also preserved in this mutant. We thus succeeded in dissociating the severing from the three other activities of villin. The contribution of villin severing to actin dynamics is analyzed in vivo through the actin-based movement of the intracellular bacteria Shigella flexneri in cells expressing villin and its severing variant. The severing mutations abolish the gain of velocity induced by villin. To further analyze this effect, we reconstituted an in vitro actin-based bead movement in which the usual capping protein is replaced by either the wild type or the severing mutant of villin. Confirming the in vivo results, villin-severing activity enhances the velocity of beads by more than two-fold and reduces the density of actin in the comets. We propose a model in which, by severing actin filaments and capping their barbed ends, villin increases the concentration of actin monomers available for polymerization, a mechanism that might be paralleled in vivo when an enterocyte undergoes an epithelio-mesenchymal transition.

Estramustine binds MAP-2 to inhibit microtubule assembly in vitro

1988 ◽  
Vol 89 (3) ◽  
pp. 331-342
Author(s):  
M.E. Stearns ◽  
K.D. Tew
Keyword(s):  
Linear Regression Analysis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Microtubule Assembly ◽  
Scatchard Analysis ◽  
Binding Assays ◽  
Electron Microscopic ◽  
Associated Proteins ◽  
Microscopic Studies

We have investigated the ability of estramustine to bind to rat brain microtubule-associated proteins (MAPs) and purified MAP-2 in vitro. [3H]estramustine's relative affinity for tubulin and MAPs was assessed by gel filtration chromatography, immunoprecipitation and binding assays. Scatchard analysis demonstrated a specific affinity of the drug for MAP-2. Calculations from kinetic parameters and non-linear regression analysis gave a Kd of 15 microM, and a Bmax of 3.4 × 10(−7)M ml-1. Extrapolation of this value suggested that each MAP-2 molecule binds approximately 20 molecules of estramustine. Microtubule assembly studies and SDS-polyacrylamide gel electrophoresis revealed that at 20–60 microM levels, estramustine inhibited the association of MAPs with taxol microtubules. Turbidity (A350) studies further demonstrated that 20–60 microM-estramustine inhibited MAP-2-driven tubulin assembly and produced microtubule disassembly. Electron-microscopic studies confirmed the centrifugation and turbidity results. The data demonstrated that estramustine can bind MAPs and MAP-2 specifically, thereby inhibiting microtubule assembly.

scholarly journals GENETICS IN ENDOCRINOLOGY: Gain and loss of function mutations of the calcium-sensing receptor and associated proteins: current treatment concepts

2016 ◽  
Vol 174 (5) ◽  
pp. R189-R208 ◽  
Author(s):  
Bernhard Mayr ◽  
Dirk Schnabel ◽  
Helmuth-Günther Dörr ◽  
Christof Schöfl
Keyword(s):  
Calcium Supplementation ◽  
Current Treatment ◽  
Loss Of Function ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Therapeutic Concepts ◽  
Sigma 1 ◽  
Associated Proteins ◽  
Treatment Concepts

The calcium-sensing receptor (CASR) is the main calcium sensor in the maintenance of calcium metabolism. Mutations of theCASR, the G protein alpha 11 (GNA11) and the adaptor-related protein complex 2 sigma 1 subunit (AP2S1) genes can shift the set point for calcium sensing causing hyper- or hypo-calcemic disorders. Therapeutic concepts for these rare diseases range from general therapies of hyper- and hypo-calcemic conditions to more pathophysiology oriented approaches such as parathyroid hormone (PTH) substitution and allosteric CASR modulators. Cinacalcet is a calcimimetic that enhances receptor function and has gained approval for the treatment of hyperparathyroidism. Calcilytics in turn attenuate CASR activity and are currently under investigation for the treatment of various diseases. We conducted a literature search for reports about treatment of patients harboring inactivating or activating CASR, GNA11 or AP2S1 mutants and aboutin vitroeffects of allosteric CASR modulators on mutated CASR. The therapeutic concepts for patients with familial hypocalciuric hypercalcemia (FHH), neonatal hyperparathyroidism (NHPT), neonatal severe hyperparathyroidism (NSHPT) and autosomal dominant hypocalcemia (ADH) are reviewed. FHH is usually benign, but symptomatic patients benefit from cinacalcet. In NSHPT patients pamidronate effectively lowers serum calcium, but most patients require parathyroidectomy. In some patients cinacalcet can obviate the need for surgery, particularly in heterozygous NHPT. Symptomatic ADH patients respond to vitamin D and calcium supplementation but this may increase calciuria and renal complications. PTH treatment can reduce relative hypercalciuria. None of the currently available therapies for ADH, however, prevent tissue calcifications and complications, which may become possible with calcilytics that correct the underlying pathophysiologic defect.

Resveratrol in vitro amelioratestert-butyl hydroperoxide-induced alterations in erythrocyte membranes from young and older humans

2014 ◽  
Vol 39 (10) ◽  
pp. 1093-1097 ◽  
Author(s):  
Kanti Bhooshan Pandey ◽  
Syed Ibrahim Rizvi
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Biological Effect ◽  
Healthy Subjects ◽  
Structural Integrity ◽  
Cell Interaction ◽  
Erythrocyte Membranes ◽  
Cell Physiology ◽  
Oxygen Species

Implication of reactive oxygen species/oxidative stress has been readily reported in etiology of aging and related manifestations. Plasma membrane as a regulator of numerous aspects of cell physiology including cell–cell interaction, solute transport, and signal transduction, provides structural integrity to the cells. The aim of the present study was to determine the effect of resveratrol administration in vitro, to evaluate the biological effect of this phytoalexin in oxidatively injured erythrocytes during aging. This study, carried out on 91 normal healthy subjects, provides experimental evidence that erythrocytes have increased oxidative damage with age. In vitro administration of resveratrol significantly attenuated deleterious effects of oxidative injury in erythrocytes from humans of all ages.

Effects of Colchicine on the Golgi Complex and Gerl of Cultured Rat Peritoneal Macrophages and Epiphyseal Chondrocytes

1980 ◽  
Vol 45 (1) ◽  
pp. 41-58
Author(s):  
JOHAN THYBERG ◽  
ANDRZEJ PIASEK ◽  
STANISLAW MOSKALEWSKI
Keyword(s):  
Golgi Complex ◽  
Structural Integrity ◽  
Cell Types ◽  
Peritoneal Macrophages ◽  
Electron Microscopic ◽  
Thiamine Pyrophosphatase ◽  
Cytoplasmic Microtubules ◽  
The Individual ◽  
Functionally Diverse

Thioglycollate-elicited rat peritoneal macrophages and epiphyseal chondrocytes were cultured in vitro, treated with colchicine, and then studied by electron-microscopic and cytochemical techniques. Colchicine, but not lumicolchicine, caused disappearance of cytoplasmic microtubules and breakup of the Golgi complex with spreading of its dictyosomes from a well defined juxta nuclear area throughout the cytoplasm. There was also an altered distribution of lysosomes, which oriented themselves close to the dictyosomes both in controland colchicine-treated cells. Further, the structure of the individual dictyosomes was changed, especially in the chondrocytes. GERL equivalents were observed in control cells but were difficult to detect after exposure to colchicine. Reaction product for thiamine pyrophosphatase was found in narrow cisternae on the inner side of the dictyosomes in control cells but invacuole-like structures in colchicine-treated cells. Reaction product for acid phosphatase was present in GERL equivalents and lysosomes in control cells but mainly in lysosomes incolchicine-treated cells. Nevertheless, the total specific activities of these enzymes as well as of 5′-nucleotidase, a plasma membrane marker, remained unaffected by the drug treatment. These observations show that cytoplasmic microtubules play an important and, in many respects similar, cytoskeletal role in two so functionally diverse cell types as macrophages and chondrocytes. They are particularly important for the structural integrity of the Golgi complex, which in both cells is normally organized in the area around the centrioles, from which numerous microtubules radiate into the cytoplasm. The observations further suggest that GERL is an integrated part of the Golgi complex in these cells.

scholarly journals The Human FSGS-Causing ANLN R431C Mutation Induces Dysregulated PI3K/AKT/mTOR/Rac1 Signaling in Podocytes

2018 ◽  
Vol 29 (8) ◽  
pp. 2110-2122 ◽  
Author(s):  
Gentzon Hall ◽  
Brandon M. Lane ◽  
Kamal Khan ◽  
Igor Pediaditakis ◽  
Jianqiu Xiao ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Adaptor Protein ◽  
Pi3k Pathway ◽  
Actin Binding ◽  
Loss Of Function ◽  
Signaling Axis ◽  
Phosphoinositide 3 Kinase

BackgroundWe previously reported that mutations in the anillin (ANLN) gene cause familial forms of FSGS. ANLN is an F-actin binding protein that modulates podocyte cell motility and interacts with the phosphoinositide 3-kinase (PI3K) pathway through the slit diaphragm adaptor protein CD2-associated protein (CD2AP). However, it is unclear how the ANLN mutations cause the FSGS phenotype. We hypothesized that the R431C mutation exerts its pathogenic effects by uncoupling ANLN from CD2AP.MethodsWe conducted in vivo complementation assays in zebrafish to determine the effect of the previously identified missense ANLN variants, ANLNR431C and ANLNG618C during development. We also performed in vitro functional assays using human podocyte cell lines stably expressing wild-type ANLN (ANLNWT) or ANLNR431C.ResultsExperiments in anln-deficient zebrafish embryos showed a loss-of-function effect for each ANLN variant. In human podocyte lines, expression of ANLNR431C increased cell migration, proliferation, and apoptosis. Biochemical characterization of ANLNR431C-expressing podocytes revealed hyperactivation of the PI3K/AKT/mTOR/p70S6K/Rac1 signaling axis and activation of mTOR-driven endoplasmic reticulum stress in ANLNR431C-expressing podocytes. Inhibition of mTOR, GSK-3β, Rac1, or calcineurin ameliorated the effects of ANLNR431C. Additionally, inhibition of the calcineurin/NFAT pathway reduced the expression of endogenous ANLN and mTOR.ConclusionsThe ANLNR431C mutation causes multiple derangements in podocyte function through hyperactivation of PI3K/AKT/mTOR/p70S6K/Rac1 signaling. Our findings suggest that the benefits of calcineurin inhibition in FSGS may be due, in part, to the suppression of ANLN and mTOR. Moreover, these studies illustrate that rational therapeutic targets for familial FSGS can be identified through biochemical characterization of dysregulated podocyte phenotypes.

scholarly journals mini spindles

1999 ◽  
Vol 146 (5) ◽  
pp. 1005-1018 ◽  
Author(s):  
C. Fiona Cullen ◽  
Peter Deák ◽  
David M. Glover ◽  
Hiroyuki Ohkura
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Structural Integrity ◽  
Sequence Similarity ◽  
High Similarity ◽  
Microtubule Associated Proteins ◽  
Spindle Poles ◽  
Associated Proteins ◽  
Diploid Cells

We describe a new Drosophila gene, mini spindles (msps) identified in a cytological screen for mitotic mutant. Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells. Nucleation of microtubules from centrosomes, metaphase alignment of chromosomes, or the focusing of spindle poles appears much less affected. The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast. Consistent with their sequence similarity, Msps protein also associates with microtubules in vitro. In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase. The absence of centrosomal staining in interphase of the cellularized embryos suggests that the interactions between Msps protein and microtubules or centrosomes may be regulated during the cell cycle.

scholarly journals Biased localization of actin binding proteins by actin filament conformation

2020 ◽  
Author(s):  
Andrew R Harris ◽  
Pamela Jreij ◽  
Brian Belardi ◽  
Andreas Bausch ◽  
Daniel A Fletcher
Keyword(s):  
Actin Filament ◽  
Single Molecule ◽  
Conformational Changes ◽  
Actin Filaments ◽  
Binding Proteins ◽  
Critical Role ◽  
Actin Binding ◽  
Cell Physiology ◽  
Physical Constraints

ABSTRACTThe assembly of actin filaments into distinct cytoskeletal structures plays a critical role in cell physiology, but how proteins localize differentially to these structures within a shared cytoplasm remains unclear. Here, we show that the actin-binding domains of accessory proteins can be sensitive to filament conformational changes. Using a combination of live cell imaging and in vitro single molecule binding measurements, we show that tandem calponin homology domains (CH1-CH2) can be mutated to preferentially bind actin networks at the front or rear of motile cells, and we demonstrate that the affinity of CH1-CH2 domain mutants varies as actin filament conformation is altered by perturbations that include stabilizing drugs, physical constraints, and other binding proteins. These findings suggest that conformational heterogeneity of actin filaments in cells could help to direct accessory binding proteins to different actin cytoskeletal structures through a biophysical feedback loop.

scholarly journals Biased localization of actin binding proteins by actin filament conformation

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrew R. Harris ◽  
Pamela Jreij ◽  
Brian Belardi ◽  
Aaron M. Joffe ◽  
Andreas R. Bausch ◽  
...  
Keyword(s):  
Actin Filament ◽  
Single Molecule ◽  
Conformational Changes ◽  
Actin Filaments ◽  
Binding Proteins ◽  
Critical Role ◽  
Actin Binding ◽  
Cell Physiology ◽  
Binding Domains

AbstractThe assembly of actin filaments into distinct cytoskeletal structures plays a critical role in cell physiology, but how proteins localize differentially to these structures within a shared cytoplasm remains unclear. Here, we show that the actin-binding domains of accessory proteins can be sensitive to filament conformational changes. Using a combination of live cell imaging and in vitro single molecule binding measurements, we show that tandem calponin homology domains (CH1–CH2) can be mutated to preferentially bind actin networks at the front or rear of motile cells. We demonstrate that the binding kinetics of CH1–CH2 domain mutants varies as actin filament conformation is altered by perturbations that include stabilizing drugs and other binding proteins. These findings suggest that conformational changes of actin filaments in cells could help to direct accessory binding proteins to different actin cytoskeletal structures through a biophysical feedback loop.

scholarly journals Inactivation of the IGF-I receptor gene in primary Sertoli cells highlights the autocrine effects of IGF-I

2007 ◽  
Vol 194 (3) ◽  
pp. 557-568 ◽  
Author(s):  
P Froment ◽  
M Vigier ◽  
D Nègre ◽  
I Fontaine ◽  
J Beghelli ◽  
...  
Keyword(s):  
Sertoli Cell ◽  
Sertoli Cells ◽  
Function Analysis ◽  
Receptor Gene ◽  
Mammalian Species ◽  
Cell Physiology ◽  
Loss Of Function ◽  
Igf I

IGF-I regulates pituitaryand gonadal functions, and is pivotal for sexual development and fertility in mammalian species. To better understand the function of autocrine IGF-I in Sertoli cell physiology, we established a system for Cre-mediated conditional inactivation of the IGF-I receptor (IGF-IR) in cultured Sertoli cells. We show here that loss of IGF-IR decreased the number of viable Sertoli cells as a consequence of diminished Sertoli cell proliferation and increased Sertoli cell death. Furthermore, the lack of IGF-IR altered the morphology of cultured Sertoli cells and decreased lactate and transferrin secretions. Collectively, our data indicate that autocrine IGF-I contributes significantly to Sertoli cell homeostasis. The described in vitro system for loss-of-function analysis of the IGF-IR can be readily transposed to study the role of other intratesticular growth factors involved in spermatogenesis.

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