scholarly journals The Central Role of the Tail in Switching Off Myosin II in Cells

2019 ◽  
Author(s):  
Shixin Yang ◽  
Kyoung Hwan Lee ◽  
John L. Woodhead ◽  
Osamu Sato ◽  
Mitsuo Ikebe ◽  
...  
Keyword(s):  
Atp Hydrolysis ◽  
Myosin Ii ◽  
Actin Binding ◽  
Compact Structure ◽  
Mechanism Of Inhibition ◽  
Energy Conserving ◽  
High Degree ◽  
First Time ◽  
In Cells

AbstractMyosin II is a motor protein playing an essential role in cell motility. The molecule can exist as a polymer that pulls on actin to generate motion, or as an inactive monomer with a compact structure, in which its tail is folded and its two heads interact with each other. This conformation functions in cells as an energy-conserving storage and transport molecule. The mechanism of inhibition is not fully understood. We have carried out a 3D reconstruction of the switched-off form revealing for the first time multiple interactions between the tail and the two heads that trap ATP hydrolysis products, block actin binding, obstruct head phosphorylation, and prevent filament formation. Blocking these essential features of myosin function can explain the high degree of inhibition of the folded form of myosin, serving its energy-conserving, storage function in cells. The structure also suggests a mechanism for unfolding when activated by phosphorylation.

scholarly journals The central role of the tail in switching off 10S myosin II activity

2019 ◽  
Vol 151 (9) ◽  
pp. 1081-1093 ◽  
Author(s):  
Shixin Yang ◽  
Kyoung Hwan Lee ◽  
John L. Woodhead ◽  
Osamu Sato ◽  
Mitsuo Ikebe ◽  
...  
Keyword(s):  
Atp Hydrolysis ◽  
Myosin Ii ◽  
Active Form ◽  
Sedimentation Coefficient ◽  
Actin Binding ◽  
Myosin Filament ◽  
Particle Analysis ◽  
Compact Structure ◽  
Energy Conserving ◽  
In Cells

Myosin II is a motor protein with two heads and an extended tail that plays an essential role in cell motility. Its active form is a polymer (myosin filament) that pulls on actin to generate motion. Its inactive form is a monomer with a compact structure (10S sedimentation coefficient), in which the tail is folded and the two heads interact with each other, inhibiting activity. This conformation is thought to function in cells as an energy-conserving form of the molecule suitable for storage as well as transport to sites of filament assembly. The mechanism of inhibition of the compact molecule is not fully understood. We have performed a 3-D reconstruction of negatively stained 10S myosin from smooth muscle in the inhibited state using single-particle analysis. The reconstruction reveals multiple interactions between the tail and the two heads that appear to trap ATP hydrolysis products, block actin binding, hinder head phosphorylation, and prevent filament formation. Blocking these essential features of myosin function could explain the high degree of inhibition of the folded form of myosin thought to underlie its energy-conserving function in cells. The reconstruction also suggests a mechanism for unfolding when myosin is activated by phosphorylation.

scholarly journals UNC-45A Weakens and Breaks MT Lattice Independent of its Effect on Non-Muscle Myosin II

2020 ◽  
Author(s):  
Juri Habicht ◽  
Ashley Mooneyham ◽  
Asumi Hoshino ◽  
Mihir Shetty ◽  
Xiaonan Zhang ◽  
...  
Keyword(s):  
Neurodegenerative Diseases ◽  
Myosin Ii ◽  
Human Diseases ◽  
Therapeutic Implications ◽  
Associated Functions ◽  
Muscle Myosin ◽  
First Time ◽  
In Cells

AbstractIn invertebrates, UNC-45 regulates myosin stability and functions. Vertebrates have two distinct isoforms of the protein: UNC-45B, expressed in muscle cells only and UNC-45A, expressed in all cells and implicated in regulating both Non-Muscle Myosin II (NMII)- and microtubule (MT)-associated functions. Here we show for the first time that: a) in vitro UNC-45A binds to the MT lattice and weakens its integrity leading to MT bending, breakage and depolymerization, b) in cells, UNC-45A overexpression causes loss of MT mass and increase in MT breakages, c) both in vitro and in cells, UNC-45A destabilizes MTs independent of its NMII C-terminal binding domain and destabilization occurs even in presence of the NMII inhibitor blebbistatin. These findings are consistent with a not mutually exclusive but rather dual role of UNC-45A in regulating NMII activity and MT stability.Because many human diseases, from cancer to neurodegenerative diseases, are caused by or associated with deregulation of MT stability our findings have profound implications in both, the biology of MTs as well as the biology of human diseases and possible therapeutic implications for their treatment.

scholarly journals Insights into animal septins using recombinant human septin octamers with distinct SEPT9 isoforms

2021 ◽  
Author(s):  
Francois Iv ◽  
Carla Silva Martins ◽  
Gerard Castro-Linares ◽  
Cyntia Taveneau ◽  
Pascale Barbier ◽  
...  
Keyword(s):  
Biological Functions ◽  
Mammalian Development ◽  
Cross Link ◽  
Complex Interactions ◽  
Biophysical Studies ◽  
First Time ◽  
Established Role ◽  
Design Cell ◽  
In Cells

Septin GTP-binding proteins contribute essential biological functions that range from the establishment of cell polarity to animal tissue morphogenesis. Human septins in cells form hetero-octameric septin complexes containing the ubiquitously expressed SEPT9. Despite the established role of SEPT9 in mammalian development and human pathophysiology, biochemical and biophysical studies have relied on monomeric SEPT9 thus not recapitulating its native assembly into hetero-octameric complexes. We established a protocol that enabled the first-time isolation of recombinant human septin octamers containing distinct SEPT9 isoforms. A combination of biochemical and biophysical assays confirmed the octameric nature of the isolated complexes in solution. Reconstitution studies showed that octamers with either a long or a short SEPT9 isoform form filament assemblies, and can directly bind and cross-link actin filaments, raising the possibility that septin-decorated actin structures in cells reflect direct actin-septin interactions. Recombinant SEPT9-containing octamers will make it possible to design cell-free assays to dissect the complex interactions of septins with cell membranes and the actin/microtubule cytoskeleton.

Actin filaments stimulate the Na(+)-K(+)-ATPase

1995 ◽  
Vol 269 (5) ◽  
pp. F637-F643 ◽  
Author(s):  
H. F. Cantiello
Keyword(s):  
Sequence Analysis ◽  
Atpase Activity ◽  
Actin Filaments ◽  
Functional Role ◽  
Atp Hydrolysis ◽  
Rat Kidney ◽  
Alpha Subunit ◽  
Actin Binding ◽  
Binding Domains

In this report, the functional role of actin on Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) activity was explored. The Na(+)- and K(+)-dependent, ouabain-sensitive ATP hydrolysis mediated by rat kidney Na(+)-K(+)-ATPase increased by 74% in the presence of previously unpolymerized actin (24 microM), whereas addition of polymerized actin was without effect. Addition of actin was associated instead with an increase in the affinity of the Na(+)-K(+)-ATPase for Na+ but not other enzymatic substates. A maximal stimulatory effect (296%) was observed either at an Na(+)-K(+)-ATPase:actin ratio of 1:50,000 or at lower ratios (1:625) by shifting from the E2 (K+ selective) to the E1 (Na+ selective) conformation of the enzyme. Immunoblotting of actin to the purified Na(+)-K(+)-ATPase suggested that this interaction may be linked to binding of actin to the enzyme, which was further supported by sequence analysis indicating putative actin-binding domains in the alpha-subunit of the enzyme. The interaction between actin and the Na(+)-K(+)-ATPase may imply a novel functional role of the cytoskeleton in the control of ion transport.

scholarly journals Functional Role of Non-Muscle Myosin II in Microglia: An Updated Review

2021 ◽  
Vol 22 (13) ◽  
pp. 6687
Author(s):  
Chiara Porro ◽  
Antonio Pennella ◽  
Maria Antonietta Panaro ◽  
Teresa Trotta
Keyword(s):  
Nervous System ◽  
Atp Hydrolysis ◽  
Myosin Ii ◽  
Cellular Functions ◽  
Pathological Conditions ◽  
Different Types ◽  
The Central Nervous System ◽  
Muscle Myosin ◽  
Pro Inflammatory Cytokines

Myosins are a remarkable superfamily of actin-based motor proteins that use the energy derived from ATP hydrolysis to translocate actin filaments and to produce force. Myosins are abundant in different types of tissues and involved in a large variety of cellular functions. Several classes of the myosin superfamily are expressed in the nervous system; among them, non-muscle myosin II (NM II) is expressed in both neurons and non-neuronal brain cells, such as astrocytes, oligodendrocytes, endothelial cells, and microglia. In the nervous system, NM II modulates a variety of functions, such as vesicle transport, phagocytosis, cell migration, cell adhesion and morphology, secretion, transcription, and cytokinesis, as well as playing key roles during brain development, inflammation, repair, and myelination functions. In this review, we will provide a brief overview of recent emerging roles of NM II in resting and activated microglia cells, the principal regulators of immune processes in the central nervous system (CNS) in both physiological and pathological conditions. When stimulated, microglial cells react and produce a number of mediators, such as pro-inflammatory cytokines, free radicals, and nitric oxide, that enhance inflammation and contribute to neurodegenerative diseases. Inhibition of NM II could be a new therapeutic target to treat or to prevent CNS diseases.

scholarly journals Repragmatization of the ME TOO Speech Act in Social and Communicative Practices of the Internet

2020 ◽  
pp. 176-187
Author(s):  
T. M. Shkapenko ◽  
N. B. Milyavskaya
Keyword(s):  
Speech Act ◽  
The Internet ◽  
New Wave ◽  
Communicative Practices ◽  
Cultural Symbol ◽  
Internet Environment ◽  
Mass Participation ◽  
High Degree ◽  
First Time

The pragmatic nature of the Me too speech act is studied in two different areas of functioning: outside the Internet environment and in cyberspace. It is noted that in normal communication Me too is a response cue that closes an adjacency pair and does not have a persuasive potential. On the Internet, this speech act undergoes radical changes, turning into a stimulus statement that initiates the mass participation of a certain target audience in the movement against sexual harassment. It is shown that the pragmatic transformation of the phrase is due to the action of both linguistic and extralinguistic factors. The transition from a responsive cue to an initial utterance is ensured by a common presupposition for all addressees, while the versatility of intentions acquired by the speech act (affirmation, recognition, accusation, appeal) together with the deictic pronoun of the first person endow it with a high degree of persuasiveness. As the psychological basis for the effective impact of the phrase, the ideas of the American psychological school about the importance of empathy and the therapeutic effect of public actions - confessions are successfully introduced into the consciousness of a globalized community. The novelty of the study is that for the first time the fact of the limited relevance of individual postulates of pragmalinguistic theories for the Internet space is established. The relevance of the work is associated with the need for a comprehensive understanding of the phenomenon of repragmatization of the Me too , which receives the role of a semiotic marker and a cultural symbol of a new wave of the feminist movement.

Myosin II isoforms in smooth muscle: heterogeneity and function

2007 ◽  
Vol 293 (2) ◽  
pp. C493-C508 ◽  
Author(s):  
Thomas J. Eddinger ◽  
Daniel P. Meer
Keyword(s):  
Smooth Muscle ◽  
Conformational Changes ◽  
Atp Hydrolysis ◽  
Expression Profiles ◽  
Myosin Ii ◽  
Thick Filament ◽  
Actin Binding ◽  
Head Region ◽  
Organ Systems ◽  
Species Specific

Both smooth muscle (SM) and nonmuscle class II myosin molecules are expressed in SM tissues comprising hollow organ systems. Individual SM cells may express one or more of multiple myosin II isoforms that differ in myosin heavy chain (MHC) and myosin light chain (MLC) subunits. Although much has been learned, the expression profiles, organization within contractile filaments, localization within cells, and precise roles in various contractile functions of these different myosin molecules are still not well understood. However, data supporting unique physiological roles for certain isoforms continues to build. Isoform differences located in the S1 head region of the MHC can alter actin binding and rates of ATP hydrolysis. Differences located in the MHC tail can alter the formation, stability, and size of the myosin thick filament. In these distinct ways, both head and tail isoform differences can alter force generation and muscle shortening velocities. The MLCs that are associated with the lever arm of the S1 head can affect the flexibility and range of motion of this domain and possibly the motion of the S2 and motor domains. Phosphorylation of MLC20 has been associated with conformational changes in the S1 and/or S2 fragments regulating enzymatic activity of the entire myosin molecule. A challenge for the future will be delineation of the physiological significance of the heterogeneous expression of these isoforms in developmental, tissue-specific, and species-specific patterns and or the intra- and intercellular heterogeneity of myosin isoform expression in SM cells of a given organ.

scholarly journals The disease-linked Glu-26-Lys mutant version of Coronin 1A exhibits pleiotropic and pathway-specific signaling defects

2015 ◽  
Vol 26 (16) ◽  
pp. 2895-2912 ◽  
Author(s):  
Virginia Ojeda ◽  
Javier Robles-Valero ◽  
María Barreira ◽  
Xosé R. Bustelo
Keyword(s):  
Myosin Ii ◽  
Dominant Negative ◽  
Actin Binding ◽  
Dominant Negative Mutant ◽  
Loss Of Function ◽  
Wild Type ◽  
Activated T Cells ◽  
Wild Type Counterpart ◽  
Rac1 Gtpase ◽  
In Cells

Coronin 1A (Coro1A) is involved in cytoskeletal and signaling events, including the regulation of Rac1 GTPase– and myosin II–dependent pathways. Mutations that generate truncated or unstable Coro1A proteins cause immunodeficiencies in both humans and rodents. However, in the case of the peripheral T-cell–deficient ( Ptcd) mouse strain, the immunodeficiency is caused by a Glu-26-Lys mutation that targets a surface-exposed residue unlikely to affect the intramolecular architecture and stability of the protein. Here we report that this mutation induces pleiotropic effects in Coro1A protein, including the exacerbation of Coro1A-dependent actin-binding and -bundling activities; the formation of large meshworks of Coro1AE26K-decorated filaments endowed with unusual organizational, functional, and staining properties; and the elimination of Coro1A functions associated with both Rac1 and myosin II signaling. By contrast, it does not affect the ability of Coro1A to stimulate the nuclear factor of activated T-cells (NF-AT). Coro1AE26K is not a dominant-negative mutant, indicating that its pathological effects are derived from the inability to rescue the complete loss of the wild-type counterpart in cells. These results indicate that Coro1AE26K behaves as either a recessive gain-of-function or loss-of-function mutant protein, depending on signaling context and presence of the wild-type counterpart in cells.

scholarly journals Insights into animal septins using recombinant human septin octamers with distinct SEPT9 isoforms

2021 ◽  
Author(s):  
Francois Iv ◽  
Carla Silva Martins ◽  
Gerard Castro-Linares ◽  
Cyntia Taveneau ◽  
Pascale Barbier ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Mammalian Development ◽  
Cross Link ◽  
Complex Interactions ◽  
Biophysical Studies ◽  
First Time ◽  
Established Role ◽  
Design Cell ◽  
In Cells

AbstractSeptin GTP-binding proteins contribute essential biological functions that range from the establishment of cell polarity to animal tissue morphogenesis. Human septins in cells form hetero-octameric septin complexes containing the ubiquitously expressed SEPT9. Despite the established role of SEPT9 in mammalian development and human pathophysiology, biochemical and biophysical studies have relied on monomeric SEPT9 thus not recapitulating its native assembly into hetero-octameric complexes. We established a protocol that enabled the first-time isolation of recombinant human septin octamers containing distinct SEPT9 isoforms. A combination of biochemical and biophysical assays confirmed the octameric nature of the isolated complexes in solution. Reconstitution studies showed that octamers with either a long or a short SEPT9 isoform form filament assemblies, and can directly bind and cross-link actin filaments, raising the possibility that septin-decorated actin structures in cells reflect direct actin-septin interactions. Recombinant SEPT9-containing octamers will make it possible to design cell-free assays to dissect the complex interactions of septins with cell membranes and the actin/microtubule cytoskeleton.SummaryHuman septins in cells form hetero-octameric complexes containing the ubiquitously expressed SEPT9. Iv et al. describe the first-time isolation of recombinant human septin octamers with distinct SEPT9 isoforms. Reconstitution studies show that octamers with either a long or a short SEPT9 isoform form higher-order filament assemblies and directly bind and cross-link actin filaments.

scholarly journals By moonlighting in the nucleus, villin regulates epithelial plasticity

2016 ◽  
Vol 27 (3) ◽  
pp. 535-548 ◽  
Author(s):  
Srinivas Patnaik ◽  
Sudeep P. George ◽  
Eric Pham ◽  
Swati Roy ◽  
Kanchan Singh ◽  
...  
Keyword(s):  
Wound Repair ◽  
Epithelial Mesenchymal Transition ◽  
Actin Binding ◽  
Nuclear Accumulation ◽  
Epithelial Polarity ◽  
Systematic Analysis ◽  
Mesenchymal Transition ◽  
Epithelial Plasticity ◽  
First Time

Villin is a tissue-specific, actin-binding protein involved in the assembly and maintenance of microvilli in polarized epithelial cells. Conversely, villin is also linked with the loss of epithelial polarity and gain of the mesenchymal phenotype in migrating, invasive cells. In this study, we describe for the first time how villin can switch between these disparate functions to change tissue architecture by moonlighting in the nucleus. Our study reveals that the moonlighting function of villin in the nucleus may play an important role in tissue homeostasis and disease. Villin accumulates in the nucleus during wound repair, and altering the cellular microenvironment by inducing hypoxia increases the nuclear accumulation of villin. Nuclear villin is also associated with mouse models of tumorigenesis, and a systematic analysis of a large cohort of colorectal cancer specimens confirmed the nuclear distribution of villin in a subset of tumors. Our study demonstrates that nuclear villin regulates epithelial–mesenchymal transition (EMT). Altering the nuclear localization of villin affects the expression and activity of Slug, a key transcriptional regulator of EMT. In addition, we find that villin directly interacts with a transcriptional corepressor and ligand of the Slug promoter, ZBRK1. The outcome of this study underscores the role of nuclear villin and its binding partner ZBRK1 in the regulation of EMT and as potential new therapeutic targets to inhibit tumorigenesis.

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