scholarly journals Segregation and activation of myosin IIB creates a rear in migrating cells

2008 ◽  
Vol 183 (3) ◽  
pp. 543-554 ◽  
Author(s):  
Miguel Vicente-Manzanares ◽  
Margaret A. Koach ◽  
Leanna Whitmore ◽  
Marcelo L. Lamers ◽  
Alan F. Horwitz
Keyword(s):  
Self Assembly ◽  
De Novo ◽  
Coiled Coil ◽  
Myosin Isoforms ◽  
C Terminus ◽  
Filament Bundles ◽  
A Cell ◽  
Myosin Iia ◽  
And Function ◽  
Migrating Cells

We have found that MLC-dependent activation of myosin IIB in migrating cells is required to form an extended rear, which coincides with increased directional migration. Activated myosin IIB localizes prominently at the cell rear and produces large, stable actin filament bundles and adhesions, which locally inhibit protrusion and define the morphology of the tail. Myosin IIA forms de novo filaments away from the myosin IIB–enriched center and back to form regions that support protrusion. The positioning and dynamics of myosin IIA and IIB depend on the self-assembly regions in their coiled-coil C terminus. COS7 and B16 melanoma cells lack myosin IIA and IIB, respectively; and show isoform-specific front-back polarity in migrating cells. These studies demonstrate the role of MLC activation and myosin isoforms in creating a cell rear, the segregation of isoforms during filament assembly and their differential effects on adhesion and protrusion, and a key role for the noncontractile region of the isoforms in determining their localization and function.

scholarly journals A disease-associated frameshift mutation in caveolin-1 disrupts caveolae formation and function through introduction of a de novo ER retention signal

2017 ◽  
Vol 28 (22) ◽  
pp. 3095-3111 ◽  
Author(s):  
Courtney A. Copeland ◽  
Bing Han ◽  
Ajit Tiwari ◽  
Eric D. Austin ◽  
James E. Loyd ◽  
...  
Keyword(s):  
Frameshift Mutation ◽  
De Novo ◽  
Dominant Negative ◽  
Caveolin 1 ◽  
Protein Levels ◽  
C Terminus ◽  
Er Retention ◽  
And Function ◽  
Er Retention Signal ◽  
Retention Signal

Caveolin-1 (CAV1) is an essential component of caveolae and is implicated in numerous physiological processes. Recent studies have identified heterozygous mutations in the CAV1 gene in patients with pulmonary arterial hypertension (PAH), but the mechanisms by which these mutations impact caveolae assembly and contribute to disease remain unclear. To address this question, we examined the consequences of a familial PAH-associated frameshift mutation in CAV1, P158PfsX22, on caveolae assembly and function. We show that C-terminus of the CAV1 P158 protein contains a functional ER-retention signal that inhibits ER exit and caveolae formation and accelerates CAV1 turnover in Cav1–/– MEFs. Moreover, when coexpressed with wild-type (WT) CAV1 in Cav1–/– MEFs, CAV1-P158 functions as a dominant negative by partially disrupting WT CAV1 trafficking. In patient skin fibroblasts, CAV1 and caveolar accessory protein levels are reduced, fewer caveolae are observed, and CAV1 complexes exhibit biochemical abnormalities. Patient fibroblasts also exhibit decreased resistance to a hypo-osmotic challenge, suggesting the function of caveolae as membrane reservoir is compromised. We conclude that the P158PfsX22 frameshift introduces a gain of function that gives rise to a dominant negative form of CAV1, defining a new mechanism by which disease-associated mutations in CAV1 impair caveolae assembly.

Interfacial zippering-up of coiled-coil protein filaments

2015 ◽  
Vol 17 (46) ◽  
pp. 31055-31060 ◽  
Author(s):  
Emiliana De Santis ◽  
Valeria Castelletto ◽  
Maxim G. Ryadnov
Keyword(s):  
Self Assembly ◽  
De Novo ◽  
Coiled Coil ◽  
Morphological Control

A de novo self-assembly topology for engineering protein nanostructures under morphological control is reported.

scholarly journals MrDNA: a multi-resolution model for predicting the structure and dynamics of DNA systems

2020 ◽  
Vol 48 (9) ◽  
pp. 5135-5146 ◽  
Author(s):  
Christopher Maffeo ◽  
Aleksei Aksimentiev
Keyword(s):  
Self Assembly ◽  
De Novo ◽  
Dna Nanotechnology ◽  
Equilibrium Structure ◽  
Molecular Graphics ◽  
Structure And Dynamics ◽  
Self Assembled ◽  
Actual Shape ◽  
And Function ◽  
Assembly Principles

Abstract Although the field of structural DNA nanotechnology has been advancing with an astonishing pace, de novo design of complex 3D nanostructures and functional devices remains a laborious and time-consuming process. One reason for that is the need for multiple cycles of experimental characterization to elucidate the effect of design choices on the actual shape and function of the self-assembled objects. Here, we demonstrate a multi-resolution simulation framework, mrdna, that, in 30 min or less, can produce an atomistic-resolution structure of a self-assembled DNA nanosystem. We demonstrate fidelity of our mrdna framework through direct comparison of the simulation results with the results of cryo-electron microscopy (cryo-EM) reconstruction of multiple 3D DNA origami objects. Furthermore, we show that our approach can characterize an ensemble of conformations adopted by dynamic DNA nanostructures, the equilibrium structure and dynamics of DNA objects constructed using off-lattice self-assembly principles, i.e. wireframe DNA objects, and to study the properties of DNA objects under a variety of environmental conditions, such as applied electric field. Implemented as an open source Python package, our framework can be extended by the community and integrated with DNA design and molecular graphics tools.

scholarly journals Structural biology of laminins

2019 ◽  
Vol 63 (3) ◽  
pp. 285-295 ◽  
Author(s):  
Erhard Hohenester
Keyword(s):  
Structural Biology ◽  
Coiled Coil ◽  
Large Cell ◽  
Basement Membranes ◽  
Cell Adhesive ◽  
A Cell ◽  
The Cross ◽  
And Function ◽  
Polypeptide Chains

Abstract Laminins are large cell-adhesive glycoproteins that are required for the formation and function of basement membranes in all animals. Structural studies by electron microscopy in the early 1980s revealed a cross-shaped molecule, which subsequently was shown to consist of three distinct polypeptide chains. Crystallographic studies since the mid-1990s have added atomic detail to all parts of the laminin heterotrimer. The three short arms of the cross are made up of continuous arrays of disulphide-rich domains. The globular domains at the tips of the short arms mediate laminin polymerization; the surface regions involved in this process have been identified by structure-based mutagenesis. The long arm of the cross is an α-helical coiled coil of all three chains, terminating in a cell-adhesive globular region. The molecular basis of cell adhesion to laminins has been revealed by recent structures of heterotrimeric integrin-binding fragments and of a laminin fragment bound to the carbohydrate modification of dystroglycan. The structural characterization of the laminin molecule is essentially complete, but we still have to find ways of imaging native laminin polymers at molecular resolution.

scholarly journals The MLKL kinase-like domain dimerization is an indispensable step of mammalian MLKL activation in necroptosis signaling

2021 ◽  
Vol 12 (7) ◽  
Author(s):  
Yu Zhang ◽  
Jia Liu ◽  
Dandan Yu ◽  
Xinxin Zhu ◽  
Xiaoyan Liu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Self Assembly ◽  
Mammalian Species ◽  
Coiled Coil ◽  
Direct Consequence ◽  
Activation Process ◽  
Sequential Process ◽  
Coiled Coil Region ◽  
And Function ◽  
General Step

AbstractMLKL phosphorylation by RIP3 is the commitment step of necroptosis execution, which could induce MLKL activation featured as MLKL monomer-oligomer transition. Here, we reported that the dimerization of the MLKL kinase-like domain was the direct consequence of RIP3 triggered MLKL-phosphorylation. Two inter-dimer interfaces were found in the crystal structure of human MLKL. Mutations destroying both interfaces could prevent RIP3-induced MLKL oligomerization and necroptosis efficiently. Moreover, we confirmed MLKL self-assembly by the internal coiled-coil region is necessary for MLKL oligomerization and function. The mutations disrupting coiled-coil self-assembly repressed necroptosis, but it did not prevent RIP3-induced dimerization of the MLKL kinase-like domain. So that, MLKL activation is a sequential process, which begins with kinase-like domain dimerization, and followed by internal coiled-coil region self-assembly to form a proper MLKL oligomer. Besides human MLKL, structural and functional analysis showed the kinase-like domain dimerization was conserved among mammalian species, suggesting it is a general step of the RIP3-induced MLKL activation process.

scholarly journals A specific basal body linker protein provides the connection function for basal body inheritance in trypanosomes

2021 ◽  
Vol 118 (8) ◽  
pp. e2014040118
Author(s):  
De-Hua Lai ◽  
Flavia Moreira-Leite ◽  
Zhi-Shen Xu ◽  
Jiong Yang ◽  
Keith Gull
Keyword(s):  
Basal Body ◽  
Mammalian Cells ◽  
De Novo ◽  
Coiled Coil ◽  
Centriole Duplication ◽  
Cytoskeletal Component ◽  
Dividing Cells ◽  
Orthogonal Orientation ◽  
And Function ◽  
Additional Role

Centrioles and basal bodies (CBBs) are found in physically linked pairs, and in mammalian cells intercentriole connections (G1–G2 tether and S–M linker) regulate centriole duplication and function. In trypanosomes BBs are not associated with the spindle and function in flagellum/cilia nucleation with an additional role in mitochondrial genome (kinetoplast DNA [kDNA]) segregation. Here, we describe BBLP, a BB/pro-BB (pBB) linker protein in Trypanosoma brucei predicted to be a large coiled-coil protein conserved in the kinetoplastida. Colocalization with the centriole marker SAS6 showed that BBLP localizes between the BB/pBB pair, throughout the cell cycle, with a stronger signal in the old flagellum BB/pBB pair. Importantly, RNA interference (RNAi) depletion of BBLP leads to a conspicuous splitting of the BB/pBB pair associated only with the new flagellum. BBLP RNAi is lethal in the bloodstream form of the parasite and perturbs mitochondrial kDNA inheritance. Immunogold labeling confirmed that BBLP is localized to a cytoskeletal component of the BB/pBB linker, and tagged protein induction showed that BBLP is incorporated de novo in both new and old flagella BB pairs of dividing cells. We show that the two aspects of CBB disengagement—loss of orthogonal orientation and ability to separate and move apart—are consistent but separable events in evolutionarily diverse cells and we provide a unifying model explaining centriole/BB linkage differences between such cells.

Role of different domains in the self-association of rat nucleoporin p62

1994 ◽  
Vol 107 (2) ◽  
pp. 631-638
Author(s):  
F. Buss ◽  
H. Kent ◽  
M. Stewart ◽  
S.M. Bailer ◽  
J.A. Hanover
Keyword(s):  
Electron Microscopy ◽  
Association Studies ◽  
Coiled Coil ◽  
Small Region ◽  
C Terminus ◽  
Linear Chains ◽  
Beta Structure ◽  
Self Association ◽  
And Function

We have expressed rat nucleoporin p62 cDNA in Escherichia coli to obtain material for structural and self-association studies. Electron microscopy and circular dichroism spectroscopy are consistent with a rod-shaped molecule with an alpha-helical coiled-coil domain at its C terminus and a cross-beta structure at its N terminus, separated by a threonine-rich linker, which has a less-defined secondary structure. Electron microscopy and the solubility properties of fragments produced using thrombin and CNBr digestion indicate that p62 molecules associate to form linear chains and that a small region near the C terminus is an important determinant of assembly. This association may have important consequences for pore structure and function; for example, one way p62 could associate would be to form rings in nuclear pores that could function like barrel hoops.

scholarly journals Atg11 Links Cargo to the Vesicle-forming Machinery in the Cytoplasm to Vacuole Targeting Pathway

2005 ◽  
Vol 16 (4) ◽  
pp. 1593-1605 ◽  
Author(s):  
Tomohiro Yorimitsu ◽  
Daniel J. Klionsky
Keyword(s):  
Self Assembly ◽  
Coiled Coil ◽  
Vesicle Formation ◽  
Selective Autophagy ◽  
C Terminus ◽  
Central Regions ◽  
Putative Site ◽  
Integral Role ◽  
Cargo Molecule

Proteins are selectively packaged into vesicles at specific sites and then delivered correctly to the various organelles where they function, which is critical to the proper physiology of each organelle. The precursor form of the vacuolar hydrolase aminopeptidase I is a selective cargo molecule of the cytoplasm to vacuole targeting (Cvt) pathway and autophagy. Precursor Ape1 along with its receptor Atg19 forms the Cvt complex, which is transported to the pre-autophagosomal structure (PAS), the putative site of Cvt vesicle formation, in a process dependent on Atg11. Here, we show that this interaction occurs through the Atg11 C terminus; subsequent recruitment of the Cvt complex to the PAS depends on central regions within Atg11. Atg11 was shown to physically link several proteins, although the timing of these interactions and their importance are unknown. Our mapping shows that the Atg11 coiled-coil domains are involved in self-assembly and the interaction with other proteins, including two previously unidentified partners, Atg17 and Atg20. Atg11 mutants defective in the transport of the Cvt complex to the PAS affect the localization of other Atg components, supporting the idea that the cargo facilitates the organization of the PAS in selective autophagy. These findings suggest that Atg11 plays an integral role in connecting cargo molecules with components of the vesicle-forming machinery.

scholarly journals Identification and Characterisation of Putative Enhancer Elements in Mouse Embryonic Stem Cells

2021 ◽  
Vol 15 ◽  
pp. 117793222097462
Author(s):  
Anna Mantsoki ◽  
Karla Parussel ◽  
Anagha Joshi
Keyword(s):  
De Novo ◽  
Es Cells ◽  
Embryonic Stem ◽  
Data Sets ◽  
Simultaneous Presence ◽  
Enhancer Activity ◽  
Cellular Context ◽  
Distinct Sequence ◽  
A Cell ◽  
And Function

Enhancer elements control mammalian transcription largely in a cell-type-specific manner. The genome-wide identification of enhancer elements and their activity status in a cellular context is therefore fundamental to understanding cell identity and function. We determined enhancer activity in mouse embryonic stem (ES) cells using chromatin modifications and characterised their global properties. Specifically, we first grouped enhancers into 5 groups using multiple H3K4me1, H3K27ac, and H3K27me3 modification data sets. Active enhancers (simultaneous presence of H3K4me1 and H3K27ac) were enriched for binding of pluripotency factors and were found near pluripotency-related genes. Although both H3K4me1-only and active enhancers were enriched for super-enhancers and a TATA box like motif, active enhancers were preferentially bound by RNA polII (s2) and were enriched for bidirectional transcription, while H3K4me1-only enhancers were enriched for RNA polII (8WG16) suggesting they were likely poised. Bivalent enhancers (simultaneous presence of H3K4me1 and H3K27me3) were preferentially in the vicinity of bivalent genes. They were enriched for binding of components of polycomb complex as well as Tcf3 and Oct4. Moreover, a ‘CTTTCTC’ de-novo motif was enriched at bivalent enhancers, previously identified at bivalent promoters in ES cells. Taken together, 3 histone modifications successfully demarcated active, bivalent, and poised enhancers with distinct sequence and binding features.

scholarly journals ESCRT-III acts in scissioning new peroxisomes from the ER

2017 ◽  
Author(s):  
Fred D. Mast ◽  
Thurston Herricks ◽  
Kathleen M. Strehler ◽  
Leslie R. Miller ◽  
Ramsey A. Saleem ◽  
...  
Keyword(s):  
De Novo ◽  
Genetic Disorders ◽  
Dynamic Control ◽  
Eukaryotic Cell ◽  
Peroxisome Biogenesis ◽  
Endosomal Sorting ◽  
Obesity And Diabetes ◽  
A Cell ◽  
And Function

AbstractDynamic control of peroxisome proliferation is integral to the peroxisome’s many functions. A breakdown in the ability of cells to form peroxisomes is linked to many human health issues, including defense against infectious agents, cancer, aging, heart disease, obesity and diabetes, and forms the basis of a spectrum of peroxisomal genetic disorders that cause severe neuropathologies. The ER serves as a source for preperoxisomal vesicles (PPVs) that mature into peroxisomes during de novo peroxisome biogenesis and to support growth and division of existing peroxisomes. However, the mechanism of PPV formation and release from the ER remains poorly understood. Here we show that the evolutionarily ancient endosomal sorting complexes required for transport (ESCRT)-III are peroxisome biogenesis factors that function to cleave PPVs budding from the ER into the cytosol. Using comprehensive morphological and genetic assays of peroxisome formation and function we find that absence of ESCRT-III proteins impedes de novo peroxisome formation and results in an aberrant peroxisome population in vivo. Using a cell-free PPV budding assay we show that ESCRT-III proteins Vps20 and Snf7 are required to release PPVs from the ER. ESCRT-III is therefore a positive effector of membrane scission for vesicles budding both away from and towards the cytosol, a finding that has important implications for the evolutionary timing of emergence of peroxisomes and the rest of the internal membrane architecture of the eukaryotic cell.

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