scholarly journals Novel plant SUN–KASH bridges are involved in RanGAP anchoring and nuclear shape determination

2012 ◽  
Vol 196 (2) ◽  
pp. 203-211 ◽  
Author(s):  
Xiao Zhou ◽  
Katja Graumann ◽  
David E. Evans ◽  
Iris Meier
Keyword(s):  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Epidermal Cells ◽  
Nuclear Shape ◽  
Interacting Proteins ◽  
Outer Nuclear Membrane ◽  
Plant Kingdom ◽  
Inner Nuclear Membrane ◽  
Shape Determination

Inner nuclear membrane Sad1/UNC-84 (SUN) proteins interact with outer nuclear membrane (ONM) Klarsicht/ANC-1/Syne homology (KASH) proteins, forming linkers of nucleoskeleton to cytoskeleton conserved from yeast to human and involved in positioning of nuclei and chromosomes. Defects in SUN–KASH bridges are linked to muscular dystrophy, progeria, and cancer. SUN proteins were recently identified in plants, but their ONM KASH partners are unknown. Arabidopsis WPP domain–interacting proteins (AtWIPs) are plant-specific ONM proteins that redundantly anchor Arabidopsis RanGTPase–activating protein 1 (AtRanGAP1) to the nuclear envelope (NE). In this paper, we report that AtWIPs are plant-specific KASH proteins interacting with Arabidopsis SUN proteins (AtSUNs). The interaction is required for both AtWIP1 and AtRanGAP1 NE localization. AtWIPs and AtSUNs are necessary for maintaining the elongated nuclear shape of Arabidopsis epidermal cells. Together, our data identify the first KASH members in the plant kingdom and provide a novel function of SUN–KASH complexes, suggesting that a functionally diverged SUN–KASH bridge is conserved beyond the opisthokonts.

scholarly journals Loss of a-Type Lamin Expression Compromises Nuclear Envelope Integrity Leading to Muscular Dystrophy

1999 ◽  
Vol 147 (5) ◽  
pp. 913-920 ◽  
Author(s):  
Teresa Sullivan ◽  
Diana Escalante-Alcalde ◽  
Harshida Bhatt ◽  
Miriam Anver ◽  
Narayan Bhat ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Mammalian Cells ◽  
Nuclear Architecture ◽  
Nuclear Lamina ◽  
Postnatal Growth ◽  
Developmentally Regulated ◽  
Inner Nuclear Membrane ◽  
Cardiac Muscles

The nuclear lamina is a protein meshwork lining the nucleoplasmic face of the inner nuclear membrane and represents an important determinant of interphase nuclear architecture. Its major components are the A- and B-type lamins. Whereas B-type lamins are found in all mammalian cells, A-type lamin expression is developmentally regulated. In the mouse, A-type lamins do not appear until midway through embryonic development, suggesting that these proteins may be involved in the regulation of terminal differentiation. Here we show that mice lacking A-type lamins develop to term with no overt abnormalities. However, their postnatal growth is severely retarded and is characterized by the appearance of muscular dystrophy. This phenotype is associated with ultrastructural perturbations to the nuclear envelope. These include the mislocalization of emerin, an inner nuclear membrane protein, defects in which are implicated in Emery-Dreifuss muscular dystrophy (EDMD), one of the three major X-linked dystrophies. Mice lacking the A-type lamins exhibit tissue-specific alterations to their nuclear envelope integrity and emerin distribution. In skeletal and cardiac muscles, this is manifest as a dystrophic condition related to EDMD.

scholarly journals Atg39 selectively captures inner nuclear membrane into lumenal vesicles for delivery to the autophagosome

2021 ◽  
Author(s):  
Sunandini Chandra ◽  
Philip J. Mannino ◽  
David J. Thaller ◽  
Nicholas R. Ader ◽  
Megan C. King ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Electron Tomography ◽  
Membrane Remodeling ◽  
Outer Nuclear Membrane ◽  
Inner Nuclear Membrane ◽  
Gfp Reporter ◽  
Sequence Elements ◽  
Lumenal Domain

AbstractMechanisms that turnover components of the nucleus and inner nuclear membrane (INM) remain to be fully defined. We explore how components of the INM are selected by a cytosolic autophagy apparatus through a transmembrane nuclear envelope-localized cargo adaptor, Atg39. A split-GFP reporter shows that Atg39 localizes to the outer nuclear membrane (ONM) and thus targets the INM across the nuclear envelope lumen. Consistent with this, sequence elements that confer both nuclear envelope localization and a membrane remodeling activity are mapped to the Atg39 lumenal domain; these lumenal motifs are required for the autophagy-mediated degradation of an integral INM protein. Interestingly, correlative light and electron tomography shows that the overexpression of Atg39 leads to the expansion of the ONM and the enclosure of a network of INM-derived vesicles in the nuclear envelope lumen. Thus, we propose an outside-in model of nucleophagy where INM is delivered into vesicles in the nuclear envelope lumen, which can be targeted by the autophagosome.

The Emery-Dreifuss muscular dystrophy phenotype arises from aberrant targeting and binding of emerin at the inner nuclear membrane

1999 ◽  
Vol 112 (15) ◽  
pp. 2571-2582 ◽  
Author(s):  
E.A. Fairley ◽  
J. Kendrick-Jones ◽  
J.A. Ellis
Keyword(s):  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Complete Removal ◽  
Wild Type ◽  
Transmembrane Region ◽  
C2c12 Myoblasts ◽  
Inner Nuclear Membrane ◽  
Membrane Spanning ◽  
Mutant Forms

The product of the X-linked Emery-Dreifuss muscular dystrophy gene is a single-membrane-spanning protein called emerin, which is localized to the inner nuclear membrane of all tissues studied. To examine whether a number of the mutant forms of emerin expressed in patients are mislocalized, we transfected GFP-emerin cDNA constructs reflecting these mutations into undifferentiated C2C12 myoblasts and showed that both wild type and all the mutant emerins are targeted to the nuclear membrane, but the mutants to a lesser extent. Mutant Del236-241 (deletion in transmembrane region) was mainly expressed as cytoplasmic aggregates, with only trace amounts at the nuclear envelope. Complete removal of the transmembrane region and C-terminal tail relocated emerin to the nucleoplasm. Mutations in emerin's N-terminal domain had a less severe effect on disrupting nuclear envelope targeting. This data suggests that emerin contains multiple non-overlapping nuclear-membrane-targeting determinants. Analysis of material immunoisolated using emerin antibodies, from either undifferentiated C2C12 myoblasts or purified hepatocyte nuclei, demonstrated that both A- and B-type lamins and nuclear actin interact with emerin. This is the first report of proteins interacting with emerin. The EDMD phenotype can thus arise by either the absence or a reduction in emerin at the nuclear envelope, and both of these disrupt its interactions with that of structural components of the nucleus. We propose that an emerin-nuclear protein complex exists at the nuclear envelope and that one of its primary roles is to stabilize the nuclear membrane against the mechanical stresses that are generated in muscle cells during contraction.

scholarly journals Myne-1, a spectrin repeat transmembrane protein of the myocyte inner nuclear membrane, interacts with lamin A/C

2002 ◽  
Vol 115 (1) ◽  
pp. 61-70 ◽  
Author(s):  
John M. K. Mislow ◽  
Marian S. Kim ◽  
Dawn Belt Davis ◽  
Elizabeth M. McNally
Keyword(s):  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Transmembrane Domain ◽  
Transmembrane Protein ◽  
Lamin A ◽  
Spectrin Repeat ◽  
Inner Nuclear Membrane ◽  
C Terminus

Mutations in the genes encoding the inner nuclear membrane proteins lamin A/C and emerin produce cardiomyopathy and muscular dystrophy in humans and mice. The mechanism by which these broadly expressed gene products result in tissue-specific dysfunction is not known. We have identified a protein of the inner nuclear membrane that is highly expressed in striated and smooth muscle. This protein, myne-1 (myocyte nuclear envelope), is predicted to have seven spectrin repeats, an interrupted LEM domain and a single transmembrane domain at its C-terminus. We found that myne-1 is expressed upon early muscle differentiation in multiple intranuclear foci concomitant with lamin A/C expression. In mature muscle, myne-1 and lamin A/C are perfectly colocalized, although colocalization with emerin is only partial. Moreover, we show that myne-1 and lamin A/C coimmunoprecipitate from differentiated muscle in vitro. The muscle-specific inner nuclear envelope expression of myne-1, along with its interaction with lamin A/C, indicates that this gene is a potential mediator of cardiomyopathy and muscular dystrophy.

scholarly journals Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection

F1000Research ◽  
2018 ◽  
Vol 6 ◽  
pp. 1804 ◽  
Author(s):  
Peter Wild ◽  
Andres Kaech ◽  
Elisabeth M. Schraner ◽  
Ladina Walser ◽  
Mathias Ackermann
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Golgi Complex ◽  
Nuclear Membrane ◽  
Progeny Virus ◽  
Cytoplasmic Matrix ◽  
Outer Nuclear Membrane ◽  
Nuclear Membranes ◽  
Perinuclear Space ◽  
Hsv 1

Background: Herpesvirus capsids are assembled in the nucleus, translocated to the perinuclear space by budding, acquiring tegument and envelope, or released to the cytoplasm via impaired nuclear envelope. One model proposes that envelopment, “de-envelopment” and “re-envelopment” is essential for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the “primary” envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of alternative exit routes.Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols.Results:  The Golgi complex is a compact entity in a juxtanuclear position covered by a membrane on thecisface. Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced.Conclusions: The data suggest that virions derived by budding at nuclear membranes are intraluminally transported from the perinuclear space via Golgi -endoplasmic reticulum transitions into Golgi cisternae for packaging. Virions derived by budding at nuclear membranes are infective like Us3 deletion mutants, which  accumulate in the perinuclear space. Therefore, i) de-envelopment followed by re-envelopment is not essential for production of infective progeny virus, ii) the process taking place at the outer nuclear membrane is budding not fusion, and iii) naked capsids gain access to the cytoplasmic matrix via impaired nuclear envelope as reported earlier.

scholarly journals Unrestrained ESCRT-III drives chromosome fragmentation and micronuclear catastrophe

2019 ◽  
Author(s):  
Marina Vietri ◽  
Sebastian W. Schultz ◽  
Aurélie Bellanger ◽  
Carl M. Jones ◽  
Camilla Raiborg ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Genome Stability ◽  
Membrane Deformation ◽  
Chromosome Fragmentation ◽  
Inner Nuclear Membrane ◽  
Membrane Rupture ◽  
Membrane Fission ◽  
Stable Association ◽  
Inner Nuclear Membrane Protein

AbstractThe ESCRT-III membrane fission machinery1,2 restores nuclear envelope integrity during mitotic exit3,4 and interphase5,6. Whereas primary nuclei resealing takes minutes, micronuclear envelope ruptures appear irreversible and result in catastrophic collapse associated with chromosome fragmentation and rearrangements (chromothripsis), thought to be a major driving force in cancer development7-10. Despite its importance11-13, the mechanistic underpinnings of nuclear envelope sealing in primary nuclei and the defects observed in micronuclei remain largely unknown. Here we show that CHMP7, the nucleator of ESCRT-III filaments at the nuclear envelope3,14, and the inner nuclear membrane protein LEMD215 act as a compartmentalization sensor detecting the loss of nuclear integrity. In cells with intact nuclear envelope, CHMP7 is actively excluded from the nucleus to preclude its binding to LEMD2. Nuclear influx of CHMP7 results in stable association with LEMD2 at the inner nuclear membrane that licenses local polymerization of ESCRT-III. Tight control of nuclear CHMP7 levels is critical, as induction of nuclear CHMP7 mutants is sufficient to induce unrestrained growth of ESCRT-III foci at the nuclear envelope, causing dramatic membrane deformation, local DNA torsional stress, single-stranded DNA formation and fragmentation of the underlying chromosomes. At micronuclei, membrane rupture is not associated with repair despite timely recruitment of ESCRT-III. Instead, micronuclei inherently lack the capacity to restrict accumulation of CHMP7 and LEMD2. This drives unrestrained ESCRT-III recruitment, membrane deformation and DNA defects that strikingly resemble those at primary nuclei upon induction of nuclear CHMP7 mutants. Preventing ESCRT-III recruitment suppresses membrane deformation and DNA damage, without restoring nucleocytoplasmic compartmentalization. We propose that the ESCRT-III nuclear integrity surveillance machinery is a double-edged sword, as its exquisite sensitivity ensures rapid repair at primary nuclei while causing unrestrained polymerization at micronuclei, with catastrophic consequences for genome stability16-18.

Function and assembly of nuclear pore complex proteins

1999 ◽  
Vol 77 (4) ◽  
pp. 321-329 ◽  
Author(s):  
Khaldon Bodoor ◽  
Sarah Shaikh ◽  
Paul Enarson ◽  
Sharmin Chowdhury ◽  
Davide Salina ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Current View ◽  
Nuclear Pore ◽  
Dynamic Component ◽  
Inner Nuclear Membrane ◽  
Inner Nuclear Membrane Protein ◽  
Nuclear Membrane Protein

Nuclear pore complexes (NPCs) are extremely elaborate structures that mediate the bidirectional movement of macromolecules between the nucleus and cytoplasm. The current view of NPC organization features a massive symmetrical framework that is embedded in the double membranes of the nuclear envelope. It embraces a central channel of as yet ill-defined structure but which may accommodate particles with diameters up to 26 nm provided that they bear specific import/export signals. Attached to both faces of the central framework are peripheral structures, short cytoplasmic filaments, and a nuclear basket assembly, which interact with molecules transiting the NPC. The mechanisms of assembly and the nature of NPC structural intermediates are still poorly understood. However, mutagenesis and expression studies have revealed discrete sequences within certain NPC proteins that are necessary and sufficient for their appropriate targeting. In addition, some details are emerging from observations on cells undergoing mitosis where the nuclear envelope is disassembled and its components, including NPC subunits, are dispersed throughout the mitotic cytoplasm. At the end of mitosis, all of these components are reutilized to form nuclear envelopes in the two daughter cells. To date, it has been possible to define a time course of postmitotic assembly for a group of NPC components (CAN/Nup214, Nup153, POM121, p62 and Tpr) relative to the integral inner nuclear membrane protein LAP2 and the NPC membrane glycoprotein gp210. Nup153, a dynamic component of the nuclear basket, associates with chromatin towards the end of anaphase coincident with, although independent of, the inner nuclear membrane protein, LAP2. Assembly of the remaining proteins follows that of the nuclear membranes and occurs in the sequence POM121, p62, CAN/Nup214 and gp210/Tpr. Since p62 remains as a complex with three other NPC proteins (p58, p54, p45) during mitosis, and CAN/Nup214 maintains a similar interaction with its partner, Nup84, the relative timing of assembly of these additional four proteins may also be inferred. These observations suggest that there is a sequential association of NPC proteins with chromosomes during nuclear envelope reformation and the recruitment of at least eight of these precedes that of gp210. These findings support a model in which it is POM121 rather than gp210 that defines initial membrane-associated NPC assembly intermediates and which may therefore represent an essential component of the central framework of the NPC. Key words: nuclear pore complex, nucleoporin, mitosis, nuclear transport

scholarly journals SUN-1 and ZYG-12, Mediators of Centrosome–Nucleus Attachment, Are a Functional SUN/KASH Pair in Caenorhabditis elegans

2009 ◽  
Vol 20 (21) ◽  
pp. 4586-4595 ◽  
Author(s):  
IL Minn ◽  
Melissa M. Rolls ◽  
Wendy Hanna-Rose ◽  
Christian J. Malone
Keyword(s):  
Caenorhabditis Elegans ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Coiled Coil ◽  
Physical Interaction ◽  
Type Ii ◽  
Inner Nuclear Membrane ◽  
Sequence Elements ◽  
Inner Nuclear Membrane Protein ◽  
Sun Domain

Klarsicht/ANC-1/Syne/homology (KASH)/Sad-1/UNC-84 (SUN) protein pairs can act as connectors between cytoplasmic organelles and the nucleoskeleton. Caenorhabditis elegans ZYG-12 and SUN-1 are essential for centrosome–nucleus attachment. Although SUN-1 has a canonical SUN domain, ZYG-12 has a divergent KASH domain. Here, we establish that the ZYG-12 mini KASH domain is functional and, in combination with a portion of coiled-coil domain, is sufficient for nuclear envelope localization. ZYG-12 and SUN-1 are hypothesized to be outer and inner nuclear membrane proteins, respectively, and to interact, but neither their topologies nor their physical interaction has been directly investigated. We show that ZYG-12 is a type II outer nuclear membrane (ONM) protein and that SUN-1 is a type II inner nuclear membrane protein. The proteins interact in the luminal space of the nuclear envelope via the ZYG-12 mini KASH domain and a region of SUN-1 that does not include the SUN domain. SUN-1 is hypothesized to restrict ZYG-12 to the ONM, preventing diffusion through the endoplasmic reticulum. We establish that ZYG-12 is indeed immobile at the ONM by using fluorescence recovery after photobleaching and show that SUN-1 is sufficient to localize ZYG-12 in cells. This work supports current models of KASH/SUN pairs and highlights the diversity in sequence elements defining KASH domains.

scholarly journals SINC, a type III secreted protein of Chlamydia psittaci, targets the inner nuclear membrane of infected cells and uninfected neighbors

2015 ◽  
Vol 26 (10) ◽  
pp. 1918-1934 ◽  
Author(s):  
Sergio A. Mojica ◽  
Kelley M. Hovis ◽  
Matthew B. Frieman ◽  
Bao Tran ◽  
Ru-ching Hsia ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Chlamydia Psittaci ◽  
Hek293 Cells ◽  
Secreted Protein ◽  
Inner Nuclear Membrane ◽  
Type Iii ◽  
Infected Cells ◽  
Digitonin Permeabilization

SINC, a new type III secreted protein of the avian and human pathogen Chlamydia psittaci, uniquely targets the nuclear envelope of C. psittaci–infected cells and uninfected neighboring cells. Digitonin-permeabilization studies of SINC-GFP–transfected HeLa cells indicate that SINC targets the inner nuclear membrane. SINC localization at the nuclear envelope was blocked by importazole, confirming SINC import into the nucleus. Candidate partners were identified by proximity to biotin ligase-fused SINC in HEK293 cells and mass spectrometry (BioID). This strategy identified 22 candidates with high confidence, including the nucleoporin ELYS, lamin B1, and four proteins (emerin, MAN1, LAP1, and LBR) of the inner nuclear membrane, suggesting that SINC interacts with host proteins that control nuclear structure, signaling, chromatin organization, and gene silencing. GFP-SINC association with the native LEM-domain protein emerin, a conserved component of nuclear “lamina” structure, or with a complex containing emerin was confirmed by GFP pull down. Our findings identify SINC as a novel bacterial protein that targets the nuclear envelope with the capability of globally altering nuclear envelope functions in the infected host cell and neighboring uninfected cells. These properties may contribute to the aggressive virulence of C. psittaci.

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