scholarly journals Nesprins: a novel family of spectrin-repeat-containing proteins that localize to the nuclear membrane in multiple tissues

2001 ◽  
Vol 114 (24) ◽  
pp. 4485-4498 ◽  
Author(s):  
Qiuping Zhang ◽  
Jeremy N. Skepper ◽  
Fangtang Yang ◽  
John D. Davies ◽  
Laszlo Hegyi ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Structural Integrity ◽  
Transmembrane Domain ◽  
Myoblast Differentiation ◽  
C2c12 Myoblast ◽  
Differentiation Markers ◽  
Spectrin Repeat ◽  
New Family ◽  
Genes Encoding

In search of vascular smooth muscle cell differentiation markers, we identified two genes encoding members of a new family of type II integral membrane proteins. Both are ubiquitously expressed, and tissue-specific alternative mRNA initiation and splicing generate at least two major isoforms of each protein, with the smaller isoforms being truncated at the N-terminus. We have named these proteins nesprin-1 and -2 for nuclear envelope spectrin repeat, as they are characterized by the presence of multiple, clustered spectrin repeats, bipartite nuclear localization sequences and a conserved C-terminal, single transmembrane domain. Transient transfection of EGFP-fusion expression constructs demonstrated their localization to the nuclear membrane with a novel C-terminal, TM-domain-containing sequence essential for perinuclear localization. Using antibodies to nesprin-1, we documented its colocalization with LAP1, emerin and lamins at the nuclear envelope, and immunogold labeling confirmed its presence at the nuclear envelope and in the nucleus where it colocalized with heterochromatin. Nesprin-1 is developmentally regulated in both smooth and skeletal muscle and is re-localized from the nuclear envelope to the nucleus and cytoplasm during C2C12 myoblast differentiation. These data and structural analogies with other proteins suggest that nesprins may function as ‘dystrophins of the nucleus’ to maintain nuclear organization and structural integrity.

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.

Patterns of evolutionary conservation in the nesprin genes highlight probable functionally important protein domains and isoforms

2008 ◽  
Vol 36 (6) ◽  
pp. 1359-1367 ◽  
Author(s):  
Jennifer G. Simpson ◽  
Roland G. Roberts
Keyword(s):  
Nuclear Envelope ◽  
Expressed Sequence Tag ◽  
Sequence Data ◽  
Actin Binding ◽  
Structural Elements ◽  
Spectrin Repeat ◽  
Protein Protein Interaction ◽  
Common Structure ◽  
Genes Encoding ◽  
Membrane Bound

The nesprins [also known as SYNEs (synaptic nuclear envelope proteins)] are a family of type II transmembrane proteins implicated in the tethering of membrane-bound organelles and in the genetic aetiology of cerebellar ataxia and Emery–Dreifuss muscular dystrophy. They are characterized by a common structure of an SR (spectrin repeat) rod domain and a C-terminal transmembrane KLS (klarsicht)/KASH [klarsicht/ANC-1 (anchorage 1)/SYNE homology] domain which interacts with SUN [Sad1p/UNC (uncoordinated)-84] proteins in the nuclear envelope; most nesprins also have N-terminal actin-binding CH (calponin homology) domains. The genes encoding the three vertebrate nesprins (five in bony fish) and the small transmembrane actin-binding protein calmin are related to each other by ancient duplications and rearrangements. In the present paper, we collate sequence data for nesprins and calmins across the vertebrate clade and use these to study evolutionary constraints acting on their genes. We show that the rod domains of the larger nesprins are composed almost entirely of unbroken SR-like structures (74 in nesprin-1 and 56 in nesprin-2) and that these range from poorly conserved purely structural elements to highly conserved regions with a presumed protein–protein interaction function. The analysis suggests several interesting regions for future study. We also assess the evolutionary and EST (expressed sequence tag) expression support for nesprin isoforms, both known and novel; our findings suggest that substantial reassessment is required.

Nesprins: intracellular scaffolds that maintain cell architecture and coordinate cell function?

2005 ◽  
Vol 7 (11) ◽  
pp. 1-15 ◽  
Author(s):  
Derek T. Warren ◽  
Qiuping Zhang ◽  
Peter L Weissberg ◽  
Catherine M. Shanahan
Keyword(s):  
Nuclear Membrane ◽  
Cell Function ◽  
Transmembrane Domain ◽  
Protein Isoforms ◽  
Actin Binding ◽  
Transcriptional Initiation ◽  
Spectrin Repeat ◽  
Cell Architecture ◽  
Intracellular Proteins ◽  
Intracellular Organelles

Nesprins are a recently discovered family of ubiquitously expressed intracellular proteins. Through alternative transcriptional initiation, termination and splicing, two genes – nesprin-1 and nesprin-2 (also known as syne-1 and syne-2) – give rise to many protein isoforms that vary markedly in size. The largest of these isoforms comprise a C-terminal transmembrane domain (the KLS domain) linked by a spectrin-repeat rod domain to an N-terminal paired, actin-binding, calponin-homology domain. This structure suggests that they are well suited to orchestrate signalling between cell membranes and the cytoskeleton. Other isoforms have variable lengths of this rod domain linked to either end of the protein. Smaller isoforms with the KLS domain are localised at the inner nuclear membrane, where they bind lamin A/C and emerin. Larger nesprin isoforms link the outer nuclear membrane with intracellular organelles and the actin cytoskeleton and are thought to regulate nuclear anchorage and organelle migration. Thus, nesprins might have a variety of fundamental roles in cells, particularly muscle cells where they are highly expressed. We speculate that nesprin mutations might contribute to a broad range of human disease syndromes, including laminopathies.

Nesprin-3: a versatile connector between the nucleus and the cytoskeleton

2011 ◽  
Vol 39 (6) ◽  
pp. 1719-1724 ◽  
Author(s):  
Mirjam Ketema ◽  
Arnoud Sonnenberg
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Actin Filaments ◽  
Structural Integrity ◽  
Nuclear Lamina ◽  
Cross Linking ◽  
Indirect Interaction ◽  
Direct Link ◽  
Nuclear Interior

The cytoskeleton is connected to the nuclear interior by LINC (linker of nucleoskeleton and cytoskeleton) complexes located in the nuclear envelope. These complexes consist of SUN proteins and nesprins present in the inner and outer nuclear membrane respectively. Whereas SUN proteins can bind the nuclear lamina, members of the nesprin protein family connect the nucleus to different components of the cytoskeleton. Nesprin-1 and -2 can establish a direct link with actin filaments, whereas nesprin-4 associates indirectly with microtubules through its interaction with kinesin-1. Nesprin-3 is the only family member known that can link the nuclear envelope to intermediate filaments. This indirect interaction is mediated by the binding of nesprin-3 to the cytoskeletal linker protein plectin. Furthermore, nesprin-3 can connect the nucleus to microtubules by its interactions with BPAG1 (bullous pemphigoid antigen 1) and MACF (microtubule–actin cross-linking factor). In contrast with the active roles that nesprin-1, -2 and -4 have in actin- and microtubule-dependent nuclear positioning, the role of nesprin-3 is likely to be more passive. We suggest that it helps to stabilize the anchorage of the nucleus within the cytoplasm and maintain the structural integrity and shape of the nucleus.

scholarly journals The nucleoporin gp210/Nup210 controls muscle differentiation by regulating nuclear envelope/ER homeostasis

2015 ◽  
Vol 208 (6) ◽  
pp. 671-681 ◽  
Author(s):  
J. Sebastian Gomez-Cavazos ◽  
Martin W. Hetzer
Keyword(s):  
Cell Differentiation ◽  
Nuclear Envelope ◽  
Er Stress ◽  
Myoblast Differentiation ◽  
Nuclear Pore ◽  
C2c12 Myoblast ◽  
Terminal Domain ◽  
Er Homeostasis

Previously, we identified the nucleoporin gp210/Nup210 as a critical regulator of muscle and neuronal differentiation, but how this nucleoporin exerts its function and whether it modulates nuclear pore complex (NPC) activity remain unknown. Here, we show that gp210/Nup210 mediates muscle cell differentiation in vitro via its conserved N-terminal domain that extends into the perinuclear space. Removal of the C-terminal domain, which partially mislocalizes gp210/Nup210 away from NPCs, efficiently rescues the differentiation defect caused by the knockdown of endogenous gp210/Nup210. Unexpectedly, a gp210/Nup210 mutant lacking the NPC-targeting transmembrane and C-terminal domains is sufficient for C2C12 myoblast differentiation. We demonstrate that the endoplasmic reticulum (ER) stress-specific caspase cascade is exacerbated during Nup210 depletion and that blocking ER stress-mediated apoptosis rescues differentiation of Nup210-deficient cells. Our results suggest that the role of gp210/Nup210 in cell differentiation is mediated by its large luminal domain, which can act independently of NPC association and appears to play a pivotal role in the maintenance of nuclear envelope/ER homeostasis.

The cell cycle dependent mislocalisation of emerin may contribute to the Emery-Dreifuss muscular dystrophy phenotype

2002 ◽  
Vol 115 (2) ◽  
pp. 341-354 ◽  
Author(s):  
Elizabeth A. L. Fairley ◽  
Andrew Riddell ◽  
Juliet A. Ellis ◽  
John Kendrick-Jones
Keyword(s):  
Cell Cycle ◽  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Transmembrane Domain ◽  
Nuclear Lamina ◽  
Lamin A ◽  
Wild Type ◽  
Cycle Dependent ◽  
Mutant Forms

Emerin is the nuclear membrane protein defective in X-linked Emery-Dreifuss muscular dystrophy (X-EDMD). The majority of X-EDMD patients have no detectable emerin. However, there are cases that produce mutant forms of emerin, which can be used to study its function. Our previous studies have shown that the emerin mutants S54F, P183T, P183H, Del95-99, Del236-241 (identified in X-EDMD patients) are targeted to the nuclear membrane but to a lesser extent than wild-type emerin. In this paper, we have studied how the mislocalisation of these mutant emerins may affect nuclear functions associated with the cell cycle using flow cytometry and immunofluorescence microscopy. We have established that cells expressing the emerin mutant Del236-241 (a deletion in the transmembrane domain), which was mainly localised in the cytoplasm, exhibited an aberrant cell cycle length. Thereafter, by examining the intracellular localisation of endogenously expressed lamin A/C and exogenously expressed wild-type and mutant forms of emerin after a number of cell divisions, we determined that the mutant forms of emerin redistributed endogenous lamin A/C. The extent of lamin A/C redistribution correlated with the amount of EGFP-emerin that was mislocalised. The amount of EGFP-emerin mislocalized, in turn, was associated with alterations in the nuclear envelope morphology. The nuclear morphology and redistribution of lamin A/C was most severely affected in the cells expressing the emerin mutant Del236-241.It is believed that emerin is part of a novel nuclear protein complex consisting of the barrier-to-autointegration factor (BAF), the nuclear lamina, nuclear actin and other associated proteins. The data presented here show that lamin A/C localisation is dominantly directed by its interaction with certain emerin mutants and perhaps wild-type emerin as well. These results suggest that emerin links A-type lamins to the nuclear envelope and that the correct localisation of these nuclear proteins is important for maintaining cell cycle timing.

scholarly journals Targeting of LRRC59 to the Endoplasmic Reticulum and the Inner Nuclear Membrane

2019 ◽  
Vol 20 (2) ◽  
pp. 334 ◽  
Author(s):  
Marina Blenski ◽  
Ralph Kehlenbach
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Nuclear Import ◽  
Transmembrane Domain ◽  
Membrane Insertion ◽  
Leucine Rich Repeat ◽  
Inner Nuclear Membrane ◽  
Importin Α ◽  
Major Route

LRRC59 (leucine-rich repeat-containing protein 59) is a tail-anchored protein with a single transmembrane domain close to its C-terminal end that localizes to the endoplasmic reticulum (ER) and the nuclear envelope. Here, we investigate the mechanisms of membrane integration of LRRC59 and its targeting to the inner nuclear membrane (INM). Using purified microsomes, we show that LRRC59 can be post-translationally inserted into ER-derived membranes. The TRC-pathway, a major route for post-translational membrane insertion, is not required for LRRC59. Like emerin, another tail-anchored protein, LRRC59 reaches the INM, as demonstrated by rapamycin-dependent dimerization assays. Using different approaches to inhibit importin α/β-dependent nuclear import of soluble proteins, we show that the classic nuclear transport machinery does not play a major role in INM-targeting of LRRC59. Instead, the size of the cytoplasmic domain of LRRC59 is an important feature, suggesting that targeting is governed by passive diffusion.

scholarly journals Analysis of the Complete Genome Sequence of the Hz-1 Virus Suggests that It Is Related to Members of the Baculoviridae

2002 ◽  
Vol 76 (18) ◽  
pp. 9024-9034 ◽  
Author(s):  
Chia-Hsiung Cheng ◽  
Su-Mei Liu ◽  
Teh-Yuan Chow ◽  
Yu-Yun Hsiao ◽  
Dan-Ping Wang ◽  
...  
Keyword(s):  
Transmembrane Domain ◽  
Large Subunit ◽  
Heliothis Zea ◽  
Virus Genome ◽  
Complete Sequence ◽  
Open Reading Frames ◽  
New Family ◽  
C Terminus ◽  
Cellular Genes ◽  
Genes Encoding

ABSTRACT We report the complete sequence of a large rod-shaped DNA virus, called the Hz-1 virus. This virus persistently infects the Heliothis zea cell lines. The Hz-1 virus has a double-stranded circular DNA genome of 228,089 bp encoding 154 open reading frames (ORFs) and also expresses a persistence-associated transcript 1, PAT1. The G+C content of the Hz-1 virus genome is 41.8%, with a gene density of one gene per 1.47 kb. Sequence analysis revealed that a 9.6-kb region at 43.6 to 47.8 map units harbors five cellular genes encoding proteins with homology to dUTP pyrophosphatase, matrix metalloproteinase, deoxynucleoside kinase, glycine hydroxymethyltransferase, and ribonucleotide reductase large subunit. Other cellular homologs were also detected dispersed in the viral genome. Several baculovirus homologs were detected in the Hz-1 virus genome. These include PxOrf-70, PxOrf-29, AcOrf-81, AcOrf-96, AcOrf-22, VLF-1, RNA polymerase LEF-8 (orf50), and two structural proteins, p74 and p91. The Hz-1 virus p74 homolog shows high structural conservation with a double transmembrane domain at its C terminus. Phylogenetic analysis of the p74 revealed that the Hz-1 virus is evolutionarily distant from the baculoviruses. Another distinctive feature of the Hz-1 virus genome is a gene that is involved in insect development. However, the remainder of the ORFs (81%) encoded proteins that bear no homology to any known proteins. In conclusion, the sequence differences between the Hz-1 virus and the baculoviruses outnumber the similarities and suggest that the Hz-1 virus may form a new family of viruses distantly related to the Baculoviridae.

The role of nesprins as multifunctional organizers in the nucleus and the cytoskeleton

2011 ◽  
Vol 39 (6) ◽  
pp. 1725-1728 ◽  
Author(s):  
Angelika A. Noegel ◽  
Sascha Neumann
Keyword(s):  
Nuclear Envelope ◽  
Lipid Bilayers ◽  
Nuclear Membrane ◽  
Envelope Protein ◽  
Membrane System ◽  
Outer Nuclear Membrane ◽  
Spectrin Repeat ◽  
Nuclear Membranes ◽  
Repeat Proteins

Nesprins (nuclear envelope spectrin repeat proteins), also known as SYNE (synaptic nuclear envelope protein), MYNE (myocyte nuclear envelope protein), ENAPTIN and NUANCE, are proteins that are primarily components of the nuclear envelope. The nuclear envelope is a continuous membrane system composed of two lipid bilayers: an inner and an outer nuclear membrane. Nesprins are components of both nuclear membranes and reach into the nucleoplasm and the cytoplasm, where they undergo different interactions and have the potential to influence transcriptional processes and cytoskeletal activities.

scholarly journals Role of Metalloprotease Disintegrin ADAM12 in Determination of Quiescent Reserve Cells during Myogenic Differentiation In Vitro

2003 ◽  
Vol 23 (19) ◽  
pp. 6725-6738 ◽  
Author(s):  
Yi Cao ◽  
Zhefeng Zhao ◽  
Joanna Gruszczynska-Biegala ◽  
Anna Zolkiewska
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Transmembrane Domain ◽  
Myogenic Differentiation ◽  
C2c12 Cells ◽  
Myoblast Differentiation ◽  
Differentiation Markers ◽  
Cycle Arrest

ABSTRACT Skeletal myoblasts grown in vitro and induced to differentiate either form differentiated multinucleated myotubes or give rise to quiescent, undifferentiated “reserve cells” that share several characteristics with muscle satellite cells. The mechanism of determination of reserve cells is poorly understood. We find that the expression level of the metalloprotease disintegrin ADAM12 is much higher in proliferating C2C12 myoblasts and in reserve cells than in myotubes. Inhibition of ADAM12 expression in differentiating C2C12 cultures by small interfering RNA is accompanied by lower expression levels of both quiescence markers (retinoblastoma-related protein p130 and cell cycle inhibitor p27) and differentiation markers (myogenin and integrin α7A isoform). Overexpression of ADAM12 in C2C12 cells under conditions that promote cell cycle progression leads to upregulation of p130 and p27, cell cycle arrest, and downregulation of MyoD. Thus, enhanced expression of ADAM12 induces a quiescence-like phenotype and does not stimulate differentiation. We also show that the region extending from the disintegrin to the transmembrane domain of ADAM12 and containing cell adhesion activity as well as the cytoplasmic domain of ADAM12 are required for ADAM12-mediated cell cycle arrest, while the metalloprotease domain is not essential. Our results suggest that ADAM12-mediated adhesion and/or signaling may play a role in determination of the pool of reserve cells during myoblast differentiation.

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