scholarly journals The first membrane spanning region of the lamin B receptor is sufficient for sorting to the inner nuclear membrane.

1993 ◽  
Vol 120 (3) ◽  
pp. 631-637 ◽  
Author(s):  
S Smith ◽  
G Blobel
Keyword(s):  
Nuclear Membrane ◽  
Mammalian Cells ◽  
Specific Interaction ◽  
Integral Membrane Protein ◽  
Transmembrane Segment ◽  
Hydrophobic Domain ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Amino Terminal ◽  
Lamin B Receptor

The lamin B receptor (LBR) is a polytopic integral membrane protein localized exclusively in the inner nuclear membrane domain of the nuclear envelope. Its cDNA deduced primary structure consists of a highly charged amino-terminal domain of 205 residues that faces the nucleoplasm followed by a hydrophobic domain with eight potential transmembrane segments. To identify determinants that sort LBR from its site of integration (RER and outer nuclear membrane) to the inner nuclear membrane, we prepared full-length, truncated, and chimeric cDNA constructs of chick LBR, transfected these into mammalian cells and detected the expressed protein by immunofluorescence microscopy using appropriate antibodies. Surprisingly, we found that the determinants for sorting of LBR to the inner nuclear membrane reside in a region comprising its first transmembrane sequence plus flanking residues on either side. The other transmembrane regions as well as the nucleoplasmic domain are not required for sorting. We propose that the first transmembrane segment of LBR interacts specifically with another transmembrane segment and consider several mechanisms by which such specific interaction could result in sorting to the inner nuclear membrane.

Subcellular distribution of the Xenopus p58/lamin B receptor in oocytes and eggs

1999 ◽  
Vol 112 (15) ◽  
pp. 2583-2596 ◽  
Author(s):  
A. Gajewski ◽  
G. Krohne
Keyword(s):  
Nuclear Membrane ◽  
Xenopus Oocytes ◽  
Immunofluorescence Microscopy ◽  
Significant Proportion ◽  
Sperm Chromatin ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Amino Terminal ◽  
Lamin B Receptor

The p58/lamin B receptor of vertebrates is localized in the inner nuclear membrane. Antibodies raised against the bacterially expressed amino-terminal half of Xenopus p58 (Xp58) revealed that in Xenopus oocytes the vast majority of this membrane protein is localized in cytoplasmic membranes. Only very small amounts of p58 not detectable by immunofluorescence microscopy were contained in the oocyte nuclear envelope. In contrast, nuclear membranes of 2-cell stage embryos were successfully stained with p58 antibodies, nuclei reconstituted in vitro in Xenopus egg extracts contained p58, and the nucleoplasmic domain of Xp58 could be specifically bound to sperm chromatin in vitro. One major difference between oocytes and early embryonic cells is that no chromatin is associated with the oocyte inner nuclear membrane whereas the complement of lamins is identical in both cell types. To gain insight into the properties of oocyte p58 we microinjected isolated nuclei of cultured rat cells into the cytoplasm of Xenopus oocytes. The oocyte p58 was detectable by immunofluorescence microscopy within 16–20 hours in the nuclear membrane of rat nuclei. Our data indicate that the peripheral chromatin but not lamins are required for the retention of p58 in the inner nuclear membrane. Sucrose step gradient centrifugation of total oocyte membranes revealed that the oocyte p58 was predominantly recovered in membrane fractions that did not contain lamins whereas membrane associated lamins and p58 of unfertilized eggs were found in the same fractions. By electron microscopical immunolocalizations one major population of meiotic p58 vesicles was identified that contained exclusively p58 and a second minor population (ca. 11% of p58 vesicles) contained in addition to p58 membrane bound B-type lamins. Egg vesicles containing pore membrane proteins were predominantly recovered in gradient fractions that did not contain p58 and B-type lamins. Our data indicate that the targeting of p58 to chromatin at the end of mitosis in the early Xenopus embryo is a process independent from that of lamin targeting. Comparable to the situation in oocytes and eggs, a significant proportion of p58 of interphase cells could be recovered in fractions that did not contain lamins. This population of p58 molecules could be extracted from A6-cells with buffers containing 1% Triton X-100/0.15 M NaCl and could be pelleted by a 50,000 g centrifugation. A- and B-type lamins were not detectable in the p58 containing pellet.

Lamin B receptor: role on chromatin structure, cellular senescence and possibly aging

2020 ◽  
Vol 477 (14) ◽  
pp. 2715-2720
Author(s):  
Susana Castro-Obregón
Keyword(s):  
Cellular Senescence ◽  
Nuclear Membrane ◽  
Chromatin Structure ◽  
Cholesterol Synthesis ◽  
Reductase Activity ◽  
Chimeric Protein ◽  
Nuclear Lamina ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Lamin B Receptor

The nuclear envelope is composed by an outer nuclear membrane and an inner nuclear membrane, which is underlain by the nuclear lamina that provides the nucleus with mechanical strength for maintaining structure and regulates chromatin organization for modulating gene expression and silencing. A layer of heterochromatin is beneath the nuclear lamina, attached by inner nuclear membrane integral proteins such as Lamin B receptor (LBR). LBR is a chimeric protein, having also a sterol reductase activity with which it contributes to cholesterol synthesis. Lukasova et al. showed that when DNA is damaged by ɣ-radiation in cancer cells, LBR is lost causing chromatin structure changes and promoting cellular senescence. Cellular senescence is characterized by terminal cell cycle arrest and the expression and secretion of various growth factors, cytokines, metalloproteinases, etc., collectively known as senescence-associated secretory phenotype (SASP) that cause chronic inflammation and tumor progression when they persist in the tissue. Therefore, it is fundamental to understand the molecular basis for senescence establishment, maintenance and the regulation of SASP. The work of Lukasova et al. contributed to our understanding of cellular senescence establishment and provided the basis that lead to the further discovery that chromatin changes caused by LBR reduction induce an up-regulated expression of SASP factors. LBR dysfunction has relevance in several diseases and possibly in physiological aging. The potential bifunctional role of LBR on cellular senescence establishment, namely its role in chromatin structure together with its enzymatic activity contributing to cholesterol synthesis, provide a new target to develop potential anti-aging therapies.

scholarly journals Temporal Association of Protamine 1 with the Inner Nuclear Membrane Protein Lamin B Receptor during Spermiogenesis

2003 ◽  
Vol 279 (12) ◽  
pp. 11626-11631 ◽  
Author(s):  
Ilias Mylonis ◽  
Victoria Drosou ◽  
Stefano Brancorsini ◽  
Eleni Nikolakaki ◽  
Paolo Sassone-Corsi ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Nuclear Membrane ◽  
Temporal Association ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Lamin B Receptor ◽  
Inner Nuclear Membrane Protein ◽  
Protamine 1 ◽  
Nuclear Membrane Protein

Intracellular trafficking of emerin, the Emery-Dreifuss muscular dystrophy protein

1999 ◽  
Vol 112 (11) ◽  
pp. 1709-1719 ◽  
Author(s):  
C. Ostlund ◽  
J. Ellenberg ◽  
E. Hallberg ◽  
J. Lippincott-Schwartz ◽  
H.J. Worman
Keyword(s):  
Plasma Membrane ◽  
Green Fluorescent Protein ◽  
Muscular Dystrophy ◽  
Nuclear Membrane ◽  
Fluorescent Protein ◽  
Chimeric Protein ◽  
Transmembrane Segment ◽  
Inner Nuclear Membrane ◽  
Amino Terminal ◽  
Green Fluorescent

Emerin is an integral protein of the inner nuclear membrane that is mutated or not expressed in patients with Emery-Dreifuss muscular dystrophy. Confocal immunofluorescence microscopy studies of the intracellular targeting of truncated forms of emerin, some of which are found in patients with Emery-Dreifuss muscular dystrophy, show that the nucleoplasmic, amino-terminal domain is necessary and sufficient for nuclear retention. When this domain is fused to a transmembrane segment of an integral membrane protein of the ER/plasma membrane, the chimeric protein is localized in the inner nuclear membrane. The transmembrane segment of emerin is not targeted to the inner nuclear membrane. Fluorescence photobleaching experiments of emerin fused to green fluorescent protein demonstrate that the diffusional mobility (D) of emerin is decreased in the inner nuclear membrane (D=0.10+/-0.01 microm2/second) compared to the ER membrane (D=0.32+/-0.01 microm2/second). This is in agreement with a model where integral proteins reach the inner nuclear membrane by lateral diffusion and are retained there by association with nucleoplasmic components. Some overexpressed emerin-green fluorescent protein also reaches the plasma membrane of transfected cells, where its diffusion is similar to that in the inner nuclear membrane, suggesting that emerin may also associate with non-nuclear structures.

scholarly journals Identification and characterization of autoantibodies against the nuclear envelope lamin B receptor from patients with primary biliary cirrhosis.

1990 ◽  
Vol 172 (3) ◽  
pp. 961-967 ◽  
Author(s):  
J C Courvalin ◽  
K Lassoued ◽  
H J Worman ◽  
G Blobel
Keyword(s):  
Primary Biliary Cirrhosis ◽  
Membrane Protein ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Mammalian Cells ◽  
Integral Membrane Protein ◽  
Nuclear Pore ◽  
Biliary Cirrhosis ◽  
Lamin B ◽  
Lamin B Receptor

We have identified autoantibodies from two patients with primary biliary cirrhosis (PBC) that recognize the nuclear envelope of mammalian cells on indirect immunofluorescence microscopy. These antibodies bind to a 58-kD integral membrane protein (p58) of the turkey erythrocyte nuclear envelope, which has been previously identified as a membrane receptor for lamin B (Worman, H. J., J. Yuan, G. Blobel, and S. D. Georgatos. 1988. Proc. Natl. Acad. Sci. USA. 85:8531). The antibodies also bind to a 61-kD integral membrane protein (p61) of the rat liver nuclear envelope. Affinity-purified antibodies eluted from turkey p58 bind to rat p61, showing that the two proteins share an epitope(s) and that p61 is likely the rat liver lamin B receptor. In human nuclear envelopes, the antigen recognized has an apparent molecular mass close to that of avian protein. These findings, along with the previous discovery of autoantibodies against an integral membrane glycoprotein (gp210) of the nuclear pore membrane in patients with PBC, suggest that antibodies against integral membrane proteins of the nuclear envelope are characteristic of a subset of patients with PBC.

scholarly journals The Lamin B receptor is essential for cholesterol synthesis and perturbed by disease-causing mutations

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Pei-Ling Tsai ◽  
Chenguang Zhao ◽  
Elizabeth Turner ◽  
Christian Schlieker
Keyword(s):  
Nuclear Membrane ◽  
Cholesterol Synthesis ◽  
Point Mutations ◽  
Nuclear Lamina ◽  
Human Cell Line ◽  
Loss Of Function ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Lamin B Receptor ◽  
Polytopic Membrane Protein

Lamin B receptor (LBR) is a polytopic membrane protein residing in the inner nuclear membrane in association with the nuclear lamina. We demonstrate that human LBR is essential for cholesterol synthesis. LBR mutant derivatives implicated in Greenberg skeletal dysplasia or Pelger-Huët anomaly fail to rescue the cholesterol auxotrophy of a LBR-deficient human cell line, consistent with a loss-of-function mechanism for these congenital disorders. These disease-causing variants fall into two classes: point mutations in the sterol reductase domain perturb enzymatic activity by reducing the affinity for the essential cofactor NADPH, while LBR truncations render the mutant protein metabolically unstable, leading to its rapid degradation at the inner nuclear membrane. Thus, metabolically unstable LBR variants may serve as long-sought-after model substrates enabling previously impossible investigations of poorly understood protein turnover mechanisms at the inner nuclear membrane of higher eukaryotes.

scholarly journals Stepwise reassembly of the nuclear envelope at the end of mitosis

1993 ◽  
Vol 122 (2) ◽  
pp. 295-306 ◽  
Author(s):  
N Chaudhary ◽  
JC Courvalin
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Nuclear Pore ◽  
Membrane Domains ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Domain Specific ◽  
Lamin B Receptor ◽  
Different Populations ◽  
Pore Complexes

The nuclear envelope consists of three distinct membrane domains: the outer membrane with the bound ribosomes, the inner membrane with the bound lamina, and the pore membrane with the bound pore complexes. Using biochemical and morphological methods, we observed that the nuclear membranes of HeLa cells undergoing mitosis are disassembled in a domain-specific manner, i.e., integral membrane proteins representing the inner nuclear membrane (the lamin B receptor) and the nuclear pore membrane (gp210) are segregated into different populations of mitotic vesicles. At the completion of mitosis, the inner nuclear membrane-derived vesicles associate with chromatin first, beginning in anaphase, whereas the pore membranes and the lamina assemble later, during telophase and cytokinesis. Our data suggest that the ordered reassembly of the nuclear envelope is triggered by the early attachment of inner nuclear membrane-derived vesicles to the chromatin.

Interaction between the inner nuclear membrane lamin B receptor and the heterochromatic methyl binding protein, MeCP2

2009 ◽  
Vol 315 (11) ◽  
pp. 1895-1903 ◽  
Author(s):  
Alessia Guarda ◽  
Fabrizio Bolognese ◽  
Ian Marc Bonapace ◽  
Gianfranco Badaracco
Keyword(s):  
Nuclear Membrane ◽  
Binding Protein ◽  
Lamin B ◽  
Inner Nuclear Membrane ◽  
Lamin B Receptor ◽  
Protein Mecp2
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