scholarly journals System analysis shows distinct mechanisms and common principles of nuclear envelope protein dynamics

2011 ◽  
Vol 193 (1) ◽  
pp. 109-123 ◽  
Author(s):  
Nikolaj Zuleger ◽  
David A. Kelly ◽  
A. Christine Richardson ◽  
Alastair R. W. Kerr ◽  
Martin W. Goldberg ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
System Analysis ◽  
Nuclear Pore ◽  
Binding Affinities ◽  
Inner Nuclear Membrane ◽  
Wide Range ◽  
Recovery Times

The nuclear envelope contains >100 transmembrane proteins that continuously exchange with the endoplasmic reticulum and move within the nuclear membranes. To better understand the organization and dynamics of this system, we compared the trafficking of 15 integral nuclear envelope proteins using FRAP. A surprising 30-fold range of mobilities was observed. The dynamic behavior of several of these proteins was also analyzed after depletion of ATP and/or Ran, two functions implicated in endoplasmic reticulum–inner nuclear membrane translocation. This revealed that ATP- and Ran-dependent translocation mechanisms are distinct and not used by all inner nuclear membrane proteins. The Ran-dependent mechanism requires the phenylalanine-glycine (FG)-nucleoporin Nup35, which is consistent with use of the nuclear pore complex peripheral channels. Intriguingly, the addition of FGs to membrane proteins reduces FRAP recovery times, and this also depends on Nup35. Modeling of three proteins that were unaffected by either ATP or Ran depletion indicates that the wide range in mobilities could be explained by differences in binding affinities in the inner nuclear membrane.

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 Induction of a Massive Endoplasmic Reticulum and Perinuclear Space Expansion by Expression of Lamin B Receptor Mutants and the Related Sterol Reductases TM7SF2 and DHCR7

2010 ◽  
Vol 21 (2) ◽  
pp. 354-368 ◽  
Author(s):  
Monika Zwerger ◽  
Thorsten Kolb ◽  
Karsten Richter ◽  
Iakowos Karakesisoglou ◽  
Harald Herrmann
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Cell Lines ◽  
Nuclear Membrane ◽  
Cultured Cells ◽  
Membrane Separation ◽  
Reductase Activity ◽  
Nuclear Pore ◽  
Lamin B ◽  
Lamin B Receptor

Lamin B receptor (LBR) is an inner nuclear membrane protein involved in tethering the nuclear lamina and the underlying chromatin to the nuclear envelope. In addition, LBR exhibits sterol reductase activity. Mutations in the LBR gene cause two different human diseases: Pelger-Huët anomaly and Greenberg skeletal dysplasia, a severe chrondrodystrophy causing embryonic death. Our study aimed at investigating the effect of five LBR disease mutants on human cultured cells. Three of the tested LBR mutants caused a massive compaction of chromatin coincidental with the formation of a large nucleus-associated vacuole (NAV) in several human cultured cell lines. Live cell imaging and electron microscopy revealed that this structure was generated by the separation of the inner and outer nuclear membrane. During NAV formation, nuclear pore complexes and components of the linker of nucleoskeleton and cytoskeleton complex were lost in areas of membrane separation. Concomitantly, a large number of smaller vacuoles formed throughout the cytoplasm. Notably, forced expression of the two structurally related sterol reductases transmembrane 7 superfamily member 2 and 7-dehydrocholesterol reductase caused, even in their wild-type form, a comparable phenotype in susceptible cell lines. Hence, LBR mutant variants and sterol reductases can severely interfere with the regular organization of the nuclear envelope and the endoplasmic reticulum.

scholarly journals Integral Membrane Proteins of the Nuclear Envelope Are Dispersed throughout the Endoplasmic Reticulum during Mitosis

1997 ◽  
Vol 137 (6) ◽  
pp. 1199-1210 ◽  
Author(s):  
Li Yang ◽  
Tinglu Guan ◽  
Larry Gerace
Keyword(s):  
Membrane Proteins ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Mammalian Cells ◽  
Polyclonal Antibodies ◽  
Integral Membrane Proteins ◽  
Immunogold Electron Microscopy ◽  
Nuclear Pore ◽  
Nuclear Lamins ◽  
Nuclear Membranes

We have analyzed the fate of several integral membrane proteins of the nuclear envelope during mitosis in cultured mammalian cells to determine whether nuclear membrane proteins are present in a vesicle population distinct from bulk ER membranes after mitotic nuclear envelope disassembly or are dispersed throughout the ER. Using immunofluorescence staining and confocal microscopy, we compared the localization of two inner nuclear membrane proteins (laminaassociated polypeptides 1 and 2 [LAP1 and LAP2]) and a nuclear pore membrane protein (gp210) to the distribution of bulk ER membranes, which was determined with lipid dyes (DiOC6 and R6) and polyclonal antibodies. We found that at the resolution of this technique, the three nuclear envelope markers become completely dispersed throughout ER membranes during mitosis. In agreement with these results, we detected LAP1 in most membranes containing ER markers by immunogold electron microscopy of metaphase cells. Together, these findings indicate that nuclear membranes lose their identity as a subcompartment of the ER during mitosis. We found that nuclear lamins begin to reassemble around chromosomes at the end of mitosis at the same time as LAP1 and LAP2 and propose that reassembly of the nuclear envelope at the end of mitosis involves sorting of integral membrane proteins to chromosome surfaces by binding interactions with lamins and chromatin.

Reticulon-like REEP4 at the inner nuclear membrane promotes nuclear pore complex formation

2021 ◽  
Vol 221 (2) ◽  
Author(s):  
Banafsheh Golchoubian ◽  
Andreas Brunner ◽  
Helena Bragulat-Teixidor ◽  
Annett Neuner ◽  
Busra A. Akarlar ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Pore Complexes ◽  
Late Stages ◽  
Protein Complex Assembly

Nuclear pore complexes (NPCs) are channels within the nuclear envelope that mediate nucleocytoplasmic transport. NPCs form within the closed nuclear envelope during interphase or assemble concomitantly with nuclear envelope reformation in late stages of mitosis. Both interphase and mitotic NPC biogenesis require coordination of protein complex assembly and membrane deformation. During early stages of mitotic NPC assembly, a seed for new NPCs is established on chromatin, yet the factors connecting the NPC seed to the membrane of the forming nuclear envelope are unknown. Here, we report that the reticulon homology domain protein REEP4 not only localizes to high-curvature membrane of the cytoplasmic endoplasmic reticulum but is also recruited to the inner nuclear membrane by the NPC biogenesis factor ELYS. This ELYS-recruited pool of REEP4 promotes NPC assembly and appears to be particularly important for NPC formation during mitosis. These findings suggest a role for REEP4 in coordinating nuclear envelope reformation with mitotic NPC biogenesis.

scholarly journals NUCLEAR MEMBRANES FROM MAMMALIAN LIVER

1970 ◽  
Vol 46 (2) ◽  
pp. 379-395 ◽  
Author(s):  
Werner W. Franke ◽  
Barbara Deumling ◽  
Baerbel Ermen ◽  
Ernst-Dieter Jarasch ◽  
Hans Kleinig
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Cytochrome B5 ◽  
Buoyant Density ◽  
Nuclear Pore ◽  
Nuclear Membranes ◽  
Dna And Rna ◽  
Mammalian Liver ◽  
Order Of Magnitude

Nuclear membranes were isolated from rat and pig liver by sonication of highly purified nuclear fractions and subsequent removal of adhering nucleoproteins in a high salt medium. The fractions were examined in the electron microscope by both negative staining and thin sectioning techniques and were found to consist of nuclear envelope fragments of widely varying sizes. Nuclear pore complex constituents still could frequently be recognized. The chemical composition of the nuclear membrane fractions was determined and compared with those of microsomal fractions prepared in parallel. For total nuclei as well as for nuclear membranes and microsomes, various enzyme activities were studied. The results indicate that a similarity exists between both fractions of cytomembranes, nuclear envelope, and endoplasmic reticulum, with respect to their RNA:protein ratio and their content of polar and nonpolar lipids. Both membranous fractions had many proteins in common including some membrane-bound enzymes. Activities in Mg-ATPase and the two examined cytochrome reductases were of the same order of magnitude. The content of cytochrome b5 as well as of P-450 was markedly lower in the nuclear membranes. The nuclear membranes were found to have a higher buoyant density and to be richer in protein. The glucose-6-phosphatase and Na-K-ATPase activities in the nuclear membrane fraction were very low. In the gel electrophoresis, in addition to many common protein bands, some characteristic ones for either microsomal or nuclear membranous material were detected. Significant small amounts of DNA and RNA were found to remain closely associated with the nuclear envelope fragments. Our findings indicate that nuclear and endoplasmic reticulum membranes which are known to be in morphological continuity have, besides a far-reaching similarity, some characteristic differences.

scholarly journals Inner nuclear membrane protein transport is mediated by multiple mechanisms

2008 ◽  
Vol 36 (6) ◽  
pp. 1373-1377 ◽  
Author(s):  
Nikolaj Zuleger ◽  
Nadia Korfali ◽  
Eric C. Schirmer
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Protein Transport ◽  
Protein Translocation ◽  
Lateral Diffusion ◽  
Membrane System ◽  
Nuclear Pore ◽  
Inner Nuclear Membrane ◽  
Classical Transport

Work in the nuclear transport field has led to an incredibly detailed description of protein translocation through the central channel of the nuclear pore complex, yet the mechanism by which nuclear envelope transmembrane proteins reach the inner nuclear membrane after synthesis in the endoplasmic reticulum is still hotly debated. Three different translocation models have gained experimental support: (i) simple lateral diffusion through the nuclear envelope membrane system; (ii) translocation by vesicle fusion events; and (iii) a variation on classical transport mediated by the nuclear pore complex. Although these models appear to be mutually exclusive, in the present paper we argue that they probably all function for different inner nuclear membrane proteins according to their unique characteristics.

scholarly journals Nuclear envelope proteomics: Novel integral membrane proteins of the inner nuclear membrane

2001 ◽  
Vol 98 (21) ◽  
pp. 11943-11948 ◽  
Author(s):  
M. Dreger ◽  
L. Bengtsson ◽  
T. Schoneberg ◽  
H. Otto ◽  
F. Hucho
Keyword(s):  
Membrane Proteins ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Integral Membrane Proteins ◽  
Inner Nuclear Membrane

The Nuclear Envelope and Human Disease

Physiology ◽  
2004 ◽  
Vol 19 (5) ◽  
pp. 309-314 ◽  
Author(s):  
Antoine Muchir ◽  
Howard J. Worman
Keyword(s):  
Membrane Proteins ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Intermediate Filament ◽  
Human Disease ◽  
Aging Process ◽  
Intermediate Filament Proteins ◽  
Inner Nuclear Membrane ◽  
Nuclear Lamins ◽  
Nuclear Lamin

Mutations in nuclear lamins A and C, intermediate filament proteins of the nuclear envelope, cause diseases affecting various tissues and the aging process. We review what is known about nuclear lamin function and the different diseases caused by mutations in lamins A and C and associated inner nuclear membrane proteins.

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.

Sign in / Sign up

Export Citation Format

Share Document