scholarly journals Internuclear exchange of an inner nuclear membrane protein (p55) in heterokaryons: in vivo evidence for the interaction of p55 with the nuclear lamina.

1990 ◽  
Vol 111 (6) ◽  
pp. 2225-2234 ◽  
Author(s):  
L Powell ◽  
B Burke
Keyword(s):  
Nuclear Membrane ◽  
Lateral Diffusion ◽  
Nuclear Lamina ◽  
Membrane System ◽  
Mouse Cell ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Pore Complexes

The movement between nuclei of an integral protein of the inner nuclear membrane has been studied in rat/mouse and rat/hamster heterokaryons. This protein, p55, was found to equilibrate between nuclei over a period of approximately 6 h in the absence of new protein synthesis. When rat/mouse heterokaryons were constructed using an undifferentiated murine embryonal carcinoma (P19), which lacks lamins A and C, no accumulation of p55 in the mouse cell nucleus was observed. However, P19 nuclei could be rendered competent to accumulate p55 by transfecting the parent cells with human lamin A before cell fusion, supporting the notion that p55 may interact with the nuclear lamina. Since p55 does not appear to be able to dissociate from the nuclear membrane, it is concluded that this exchange between nuclei does not occur in the aqueous phase and instead is probably membrane mediated. It is proposed that this protein may be free to move between the inner and outer nuclear membranes via the continuities at the nuclear pore complexes and that transfer between nuclei occurs via lateral diffusion through the peripheral ER, which appears to form a single continuous membrane system in these heterokaryons. One implication of these observations is that accumulation of at least some integral proteins in the inner nuclear membrane may be mediated by interactions with other nuclear components and may not require a single defined targeting sequence.

scholarly journals Efficient protein targeting to the inner nuclear membrane requires Atlastin-dependent maintenance of ER topology

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Sumit Pawar ◽  
Rosemarie Ungricht ◽  
Peter Tiefenboeck ◽  
Jean-Christophe Leroux ◽  
Ulrike Kutay
Keyword(s):  
Nuclear Membrane ◽  
Protein Targeting ◽  
Membrane System ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Vitro Assay ◽  
Inner Nuclear Membrane ◽  
General Importance

Newly synthesized membrane proteins are targeted to the inner nuclear membrane (INM) by diffusion within the membrane system of the endoplasmic reticulum (ER), translocation through nuclear pore complexes (NPCs) and retention on nuclear partners. Using a visual in vitro assay we previously showed that efficient protein targeting to the INM depends on nucleotide hydrolysis. We now reveal that INM targeting is GTP-dependent. Exploiting in vitro reconstitution and in vivo analysis of INM targeting, we establish that Atlastins, membrane-bound GTPases of the ER, sustain the efficient targeting of proteins to the INM by their continued activity in preserving ER topology. When ER topology is altered, the long-range diffusional exchange of proteins in the ER network and targeting efficiency to the INM are diminished. Highlighting the general importance of proper ER topology, we show that Atlastins also influence NPC biogenesis and timely exit of secretory cargo from the ER.

scholarly journals Diffusion and retention are major determinants of protein targeting to the inner nuclear membrane

2015 ◽  
Vol 209 (5) ◽  
pp. 687-704 ◽  
Author(s):  
Rosemarie Ungricht ◽  
Michael Klann ◽  
Peter Horvath ◽  
Ulrike Kutay
Keyword(s):  
Nuclear Membrane ◽  
Protein Targeting ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Vitro Assay ◽  
Inner Nuclear Membrane ◽  
Pore Complexes ◽  
Energy Dependent

Newly synthesized membrane proteins are constantly sorted from the endoplasmic reticulum (ER) to various membranous compartments. How proteins specifically enrich at the inner nuclear membrane (INM) is not well understood. We have established a visual in vitro assay to measure kinetics and investigate requirements of protein targeting to the INM. Using human LBR, SUN2, and LAP2β as model substrates, we show that INM targeting is energy-dependent but distinct from import of soluble cargo. Accumulation of proteins at the INM relies on both a highly interconnected ER network, which is affected by energy depletion, and an efficient immobilization step at the INM. Nucleoporin depletions suggest that translocation through nuclear pore complexes (NPCs) is rate-limiting and restricted by the central NPC scaffold. Our experimental data combined with mathematical modeling support a diffusion-retention–based mechanism of INM targeting. We experimentally confirmed the sufficiency of diffusion and retention using an artificial reporter lacking natural sorting signals that recapitulates the energy dependence of the process in vivo.

scholarly journals Synthesis, transport and incorporation into the nuclear envelope of A-type lamins and inner nuclear membrane proteins

2011 ◽  
Vol 39 (6) ◽  
pp. 1758-1763 ◽  
Author(s):  
Jose M. González ◽  
Vicente Andrés
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Complex Structure ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Perinuclear Space ◽  
Interphase Cells ◽  
Pore Complexes

The mammalian NE (nuclear envelope), which separates the nucleus from the cytoplasm, is a complex structure composed of nuclear pore complexes, the outer and inner nuclear membranes, the perinuclear space and the nuclear lamina (A- and B-type lamins). The NE is completely disassembled and reassembled at each cell division. In the present paper, we review recent advances in the understanding of the mechanisms implicated in the transport of inner nuclear membrane and nuclear lamina proteins from the endoplasmic reticulum to the nucleus in interphase cells and mitosis, with special attention to A-type lamins.

scholarly journals Nuclear envelope organization in Dictyostelium discoideum

2019 ◽  
Vol 63 (8-9-10) ◽  
pp. 509-519 ◽  
Author(s):  
Petros Batsios ◽  
Ralph Gräf ◽  
Michael P. Koonce ◽  
Denis A. Larochelle ◽  
Irene Meyer
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Major Constituent ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Linc Complex ◽  
Family Protein ◽  
Import And Export ◽  
Pore Complexes

The nuclear envelope consists of the outer and the inner nuclear membrane, the nuclear lamina and the nuclear pore complexes, which regulate nuclear import and export. The major constituent of the nuclear lamina of Dictyostelium is the lamin NE81. It can form filaments like B-type lamins and it interacts with Sun1, as well as with the LEM/HeH-family protein Src1. Sun1 and Src1 are nuclear envelope transmembrane proteins involved in the centrosome-nucleus connection and nuclear envelope stability at the nucleolar regions, respectively. In conjunction with a KASH-domain protein, Sun1 usually forms a so-called LINC complex. Two proteins with functions reminiscent of KASH-domain proteins at the outer nuclear membrane of Dictyostelium are known; interaptin which serves as an actin connector and the kinesin Kif9 which plays a role in the microtubule-centrosome connector. However, both of these lack the conserved KASH-domain. The link of the centrosome to the nuclear envelope is essential for the insertion of the centrosome into the nuclear envelope and the appropriate spindle formation. Moreover, centrosome insertion is involved in permeabilization of the mitotic nucleus, which ensures access of tubulin dimers and spindle assembly factors. Our recent progress in identifying key molecular players at the nuclear envelope of Dictyostelium promises further insights into the mechanisms of nuclear envelope dynamics.

scholarly journals ESCRT recruitment by the S. cerevisiae inner nuclear membrane protein Heh1 is regulated by Hub1-mediated alternative splicing

2020 ◽  
Vol 133 (24) ◽  
pp. jcs250688 ◽  
Author(s):  
Matías Capella ◽  
Lucía Martín Caballero ◽  
Boris Pfander ◽  
Sigurd Braun ◽  
Stefan Jentsch
Keyword(s):  
Alternative Splicing ◽  
Membrane Protein ◽  
Nuclear Membrane ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Inner Nuclear Membrane ◽  
Growth Defects ◽  
Pore Complexes ◽  
Inner Nuclear Membrane Protein ◽  
Nuclear Membrane Protein

ABSTRACTMisassembled nuclear pore complexes (NPCs) are removed by sealing off the surrounding nuclear envelope (NE), which is conducted by the endosomal sorting complexes required for transport (ESCRT) machinery. Recruitment of ESCRT proteins to the NE is mediated by the interaction between the ESCRT member Chm7 and the inner nuclear membrane protein Heh1, which belongs to the conserved LEM family. Increased ESCRT recruitment results in excessive membrane scission at damage sites but its regulation remains poorly understood. Here, we show that Hub1-mediated alternative splicing of HEH1 pre-mRNA, resulting in production of its shorter form Heh1-S, is critical for the integrity of the NE in Saccharomyces cerevisiae. ESCRT-III mutants lacking Hub1 or Heh1-S display severe growth defects and accumulate improperly assembled NPCs. This depends on the interaction of Chm7 with the conserved MSC domain, which is only present in the longer variant Heh1-L. Heh1 variants assemble into heterodimers, and we demonstrate that a unique splice segment in Heh1-S suppresses growth defects associated with the uncontrolled interaction between Heh1-L and Chm7. Together, our findings reveal that Hub1-mediated splicing generates Heh1-S to regulate ESCRT recruitment to the NE.This article has an associated First Person interview with the first author of the paper.

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 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 Synchronization of Interphase Events Depends neither on Mitosis nor on cdk1

2003 ◽  
Vol 14 (9) ◽  
pp. 3730-3740 ◽  
Author(s):  
Ayelet Laronne ◽  
Shay Rotkopf ◽  
Asaf Hellman ◽  
Yosef Gruenbaum ◽  
Andrew C.G. Porter ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Ubiquitin Ligase ◽  
Nuclear Membrane ◽  
Nuclear Lamina ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Polyploid Cells ◽  
Dividing Cells ◽  
Pore Complexes

Human HT2-19 cells with a conditional cdk1 mutation stop dividing upon cdk1 inactivation and undergo multiple rounds of endoreplication. We show herein that major cell cycle events remain synchronized in these endoreplicating cells. DNA replication alternates with gap phases and cell cycle-specific cyclin E expression is maintained. Centrosomes duplicate in synchrony with chromosome replication, giving rise to polyploid cells with multiple centrosomes. Centrosome migration, a typical prophase event, also takes place in endoreplicating cells. The timing of these events is unaffected by cdk1 inactivation compared with normally dividing cells. Nuclear lamina breakdown, in contrast, previously shown to be dependent on cdk1, does not take place in endoreplicating HT2-19 cells. Moreover, breakdown of all other major components of the nuclear lamina, like the inner nuclear membrane proteins and nuclear pore complexes, seems also to depend on cdk1. Interestingly, the APC/C ubiquitin ligase is activated in these endoreplicating cells by fzr but not by fzy. The oscillations of interphase events are thus independent of cdk1 and of mitosis but may depend on APC/Cfzr activity.

scholarly journals Energy- and temperature-dependent transport of integral proteins to the inner nuclear membrane via the nuclear pore

2004 ◽  
Vol 167 (6) ◽  
pp. 1051-1062 ◽  
Author(s):  
Tomoyuki Ohba ◽  
Eric C. Schirmer ◽  
Takeharu Nishimoto ◽  
Larry Gerace
Keyword(s):  
Nuclear Membrane ◽  
Lateral Diffusion ◽  
Nuclear Lamina ◽  
Atp Depletion ◽  
Nuclear Pore ◽  
Temperature Dependent ◽  
Inner Nuclear Membrane ◽  
Dependent Transport ◽  
Integral Proteins ◽  
Reduced Temperature

Resident integral proteins of the inner nuclear membrane (INM) are synthesized as membrane-integrated proteins on the peripheral endoplasmic reticulum (ER) and are transported to the INM throughout interphase using an unknown trafficking mechanism. To study this transport, we developed a live cell assay that measures the movement of transmembrane reporters from the ER to the INM by rapamycin-mediated trapping at the nuclear lamina. Reporter constructs with small (<30 kD) cytosolic and lumenal domains rapidly accumulated at the INM. However, increasing the size of either domain by 47 kD strongly inhibited movement. Reduced temperature and ATP depletion also inhibited movement, which is characteristic of membrane fusion mechanisms, but pharmacological inhibition of vesicular trafficking had no effect. Because reporter accumulation at the INM was inhibited by antibodies to the nuclear pore membrane protein gp210, our results support a model wherein transport of integral proteins to the INM involves lateral diffusion in the lipid bilayer around the nuclear pore membrane, coupled with active restructuring of the nuclear pore complex.

scholarly journals REEP4 is recruited to the inner nuclear membrane by ELYS and promotes nuclear pore complex formation

2020 ◽  
Author(s):  
Banafsheh Golchoubian ◽  
Andreas Brunner ◽  
Helena Bragulat-Teixidor ◽  
Busra A. Akarlar ◽  
Nurhan Ozlu ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Nucleocytoplasmic Transport ◽  
Local Deformation ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Membrane Remodeling ◽  
Inner Nuclear Membrane ◽  
Pore Complexes

AbstractNuclear pore complexes (NPCs) are channels within the nuclear envelope that mediate nucleocytoplasmic transport. NPCs assemble either into the closed nuclear envelope during interphase or concomitantly with nuclear envelope reformation during anaphase. Both, interphase and post-mitotic NPC biogenesis require local deformation of membrane. Yet, the factors that control proper membrane remodeling for post-mitotic NPC assembly are unknown. Here, we report that the reticulon homology domain-protein REEP4 localizes not only to high-curvature membrane of the cytoplasmic endoplasmic reticulum (ER) but also to the inner nuclear membrane (INM). We show that REEP4 is recruited to the INM by the NPC biogenesis factor ELYS and promotes NPC assembly. REEP4 contributes mainly to anaphase NPC assembly, suggesting that REEP4 has an unexpected role in coordinating nuclear envelope reformation with post-mitotic NPC biogenesis.

Sign in / Sign up

Export Citation Format

Share Document