scholarly journals Direct binding of ESCRT protein Chm7 to phosphatidic acid–rich membranes at nuclear envelope herniations

2021 ◽  
Vol 220 (3) ◽  
Author(s):  
David J. Thaller ◽  
Danqing Tong ◽  
Christopher J. Marklew ◽  
Nicholas R. Ader ◽  
Philip J. Mannino ◽  
...  
Keyword(s):  
Amino Acids ◽  
Phosphatidic Acid ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Binding Capacity ◽  
Nuclear Pore ◽  
Membrane Remodeling ◽  
Functional Importance ◽  
Direct Binding ◽  
Domain Protein

Mechanisms that control nuclear membrane remodeling are essential to maintain the integrity of the nucleus but remain to be fully defined. Here, we identify a phosphatidic acid (PA)–binding capacity in the nuclear envelope (NE)–specific ESCRT, Chm7, in budding yeast. Chm7’s interaction with PA-rich membranes is mediated through a conserved hydrophobic stretch of amino acids, which confers recruitment to the NE in a manner that is independent of but required for Chm7’s interaction with the LAP2-emerin-MAN1 (LEM) domain protein Heh1 (LEM2). Consistent with the functional importance of PA binding, mutation of this region abrogates recruitment of Chm7 to membranes and abolishes Chm7 function in the context of NE herniations that form during defective nuclear pore complex (NPC) biogenesis. In fact, we show that a PA sensor specifically accumulates within these NE herniations. We suggest that local control of PA metabolism is important for ensuring productive NE remodeling and that its dysregulation may contribute to pathologies associated with defective NPC assembly.

scholarly journals Direct PA-binding by Chm7 is required for nuclear envelope surveillance at herniations

2020 ◽  
Author(s):  
David J. Thaller ◽  
Danqing Tong ◽  
Christopher J. Marklew ◽  
Sapan Borah ◽  
Barbara Ciani ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Specific Binding ◽  
Binding Activity ◽  
Nuclear Pore ◽  
Membrane Remodeling ◽  
Functional Importance ◽  
Domain Protein

AbstractMechanisms that control nuclear membrane remodeling are essential to maintain the integrity of the nucleus but remain to be fully defined. Here, we identify a phosphatidic acid (PA)-binding activity in the nuclear envelope-specific ESCRT, Chm7, in budding yeast. PA-binding is mediated through a conserved hydrophobic stretch of amino acids, which confers specific binding to the inner nuclear membrane (INM). This INM-binding is independent but nonetheless required for interaction with the LAP2-emerin-MAN1 (LEM) domain protein, Heh1 (LEM2). Consistent with the functional importance of PA-binding, mutation of this region inhibits recruitment of Chm7 to the INM and abolishes Chm7 function in the context of nuclear envelope herniations or “blebs” that form during defective nuclear pore complex (NPC) biogenesis. In fact, we show that PA accumulates at nuclear envelope herniations. We suggest that local control of PA metabolism is important for ensuring productive nuclear envelope remodeling and that its dysregulation may contribute to pathologies associated with defective NPC assembly.

scholarly journals A short perinuclear amphipathic α-helix in Apq12 promotes nuclear pore complex biogenesis

2021 ◽  
Author(s):  
Elmar Schiebel ◽  
Wanlu Zhang ◽  
Azqa Khan ◽  
Jlenia Vitale ◽  
Annett Neuner ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Phosphatidic Acid ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Integral Membrane Protein ◽  
Nuclear Pore ◽  
Binding Properties ◽  
Perinuclear Space ◽  
Α Helix

The integral membrane protein Apq12 is an important nuclear envelope (NE)/ER modulator that cooperates with the nuclear pore complex (NPC) biogenesis factors Brl1 and Brr6. How Apq12 executes these functions is unknown. Here we identified a short amphipathic α-helix (AαH) in Apq12 that links the two transmembrane domains in the perinuclear space and has liposome-binding properties. Cells expressing an APQ12 (apq12-ah) version in which AαH is disrupted show NPC biogenesis and NE integrity defects, without impacting upon Apq12-ah topology or NE/ER localization. Overexpression of APQ12 but not apq12-ah triggers striking over-proliferation of the outer nuclear membrane (ONM)/ER and promotes accumulation of phosphatidic acid (PA) at the NE. Apq12 and Apq12-ah both associate with NPC biogenesis intermediates and removal of AαH increases both Brl1 levels and the interaction between Brl1 and Brr6. We conclude that the short amphipathic α-helix of Apq12 regulates the function of Brl1 and Brr6 and promotes PA accumulation at the NE during NPC biogenesis.

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.

scholarly journals Chm7 and Heh1 form a nuclear envelope subdomain for nuclear pore complex quality control

2016 ◽  
Author(s):  
Brant M. Webster ◽  
David J. Thaller ◽  
Jens Jäeger ◽  
Sarah E. Ochmann ◽  
C. Patrick Lusk
Keyword(s):  
Quality Control ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Membrane Remodeling ◽  
Local Regulation ◽  
Aaa Atpase ◽  
Pore Complexes ◽  
Nuclear Compartmentalization

AbstractMechanisms that ensure the integrity of the nuclear envelope rely on membrane remodeling proteins like the ESCRTs and the AAA ATPase Vps4, which help seal the nuclear envelope at the end of mitosis and prevent the formation of defective nuclear pore complexes (NPCs). Here, we show that the integral inner nuclear membrane proteins Heh1 and Heh2 directly bind the ESCRT-III, Snf7, and the ESCRT-II/III chimera, Chm7, in their ‘open’ forms. Moreover, Heh1 is required for Chm7-recruitment to the nuclear envelope. As Chm7 accumulates on the nuclear envelope upon blocks to NPC assembly, but not to nuclear transport, interactions between ESCRTs and the Heh proteins might form a biochemically distinct nuclear envelope subdomain that delimits regions of assembling NPCs. Interestingly, deletion of CHM7 suppresses the formation of the storage of improperly assembled NPC compartment prevalent in vps4Δ strains. Thus, our data support that the Heh1-dependent recruitment of Chm7 is a key component of a quality control pathway whose local regulation by Vps4 and the transmembrane nup, Pom152, prevents loss of nuclear compartmentalization by defective NPCs.

scholarly journals Nup98 Localizes to Both Nuclear and Cytoplasmic Sides of the Nuclear Pore and Binds to Two Distinct Nucleoporin Subcomplexes

2003 ◽  
Vol 14 (2) ◽  
pp. 600-610 ◽  
Author(s):  
Eric R. Griffis ◽  
Songli Xu ◽  
Maureen A. Powers
Keyword(s):  
Amino Acids ◽  
Nuclear Envelope ◽  
Point Mutation ◽  
Cleavage Site ◽  
Nuclear Pore ◽  
Nucleocytoplasmic Shuttling ◽  
Double Membrane ◽  
C Terminus ◽  
Direct Binding ◽  
Autoproteolytic Cleavage

The vertebrate nuclear pore is an enormous structure that spans the double membrane of the nuclear envelope. In yeast, most nucleoporins are found symmetrically on both the nuclear and cytoplasmic sides of the structure. However, in vertebrates most nucleoporins have been localized exclusively to one side of the nuclear pore. Herein, we show, by immunofluorescence and immunoelectron microscopy, that Nup98 is found on both sides of the pore complex. Additionally, we find that the pore-targeting domain of Nup98 interacts directly with the cytoplasmic nucleoporin Nup88, a component of the Nup214, Nup88, Nup62 subcomplex. Nup98 was previously described to interact with the nuclear-oriented Nup160, 133, 107, 96 complex through direct binding to Nup96. Interestingly, the same site within Nup98 is involved in binding to both Nup88 and Nup96. Autoproteolytic cleavage of the Nup98 C terminus is required for both of these binding interactions. When cleavage is blocked by a point mutation, a minimal eight amino acids downstream of the cleavage site is sufficient to prevent most binding to either Nup96 or Nup88. Thus, Nup98 interacts with both faces of the nuclear pore, a localization in keeping with its previously described nucleocytoplasmic shuttling activity.

scholarly journals Regulation and coordination of nuclear envelope and nuclear pore complex assembly

Nucleus ◽  
2013 ◽  
Vol 4 (2) ◽  
pp. 105-114 ◽  
Author(s):  
Michaela Clever ◽  
Yasuhiro Mimura ◽  
Tomoko Funakoshi ◽  
Naoko Imamoto
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Nuclear Pore ◽  
Complex Assembly

scholarly journals The Three Fungal Transmembrane Nuclear Pore Complex Proteins of Aspergillus nidulans Are Dispensable in the Presence of an Intact An-Nup84-120 Complex

2009 ◽  
Vol 20 (2) ◽  
pp. 616-630 ◽  
Author(s):  
Hui-Lin Liu ◽  
Colin P.C. De Souza ◽  
Aysha H. Osmani ◽  
Stephen A. Osmani
Keyword(s):  
High Temperature ◽  
Nuclear Envelope ◽  
Aspergillus Nidulans ◽  
Nuclear Pore Complex ◽  
Mitotic Spindle ◽  
Spindle Pole ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Spindle Pole Bodies ◽  
Pore Complexes

In Aspergillus nidulans nuclear pore complexes (NPCs) undergo partial mitotic disassembly such that 12 NPC proteins (Nups) form a core structure anchored across the nuclear envelope (NE). To investigate how the NPC core is maintained, we affinity purified the major core An-Nup84-120 complex and identified two new fungal Nups, An-Nup37 and An-ELYS, previously thought to be vertebrate specific. During mitosis the An-Nup84-120 complex locates to the NE and spindle pole bodies but, unlike vertebrate cells, does not concentrate at kinetochores. We find that mutants lacking individual An-Nup84-120 components are sensitive to the membrane destabilizer benzyl alcohol (BA) and high temperature. Although such mutants display no defects in mitotic spindle formation, they undergo mitotic specific disassembly of the NPC core and transient aggregation of the mitotic NE, suggesting the An-Nup84-120 complex might function with membrane. Supporting this, we show cells devoid of all known fungal transmembrane Nups (An-Ndc1, An-Pom152, and An-Pom34) are viable but that An-ndc1 deletion combined with deletion of individual An-Nup84-120 components is either lethal or causes sensitivity to treatments expected to destabilize membrane. Therefore, the An-Nup84-120 complex performs roles, perhaps at the NPC membrane as proposed previously, that become essential without the An-Ndc1 transmembrane Nup.

scholarly journals The single transmembrane segment of gp210 is sufficient for sorting to the pore membrane domain of the nuclear envelope.

1992 ◽  
Vol 119 (6) ◽  
pp. 1441-1449 ◽  
Author(s):  
R W Wozniak ◽  
G Blobel
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Immunofluorescence Microscopy ◽  
Nuclear Pore ◽  
Transmembrane Helices ◽  
Wild Type ◽  
Transmembrane Segment ◽  
Membrane Domain ◽  
3T3 Cells ◽  
Type Mutant

The glycoprotein gp210 is located in the "pore membrane," a specialized domain of the nuclear envelope to which the nuclear pore complex (NPC) is anchored. gp210 contains a large cisternal domain, a single transmembrane segment (TM), and a COOH-terminal, 58-amino acid residue cytoplasmic tail (CT) (Wozniak, R. W., E. Bartnik, and G. Blobel. 1989. J. Cell Biol. 108:2083-2092; Greber, U. F., A. Senior, and L. Gerace. 1990. EMBO (Eur. Mol. Biol. Organ.) J. 9:1495-1502). To locate determinants for sorting of gp210 to the pore membrane, we constructed various cDNAs coding for wild-type, mutant, and chimeric gp210, and monitored localization of the expressed protein in 3T3 cells by immunofluorescence microscopy using appropriate antibodies. The large cisternal domain of gp210 (95% of its mass) did not reveal any sorting determinants. Surprisingly, the TM of gp210 is sufficient for sorting to the pore membrane. The CT also contains a sorting determinant, but it is weaker than that of the TM. We propose specific lateral association of the transmembrane helices of two proteins to yield either a gp210 homodimer or a heterodimer of gp210 and another protein. The cytoplasmically oriented tails of these dimers may bind cooperatively to the adjacent NPCs. In addition, we demonstrate that gp210 co-localizes with cytoplasmically dispersed nucleoporins, suggesting a cytoplasmic association of these components.

scholarly journals The Torsin/ NEP1R1-CTDNEP1/ Lipin axis regulates nuclear envelope lipid metabolism for nuclear pore complex insertion

2020 ◽  
Author(s):  
Julie Jacquemyn ◽  
Joyce Foroozandeh ◽  
Katlijn Vints ◽  
Jef Swerts ◽  
Patrik Verstreken ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Lipid Droplets ◽  
Nuclear Pore ◽  
List Type ◽  
Unknown Mechanism ◽  
Structure Lipid ◽  
Cellular Events ◽  
Upstream Regulator

AbstractTorsin ATPases of the endoplasmic reticulum (ER) and nuclear envelope (NE) lumen inhibit Lipin-mediated phosphatidate (PA) to diacylglycerol (DAG) conversion by an unknown mechanism. This excess PA metabolism is implicated in TOR1A/TorsinA diseases, but it is unclear whether it explains why Torsin concomitantly affects nuclear structure, lipid droplets (LD), organelle and cell growth. Here a fly miniscreen identified that Torsins affect these events via the NEP1R1-CTDNEP1 phosphatase complex. Further, Torsin homo-oligomerization rather than ATPase activity was key to function. NEP1R1-CTDNEP1 activates Lipin by dephosphorylation. We show that Torsin prevents CTDNEP1 from accumulating in the NE and excludes Lipin from the nucleus. Moreover, this repression of nuclear PA metabolism is required for interphase nuclear pore biogenesis. We conclude that Torsin is an upstream regulator of the NEP1R1-CTDNEP1/ Lipin pathway. This connects the ER/NE lumen with PA metabolism, and affects numerous cellular events including it has a previously unrecognized role in nuclear pore biogenesis.HighlightsNuclear envelope PA-DAG-TAG synthesis is independently regulated by Torsin and Torip/LAP1Torsin removes CTDNEP1 from the nuclear envelope and excludes Lipin from the nucleusExcess nuclear envelope NEP1R1-CTDNEP1/ Lipin activity impairs multiple aspects of NPC biogenesisNEP1R1-CTDNEP1/ Lipin inhibition prevents cellular defects associated with TOR1A and TOR1AIP1 / LAP1 disease

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