1
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Le TK, Hirano Y, Asakawa H, Okamoto K, Fukagawa T, Haraguchi T, Hiraoka Y. A ubiquitin-proteasome pathway degrades the inner nuclear membrane protein Bqt4 to maintain nuclear membrane homeostasis. J Cell Sci 2023; 136:jcs260930. [PMID: 37694715 DOI: 10.1242/jcs.260930] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 08/25/2023] [Indexed: 09/12/2023] Open
Abstract
Aberrant accumulation of inner nuclear membrane (INM) proteins is associated with deformed nuclear morphology and mammalian diseases. However, the mechanisms underlying the maintenance of INM homeostasis remain poorly understood. In this study, we explored the degradation mechanisms of the INM protein Bqt4 in the fission yeast Schizosaccharomyces pombe. We have previously shown that Bqt4 interacts with the transmembrane protein Bqt3 at the INM and is degraded in the absence of Bqt3. Here, we reveal that excess Bqt4, unassociated with Bqt3, is targeted for degradation by the ubiquitin-proteasome system localized in the nucleus and Bqt3 antagonizes this process. The degradation process involves the Doa10 E3 ligase complex at the INM. Bqt4 is a tail-anchored protein and the Cdc48 complex is required for its degradation. The C-terminal transmembrane domain of Bqt4 was necessary and sufficient for proteasome-dependent protein degradation. Accumulation of Bqt4 at the INM impaired cell viability with nuclear envelope deformation, suggesting that quantity control of Bqt4 plays an important role in nuclear membrane homeostasis.
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Affiliation(s)
- Toan Khanh Le
- Nuclear Dynamics Group, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Yasuhiro Hirano
- Nuclear Dynamics Group, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
- Laboratory of Chromosome Biology, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Haruhiko Asakawa
- Nuclear Dynamics Group, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
- Laboratory of Chromosome Biology, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Koji Okamoto
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Tatsuo Fukagawa
- Laboratory of Chromosome Biology, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Tokuko Haraguchi
- Nuclear Dynamics Group, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Yasushi Hiraoka
- Nuclear Dynamics Group, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
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2
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Turk SM, Indovina CJ, Miller JM, Overton DL, Runnebohm AM, Orchard CJ, Tragesser-Tiña ME, Gosser SK, Doss EM, Richards KA, Irelan CB, Daraghmi MM, Bailey CG, Niekamp JM, Claypool KP, Engle SM, Buchanan BW, Woodruff KA, Olesen JB, Smaldino PJ, Rubenstein EM. Lipid biosynthesis perturbation impairs endoplasmic reticulum-associated degradation. J Biol Chem 2023; 299:104939. [PMID: 37331602 PMCID: PMC10372827 DOI: 10.1016/j.jbc.2023.104939] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/02/2023] [Accepted: 06/09/2023] [Indexed: 06/20/2023] Open
Abstract
The relationship between lipid homeostasis and protein homeostasis (proteostasis) is complex and remains incompletely understood. We conducted a screen for genes required for efficient degradation of Deg1-Sec62, a model aberrant translocon-associated substrate of the endoplasmic reticulum (ER) ubiquitin ligase Hrd1, in Saccharomyces cerevisiae. This screen revealed that INO4 is required for efficient Deg1-Sec62 degradation. INO4 encodes one subunit of the Ino2/Ino4 heterodimeric transcription factor, which regulates expression of genes required for lipid biosynthesis. Deg1-Sec62 degradation was also impaired by mutation of genes encoding several enzymes mediating phospholipid and sterol biosynthesis. The degradation defect in ino4Δ yeast was rescued by supplementation with metabolites whose synthesis and uptake are mediated by Ino2/Ino4 targets. Stabilization of a panel of substrates of the Hrd1 and Doa10 ER ubiquitin ligases by INO4 deletion indicates ER protein quality control is generally sensitive to perturbed lipid homeostasis. Loss of INO4 sensitized yeast to proteotoxic stress, suggesting a broad requirement for lipid homeostasis in maintaining proteostasis. A better understanding of the dynamic relationship between lipid homeostasis and proteostasis may lead to improved understanding and treatment of several human diseases associated with altered lipid biosynthesis.
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Affiliation(s)
- Samantha M Turk
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - Jacob M Miller
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | | | - Cade J Orchard
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | | | - Ellen M Doss
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Kyle A Richards
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | | | - Connor G Bailey
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Julia M Niekamp
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - Sarah M Engle
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Bryce W Buchanan
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - James B Olesen
- Department of Biology, Ball State University, Muncie, Indiana, USA
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3
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Hahn L, Carvalho P. Making and breaking the inner nuclear membrane proteome. Curr Opin Cell Biol 2022; 78:102115. [PMID: 35870351 DOI: 10.1016/j.ceb.2022.102115] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 06/12/2022] [Accepted: 06/17/2022] [Indexed: 01/31/2023]
Abstract
The nuclear envelope (NE) is the defining feature of eukaryotic cells, separating the nucleus from the cytoplasm. It has a complex architecture consisting of two lipid bilayers that, despite being continuous between them and with the endoplasmic reticulum, have different protein compositions consistent with their distinct functions. In particular, the unique composition of the inner nuclear membrane (INM), facing the nucleoplasm and its underlying nuclear lamina, is critical for the organisation and function of nuclear processes, from cell fate to gene regulation and DNA repair. Mutations in INM proteins affecting this organisation are associated with muscular dystrophies and premature ageing syndromes highlighting the role of INM architecture in cell homeostasis. Here, we discuss recent progress in understanding how specific proteins concentrate at the INM, as well as the quality control mechanisms involved in remodelling and maintaining INM protein homeostasis.
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Affiliation(s)
- Lilli Hahn
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
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4
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Mannino PJ, Lusk CP. Quality control mechanisms that protect nuclear envelope identity and function. J Biophys Biochem Cytol 2022; 221:213424. [PMID: 36036741 PMCID: PMC9442147 DOI: 10.1083/jcb.202205123] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 08/08/2022] [Accepted: 08/10/2022] [Indexed: 11/22/2022] Open
Abstract
The nuclear envelope (NE) is a specialization of the endoplasmic reticulum with distinct biochemistry that defines inner and outer membranes connected at a pore membrane that houses nuclear pore complexes (NPCs). Quality control mechanisms that maintain the physical integrity and biochemical identity of these membranes are critical to ensure that the NE acts as a selective barrier that also contributes to genome stability and metabolism. As the proteome of the NE is highly integrated, it is challenging to turn over by conventional ubiquitin-proteasome and autophagy mechanisms. Further, removal of entire sections of the NE requires elaborate membrane remodeling that is poorly understood. Nonetheless, recent work has made inroads into discovering specializations of cellular degradative machineries tailored to meeting the unique challenges imposed by the NE. In addition, cells have evolved mechanisms to surveil and repair the NE barrier to protect against the deleterious effects of a breach in NE integrity, in the form of either a ruptured NE or a dysfunctional NPC. Here, we synthesize the most recent work exploring NE quality control mechanisms across eukaryotes.
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5
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Calvanese E, Gu Y. Towards understanding inner nuclear membrane protein degradation in plants. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:2266-2274. [PMID: 35139191 DOI: 10.1093/jxb/erac037] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
The inner nuclear membrane (INM) hosts a unique set of membrane proteins that play essential roles in various aspects of the nuclear function. However, overaccumulation or malfunction of INM protein has been associated with a range of rare genetic diseases; therefore, maintaining the homeostasis and integrity of INM proteins by active removal of aberrantly accumulated proteins and replacing defective molecules through proteolysis is of critical importance. Within the last decade, it has been shown that INM proteins are degraded in yeasts by a process very similar to endoplasmic reticulum-associated degradation (ERAD), which is accomplished by retrotranslocation of membrane substrates followed by proteasome-dependent proteolysis, and this process was named inner nuclear membrane-associated degradation (INMAD). INMAD is distinguished from ERAD by specific INM-localized E3 ubiquitin ligases and proteolysis regulators. While much is yet to be determined about the INMAD pathway in yeasts, virtually no knowledge of it exists for higher eukaryotes, and only very recently have several critical regulators that participate in INM protein degradation been discovered in plants. Here, we review key molecular components of the INMAD pathway and draw parallels between the yeast and plant system to discuss promising directions in the future study of the plant INMAD process.
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Affiliation(s)
- Enrico Calvanese
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
- Innovative Genomics Institute, University of California, Berkeley, CA 94720, USA
| | - Yangnan Gu
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
- Innovative Genomics Institute, University of California, Berkeley, CA 94720, USA
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6
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Doss EM, Tragesser-Tiña ME, Huang Y, Smaldino PJ, True JD, Kalinski AL, Rubenstein EM. APC/C Cdh1p and Slx5p/Slx8p ubiquitin ligases confer resistance to aminoglycoside hygromycin B in Saccharomyces cerevisiae. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000547. [PMID: 35622489 PMCID: PMC9007615 DOI: 10.17912/micropub.biology.000547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/18/2022] [Accepted: 03/22/2022] [Indexed: 11/24/2022]
Abstract
Multiple ubiquitin ligases with nuclear substrates promote regulated protein degradation and turnover of protein quality control (PQC) substrates. We hypothesized that two ubiquitin ligases with nuclear substrates – the anaphase-promoting complex/cyclosome with the Cdh1p substrate recognition factor (APC/C Cdh1p ) and the Slx5p/Slx8p SUMO-targeted ubiquitin ligase – contribute to PQC. We predicted yeast lacking subunits of these enzymes would exhibit compromised growth in the presence of hygromycin B, which reduces translational fidelity. We observed that loss of Cdh1p, Slx5p, or Slx8p sensitizes yeast to hygromycin B to a similar extent as loss of two ubiquitin ligases with characterized roles in nuclear PQC and hygromycin B resistance. In addition to their well-characterized function in regulated protein degradation, our results are consistent with prominent roles for both APC/C Cdh1p and Slx5p/Slx8p in PQC.
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Affiliation(s)
| | | | - Yanru Huang
- Ball State University, Department of Biology
| | | | | | | | - Eric M. Rubenstein
- Ball State University, Department of Biology
,
Correspondence to: Eric M. Rubenstein (
)
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7
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Chandra S, Lusk CP. Emerging Connections between Nuclear Pore Complex Homeostasis and ALS. Int J Mol Sci 2022; 23:1329. [PMID: 35163252 PMCID: PMC8835831 DOI: 10.3390/ijms23031329] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/17/2022] [Accepted: 01/20/2022] [Indexed: 12/26/2022] Open
Abstract
Developing effective treatments for neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) requires understanding of the underlying pathomechanisms that contribute to the motor neuron loss that defines the disease. As it causes the largest fraction of familial ALS cases, considerable effort has focused on hexanucleotide repeat expansions in the C9ORF72 gene, which encode toxic repeat RNA and dipeptide repeat (DPR) proteins. Both the repeat RNA and DPRs interact with and perturb multiple elements of the nuclear transport machinery, including shuttling nuclear transport receptors, the Ran GTPase and the nucleoporin proteins (nups) that build the nuclear pore complex (NPC). Here, we consider recent work that describes changes to the molecular composition of the NPC in C9ORF72 model and patient neurons in the context of quality control mechanisms that function at the nuclear envelope (NE). For example, changes to NPC structure may be caused by the dysregulation of a conserved NE surveillance pathway mediated by the endosomal sorting complexes required for the transport protein, CHMP7. Thus, these studies are introducing NE and NPC quality control pathways as key elements in a pathological cascade that leads to C9ORF72 ALS, opening entirely new experimental avenues and possibilities for targeted therapeutic intervention.
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Affiliation(s)
| | - C. Patrick Lusk
- Department of Cell Biology, Yale School of Medicine, 295 Congress Ave, New Haven, CT 06520, USA;
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8
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Chandra S, Mannino PJ, Thaller DJ, Ader NR, King MC, Melia TJ, Lusk CP. Atg39 selectively captures inner nuclear membrane into lumenal vesicles for delivery to the autophagosome. J Cell Biol 2021; 220:e202103030. [PMID: 34714326 PMCID: PMC8575018 DOI: 10.1083/jcb.202103030] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 08/26/2021] [Accepted: 09/29/2021] [Indexed: 12/26/2022] Open
Abstract
Mechanisms that turn over components of the nucleus and inner nuclear membrane (INM) remain to be fully defined. We explore how components of the INM are selected by a cytosolic autophagy apparatus through a transmembrane nuclear envelope-localized cargo adaptor, Atg39. A split-GFP reporter showed that Atg39 localizes to the outer nuclear membrane (ONM) and thus targets the INM across the nuclear envelope lumen. Consistent with this, sequence elements that confer both nuclear envelope localization and a membrane remodeling activity are mapped to the Atg39 lumenal domain; these lumenal motifs are required for the autophagy-mediated degradation of integral INM proteins. Interestingly, correlative light and electron microscopy shows that the overexpression of Atg39 leads to the expansion of the ONM and the enclosure of a network of INM-derived vesicles in the nuclear envelope lumen. Thus, we propose an outside-in model of nucleophagy where INM is delivered into vesicles in the nuclear envelope lumen, which can be targeted by the autophagosome.
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Affiliation(s)
| | | | | | | | | | - Thomas J. Melia
- Department of Cell Biology, Yale School of Medicine, New Haven, CT
| | - C. Patrick Lusk
- Department of Cell Biology, Yale School of Medicine, New Haven, CT
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9
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Zhao S, Huang D, Peng J. Nucleolus-localized Def-CAPN3 protein degradation pathway and its role in cell cycle control and ribosome biogenesis. J Genet Genomics 2021; 48:955-960. [PMID: 34452850 DOI: 10.1016/j.jgg.2021.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 06/16/2021] [Accepted: 06/17/2021] [Indexed: 12/25/2022]
Abstract
The nucleolus, as the 'nucleus of the nucleus', is a prominent subcellular organelle in a eukaryocyte. The nucleolus serves as the centre for ribosome biogenesis, as well as an important site for cell-cycle regulation, cellular senescence, and stress response. The protein composition of the nucleolus changes dynamically through protein turnover to meet the needs of cellular activities or stress responses. Recent studies have identified a nucleolus-localized protein degradation pathway in zebrafish and humans, namely the Def-CAPN3 pathway, which is essential to ribosome production and cell-cycle progression, by controlling the turnover of multiple substrates (e.g., ribosomal small-subunit [SSU] processome component Mpp10, transcription factor p53, check-point proteins Chk1 and Wee1). This pathway relies on the Ca2+-dependent cysteine proteinase CAPN3 and is independent of the ubiquitin-mediated proteasome pathway. CAPN3 is recruited by nucleolar protein Def from cytoplasm to nucleolus, where it proteolyzes its substrates which harbor a CAPN3 recognition-motif. Def depletion leads to the exclusion of CAPN3 and accumulation of p53, Wee1, Chk1, and Mpp10 in the nucleolus that result in cell-cycle arrest and rRNA processing abnormality. Here, we summarize the discovery of the Def-CAPN3 pathway and propose its biological role in cell-cycle control and ribosome biogenesis.
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Affiliation(s)
- Shuyi Zhao
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Delai Huang
- Department of Biology, University of Virginia, Charlottesville, VA 22904, United States
| | - Jinrong Peng
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China.
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10
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Woodruff KA, Richards KA, Evans MD, Scott AR, Voas BM, Irelan CB, Olesen JB, Smaldino PJ, Rubenstein EM. Inner Nuclear Membrane Asi Ubiquitin Ligase Catalytic Subunits Asi1p and Asi3p, but not Asi2p, confer resistance to aminoglycoside hygromycin B in Saccharomyces cerevisiae. MICROPUBLICATION BIOLOGY 2021; 2021:10.17912/micropub.biology.000403. [PMID: 34095778 PMCID: PMC8170509 DOI: 10.17912/micropub.biology.000403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The heterotrimeric Asi ubiquitin ligase (encoded by ASI1, ASI2, and ASI3) mediates protein degradation in the inner nuclear membrane in Saccharomyces cerevisiae. Asi1p and Asi3p possess catalytic domains, while Asi2p functions as an adaptor for a subset of Asi substrates. We hypothesized the Asi complex is an important mediator of protein quality control, and we predicted that Asi would be required for optimal growth in conditions associated with elevated abundance of aberrant proteins. Loss of Asi1p or Asi3p, but not Asi2p, sensitized yeast to hygromycin B, which promotes translational infidelity by distorting the ribosome A site. Surprisingly, loss of quality control ubiquitin ligase Hul5p did not sensitize yeast to hygromycin B. Our results are consistent with a prominent role for an Asi subcomplex that includes Asi1p and Asi3p (but not Asi2p) in protein quality control.
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11
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Nuclear Ubiquitin-Proteasome Pathways in Proteostasis Maintenance. Biomolecules 2021; 11:biom11010054. [PMID: 33406777 PMCID: PMC7824755 DOI: 10.3390/biom11010054] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 12/28/2020] [Accepted: 12/30/2020] [Indexed: 12/19/2022] Open
Abstract
Protein homeostasis, or proteostasis, is crucial for the functioning of a cell, as proteins that are mislocalized, present in excessive amounts, or aberrant due to misfolding or other type of damage can be harmful. Proteostasis includes attaining the correct protein structure, localization, and the formation of higher order complexes, and well as the appropriate protein concentrations. Consequences of proteostasis imbalance are evident in a range of neurodegenerative diseases characterized by protein misfolding and aggregation, such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis. To protect the cell from the accumulation of aberrant proteins, a network of protein quality control (PQC) pathways identifies the substrates and direct them towards refolding or elimination via regulated protein degradation. The main pathway for degradation of misfolded proteins is the ubiquitin-proteasome system. PQC pathways have been first described in the cytoplasm and the endoplasmic reticulum, however, accumulating evidence indicates that the nucleus is an important PQC compartment for ubiquitination and proteasomal degradation of not only nuclear, but also cytoplasmic proteins. In this review, we summarize the nuclear ubiquitin-proteasome pathways involved in proteostasis maintenance in yeast, focusing on inner nuclear membrane-associated degradation (INMAD) and San1-mediated protein quality control.
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12
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Fan J, Jin H, Koch BA, Yu HG. Mps2 links Csm4 and Mps3 to form a telomere-associated LINC complex in budding yeast. Life Sci Alliance 2020; 3:3/12/e202000824. [PMID: 32967926 PMCID: PMC7536833 DOI: 10.26508/lsa.202000824] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 09/10/2020] [Accepted: 09/11/2020] [Indexed: 11/24/2022] Open
Abstract
The canonical LINC complex is composed of two different transmembrane proteins; this work reveals the heterotrimeric composition of the telomere-associated LINC complex in budding yeast. The linker of the nucleoskeleton and cytoskeleton (LINC) complex is composed of two transmembrane proteins: the KASH domain protein localized to the outer nuclear membrane and the SUN domain protein to the inner nuclear membrane. In budding yeast, the sole SUN domain protein, Mps3, is thought to pair with either Csm4 or Mps2, two KASH-like proteins, to form two separate LINC complexes. Here, we show that Mps2 mediates the interaction between Csm4 and Mps3 to form a heterotrimeric telomere-associated LINC (t-LINC) complex in budding yeast meiosis. Mps2 binds to Csm4 and Mps3, and all three are localized to the telomere. Telomeric localization of Csm4 depends on both Mps2 and Mps3; in contrast, Mps2’s localization depends on Mps3 but not Csm4. Mps2-mediated t-LINC complex regulates telomere movement and meiotic recombination. By ectopically expressing CSM4 in vegetative yeast cells, we reconstitute the heterotrimeric t-LINC complex and demonstrate its ability to tether telomeres. Our findings therefore reveal the heterotrimeric composition of the t-LINC complex in budding yeast and have implications for understanding variant LINC complex formation.
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Affiliation(s)
- Jinbo Fan
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Hui Jin
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Bailey A Koch
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Hong-Guo Yu
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
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13
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Almendáriz-Palacios C, Gillespie ZE, Janzen M, Martinez V, Bridger JM, Harkness TAA, Mousseau DD, Eskiw CH. The Nuclear Lamina: Protein Accumulation and Disease. Biomedicines 2020; 8:E188. [PMID: 32630170 PMCID: PMC7400325 DOI: 10.3390/biomedicines8070188] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/23/2020] [Accepted: 06/26/2020] [Indexed: 02/06/2023] Open
Abstract
Cellular health is reliant on proteostasis-the maintenance of protein levels regulated through multiple pathways modulating protein synthesis, degradation and clearance. Loss of proteostasis results in serious disease and is associated with aging. One proteinaceous structure underlying the nuclear envelope-the nuclear lamina-coordinates essential processes including DNA repair, genome organization and epigenetic and transcriptional regulation. Loss of proteostasis within the nuclear lamina results in the accumulation of proteins, disrupting these essential functions, either via direct interactions of protein aggregates within the lamina or by altering systems that maintain lamina structure. Here we discuss the links between proteostasis and disease of the nuclear lamina, as well as how manipulating specific proteostatic pathways involved in protein clearance could improve cellular health and prevent/reverse disease.
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Affiliation(s)
- Carla Almendáriz-Palacios
- Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (C.A.-P.); (V.M.)
| | - Zoe E. Gillespie
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (Z.E.G.); (M.J.); (T.A.A.H.)
| | - Matthew Janzen
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (Z.E.G.); (M.J.); (T.A.A.H.)
| | - Valeria Martinez
- Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (C.A.-P.); (V.M.)
| | - Joanna M. Bridger
- Centre for Genome Engineering and Maintenance, College of Health, Life and Medical Sciences, Brunel University London, Kingston Lane, Uxbridge UB8 3PH, UK;
| | - Troy A. A. Harkness
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (Z.E.G.); (M.J.); (T.A.A.H.)
| | - Darrell D. Mousseau
- Cell Signalling Laboratory, Department of Psychiatry, University of Saskatchewan, Saskatoon, SK S7N 5A5, Canada;
| | - Christopher H. Eskiw
- Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (C.A.-P.); (V.M.)
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; (Z.E.G.); (M.J.); (T.A.A.H.)
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14
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Huang A, Tang Y, Shi X, Jia M, Zhu J, Yan X, Chen H, Gu Y. Proximity labeling proteomics reveals critical regulators for inner nuclear membrane protein degradation in plants. Nat Commun 2020; 11:3284. [PMID: 32601292 PMCID: PMC7324386 DOI: 10.1038/s41467-020-16744-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 05/20/2020] [Indexed: 11/08/2022] Open
Abstract
The inner nuclear membrane (INM) selectively accumulates proteins that are essential for nuclear functions; however, overaccumulation of INM proteins results in a range of rare genetic disorders. So far, little is known about how defective, mislocalized, or abnormally accumulated membrane proteins are actively removed from the INM, especially in plants and animals. Here, via analysis of a proximity-labeling proteomic profile of INM-associated proteins in Arabidopsis, we identify critical components for an INM protein degradation pathway. We show that this pathway relies on the CDC48 complex for INM protein extraction and 26S proteasome for subsequent protein degradation. Moreover, we show that CDC48 at the INM may be regulated by a subgroup of PUX proteins, which determine the substrate specificity or affect the ATPase activity of CDC48. These PUX proteins specifically associate with the nucleoskeleton underneath the INM and physically interact with CDC48 proteins to negatively regulate INM protein degradation in plants.
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Affiliation(s)
- Aobo Huang
- Tsinghua-Peking Joint Center for Life Sciences, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yu Tang
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Xuetao Shi
- Tsinghua-Peking Joint Center for Life Sciences, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Min Jia
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
| | - Jinheng Zhu
- Tsinghua-Peking Joint Center for Life Sciences, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Xiaohan Yan
- Tsinghua-Peking Joint Center for Life Sciences, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Huiqin Chen
- Tsinghua-Peking Joint Center for Life Sciences, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yangnan Gu
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA.
- Innovative Genomics Institute, University of California, Berkeley, CA, USA.
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15
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Croft T, Venkatakrishnan P, James Theoga Raj C, Groth B, Cater T, Salemi MR, Phinney B, Lin SJ. N-terminal protein acetylation by NatB modulates the levels of Nmnats, the NAD + biosynthetic enzymes in Saccharomyces cerevisiae. J Biol Chem 2020; 295:7362-7375. [PMID: 32299909 PMCID: PMC7247314 DOI: 10.1074/jbc.ra119.011667] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 04/14/2020] [Indexed: 12/13/2022] Open
Abstract
NAD+ is an essential metabolite participating in cellular biochemical processes and signaling. The regulation and interconnection among multiple NAD+ biosynthesis pathways are incompletely understood. Yeast (Saccharomyces cerevisiae) cells lacking the N-terminal (Nt) protein acetyltransferase complex NatB exhibit an approximate 50% reduction in NAD+ levels and aberrant metabolism of NAD+ precursors, changes that are associated with a decrease in nicotinamide mononucleotide adenylyltransferase (Nmnat) protein levels. Here, we show that this decrease in NAD+ and Nmnat protein levels is specifically due to the absence of Nt-acetylation of Nmnat (Nma1 and Nma2) proteins and not of other NatB substrates. Nt-acetylation critically regulates protein degradation by the N-end rule pathways, suggesting that the absence of Nt-acetylation may alter Nmnat protein stability. Interestingly, the rate of protein turnover (t½) of non-Nt-acetylated Nmnats did not significantly differ from those of Nt-acetylated Nmnats. Accordingly, deletion or depletion of the N-end rule pathway ubiquitin E3 ligases in NatB mutants did not restore NAD+ levels. Next, we examined whether the status of Nt-acetylation would affect the translation of Nmnats, finding that the absence of Nt-acetylation does not significantly alter the polysome formation rate on Nmnat mRNAs. However, we observed that NatB mutants have significantly reduced Nmnat protein maturation. Our findings indicate that the reduced Nmnat levels in NatB mutants are mainly due to inefficient protein maturation. Nmnat activities are essential for all NAD+ biosynthesis routes, and understanding the regulation of Nmnat protein homeostasis may improve our understanding of the molecular basis and regulation of NAD+ metabolism.
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Affiliation(s)
- Trevor Croft
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, California 95616
| | - Padmaja Venkatakrishnan
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, California 95616
| | - Christol James Theoga Raj
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, California 95616
| | - Benjamin Groth
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, California 95616
| | - Timothy Cater
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, California 95616
| | - Michelle R Salemi
- Proteomic Core Facility, University of California, Davis, California 95616
| | - Brett Phinney
- Proteomic Core Facility, University of California, Davis, California 95616
| | - Su-Ju Lin
- Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, California 95616.
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16
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Abstract
The nucleus is enclosed by a double-membrane structure, the nuclear envelope, which separates the nucleoplasm from the cytoplasm. The outer nuclear membrane is continuous with the endoplasmic reticulum (ER), whereas the inner nuclear membrane (INM) is a specialized compartment with a unique proteome. In order to ensure compartmental homeostasis, INM-associated degradation (INMAD) is required for both protein quality control and regulated proteolysis of INM proteins. INMAD shares similarities with ER-associated degradation (ERAD). The mechanism of ERAD is well characterized, whereas the INMAD pathway requires further definition. Here we review the three different branches of INMAD, mediated by their respective E3 ubiquitin ligases: Doa10, Asi1-3, and APC/C. We clarify the distinction between ERAD and INMAD, their substrate recognition signals, and the subsequent processing by their respective degradation machineries. We also discuss the significance of cell-cycle and developmental regulation of protein clearance at the INM, and its relationship to human disease.
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Affiliation(s)
- Bailey Koch
- a Department of Biological Science, The Florida State University , Tallahassee , FL , USA
| | - Hong-Guo Yu
- a Department of Biological Science, The Florida State University , Tallahassee , FL , USA
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17
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Sosa Ponce ML, Moradi-Fard S, Zaremberg V, Cobb JA. SUNny Ways: The Role of the SUN-Domain Protein Mps3 Bridging Yeast Nuclear Organization and Lipid Homeostasis. Front Genet 2020; 11:136. [PMID: 32184804 PMCID: PMC7058695 DOI: 10.3389/fgene.2020.00136] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 02/04/2020] [Indexed: 12/14/2022] Open
Abstract
Mps3 is a SUN (Sad1-UNC-84) domain-containing protein that is located in the inner nuclear membrane (INM). Genetic screens with multiple Mps3 mutants have suggested that distinct regions of Mps3 function in relative isolation and underscore the broad involvement of Mps3 in multiple pathways including mitotic spindle formation, telomere maintenance, and lipid metabolism. These pathways have largely been characterized in isolation, without a holistic consideration for how key regulatory events within one pathway might impinge on other aspects of biology at the nuclear membrane. Mps3 is uniquely positioned to function in these multiple pathways as its N- terminus is in the nucleoplasm, where it is important for telomere anchoring at the nuclear periphery, and its C-terminus is in the lumen, where it has links with lipid metabolic processes. Emerging work suggests that the role of Mps3 in nuclear organization and lipid homeostasis are not independent, but more connected. For example, a failure in regulating Mps3 levels through the cell cycle leads to nuclear morphological abnormalities and loss of viability, suggesting a link between the N-terminal domain of Mps3 and nuclear envelope homeostasis. We will highlight work suggesting that Mps3 is pivotal factor in communicating events between the nucleus and the lipid bilayer.
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Affiliation(s)
- Maria Laura Sosa Ponce
- Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Cumming School of Medicine, Calgary, AB, Canada.,Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Sarah Moradi-Fard
- Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Cumming School of Medicine, Calgary, AB, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Jennifer A Cobb
- Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Cumming School of Medicine, Calgary, AB, Canada
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18
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Buchanan BW, Mehrtash AB, Broshar CL, Runnebohm AM, Snow BJ, Scanameo LN, Hochstrasser M, Rubenstein EM. Endoplasmic reticulum stress differentially inhibits endoplasmic reticulum and inner nuclear membrane protein quality control degradation pathways. J Biol Chem 2019; 294:19814-19830. [PMID: 31723032 DOI: 10.1074/jbc.ra119.010295] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 11/04/2019] [Indexed: 12/29/2022] Open
Abstract
Endoplasmic reticulum (ER) stress occurs when the abundance of unfolded proteins in the ER exceeds the capacity of the folding machinery. Despite the expanding cadre of characterized cellular adaptations to ER stress, knowledge of the effects of ER stress on cellular physiology remains incomplete. We investigated the impact of ER stress on ER and inner nuclear membrane protein quality control mechanisms in Saccharomyces cerevisiae. We analyzed the turnover of substrates of four ubiquitin ligases (Doa10, Rkr1/Ltn1, Hrd1, and the Asi complex) and the metalloprotease Ste24 in induced models of ER stress. ER stress did not substantially impact Doa10 or Rkr1 substrates. However, Hrd1-mediated destruction of a protein that aberrantly engages the translocon (Deg1-Sec62) and substrates with luminal degradation signals was markedly impaired by ER stress; by contrast, Hrd1-dependent degradation of proteins with intramembrane degrons was largely unperturbed by ER stress. ER stress impaired the degradation of one of two Asi substrates analyzed and caused a translocon-clogging Ste24 substrate to accumulate in a form consistent with persistent translocon occupation. Degradation of Deg1-Sec62 in the absence of stress and stabilization during ER stress were independent of four ER stress-sensing pathways. Our results indicate ER stress differentially impacts degradation of protein quality control substrates, including those mediated by the same ubiquitin ligase. These observations suggest the existence of additional regulatory mechanisms dictating substrate selection during ER stress.
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Affiliation(s)
- Bryce W Buchanan
- Department of Biology, Ball State University, Muncie, Indiana 47306
| | - Adrian B Mehrtash
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | | | | | - Brian J Snow
- Department of Biology, Ball State University, Muncie, Indiana 47306
| | - Laura N Scanameo
- Department of Biology, Ball State University, Muncie, Indiana 47306
| | - Mark Hochstrasser
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
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19
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Natarajan N, Foresti O, Wendrich K, Stein A, Carvalho P. Quality Control of Protein Complex Assembly by a Transmembrane Recognition Factor. Mol Cell 2019; 77:108-119.e9. [PMID: 31679820 PMCID: PMC6941229 DOI: 10.1016/j.molcel.2019.10.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 08/27/2019] [Accepted: 10/01/2019] [Indexed: 01/08/2023]
Abstract
The inner nuclear membrane (INM) is continuous with the endoplasmic reticulum (ER) but harbors a distinctive proteome essential for nuclear functions. In yeast, the Asi1/Asi2/Asi3 ubiquitin ligase complex safeguards the INM proteome through the clearance of mislocalized ER membrane proteins. How the Asi complex selectively targets mislocalized proteins and coordinates its activity with other ER functions, such as protein biogenesis, is unclear. Here, we uncover a link between INM proteome identity and membrane protein complex assembly in the remaining ER. We show that lone proteins and complex subunits failing to assemble in the ER access the INM for Asi-mediated degradation. Substrates are recognized by direct binding of Asi2 to their transmembrane domains for subsequent ubiquitination by Asi1/Asi3 and membrane extraction. Our data suggest a model in which spatial segregation of membrane protein complex assembly and quality control improves assembly efficiency and reduces the levels of orphan subunits. Quality control of unassembled subunits of membrane complexes is restricted to the INM The Asi complex promotes degradation of folded but unassembled membrane proteins Binding of Asi2 to membrane domain of unassembled subunits mediates their recognition INM quality control maintains complex subunits within near-stoichiometric levels
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Affiliation(s)
- Nivedita Natarajan
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Ombretta Foresti
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader, 88, 08003 Barcelona, Spain
| | - Kim Wendrich
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Alexander Stein
- Research Group Membrane Protein Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
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20
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Patrolling the nucleus: inner nuclear membrane-associated degradation. Curr Genet 2019; 65:1099-1106. [PMID: 31020383 PMCID: PMC6744382 DOI: 10.1007/s00294-019-00971-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Revised: 04/09/2019] [Accepted: 04/10/2019] [Indexed: 12/13/2022]
Abstract
Protein quality control and transport are important for the integrity of organelles such as the endoplasmic reticulum, but it is largely unknown how protein homeostasis is regulated at the nuclear envelope (NE) despite the connection between NE protein function and human disease. Elucidating mechanisms that regulate the NE proteome is key to understanding nuclear processes such as gene expression, DNA replication and repair as NE components, particularly proteins at the inner nuclear membrane (INM), are involved in the maintenance of nuclear structure, nuclear positioning and chromosome organization. Nuclear pore complexes control the entry and exit of proteins in and out of the nucleus, restricting movement across the nuclear membrane based on protein size, or the size of the extraluminal-facing domain of a transmembrane protein, providing one level of INM proteome regulation. Research in budding yeast has identified a protein quality control system that targets mislocalized and misfolded proteins at the INM. Here, we review what is known about INM-associated degradation, including recent evidence suggesting that it not only targets mislocalized or misfolded proteins, but also contributes to homeostasis of resident INM proteins.
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