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Deolal P, Scholz J, Ren K, Bragulat-Teixidor H, Otsuka S. Sculpting nuclear envelope identity from the endoplasmic reticulum during the cell cycle. Nucleus 2024; 15:2299632. [PMID: 38238284 PMCID: PMC10802211 DOI: 10.1080/19491034.2023.2299632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 12/21/2023] [Indexed: 01/23/2024] Open
Abstract
The nuclear envelope (NE) regulates nuclear functions, including transcription, nucleocytoplasmic transport, and protein quality control. While the outer membrane of the NE is directly continuous with the endoplasmic reticulum (ER), the NE has an overall distinct protein composition from the ER, which is crucial for its functions. During open mitosis in higher eukaryotes, the NE disassembles during mitotic entry and then reforms as a functional territory at the end of mitosis to reestablish nucleocytoplasmic compartmentalization. In this review, we examine the known mechanisms by which the functional NE reconstitutes from the mitotic ER in the continuous ER-NE endomembrane system during open mitosis. Furthermore, based on recent findings indicating that the NE possesses unique lipid metabolism and quality control mechanisms distinct from those of the ER, we explore the maintenance of NE identity and homeostasis during interphase. We also highlight the potential significance of membrane junctions between the ER and NE.
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Affiliation(s)
- Pallavi Deolal
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
- Medical University of Vienna, Center for Medical Biochemistry, Department of Molecular Biology, Vienna, Austria
| | - Julia Scholz
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
- Medical University of Vienna, Center for Medical Biochemistry, Department of Molecular Biology, Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Kaike Ren
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
- Medical University of Vienna, Center for Medical Biochemistry, Department of Molecular Biology, Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Helena Bragulat-Teixidor
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
- Medical University of Vienna, Center for Medical Biochemistry, Department of Molecular Biology, Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Shotaro Otsuka
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
- Medical University of Vienna, Center for Medical Biochemistry, Department of Molecular Biology, Vienna, Austria
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2
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Scott ZC, Steen SB, Huber G, Westrate LM, Koslover EF. The endoplasmic reticulum as an active liquid network. Proc Natl Acad Sci U S A 2024; 121:e2409755121. [PMID: 39392663 DOI: 10.1073/pnas.2409755121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Accepted: 09/06/2024] [Indexed: 10/12/2024] Open
Abstract
The peripheral endoplasmic reticulum (ER) forms a dense, interconnected, and constantly evolving network of membrane-bound tubules in eukaryotic cells. While individual structural elements and the morphogens that stabilize them have been described, a quantitative understanding of the dynamic large-scale network topology remains elusive. We develop a physical model of the ER as an active liquid network, governed by a balance of tension-driven shrinking and new tubule growth. This minimalist model gives rise to steady-state network structures with density and rearrangement timescales predicted from the junction mobility and tubule spawning rate. Several parameter-independent geometric features of the liquid network model are shown to be representative of ER architecture in live mammalian cells. The liquid network model connects the timescales of distinct dynamic features such as ring closure and new tubule growth in the ER. Furthermore, it demonstrates how the steady-state network morphology on a cellular scale arises from the balance of microscopic dynamic rearrangements.
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Affiliation(s)
| | - Samuel B Steen
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, MI 49546
| | - Greg Huber
- Chan Zuckerberg Biohub-San Francisco, San Francisco, CA 94158
| | - Laura M Westrate
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, MI 49546
| | - Elena F Koslover
- Department of Physics, University of California, San Diego, La Jolla, CA 92093
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3
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Wilson A, McCormick C. Reticulophagy and viral infection. Autophagy 2024. [PMID: 39394962 DOI: 10.1080/15548627.2024.2414424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 10/03/2024] [Accepted: 10/06/2024] [Indexed: 10/14/2024] Open
Abstract
All viruses are obligate intracellular parasites that use host machinery to synthesize viral proteins. In infected eukaryotes, viral secreted and transmembrane proteins are synthesized at the endoplasmic reticulum (ER). Many viruses refashion ER membranes into bespoke factories where viral products accumulate while evading host pattern recognition receptors. ER processes are tightly regulated to maintain cellular homeostasis, so viruses must either conform to ER regulatory mechanisms or subvert them to ensure efficient viral replication. Reticulophagy is a catabolic process that directs lysosomal degradation of ER components. There is accumulating evidence that reticulophagy serves as a form of antiviral defense; we call this defense "xERophagy" to acknowledge its relationship to xenophagy, the catabolic degradation of microorganisms by macroautophagy/autophagy. In turn, viruses can subvert reticulophagy to suppress host antiviral responses and support efficient viral replication. Here, we review the evidence for functional interplay between viruses and the host reticulophagy machinery.
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Affiliation(s)
- Alexa Wilson
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Craig McCormick
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
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4
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Sawyer EM, Jensen LE, Meehl JB, Larsen KP, Petito DA, Hurley JH, Voeltz GK. SigmaR1 shapes rough endoplasmic reticulum membrane sheets. Dev Cell 2024; 59:2566-2577.e7. [PMID: 38971154 DOI: 10.1016/j.devcel.2024.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 02/12/2024] [Accepted: 06/07/2024] [Indexed: 07/08/2024]
Abstract
Rough endoplasmic reticulum (ER) sheets are a fundamental domain of the ER and the gateway into the secretory pathway. Although reticulon proteins stabilize high-curvature ER tubules, it is unclear whether other proteins scaffold the flat membranes of rough ER sheets. Through a proteomics screen using ER sheet-localized RNA-binding proteins as bait, we identify the sigma-1 receptor (SigmaR1) as an ER sheet-shaping factor. High-resolution live cell imaging and electron tomography assign SigmaR1 as an ER sheet-localized factor whose levels determine the amount of rough ER sheets in cells. Structure-guided mutagenesis and in vitro reconstitution on giant unilamellar vesicles further support a mechanism whereby SigmaR1 oligomers use their extended arrays of amphipathic helices to bind and flatten the lumenal leaflet of ER membranes to oppose membrane curvature and stabilize rough ER sheets.
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Affiliation(s)
- Eric M Sawyer
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute
| | - Liv E Jensen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Janet B Meehl
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute
| | - Kevin P Larsen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Daniel A Petito
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute
| | - James H Hurley
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Gia K Voeltz
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute.
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Shibata Y, Mazur EE, Pan B, Paulo JA, Gygi SP, Chavan S, Valerio LSA, Zhang J, Rapoport TA. The membrane curvature-inducing REEP1-4 proteins generate an ER-derived vesicular compartment. Nat Commun 2024; 15:8655. [PMID: 39368994 PMCID: PMC11455953 DOI: 10.1038/s41467-024-52901-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 09/24/2024] [Indexed: 10/07/2024] Open
Abstract
The endoplasmic reticulum (ER) is shaped by abundant membrane curvature-generating proteins that include the REEP family member REEP5. The REEP1 subfamily, consisting of four proteins in mammals (REEP1-4), is less abundant and lack a N-terminal region. Mutations in REEP1 and REEP2 cause Hereditary Spastic Paraplegia, but the function of these four REEP proteins remains enigmatic. Here we show that REEP1-4 reside in a unique vesicular compartment and identify features that determine their localization. Mutations in REEP1-4 that compromise curvature generation, including those causing disease, relocalize the proteins to the bulk ER. These mutants interact with wild-type proteins to retain them in the ER, consistent with their autosomal-dominant disease inheritance. REEP1 vesicles contain the membrane fusogen atlastin-1, but not general ER proteins. We propose that REEP1-4 generate these vesicles themselves by budding from the ER, and that they cycle back to the ER by atlastin-mediated fusion. The vesicles may serve to regulate ER tubule dynamics.
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Affiliation(s)
- Yoko Shibata
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA.
- Howard Hughes Medical Institute, Boston, MA, USA.
| | - Emily E Mazur
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA
- Howard Hughes Medical Institute, Boston, MA, USA
| | - Buyan Pan
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA
- Howard Hughes Medical Institute, Boston, MA, USA
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA
| | - Suyog Chavan
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA
| | | | - Jiuchun Zhang
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA
| | - Tom A Rapoport
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 2115, USA.
- Howard Hughes Medical Institute, Boston, MA, USA.
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6
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Sada R, Yamamoto H, Matsumoto S, Harada A, Kikuchi A. Newly developed humanized anti-CKAP4 antibody suppresses pancreatic cancer growth by inhibiting DKK1-CKAP4 signaling. Cancer Sci 2024; 115:3358-3369. [PMID: 39118263 PMCID: PMC11447883 DOI: 10.1111/cas.16278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 06/26/2024] [Accepted: 06/28/2024] [Indexed: 08/10/2024] Open
Abstract
Cytoskeleton-associated protein 4 (CKAP4) is a cell surface receptor for Dickkopf 1 (DKK1), a secreted protein. The DKK1-CKAP4 pathway is activated in various malignant tumors, including pancreatic, lung, esophageal, and liver cancers, to promote tumor growth. Thus, CKAP4 has been expected to represent a novel molecular target of cancer therapy. Recombinant mouse anti-CKAP4 antibodies were generated based on an original mouse antibody (3F11-2B10) and inhibited DKK1-CKAP4 signaling and xenograft tumor formation induced by pancreatic cancer cells, which was comparable with 3F11-2B10. From the 3F11-2B10 nucleotide sequence, humanized anti-CKAP4 antibody (Hv1Lt1) was subsequently developed. The binding affinity of Hv1Lt1 for CKAP4 was superior to that of 3F11-2B10. Hv1Lt1 inhibited DKK1 binding to CKAP4, AKT activity, and sphere formation of pancreatic cancer cells, which was comparable with 3F11-2B10. Hv1Lt1 also suppressed xenograft tumor formation induced by human pancreatic cancer cells and tumor growth in murine cancer models, in which murine pancreatic cancer organoids were orthotopically transplanted into the pancreas. In resected tumor samples from mice treated with Hv1Lt1, anti-tumor immune reactions were modulated and cytotoxic T cells were highly infiltrated in the tumor microenvironment. Additionally, combination of Hv1Lt1 and other chemotherapy drugs exhibited stronger effects compared with monotherapy. These results suggest that Hv1Lt1 represents a promising anti-cancer therapy.
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Affiliation(s)
- Ryota Sada
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, Suita, Japan
- Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Suita, Japan
- Center for Infectious Disease Education and Research (CiDER), Osaka University, Suita, Japan
| | - Hideki Yamamoto
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Health Care Sciences, Jikei University of Health Care Sciences, Osaka, Japan
| | - Shinji Matsumoto
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, Suita, Japan
- Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Suita, Japan
- Center for Infectious Disease Education and Research (CiDER), Osaka University, Suita, Japan
| | - Akikazu Harada
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, Suita, Japan
- Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Suita, Japan
- Center for Infectious Disease Education and Research (CiDER), Osaka University, Suita, Japan
| | - Akira Kikuchi
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, Suita, Japan
- Center for Infectious Disease Education and Research (CiDER), Osaka University, Suita, Japan
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7
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Kuriyama S, Thasaneeya K, Itoh G, Kidoaki S, Tanaka M. Glyoxal-methyl-ethylene sulfonic acid fixative enhances the fixation of cytoskeletal structures for Förster resonance energy transfer measurements. Histochem Cell Biol 2024; 162:337-347. [PMID: 38880796 DOI: 10.1007/s00418-024-02304-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/03/2024] [Indexed: 06/18/2024]
Abstract
Förster resonance energy transfer (FRET) serves as a tool for measuring protein-protein interactions using various sensor molecules. The tension sensor module relies on FRET technology. In our study, this module was inserted within the actinin molecule to measure the surface tension of the cells. Given that the decay curve of FRET efficiency correlates with surface tension increase, precise and accurate efficiency measurement becomes crucial. Among the methods of FRET measurements, FRET efficiency remains the most accurate if sample fixation is successful. However, when cells were fixed with 4% paraformaldehyde (PFA), the actinin-FRET sensor diffused across the cytoplasm; this prompted us to explore fixation method enhancements. Glyoxal fixative has been reported to improve cytoskeletal morphologies compared to PFA. However, it was not known whether glyoxal fits FRET measurements. Glyoxal necessitates an acetic acid solution for fixation; however, acidic conditions could compromise fluorescence stability. We observed that the pH working range of glyoxal fixative aligns closely with MES (methyl-ethylene sulfonic acid) Good's buffer. Initially, we switched the acidic solution for MES buffer and optimized the fixation procedure for in vitro and in vivo FRET imaging. By comparing FRET measurements on hydrogels with known stiffness to tumor nodules in mouse lung, we estimated in vivo stiffness. The estimated stiffness of cancerous tissue was harder than the reported stiffness of smooth muscle. This discovery shed lights on how cancer cells perceive environmental stiffness during metastasis.
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Affiliation(s)
- Sei Kuriyama
- Department Molecular Medicine & Biochemistry, Akita University Fac. & Grad. Sch. Med, Akita City, Akita, 010-8543, Japan.
| | - Kuboki Thasaneeya
- Institute for Materials Chemistry and Engineering, Division Biomolecular Chemistry, Kyushu University, 744 Moto-Oka, Nishi-Ku, Fukuoka, 819-0395, Japan
| | - Go Itoh
- Department Molecular Medicine & Biochemistry, Akita University Fac. & Grad. Sch. Med, Akita City, Akita, 010-8543, Japan
| | - Satoru Kidoaki
- Institute for Materials Chemistry and Engineering, Division Biomolecular Chemistry, Kyushu University, 744 Moto-Oka, Nishi-Ku, Fukuoka, 819-0395, Japan
| | - Masamitsu Tanaka
- Department Molecular Medicine & Biochemistry, Akita University Fac. & Grad. Sch. Med, Akita City, Akita, 010-8543, Japan
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Tanaka Y, Farkhondeh A, Yang W, Ueno H, Noda M, Hirokawa N. Kinesin-1 mediates proper ER folding of the Ca V1.2 channel and maintains mouse glucose homeostasis. EMBO Rep 2024:10.1038/s44319-024-00246-y. [PMID: 39322740 DOI: 10.1038/s44319-024-00246-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 07/08/2024] [Accepted: 08/22/2024] [Indexed: 09/27/2024] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) from pancreatic beta cells is a principal mechanism for systemic glucose homeostasis, of which regulatory mechanisms are still unclear. Here we show that kinesin molecular motor KIF5B is essential for GSIS through maintaining the voltage-gated calcium channel CaV1.2 levels, by facilitating an Hsp70-to-Hsp90 chaperone exchange to pass through the quality control in the endoplasmic reticulum (ER). Phenotypic analyses of KIF5B conditional knockout (cKO) mouse beta cells revealed significant abolishment of glucose-stimulated calcium transients, which altered the behaviors of insulin granules via abnormally stabilized cortical F-actin. KIF5B and Hsp90 colocalize to microdroplets on ER sheets, where CaV1.2 but not Kir6.2 is accumulated. In the absence of KIF5B, CaV1.2 fails to be transferred from Hsp70 to Hsp90 via STIP1, and is likely degraded via the proteasomal pathway. KIF5B and Hsc70 overexpression increased CaV1.2 expression via enhancing its chaperone binding. Thus, ER sheets may serve as the place of KIF5B- and Hsp90-dependent chaperone exchange, which predominantly facilitates CaV1.2 production in beta cells and properly enterprises GSIS against diabetes.
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Affiliation(s)
- Yosuke Tanaka
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo, 113-0033, Japan
| | - Atena Farkhondeh
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo, 113-0033, Japan
| | - Wenxing Yang
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo, 113-0033, Japan
| | - Hitoshi Ueno
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo, 113-0033, Japan
| | - Mitsuhiko Noda
- Department of Diabetes, Metabolism and Endocrinology, Ichikawa Hospital, International University of Health and Welfare, Chiba, 272-0827, Japan
| | - Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo, 113-0033, Japan.
- Department of Advanced Morphological Imaging, Graduate School of Medicine, Juntendo University, 2-1-1, Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
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Tran QTH, Kondo N, Ueda H, Matsuo Y, Tsukaguchi H. Altered Endoplasmic Reticulum Integrity and Organelle Interactions in Living Cells Expressing INF2 Variants. Int J Mol Sci 2024; 25:9783. [PMID: 39337270 PMCID: PMC11431639 DOI: 10.3390/ijms25189783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2024] [Revised: 09/05/2024] [Accepted: 09/06/2024] [Indexed: 09/30/2024] Open
Abstract
The cytoskeleton mediates fundamental cellular processes by organizing inter-organelle interactions. Pathogenic variants of inverted formin 2 (INF2) CAAX isoform, an actin assembly factor that is predominantly expressed in the endoplasmic reticulum (ER), are linked to focal segmental glomerulosclerosis (FSGS) and Charcot-Marie-Tooth (CMT) neuropathy. To investigate how pathogenic INF2 variants alter ER integrity, we used high-resolution live imaging of HeLa cells. Cells expressing wild-type (WT) INF2 showed a predominant tubular ER with perinuclear clustering. Cells expressing INF2 FSGS variants that cause mild and intermediate disease induced more sheet-like ER, a pattern similar to that seen for cells expressing WT-INF2 that were treated with actin and microtubule (MT) inhibitors. Dual CMT-FSGS INF2 variants led to more severe ER dysmorphism, with a diffuse, fragmented ER and coarse INF2 aggregates. Proper organization of both F-actin and MT was needed to modulate the tubule vs. sheet conformation balance, while MT arrays regulated spatial expansion of tubular ER in the cell periphery. Pathogenic INF2 variants also induced mitochondria fragmentation and dysregulated mitochondria distribution. Such mitochondrial abnormalities were more prominent for cells expressing CMT-FSGS compared to those with FSGS variants, indicating that the severity of the dysfunction is linked to the degree of cytoskeletal disorganization. Our observations suggest that pathogenic INF2 variants disrupt ER continuity by altering interactions between the ER and the cytoskeleton that in turn impairs inter-organelle communication, especially at ER-mitochondria contact sites. ER continuity defects may be a common disease mechanism involved in both peripheral neuropathy and glomerulopathy.
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Affiliation(s)
- Quynh Thuy Huong Tran
- Second Department of Internal Medicine, Division of Nephrology, Kansai Medical University, Hirakata 573-1010, Japan
| | - Naoyuki Kondo
- Department of Molecular Genetics, Institute of Biochemical Science, Kansai Medical University, Hirakata 573-1010, Japan
| | - Hiroko Ueda
- Second Department of Internal Medicine, Division of Nephrology, Kansai Medical University, Hirakata 573-1010, Japan
| | - Yoshiyuki Matsuo
- Central Research Center, Institute of Biomedical Science, Kansai Medical University, Hirakata 573-1010, Japan
| | - Hiroyasu Tsukaguchi
- Second Department of Internal Medicine, Division of Nephrology, Kansai Medical University, Hirakata 573-1010, Japan
- Clinical Genetics Center, Kansai Medical University Hospital, Hirakata 573-1191, Japan
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Wang P, Shao Y, Al-Nusaif M, Zhang J, Yang H, Yang Y, Kim K, Li S, Liu C, Cai H, Le W. Pathological characteristics of axons and alterations of proteomic and lipidomic profiles in midbrain dopaminergic neurodegeneration induced by WDR45-deficiency. Mol Neurodegener 2024; 19:62. [PMID: 39183331 PMCID: PMC11346282 DOI: 10.1186/s13024-024-00746-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 07/17/2024] [Indexed: 08/27/2024] Open
Abstract
BACKGROUND Although WD repeat domain 45 (WDR45) mutations have been linked to β -propeller protein-associated neurodegeneration (BPAN), the precise molecular and cellular mechanisms behind this disease remain elusive. This study aims to shed light on the impacts of WDR45-deficiency on neurodegeneration, specifically axonal degeneration, within the midbrain dopaminergic (DAergic) system. We hope to better understand the disease process by examining pathological and molecular alterations, especially within the DAergic system. METHODS To investigate the impacts of WDR45 dysfunction on mouse behaviors and DAergic neurons, we developed a mouse model in which WDR45 was conditionally knocked out in the midbrain DAergic neurons (WDR45cKO). Through a longitudinal study, we assessed alterations in the mouse behaviors using open field, rotarod, Y-maze, and 3-chamber social approach tests. We utilized a combination of immunofluorescence staining and transmission electron microscopy to examine the pathological changes in DAergic neuron soma and axons. Additionally, we performed proteomic and lipidomic analyses of the striatum from young and aged mice to identify the molecules and processes potentially involved in the striatal pathology during aging. Further more, primary midbrain neuronal culture was employed to explore the molecular mechanisms leading to axonal degeneration. RESULTS Our study of WDR45cKO mice revealed a range of deficits, including impaired motor function, emotional instability, and memory loss, coinciding with the profound reduction of midbrain DAergic neurons. The neuronal loss, we observed massive axonal enlargements in the dorsal and ventral striatum. These enlargements were characterized by the accumulation of extensively fragmented tubular endoplasmic reticulum (ER), a hallmark of axonal degeneration. Proteomic analysis of the striatum showed that the differentially expressed proteins were enriched in metabolic processes. The carbohydrate metabolic and protein catabolic processes appeared earlier, and amino acid, lipid, and tricarboxylic acid metabolisms were increased during aging. Of note, we observed a tremendous increase in the expression of lysophosphatidylcholine acyltransferase 1 (Lpcat1) that regulates phospholipid metabolism, specifically in the conversion of lysophosphatidylcholine (LPC) to phosphatidylcholine (PC) in the presence of acyl-CoA. The lipidomic results consistently suggested that differential lipids were concentrated on PC and LPC. Axonal degeneration was effectively ameliorated by interfering Lpcat1 expression in primary cultured WDR45-deficient DAergic neurons, proving that Lpcat1 and its regulated lipid metabolism, especially PC and LPC metabolism, participate in controlling the axonal degeneration induced by WDR45 deficits. CONCLUSIONS In this study, we uncovered the molecular mechanisms underlying the contribution of WDR45 deficiency to axonal degeneration, which involves complex relationships between phospholipid metabolism, autophagy, and tubular ER. These findings greatly advance our understanding of the fundamental molecular mechanisms driving axonal degeneration and may provide a foundation for developing novel mechanistically based therapeutic interventions for BPAN and other neurodegenerative diseases.
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Affiliation(s)
- Panpan Wang
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Yaping Shao
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Murad Al-Nusaif
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Jun Zhang
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Huijia Yang
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Yuting Yang
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Kunhyok Kim
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Song Li
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China
| | - Cong Liu
- Interdisciplinary Research Center On Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China
| | - Huaibin Cai
- Transgenic Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Weidong Le
- Liaoning Provincial Key Laboratory for Research On the Pathogenic Mechanisms of Neurological Diseases, The First Affiliated Hospital, Dalian Medical University, Dalian, 116021, China.
- Institute of Neurology, Sichuan Academy of Medical Science, Sichuan Provincial Hospital, Chengdu, 610072, China.
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11
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Koppers M, Özkan N, Nguyen HH, Jurriens D, McCaughey J, Nguyen DTM, Li CH, Stucchi R, Altelaar M, MacGillavry HD, Kapitein LC, Hoogenraad CC, Farías GG. Axonal endoplasmic reticulum tubules control local translation via P180/RRBP1-mediated ribosome interactions. Dev Cell 2024; 59:2053-2068.e9. [PMID: 38815583 PMCID: PMC11338522 DOI: 10.1016/j.devcel.2024.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 01/31/2024] [Accepted: 05/09/2024] [Indexed: 06/01/2024]
Abstract
Local mRNA translation in axons is critical for the spatiotemporal regulation of the axonal proteome. A wide variety of mRNAs are localized and translated in axons; however, how protein synthesis is regulated at specific subcellular sites in axons remains unclear. Here, we establish that the axonal endoplasmic reticulum (ER) supports axonal translation in developing rat hippocampal cultured neurons. Axonal ER tubule disruption impairs local translation and ribosome distribution. Using nanoscale resolution imaging, we find that ribosomes make frequent contacts with axonal ER tubules in a translation-dependent manner and are influenced by specific extrinsic cues. We identify P180/RRBP1 as an axonally distributed ribosome receptor that regulates local translation and binds to mRNAs enriched for axonal membrane proteins. Importantly, the impairment of axonal ER-ribosome interactions causes defects in axon morphology. Our results establish a role for the axonal ER in dynamically localizing mRNA translation, which is important for proper neuron development.
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Affiliation(s)
- Max Koppers
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands.
| | - Nazmiye Özkan
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Ha H Nguyen
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Daphne Jurriens
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Janine McCaughey
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Dan T M Nguyen
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Chun Hei Li
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Riccardo Stucchi
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands; Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Harold D MacGillavry
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Lukas C Kapitein
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands; Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA
| | - Ginny G Farías
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands.
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12
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Donahue E, Hepowit NL, Keuchel B, Mulligan AG, Johnson DJ, Ellisman M, Arrojo E Drigo R, MacGurn J, Burkewitz K. ER-phagy drives age-onset remodeling of endoplasmic reticulum structure-function and lifespan. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.07.607085. [PMID: 39149405 PMCID: PMC11326278 DOI: 10.1101/2024.08.07.607085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
The endoplasmic reticulum (ER) comprises an array of structurally distinct subdomains, each with characteristic functions. While altered ER-associated processes are linked to age-onset pathogenesis, whether shifts in ER morphology underlie these functional changes is unclear. We report that ER remodeling is a conserved feature of the aging process in models ranging from yeast to C. elegans and mammals. Focusing on C. elegans as an exemplar of metazoan aging, we find that as animals age, ER mass declines in virtually all tissues and ER morphology shifts from rough sheets to tubular ER. The accompanying large-scale shifts in proteomic composition correspond to the ER turning from protein synthesis to lipid metabolism. To drive this substantial remodeling, ER-phagy is activated early in adulthood, promoting turnover of rough ER in response to rises in luminal protein-folding burden and reduced global protein synthesis. Surprisingly, ER remodeling is a pro-active and protective response during aging, as ER-phagy impairment limits lifespan in yeast and diverse lifespan-extending paradigms promote profound remodeling of ER morphology even in young animals. Altogether our results reveal ER-phagy and ER morphological dynamics as pronounced, underappreciated mechanisms of both normal aging and enhanced longevity.
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Affiliation(s)
- Ekf Donahue
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - N L Hepowit
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - B Keuchel
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - A G Mulligan
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - D J Johnson
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - M Ellisman
- National Center for Microscopy and Imaging Research, Department of Neurosciences, University of California San Diego, La Jolla, CA, 92093, USA
| | - R Arrojo E Drigo
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37240, USA
| | - J MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - K Burkewitz
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
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13
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Nair KA, Liu B. Navigating the landscape of the unfolded protein response in CD8 + T cells. Front Immunol 2024; 15:1427859. [PMID: 39026685 PMCID: PMC11254671 DOI: 10.3389/fimmu.2024.1427859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Accepted: 06/24/2024] [Indexed: 07/20/2024] Open
Abstract
Endoplasmic reticulum stress occurs due to large amounts of misfolded proteins, hypoxia, nutrient deprivation, and more. The unfolded protein is a complex intracellular signaling network designed to operate under this stress. Composed of three individual arms, inositol-requiring enzyme 1, protein kinase RNA-like ER kinase, and activating transcription factor-6, the unfolded protein response looks to resolve stress and return to proteostasis. The CD8+ T cell is a critical cell type for the adaptive immune system. The unfolded protein response has been shown to have a wide-ranging spectrum of effects on CD8+ T cells. CD8+ T cells undergo cellular stress during activation and due to environmental insults. However, the magnitude of the effects this response has on CD8+ T cells is still understudied. Thus, studying these pathways is important to unraveling the inner machinations of these powerful cells. In this review, we will highlight the recent literature in this field, summarize the three pathways of the unfolded protein response, and discuss their roles in CD8+ T cell biology and functionality.
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Affiliation(s)
- Keith Alan Nair
- Division of Hematology, Department of Internal Medicine, The Ohio State University Comprehensive Cancer Center, Columbus, OH, United States
- The Pelotonia Institute for Immuno-Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH, United States
| | - Bei Liu
- Division of Hematology, Department of Internal Medicine, The Ohio State University Comprehensive Cancer Center, Columbus, OH, United States
- The Pelotonia Institute for Immuno-Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH, United States
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14
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Kataoka-Hamai C. Triacylglycerol-droplet-induced bilayer spontaneous curvature in giant unilamellar vesicles. Biophys J 2024; 123:1857-1868. [PMID: 38822522 PMCID: PMC11267425 DOI: 10.1016/j.bpj.2024.05.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 04/05/2024] [Accepted: 05/29/2024] [Indexed: 06/03/2024] Open
Abstract
This study investigated the incorporation of triacylglycerol droplets in the bilayers of giant unilamellar vesicles (GUVs) using four triacylglycerols and four phosphatidylcholines by confocal laser scanning microscopy. The triacylglycerol droplets were incorporated between the monolayer leaflets of the GUVs. Among the spherical droplets protruding on only one side of the bilayers, the droplets bound to the outer leaflets outnumbered those bound to the inner leaflets. The more frequent droplet binding to the outer leaflet caused transbilayer asymmetry in the droplet surface density. A vesicle consisting of a single-bilayer spherical segment and a double-bilayer spherical segment was also observed. The yield of these vesicles was comparable with or higher than that of the droplet-incorporating GUVs for many of the phosphatidylcholine-triacylglycerol combinations. In a vesicle consisting of single-bilayer and double-bilayer segments, most of the triacylglycerol droplets were localized on the outermost membrane surface along the segment boundary and in the double-bilayer segment. To rationalize the formation of these vesicle structures, we propose that the transbilayer asymmetry in the droplet surface density induces spontaneous curvature of the bilayer, with the bilayer spontaneously bending away from the droplets. Energy calculations performed assuming the existence of spontaneous curvature of the bilayer corroborated the experimentally determined membrane shapes for the vesicles consisting of unilamellar and bilamellar regions.
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Affiliation(s)
- Chiho Kataoka-Hamai
- Research Center for Macromolecules and Biomaterials, National Institute for Materials Science, Tsukuba, Ibaraki, Japan.
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15
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Ortiz HR, Cruz Flores P, Podgorski J, Ramonett A, Ahmed T, Hempel N, Charest PG, Ellis NA, Langlais PR, Montfort WR, Mythreye K, Kumar S, Lee NY. Extracellular signals induce dynamic ER remodeling through αTAT1-dependent microtubule acetylation. Neoplasia 2024; 53:101003. [PMID: 38759377 PMCID: PMC11127537 DOI: 10.1016/j.neo.2024.101003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 04/26/2024] [Indexed: 05/19/2024]
Abstract
Dynamic changes in the endoplasmic reticulum (ER) morphology are central to maintaining cellular homeostasis. Microtubules (MT) facilitate the continuous remodeling of the ER network into sheets and tubules by coordinating with many ER-shaping protein complexes, although how this process is controlled by extracellular signals remains unknown. Here we report that TAK1, a kinase responsive to various growth factors and cytokines including TGF-β and TNF-α, triggers ER tubulation by activating αTAT1, an MT-acetylating enzyme that enhances ER-sliding. We show that this TAK1/αTAT1-dependent ER remodeling promotes cell survival by actively downregulating BOK, an ER membrane-associated proapoptotic effector. While BOK is normally protected from degradation when complexed with IP3R, it is rapidly degraded upon their dissociation during the ER sheets-to-tubules conversion. These findings demonstrate a distinct mechanism of ligand-induced ER remodeling and suggest that the TAK1/αTAT1 pathway may be a key target in ER stress and dysfunction.
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Affiliation(s)
- Hannah R Ortiz
- Department of Pharmacology, University of Arizona, Tucson, AZ 85724, USA
| | - Paola Cruz Flores
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ 85724, USA
| | - Julia Podgorski
- Department of Pharmacology, University of Arizona, Tucson, AZ 85724, USA
| | - Aaron Ramonett
- Department of Pharmacology, University of Arizona, Tucson, AZ 85724, USA
| | - Tasmia Ahmed
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ 85724, USA
| | - Nadine Hempel
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Pascale G Charest
- Department of Molecular & Cellular Biology, University of Arizona, Tucson, AZ 85724, USA
| | - Nathan A Ellis
- Department of Cellular & Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA
| | - Paul R Langlais
- Department of Medicine, University of Arizona, Tucson, AZ 85724, USA
| | - William R Montfort
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ 85724, USA
| | | | - Sanjay Kumar
- Division of Biology, Indian Institute of Science Education & Research Tirupati, Mangalam Tirupati 517507, India.
| | - Nam Y Lee
- Department of Pharmacology, University of Arizona, Tucson, AZ 85724, USA; Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ 85724, USA; Comprehensive Cancer Center, University of Arizona, Tucson, AZ 85724, USA.
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16
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Gong B, Johnston JD, Thiemicke A, de Marco A, Meyer T. Endoplasmic reticulum-plasma membrane contact gradients direct cell migration. Nature 2024; 631:415-423. [PMID: 38867038 PMCID: PMC11236710 DOI: 10.1038/s41586-024-07527-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 05/07/2024] [Indexed: 06/14/2024]
Abstract
Directed cell migration is driven by the front-back polarization of intracellular signalling1-3. Receptor tyrosine kinases and other inputs activate local signals that trigger membrane protrusions at the front2,4-6. Equally important is a long-range inhibitory mechanism that suppresses signalling at the back to prevent the formation of multiple fronts7-9. However, the identity of this mechanism is unknown. Here we report that endoplasmic reticulum-plasma membrane (ER-PM) contact sites are polarized in single and collectively migrating cells. The increased density of these ER-PM contacts at the back provides the ER-resident PTP1B phosphatase more access to PM substrates, which confines receptor signalling to the front and directs cell migration. Polarization of the ER-PM contacts is due to microtubule-regulated polarization of the ER, with more RTN4-rich curved ER at the front and more CLIMP63-rich flattened ER at the back. The resulting ER curvature gradient leads to small and unstable ER-PM contacts only at the front. These contacts flow backwards and grow to large and stable contacts at the back to form the front-back ER-PM contact gradient. Together, our study suggests that the structural polarity mediated by ER-PM contact gradients polarizes cell signalling, directs cell migration and prolongs cell migration.
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Affiliation(s)
- Bo Gong
- Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY, USA.
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA.
| | - Jake D Johnston
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
- Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Alexander Thiemicke
- Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY, USA
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | - Alex de Marco
- Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Tobias Meyer
- Department of Cell and Developmental Biology, Weill Cornell Medicine, New York, NY, USA.
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA.
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17
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Zhao Z, Satarifard V, Lipowsky R, Dimova R. Membrane nanotubes transform into double-membrane sheets at condensate droplets. Proc Natl Acad Sci U S A 2024; 121:e2321579121. [PMID: 38900795 PMCID: PMC11214096 DOI: 10.1073/pnas.2321579121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 05/15/2024] [Indexed: 06/22/2024] Open
Abstract
Cellular membranes exhibit a multitude of highly curved morphologies such as buds, nanotubes, cisterna-like sheets defining the outlines of organelles. Here, we mimic cell compartmentation using an aqueous two-phase system of dextran and poly(ethylene glycol) encapsulated in giant vesicles. Upon osmotic deflation, the vesicle membrane forms nanotubes, which undergo surprising morphological transformations at the liquid-liquid interfaces inside the vesicles. At these interfaces, the nanotubes transform into cisterna-like double-membrane sheets (DMS) connected to the mother vesicle via short membrane necks. Using super-resolution (stimulated emission depletion) microscopy and theoretical considerations, we construct a morphology diagram predicting the tube-to-sheet transformation, which is driven by a decrease in the free energy. Nanotube knots can prohibit the tube-to-sheet transformation by blocking water influx into the tubes. Because both nanotubes and DMSs are frequently formed by cellular membranes, understanding the formation and transformation between these membrane morphologies provides insight into the origin and evolution of cellular organelles.
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Affiliation(s)
- Ziliang Zhao
- Max Planck Institute of Colloids and Interfaces, Potsdam14476, Germany
- Leibniz Institute of Photonic Technology e.V., Jena07745, Germany
- Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Jena07743, Germany
| | - Vahid Satarifard
- Max Planck Institute of Colloids and Interfaces, Potsdam14476, Germany
- Yale Institute for Network Science, Yale University, New Haven, CT06520
| | - Reinhard Lipowsky
- Max Planck Institute of Colloids and Interfaces, Potsdam14476, Germany
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Potsdam14476, Germany
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18
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Lewis AJO, Zhong F, Keenan RJ, Hegde RS. Structural analysis of the dynamic ribosome-translocon complex. eLife 2024; 13:RP95814. [PMID: 38896445 PMCID: PMC11186639 DOI: 10.7554/elife.95814] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024] Open
Abstract
The protein translocon at the endoplasmic reticulum comprises the Sec61 translocation channel and numerous accessory factors that collectively facilitate the biogenesis of secretory and membrane proteins. Here, we leveraged recent advances in cryo-electron microscopy (cryo-EM) and structure prediction to derive insights into several novel configurations of the ribosome-translocon complex. We show how a transmembrane domain (TMD) in a looped configuration passes through the Sec61 lateral gate during membrane insertion; how a nascent chain can bind and constrain the conformation of ribosomal protein uL22; and how the translocon-associated protein (TRAP) complex can adjust its position during different stages of protein biogenesis. Most unexpectedly, we find that a large proportion of translocon complexes contains RAMP4 intercalated into Sec61's lateral gate, widening Sec61's central pore and contributing to its hydrophilic interior. These structures lead to mechanistic hypotheses for translocon function and highlight a remarkably plastic machinery whose conformations and composition adjust dynamically to its diverse range of substrates.
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Affiliation(s)
- Aaron JO Lewis
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Frank Zhong
- Department of Molecular Genetics and Cell Biology, The University of ChicagoChicagoUnited States
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of ChicagoChicagoUnited States
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19
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Guan L, Ge R, Ma S. Newsights of endoplasmic reticulum in hypoxia. Biomed Pharmacother 2024; 175:116812. [PMID: 38781866 DOI: 10.1016/j.biopha.2024.116812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 05/19/2024] [Accepted: 05/20/2024] [Indexed: 05/25/2024] Open
Abstract
The endoplasmic reticulum (ER) is important to cells because of its essential functions, including synthesizing three major nutrients and ion transport. When cellular homeostasis is disrupted, ER quality control (ERQC) system is activated effectively to remove misfolded and unfolded proteins through ER-phagy, ER-related degradation (ERAD), and molecular chaperones. When unfolded protein response (UPR) and ER stress are activated, the cell may be suffering a huge blow, and the most probable consequence is apoptosis. The membrane contact points between the ER and sub-organelles contribute to communication between the organelles. The decrease in oxygen concentration affects the morphology and structure of the ER, thereby affecting its function and further disrupting the stable state of cells, leading to the occurrence of disease. In this study, we describe the functions of ER-, ERQC-, and ER-related membrane contact points and their changes under hypoxia, which will help us further understand ER and treat ER-related diseases.
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Affiliation(s)
- Lu Guan
- Qinghai University, Xining, Qinghai, China
| | - Rili Ge
- Key Laboratory of the Ministry of High Altitude Medicine, Qinghai University, Xining, Qinghai, China; Key Laboratory of Applied Fundamentals of High Altitude Medicine, (Qinghai-Utah Joint Key Laboratory of Plateau Medicine), Qinghai University, Xining, Qinghai, China; Laboratory for High Altitude Medicine of Qinghai Province, Qinghai University, Xining, Qinghai, China
| | - Shuang Ma
- Key Laboratory of the Ministry of High Altitude Medicine, Qinghai University, Xining, Qinghai, China; Key Laboratory of Applied Fundamentals of High Altitude Medicine, (Qinghai-Utah Joint Key Laboratory of Plateau Medicine), Qinghai University, Xining, Qinghai, China; Laboratory for High Altitude Medicine of Qinghai Province, Qinghai University, Xining, Qinghai, China.
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20
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Chowdhury SP, Solley SC, Polishchuk E, Bacal J, Conrad JE, Gardner BM, Acosta-Alvear D, Zappa F. Baseline unfolded protein response signaling adjusts the timing of the mammalian cell cycle. Mol Biol Cell 2024; 35:br12. [PMID: 38656789 PMCID: PMC11238080 DOI: 10.1091/mbc.e23-11-0419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 04/16/2024] [Accepted: 04/17/2024] [Indexed: 04/26/2024] Open
Abstract
The endoplasmic reticulum (ER) is a single-copy organelle that cannot be generated de novo, suggesting coordination between the mechanisms overseeing ER integrity and those controlling the cell cycle to maintain organelle inheritance. The Unfolded Protein Response (UPR) is a conserved signaling network that regulates ER homeostasis. Here, we show that pharmacological and genetic inhibition of the UPR sensors IRE1, ATF6, and PERK in unstressed cells delays the cell cycle, with PERK inhibition showing the most penetrant effect, which was associated with a slowdown of the G1-to-S/G2 transition. Treatment with the small molecule ISRIB to bypass the effects of PERK-dependent phosphorylation of the translation initiation factor eIF2α had no such effect, suggesting that cell cycle timing depends on PERK's kinase activity but is independent of eIF2α phosphorylation. Using complementary light and electron microscopy and flow cytometry-based analyses, we also demonstrate that the ER enlarges before mitosis. Together, our results suggest coordination between UPR signaling and the cell cycle to maintain ER physiology during cell division.
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Affiliation(s)
- Soham P. Chowdhury
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Sabrina C. Solley
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Elena Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM), 80078 Pozzuoli, Naples, Italy
| | - Julien Bacal
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Julia E. Conrad
- Altos Labs Bay Area Institute of Science, Altos Labs, Redwood City, CA 94065
| | - Brooke M. Gardner
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Diego Acosta-Alvear
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Francesca Zappa
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106
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21
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Niemelä LRK, Koskela EV, Frey AD. Modification of the endoplasmic reticulum morphology enables improved recombinant antibody expression in Saccharomyces cerevisiae. J Biotechnol 2024; 387:1-11. [PMID: 38555020 DOI: 10.1016/j.jbiotec.2024.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 03/23/2024] [Accepted: 03/24/2024] [Indexed: 04/02/2024]
Abstract
The yeast Saccharomyces cerevisiae is a versatile cell factory used for manufacturing of a wide range of products, among them recombinant proteins. Protein folding is one of the rate-limiting processes and this shortcoming is often overcome by the expression of folding catalysts and chaperones in the endoplasmic reticulum (ER). In this work, we aimed to establish the impact of ER structure on cellular productivity. The reticulon proteins Rtn1p and Rtn2p, and Yop1p are membrane curvature inducing proteins that define the morphology of the ER and depletion of these proteins creates yeast cells with a higher ER sheet-to-tubule ratio. We created yeast strains with different combinations of deletions of Rtn1p, Rtn2p, and Yop1p coding genes in cells with a normal or expanded ER lumen. We identified strains that reached up to 2.2-fold higher antibody titres compared to the control strain. The expanded ER membrane reached by deletion of the lipid biosynthesis repressor OPI1 was essential for the increased productivity. The improved specific productivity was accompanied by an up to 2-fold enlarged ER surface area and a 1.5-fold increased cross-sectional cell area. Furthermore, the strains with enlarged ER displayed an attenuated unfolded protein response. These results underline the impact that ER structures have on productivity and support the notion that reprogramming subcellular structures belongs into the toolbox of synthetic biology.
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Affiliation(s)
- Laura R K Niemelä
- Aalto University, Department of Bioproducts and Biosystems, Espoo, Finland
| | - Essi V Koskela
- Aalto University, Department of Bioproducts and Biosystems, Espoo, Finland
| | - Alexander D Frey
- Aalto University, Department of Bioproducts and Biosystems, Espoo, Finland.
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22
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Santinho A, Carpentier M, Lopes Sampaio J, Omrane M, Thiam AR. Giant organelle vesicles to uncover intracellular membrane mechanics and plasticity. Nat Commun 2024; 15:3767. [PMID: 38704407 PMCID: PMC11069511 DOI: 10.1038/s41467-024-48086-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 04/22/2024] [Indexed: 05/06/2024] Open
Abstract
Tools for accessing and studying organelles remain underdeveloped. Here, we present a method by which giant organelle vesicles (GOVs) are generated by submitting cells to a hypotonic medium followed by plasma membrane breakage. By this means, GOVs ranging from 3 to over 10 µm become available for micromanipulation. GOVs are made from organelles such as the endoplasmic reticulum, endosomes, lysosomes and mitochondria, or in contact with one another such as giant mitochondria-associated ER membrane vesicles. We measure the mechanical properties of each organelle-derived GOV and find that they have distinct properties. In GOVs procured from Cos7 cells, for example, bending rigidities tend to increase from the endoplasmic reticulum to the plasma membrane. We also found that the mechanical properties of giant endoplasmic reticulum vesicles (GERVs) vary depending on their interactions with other organelles or the metabolic state of the cell. Lastly, we demonstrate GERVs' biochemical activity through their capacity to synthesize triglycerides and assemble lipid droplets. These findings underscore the potential of GOVs as valuable tools for studying the biophysics and biology of organelles.
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Affiliation(s)
- Alexandre Santinho
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Maxime Carpentier
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Julio Lopes Sampaio
- Institut Curie, PSL Research University, Plateforme de Métabolomique et Lipidomique, 26 rue d'Ulm, Paris, France
| | - Mohyeddine Omrane
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France.
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23
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Johnson DH, Kou OH, Bouzos N, Zeno WF. Protein-membrane interactions: sensing and generating curvature. Trends Biochem Sci 2024; 49:401-416. [PMID: 38508884 PMCID: PMC11069444 DOI: 10.1016/j.tibs.2024.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 02/20/2024] [Accepted: 02/23/2024] [Indexed: 03/22/2024]
Abstract
Biological membranes are integral cellular structures that can be curved into various geometries. These curved structures are abundant in cells as they are essential for various physiological processes. However, curved membranes are inherently unstable, especially on nanometer length scales. To stabilize curved membranes, cells can utilize proteins that sense and generate membrane curvature. In this review, we summarize recent research that has advanced our understanding of interactions between proteins and curved membrane surfaces, as well as work that has expanded our ability to study curvature sensing and generation. Additionally, we look at specific examples of cellular processes that require membrane curvature, such as neurotransmission, clathrin-mediated endocytosis (CME), and organelle biogenesis.
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Affiliation(s)
- David H Johnson
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA
| | - Orianna H Kou
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA
| | - Nicoletta Bouzos
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA
| | - Wade F Zeno
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA.
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24
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Falahati H, Wu Y, De Camilli P. Ectopic Reconstitution of a Spine-Apparatus Like Structure Provides Insight into Mechanisms Underlying Its Formation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.16.589782. [PMID: 38659799 PMCID: PMC11042382 DOI: 10.1101/2024.04.16.589782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The endoplasmic reticulum (ER) is a continuous cellular endomembrane network that displays focal specializations. Most notable examples of such specializations include the spine apparatus of neuronal dendrites, and the cisternal organelle of axonal initial segments. Both organelles exhibit stacks of smooth ER sheets with a narrow lumen and interconnected by a dense protein matrix. The actin-binding protein synaptopodin is required for their formation. Here, we report that expression in non-neuronal cells of a synaptopodin construct targeted to the ER is sufficient to generate stacked ER cisterns resembling the spine apparatus with molecular properties distinct from the surrounding ER. Cisterns within these stacks are connected to each other by an actin-based matrix that contains proteins also found at the spine apparatus of neuronal spines. These findings reveal a critical role of a synaptopodin-dependent actin matrix in generating cisternal stacks. These ectopically generated structures provide insight into spine apparatus morphogenesis.
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Affiliation(s)
- Hanieh Falahati
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
| | - Yumei Wu
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
| | - Pietro De Camilli
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
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25
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Niu X, Shen Y, Wen Y, Mi X, Xie J, Zhang Y, Ding Z. KTN1 mediated unfolded protein response protects keratinocytes from ionizing radiation-induced DNA damage. J Dermatol Sci 2024; 114:24-33. [PMID: 38448340 DOI: 10.1016/j.jdermsci.2024.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 02/11/2024] [Accepted: 02/22/2024] [Indexed: 03/08/2024]
Abstract
BACKGROUND The unfolded protein response (UPR) is one of the cytoprotective mechanisms against various stresses and essential for the normal function of skin. Skin injury caused by ionizing radiation (IR) is a common side effect of radiotherapy and it is unclear how UPR affects IR-induced skin injury. OBJECTIVES To verify the effect of UPR on IR-induced DNA damage in keratinocytes and the relation between an endoplasmic reticulum (ER) protein KTN1 and UPR. METHODS All experiments were performed on keratinocytes models: HaCaT and HEK-A. ER lumen and the expression levels of KTN1 and UPR pathway proteins (PERK, IRE1α and ATF6) were examined by transmission electron microscopy and immunoblotting, respectively. 4-PBA, an UPR inhibitor, was used to detected its effects on DNA damage and cell proliferation. Subsequently, the effects of KTN1 deletion on UPR, DNA damage and cell proliferation after IR were detected. Tunicamycin was used to reactivate UPR and then we examined its effects on DNA damage. RESULTS UPR was activated by IR in keratinocytes. Inhibition of UPR aggravated DNA damage and suppressed cell proliferation after IR. KTN1 expression was upregulated by IR and KTN1 depletion reduced ER expansion and the expression of UPR-related proteins. Moreover, KTN1 depletion aggravated DNA damage and suppressed cell proliferation after IR could reversed by reactivation of UPR. CONCLUSION KTN1 deletion aggravates IR-induced keratinocyte DNA damage via inhibiting UPR. Our findings provide new insights into the mechanisms of keratinocytes in response to IR-induced damage.
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Affiliation(s)
- Xinli Niu
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China
| | - Yi Shen
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China
| | - Yunhan Wen
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China
| | - Xing Mi
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China
| | - Jing Xie
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China
| | - Ying Zhang
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China
| | - Zhenhua Ding
- Department of Radiation Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, NMPA Key Laboratory for Safety Evaluation of Cosmetics, School of Public Health, Southern Medical University, Guangzhou, China.
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26
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Mann MJ, Melendez-Suchi C, Vorndran HE, Sukhoplyasova M, Flory AR, Irvine MC, Iyer AR, Guerriero CJ, Brodsky JL, Hendershot LM, Buck TM. Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum function. Mol Biol Cell 2024; 35:ar59. [PMID: 38446639 PMCID: PMC11064666 DOI: 10.1091/mbc.e24-01-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 02/20/2024] [Accepted: 02/29/2024] [Indexed: 03/08/2024] Open
Abstract
GRP170 (Hyou1) is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds nonnative proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of mouse embryonic fibroblasts obtained from mice in which LoxP sites were engineered in the Hyou1 loci (Hyou1LoxP/LoxP). A doxycycline-regulated Cre recombinase was stably introduced into these cells. Induction of Cre resulted in depletion of Grp170 protein which culminated in cell death. As Grp170 levels fell we observed a portion of BiP fractionating with insoluble material, increased binding of BiP to a client with a concomitant reduction in its turnover, and reduced solubility of an aggregation-prone BiP substrate. Consistent with disrupted BiP functions, we observed reactivation of BiP and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and provide hypotheses as to why mutations in the Hyou1 locus are linked to human disease.
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Affiliation(s)
- Melissa J. Mann
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Chris Melendez-Suchi
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Hannah E. Vorndran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Maria Sukhoplyasova
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Ashley R. Flory
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Mary Carson Irvine
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Anuradha R. Iyer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | | | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Linda M. Hendershot
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Teresa M. Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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27
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Martínez-Andrade JM, Roberson RW, Riquelme M. A bird's-eye view of the endoplasmic reticulum in filamentous fungi. Microbiol Mol Biol Rev 2024; 88:e0002723. [PMID: 38372526 PMCID: PMC10966943 DOI: 10.1128/mmbr.00027-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2024] Open
Abstract
SUMMARYThe endoplasmic reticulum (ER) is one of the most extensive organelles in eukaryotic cells. It performs crucial roles in protein and lipid synthesis and Ca2+ homeostasis. Most information on ER types, functions, organization, and domains comes from studies in uninucleate animal, plant, and yeast cells. In contrast, there is limited information on the multinucleate cells of filamentous fungi, i.e., hyphae. We provide an analytical review of existing literature to categorize different types of ER described in filamentous fungi while emphasizing the research techniques and markers used. Additionally, we identify the knowledge gaps that need to be resolved better to understand the structure-function correlation of ER in filamentous fungi. Finally, advanced technologies that can provide breakthroughs in understanding the ER in filamentous fungi are discussed.
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Affiliation(s)
- Juan M. Martínez-Andrade
- Department of Microbiology, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico
| | | | - Meritxell Riquelme
- Department of Microbiology, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico
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28
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Crapart CC, Scott ZC, Konno T, Sharma A, Parutto P, Bailey DMD, Westrate LM, Avezov E, Koslover EF. Luminal transport through intact endoplasmic reticulum limits the magnitude of localized Ca 2+ signals. Proc Natl Acad Sci U S A 2024; 121:e2312172121. [PMID: 38502705 PMCID: PMC10990089 DOI: 10.1073/pnas.2312172121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 02/09/2024] [Indexed: 03/21/2024] Open
Abstract
The endoplasmic reticulum (ER) forms an interconnected network of tubules stretching throughout the cell. Understanding how ER functionality relies on its structural organization is crucial for elucidating cellular vulnerability to ER perturbations, which have been implicated in several neuronal pathologies. One of the key functions of the ER is enabling Ca[Formula: see text] signaling by storing large quantities of this ion and releasing it into the cytoplasm in a spatiotemporally controlled manner. Through a combination of physical modeling and live-cell imaging, we demonstrate that alterations in ER shape significantly impact its ability to support efficient local Ca[Formula: see text] releases, due to hindered transport of luminal content within the ER. Our model reveals that rapid Ca[Formula: see text] release necessitates mobile luminal buffer proteins with moderate binding strength, moving through a well-connected network of ER tubules. These findings provide insight into the functional advantages of normal ER architecture, emphasizing its importance as a kinetically efficient intracellular Ca[Formula: see text] delivery system.
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Affiliation(s)
- Cécile C. Crapart
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | | | - Tasuku Konno
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - Aman Sharma
- Department of Physics, University of California, San Diego, La Jolla, CA92130
| | - Pierre Parutto
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - David M. D. Bailey
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - Laura M. Westrate
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, MI49546
| | - Edward Avezov
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - Elena F. Koslover
- Department of Physics, University of California, San Diego, La Jolla, CA92130
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29
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Hoyer MJ, Capitanio C, Smith IR, Paoli JC, Bieber A, Jiang Y, Paulo JA, Gonzalez-Lozano MA, Baumeister W, Wilfling F, Schulman BA, Harper JW. Combinatorial selective ER-phagy remodels the ER during neurogenesis. Nat Cell Biol 2024; 26:378-392. [PMID: 38429475 PMCID: PMC10940164 DOI: 10.1038/s41556-024-01356-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 01/11/2024] [Indexed: 03/03/2024]
Abstract
The endoplasmic reticulum (ER) employs a diverse proteome landscape to orchestrate many cellular functions, ranging from protein and lipid synthesis to calcium ion flux and inter-organelle communication. A case in point concerns the process of neurogenesis, where a refined tubular ER network is assembled via ER shaping proteins into the newly formed neuronal projections to create highly polarized dendrites and axons. Previous studies have suggested a role for autophagy in ER remodelling, as autophagy-deficient neurons in vivo display axonal ER accumulation within synaptic boutons, and the membrane-embedded ER-phagy receptor FAM134B has been genetically linked with human sensory and autonomic neuropathy. However, our understanding of the mechanisms underlying selective removal of the ER and the role of individual ER-phagy receptors is limited. Here we combine a genetically tractable induced neuron (iNeuron) system for monitoring ER remodelling during in vitro differentiation with proteomic and computational tools to create a quantitative landscape of ER proteome remodelling via selective autophagy. Through analysis of single and combinatorial ER-phagy receptor mutants, we delineate the extent to which each receptor contributes to both the magnitude and selectivity of ER protein clearance. We define specific subsets of ER membrane or lumenal proteins as preferred clients for distinct receptors. Using spatial sensors and flux reporters, we demonstrate receptor-specific autophagic capture of ER in axons, and directly visualize tubular ER membranes within autophagosomes in neuronal projections by cryo-electron tomography. This molecular inventory of ER proteome remodelling and versatile genetic toolkit provide a quantitative framework for understanding the contributions of individual ER-phagy receptors for reshaping ER during cell state transitions.
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Affiliation(s)
- Melissa J Hoyer
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Cristina Capitanio
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Ian R Smith
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Velia Therapeutics, San Diego, CA, USA
| | - Julia C Paoli
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Anna Bieber
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Yizhi Jiang
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Miguel A Gonzalez-Lozano
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Wolfgang Baumeister
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Florian Wilfling
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
- Mechanisms of Cellular Quality Control, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Brenda A Schulman
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - J Wade Harper
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA.
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30
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Jang W, Haucke V. ER remodeling via lipid metabolism. Trends Cell Biol 2024:S0962-8924(24)00023-0. [PMID: 38395735 DOI: 10.1016/j.tcb.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 12/22/2023] [Accepted: 01/24/2024] [Indexed: 02/25/2024]
Abstract
Unlike most other organelles found in multiple copies, the endoplasmic reticulum (ER) is a unique singular organelle within eukaryotic cells. Despite its continuous membrane structure, encompassing more than half of the cellular endomembrane system, the ER is subdivided into specialized sub-compartments, including morphological, membrane contact site (MCS), and de novo organelle biogenesis domains. In this review, we discuss recent emerging evidence indicating that, in response to nutrient stress, cells undergo a reorganization of these sub-compartmental ER domains through two main mechanisms: non-destructive remodeling of morphological ER domains via regulation of MCS and organelle hitchhiking, and destructive remodeling of specialized domains by ER-phagy. We further highlight and propose a critical role of membrane lipid metabolism in this ER remodeling during starvation.
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Affiliation(s)
- Wonyul Jang
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany; Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
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31
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Zhang W, Zhang Z, Xiang Y, Gu DD, Chen J, Chen Y, Zhai S, Liu Y, Jiang T, Liu C, He B, Yan M, Wang Z, Xu J, Cao YL, Deng B, Zeng D, Lei J, Zhuo J, Lei X, Long Z, Jin B, Chen T, Li D, Shen Y, Hu J, Gao S, Liu Q. Aurora kinase A-mediated phosphorylation triggers structural alteration of Rab1A to enhance ER complexity during mitosis. Nat Struct Mol Biol 2024; 31:219-231. [PMID: 38177680 DOI: 10.1038/s41594-023-01165-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 10/26/2023] [Indexed: 01/06/2024]
Abstract
Morphological rearrangement of the endoplasmic reticulum (ER) is critical for metazoan mitosis. Yet, how the ER is remodeled by the mitotic signaling remains unclear. Here, we report that mitotic Aurora kinase A (AURKA) employs a small GTPase, Rab1A, to direct ER remodeling. During mitosis, AURKA phosphorylates Rab1A at Thr75. Structural analysis demonstrates that Thr75 phosphorylation renders Rab1A in a constantly active state by preventing interaction with GDP-dissociation inhibitor (GDI). Activated Rab1A is retained on the ER and induces the oligomerization of ER-shaping protein RTNs and REEPs, eventually triggering an increase of ER complexity. In various models, from Caenorhabditis elegans and Drosophila to mammals, inhibition of Rab1AThr75 phosphorylation by genetic modifications disrupts ER remodeling. Thus, our study reveals an evolutionarily conserved mechanism explaining how mitotic kinase controls ER remodeling and uncovers a critical function of Rab GTPases in metaphase.
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Affiliation(s)
- Wei Zhang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
- Department of Clinical Immunology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zijian Zhang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Yun Xiang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Dong-Dong Gu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Jinna Chen
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Yifan Chen
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Shixian Zhai
- MOE Key Laboratory of Laser Life Science and College of Biophotonics, South China Normal University, Guangzhou, China
| | - Yong Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Tao Jiang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Chong Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bin He
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Min Yan
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Zifeng Wang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Jie Xu
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Yu-Lu Cao
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Bing Deng
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Deshun Zeng
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Jie Lei
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Junxiao Zhuo
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Xinxing Lei
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Zijie Long
- Department of Hematology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Institute of Hematology, Sun Yat-sen University, Guangzhou, China
| | - Bilian Jin
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Tongsheng Chen
- MOE Key Laboratory of Laser Life Science and College of Biophotonics, South China Normal University, Guangzhou, China
| | - Dong Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yidong Shen
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Song Gao
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China.
| | - Quentin Liu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China.
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China.
- Institute of Hematology, Sun Yat-sen University, Guangzhou, China.
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32
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Paul B, Merta H, Ugrankar-Banerjee R, Hensley M, Tran S, Dias do Vale G, McDonald JG, Farber SA, Henne WM. Paraoxonase-like APMAP maintains endoplasmic reticulum-associated lipid and lipoprotein homeostasis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.26.577049. [PMID: 38328083 PMCID: PMC10849633 DOI: 10.1101/2024.01.26.577049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Oxidative stress perturbs lipid homeostasis and contributes to metabolic diseases. Though ignored compared to mitochondrial oxidation, the endoplasmic reticulum (ER) generates reactive oxygen species requiring antioxidant quality control. Using multi-organismal profiling featuring Drosophila, zebrafish, and mammalian cells, here we characterize the paraoxonase-like APMAP as an ER-localized protein that promotes redox and lipid homeostasis and lipoprotein maturation. APMAP-depleted mammalian cells exhibit defective ER morphology, elevated ER and oxidative stress, lipid droplet accumulation, and perturbed ApoB-lipoprotein homeostasis. Critically, APMAP loss is rescued with chemical antioxidant NAC. Organismal APMAP depletion in Drosophila perturbs fat and lipoprotein homeostasis, and zebrafish display increased vascular ApoB-containing lipoproteins, particles that are atherogenic in mammals. Lipidomics reveals altered polyunsaturated phospholipids and increased ceramides upon APMAP loss, which perturbs ApoB-lipoprotein maturation. These ApoB-associated defects are rescued by inhibiting ceramide synthesis. Collectively, we propose APMAP is an ER-localized antioxidant that promotes lipid and lipoprotein homeostasis.
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Affiliation(s)
- Blessy Paul
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390
| | - Holly Merta
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390
| | | | - Monica Hensley
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218
| | - Son Tran
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390
| | - Goncalo Dias do Vale
- Department of Molecular Genetics, UT Southwestern Medical Center, Dallas, TX 75390
| | - Jeffrey G McDonald
- Department of Molecular Genetics, UT Southwestern Medical Center, Dallas, TX 75390
| | - Steven A Farber
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390
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Merta H, Isogai T, Paul B, Danuser G, Henne WM. Spatial proteomics of ER tubules reveals CLMN, an ER-actin tether at focal adhesions that promotes cell migration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.24.577043. [PMID: 38328045 PMCID: PMC10849733 DOI: 10.1101/2024.01.24.577043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The endoplasmic reticulum (ER) is structurally and functionally diverse, yet how its functions are organized within morphological subdomains is incompletely understood. Utilizing TurboID-based proximity labeling and CRISPR knock-in technologies, here we map the proteomic landscape of the human ER and nuclear envelope. Spatial proteomics reveals enrichments of proteins into ER tubules, sheets, and nuclear envelope. We uncover an ER-enriched actin-binding protein, Calmin (CLMN), and define it as an ER-actin tether that localizes to focal adhesions adjacent to ER tubules. CLMN depletion perturbs focal adhesion disassembly, actin dynamics, and cell movement. Mechanistically, CLMN-depleted cells also exhibit defects in calcium signaling near ER-actin interfaces, suggesting CLMN promotes calcium signaling near adhesions to facilitate their disassembly. Collectively, we map the sub-organelle proteome landscape of the ER, identify CLMN as an ER-actin tether, and describe a non-canonical mechanism by which ER tubules engage actin to regulate cell migration.
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Affiliation(s)
- Holly Merta
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - Tadamoto Isogai
- Lyda Hill Department of Bioinformatics and Cecil H. and Ida Green Center for Systems Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - Blessy Paul
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - Gaudenz Danuser
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
- Lyda Hill Department of Bioinformatics and Cecil H. and Ida Green Center for Systems Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
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Hoyer MJ, Capitanio C, Smith IR, Paoli JC, Bieber A, Jiang Y, Paulo JA, Gonzalez-Lozano MA, Baumeister W, Wilfling F, Schulman BA, Harper JW. Combinatorial selective ER-phagy remodels the ER during neurogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546565. [PMID: 37425907 PMCID: PMC10326971 DOI: 10.1101/2023.06.26.546565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
The endoplasmic reticulum (ER) employs a diverse proteome landscape to orchestrate many cellular functions ranging from protein and lipid synthesis to calcium ion flux and inter-organelle communication. A case in point concerns the process of neurogenesis: a refined tubular ER network is assembled via ER shaping proteins into the newly formed neuronal projections to create highly polarized dendrites and axons. Previous studies have suggested a role for autophagy in ER remodeling, as autophagy-deficient neurons in vivo display axonal ER accumulation within synaptic boutons, and the membrane-embedded ER-phagy receptor FAM134B has been genetically linked with human sensory and autonomic neuropathy. However, our understanding of the mechanisms underlying selective removal of ER and the role of individual ER-phagy receptors is limited. Here, we combine a genetically tractable induced neuron (iNeuron) system for monitoring ER remodeling during in vitro differentiation with proteomic and computational tools to create a quantitative landscape of ER proteome remodeling via selective autophagy. Through analysis of single and combinatorial ER-phagy receptor mutants, we delineate the extent to which each receptor contributes to both magnitude and selectivity of ER protein clearance. We define specific subsets of ER membrane or lumenal proteins as preferred clients for distinct receptors. Using spatial sensors and flux reporters, we demonstrate receptor-specific autophagic capture of ER in axons, and directly visualize tubular ER membranes within autophagosomes in neuronal projections by cryo-electron tomography. This molecular inventory of ER proteome remodeling and versatile genetic toolkit provides a quantitative framework for understanding contributions of individual ER-phagy receptors for reshaping ER during cell state transitions.
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Gruber L, Jobst M, Kiss E, Karasová M, Englinger B, Berger W, Del Favero G. Intracellular remodeling associated with endoplasmic reticulum stress modifies biomechanical compliance of bladder cells. Cell Commun Signal 2023; 21:307. [PMID: 37904178 PMCID: PMC10614373 DOI: 10.1186/s12964-023-01295-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/23/2023] [Indexed: 11/01/2023] Open
Abstract
Bladder cells face a challenging biophysical environment: mechanical cues originating from urine flow and regular contraction to enable the filling voiding of the organ. To ensure functional adaption, bladder cells rely on high biomechanical compliance, nevertheless aging or chronic pathological conditions can modify this plasticity. Obviously the cytoskeletal network plays an essential role, however the contribution of other, closely entangled, intracellular organelles is currently underappreciated. The endoplasmic reticulum (ER) lies at a crucial crossroads, connected to both nucleus and cytoskeleton. Yet, its role in the maintenance of cell mechanical stability is less investigated. To start exploring these aspects, T24 bladder cancer cells were treated with the ER stress inducers brefeldin A (10-40nM BFA, 24 h) and thapsigargin (0.1-100nM TG, 24 h). Without impairment of cell motility and viability, BFA and TG triggered a significant subcellular redistribution of the ER; this was associated with a rearrangement of actin cytoskeleton. Additional inhibition of actin polymerization with cytochalasin D (100nM CytD) contributed to the spread of the ER toward cell periphery, and was accompanied by an increase of cellular stiffness (Young´s modulus) in the cytoplasmic compartment. Shrinking of the ER toward the nucleus (100nM TG, 2 h) was related to an increased stiffness in the nuclear and perinuclear areas. A similar short-term response profile was observed also in normal human primary bladder fibroblasts. In sum, the ER and its subcellular rearrangement seem to contribute to the mechanical properties of bladder cells opening new perspectives in the study of the related stress signaling cascades. Video Abstract.
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Affiliation(s)
- Livia Gruber
- Department of Food Chemistry and Toxicology, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria
| | - Maximilian Jobst
- Department of Food Chemistry and Toxicology, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria
- Core Facility Multimodal Imaging, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria
- University of Vienna, Vienna Doctoral School in Chemistry (DoSChem), Währinger Str. 42, Vienna, 1090, Austria
| | - Endre Kiss
- Core Facility Multimodal Imaging, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria
| | - Martina Karasová
- Department of Food Chemistry and Toxicology, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria
- Core Facility Multimodal Imaging, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria
| | - Bernhard Englinger
- Department of Urology, Comprehensive Cancer Center, Medical University of Vienna, Vienna, 1090, Austria
- Center for Cancer Research and Comprehensive Cancer Center, Medical University Vienna, Vienna, 1090, Austria
| | - Walter Berger
- Center for Cancer Research and Comprehensive Cancer Center, Medical University Vienna, Vienna, 1090, Austria
| | - Giorgia Del Favero
- Department of Food Chemistry and Toxicology, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria.
- Core Facility Multimodal Imaging, University of Vienna Faculty of Chemistry, Währinger Str. 38-40, Vienna, 1090, Austria.
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Mann MJ, Melendez-Suchi C, Sukhoplyasova M, Flory AR, Carson Irvine M, Iyer AR, Vorndran H, Guerriero CJ, Brodsky JL, Hendershot LM, Buck TM. Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum functions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.19.563191. [PMID: 37905119 PMCID: PMC10614942 DOI: 10.1101/2023.10.19.563191] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
GRP170, a product of the Hyou1 gene, is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds non-native proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of embryonic fibroblasts from mice in which LoxP sites were engineered in the Hyou1 loci ( Hyou1 LoxP/LoxP ). A doxycycline-regulated Cre recombinase was also stably introduced into these cells. Induction of Cre resulted in excision of Hyou1 and depletion of Grp170 protein, culminating in apoptotic cell death. As Grp170 levels fell we observed increased steady-state binding of BiP to a client, slowed degradation of a misfolded BiP substrate, and BiP accumulation in NP40-insoluble fractions. Consistent with disrupted BiP functions, we observed reactivation of BiP storage pools and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and insights into mutations in the Hyou1 locus and human disease.
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Fu Y, Sacco O, DeBitetto E, Kanshin E, Ueberheide B, Sfeir A. Mitochondrial DNA breaks activate an integrated stress response to reestablish homeostasis. Mol Cell 2023; 83:3740-3753.e9. [PMID: 37832546 PMCID: PMC11229056 DOI: 10.1016/j.molcel.2023.09.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 08/10/2023] [Accepted: 09/21/2023] [Indexed: 10/15/2023]
Abstract
Mitochondrial DNA double-strand breaks (mtDSBs) lead to the degradation of circular genomes and a reduction in copy number; yet, the cellular response in human cells remains elusive. Here, using mitochondrial-targeted restriction enzymes, we show that a subset of cells with mtDSBs exhibited defective mitochondrial protein import, reduced respiratory complexes, and loss of membrane potential. Electron microscopy confirmed the altered mitochondrial membrane and cristae ultrastructure. Intriguingly, mtDSBs triggered the integrated stress response (ISR) via the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) by DELE1 and heme-regulated eIF2α kinase (HRI). When ISR was inhibited, the cells experienced intensified mitochondrial defects and slower mtDNA recovery post-breakage. Lastly, through proteomics, we identified ATAD3A-a membrane-bound protein interacting with nucleoids-as potentially pivotal in relaying signals from impaired genomes to the inner mitochondrial membrane. In summary, our study delineates the cascade connecting damaged mitochondrial genomes to the cytoplasm and highlights the significance of the ISR in maintaining mitochondrial homeostasis amid genome instability.
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Affiliation(s)
- Yi Fu
- Skirball Institute of Biomolecular Medicine, Cell Biology Department, NYU School of Medicine, New York, NY 10016, USA; Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Olivia Sacco
- Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Emily DeBitetto
- Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Evgeny Kanshin
- Proteomics Laboratory, NYU School of Medicine, New York, NY 10016, USA; Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY 10016, USA
| | - Beatrix Ueberheide
- Proteomics Laboratory, NYU School of Medicine, New York, NY 10016, USA; Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY 10016, USA; Department of Neurology, NYU School of Medicine, New York, NY 10016, USA; Perlmutter Cancer Center, NYU School of Medicine, New York, NY 10016, USA
| | - Agnel Sfeir
- Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
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38
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Fuentes LA, Marin Z, Tyson J, Baddeley D, Bewersdorf J. The nanoscale organization of reticulon 4 shapes local endoplasmic reticulum structure in situ. J Cell Biol 2023; 222:e202301112. [PMID: 37516910 PMCID: PMC10373298 DOI: 10.1083/jcb.202301112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 05/31/2023] [Accepted: 07/06/2023] [Indexed: 07/31/2023] Open
Abstract
The endoplasmic reticulum's (ER's) structure is directly linked to the many functions of the ER, but its formation is not fully understood. We investigate how the ER-membrane curving protein reticulon 4 (Rtn4) localizes to and organizes in the membrane and how that affects the local ER structure. We show a strong correlation between the local Rtn4 density and the local ER membrane curvature. Our data further reveal that the typical ER tubule possesses an elliptical cross-section with Rtn4 enriched at either end of the major axis. Rtn4 oligomers are linear shaped, contain about five copies of the protein, and preferentially orient parallel to the tubule axis. Our observations support a mechanism in which oligomerization leads to an increase of the local Rtn4 concentration with each molecule, increasing membrane curvature through a hairpin wedging mechanism. This quantitative analysis of Rtn4 and its effects on the ER membrane result in a new model of tubule shape as it relates to Rtn4.
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Affiliation(s)
- Lukas A. Fuentes
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Zach Marin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Jonathan Tyson
- Department of Chemistry, Yale University, New Haven, CT, USA
| | - David Baddeley
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Department of Physics, Yale University, New Haven, CT, USA
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39
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Jackson KG, Way GW, Zeng J, Lipp MK, Zhou H. The Dynamic Role of Endoplasmic Reticulum Stress in Chronic Liver Disease. THE AMERICAN JOURNAL OF PATHOLOGY 2023; 193:1389-1399. [PMID: 37028592 PMCID: PMC10548273 DOI: 10.1016/j.ajpath.2023.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/10/2023] [Accepted: 03/27/2023] [Indexed: 04/08/2023]
Abstract
Chronic liver disease (CLD) is a major worldwide public health threat, with an estimated prevalence of 1.5 billion individuals with CLD in 2020. Chronic activation of endoplasmic reticulum (ER) stress-related pathways is recognized as substantially contributing to the pathologic progression of CLD. The ER is an intracellular organelle that folds proteins into their correct three-dimensional shapes. ER-associated enzymes and chaperone proteins highly regulate this process. Perturbations in protein folding lead to misfolded or unfolded protein accumulation in the ER lumen, resulting in ER stress and concomitant activation of the unfolded protein response (UPR). The adaptive UPR is a set of signal transduction pathways evolved in mammalian cells that attempts to reestablish ER protein homeostasis by reducing protein load and increasing ER-associated degradation. However, maladaptive UPR responses in CLD occur due to prolonged UPR activation, leading to concomitant inflammation and cell death. This review assesses the current understanding of the cellular and molecular mechanisms that regulate ER stress and the UPR in the progression of various liver diseases and the potential pharmacologic and biological interventions that target the UPR.
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Affiliation(s)
- Kaitlyn G Jackson
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, Virginia
| | - Grayson W Way
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, Virginia; Center for Clinical and Translational Research, Virginia Commonwealth University School of Medicine, Richmond, Virginia
| | - Jing Zeng
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, Virginia; Department of Gastroenterology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Marissa K Lipp
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, Virginia
| | - Huiping Zhou
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, Virginia; Central Virginia Veterans Healthcare System, Richmond, Virginia.
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Cremer T, Voortman LM, Bos E, Jongsma MLM, ter Haar LR, Akkermans JJLL, Talavera Ormeño CMP, Wijdeven RHM, de Vries J, Kim RQ, Janssen GMC, van Veelen PA, Koning RI, Neefjes J, Berlin I. RNF26 binds perinuclear vimentin filaments to integrate ER and endolysosomal responses to proteotoxic stress. EMBO J 2023; 42:e111252. [PMID: 37519262 PMCID: PMC10505911 DOI: 10.15252/embj.2022111252] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 06/28/2023] [Accepted: 07/03/2023] [Indexed: 08/01/2023] Open
Abstract
Proteotoxic stress causes profound endoplasmic reticulum (ER) membrane remodeling into a perinuclear quality control compartment (ERQC) for the degradation of misfolded proteins. Subsequent return to homeostasis involves clearance of the ERQC by endolysosomes. However, the factors that control perinuclear ER integrity and dynamics remain unclear. Here, we identify vimentin intermediate filaments as perinuclear anchors for the ER and endolysosomes. We show that perinuclear vimentin filaments engage the ER-embedded RING finger protein 26 (RNF26) at the C-terminus of its RING domain. This restricts RNF26 to perinuclear ER subdomains and enables the corresponding spatial retention of endolysosomes through RNF26-mediated membrane contact sites (MCS). We find that both RNF26 and vimentin are required for the perinuclear coalescence of the ERQC and its juxtaposition with proteolytic compartments, which facilitates efficient recovery from ER stress via the Sec62-mediated ER-phagy pathway. Collectively, our findings reveal a scaffolding mechanism that underpins the spatiotemporal integration of organelles during cellular proteostasis.
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Affiliation(s)
- Tom Cremer
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
- Oncode Institute, Leiden University Medical CenterLeidenThe Netherlands
| | - Lenard M Voortman
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Erik Bos
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Marlieke LM Jongsma
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
- Oncode Institute, Leiden University Medical CenterLeidenThe Netherlands
| | - Laurens R ter Haar
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Jimmy JLL Akkermans
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
- Oncode Institute, Leiden University Medical CenterLeidenThe Netherlands
| | - Cami MP Talavera Ormeño
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Ruud HM Wijdeven
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
- Oncode Institute, Leiden University Medical CenterLeidenThe Netherlands
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam NeuroscienceAmsterdam University Medical CenterAmsterdamThe Netherlands
| | - Jelle de Vries
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Robbert Q Kim
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - George MC Janssen
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Peter A van Veelen
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Roman I Koning
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Jacques Neefjes
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
- Oncode Institute, Leiden University Medical CenterLeidenThe Netherlands
| | - Ilana Berlin
- Department of Cell and Chemical BiologyLeiden University Medical CenterLeidenThe Netherlands
- Oncode Institute, Leiden University Medical CenterLeidenThe Netherlands
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Gandhimathi R, Pinotsi D, Köhler M, Mansfeld J, Ashiono C, Kleele T, Pawar S, Kutay U. Super-resolution microscopy reveals focal organization of ER-associated Y-complexes in mitosis. EMBO Rep 2023; 24:e56766. [PMID: 37469276 PMCID: PMC10481662 DOI: 10.15252/embr.202356766] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 07/03/2023] [Accepted: 07/03/2023] [Indexed: 07/21/2023] Open
Abstract
During mitotic entry of vertebrate cells, nuclear pore complexes (NPCs) are rapidly disintegrated. NPC disassembly is initiated by hyperphosphorylation of linker nucleoporins (Nups), which leads to the dissociation of FG repeat Nups and relaxation of the nuclear permeability barrier. However, less is known about disintegration of the huge nuclear and cytoplasmic rings, which are formed by annular assemblies of Y-complexes that are dissociated from NPCs as intact units. Surprisingly, we observe that Y-complex Nups display slower dissociation kinetics compared with other Nups during in vitro NPC disassembly, indicating a mechanistic difference in the disintegration of Y-based rings. Intriguingly, biochemical experiments reveal that a fraction of Y-complexes remains associated with mitotic ER membranes, supporting recent microscopic observations. Visualization of mitotic Y-complexes by super-resolution microscopy demonstrates that they form two classes of higher order assemblies: large clusters at kinetochores and small, focal ER-associated assemblies. These, however, lack features qualifying them as persisting ring-shaped subassemblies previously proposed to serve as structural templates for NPC reassembly during mitotic exit, which helps to refine current models of nuclear reassembly.
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Affiliation(s)
- Rojapriyadharshini Gandhimathi
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
- Molecular Life Sciences Ph.D. ProgramZurichSwitzerland
| | | | - Mario Köhler
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
| | - Jörg Mansfeld
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
- The Institute of Cancer ResearchLondonUK
| | - Caroline Ashiono
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
| | - Tatjana Kleele
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
| | - Sumit Pawar
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
- Present address:
Myllia BiotechnologyViennaAustria
| | - Ulrike Kutay
- Department of Biology, Institute of BiochemistryETH ZurichZurichSwitzerland
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Venkatraman K, Lee CT, Garcia GC, Mahapatra A, Milshteyn D, Perkins G, Kim KY, Pasolli HA, Phan S, Lippincott-Schwartz J, Ellisman MH, Rangamani P, Budin I. Cristae formation is a mechanical buckling event controlled by the inner membrane lipidome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.13.532310. [PMID: 36993370 PMCID: PMC10054968 DOI: 10.1101/2023.03.13.532310] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Cristae are high curvature structures in the inner mitochondrial membrane (IMM) that are crucial for ATP production. While cristae-shaping proteins have been defined, analogous mechanisms for lipids have yet to be elucidated. Here we combine experimental lipidome dissection with multi-scale modeling to investigate how lipid interactions dictate IMM morphology and ATP generation. When modulating phospholipid (PL) saturation in engineered yeast strains, we observed a surprisingly abrupt breakpoint in IMM topology driven by a continuous loss of ATP synthase organization at cristae ridges. We found that cardiolipin (CL) specifically buffers the IMM against curvature loss, an effect that is independent of ATP synthase dimerization. To explain this interaction, we developed a continuum model for cristae tubule formation that integrates both lipid and protein-mediated curvatures. The model highlighted a snapthrough instability, which drives IMM collapse upon small changes in membrane properties. We also showed that CL is essential in low oxygen conditions that promote PL saturation. These results demonstrate that the mechanical function of CL is dependent on the surrounding lipid and protein components of the IMM.
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Affiliation(s)
- Kailash Venkatraman
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093
| | - Christopher T Lee
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
| | - Guadalupe C Garcia
- Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla CA 92097
| | - Arijit Mahapatra
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
| | - Daniel Milshteyn
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093
| | - Guy Perkins
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093
| | - Keun-Young Kim
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093
| | - H Amalia Pasolli
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn VA 20147
| | - Sebastien Phan
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093
| | | | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093
| | - Itay Budin
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093
- Lead contact
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43
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Cheng LC, Zhang X, Baboo S, Nguyen JA, Martinez-Bartolomé S, Loose E, Diedrich J, Yates JR, Gerace L. Comparative membrane proteomics reveals diverse cell regulators concentrated at the nuclear envelope. Life Sci Alliance 2023; 6:e202301998. [PMID: 37433644 PMCID: PMC10336727 DOI: 10.26508/lsa.202301998] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 06/23/2023] [Accepted: 06/26/2023] [Indexed: 07/13/2023] Open
Abstract
The nuclear envelope (NE) is a subdomain of the ER with prominent roles in nuclear organization, which are largely mediated by its distinctive protein composition. We developed methods to reveal low-abundance transmembrane (TM) proteins concentrated at the NE relative to the peripheral ER. Using label-free proteomics that compared isolated NEs with cytoplasmic membranes, we first identified proteins with apparent NE enrichment. In subsequent authentication, ectopically expressed candidates were analyzed by immunofluorescence microscopy to quantify their targeting to the NE in cultured cells. Ten proteins from a validation set were found to associate preferentially with the NE, including oxidoreductases, enzymes for lipid biosynthesis, and regulators of cell growth and survival. We determined that one of the validated candidates, the palmitoyltransferase Zdhhc6, modifies the NE oxidoreductase Tmx4 and thereby modulates its NE levels. This provides a functional rationale for the NE concentration of Zdhhc6. Overall, our methodology has revealed a group of previously unrecognized proteins concentrated at the NE and additional candidates. Future analysis of these can potentially unveil new mechanistic pathways associated with the NE.
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Affiliation(s)
- Li-Chun Cheng
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Xi Zhang
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Sabyasachi Baboo
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Julie A Nguyen
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | | | - Esther Loose
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Jolene Diedrich
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - John R Yates
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Larry Gerace
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
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44
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Parkkinen I, Their A, Asghar MY, Sree S, Jokitalo E, Airavaara M. Pharmacological Regulation of Endoplasmic Reticulum Structure and Calcium Dynamics: Importance for Neurodegenerative Diseases. Pharmacol Rev 2023; 75:959-978. [PMID: 37127349 DOI: 10.1124/pharmrev.122.000701] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 03/27/2023] [Accepted: 04/04/2023] [Indexed: 05/03/2023] Open
Abstract
The endoplasmic reticulum (ER) is the largest organelle of the cell, composed of a continuous network of sheets and tubules, and is involved in protein, calcium (Ca2+), and lipid homeostasis. In neurons, the ER extends throughout the cell, both somal and axodendritic compartments, and is highly important for neuronal functions. A third of the proteome of a cell, secreted and membrane-bound proteins, are processed within the ER lumen and most of these proteins are vital for neuronal activity. The brain itself is high in lipid content, and many structural lipids are produced, in part, by the ER. Cholesterol and steroid synthesis are strictly regulated in the ER of the blood-brain barrier protected brain cells. The high Ca2+ level in the ER lumen and low cytosolic concentration is needed for Ca2+-based intracellular signaling, for synaptic signaling and Ca2+ waves, and for preparing proteins for correct folding in the presence of high Ca2+ concentrations to cope with the high concentrations of extracellular milieu. Particularly, ER Ca2+ is controlled in axodendritic areas for proper neurito- and synaptogenesis and synaptic plasticity and remodeling. In this review, we cover the physiologic functions of the neuronal ER and discuss it in context of common neurodegenerative diseases, focusing on pharmacological regulation of ER Ca2+ Furthermore, we postulate that heterogeneity of the ER, its protein folding capacity, and ensuring Ca2+ regulation are crucial factors for the aging and selective vulnerability of neurons in various neurodegenerative diseases. SIGNIFICANCE STATEMENT: Endoplasmic reticulum (ER) Ca2+ regulators are promising therapeutic targets for degenerative diseases for which efficacious drug therapies do not exist. The use of pharmacological probes targeting maintenance and restoration of ER Ca2+ can provide restoration of protein homeostasis (e.g., folding of complex plasma membrane signaling receptors) and slow down the degeneration process of neurons.
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Affiliation(s)
- Ilmari Parkkinen
- Neuroscience Center (I.P., A.T., M.A.), Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy (I.P., M.A.), Cell and Tissue Dynamics Research Program, Institute of Biotechnology, Helsinki Institute of Life Sciences (M.Y.A., S.S., E.J.), and Electron Microscopy Unit, Institute of Biotechnology, Helsinki Institute of Life Sciences (E.J.), University of Helsinki, Helsinki, Finland
| | - Anna Their
- Neuroscience Center (I.P., A.T., M.A.), Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy (I.P., M.A.), Cell and Tissue Dynamics Research Program, Institute of Biotechnology, Helsinki Institute of Life Sciences (M.Y.A., S.S., E.J.), and Electron Microscopy Unit, Institute of Biotechnology, Helsinki Institute of Life Sciences (E.J.), University of Helsinki, Helsinki, Finland
| | - Muhammad Yasir Asghar
- Neuroscience Center (I.P., A.T., M.A.), Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy (I.P., M.A.), Cell and Tissue Dynamics Research Program, Institute of Biotechnology, Helsinki Institute of Life Sciences (M.Y.A., S.S., E.J.), and Electron Microscopy Unit, Institute of Biotechnology, Helsinki Institute of Life Sciences (E.J.), University of Helsinki, Helsinki, Finland
| | - Sreesha Sree
- Neuroscience Center (I.P., A.T., M.A.), Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy (I.P., M.A.), Cell and Tissue Dynamics Research Program, Institute of Biotechnology, Helsinki Institute of Life Sciences (M.Y.A., S.S., E.J.), and Electron Microscopy Unit, Institute of Biotechnology, Helsinki Institute of Life Sciences (E.J.), University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Neuroscience Center (I.P., A.T., M.A.), Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy (I.P., M.A.), Cell and Tissue Dynamics Research Program, Institute of Biotechnology, Helsinki Institute of Life Sciences (M.Y.A., S.S., E.J.), and Electron Microscopy Unit, Institute of Biotechnology, Helsinki Institute of Life Sciences (E.J.), University of Helsinki, Helsinki, Finland
| | - Mikko Airavaara
- Neuroscience Center (I.P., A.T., M.A.), Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy (I.P., M.A.), Cell and Tissue Dynamics Research Program, Institute of Biotechnology, Helsinki Institute of Life Sciences (M.Y.A., S.S., E.J.), and Electron Microscopy Unit, Institute of Biotechnology, Helsinki Institute of Life Sciences (E.J.), University of Helsinki, Helsinki, Finland
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45
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Wang N, Shibata Y, Paulo JA, Gygi SP, Rapoport TA. A conserved membrane curvature-generating protein is crucial for autophagosome formation in fission yeast. Nat Commun 2023; 14:4765. [PMID: 37553386 PMCID: PMC10409813 DOI: 10.1038/s41467-023-40530-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 07/26/2023] [Indexed: 08/10/2023] Open
Abstract
Organelles are shaped by curvature-generating proteins, which include the reticulons and REEPs that are involved in forming the endoplasmic reticulum (ER). A conserved REEP subfamily differs from the ER-shaping REEPs in abundance and membrane topology and has unidentified functions. Here, we show that Rop1, the single member of this family in the fission yeast Schizosacharomyces pombe, is crucial for the macroautophagy of organelles and cytosolic proteins. Rop1 is needed for the formation of phagophores, cup-like structures consisting of two closely apposed membrane sheets that encapsulate cargo. It is recruited at early stages to phagophores and is required for their maturation into autophagosomes. Rop1 function relies on its ability to generate high membrane curvature and on its colocalization with the autophagy component Atg2 that is thought to reside at the phagophore rim. We propose that Rop1 facilitates the formation and growth of the double-membrane structure of the autophagosome.
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Affiliation(s)
- Ning Wang
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115, USA
| | - Yoko Shibata
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115, USA
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115, USA
| | - Tom A Rapoport
- Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA, 02115, USA.
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46
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Scott ZC, Koning K, Vanderwerp M, Cohen L, Westrate LM, Koslover EF. Endoplasmic reticulum network heterogeneity guides diffusive transport and kinetics. Biophys J 2023; 122:3191-3205. [PMID: 37401053 PMCID: PMC10432226 DOI: 10.1016/j.bpj.2023.06.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 05/17/2023] [Accepted: 06/28/2023] [Indexed: 07/05/2023] Open
Abstract
The endoplasmic reticulum (ER) is a dynamic network of interconnected sheets and tubules that orchestrates the distribution of lipids, ions, and proteins throughout the cell. The impact of its complex, dynamic morphology on its function as an intracellular transport hub remains poorly understood. To elucidate the functional consequences of ER network structure and dynamics, we quantify how the heterogeneity of the peripheral ER in COS7 cells affects diffusive protein transport. In vivo imaging of photoactivated ER membrane proteins demonstrates their nonuniform spreading to adjacent regions, in a manner consistent with simulations of diffusing particles on extracted network structures. Using a minimal network model to represent tubule rearrangements, we demonstrate that ER network dynamics are sufficiently slow to have little effect on diffusive protein transport. Furthermore, stochastic simulations reveal a novel consequence of ER network heterogeneity: the existence of "hot spots" where sparse diffusive reactants are more likely to find one another. ER exit sites, specialized domains regulating cargo export from the ER, are shown to be disproportionately located in highly accessible regions, further from the outer boundary of the cell. Combining in vivo experiments with analytic calculations, quantitative image analysis, and computational modeling, we demonstrate how structure guides diffusive protein transport and reactions in the ER.
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Affiliation(s)
| | - Katherine Koning
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, Michigan
| | - Molly Vanderwerp
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, Michigan
| | | | - Laura M Westrate
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, Michigan
| | - Elena F Koslover
- Department of Physics, University of California, San Diego, La Jolla, California.
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47
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Hüsler D, Stauffer P, Hilbi H. Tapping lipid droplets: A rich fat diet of intracellular bacterial pathogens. Mol Microbiol 2023; 120:194-209. [PMID: 37429596 DOI: 10.1111/mmi.15120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 06/21/2023] [Accepted: 06/22/2023] [Indexed: 07/12/2023]
Abstract
Lipid droplets (LDs) are dynamic and versatile organelles present in most eukaryotic cells. LDs consist of a hydrophobic core of neutral lipids, a phospholipid monolayer coat, and a variety of associated proteins. LDs are formed at the endoplasmic reticulum and have diverse roles in lipid storage, energy metabolism, membrane trafficking, and cellular signaling. In addition to their physiological cellular functions, LDs have been implicated in the pathogenesis of several diseases, including metabolic disorders, cancer, and infections. A number of intracellular bacterial pathogens modulate and/or interact with LDs during host cell infection. Members of the genera Mycobacterium, Legionella, Coxiella, Chlamydia, and Salmonella exploit LDs as a source of intracellular nutrients and membrane components to establish their distinct intracellular replicative niches. In this review, we focus on the biogenesis, interactions, and functions of LDs, as well as on their role in lipid metabolism of intracellular bacterial pathogens.
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Affiliation(s)
- Dario Hüsler
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Pia Stauffer
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
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48
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Ilamathi HS, Benhammouda S, Lounas A, Al-Naemi K, Desrochers-Goyette J, Lines MA, Richard FJ, Vogel J, Germain M. Contact sites between endoplasmic reticulum sheets and mitochondria regulate mitochondrial DNA replication and segregation. iScience 2023; 26:107180. [PMID: 37534187 PMCID: PMC10391914 DOI: 10.1016/j.isci.2023.107180] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 05/16/2023] [Accepted: 06/15/2023] [Indexed: 08/04/2023] Open
Abstract
Mitochondria are multifaceted organelles crucial for cellular homeostasis that contain their own genome. Mitochondrial DNA (mtDNA) replication is a spatially regulated process essential for the maintenance of mitochondrial function, its defect causing mitochondrial diseases. mtDNA replication occurs at endoplasmic reticulum (ER)-mitochondria contact sites and is affected by mitochondrial dynamics: The absence of mitochondrial fusion is associated with mtDNA depletion whereas loss of mitochondrial fission causes the aggregation of mtDNA within abnormal structures termed mitobulbs. Here, we show that contact sites between mitochondria and ER sheets, the ER structure associated with protein synthesis, regulate mtDNA replication and distribution within mitochondrial networks. DRP1 loss or mutation leads to modified ER sheets and alters the interaction between ER sheets and mitochondria, disrupting RRBP1-SYNJ2BP interaction. Importantly, mtDNA distribution and replication were rescued by promoting ER sheets-mitochondria contact sites. Our work identifies the role of ER sheet-mitochondria contact sites in regulating mtDNA replication and distribution.
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Affiliation(s)
- Hema Saranya Ilamathi
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Réseau Intersectoriel de Recherche en Santé de l’Université du Québec (RISUQ), Laval, QC, Canada
| | - Sara Benhammouda
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Réseau Intersectoriel de Recherche en Santé de l’Université du Québec (RISUQ), Laval, QC, Canada
| | - Amel Lounas
- Centre de Recherche en Reproduction, Développement et Santé Intergénérationnelle (CRDSI), Département des Sciences Animales, Faculté des Sciences de L’agriculture et de L’alimentation, Université Laval, Québec, QC, Canada
| | - Khalid Al-Naemi
- Department of Biology, McGill University, Montréal, QC, Canada
| | - Justine Desrochers-Goyette
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Réseau Intersectoriel de Recherche en Santé de l’Université du Québec (RISUQ), Laval, QC, Canada
| | - Matthew A. Lines
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - François J. Richard
- Centre de Recherche en Reproduction, Développement et Santé Intergénérationnelle (CRDSI), Département des Sciences Animales, Faculté des Sciences de L’agriculture et de L’alimentation, Université Laval, Québec, QC, Canada
| | - Jackie Vogel
- Department of Biology, McGill University, Montréal, QC, Canada
| | - Marc Germain
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada
- Réseau Intersectoriel de Recherche en Santé de l’Université du Québec (RISUQ), Laval, QC, Canada
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49
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Williams JM, Chen YJ, Cho WJ, Tai AW, Tsai B. Reticulons promote formation of ER-derived double-membrane vesicles that facilitate SARS-CoV-2 replication. J Cell Biol 2023; 222:e202203060. [PMID: 37093123 PMCID: PMC10130743 DOI: 10.1083/jcb.202203060] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 08/24/2022] [Accepted: 04/06/2023] [Indexed: 04/25/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the etiologic agent for the global COVID-19 pandemic, triggers the formation of endoplasmic reticulum (ER)-derived replication organelles, including double-membrane vesicles (DMVs), in the host cell to support viral replication. Here, we clarify how SARS-CoV-2 hijacks host factors to construct the DMVs. We show that the ER morphogenic proteins reticulon-3 (RTN3) and RTN4 help drive DMV formation, enabling viral replication, which leads to productive infection. Different SARS-CoV-2 variants, including the delta variant, use the RTN-dependent pathway to promote infection. Mechanistically, our results reveal that the membrane-embedded reticulon homology domain (RHD) of the RTNs is sufficient to functionally support viral replication and physically engage NSP3 and NSP4, two viral non-structural membrane proteins known to induce DMV formation. Our findings thus identify the ER morphogenic RTN3 and RTN4 membrane proteins as host factors that help promote the biogenesis of SARS-CoV-2-induced DMVs, which can act as viral replication platforms.
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Affiliation(s)
- Jeffrey M. Williams
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Yu-Jie Chen
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Woo Jung Cho
- Biomedical Research Core Facilities, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Andrew W. Tai
- Department of Internal Medicine and Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
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50
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Woo TT, Williams JM, Tsai B. How host ER membrane chaperones and morphogenic proteins support virus infection. J Cell Sci 2023; 136:jcs261121. [PMID: 37401530 PMCID: PMC10357032 DOI: 10.1242/jcs.261121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023] Open
Abstract
The multi-functional endoplasmic reticulum (ER) is exploited by viruses to cause infection. Morphologically, this organelle is a highly interconnected membranous network consisting of sheets and tubules whose levels are dynamic, changing in response to cellular conditions. Functionally, the ER is responsible for protein synthesis, folding, secretion and degradation, as well as Ca2+ homeostasis and lipid biosynthesis, with each event catalyzed by defined ER factors. Strikingly, these ER host factors are hijacked by viruses to support different infection steps, including entry, translation, replication, assembly and egress. Although the full repertoire of these ER factors that are hijacked is unknown, recent studies have uncovered several ER membrane machineries that are exploited by viruses - ranging from polyomavirus to flavivirus and coronavirus - to facilitate different steps of their life cycle. These discoveries should provide better understanding of virus infection mechanisms, potentially leading to the development of more effective anti-viral therapies.
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Affiliation(s)
- Tai-Ting Woo
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109,USA
| | - Jeffrey M. Williams
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109,USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, BSRB 3043, Ann Arbor, MI 48109,USA
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