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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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Tang Z, Motoyoshi K, Honda T, Nakamura H, Murayama T. Amyloid Beta-Peptide 25-35 (Aβ 25-35) Induces Cytotoxicity via Multiple Mechanisms: Roles of the Inhibition of Glucosylceramide Synthase by Aβ 25-35 and Its Protection by D609. Biol Pharm Bull 2021; 44:1419-1426. [PMID: 34602551 DOI: 10.1248/bpb.b21-00204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sphingolipids (SLs), such as ceramide, glucosylceramide (GlcCer), and sphingomyelin, play important roles in the normal development/functions of the brain and peripheral tissues. Disruption of SL homeostasis in cells/organelles, specifically up-regulation of ceramide, is involved in multiple diseases including Alzheimer's disease (AD). One of the pathological features of AD is aggregates of amyloid beta (Aβ) peptides, and SLs regulate both the formation/aggregation of Aβ and Aβ-induced cellular responses. Up-regulation of ceramide levels via de novo and salvage synthesis pathways is reported in Aβ-treated cells and brains with AD; however, the effects of Aβ on ceramide decomposition pathways have not been elucidated. Thus, we investigated the effects of the 25-35-amino acid Aβ peptide (Aβ25-35), the fundamental cytotoxic domain of Aβ, on SL metabolism in cells treated with the fluorescent nitrobenzo-2-oxa-1,3-diazole-labeled C6-ceramide (NBD-ceramide). Aβ25-35 treatment reduced the formation of NBD-GlcCer mediated by GlcCer synthase (GCS) without affecting the formation of NBD-sphingomyelin or NBD-ceramide-1-phosphate, and reduced cell viability. Aβ25-35-induced responses decreased in cells treated with D609, a putative inhibitor of sphingomyelin synthases. Aβ25-35-induced cytotoxicity significantly increased in GCS-knockout cells and pharmacological inhibition of GCS alone demonstrated cytotoxicity. Our study revealed that Aβ25-35-induced cytotoxicity is at least partially mediated by the inhibition of GCS activity.
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Affiliation(s)
- Zhihui Tang
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University
| | - Kaisei Motoyoshi
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University
| | - Takuya Honda
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University
| | - Hiroyuki Nakamura
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University
| | - Toshihiko Murayama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University
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Sandor A, Fricker MD, Kriechbaumer V, Sweetlove LJ. IntEResting structures: formation and applications of organized smooth endoplasmic reticulum in plant cells. PLANT PHYSIOLOGY 2021; 185:550-561. [PMID: 33822222 PMCID: PMC8892044 DOI: 10.1104/pp.20.00719] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 07/21/2020] [Indexed: 06/12/2023]
Abstract
The endoplasmic reticulum (ER) is an organelle with remarkable plasticity, capable of rapidly changing its structure to accommodate different functions based on intra- and extracellular cues. One of the ER structures observed in plants is known as "organized smooth endoplasmic reticulum" (OSER), consisting of symmetrically stacked ER membrane arrays. In plants, these structures were first described in certain specialized tissues, e.g. the sieve elements of the phloem, and more recently in transgenic plants overexpressing ER membrane resident proteins. To date, much of the investigation of OSER focused on yeast and animal cells but research into plant OSER has started to grow. In this update, we give a succinct overview of research into the OSER phenomenon in plant cells with case studies highlighting both native and synthetic occurrences of OSER. We also assess the primary driving forces that trigger the formation of OSER, collating evidence from the literature to compare two competing theories for the origin of OSER: that OSER formation is initiated by oligomerizing protein accumulation in the ER membrane or that OSER is the result of ER membrane proliferation. This has long been a source of controversy in the field and here we suggest a way to integrate arguments from both sides into a single unifying theory. Finally, we discuss the potential biotechnological uses of OSER as a tool for the nascent plant synthetic biology field with possible applications as a synthetic microdomain for metabolic engineering and as an extensive membrane surface for synthetic chemistry or protein accumulation.
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Affiliation(s)
- Andras Sandor
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Mark D Fricker
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Verena Kriechbaumer
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
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Kato Y, Arakawa S, Terasawa K, Inokuchi JI, Iwata T, Shimizu S, Watabe T, Hara-Yokoyama M. The ceramide analogue N-(1-hydroxy-3-morpholino-1-phenylpropan-2-yl)decanamide induces large lipid droplet accumulation and highlights the effect of LAMP-2 deficiency on lipid droplet degradation. Bioorg Med Chem Lett 2020; 30:126891. [PMID: 31874824 DOI: 10.1016/j.bmcl.2019.126891] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/04/2019] [Accepted: 12/05/2019] [Indexed: 12/15/2022]
Abstract
Excess accumulation of intracellular lipids leads to various diseases. Lipid droplets (LDs) are ubiquitous cellular organelles for lipid storage. LDs are hydrolyzed via cytosolic lipases (lipolysis) and also degraded in lysosomes through autophagy; namely, lipophagy. A recent study has shown the size-dependent selection of LDs by the two major catabolic pathways (lipolysis and lipophagy), and thus experimental systems that can manipulate the size of LDs are now needed. The ceramide analogue N-(1-hydroxy-3-morpholino-1-phenylpropan-2-yl)decanamide (PDMP) affects the structures and functions of lysosomes/late endosomes and the endoplasmic reticulum (ER), and alters cholesterol homeostasis. We previously reported that PDMP induces autophagy via the inhibition of mTORC1. In the present study, we found that PDMP induced the accumulation of LDs, especially that of large LDs, in mouse fibroblast (L cells). Surprisingly, the LD accumulation was relieved by PDMP in L cells deficient in lysosome-associated membrane protein-2 (LAMP-2), which is reportedly important for lipophagy. An electron microscopy analysis demonstrated that the LAMP-2 deficiency caused enlarged autophagosomes/autolysosomes in L cells, which may promote the sequestration and degradation of the PDMP-dependent large LDs. Accordingly, PDMP will be useful to explore the mechanism of LD degradation, by inducing large LDs.
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Affiliation(s)
- Yuji Kato
- Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
| | - Satoko Arakawa
- Department of Pathological Cell Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
| | - Kazue Terasawa
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
| | - Jin-Ichi Inokuchi
- Division of Glycopathology, Institute of Molecular Biomembrane and Glycobiology, Tohoku Medical and Pharmaceutical University, 4-4-1, Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | - Takanori Iwata
- Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
| | - Shigeomi Shimizu
- Department of Pathological Cell Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
| | - Tetsuro Watabe
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
| | - Miki Hara-Yokoyama
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan.
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Saito A, Imaizumi K. Unfolded Protein Response-Dependent Communication and Contact among Endoplasmic Reticulum, Mitochondria, and Plasma Membrane. Int J Mol Sci 2018; 19:ijms19103215. [PMID: 30340324 PMCID: PMC6213962 DOI: 10.3390/ijms19103215] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 10/10/2018] [Accepted: 10/13/2018] [Indexed: 12/20/2022] Open
Abstract
The function of the endoplasmic reticulum (ER) can be impaired by changes to the extra- and intracellular environment, such as disruption of calcium homeostasis, expression of mutated proteins, and oxidative stress. In response to disruptions to ER homeostasis, eukaryotic cells activate canonical branches of signal transduction cascades, collectively termed the unfolded protein response (UPR). The UPR functions to remove or recover the activity of misfolded proteins that accumulated in the ER and to avoid irreversible cellular damage. Additionally, the UPR plays unique physiological roles in the regulation of diverse cellular events, including cell differentiation and development and lipid biosynthesis. Recent studies have shown that these important cellular events are also regulated by contact and communication among organelles. These reports suggest strong involvement among the UPR, organelle communication, and regulation of cellular homeostasis. However, the precise mechanisms for the formation of contact sites and the regulation of ER dynamics by the UPR remain unresolved. In this review, we summarize the current understanding of how the UPR regulates morphological changes to the ER and the formation of contact sites between the ER and other organelles. We also review how UPR-dependent connections between the ER and other organelles affect cellular and physiological functions.
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Affiliation(s)
- Atsushi Saito
- Department of Stress Protein Processing, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
| | - Kazunori Imaizumi
- Department of Biochemistry, Institute of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
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Tam AB, Roberts LS, Chandra V, Rivera IG, Nomura DK, Forbes DJ, Niwa M. The UPR Activator ATF6 Responds to Proteotoxic and Lipotoxic Stress by Distinct Mechanisms. Dev Cell 2018; 46:327-343.e7. [PMID: 30086303 DOI: 10.1016/j.devcel.2018.04.023] [Citation(s) in RCA: 102] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Revised: 04/13/2018] [Accepted: 04/24/2018] [Indexed: 02/06/2023]
Abstract
The unfolded protein response (UPR) is induced by proteotoxic stress of the endoplasmic reticulum (ER). Here we report that ATF6, a major mammalian UPR sensor, is also activated by specific sphingolipids, dihydrosphingosine (DHS) and dihydroceramide (DHC). Single mutations in a previously undefined transmembrane domain motif that we identify in ATF6 incapacitate DHS/DHC activation while still allowing proteotoxic stress activation via the luminal domain. ATF6 thus possesses two activation mechanisms: DHS/DHC activation and proteotoxic stress activation. Reporters constructed to monitor each mechanism show that phenobarbital-induced ER membrane expansion depends on transmembrane domain-induced ATF6. DHS/DHC addition preferentially induces transcription of ATF6 target lipid biosynthetic and metabolic genes over target ER chaperone genes. Importantly, ATF6 containing a luminal achromatopsia eye disease mutation, unresponsive to proteotoxic stress, can be activated by fenretinide, a drug that upregulates DHC, suggesting a potential therapy for this and other ATF6-related diseases including heart disease and stroke.
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Affiliation(s)
- Arvin B Tam
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA
| | - Lindsay S Roberts
- Department of Chemistry, Molecular and Cell Biology, and Nutritional Sciences and Toxicology, University of California, Berkeley, 127 Morgan Hall, Berkeley, CA 94720, USA
| | - Vivek Chandra
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA
| | - Io Guane Rivera
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA
| | - Daniel K Nomura
- Department of Chemistry, Molecular and Cell Biology, and Nutritional Sciences and Toxicology, University of California, Berkeley, 127 Morgan Hall, Berkeley, CA 94720, USA
| | - Douglass J Forbes
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, 2124A Pacific Hall, 9500 Gilman Drive, La Jolla, CA 92093-0347, USA
| | - Maho Niwa
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, NSB#1, Rm5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA.
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7
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Abstract
The endoplasmic reticulum (ER) is a morphologically dynamic organelle containing different membrane subdomains with distinct cellular functions. Numerous observations have revealed that ER stress response induced by disturbed ER homeostasis is linked to various neurological/neurodegenerative disorders. In contrast, recent findings unveil that ER structural derangements are linked to the progression of several neurological diseases. The derangements involve two distinct, and likely opposing pathways. One is dysfunction of ER dynamics machinery, leading to disruption of ER network organization. Another one is facilitation of pre-existing machinery, leading to generation of markedly-ordered de novo membranous structure. Restoring the ER network can be the effective way toward the cure of ER-deranged neurological disorders.
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Affiliation(s)
- Tomoyuki Yamanaka
- Laboratory of Structural Neuropathology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Nobuyuki Nukina
- Laboratory of Structural Neuropathology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan
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8
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Abstract
The experimental approach to deplete cellular glycosphingolipids (GSLs) with the specific inhibitors of glycosphingolipid biosynthesis has the potential to identify functions of endogenous GSLs. Most GSLs are derived from glucosylceramide (GlcCer). D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) inhibits GIcCer synthase and has been used extensively to study the biological functions of living cells. D-PDMP inhibits mTORC1 activity, which is independent of its inhibitory activity on GlcCer synthase. We also developed an analog of D-PDMP, D-threo-1-phenyl-2-benzyloxycarbonylamino-3-pyrrolidino-1-propanol (D-PBPP) lacking the effect on mTORC1. Here, we summarize the effects of D-PDMP and D-PBPP on the metabolism of GSLs and cell growth.
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Tang YC, Yuwen H, Wang K, Bruno PM, Bullock K, Deik A, Santaguida S, Trakala M, Pfau SJ, Zhong N, Huang T, Wang L, Clish CB, Hemann MT, Amon A. Aneuploid Cell Survival Relies upon Sphingolipid Homeostasis. Cancer Res 2017; 77:5272-5286. [PMID: 28775166 DOI: 10.1158/0008-5472.can-17-0049] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 06/13/2017] [Accepted: 07/25/2017] [Indexed: 01/26/2023]
Abstract
Aneuploidy, a hallmark of cancer cells, poses an appealing opportunity for cancer treatment and prevention strategies. Using a cell-based screen to identify small molecules that could selectively kill aneuploid cells, we identified the compound N-[2-hydroxy-1-(4-morpholinylmethyl)-2-phenylethyl]-decanamide monohydrochloride (DL-PDMP), an antagonist of UDP-glucose ceramide glucosyltransferase. DL-PDMP selectively inhibited proliferation of aneuploid primary mouse embryonic fibroblasts and aneuploid colorectal cancer cells. Its selective cytotoxic effects were based on further accentuating the elevated levels of ceramide, which characterize aneuploid cells, leading to increased apoptosis. We observed that DL-PDMP could also enhance the cytotoxic effects of paclitaxel, a standard-of-care chemotherapeutic agent that causes aneuploidy, in human colon cancer and mouse lymphoma cells. Our results offer pharmacologic evidence that the aneuploid state in cancer cells can be targeted selectively for therapeutic purposes, or for reducing the toxicity of taxane-based drug regimens. Cancer Res; 77(19); 5272-86. ©2017 AACR.
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Affiliation(s)
- Yun-Chi Tang
- The Key Laboratory of Stem Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Hui Yuwen
- The Key Laboratory of Stem Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Kaiying Wang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peter M Bruno
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Kevin Bullock
- Metabolomics Platform, Broad Institute of MIT and Harvard, Cambridge, Massachusetts
| | - Amy Deik
- Metabolomics Platform, Broad Institute of MIT and Harvard, Cambridge, Massachusetts
| | - Stefano Santaguida
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Marianna Trakala
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Sarah J Pfau
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Na Zhong
- The Key Laboratory of Stem Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tao Huang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lan Wang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Clary B Clish
- Metabolomics Platform, Broad Institute of MIT and Harvard, Cambridge, Massachusetts
| | - Michael T Hemann
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Angelika Amon
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts.
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
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KOGA D, BOCHIMOTO H, KUSUMI S, USHIKI T, WATANABE T. <b>Changes in the three-dimensional ultrastructure of membranous organelles in male rat pituitary gonadotropes after castration</b>. Biomed Res 2017; 38:1-18. [DOI: 10.2220/biomedres.38.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Daisuke KOGA
- Department of Microscopic Anatomy and Cell Biology, Asahikawa Medical University
- Division of Microscopic Anatomy and Bio-imaging, Department of Cellular Function, Niigata University Graduate School of Medical and Dental Sciences
| | - Hiroki BOCHIMOTO
- Department of Microscopic Anatomy and Cell Biology, Asahikawa Medical University
| | - Satoshi KUSUMI
- Division of Morphological Sciences, Kagoshima University Graduate School of Medical and Dental Sciences
| | - Tatsuo USHIKI
- Division of Microscopic Anatomy and Bio-imaging, Department of Cellular Function, Niigata University Graduate School of Medical and Dental Sciences
| | - Tsuyoshi WATANABE
- Department of Microscopic Anatomy and Cell Biology, Asahikawa Medical University
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11
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Ode T, Podyma-Inoue KA, Terasawa K, Inokuchi JI, Kobayashi T, Watabe T, Izumi Y, Hara-Yokoyama M. PDMP, a ceramide analogue, acts as an inhibitor of mTORC1 by inducing its translocation from lysosome to endoplasmic reticulum. Exp Cell Res 2016; 350:103-114. [PMID: 27865938 DOI: 10.1016/j.yexcr.2016.11.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 11/03/2016] [Accepted: 11/15/2016] [Indexed: 11/20/2022]
Abstract
Mammalian or mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth, metabolism, and cell differentiation. Recent studies have revealed that the recruitment of mTORC1 to lysosomes is essential for its activation. The ceramide analogue 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), a well known glycosphingolipid synthesis inhibitor, also affects the structures and functions of various organelles, including lysosomes and endoplasmic reticulum (ER). We investigated whether PDMP regulates the mTORC1 activity through its effects on organellar behavior. PDMP induced the translocation of mTORC1 from late endosomes/lysosomes, leading to the dissociation of mTORC1 from its activator Rheb in MC3T3-E1 cells. Surprisingly, we found mTORC1 translocation to the ER upon PDMP treatment. This effect of PDMP was independent of its action as the inhibitor, since two stereoisomers of PDMP, with and without the inhibitor activity, showed essentially the same effect. We confirmed that PDMP inhibits the mTORC1 activity based on the decrease in the phosphorylation of ribosomal S6 kinase, a downstream target of mTORC1, and the increase in LC3 puncta, reflecting autophagosome formation. Furthermore, PDMP inhibited the mTORC1-dependent osteoblastic cell proliferation and differentiation of MC3T3-E1 cells. Accordingly, the present results reveal a novel mechanism of PDMP, which inhibits the mTORC1 activity by inducing the translocation of mTOR from lysosomes to the ER.
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Affiliation(s)
- Takashi Ode
- Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan; Research Fellow of the Japan Society for the Promotion of Science (JSPS), 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan
| | - Katarzyna A Podyma-Inoue
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Kazue Terasawa
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Jin-Ichi Inokuchi
- Division of Glycopathology, Institute of Molecular Biomembrane and Glycobiology, Tohoku Medical and Pharmaceutical University, 4-4-1, Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | - Toshihide Kobayashi
- Lipid Biology Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Tetsuro Watabe
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yuichi Izumi
- Department of Periodontology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Miki Hara-Yokoyama
- Department of Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
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12
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Rämö O, Kumar D, Gucciardo E, Joensuu M, Saarekas M, Vihinen H, Belevich I, Smolander OP, Qian K, Auvinen P, Jokitalo E. NOGO-A/RTN4A and NOGO-B/RTN4B are simultaneously expressed in epithelial, fibroblast and neuronal cells and maintain ER morphology. Sci Rep 2016; 6:35969. [PMID: 27786289 PMCID: PMC5081510 DOI: 10.1038/srep35969] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 10/07/2016] [Indexed: 02/08/2023] Open
Abstract
Reticulons (RTNs) are a large family of membrane associated proteins with various functions. NOGO-A/RTN4A has a well-known function in limiting neurite outgrowth and restricting the plasticity of the mammalian central nervous system. On the other hand, Reticulon 4 proteins were shown to be involved in forming and maintaining endoplasmic reticulum (ER) tubules. Using comparative transcriptome analysis and qPCR, we show here that NOGO-B/RTN4B and NOGO-A/RTN4A are simultaneously expressed in cultured epithelial, fibroblast and neuronal cells. Electron tomography combined with immunolabelling reveal that both isoforms localize preferably to curved membranes on ER tubules and sheet edges. Morphological analysis of cells with manipulated levels of NOGO-B/RTN4B revealed that it is required for maintenance of normal ER shape; over-expression changes the sheet/tubule balance strongly towards tubules and causes the deformation of the cell shape while depletion of the protein induces formation of large peripheral ER sheets.
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Affiliation(s)
- Olli Rämö
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Darshan Kumar
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Erika Gucciardo
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Merja Joensuu
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Maiju Saarekas
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Ilya Belevich
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Olli-Pekka Smolander
- DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Kui Qian
- DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Petri Auvinen
- DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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13
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Pawlikowska-Pawlęga B, Misiak LE, Jarosz-Wilkołazka A, Zarzyka B, Paduch R, Gawron A, Gruszecki WI. Biophysical characterization of genistein-membrane interaction and its correlation with biological effect on cells - The case of EYPC liposomes and human erythrocyte membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2127-38. [PMID: 24813834 DOI: 10.1016/j.bbamem.2014.04.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/28/2014] [Accepted: 04/30/2014] [Indexed: 12/18/2022]
Abstract
With application of EPR and (1)H NMR techniques genistein interaction with liposomes formed with egg yolk lecithin and with erythrocyte membranes was assessed. The present study addressed the problem of genistein localization and its effects on lipid membrane fluidity and protein conformation. The range of microscopic techniques was employed to study genistein effects on HeLa cells and human erythrocytes. Moreover, DPPH bioassay, superoxide anion radical test and enzymatic measurements were performed in HeLa cells subjected to genistein. The gathered results from both EPR and NMR techniques indicated strong ordering effect of genistein on the motional freedom of lipids in the head group region and the adjacent hydrophobic zone in liposomal as well as in red blood cell membranes. EPR study of human ghost showed also the changes in the erythrocyte membrane protein conformation. The membrane effects of genistein were correlated with the changes in internal membranes arrangement of HeLa cells as it was noticed using transmission electron microscopic and fluorescent techniques. Scanning electron and light microscopy methods showed that one of the aftermaths of genistein incorporation into membranes was creation of echinocytic form of the red blood cells with reduced diameter. Genistein improved redox status of HeLa cells treated with H2O2 by lowering radicals' level. In conclusion, the capacity of genistein to incorporate, to affect membrane organization and to change its biophysical properties is correlated with the changes inside the cells.
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Affiliation(s)
- Bożena Pawlikowska-Pawlęga
- Department of Comparative Anatomy and Anthropology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland; Electron Microscopy Laboratory, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Lucjan E Misiak
- Institute of Physics, Maria Curie-Skłodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland.
| | - Anna Jarosz-Wilkołazka
- Department of Biochemistry, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Barbara Zarzyka
- Department of Cell Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Roman Paduch
- Department of Virology and Immunology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Antoni Gawron
- Department of Comparative Anatomy and Anthropology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Wieslaw I Gruszecki
- Department of Biophysics, Institute of Physics, Maria Curie-Skłodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland.
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14
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Abstract
Plasma cells (PCs) are the effectors responsible for antibody (Ab)-mediated immunity. They differentiate from B lymphocytes through a complete remodeling of their original structure and function. Stress is a constitutive element of PC differentiation. Macroautophagy, conventionally referred to as autophagy, is a conserved lysosomal recycling strategy that integrates cellular metabolism and enables adaptation to stress. In metazoa, autophagy plays diverse roles in cell differentiation. Recently, a number of autophagic functions have been recognized in innate and adaptive immunity, including clearance of intracellular pathogens, inflammasome regulation, lymphocyte ontogenesis, and antigen presentation. We identified a previously unrecognized role played by autophagy in PC differentiation and activity. Following B cell activation, autophagy moderates the expression of the transcriptional repressor Blimp-1 and immunoglobulins through a selective negative control exerted on the size of the endoplasmic reticulum and its stress signaling response, including the essential PC transcription factor, XBP-1. This containment of PC differentiation and function, i.e., Ab production, is essential to optimize energy metabolism and viability. As a result, autophagy sustains Ab responses in vivo. Moreover, autophagy is an essential intrinsic determinant of long-lived PCs in their as yet poorly understood bone marrow niche. In this essay, we discuss these findings in the context of the established biological functions of autophagy, and their manifold implications for adaptive immunity and PC diseases, in primis multiple myeloma.
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Affiliation(s)
- Laura Oliva
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute , Milan , Italy
| | - Simone Cenci
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute , Milan , Italy ; Università Vita-Salute San Raffaele , Milan , Italy ; Bone Pathophysiology Program (BoNetwork), Division of Genetics and Cell Biology, San Raffaele Scientific Institute , Milan , Italy
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15
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Fossati M, Borgese N, Colombo SF, Francolini M. Visualization of endoplasmic reticulum subdomains in cultured cells. J Vis Exp 2014:e50985. [PMID: 24637314 DOI: 10.3791/50985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The lipids and proteins in eukaryotic cells are continuously exchanged between cell compartments, although these retain their distinctive composition and functions despite the intense interorganelle molecular traffic. The techniques described in this paper are powerful means of studying protein and lipid mobility and trafficking in vivo and in their physiological environment. Fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) are widely used live-cell imaging techniques for studying intracellular trafficking through the exo-endocytic pathway, the continuity between organelles or subcompartments, the formation of protein complexes, and protein localization in lipid microdomains, all of which can be observed under physiological and pathological conditions. The limitations of these approaches are mainly due to the use of fluorescent fusion proteins, and their potential drawbacks include artifactual over-expression in cells and the possibility of differences in the folding and localization of tagged and native proteins. Finally, as the limit of resolution of optical microscopy (about 200 nm) does not allow investigation of the fine structure of the ER or the specific subcompartments that can originate in cells under stress (i.e. hypoxia, drug administration, the over-expression of transmembrane ER resident proteins) or under pathological conditions, we combine live-cell imaging of cultured transfected cells with ultrastructural analyses based on transmission electron microscopy.
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Affiliation(s)
- Matteo Fossati
- Fondazione Filarete; Department of Biotechnology and Translational Medicine, University of Milan; Neuroscience Institute, National Research Council (CNR)
| | - Nica Borgese
- Department of Biotechnology and Translational Medicine, University of Milan; Neuroscience Institute, National Research Council (CNR); Department of Health Science, "Magna Graecia" University of Catanzaro
| | - Sara Francesca Colombo
- Department of Biotechnology and Translational Medicine, University of Milan; Neuroscience Institute, National Research Council (CNR)
| | - Maura Francolini
- Fondazione Filarete; Department of Biotechnology and Translational Medicine, University of Milan;
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16
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Ivanov AI. Pharmacological inhibitors of exocytosis and endocytosis: novel bullets for old targets. Methods Mol Biol 2014; 1174:3-18. [PMID: 24947371 DOI: 10.1007/978-1-4939-0944-5_1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Pharmacological inhibitors of vesicle trafficking possess great promise as valuable analytical tools for the study of a variety of biological processes and as potential therapeutic agents to fight microbial infections and cancer. However, many commonly used trafficking inhibitors are characterized by poor selectivity that diminishes their use in solving basic problems of cell biology or drug development. Recent high-throughput chemical screens intensified the search for novel modulators of vesicle trafficking, and successfully identified a number of small molecules that inhibit exocytosis and endocytosis in different types of mammalian cells. This chapter provides a systematic overview of recently discovered inhibitors of vesicle trafficking. It describes cellular effects and mechanisms of action of novel inhibitors of exocytosis and endocytosis. Furthermore, it pays special attention to the selectivity and possible off-target effects of these inhibitors.
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Affiliation(s)
- Andrei I Ivanov
- Department of Human and Molecular Genetics, VCU Institute of Molecular Medicine, Virginia Commonwealth University, Goodwin Laboratory, 401 College Street, 980035, Richmond, VA, 23298, USA,
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17
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Varadarajan S, Tanaka K, Smalley JL, Bampton ETW, Pellecchia M, Dinsdale D, Willars GB, Cohen GM. Endoplasmic reticulum membrane reorganization is regulated by ionic homeostasis. PLoS One 2013; 8:e56603. [PMID: 23457590 PMCID: PMC3574070 DOI: 10.1371/journal.pone.0056603] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 01/14/2013] [Indexed: 01/01/2023] Open
Abstract
Recently we described a new, evolutionarily conserved cellular stress response characterized by a reversible reorganization of endoplasmic reticulum (ER) membranes that is distinct from canonical ER stress and the unfolded protein response (UPR). Apogossypol, a putative broad spectrum BCL-2 family antagonist, was the prototype compound used to induce this ER membrane reorganization. Following microarray analysis of cells treated with apogossypol, we used connectivity mapping to identify a wide range of structurally diverse chemicals from different pharmacological classes and established their ability to induce ER membrane reorganization. Such structural diversity suggests that the mechanisms initiating ER membrane reorganization are also diverse and a major objective of the present study was to identify potentially common features of these mechanisms. In order to explore this, we used hierarchical clustering of transcription profiles for a number of chemicals that induce membrane reorganization and discovered two distinct clusters. One cluster contained chemicals with known effects on Ca2+ homeostasis. Support for this was provided by the findings that ER membrane reorganization was induced by agents that either deplete ER Ca2+ (thapsigargin) or cause an alteration in cellular Ca2+ handling (calmodulin antagonists). Furthermore, overexpression of the ER luminal Ca2+ sensor, STIM1, also evoked ER membrane reorganization. Although perturbation of Ca2+ homeostasis was clearly one mechanism by which some agents induced ER membrane reorganization, influx of extracellular Na+ but not Ca2+ was required for ER membrane reorganization induced by apogossypol and the related BCL-2 family antagonist, TW37, in both human and yeast cells. Not only is this novel, non-canonical ER stress response evolutionary conserved but so also are aspects of the mechanism of formation of ER membrane aggregates. Thus perturbation of ionic homeostasis is important in the regulation of ER membrane reorganization.
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Affiliation(s)
| | - Kayoko Tanaka
- Department of Biochemistry, University of Leicester, Leicester, United Kingdom
| | - Joshua L. Smalley
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | | | | | - David Dinsdale
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Gary B. Willars
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
| | - Gerald M. Cohen
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
- Department of Biochemistry, University of Leicester, Leicester, United Kingdom
- * E-mail:
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18
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Lu L, Hannoush RN, Goess BC, Varadarajan S, Shair MD, Kirchhausen T. The small molecule dispergo tubulates the endoplasmic reticulum and inhibits export. Mol Biol Cell 2013; 24:1020-9. [PMID: 23389632 PMCID: PMC3608490 DOI: 10.1091/mbc.e12-08-0575] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A small molecule called dispergo is identified that acutely and reversibly induces ER tubulation and the ER export block that results in the gradual merge of the Golgi membrane with the ER. It is the first reported small molecule with such a phenotype and could facilitate the functional study of the ER. The mammalian endoplasmic reticulum (ER) is an organelle that maintains a complex, compartmentalized organization of interconnected cisternae and tubules while supporting a continuous flow of newly synthesized proteins and lipids to the Golgi apparatus. Using a phenotypic screen, we identify a small molecule, dispergo, that induces reversible loss of the ER cisternae and extensive ER tubulation, including formation of ER patches comprising densely packed tubules. Dispergo also prevents export from the ER to the Golgi apparatus, and this traffic block results in breakdown of the Golgi apparatus, primarily due to maintenance of the constitutive retrograde transport of its components to the ER. The effects of dispergo are reversible, since its removal allows recovery of the ER cisternae at the expense of the densely packed tubular ER patches. This recovery occurs together with reactivation of ER-to-Golgi traffic and regeneration of a functional Golgi with correct morphology. Because dispergo is the first small molecule that reversibly tubulates the ER and inhibits its export function, it will be useful in studying these complex processes.
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Affiliation(s)
- Lei Lu
- Department of Cell Biology, Harvard Medical School, MA, USA
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19
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Plasma cells require autophagy for sustainable immunoglobulin production. Nat Immunol 2013; 14:298-305. [PMID: 23354484 DOI: 10.1038/ni.2524] [Citation(s) in RCA: 309] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 12/14/2012] [Indexed: 02/06/2023]
Abstract
The role of autophagy in plasma cells is unknown. Here we found notable autophagic activity in both differentiating and long-lived plasma cells and investigated its function through the use of mice with conditional deficiency in the essential autophagic molecule Atg5 in B cells. Atg5(-/-) differentiating plasma cells had a larger endoplasmic reticulum (ER) and more ER stress signaling than did their wild-type counterparts, which led to higher expression of the transcriptional repressor Blimp-1 and immunoglobulins and more antibody secretion. The enhanced immunoglobulin synthesis was associated with less intracellular ATP and more death of mutant plasma cells, which identified an unsuspected autophagy-dependent cytoprotective trade-off between immunoglobulin synthesis and viability. In vivo, mice with conditional deficiency in Atg5 in B cells had defective antibody responses, complete selection in the bone marrow for plasma cells that escaped Atg5 deletion and fewer antigen-specific long-lived bone marrow plasma cells than did wild-type mice, despite having normal germinal center responses. Thus, autophagy is specifically required for plasma cell homeostasis and long-lived humoral immunity.
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20
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Krüger F, Krebs M, Viotti C, Langhans M, Schumacher K, Robinson DG. PDMP induces rapid changes in vacuole morphology in Arabidopsis root cells. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:529-40. [PMID: 23230024 PMCID: PMC3542044 DOI: 10.1093/jxb/ers345] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
PDMP (D-L-threo-1-phenyl-2-decanoyl amino-3-morpholino-1-propanol) is a well-known inhibitor of glucosylceramide synthase (GCS), a key enzyme in sphingolipid biosynthesis. Through the resultant increase in ceramides which interact with mTOR and Beclin1 (Atg6), this drug is also known to induce macroautophagy in mammalian cells. This study investigated the response of Arabidopsis root cells to PDMP, and what are probably numerous tightly packed small vacuoles in the control cells appear to fuse to form a single globular-shaped vacuole. However, during this fusion process, cytoplasm channels between the individual vacuoles become trapped in deep invaginations of the tonoplast. In both optical sections in the confocal laser scanning microscope and in ultrathin sections in the electron microscope, these invaginations have the appearance of cytoplasmic inclusions in the vacuole lumen. These changes in vacuole morphology are rapid (occurring within minutes after application of PDMP) and are independent of ongoing protein synthesis. The tonoplast invaginations remain visible for hours, but after 24h almost all disappear. Experiments designed to examine whether ceramide levels might be the cause of the PDMP effect have not proved conclusive. On the other hand, this study has been able to rule out the release of Ca(2+) ions from intracellular stores as a contributing factor.
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Affiliation(s)
- Falco Krüger
- Department of Plant Developmental Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
- * These authors contributed equally to this manuscript.
| | - Melanie Krebs
- Department of Plant Developmental Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
- * These authors contributed equally to this manuscript.
| | - Corrado Viotti
- Department of Plant Developmental Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Markus Langhans
- Department of Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Karin Schumacher
- Department of Plant Developmental Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - David G. Robinson
- Department of Plant Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
- * These authors contributed equally to this manuscript.
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21
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Pawlikowska-Pawlęga B, Misiak LE, Zarzyka B, Paduch R, Gawron A, Gruszecki WI. FTIR, (1)H NMR and EPR spectroscopy studies on the interaction of flavone apigenin with dipalmitoylphosphatidylcholine liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:518-27. [PMID: 23088916 DOI: 10.1016/j.bbamem.2012.10.013] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 09/27/2012] [Accepted: 10/15/2012] [Indexed: 11/25/2022]
Abstract
Apigenin (5,7,4'-trihydroxyflavone) is a cancer chemopreventive agent and a member of the family of plant flavonoids. Apigenin interaction with liposomes formed with dipalmitoylphosphatidylcholine (DPPC) was investigated by means of FTIR spectroscopy, (1)H NMR and EPR techniques. Fluorescent microscopy and electron microscopy were applied to study the apigenin effects on colon myofibroblasts and human skin fibroblasts. The strong rigidifying effect of apigenin with respect to polar head groups was concluded on the basis of the action of the flavone on partition coefficient of Tempo spin label between the water and lipid phases. The ordering effect was also found in hydrophobic region at the depth monitored by 5-SASL and 16-SASL spin labels. The inclusion of apigenin to the membrane restricted the motional freedom of polar head groups lowering penetration of Pr(3+) ions to the membranes. The (1)H NMR technique supported also the restriction of motional freedom of the membrane in the hydrophobic region, especially in the zone of CH(2) groups of alkyl chains. FTIR analysis showed that apigenin incorporates into DPPC liposomes via hydrogen bonding between its own hydroxyl groups and lipid polar head groups in the C-O-P-O-C segment. It is also very likely that hydroxyl groups of apigenin link with polar groups of DPPC by water bridges. Electron and fluorescence microscopic observations revealed changes in the internal membrane organization of the examined cells. In conclusion, the changes of the structural and dynamic properties of membranes can be crucial for processes involving tumor suppression signal transduction pathways and cell cycle regulation.
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Affiliation(s)
- Bożena Pawlikowska-Pawlęga
- Department of Comparative Anatomy and Anthropology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
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22
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A novel cellular stress response characterised by a rapid reorganisation of membranes of the endoplasmic reticulum. Cell Death Differ 2012; 19:1896-907. [PMID: 22955944 DOI: 10.1038/cdd.2012.108] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Canonical endoplasmic reticulum (ER) stress, which occurs in many physiological and disease processes, results in activation of the unfolded protein response (UPR). We now describe a new, evolutionarily conserved cellular stress response characterised by a striking, but reversible, reorganisation of ER membranes that occurs independently of the UPR, resulting in impaired ER transport and function. This reorganisation is characterised by a dramatic redistribution and clustering of ER membrane proteins. ER membrane aggregation is regulated, in part, by anti-apoptotic BCL-2 family members, particularly MCL-1. Using connectivity mapping, we report the widespread occurrence of this stress response by identifying several structurally diverse chemicals from different pharmacological classes, including antihistamines, antimalarials and antipsychotics, which induce ER membrane reorganisation. Furthermore, we demonstrate the potential of ER membrane aggregation to result in pathological consequences, such as the long-QT syndrome, a cardiac arrhythmic abnormality, arising because of a novel trafficking defect of the human ether-a-go-go-related channel protein from the ER to the plasma membrane. Thus, ER membrane reorganisation is a feature of a new cellular stress pathway, clearly distinct from the UPR, with important consequences affecting the normal functioning of the ER.
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23
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Pawlikowska-Pawlęga B, Misiak LE, Zarzyka B, Paduch R, Gawron A, Gruszecki WI. Localization and interaction of genistein with model membranes formed with dipalmitoylphosphatidylcholine (DPPC). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1785-93. [DOI: 10.1016/j.bbamem.2012.03.020] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 03/19/2012] [Accepted: 03/30/2012] [Indexed: 11/24/2022]
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24
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Selective activation of the transcription factor ATF6 mediates endoplasmic reticulum proliferation triggered by a membrane protein. Proc Natl Acad Sci U S A 2011; 108:7832-7. [PMID: 21521793 DOI: 10.1073/pnas.1101379108] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
It is well known that the endoplasmic reticulum (ER) is capable of expanding its surface area in response both to cargo load and to increased expression of resident membrane proteins. Although the response to increased cargo load, known as the unfolded protein response (UPR), is well characterized, the mechanism of the response to membrane protein load has been unclear. As a model system to investigate this phenomenon, we have used a HeLa-TetOff cell line inducibly expressing a tail-anchored construct consisting of an N-terminal cytosolic GFP moiety anchored to the ER membrane by the tail of cytochrome b5 [GFP-b(5)tail]. After removal of doxycycline, GFP-b(5)tail is expressed at moderate levels (1-2% of total ER protein) that, nevertheless, induce ER proliferation, as assessed both by EM and by a three- to fourfold increase in phosphatidylcholine synthesis. We investigated possible participation of each of the three arms of the UPR and found that only the activating transcription factor 6 (ATF6) arm was selectively activated after induction of GFP-b(5)tail expression; peak ATF6α activation preceded the increase in phosphatidylcholine synthesis. Surprisingly, up-regulation of known ATF6 target genes was not observed under these conditions. Silencing of ATF6α abolished the ER proliferation response, whereas knockdown of Ire1 was without effect. Because GFP-b(5)tail lacks a luminal domain, the response we observe is unlikely to originate from the ER lumen. Instead, we propose that a sensing mechanism operates within the lipid bilayer to trigger the selective activation of ATF6.
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25
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Kunzelmann K, Kongsuphol P, Chootip K, Toledo C, Martins JR, Almaca J, Tian Y, Witzgall R, Ousingsawat J, Schreiber R. Role of the Ca2+-activated Cl- channels bestrophin and anoctamin in epithelial cells. Biol Chem 2011; 392:125-34. [DOI: 10.1515/bc.2011.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Two families of proteins, the bestrophins (Best) and the recently cloned TMEM16 proteins (anoctamin, Ano), recapitulate properties of Ca2+-activated Cl- currents. Best1 is strongly expressed in the retinal pigment epithelium and could have a function as a Ca2+-activated Cl- channel as well as a regulator of Ca2+ signaling. It is also present at much lower levels in other cell types including epithelial cells, where it regulates plasma membrane localized Cl- channels by controlling intracellular Ca2+ levels. Best1 interacts with important Ca2+-signaling proteins such as STIM1 and can interact directly with other Ca2+-activated Cl- channels such as TMEM16A. Best1 is detected in the endoplasmic reticulum (ER) where it shapes the dynamic ER structure and regulates cell proliferation, which could be important for renal cystogenesis. Ca2+-activated Cl- channels of the anoctamin family (TMEM16A) show biophysical and pharmacological properties that are typical for endogenous Ca2+-dependent Cl- channels. TMEM16 proteins are abundantly expressed and many reports demonstrate their physiological importance in epithelial as well as non-epithelial cells. These channels are also activated by cell swelling and can therefore control cell volume, proliferation and apoptosis. To fully understand the function and regulation of Ca2+-activated Cl- currents, it is necessary to appreciate that Best1 and TMEM16A are embedded in a protein network and that they probably operate in functional microdomains.
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26
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Oyetibo GO, Ilori MO, Adebusoye SA, Obayori OS, Amund OO. Bacteria with dual resistance to elevated concentrations of heavy metals and antibiotics in Nigerian contaminated systems. ENVIRONMENTAL MONITORING AND ASSESSMENT 2010; 168:305-314. [PMID: 19688604 DOI: 10.1007/s10661-009-1114-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 07/27/2009] [Indexed: 05/28/2023]
Abstract
Samples of soil, water, and sediments from industrial estates in Lagos were collected and analyzed for heavy metals and physicochemical composition. Bacteria that are resistant to elevated concentrations of metals (Cd(2+), Co(2+), Ni(2+), Cr(6+), and Hg(2+)) were isolated from the samples, and they were further screened for antibiotic sensitivity. The minimum tolerance concentrations (MTCs) of the isolates with dual resistance to the metals were determined. The physicochemistry of all the samples indicated were heavily polluted. Twenty-two of the 270 bacterial strains isolated showed dual resistances to antibiotics and heavy metals. The MTCs of isolates to the metals were 14 mM for Cd(2+), 15 mM for Co(2+) and Ni(2+), 17 mM for Cr(6+), and 10 mM for Hg(2+). Five strains (Pseudomonas aeruginosa, Actinomyces turicensis, Acinetobacter junni, Nocardia sp., and Micrococcus sp.) resisted all the 18 antibiotics tested. Whereas Rhodococcus sp. and Micrococcus sp. resisted 15 mM Ni(2+), P. aeruginosa resisted 10 mM Co(2+). To our knowledge, there has not been any report of bacterial strains resisting such high doses of metals coupled with wide range of antibiotics. Therefore, dual expressions of antibiotics and heavy-metal resistance make the isolates, potential seeds for decommissioning of sites polluted with industrial effluents rich in heavy metals, since the bacteria will be able to withstand in situ antibiosis that may prevail in such ecosystems.
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Affiliation(s)
- Ganiyu O Oyetibo
- Department of Botany and Microbiology, Faculty of Science, University of Lagos, Akoka, Lagos, Nigeria
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Fasana E, Fossati M, Ruggiano A, Brambillasca S, Hoogenraad CC, Navone F, Francolini M, Borgese N. A VAPB mutant linked to amyotrophic lateral sclerosis generates a novel form of organized smooth endoplasmic reticulum. FASEB J 2009; 24:1419-30. [PMID: 20008544 DOI: 10.1096/fj.09-147850] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
VAPB (vesicle-associated membrane protein-associated protein B) is an endoplasmic reticulum (ER)-resident tail-anchored adaptor protein involved in lipid transport. A dominantly inherited mutant, P56S-VAPB, causes a familial form of amyotrophic lateral sclerosis (ALS) and forms poorly characterized inclusion bodies in cultured cells. To provide a cell biological basis for the understanding of mutant VAPB pathogenicity, we investigated its biogenesis and the inclusions that it generates. Translocation assays in cell-free systems and in cultured mammalian cells were used to investigate P56S-VAPB membrane insertion, and the inclusions were characterized by confocal imaging and electron microscopy. We found that mutant VAPB inserts post-translationally into ER membranes in a manner indistinguishable from the wild-type protein but that it rapidly clusters to form inclusions that remain continuous with the rest of the ER. Inclusions were induced by the mutant also when it was expressed at levels comparable to the endogenous wild-type protein. Ultrastructural analysis revealed that the inclusions represent a novel form of organized smooth ER (OSER) consisting in a limited number of parallel cisternae (usually 2 or 3) interleaved by a approximately 30 nm-thick electron-dense cytosolic layer. Our results demonstrate that the ALS-linked VAPB mutant causes dramatic ER restructuring that may underlie its pathogenicity in motoneurons.
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Affiliation(s)
- Elisa Fasana
- Consiglio Nazionale delle Ricerche Institute of Neuroscience, via Vanvitelli 32, 20129 Milano, Italy
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28
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Iinuma T, Aoki T, Arasaki K, Hirose H, Yamamoto A, Samata R, Hauri HP, Arimitsu N, Tagaya M, Tani K. Role of syntaxin 18 in the organization of endoplasmic reticulum subdomains. J Cell Sci 2009; 122:1680-90. [PMID: 19401338 DOI: 10.1242/jcs.036103] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The presence of subdomains in the endoplasmic reticulum (ER) enables this organelle to perform a variety of functions, yet the mechanisms underlying their organization are poorly understood. In the present study, we show that syntaxin 18, a SNAP (soluble NSF attachment protein) receptor localized in the ER, is important for the organization of two ER subdomains, smooth/rough ER membranes and ER exit sites. Knockdown of syntaxin 18 caused a global change in ER membrane architecture, leading to the segregation of the smooth and rough ER. Furthermore, the organization of ER exit sites was markedly changed concomitantly with dispersion of the ER-Golgi intermediate compartment and the Golgi complex. These morphological changes in the ER were substantially recovered by treatment of syntaxin-18-depleted cells with brefeldin A, a reagent that stimulates retrograde membrane flow to the ER. These results suggest that syntaxin 18 has an important role in ER subdomain organization by mediating the fusion of retrograde membrane carriers with the ER membrane.
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Affiliation(s)
- Takayuki Iinuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
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29
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McGovern G, Jeffrey M. Scrapie-specific pathology of sheep lymphoid tissues. PLoS One 2007; 2:e1304. [PMID: 18074028 PMCID: PMC2110901 DOI: 10.1371/journal.pone.0001304] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Accepted: 11/14/2007] [Indexed: 11/19/2022] Open
Abstract
Transmissible spongiform encephalopathies (TSEs) or prion diseases often result in accumulation of disease-associated PrP (PrPd) in the lymphoreticular system (LRS), specifically in association with follicular dendritic cells (FDCs) and tingible body macrophages (TBMs) of secondary follicles. We studied the effects of sheep scrapie on lymphoid tissue in tonsils and lymph nodes by light and electron microscopy. FDCs of sheep were grouped according to morphology as immature, mature or regressing. Scrapie was associated with FDC dendrite hypertrophy and electron dense deposit or vesicles. PrPd was located using immunogold labelling at the plasmalemma of FDC dendrites and, infrequently, mature B cells. Abnormal electron dense deposits surrounding FDC dendrites were identified as immunoglobulins suggesting that excess immune complexes are retained and are indicative of an FDC dysfunction. Within scrapie-affected lymph nodes, macrophages outside the follicle and a proportion of germinal centre TBMs accumulated PrPd within endosomes and lysosomes. In addition, TBMs showed PrPd in association with the cell membrane, non-coated pits and vesicles, and also with discrete, large and random endoplasmic reticulum networks, which co-localised with ubiquitin. These observations suggest that PrPd is internalised via the caveolin-mediated pathway, and causes an abnormal disease-related alteration in endoplasmic reticulum structure. In contrast to current dogma, this study shows that sheep scrapie is associated with cytopathology of germinal centres, which we attribute to abnormal antigen complex trapping by FDCs and abnormal endocytic events in TBMs. The nature of the sub-cellular changes in FDCs and TBMs differs from those of scrapie infected neurones and glial cells suggesting that different PrPd/cell membrane interactions occur in different cell types.
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Affiliation(s)
- Gillian McGovern
- Veterinary Laboratories Agency Lasswade, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, United Kingdom.
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30
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Goetz JG, Genty H, St-Pierre P, Dang T, Joshi B, Sauvé R, Vogl W, Nabi IR. Reversible interactions between smooth domains of the endoplasmic reticulum and mitochondria are regulated by physiological cytosolic Ca2+ levels. J Cell Sci 2007; 120:3553-64. [PMID: 17895372 DOI: 10.1242/jcs.03486] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The 3F3A monoclonal antibody to autocrine motility factor receptor (AMFR) labels mitochondria-associated smooth endoplasmic reticulum (ER) tubules. siRNA down-regulation of AMFR expression reduces mitochondria-associated 3F3A labelling. The 3F3A-labelled ER domain does not overlap with reticulon-labelled ER tubules, the nuclear membrane or perinuclear ER markers and only partially overlaps with the translocon component Sec61alpha. Upon overexpression of FLAG-tagged AMFR, 3F3A labelling is mitochondria associated, excluded from the perinuclear ER and co-distributes with reticulon. 3F3A labelling therefore defines a distinct mitochondria-associated ER domain. Elevation of free cytosolic Ca(2+) levels with ionomycin promotes dissociation of 3F3A-labelled tubules from mitochondria and, judged by electron microscopy, disrupts close contacts (<50 nm) between smooth ER tubules and mitochondria. The ER tubule-mitochondria association is similarly disrupted upon thapsigargin-induced release of ER Ca(2+) stores or purinergic receptor stimulation by ATP. The inositol (1,4,5)-trisphosphate [Ins(1,4,5)P(3)] receptor (IP3R) colocalises to 3F3A-labelled mitochondria-associated ER tubules, and conditions that induce ER tubule-mitochondria dissociation disrupt continuity between 3F3A- and IP3R-labelled ER domains. RAS-transformed NIH-3T3 cells have increased basal cytosolic Ca(2+) levels and show dissociation of the 3F3A-labelled, but not IP3R-labelled, ER from mitochondria. Our data indicate that regulation of the ER-mitochondria association by free cytosolic Ca(2+) is a characteristic of smooth ER domains and that multiple mechanisms regulate the interaction between these organelles.
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Affiliation(s)
- Jacky G Goetz
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver V6T 1Z3, Canada
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31
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Borgese N, Francolini M, Snapp E. Endoplasmic reticulum architecture: structures in flux. Curr Opin Cell Biol 2006; 18:358-64. [PMID: 16806883 PMCID: PMC4264046 DOI: 10.1016/j.ceb.2006.06.008] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2006] [Accepted: 06/07/2006] [Indexed: 12/12/2022]
Abstract
The endoplasmic reticulum (ER) is a dynamic pleiomorphic organelle containing continuous but distinct subdomains. The diversity of ER structures parallels its many functions, including secretory protein biogenesis, lipid synthesis, drug metabolism and Ca2+ signaling. Recent studies are revealing how elaborate ER structures arise in response to subtle changes in protein levels, dynamics, and interactions as well as in response to alterations in cytosolic ion concentrations. Subdomain formation appears to be governed by principles of self-organization. Once formed, ER subdomains remain malleable and can be rapidly transformed into alternative structures in response to altered conditions. The mechanisms that modulate ER structure are likely to be important for the generation of the characteristic shapes of other organelles.
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Affiliation(s)
- Nica Borgese
- National Research Council Institute for Neuroscience and Department of Medical Pharmacology, University of Milan, via Vanvitelli 32, 20129 Milano, Italy.
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