1
|
Christensen SB, Simonsen HT, Engedal N, Nissen P, Møller JV, Denmeade SR, Isaacs JT. From Plant to Patient: Thapsigargin, a Tool for Understanding Natural Product Chemistry, Total Syntheses, Biosynthesis, Taxonomy, ATPases, Cell Death, and Drug Development. PROGRESS IN THE CHEMISTRY OF ORGANIC NATURAL PRODUCTS 2021; 115:59-114. [PMID: 33797641 DOI: 10.1007/978-3-030-64853-4_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Thapsigargin, the first representative of the hexaoxygenated guaianolides, was isolated 40 years ago in order to understand the skin-irritant principles of the resin of the umbelliferous plant Thapsia garganica. The pronounced cytotoxicity of thapsigargin is caused by highly selective inhibition of the intracellular sarco-endoplasmic Ca2+-ATPase (SERCA) situated on the membrane of the endo- or sarcoplasmic reticulum. Thapsigargin is selective to the SERCA pump and to a minor extent the secretory pathway Ca2+/Mn2+ ATPase (SPCA) pump. Thapsigargin has become a tool for investigation of the importance of SERCA in intracellular calcium homeostasis. In addition, complex formation of thapsigargin with SERCA has enabled crystallization and structure determination of calcium-free states by X-ray crystallography. These results led to descriptions of the mechanism of action and kinetic properties of SERCA and other ATPases. Inhibition of SERCA depletes Ca2+ from the sarco- and endoplasmic reticulum provoking the unfolded protein response, and thereby has enabled new studies on the mechanism of cell death. Development of protocols for selective transformation of thapsigargin disclosed the chemistry and facilitated total synthesis of the molecule. Conversion of trilobolide into thapsigargin offered an economically feasible sustainable source of thapsigargin, which enables a future drug production. Principles for prodrug development were used by conjugating a payload derived from thapsigargin with a hydrophilic peptide selectively cleaved by proteases in the tumor. Mipsagargin was developed in order to obtain a drug for treatment of cancer diseases characterized by the presence of prostate specific membrane antigen (PSMA) in the neovascular tissue of the tumors. Even though mipsagargin showed interesting clinical effects the results did not encourage funding and consequently the attempt to register the drug has been abandoned. In spite of this disappointing fact, the research performed to develop the drug has resulted in important scientific discoveries concerning the chemistry, biosynthesis and biochemistry of sesquiterpene lactones, the mechanism of action of ATPases including SERCA, mechanisms for cell death caused by the unfolded protein response, and the use of prodrugs for cancer-targeting cytotoxins. The presence of toxins in only some species belonging to Thapsia also led to a major revision of the taxonomy of the genus.
Collapse
Affiliation(s)
- Søren Brøgger Christensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark.
| | - Henrik Toft Simonsen
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, Bld 223, 2800, Kgs. Lyngby, Denmark
| | - Nikolai Engedal
- Department of Tumor Biology, Institute for Cancer Research, University Hospital, Montebello, 0379, Oslo, Norway
| | - Poul Nissen
- Department of Molecular Biology and Genetics, Danish Research Institute of Translational Neuroscience - DANDRITE, Nordic EMBL Partnership for Molecular Medicine, Aarhus University, Gustav Wieds Vej 10C, 8000, Aarhus C, Denmark
| | - Jesper Vuust Møller
- Department of Biomedicine, Aarhus University, Ole Worms Allé 3, Bld 1182, Room 114, 8000, Aarhus C, Denmark
| | - Samuel R Denmeade
- Department of Oncology, Prostate Cancer Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Maryland, The Johns Hopkins University School of Medicine, Baltimore, The Bunting-Blaustein Cancer Research Building, 1650 Orleans Street, Baltimore, MD, 21231, USA
| | - John T Isaacs
- Department of Oncology, Prostate Cancer Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Maryland, The Johns Hopkins University School of Medicine, Baltimore, The Bunting-Blaustein Cancer Research Building, 1650 Orleans Street, Baltimore, MD, 21231, USA
| |
Collapse
|
2
|
Indu S, Kaliappan KP. A new and informative [a,b,c,d] nomenclature for one-pot multistep transformations: a simple tool to measure synthetic efficiency. RSC Adv 2018; 8:21292-21305. [PMID: 35557999 PMCID: PMC9088519 DOI: 10.1039/c8ra03338b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 06/04/2018] [Indexed: 01/03/2023] Open
Abstract
Domino, cascade and tandem reactions constitute the most efficient and creative chemical transformations with a huge domain of synthetic utility and applications. A number of reactions may be achieved in a single pot, accompanied by the formation of new rings and new bonds, leading towards higher molecular complexity. A lack of one unified, yet informative descriptor often understates the synthetic ingenuity of certain highly creative transformations. In this review, we propose a new tetra-coordinated [a,b,c,d] nomenclature which takes into account and displays the basic parameters which generally indicate the level of efficiency of a chemical transformation. An almost exhaustive set of one-pot multistep reactions may be described by this system and this review is an attempt to display the one-pot multistep transformations reported from our group and to classify them based on our proposed descriptor.
Collapse
Affiliation(s)
- Satrajit Indu
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai-400076 India
| | - Krishna P Kaliappan
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai-400076 India
| |
Collapse
|
3
|
Cole JT, Kean WS, Pollard HB, Verma A, Watson WD. Glucose-6-phosphate reduces calcium accumulation in rat brain endoplasmic reticulum. Front Mol Neurosci 2012; 5:51. [PMID: 22529775 PMCID: PMC3330244 DOI: 10.3389/fnmol.2012.00051] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 04/01/2012] [Indexed: 12/01/2022] Open
Abstract
Brain cells expend large amounts of energy sequestering calcium (Ca2+), while loss of Ca2+ compartmentalization leads to cell damage or death. Upon cell entry, glucose is converted to glucose-6-phosphate (G6P), a parent substrate to several metabolic major pathways, including glycolysis. In several tissues, G6P alters the ability of the endoplasmic reticulum (ER) to sequester Ca2+. This led to the hypothesis that G6P regulates Ca2+ accumulation by acting as an endogenous ligand for sarco-endoplasmic reticulum calcium ATPase (SERCA). Whole brain ER microsomes were pooled from adult male Sprague-Dawley rats. Using radio-isotopic assays, 45Ca2+ accumulation was quantified following incubation with increasing amounts of G6P, in the presence or absence of thapsigargin, a potent SERCA inhibitor. To qualitatively assess SERCA activity, the simultaneous release of inorganic phosphate (Pi) coupled with Ca2+ accumulation was quantified. Addition of G6P significantly and decreased Ca2+ accumulation in a dose-dependent fashion (1–10 mM). The reduction in Ca2+ accumulation was not significantly different that seen with addition of thapsigargin. Addition of glucose-1-phosphate or fructose-6-phosphate, or other glucose metabolic pathway intermediates, had no effect on Ca2+ accumulation. Further, the release of Pi was markedly decreased, indicating G6P-mediated SERCA inhibition as the responsible mechanism for reduced Ca2+ uptake. Simultaneous addition of thapsigargin and G6P did decrease inorganic phosphate in comparison to either treatment alone, which suggests that the two treatments have different mechanisms of action. Therefore, G6P may be a novel, endogenous regulator of SERCA activity. Additionally, pathological conditions observed during disease states that disrupt glucose homeostasis, may be attributable to Ca2+ dystasis caused by altered G6P regulation of SERCA activity.
Collapse
Affiliation(s)
- Jeffrey T Cole
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda MD, USA
| | | | | | | | | |
Collapse
|
4
|
McMullen DC, Kean WS, Verma A, Cole JT, Watson WD. A microplate technique to simultaneously assay calcium accumulation in endoplasmic reticulum and SERCA release of inorganic phosphate. Biol Proced Online 2012; 14:4. [PMID: 22472432 PMCID: PMC3388579 DOI: 10.1186/1480-9222-14-4] [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] [Received: 01/12/2012] [Accepted: 04/02/2012] [Indexed: 01/02/2023] Open
Abstract
Traditional analyses of calcium homeostasis have separately quantified either calcium accumulation or release mechanisms. To define the system as a whole, however, requires multiple experimental techniques to examine both accumulation and release. Here we describe a technique that couples the simultaneous quantification of radio-labeled calcium accumulation in endoplasmic reticulum (ER) microsomes with the release of inorganic phosphate (Pi) by the hydrolytic activity of sarco-endoplasmic reticulum calcium ATPase (SERCA) all in the convenience of a 96-well format.
Collapse
Affiliation(s)
- David C McMullen
- Department of Neurology, Uniformed Services University of the Health Sciences, B-3059, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
| | | | | | | | | |
Collapse
|
5
|
Zhou X, Wu W, Liu X, Lee CS. Base-Catalyzed Diels−Alder Reactions of 2H-Pyran-2,5-diones: A Mild Approach to Basiliolide B. Org Lett 2008; 10:5525-8. [DOI: 10.1021/ol8022787] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xiongfei Zhou
- Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School of Peking University, Shenzhen University Town, Xili, Shenzhen 518055, China
| | - Wanqing Wu
- Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School of Peking University, Shenzhen University Town, Xili, Shenzhen 518055, China
| | - Xiaozu Liu
- Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School of Peking University, Shenzhen University Town, Xili, Shenzhen 518055, China
| | - Chi-Sing Lee
- Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School of Peking University, Shenzhen University Town, Xili, Shenzhen 518055, China
| |
Collapse
|
6
|
Malviya AN, Klein C. Mechanism regulating nuclear calcium signalingThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell. Can J Physiol Pharmacol 2006; 84:403-22. [PMID: 16902586 DOI: 10.1139/y05-130] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although the outer nuclear membrane is continuous with the endoplasmic reticulum, it is possible to isolate nuclei both intact and free from endoplasmic reticulum contaminants. The outer and the inner nuclear membranes can be purified free from cross-contamination. Evidence in support of autonomous regulation of nuclear calcium signaling relies upon the investigations with isolated nuclei. Mechanisms for generating calcium signaling in the nucleus have been identified. Two calcium transporting systems, an ATP-dependant nuclear Ca2+-ATPase and an IP4-mediated inositol 1,3,4,5-tetrakisphosphate receptor, are located on the outer nuclear membrane. Thus, ATP and IP4, depending on external free calcium concentrations, are responsible for filling the nuclear envelope calcium pool. The inositol 1,4,5-trisphosphate receptor is located on the inner nuclear membrane with its ligand binding domain facing toward the nucleoplasm. Likewise, the ryanodine receptor is located on the inner nuclear membrane and its ligand cADP-ribose is generated within the nucleus. A 120 kDa protein fragment of nuclear PLC-γ1 is stimulated in vivo by epidermal growth factor nuclear signaling coincident with the time course of nuclear membrane epidermal growth factor receptor activation. Stimulated 120 kDa protein fragment interacts with PIKE, a nuclear GTPase, and together they form a complex with PI[3]kinase serving as a module for nuclear PI[3]K stimulation. Thus, the nucleus has its own IP3generating system.
Collapse
|
7
|
Laporte R, Hui A, Laher I. Pharmacological modulation of sarcoplasmic reticulum function in smooth muscle. Pharmacol Rev 2005; 56:439-513. [PMID: 15602008 DOI: 10.1124/pr.56.4.1] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The sarco/endoplasmic reticulum (SR/ER) is the primary storage and release site of intracellular calcium (Ca2+) in many excitable cells. The SR is a tubular network, which in smooth muscle (SM) cells distributes close to cellular periphery (superficial SR) and in deeper aspects of the cell (deep SR). Recent attention has focused on the regulation of cell function by the superficial SR, which can act as a buffer and also as a regulator of membrane channels and transporters. Ca2+ is released from the SR via two types of ionic channels [ryanodine- and inositol 1,4,5-trisphosphate-gated], whereas accumulation from thecytoplasm occurs exclusively by an energy-dependent sarco-endoplasmic reticulum Ca2+-ATPase pump (SERCA). Within the SR, Ca2+ is bound to various storage proteins. Emerging evidence also suggests that the perinuclear portion of the SR may play an important role in nuclear transcription. In this review, we detail the pharmacology of agents that alter the functions of Ca2+ release channels and of SERCA. We describe their use and selectivity and indicate the concentrations used in investigating various SM preparations. Important aspects of cell regulation and excitation-contractile activity coupling in SM have been uncovered through the use of such activators and inhibitors of processes that determine SR function. Likewise, they were instrumental in the recent finding of an interaction of the SR with other cellular organelles such as mitochondria. Thus, an appreciation of the pharmacology and selectivity of agents that interfere with SR function in SM has greatly assisted in unveiling the multifaceted nature of the SR.
Collapse
Affiliation(s)
- Régent Laporte
- Ferring Research Institute, Inc., Ferring Pharmaceuticals, San Diego, California, USA
| | | | | |
Collapse
|
8
|
Kaliappan KP, Nandurdikar RS. A facile domino metathetic route to a thapsigargin skeleton. Org Biomol Chem 2005; 3:3613-4. [PMID: 16211096 DOI: 10.1039/b510388f] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A facile synthesis of a 5,7,5-fused ring system that is present in thapsigargins belonging to a novel family of sesquiterpene lactones, guainanolides, using domino enyne-RCM is reported here.
Collapse
Affiliation(s)
- Krishna P Kaliappan
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400 076, India.
| | | |
Collapse
|
9
|
Ley SV, Antonello A, Balskus EP, Booth DT, Christensen SB, Cleator E, Gold H, Högenauer K, Hünger U, Myers RM, Oliver SF, Simic O, Smith MD, Søhoel H, Woolford AJA. Synthesis of the thapsigargins. Proc Natl Acad Sci U S A 2004; 101:12073-8. [PMID: 15226504 PMCID: PMC514437 DOI: 10.1073/pnas.0403300101] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The thapsigargins are a family of complex guaianolides with potent and selective Ca(2+)-modulating properties. This article documents the evolution of a synthetic route through several iterations to a final practical and scaleable synthetic route capable of generating both unnatural and natural products based around the guaianolide skeleton.
Collapse
Affiliation(s)
- Steven V Ley
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Franklin IK, Winz RA, Hubbard MJ. Endoplasmic reticulum Ca2+-ATPase pump is up-regulated in calcium-transporting dental enamel cells: a non-housekeeping role for SERCA2b. Biochem J 2001; 358:217-24. [PMID: 11485570 PMCID: PMC1222050 DOI: 10.1042/0264-6021:3580217] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Dental enamel-forming cells face a major challenge to avoid the cytotoxic effects of excess calcium. We have characterized sarcoplasmic/endoplasmic reticulum calcium-ATPase pumps (SERCA) in rat enamel cells to address the proposal that non-mitochondrial calcium stores play a dominant role in transcellular calcium transport. A single major isoform, SERCA2b, was detected during the protein-secretory and calcium-transport stages of enamel formation using reverse-transcriptase PCR, cDNA cloning, Northern analysis and immunoblotting. Most importantly, SERCA2b exhibited a specific 3-fold up-regulation to high expression levels during calcium transport, as determined by quantitative immunoblotting and ATPase assays. Sensitivity of the calcium-dependent ATPase to thapsigargin and three other SERCA inhibitors was characterized. These findings indicate that enamel cells are well-equipped to sequester calcium in endoplasmic reticulum stores and so protect against calcium toxicity, associate SERCA with transcellular calcium transport for the first time, and establish SERCA2b as a molecular and pharmacological target for future investigations of calcium transcytosis. The observed physiological regulation in enamel cells contradicts the widespread perception that SERCA2b is restricted to general housekeeping duties.
Collapse
Affiliation(s)
- I K Franklin
- Department of Biochemistry, University of Otago, PO Box 56, 710 Cumberland Street, Dunedin, New Zealand
| | | | | |
Collapse
|
11
|
Caspersen C, Pedersen PS, Treiman M. The sarco/endoplasmic reticulum calcium-ATPase 2b is an endoplasmic reticulum stress-inducible protein. J Biol Chem 2000; 275:22363-72. [PMID: 10748035 DOI: 10.1074/jbc.m001569200] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The sarco/endoplasmic reticulum calcium-ATPase (SERCA) translocates Ca(2+) from the cytosol to the lumen of the endoplasmic reticulum. This Ca(2+) storage is important for cellular processes such as calcium signaling and endoplasmic reticulum (ER)-associated posttranslational protein modifications. We investigated the expression of the SERCA2 and SERCA3 isozymes in PC12 cells exposed to agents interfering with different aspects of the posttranslational protein processing within the ER, thereby activating the ER stress-induced unfolded protein response (UPR). All agents increased the SERCA2b mRNA level 3-4-fold, in parallel with increasing mRNA levels for the ER stress marker proteins BiP/GRP78 and CHOP/GADD153. In contrast, SERCA3 mRNA levels did not change. SERCA2b mRNA stability was not changed, indicating that the mechanism of its up-regulation was transcriptional, in accordance with the presence of ER stress response elements in the promoter region of the SERCA2 gene. SERCA2b was also increased at the protein level upon ER stress treatments. Induction of ER stress by tunicamycin, dithiothreitol, or l-azetidine 2-carboxylic acid did not result in depletion of ER calcium, showing that such depletion was not necessary for up-regulation of SERCA2b expression or UPR activation in general. We conclude that the SERCA2b expression can be controlled by the UPR pathway independently of ER Ca(2+) depletion.
Collapse
Affiliation(s)
- C Caspersen
- Department of Medical Physiology and the Biotechnology Center for Cellular Communication, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark
| | | | | |
Collapse
|
12
|
Doutheil J, Althausen S, Treiman M, Paschen W. Effect of nitric oxide on endoplasmic reticulum calcium homeostasis, protein synthesis and energy metabolism. Cell Calcium 2000; 27:107-15. [PMID: 10756977 DOI: 10.1054/ceca.1999.0099] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It has been suggested that nitric oxide (NO) may contribute to ischemia-induced cell injury. However, the mechanisms underlying NO toxicity have not yet been fully elucidated. In the present study, we investigated the effect of NO on the level of endoplasmic reticulum (ER) calcium stores, on ER Ca2+ pump activity, on protein synthesis, on concentrations of high-energy phosphates, and on gadd153 mRNA levels. Primary neuronal cells were exposed to the NO-donor (+/-)-S-Nitroso-N-acetylpenicillamine (SNAP) for 1 h, 2 h, 6 h or 24 h. The level of ER calcium stores was evaluated by measuring the increase in cytoplasmic calcium activity induced by exposing cells to thapsigargin, an irreversible inhibitor of ER Ca(2+)-ATPase; the activity of ER Ca(2+)-ATPase was determined by measuring a phosphorylated intermediate; SNAP-induced changes in gadd153 expression were evaluated by quantitative PCR; SNAP-induced changes in protein synthesis were investigated by measuring the incorporation of L-[4,5-3H]leucine into proteins, and changes in the levels of ATP, ADP, AMP were measured by HPLC. Exposing cells to SNAP for 1 h to 2 h induced a marked depletion of ER calcium stores through an inhibition of ER Ca(2+)-ATPase (to 58% of control), and a concentration-dependent suppression of protein synthesis which was reversed in the presence of hemoglobin, suggesting NO-related effects. ATP levels and adenylate energy charge were significantly decreased only when cells were exposed to the highest SNAP concentration for 6 h or 24 h, excluding significant effects of NO on the energy state of cells in the acute state, i.e. when ER calcium stores were already completely depleted and protein synthesis severely suppressed. In light of the regulatory role of ER calcium homeostasis in the control of protein synthesis, the results imply that the suppression of protein synthesis resulted from NO-induced inhibition of ER Ca(2+)-ATPase and depletion of ER calcium stores, and that NO-induced disturbances of energy metabolism are secondary to the effect of NO on ER calcium homeostasis. It is, therefore, concluded that ER calcium stores are a primary target of NO-toxicity.
Collapse
Affiliation(s)
- J Doutheil
- Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Cologne, Germany
| | | | | | | |
Collapse
|
13
|
Doutheil J, Treiman M, Oschlies U, Paschen W. Recovery of neuronal protein synthesis after irreversible inhibition of the endoplasmic reticulum calcium pump. Cell Calcium 1999; 25:419-28. [PMID: 10579053 DOI: 10.1054/ceca.1999.0042] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In the physiological state, protein synthesis is controlled by calcium homeostasis in the endoplasmic reticulum (ER). Recently, evidence has been presented that dividing cells can adapt to an irreversible inhibition of the ER calcium pump (SERCA), although the mechanisms underlying this adaption have not yet been elucidated. Exposing primary neuronal cells to thapsigargin (Tg, a specific irreversible inhibition of SERCA) resulted in a complete suppression of protein synthesis and disaggregation of polyribosomes indicating inhibition of the initiation step of protein synthesis. Protein synthesis and ribosomal aggregation recovered to 50-70% of control when cells were cultured in medium supplemented with serum for 24 h, but recovery was significantly suppressed in a serum-free medium. Culturing cells in serum-free medium for 24 h already caused an almost 50% suppression of SERCA activity and protein synthesis. SERCA activity did not recover after Tg treatment, and a second exposure of cells to Tg, 24 h after the first, had no effect on protein synthesis. Acute exposure of neurons to Tg induced a depletion of ER calcium stores as indicated by an increase in cytoplasmic calcium activity, but this response was not elicited by the same treatment 24 h later. However, treatments known to deplete ER calcium stores (exposure to the ryanodine receptor agonists caffeine or 2-hydroxycarbazole, or incubating cells in calcium-free medium supplemented with EGTA) caused a second suppression of protein synthesis when applied 24 h after Tg treatment. The results suggest that after Tg exposure, restoration of protein synthesis was induced by recovery of the regulatory link between ER calcium homeostasis and protein synthesis, and not by renewed synthesis of SERCA protein or development of a new regulatory system for the control of protein synthesis. The effect of serum withdrawal on SERCA activity and protein synthesis points to a role of growth factors in maintaining ER calcium homeostasis, and suggests that the ER acts as a mediator of cell damage after interruption of growth factor supplies.
Collapse
Affiliation(s)
- J Doutheil
- Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Cologne, Germany
| | | | | | | |
Collapse
|
14
|
Feher JJ, Lee KN, Wu QY. Ryanodine-sensitive, thapsigargin-insensitive calcium uptake in rat ventricle homogenates. Mol Cell Biochem 1998; 189:9-17. [PMID: 9879648 DOI: 10.1023/a:1006800328118] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Thapsigargin is a natural product that specifically inhibits all known SERCA calcium pumps with high affinity. We investigated the effects of thapsigargin on cardiac sarcoplasmic reticulum (SR) by measuring the oxalate-supported calcium uptake rate in the unfractionated homogenate and in the isolated SR fraction. The uptake rate in both the isolated SR and unfractionated homogenate are stimulated about two-fold by preincubation with high concentrations of ryanodine, which closes the SR efflux channel. Thapsigargin stoichiometrically and completely inhibited the calcium uptake rate in the isolated SR, both in the presence and absence of SR channel blockade. In contrast, thapsigargin nearly completely inhibited the homogenate calcium uptake only in the absence of SR channel blockade; in the presence of blockade, about 20% of the uptake activity was insensitive to thapsigargin. This result unmasks a thapsigargin-insensitive, ryanodine-sensitive component of calcium uptake in the heart. This activity is in an oxalate-permeable pool and is inhibited by cyclopiazonic acid, another inhibitor of the SERCA calcium pumps. There was no TG-insensitive activity in the rat EDL muscle homogenate. The absence of thapsigargin-insensitive uptake activity in the isolated SR can be attributed to its inactivation during the isolation of the SR. The oxalate permeability and ryanodine sensitivity suggest that the TG-insensitive calcium uptake activity is closely related to the classical SR. The different thapsigargin sensitivities suggests the existence of two kinds of intracellular calcium pumps in the heart.
Collapse
Affiliation(s)
- J J Feher
- Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0551, USA
| | | | | |
Collapse
|
15
|
Kissmehl R, Huber S, Kottwitz B, Hauser K, Plattner H. Subplasmalemmal Ca-stores in Paramecium tetraurelia. Identification and characterisation of a sarco(endo)plasmic reticulum-like Ca(2+)-ATPase by phosphoenzyme intermediate formation and its inhibition by caffeine. Cell Calcium 1998; 24:193-203. [PMID: 9883273 DOI: 10.1016/s0143-4160(98)90128-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Considering increasing interest in calcium stores in protozoa, including parasitic forms, and specifically in subplasmalemmal stores in higher eukaryotes, we have isolated subplasmalemmal calcium stores (alveolar sacs) from the ciliated protozoan, Paramecium tetraurelia. Using antibodies against established sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCAs) we detected in Western blots of subcellular fractions a band of approximately 106 kDa size selectively in alveolar sacs--but not, for example, in plasma membranes--and concomitant restriction of immunofluorecence labelling to the cell cortex of permeabilised cells. These results are the same as with ABs against a peptide derived from a cloned SERCA-like gene from Paramecium [Hauser K., Pavlovic N., Kissmehl R., Plattner H. Molecular characterization of a sarco(endo)plasmic reticulum Ca(2+)-ATPase gene from Paramecium tetraurelia and localisation of its gene product to subplasmalemmal calcium stores. Biochem J 1998; 334: 31-38]. When such isolated alveolar sacs were now tested for phosphoenzyme intermediate (EP) formation, a phosphoprotein of the same apparent molecular mass (approximately 106 kDa) as in blots could be identified in gel autoradiograms. This EP corresponds to that formed in the reaction cycle of different SERCA-types, with dependency on Ca2+ and Mg2+, sensitivity to La3+ or insensitivity towards calmodulin, calmodulin antagonists and vanadate. However, EP formation in alveolar sacs is not inhibited by established SERCA inhibitors (e.g. thapsigargi[ci]n tested up to 100 microM). Surprisingly, caffeine, which is frequently used to mobilise Ca2+ from intracellular stores, strongly inhibits EP formation. In parallel experiments, we did not find any similar effect with sarcoplasmic reticulum isolated from skeletal muscle. We conclude that the approximately 106 kDa protein of alveolar sacs in Paramecium may represent a SERCA-like Ca(2+)-ATPase with some unorthodox features, which might be relevant also for some other protozoan systems. In this case, the established Ca(2+)-mobilizing effect of caffeine may be amplified by inhibiting store refilling.
Collapse
Affiliation(s)
- R Kissmehl
- Department of Biology, University of Konstanz, Germany
| | | | | | | | | |
Collapse
|
16
|
Rogue PJ, Humbert JP, Meyer A, Freyermuth S, Krady MM, Malviya AN. cAMP-dependent protein kinase phosphorylates and activates nuclear Ca2+-ATPase. Proc Natl Acad Sci U S A 1998; 95:9178-83. [PMID: 9689054 PMCID: PMC21312 DOI: 10.1073/pnas.95.16.9178] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
A Ca2+-pump ATPase, similar to that in the endoplasmic reticulum, has been located on the outer membrane of rat liver nuclei. The effect of cAMP-dependent protein kinase (PKA) on nuclear Ca2+-ATPase (NCA) was studied by using purified rat liver nuclei. Treatment of isolated nuclei with the catalytic unit of PKA resulted in the phosphorylation of a 105-kDa band that was recognized by antibodies specific for sarcoplasmic reticulum Ca2+-ATPase type 2b. Partial purification and immunoblotting confirmed that the 105-kDa protein band phosphorylated by PKA is NCA. The stoichiometry of phosphorylation was 0.76 mol of phosphate incorporated/mol of partially purified enzyme. Measurement of ATP-dependent 45Ca2+ uptake into purified nuclei showed that PKA phosphorylation enhanced the Ca2+-pumping activity of NCA. We show that PKA phosphorylation of Ca2+-ATPase enhances the transport of 10-kDa fluorescent-labeled dextrans across the nuclear envelope. The findings reported in this paper are consistent with the notion that the crosstalk between the cAMP/PKA- and Ca2+-dependent signaling pathways identified at the cytoplasmic level extends to the nucleus. Furthermore, these data support a function for crosstalk in the regulation of calcium-dependent transport across the nuclear envelope.
Collapse
Affiliation(s)
- P J Rogue
- Laboratoire de Neurobiologie Moléculaire des Interactions Cellulaires, UPR 416 du Centre National de la Recherche Scientifique, 5 rue Blaise Pascal, 67084 Strasbourg, France
| | | | | | | | | | | |
Collapse
|
17
|
Treiman M, Caspersen C, Christensen SB. A tool coming of age: thapsigargin as an inhibitor of sarco-endoplasmic reticulum Ca(2+)-ATPases. Trends Pharmacol Sci 1998; 19:131-5. [PMID: 9612087 DOI: 10.1016/s0165-6147(98)01184-5] [Citation(s) in RCA: 470] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Thapsigargin is the most widely used inhibitor of the ubiquitous sarco-endoplasmic reticulum Ca(2+)-ATPases in mammalian cells. Over the past ten years, this guaianolide compound of plant origin has become a popular tool in a host of studies directed at elucidating the mechanisms of intracellular Ca2+ signalling. Its remarkable potency and selectivity have been instrumental in widening our view of the function of intracellular Ca2+ stores to include such key aspects as store-operated Ca2+ entry or the involvement of the stores in protein synthesis or cell growth. In this article Marek Treiman, Casper Caspersen and Søren Brøgger Christensen review the key pharmacological features of thapsigargin action; they also discuss some of the ways in which its unique properties have shown to be important for obtaining new insights into the biology of Ca2+ stores, and how these properties might encompass a therapeutic potential. In parallel, attention is drawn to some of the limitations and pitfalls encountered when working with thapsigargin.
Collapse
Affiliation(s)
- M Treiman
- Department of Medical Physiology, Panum Institute, Copenhagen, Denmark
| | | | | |
Collapse
|
18
|
Salvador JM, Mata AM. Characterization of the intracellular and the plasma membrane Ca2+-ATPases in fractionated pig brain membranes using calcium pump inhibitors. Arch Biochem Biophys 1998; 351:272-8. [PMID: 9514660 DOI: 10.1006/abbi.1997.0562] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Ca2+-ATPase activity of isolated membranes and purified plasma membrane ATPase from pig brain was measured in the presence of specific inhibitors. The inhibition of the enzymatic activity by vanadate presents a lower affinity in microsomes than in the synaptic plasma membrane vesicles, showing K0.5 of 0.4 and 0.2 microM, respectively. The purified enzyme showed a higher sensitivity to vanadate with a K0.5 of 0.10 microM. Thapsigargin (Tg) and 2,5-di(tert-butyl)-1,4-benzohydroquinone (BHQ) were stronger inhibitors of the Ca2+-ATPase activity in microsomes than in the synaptic membrane vesicles. The activity of the purified enzyme was not affected by Tg and only partially by BHQ. Cyclopiazonic acid inhibited the enzymatic activity in all fractions, being more sensitive in microsomes. The microsome preparation incorporated 32P from [gamma-32P]ATP into two main proteins that appear at approx 110,000 and 140,000. According to the inhibition pattern, the lower phosphorylated band was identified as the sarco(endo)plasmic reticulum Ca2+-ATPase, being in a higher percentage than the upper band. Synaptic membrane vesicles also incorporated radioactive 32P into two protein bands. The 140,000 protein (upper band) shows the typical behavior of the purified plasma membrane Ca2+-ATPase, being more abundant in this preparation than the organellar Ca2+-pump (lower band). This study highlights the heterogeneous nature of the Ca2+-ATPase activity measured in brain membrane fractions.
Collapse
Affiliation(s)
- J M Salvador
- Facultad de Ciencias, Universidad de Extremadura, Badajoz, 06071, Spain
| | | |
Collapse
|
19
|
Wells KM, Abercrombie RF. Luminal Ca2+ protects against thapsigargin inhibition in neuronal endoplasmic reticulum. J Biol Chem 1998; 273:5020-5. [PMID: 9478950 DOI: 10.1074/jbc.273.9.5020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Thapsigargin is a specific and potent inhibitor of sarco/endoplasmic reticulum Ca2+-ATPases. However, in whole rat brain microsomes, 1 microM thapsigargin had no significant effect on the 10-min time course of ATP-dependent Ca2+ uptake in the absence of the luminal Ca2+ chelator oxalate. In contrast, 50 mM oxalate resolved a thapsigargin-sensitive Ca2+ uptake rate (IC50 approximately 1 nM thapsigargin) five times that of a thapsigargin-insensitive rate. This remaining approximately 20% of the total ATP-dependent accumulation was insensitive to thapsigargin (up to 10 microM), slightly less sensitive to vanadate inhibition, and unresponsive to 5 microM inositol 1,4,5-trisphosphate or 10 mM caffeine. Measuring both 12-min Ca2+ uptake and initial Ca2+ uptake rates, the apparent thapsigargin sensitivity increased as oxalate concentrations increased from 10 to 50 mM, corresponding to a range of luminal free Ca2+ concentrations of approximately 300 down to 60 nM. Addition of oxalate during steady-state 45Ca accumulation rapidly resolved the aforementioned thapsigargin sensitivity. These results strongly suggest that luminal Ca2+ may protect a large portion of neuronal endoplasmic reticulum Ca2+ pumps against thapsigargin inhibition. Although high [Ca2+] has been previously shown to protect against thapsigargin inhibition in several reticular membrane preparations, our results suggest that luminal Ca2+ alone is responsible for mediating this effect in neurons.
Collapse
Affiliation(s)
- K M Wells
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | |
Collapse
|
20
|
Pezzati R, Bossi M, Podini P, Meldolesi J, Grohovaz F. High-resolution calcium mapping of the endoplasmic reticulum-Golgi-exocytic membrane system. Electron energy loss imaging analysis of quick frozen-freeze dried PC12 cells. Mol Biol Cell 1997; 8:1501-12. [PMID: 9285821 PMCID: PMC276172 DOI: 10.1091/mbc.8.8.1501] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The calcium pools segregated within the endoplasmic reticulum, Golgi complex, exocytic, and other organelles are believed to participate in the regulation of a variety of cell functions. Until now, however, the precise intracellular distribution of the element had not been established. Here, we report about the first high-resolution calcium mapping obtained in neurosecretory PC12 cells by the imaging mode of the electron energy loss spectroscopy technique. The preparation procedure used included quick freezing of cell monolayers, followed by freeze-drying, fixation with OSO4 vapors, resin embedding, and cutting of very thin sections. Conventional electron microscopy and high-resolution immunocytochemistry revealed a high degree of structural preservation, a condition in which inorganic elements are expected to maintain their native distribution. Within these cells, calcium signals of nucleus, cytosol, and most mitochondria remained below detection, whereas in other organelles specific patterns were identified. In the endoplasmic reticulum, the distribution was heterogeneous with strongly positive cisternae (more often the nuclear envelope and stacks of parallel elements that are frequent in quick frozen preparations) lying in the proximity of or even in direct continuity with other, apparently negative cisternae. The Golgi complexes were labeled strongly and uniformly in all cisternae and part of their vesicles, with no appreciable differences along the cis-trans axis. Weaker or negative signals were recorded from the trans-Golgi network elements and from scattered vesicles, whereas in contrast secretion granules were strongly positive for calcium. These results are discussed in relation to the existing knowledge about the mechanisms of calcium transport in the variations organelles, and about the processes and functions regulated by organelle lumenal calcium in eukaryotic cells.
Collapse
Affiliation(s)
- R Pezzati
- Consiglio Nazionale delle Ricerche, Cellular and Molecular Pharmacology Center, Milan, Italy
| | | | | | | | | |
Collapse
|
21
|
Rooney E, Meldolesi J. The endoplasmic reticulum in PC12 cells. Evidence for a mosaic of domains differently specialized in Ca2+ handling. J Biol Chem 1996; 271:29304-11. [PMID: 8910591 DOI: 10.1074/jbc.271.46.29304] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Velocity and isopycnic gradient centrifugation were employed to fractionate post-nuclear supernatants rapidly prepared from PC12 cells in order to characterize areas of the endoplasmic reticulum involved in various aspects of intracellular Ca2+ homeostasis. The endoplasmic reticulum Ca2+ pumping activity, defined by three properties studied in parallel in the isolated fractions; thapsigargin-sensitive uptake of 45Ca2+, Ca2+-dependent, thapsigargin-sensitive protein phosphorylation and Western blotting of sarcoplasmic reticulum calcium ATPase (SERCA) 2b and putative SERCA3 ATPases, was concentrated primarily in a few fractions located at the top and toward the bottom of velocity and isopycnic gradients, respectively. The endoplasmic reticulum Ca2+ release channel, the inositol 1,4,5-trisphosphate receptor, was concentrated in the same fractions as the Ca2+ pumps, and additionally in a few fractions distinctly poor in SERCAs. In contrast, two lumenal markers (protein disulfide isomerase and calreticulin, the major Ca2+ storage protein of non-muscle endoplasmic reticulum) were enriched in the middle fractions of the velocity gradients while calnexin, a Ca2+-binding membrane protein, was more widely distributed throughout the gradients. These results document a considerable degree of functional and compositional heterogeneity in the endoplasmic reticulum of neurosecretory PC12 cells. Even in the limited areas that appear specialized for rapid Ca2+ uptake and release the ratio between pumps and channels varies considerably. Within the rest of the system, insulated from short-term fluctuations of Ca2+ concentration, Ca2+-binding proteins appear to be extensively distributed, in agreement with the idea that the Ca2+ content of the endoplasmic reticulum serves multiple functions.
Collapse
Affiliation(s)
- E Rooney
- Department of Pharmacology and B. Ceccarelli Centre, University of Milan, the CNR Centre of Molecular and Cellular Pharmacology, Milano, Italy
| | | |
Collapse
|