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Michalak M. Calreticulin: Endoplasmic reticulum Ca 2+ gatekeeper. J Cell Mol Med 2024; 28:e17839. [PMID: 37424156 PMCID: PMC10902585 DOI: 10.1111/jcmm.17839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/21/2023] [Accepted: 06/27/2023] [Indexed: 07/11/2023] Open
Abstract
Endoplasmic reticulum (ER) luminal Ca2+ is vital for the function of the ER and regulates many cellular processes. Calreticulin is a highly conserved, ER-resident Ca2+ binding protein and lectin-like chaperone. Over four decades of studying calreticulin demonstrate that this protein plays a crucial role in maintaining Ca2+ supply under different physiological conditions, in managing access to Ca2+ and how Ca2+ is used depending on the environmental events and in making sure that Ca2+ is not misused. Calreticulin plays a role of ER luminal Ca2+ sensor to manage Ca2+-dependent ER luminal events including maintaining interaction with its partners, Ca2+ handling molecules, substrates and stress sensors. The protein is strategically positioned in the lumen of the ER from where the protein manages access to and distribution of Ca2+ for many cellular Ca2+-signalling events. The importance of calreticulin Ca2+ pool extends beyond the ER and includes influence of cellular processes involved in many aspects of cellular pathophysiology. Abnormal handling of the ER Ca2+ contributes to many pathologies from heart failure to neurodegeneration and metabolic diseases.
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Affiliation(s)
- Marek Michalak
- Department of BiochemistryUniversity of AlbertaEdmontonAlbertaCanada
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2
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Marabelli C, Santiago DJ, Priori SG. The Structural-Functional Crosstalk of the Calsequestrin System: Insights and Pathological Implications. Biomolecules 2023; 13:1693. [PMID: 38136565 PMCID: PMC10741413 DOI: 10.3390/biom13121693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/14/2023] [Accepted: 11/21/2023] [Indexed: 12/24/2023] Open
Abstract
Calsequestrin (CASQ) is a key intra-sarcoplasmic reticulum Ca2+-handling protein that plays a pivotal role in the contraction of cardiac and skeletal muscles. Its Ca2+-dependent polymerization dynamics shape the translation of electric excitation signals to the Ca2+-induced contraction of the actin-myosin architecture. Mutations in CASQ are linked to life-threatening pathological conditions, including tubular aggregate myopathy, malignant hyperthermia, and Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT). The variability in the penetrance of these phenotypes and the lack of a clear understanding of the disease mechanisms associated with CASQ mutations pose a major challenge to the development of effective therapeutic strategies. In vitro studies have mainly focused on the polymerization and Ca2+-buffering properties of CASQ but have provided little insight into the complex interplay of structural and functional changes that underlie disease. In this review, the biochemical and structural natures of CASQ are explored in-depth, while emphasizing their direct and indirect consequences for muscle Ca2+ physiology. We propose a novel functional classification of CASQ pathological missense mutations based on the structural stability of the monomer, dimer, or linear polymer conformation. We also highlight emerging similarities between polymeric CASQ and polyelectrolyte systems, emphasizing the potential for the use of this paradigm to guide further research.
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Affiliation(s)
- Chiara Marabelli
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy;
- Laboratory of Molecular Cardiology, IRCCS ICS Maugeri, 27100 Pavia, Italy
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain;
| | - Demetrio J. Santiago
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain;
| | - Silvia G. Priori
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy;
- Laboratory of Molecular Cardiology, IRCCS ICS Maugeri, 27100 Pavia, Italy
- Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain;
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3
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Hanna AD, Lee CS, Babcock L, Wang H, Recio J, Hamilton SL. Pathological mechanisms of vacuolar aggregate myopathy arising from a Casq1 mutation. FASEB J 2021; 35:e21349. [PMID: 33786938 DOI: 10.1096/fj.202001653rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 12/15/2020] [Accepted: 12/22/2020] [Indexed: 11/11/2022]
Abstract
Mice with a mutation (D244G, DG) in calsequestrin 1 (CASQ1), analogous to a human mutation in CASQ1 associated with a delayed onset human myopathy (vacuolar aggregate myopathy), display a progressive myopathy characterized by decreased activity, decreased ability of fast twitch muscles to generate force and low body weight after one year of age. The DG mutation causes CASQ1 to partially dissociate from the junctional sarcoplasmic reticulum (SR) and accumulate in the endoplasmic reticulum (ER). Decreased junctional CASQ1 reduces SR Ca2+ release. Muscles from older DG mice display ER stress, ER expansion, increased mTOR signaling, inadequate clearance of aggregated proteins by the proteasomes, and elevation of protein aggregates and lysosomes. This study suggests that the myopathy associated with the D244G mutation in CASQ1 is driven by CASQ1 mislocalization, reduced SR Ca2+ release, CASQ1 misfolding/aggregation and ER stress. The subsequent maladaptive increase in protein synthesis and decreased protein aggregate clearance are likely to contribute to disease progression.
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Affiliation(s)
- Amy D Hanna
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Chang Seok Lee
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Lyle Babcock
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Hui Wang
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Joseph Recio
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Susan L Hamilton
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
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4
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Wang Q, Michalak M. Calsequestrin. Structure, function, and evolution. Cell Calcium 2020; 90:102242. [PMID: 32574906 DOI: 10.1016/j.ceca.2020.102242] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/05/2020] [Accepted: 06/06/2020] [Indexed: 12/25/2022]
Abstract
Calsequestrin is the major Ca2+ binding protein in the sarcoplasmic reticulum (SR), serves as the main Ca2+ storage and buffering protein and is an important regulator of Ca2+ release channels in both skeletal and cardiac muscle. It is anchored at the junctional SR membrane through interactions with membrane proteins and undergoes reversible polymerization with increasing Ca2+ concentration. Calsequestrin provides high local Ca2+ at the junctional SR and communicates changes in luminal Ca2+ concentration to Ca2+ release channels, thus it is an essential component of excitation-contraction coupling. Recent studies reveal new insights on calsequestrin trafficking, Ca2+ binding, protein evolution, protein-protein interactions, stress responses and the molecular basis of related human muscle disease, including catecholaminergic polymorphic ventricular tachycardia (CPVT). Here we provide a comprehensive overview of calsequestrin, with recent advances in structure, diverse functions, phylogenetic analysis, and its role in muscle physiology, stress responses and human pathology.
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Affiliation(s)
- Qian Wang
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6H 2S7, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6H 2S7, Canada.
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5
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Rossi D, Gamberucci A, Pierantozzi E, Amato C, Migliore L, Sorrentino V. Calsequestrin, a key protein in striated muscle health and disease. J Muscle Res Cell Motil 2020; 42:267-279. [PMID: 32488451 DOI: 10.1007/s10974-020-09583-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 10/24/2022]
Abstract
Calsequestrin (CASQ) is the most abundant Ca2+ binding protein localized in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle. The genome of vertebrates contains two genes, CASQ1 and CASQ2. CASQ1 and CASQ2 have a high level of homology, but show specific patterns of expression. Fast-twitch skeletal muscle fibers express only CASQ1, both CASQ1 and CASQ2 are present in slow-twitch skeletal muscle fibers, while CASQ2 is the only protein present in cardiomyocytes. Depending on the intraluminal SR Ca2+ levels, CASQ monomers assemble to form large polymers, which increase their Ca2+ binding ability. CASQ interacts with triadin and junctin, two additional SR proteins which contribute to localize CASQ to the junctional region of the SR (j-SR) and also modulate CASQ ability to polymerize into large macromolecular complexes. In addition to its ability to bind Ca2+ in the SR, CASQ appears also to be able to contribute to regulation of Ca2+ homeostasis in muscle cells. Both CASQ1 and CASQ2 are able to either activate and inhibit the ryanodine receptors (RyRs) calcium release channels, likely through their interactions with junctin and triadin. Additional evidence indicates that CASQ1 contributes to regulate the mechanism of store operated calcium entry in skeletal muscle via a direct interaction with the Stromal Interaction Molecule 1 (STIM1). Mutations in CASQ2 and CASQ1 have been identified, respectively, in patients with catecholamine-induced polymorphic ventricular tachycardia and in patients with some forms of myopathy. This review will highlight recent developments in understanding CASQ1 and CASQ2 in health and diseases.
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Affiliation(s)
- Daniela Rossi
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy.
| | - Alessandra Gamberucci
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Enrico Pierantozzi
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Caterina Amato
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Loredana Migliore
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Vincenzo Sorrentino
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
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Wang Q, Groenendyk J, Paskevicius T, Qin W, Kor KC, Liu Y, Hiess F, Knollmann BC, Chen SRW, Tang J, Chen XZ, Agellon LB, Michalak M. Two pools of IRE1α in cardiac and skeletal muscle cells. FASEB J 2019; 33:8892-8904. [PMID: 31051095 PMCID: PMC6662970 DOI: 10.1096/fj.201802626r] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 04/08/2019] [Indexed: 12/23/2022]
Abstract
The endoplasmic reticulum (ER) plays a central role in cellular stress responses via mobilization of ER stress coping responses, such as the unfolded protein response (UPR). The inositol-requiring 1α (IRE1α) is an ER stress sensor and component of the UPR. Muscle cells also have a well-developed and highly subspecialized membrane network of smooth ER called the sarcoplasmic reticulum (SR) surrounding myofibrils and specialized for Ca2+ storage, release, and uptake to control muscle excitation-contraction coupling. Here, we describe 2 distinct pools of IRE1α in cardiac and skeletal muscle cells, one localized at the perinuclear ER and the other at the junctional SR. We discovered that, at the junctional SR, calsequestrin binds to the ER luminal domain of IRE1α, inhibiting its dimerization. This novel interaction of IRE1α with calsequestrin, one of the highly abundant Ca2+ handling proteins at the junctional SR, provides new insights into the regulation of stress coping responses in muscle cells.-Wang, Q., Groenendyk, J., Paskevicius, T., Qin, W., Kor, K. C., Liu, Y., Hiess, F., Knollmann, B. C., Chen, S. R. W., Tang, J., Chen, X.-Z., Agellon, L. B., Michalak, M. Two pools of IRE1α in cardiac and skeletal muscle cells.
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Affiliation(s)
- Qian Wang
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jody Groenendyk
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | | | - Wenying Qin
- National “111” Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
| | - Kaylen C. Kor
- Division of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Yingjie Liu
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Florian Hiess
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Bjorn C. Knollmann
- Division of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - S. R. Wayne Chen
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Jingfeng Tang
- National “111” Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
| | - Xing-Zhen Chen
- National “111” Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada; and
| | - Luis B. Agellon
- School of Human Nutrition, McGill University, Ste. Anne de Bellevue, Quebec, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
- National “111” Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
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Bal NC, Jena N, Chakravarty H, Kumar A, Chi M, Balaraju T, Rawale SV, Rawale JS, Sharon A, Periasamy M. The C-terminal calcium-sensitive disordered motifs regulate isoform-specific polymerization characteristics of calsequestrin. Biopolymers 2016; 103:15-22. [PMID: 25091206 DOI: 10.1002/bip.22534] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 07/31/2014] [Accepted: 08/01/2014] [Indexed: 12/14/2022]
Abstract
Calsequestrin (CASQ) exists as two distinct isoforms CASQ1 and CASQ2 in all vertebrates. Although the isoforms exhibit unique functional characteristic, the structural basis for the same is yet to be fully defined. Interestingly, the C-terminal region of the two isoforms exhibit significant differences both in length and amino acid composition; forming Dn-motif and DEXn-motif in CASQ1 and CASQ2, respectively. Here, we investigated if the unique C-terminal motifs possess Ca(2+)-sensitivity and affect protein function. Sequence analysis shows that both the Dn- and DEXn-motifs are intrinsically disordered regions (IDRs) of the protein, a feature that is conserved from fish to man. Using purified synthetic peptides, we show that these motifs undergo distinctive Ca(2+)-mediated folding suggesting that these disordered motifs are Ca(2+)-sensitivity. We generated chimeric proteins by swapping the C-terminal portions between CASQ1 and CASQ2. Our studies show that the C-terminal portions do not play significant role in protein folding. An interesting finding of the current study is that the switching of the C-terminal portion completely reverses the polymerization kinetics. Collectively, these data suggest that these Ca(2+)-sensitivity IDRs located at the back-to-back dimer interface influence isoform-specific Ca(2+)-dependent polymerization properties of CASQ.
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Affiliation(s)
- Naresh C Bal
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, 43210
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8
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Antón-Fernández A, Rubio-Garrido P, DeFelipe J, Muñoz A. Selective presence of a giant saccular organelle in the axon initial segment of a subpopulation of layer V pyramidal neurons. Brain Struct Funct 2013; 220:869-84. [DOI: 10.1007/s00429-013-0689-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 12/06/2013] [Indexed: 01/03/2023]
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9
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Potential role of cardiac calsequestrin in the lethal arrhythmic effects of cocaine. Drug Alcohol Depend 2013; 133:344-51. [PMID: 23876860 PMCID: PMC4097383 DOI: 10.1016/j.drugalcdep.2013.06.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 06/11/2013] [Accepted: 06/14/2013] [Indexed: 11/24/2022]
Abstract
BACKGROUND Cocaine-related deaths are continuously rising and its overdose is often associated with lethal cardiotoxic effects. METHODS AND RESULTS Our approach, employing isothermal titration calorimetry (ITC) and light scattering in parallel, has confirmed the significant affinity of human cardiac calsequestrin (CASQ2) for cocaine. Calsequestrin (CASQ) is a major Ca(2+)-storage protein within the sarcoplasmic reticulum (SR) of both cardiac and skeletal muscles. CASQ acts as a Ca(2+) buffer and Ca(2+)-channel regulator through its unique Ca(2+)-dependent oligomerization. Equilibrium dialysis and atomic absorption spectroscopy experiments illustrated the perturbational effect of cocaine on CASQ2 polymerization, resulting in substantial reduction of its Ca(2+)-binding capacity. We also confirmed the accumulation of cocaine in rat heart tissue and the substantial effects cocaine has on cultured C2C12 cells. The same experiments were performed with methamphetamine as a control, which displayed neither affinity for CASQ2 nor any significant effects on its function. Since cocaine did not have any direct effect on the Ca(2+)-release channel judging from our single channel recordings, these studies provide new insights into how cocaine may interfere with the normal E-C coupling mechanism with lethal arrhythmogenic consequences. CONCLUSION We propose that cocaine accumulates in SR through its affinity for CASQ2 and affects both SR Ca(2+) storage and release by altering the normal CASQ2 Ca(2+)-dependent polymerization. By this mechanism, cocaine use could produce serious cardiac problems, especially in people who have genetically-impaired CASQ2, defects in other E-C coupling components, or compromised cocaine metabolism and clearance.
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Lam AK, Galione A. The endoplasmic reticulum and junctional membrane communication during calcium signaling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2542-59. [DOI: 10.1016/j.bbamcr.2013.06.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 06/03/2013] [Accepted: 06/03/2013] [Indexed: 12/13/2022]
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Perni S, Close M, Franzini-Armstrong C. Novel details of calsequestrin gel conformation in situ. J Biol Chem 2013; 288:31358-62. [PMID: 24025332 DOI: 10.1074/jbc.m113.507749] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calsequestrin (CASQ) is the major component of the sarcoplasmic reticulum (SR) lumen in skeletal and cardiac muscles. This calcium-binding protein localizes to the junctional SR (jSR) cisternae, where it is responsible for the storage of large amounts of Ca(2+), whereas it is usually absent, at least in its polymerized form, in the free SR. The retention of CASQ inside the jSR is due partly to its association with other jSR proteins, such as junctin and triadin, and partly to its ability to polymerize, in a high Ca(2+) environment, into an intricate gel that holds the protein in place. In this work, we shed some light on the still poorly described in situ structure of polymerized CASQ using detailed EM images from thin sections, with and without tilting, and from deep-etched rotary-shadowed replicas. The latter directly illustrate the fundamental network nature of polymerized CASQ, revealing repeated nodal points connecting short segments of the linear polymer.
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Affiliation(s)
- Stefano Perni
- From the Department of Cell Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6058 and
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12
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Sanchez EJ, Lewis KM, Munske GR, Nissen MS, Kang C. Glycosylation of skeletal calsequestrin: implications for its function. J Biol Chem 2011; 287:3042-50. [PMID: 22170046 DOI: 10.1074/jbc.m111.326363] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calsequestrin (CASQ) serves as a major Ca(2+) storage/buffer protein in the sarcoplasmic reticulum (SR). When purified from skeletal muscle, CASQ1 is obtained in its glycosylated form. Here, we have confirmed the specific site and degree of glycosylation of native rabbit CASQ1 and have investigated its effect on critical properties of CASQ by comparison with the non-glycosylated recombinant form. Based on our comparative approach utilizing crystal structures, Ca(2+) binding capacities, analytical ultracentrifugation, and light-scattering profiles of the native and recombinant rabbit CASQ1, we propose a novel and dynamic role for glycosylation in CASQ. CASQ undergoes a unique degree of mannose trimming as it is trafficked from the proximal endoplasmic reticulum to the SR. The major glycoform of CASQ (GlcNAc(2)Man(9)) found in the proximal endoplasmic reticulum can severely hinder formation of the back-to-back interface, potentially preventing premature Ca(2+)-dependent polymerization of CASQ and ensuring its continuous mobility to the SR. Only trimmed glycans can stabilize both front-to-front and the back-to-back interfaces of CASQ through extensive hydrogen bonding and electrostatic interactions. Therefore, the mature glycoform of CASQ (GlcNAc(2)Man(1-4)) within the SR can be retained upon establishing a functional high capacity Ca(2+) binding polymer. In addition, based on the high resolution structures, we propose a molecular mechanism for the catecholaminergic polymorphic ventricular tachycardia (CPVT2) mutation, K206N.
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Affiliation(s)
- Emiliano J Sanchez
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, USA
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13
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Lynes EM, Simmen T. Urban planning of the endoplasmic reticulum (ER): how diverse mechanisms segregate the many functions of the ER. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1893-905. [PMID: 21756943 PMCID: PMC7172674 DOI: 10.1016/j.bbamcr.2011.06.011] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum (ER) is the biggest organelle in most cell types, but its characterization as an organelle with a continuous membrane belies the fact that the ER is actually an assembly of several, distinct membrane domains that execute diverse functions. Almost 20 years ago, an essay by Sitia and Meldolesi first listed what was known at the time about domain formation within the ER. In the time that has passed since, additional ER domains have been discovered and characterized. These include the mitochondria-associated membrane (MAM), the ER quality control compartment (ERQC), where ER-associated degradation (ERAD) occurs, and the plasma membrane-associated membrane (PAM). Insight has been gained into the separation of nuclear envelope proteins from the remainder of the ER. Research has also shown that the biogenesis of peroxisomes and lipid droplets occurs on specialized membranes of the ER. Several studies have shown the existence of specific marker proteins found on all these domains and how they are targeted there. Moreover, a first set of cytosolic ER-associated sorting proteins, including phosphofurin acidic cluster sorting protein 2 (PACS-2) and Rab32 have been identified. Intra-ER targeting mechanisms appear to be superimposed onto ER retention mechanisms and rely on transmembrane and cytosolic sequences. The crucial roles of ER domain formation for cell physiology are highlighted with the specific targeting of the tumor metastasis regulator gp78 to ERAD-mediating membranes or of the promyelocytic leukemia protein to the MAM.
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Affiliation(s)
- Emily M Lynes
- Department of Cell Biology, University of Alberta, Alberta, Canada
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14
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Infante C, Ponce M, Manchado M. Duplication of calsequestrin genes in teleosts: Molecular characterization in the Senegalese sole (Solea senegalensis). Comp Biochem Physiol B Biochem Mol Biol 2011; 158:304-14. [PMID: 21256971 DOI: 10.1016/j.cbpb.2011.01.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 01/16/2011] [Accepted: 01/17/2011] [Indexed: 01/20/2023]
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15
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Ramírez OA, Couve A. The endoplasmic reticulum and protein trafficking in dendrites and axons. Trends Cell Biol 2011; 21:219-27. [DOI: 10.1016/j.tcb.2010.12.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 11/24/2010] [Accepted: 12/02/2010] [Indexed: 12/12/2022]
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16
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Potential adverse interaction of human cardiac calsequestrin. Eur J Pharmacol 2010; 646:12-21. [PMID: 20713040 DOI: 10.1016/j.ejphar.2010.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 07/20/2010] [Accepted: 08/04/2010] [Indexed: 11/21/2022]
Abstract
Calsequestrin (CASQ) is a major Ca(2+) storage protein within the sarcoplasmic reticulum (SR) of both cardiac and skeletal muscles. CASQ reportedly acts as a Ca(2+) buffer and Ca(2+)-channel regulator through its unique Ca(2+)-dependent oligomerization, maintaining the free Ca(2+) concentration at a low level (0.5-1mM) and the stability of SR Ca(2+) releases. Our approach, employing isothermal titration calorimetry and light scattering in parallel, has provided valuable information about the affinity of human cardiac CASQ (hCASQ2) for a variety of drugs, which have been associated with heart- or muscle-related side effects. Those strongly binding drugs included phenothiazines, anthracyclines and Ca(2+) channel blockers, such as trifluoperazine, thioridazine, doxorubicin, daunorubicin, amlodipine and verapamil, having an average affinity of ~18 μM. They exhibit an inhibitory effect on in vitro Ca(2+)-dependent polymerization of hCASQ2 in a manner proportional to their binding affinity. Therefore accumulation of such drugs in the SR could significantly hinder the Ca(2+)-buffering capacity of the SR and/or the regulation of the Ca(2+) channel, RyR2. These effects could result in serious cardiac problems in people who have genetically impaired hCASQ2, defects in other E-C coupling components or problems with metabolism and clearance of those drugs.
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Kirchhefer U, Wehrmeister D, Postma AV, Pohlentz G, Mormann M, Kucerova D, Müller FU, Schmitz W, Schulze-Bahr E, Wilde AA, Neumann J. The human CASQ2 mutation K206N is associated with hyperglycosylation and altered cellular calcium handling. J Mol Cell Cardiol 2010; 49:95-105. [DOI: 10.1016/j.yjmcc.2010.03.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 03/04/2010] [Accepted: 03/08/2010] [Indexed: 10/19/2022]
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Bal NC, Sharon A, Gupta SC, Jena N, Shaikh S, Gyorke S, Periasamy M. The catecholaminergic polymorphic ventricular tachycardia mutation R33Q disrupts the N-terminal structural motif that regulates reversible calsequestrin polymerization. J Biol Chem 2010; 285:17188-96. [PMID: 20353949 DOI: 10.1074/jbc.m109.096354] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calsequestrin undergoes dynamic polymerization with increasing calcium concentration by front-to-front dimerization and back-to-back packing, forming wire-shaped structures. A recent finding that point mutation R33Q leads to lethal catecholaminergic polymorphic ventricular tachycardia (CPVT) implies a crucial role for the N terminus. In this study, we demonstrate that this mutation resides in a highly conserved alternately charged residue cluster (DGKDR; cluster 1) in the N-terminal end of calsequestrin. We further show that this cluster configures itself as a ring system and that the dipolar arrangement within the cluster brings about a critical conformational flip of Lys(31)-Asp(32) essential for dimer stabilization by formation of a H-bond network. We additionally show that Ca(2+)-induced calsequestrin aggregation is nonlinear and reversible and can regain the native conformation by Ca(2+) chelation with EGTA. This study suggests that cluster 1 works as a molecular switch and governs the bidirectional transition between the CASQ2 monomer and dimer. We further demonstrate that mutations disrupting the alternating charge pattern of the cluster, including R33Q, impair Ca(2+)-CASQ2 interaction, leading to altered polymerization-depolymerization dynamics. This study provides new mechanistic insight into the functional effects of the R33Q mutation and its potential role in CPVT.
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Affiliation(s)
- Naresh C Bal
- Department of Physiology and Cell Biology, The Ohio State University College of Medicine, and the Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA
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19
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Royer L, Ríos E. Deconstructing calsequestrin. Complex buffering in the calcium store of skeletal muscle. J Physiol 2009; 587:3101-11. [PMID: 19403601 PMCID: PMC2727020 DOI: 10.1113/jphysiol.2009.171934] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 04/22/2009] [Indexed: 12/22/2022] Open
Abstract
Since its discovery in 1971, calsequestrin has been recognized as the main Ca(2+) binding protein inside the sarcoplasmic reticulum (SR), the organelle that stores and upon demand mobilizes Ca(2+) for contractile activation of muscle. This article reviews the potential roles of calsequestrin in excitation-contraction coupling of skeletal muscle. It first considers the quantitative demands for a structure that binds Ca(2+) inside the SR in view of the amounts of the ion that must be mobilized to elicit muscle contraction. It briefly discusses existing evidence, largely gathered in cardiac muscle, of two roles for calsequestrin: as Ca(2+) reservoir and as modulator of the activity of Ca(2+) release channels, and then considers the results of an incipient body of work that manipulates the cellular endowment of calsequestrin. The observations include evidence that both the Ca(2+) buffering capacity of calsequestrin in solution and that of the SR in intact cells decay as the free Ca(2+) concentration is lowered. Together with puzzling observations of increase of Ca(2+) inside the SR, in cells or vesicular fractions, upon activation of Ca(2+) release, this is interpreted as evidence that the Ca(2+) buffering in the SR is non-linear, and is optimized for support of Ca(2+) release at the physiological levels of SR Ca(2+) concentration. Such non-linearity of buffering is qualitatively explained by a speculation that puts together ideas first proposed by others. The speculation pictures calsequestrin polymers as 'wires' that both bind Ca(2+) and efficiently deliver it near the release channels. In spite of the kinetic changes, the functional studies reveal that cells devoid of calsequestrin are still capable of releasing large amounts of Ca(2+) into the myoplasm, consistent with the long term viability and apparent good health of mice engineered for calsequestrin ablation. The experiments therefore suggest that other molecules are capable of providing sites for reversible binding of large amounts of Ca(2+) inside the sarcoplasmic reticulum.
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Affiliation(s)
- Leandro Royer
- Department of Molecular Biophysics and Physiology, Rush University School of Medicine, Chicago, IL 60612, USA
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20
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Ramírez OA, Vidal RL, Tello JA, Vargas KJ, Kindler S, Härtel S, Couve A. Dendritic assembly of heteromeric gamma-aminobutyric acid type B receptor subunits in hippocampal neurons. J Biol Chem 2009; 284:13077-85. [PMID: 19276079 PMCID: PMC2676040 DOI: 10.1074/jbc.m900575200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 03/09/2009] [Indexed: 01/27/2023] Open
Abstract
Understanding the mechanisms that control synaptic efficacy through the availability of neurotransmitter receptors depends on uncovering their specific intracellular trafficking routes. gamma-Aminobutyric acid type B (GABA(B)) receptors (GABA(B)Rs) are obligatory heteromers present at dendritic excitatory and inhibitory postsynaptic sites. It is unknown whether synthesis and assembly of GABA(B)Rs occur in the somatic endoplasmic reticulum (ER) followed by vesicular transport to dendrites or whether somatic synthesis is followed by independent transport of the subunits for assembly and ER export throughout the somatodendritic compartment. To discriminate between these possibilities we studied the association of GABA(B)R subunits in dendrites of hippocampal neurons combining live fluorescence microscopy, biochemistry, quantitative colocalization, and bimolecular fluorescent complementation. We demonstrate that GABA(B)R subunits are segregated and differentially mobile in dendritic intracellular compartments and that a high proportion of non-associated intracellular subunits exist in the brain. Assembled heteromers are preferentially located at the plasma membrane, but blockade of ER exit results in their intracellular accumulation in the cell body and dendrites. We propose that GABA(B)R subunits assemble in the ER and are exported from the ER throughout the neuron prior to insertion at the plasma membrane. Our results are consistent with a bulk flow of segregated subunits through the ER and rule out a post-Golgi vesicular transport of preassembled GABA(B)Rs.
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Affiliation(s)
- Omar A Ramírez
- Physiology and Biophysics, Faculty of Medicine, Universidad de Chile, Santiago, Chile
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21
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Michalak M, Opas M. Endoplasmic and sarcoplasmic reticulum in the heart. Trends Cell Biol 2009; 19:253-9. [PMID: 19409791 DOI: 10.1016/j.tcb.2009.03.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Revised: 03/21/2009] [Accepted: 03/23/2009] [Indexed: 12/30/2022]
Abstract
The concept of the presence of sarcoplasmic reticulum (SR) membrane in the heart is widely accepted and has been considered merely to be a different name for the endoplasmic reticulum (ER) in muscle tissues. Cardiac SR membranes are specialized in the regulation of Ca(2+) transport and control of excitation-contraction coupling. By contrast, the ER is responsible for protein synthesis, modification, secretion, lipid and steroid synthesis, and modulation of Ca(2+) signaling. Recent developments have indicated that functional changes in proteins or pathways normally associated with ER and not SR membrane impact cardiac development and pathology. Here, we propose that the SR and ER might be functionally distinct internal membrane compartments in cardiomyocytes.
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Affiliation(s)
- Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
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22
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Christis C, Lubsen NH, Braakman I. Protein folding includes oligomerization - examples from the endoplasmic reticulum and cytosol. FEBS J 2008; 275:4700-27. [DOI: 10.1111/j.1742-4658.2008.06590.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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23
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Modulation of SR Ca release by luminal Ca and calsequestrin in cardiac myocytes: effects of CASQ2 mutations linked to sudden cardiac death. Biophys J 2008; 95:2037-48. [PMID: 18469084 DOI: 10.1529/biophysj.107.128249] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cardiac calsequestrin (CASQ2) is an intrasarcoplasmic reticulum (SR) low-affinity Ca-binding protein, with mutations that are associated with catecholamine-induced polymorphic ventricular tachycardia (CPVT). To better understand how CASQ2 mutants cause CPVT, we expressed two CPVT-linked CASQ2 mutants, a truncated protein (at G112+5X, CASQ2(DEL)) or CASQ2 containing a point mutation (CASQ2(R33Q)), in canine ventricular myocytes and assessed their effects on Ca handling. We also measured CASQ2-CASQ2 variant interactions using fluorescence resonance transfer in a heterologous expression system, and evaluated CASQ2 interaction with triadin. We found that expression of CASQ2(DEL) or CASQ2(R33Q) altered myocyte Ca signaling through two different mechanisms. Overexpressing CASQ2(DEL) disrupted the CASQ2 polymerization required for high capacity Ca binding, whereas CASQ2(R33Q) compromised the ability of CASQ2 to control ryanodine receptor (RyR2) channel activity. Despite profound differences in SR Ca buffering strengths, local Ca release terminated at the same free luminal [Ca] in control cells, cells overexpressing wild-type CASQ2 and CASQ2(DEL)-expressing myocytes, suggesting that a decline in [Ca](SR) is a signal for RyR2 closure. Importantly, disrupting interactions between the RyR2 channel and CASQ2 by expressing CASQ2(R33Q) markedly lowered the [Ca](SR) threshold for Ca release termination. We conclude that CASQ2 in the SR determines the magnitude and duration of Ca release from each SR terminal by providing both a local source of releasable Ca and by effects on luminal Ca-dependent RyR2 gating. Furthermore, two CPVT-inducing CASQ2 mutations, which cause mechanistically different defects in CASQ2 and RyR2 function, lead to increased diastolic SR Ca release events and exhibit a similar CPVT disease phenotype.
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24
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Rossi D, Barone V, Giacomello E, Cusimano V, Sorrentino V. The sarcoplasmic reticulum: an organized patchwork of specialized domains. Traffic 2008; 9:1044-9. [PMID: 18266914 DOI: 10.1111/j.1600-0854.2008.00717.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The sarcoplasmic reticulum (SR) of skeletal muscle cells is a convoluted structure composed of a variety of tubules and cisternae, which share a continuous lumen delimited by a single continuous membrane, branching to form a network that surrounds each myofibril. In this network, some specific domains basically represented by the longitudinal SR and the junctional SR can be distinguished. These domains are mainly dedicated to Ca(2+) homeostasis in relation to regulation of muscle contraction, with the longitudinal SR representing the sites of Ca(2+) uptake and storage and the junctional SR representing the sites of Ca(2+) release. To perform its functions, the SR takes contact with other cellular elements, the sarcolemma, the contractile apparatus and the mitochondria, giving rise to a number of interactions, most of which are still to be defined at the molecular level. This review will describe some of the most recent advancements in understanding the organization of this complex network and its specific domains. Furthermore, we shall address initial evidence on how SR proteins are retained at distinct SR domains.
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Affiliation(s)
- Daniela Rossi
- Molecular Medicine Section, Department of Neuroscience and Interuniversitary Institute of Myology, University of Siena, 53100 Siena, Italy
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25
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Shadle SE, Rostock R, Bonfrisco L, Schimpf ME. Study of Calsequestrin Aggregation by Flow Field‐Flow Fractionation with Light Scattering Detection. J LIQ CHROMATOGR R T 2007. [DOI: 10.1080/10826070701277364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Susan E. Shadle
- a Department of Chemistry , Boise State University , Boise, Idaho, USA
| | - Randy Rostock
- a Department of Chemistry , Boise State University , Boise, Idaho, USA
| | - Lou Bonfrisco
- a Department of Chemistry , Boise State University , Boise, Idaho, USA
| | - Martin E. Schimpf
- a Department of Chemistry , Boise State University , Boise, Idaho, USA
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26
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Cho JH, Ko KM, Singaruvelu G, Lee W, Kang GB, Rho SH, Park BJ, Yu JR, Kagawa H, Eom SH, Kim DH, Ahnn J. Functional importance of polymerization and localization of calsequestrin in C. elegans. J Cell Sci 2007; 120:1551-8. [PMID: 17405817 DOI: 10.1242/jcs.001016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dual roles of calsequestrin (CSQ-1) being the Ca2+ donor and Ca2+ acceptor make it an excellent Ca2+-buffering protein within the sarcoplasmic reticulum (SR). We have isolated and characterized a calsequestrin (csq-1)-null mutant in Caenorhabditis elegans. To our surprise, this mutant csq-1(jh109) showed no gross defects in muscle development or function but, however, is highly sensitive to perturbation of Ca2+ homeostasis. By taking advantage of the viable null mutant, we investigated the domains of CSQ-1 that are important for polymerization and cellular localization, and required for its correct buffering functions. In transgenic animals rescued with various CSQ-1 constructs, the in vivo patterns of polymerization and localization of several mutated calsequestrins were observed to correlate with the structure-function relationship. Our results suggest that polymerization of CSQ-1 is essential but not sufficient for correct cellular localization and function of CSQ-1. In addition, direct interaction between CSQ-1 and the ryanodine receptor (RyR) was found for the first time, suggesting that the cellular localization of CSQ-1 in C. elegans is indeed modulated by RyR through a physical interaction.
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Affiliation(s)
- Jeong Hoon Cho
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, 500-712, Korea.
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27
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Baba Y, Hayashi K, Fujii Y, Mizushima A, Watarai H, Wakamori M, Numaga T, Mori Y, Iino M, Hikida M, Kurosaki T. Coupling of STIM1 to store-operated Ca2+ entry through its constitutive and inducible movement in the endoplasmic reticulum. Proc Natl Acad Sci U S A 2006; 103:16704-9. [PMID: 17075073 PMCID: PMC1636519 DOI: 10.1073/pnas.0608358103] [Citation(s) in RCA: 258] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Depletion of intracellular calcium (Ca(2+)) stores induces store-operated Ca(2+) (SOC) entry across the plasma membrane (PM). STIM1, a putative Ca(2+) sensor in the endoplasmic reticulum (ER), has been recently shown to be necessary for SOC channel activation. Here we show that STIM1 dynamically moves in tubulovesicular shape on the ER and its subcompartment in resting living cells, whereas, upon Ca(2+) store depletion, it is rapidly redistributed into discrete puncta that are located underneath, but not inserted into the PM. Normal constitutive movement of STIM1 is mediated through the coiled-coil and Ser/Thr-rich C-terminal domains in the cytoplasmic region of STIM1, whereas subsequent inducible puncta formation further requires the sterile alpha motif domain protruding into the ER lumen. Each of these three domains (coiled-coil, Ser/Thr-rich, and sterile alpha motif) was essential for activating SOC channels. Hence, our findings based on structure-function experiments suggest that constitutive dynamic movement of STIM1 in the ER and its subcompartment is obligatory for subsequent depletion-dependent redistribution of STIM1 into puncta underneath the PM and activation of SOC channels.
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Affiliation(s)
| | - Kenji Hayashi
- Department of Pharmacology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan; and
| | - Yoko Fujii
- *Laboratory for Lymphocyte Differentiation and
| | - Akiko Mizushima
- Department of Pharmacology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan; and
| | - Hiroshi Watarai
- Laboratory for Immune Regulation, RIKEN Research Center for Allergy and Immunology, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Minoru Wakamori
- Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan
| | - Takuro Numaga
- Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan
| | - Yasuo Mori
- Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan
| | - Masamitsu Iino
- Department of Pharmacology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan; and
| | | | - Tomohiro Kurosaki
- *Laboratory for Lymphocyte Differentiation and
- To whom correspondence should be addressed. E-mail:
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28
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di Barletta MR, Viatchenko-Karpinski S, Nori A, Memmi M, Terentyev D, Turcato F, Valle G, Rizzi N, Napolitano C, Gyorke S, Volpe P, Priori SG. Clinical phenotype and functional characterization of CASQ2 mutations associated with catecholaminergic polymorphic ventricular tachycardia. Circulation 2006; 114:1012-9. [PMID: 16908766 DOI: 10.1161/circulationaha.106.623793] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Four distinct mutations in the human cardiac calsequestrin gene (CASQ2) have been linked to catecholaminergic polymorphic ventricular tachycardia (CPVT). The mechanisms leading to the clinical phenotype are still poorly understood because only 1 CASQ2 mutation has been characterized in vitro. METHODS AND RESULTS We identified a homozygous 16-bp deletion at position 339 to 354 leading to a frame shift and a stop codon after 5aa (CASQ2(G112+5X)) in a child with stress-induced ventricular tachycardia and cardiac arrest. The same deletion was also identified in association with a novel point mutation (CASQ2(L167H)) in a highly symptomatic CPVT child who is the first CPVT patient carrier of compound heterozygous CASQ2 mutations. We characterized in vitro the properties of CASQ2 mutants: CASQ2(G112+5X) did not bind Ca2+, whereas CASQ2(L167H) had normal calcium-binding properties. When expressed in rat myocytes, both mutants decreased the sarcoplasmic reticulum Ca2+-storing capacity and reduced the amplitude of I(Ca)-induced Ca2+ transients and of spontaneous Ca2+ sparks in permeabilized myocytes. Exposure of myocytes to isoproterenol caused the development of delayed afterdepolarizations in CASQ2(G112+5X). CONCLUSIONS CASQ2(L167H) and CASQ2(G112+5X) alter CASQ2 function in cardiac myocytes, which leads to reduction of active sarcoplasmic reticulum Ca2+ release and calcium content. In addition, CASQ2(G112+5X) displays altered calcium-binding properties and leads to delayed afterdepolarizations. We conclude that the 2 CASQ2 mutations identified in CPVT create distinct abnormalities that lead to abnormal intracellular calcium regulation, thus facilitating the development of tachyarrhythmias.
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29
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Nori A, Valle G, Bortoloso E, Turcato F, Volpe P. Calsequestrin targeting to sarcoplasmic reticulum of skeletal muscle fibers. Am J Physiol Cell Physiol 2006; 291:C245-53. [PMID: 16571864 DOI: 10.1152/ajpcell.00370.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Calsequestrin (CS) is the low-affinity, high-capacity calcium binding protein segregated to the lumen of terminal cisternae (TC) of the sarcoplasmic reticulum (SR). The physiological role of CS in controlling calcium release from the SR depends on both its intrinsic properties and its localization. The mechanisms of CS targeting were investigated in skeletal muscle fibers and C2C12 myotubes, a model of SR differentiation, with four deletion mutants of epitope (hemagglutinin, HA)-tagged CS: CS-HA24NH2, CS-HA2D, CS-HA3D, and CS-HAHT, a double mutant of the NH2 terminus and domain III. As judged by immunofluorescence of transfected skeletal muscle fibers, only the double CS-HA mutant showed a homogeneous distribution at the sarcomeric I band, i.e., it did not segregate to TC. As shown by subfractionation of microsomes derived from transfected skeletal muscles, CS-HAHT was largely associated to longitudinal SR whereas CS-HA was concentrated in TC. In C2C12 myotubes, as judged by immunofluorescence, not only CS-HAHT but also CS-HA3D and CS-HA2D were not sorted to developing SR. Condensation competence, a property referable to CS oligomerization, was monitored for the several CS-HA mutants in C2C12 myoblasts, and only CS-HA3D was found able to condense. Together, the results indicate that 1) there are at least two targeting sequences at the NH2 terminus and domain III of CS, 2) SR-specific target and structural information is contained in these sequences, 3) heterologous interactions with junctional SR proteins are relevant for segregation, 4) homologous CS-CS interactions are involved in the overall targeting process, and 5) different targeting mechanisms prevail depending on the stage of SR differentiation.
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Affiliation(s)
- Alessandra Nori
- Dipartimento di Scienze Biomediche Sperimentali, Università degli Studi di Padova, viale G. Colombo 3, 35121 Padua, Italy
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30
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Rizzuto R, Pozzan T. Microdomains of intracellular Ca2+: molecular determinants and functional consequences. Physiol Rev 2006; 86:369-408. [PMID: 16371601 DOI: 10.1152/physrev.00004.2005] [Citation(s) in RCA: 885] [Impact Index Per Article: 49.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Calcium ions are ubiquitous and versatile signaling molecules, capable of decoding a variety of extracellular stimuli (hormones, neurotransmitters, growth factors, etc.) into markedly different intracellular actions, ranging from contraction to secretion, from proliferation to cell death. The key to this pleiotropic role is the complex spatiotemporal organization of the [Ca(2+)] rise evoked by extracellular agonists, which allows selected effectors to be recruited and specific actions to be initiated. In this review, we discuss the structural and functional bases that generate the subcellular heterogeneity in cellular Ca(2+) levels at rest and under stimulation. This complex choreography requires the concerted action of many different players; the central role is, of course, that of the calcium ion, with the main supporting characters being all the entities responsible for moving Ca(2+) between different compartments, while the cellular architecture provides a determining framework within which all the players have their exits and their entrances. In particular, we concentrate on the molecular mechanisms that lead to the generation of cytoplasmic Ca(2+) microdomains, focusing on their different subcellular location, mechanism of generation, and functional role.
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Affiliation(s)
- Rosario Rizzuto
- Department of Experimental and Diagnostic Medicine, and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Ferrara, Italy
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31
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Charlier HA, Olson RD, Thornock CM, Mercer WK, Olson DR, Broyles TS, Muhlestein DJ, Larson CL, Cusack BJ, Shadle SE. Investigations of Calsequestrin as a Target for Anthracyclines: Comparison of Functional Effects of Daunorubicin, Daunorubicinol, and Trifluoperazine. Mol Pharmacol 2005; 67:1505-12. [PMID: 15705743 DOI: 10.1124/mol.104.005728] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Anthracycline therapy is associated with a life-threatening but poorly understood cardiotoxicity. Effects of treatment are consistent with drug-induced disruption of cardiac sarcoplasmic reticulum (SR) calcium homeostasis, including inhibition of calcium release by anthracyclines. This effect, which depends on luminal SR calcium concentration, is hypothesized to involve interactions of anthracyclines with the calcium binding protein calsequestrin (CSQ). This study was designed to test the hypothesis that an interaction between CSQ and anthracyclines could be related to alterations in SR calcium release and cardiac function. The effects of the anthracycline, daunorubicin, and its metabolite daunorubicinol were compared with those of a known CSQ inhibitor, trifluoperazine (TFP). Protein fluorescence quenching studies demonstrated that TFP, daunorubicin, and daunorubicinol bind to CSQ with apparent binding affinities in the low micromolar range. The presence of calcium decreases the drug-dependent fluorescence quenching, probably because of calcium-induced CSQ conformational changes. TFP also inhibited SR calcium release. Although the TFP IC50 value is somewhat larger than for anthracyclines, the TFP effect is also dependent on luminal SR calcium concentration. In a muscle preparation, micromolar TFP decreased cardiac contractility in a manner that implicates the involvement of SR calcium and resembles the effects of anthracyclines. These data are consistent with a mechanism in which TFP or anthracyclines impair SR calcium release and cardiac function through a mechanism involving disruption of CSQ function. Such a mechanism may contribute to anthracycline cardiotoxicity.
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Affiliation(s)
- Henry A Charlier
- Department of Chemistry, Boise State University, Idaho 83725, USA
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32
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Viatchenko-Karpinski S, Terentyev D, Györke I, Terentyeva R, Volpe P, Priori SG, Napolitano C, Nori A, Williams SC, Györke S. Abnormal Calcium Signaling and Sudden Cardiac Death Associated With Mutation of Calsequestrin. Circ Res 2004; 94:471-7. [PMID: 14715535 DOI: 10.1161/01.res.0000115944.10681.eb] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mutations in human cardiac calsequestrin (CASQ2), a high-capacity calcium-binding protein located in the sarcoplasmic reticulum (SR), have recently been linked to effort-induced ventricular arrhythmia and sudden death (catecholaminergic polymorphic ventricular tachycardia). However, the precise mechanisms through which these mutations affect SR function and lead to arrhythmia are presently unknown. In this study, we explored the effect of adenoviral-directed expression of a canine CASQ2 protein carrying the catecholaminergic polymorphic ventricular tachycardia-linked mutation D307H (CASQ2(D307H)) on Ca2+ signaling in adult rat myocytes. Total CASQ2 protein levels were consistently elevated approximately 4-fold in cells infected with adenoviruses expressing either wild-type CASQ2 (CASQ2(WT)) or CASQ2(D307H). Expression of CASQ2(D307H) reduced the Ca2+ storing capacity of the SR. In addition, the amplitude, duration, and rise time of macroscopic I(Ca)-induced Ca2+ transients and of spontaneous Ca2+ sparks were reduced significantly in myocytes expressing CASQ2(D307H). Myocytes expressing CASQ2(D307H) also displayed drastic disturbances of rhythmic oscillations in [Ca2+]i and membrane potential, with signs of delayed afterdepolarizations when undergoing periodic pacing and exposed to isoproterenol. Importantly, normal rhythmic activity was restored by loading the SR with the low-affinity Ca2+ buffer, citrate. Our data suggest that the arrhythmogenic CASQ2(D307H) mutation impairs SR Ca2+ storing and release functions and destabilizes the Ca2+-induced Ca2+ release mechanism by reducing the effective Ca2+ buffering inside the SR and/or by altering the responsiveness of the Ca2+ release channel complex to luminal Ca2+. These results establish at the cellular level the pathological link between CASQ2 mutations and the predisposition to adrenergically mediated arrhythmias observed in patients carrying CASQ2 defects.
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33
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Bannai H, Inoue T, Nakayama T, Hattori M, Mikoshiba K. Kinesin dependent, rapid, bi-directional transport of ER sub-compartment in dendrites of hippocampal neurons. J Cell Sci 2004; 117:163-75. [PMID: 14676272 DOI: 10.1242/jcs.00854] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although spatially restricted Ca2+ release from the endoplasmic reticulum (ER) through intracellular Ca2+ channels plays important roles in various neuronal activities, the accurate distribution and dynamics of ER in the dendrite of living neurons still remain unknown. To elucidate these, we expressed fluorescent protein-tagged ER proteins in cultured mouse hippocampal neurons, and monitored their movements using time-lapse microscopy. We report here that a sub-compartment of ER forms in relatively large vesicles that are capable, similarly to the reticular ER, of taking up and releasing Ca2+. The vesicular sub-compartment of ER moved rapidly along the dendrites in both anterograde and retrograde directions at a velocity of 0.2-0.3 μm/second. Depletion of microtubules, overexpression of dominant-negative kinesin and kinesin depletion by antisense DNA reduced the number and velocity of the moving vesicles, suggesting that kinesin may drive the transport of the vesicular sub-compartment of ER along microtubules in the dendrite. Rapid transport of the Ca2+-releasable sub-compartment of ER might contribute to rapid supply of fresh ER proteins to the distal part of the dendrite, or to the spatial regulation of intracellular Ca2+ signaling.
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Affiliation(s)
- Hiroko Bannai
- Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
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Papp S, Dziak E, Michalak M, Opas M. Is all of the endoplasmic reticulum created equal? The effects of the heterogeneous distribution of endoplasmic reticulum Ca2+-handling proteins. J Cell Biol 2003; 160:475-9. [PMID: 12591911 PMCID: PMC2173736 DOI: 10.1083/jcb.200207136] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The endoplasmic reticulum is a heterogeneous compartment with respect to the distribution of its Ca2+-handling proteins, namely the Ca2+-binding proteins, the Ca2+ pumps and the Ca2+ release channels. The nonuniform distribution of these proteins may explain the functional heterogeneity of the endoplasmic reticulum, such as the generation of spatially complex Ca2+ signals, Ca2+ homeostasis, and protein folding and quality control.
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Affiliation(s)
- S Papp
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
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35
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Shin DW, Pan Z, Kim EK, Lee JM, Bhat MB, Parness J, Kim DH, Ma J. A retrograde signal from calsequestrin for the regulation of store-operated Ca2+ entry in skeletal muscle. J Biol Chem 2003; 278:3286-92. [PMID: 12419813 DOI: 10.1074/jbc.m209045200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calsequestrin (CSQ) is a high capacity Ca(2+)-binding protein present in the lumen of sarcoplasmic reticulum (SR) in striated muscle cells and has been shown to regulate the ryanodine receptor Ca(2+) release channel activity through interaction with other proteins present in the SR. Here we show that overexpression of wild-type CSQ or a CSQ mutant lacking the junction binding region (amino acids 86-191; Delta junc-CSQ) in mouse skeletal C2C12 myotube enhanced caffeine- and voltage-induced Ca(2+) release by increasing the Ca(2+) load in SR, whereas overexpression of a mutant CSQ lacking a Ca(2+) binding, aspartate-rich domain (amino acids 352-367; Delta asp-CSQ) showed the opposite effects. Depletion of SR Ca(2+) by thapsigargin initiated store-operated Ca(2+) entry (SOCE) in C2C12 myotubes. A large component of SOCE was inhibited by overexpression of wild-type CSQ or Delta junc-CSQ, whereas myotubes transfected with Delta asp-CSQ exhibited normal function of SOCE. These results indicate that the aspartate-rich segment of CSQ, under conditions of overexpression, can sustain structural interactions that interfere with the SOCE mechanism. Such retrograde activation mechanisms are possibly taking place at the junctional site of the SR.
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Affiliation(s)
- Dong Wook Shin
- Department of Life Science, Kwangju Institute of Science and Technology, Kwangju, 500-712, Korea
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36
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O'Brian JJ, Ram ML, Kiarash A, Cala SE. Mass spectrometry of cardiac calsequestrin characterizes microheterogeneity unique to heart and indicative of complex intracellular transit. J Biol Chem 2002; 277:37154-60. [PMID: 12147690 DOI: 10.1074/jbc.m204370200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cardiac calsequestrin concentrates in junctional sarcoplasmic reticulum in heart and skeletal muscle cells by an undefined mechanism. During transit through the secretory pathway, it undergoes an as yet uncharacterized glycosylation and acquires phosphate on CK2-sensitive sites. In this study, we have shown that active calsequestrin phosphorylation occurred in nonmuscle cells as well as muscle cells, reflecting a widespread cellular process. To characterize this post-translational modification and resolve individual molecular mass species, we subjected purified calsequestrin to mass spectrometry using electrospray ionization. Mass spectra showed that calsequestrin glycan structure in nonmuscle cells was that expected for an endoplasmic reticulum-localized glycoprotein and showed that each glycoform existed as four mass peaks representing molecules that also had 0-3 phosphorylation sites occupied. In heart, mass peaks indicated carbohydrate modifications characteristic of transit through Golgi compartments. Phosphorylation did not occur on every glycoform present, suggesting a far more complex movement of calsequestrin molecules in heart cells. Significant amounts of calsequestrin contained glycan with only a single mannose residue, indicative of a novel post-endoplasmic reticulum mannosidase activity. In conclusion, glyco- and phosphoforms of calsequestrin chart a complex cellular transport in heart, with calsequestrin following trafficking pathways not present or not accessible to the same molecules in nonmuscle.
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Affiliation(s)
- Jeffrey J O'Brian
- Program in Molecular and Cellular Cardiology, Department of Medicine, Wayne State University, Detroit, Michigan 48201, USA
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37
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Glover L, Quinn S, Ryan M, Pette D, Ohlendieck K. Supramolecular calsequestrin complex. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:4607-16. [PMID: 12230573 DOI: 10.1046/j.1432-1033.2002.03160.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
As recently demonstrated by overlay assays using calsequestrin-peroxidase conjugates, the major 63 kDa Ca(2+)-binding protein of the sarcoplasmic reticulum forms complexes with itself, and with junctin (26 kDa), triadin (94 kDa) and the ryanodine receptor (560 kDa) [Glover, L., Culligan, K., Cala, S., Mulvey, C. & Ohlendieck, K. (2001) Biochim. Biophys. Acta1515, 120-132]. Here, we show that variations in the relative abundance of these four central elements of excitation-contraction coupling in different fiber types, and during chronic electrostimulation-induced fiber type transitions, are reflected by distinct alterations in the calsequestrin overlay binding patterns. Comparative immunoblotting with antibodies to markers of the junctional sarcoplasmic reticulum, in combination with the calsequestrin overlay binding patterns, confirmed a lower ryanodine receptor expression in slow soleus muscle compared to fast fibers, and revealed a drastic reduction of the RyR1 isoform in chronic low-frequency stimulated tibialis anterior muscle. The fast-to-slow transition process included a distinct reduction in fast calsequestrin and triadin and a concomitant reduction in calsequestrin binding to these sarcoplasmic reticulum elements. The calsequestrin-binding protein junctin was not affected by the muscle transformation process. The increase in calsequestrin and decrease in junctin expression during postnatal development resulted in similar changes in the intensity of binding of the calsequestrin conjugate to these sarcoplasmic reticulum components. Aged skeletal muscle fibers tended towards reduced protein interactions within the calsequestrin complex. This agrees with the physiological concept that the key regulators of Ca(2+) homeostasis exist in a supramolecular membrane assembly and that protein-protein interactions are affected by isoform shifting underlying the finely tuned adaptation of muscle fibers to changed functional demands.
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Affiliation(s)
- Louise Glover
- Department of Pharmacology, University College Dublin, Belfield, Ireland
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Meldolesi J. Rapidly exchanging Ca(2+) stores: ubiquitous partners of surface channels in neurons. Physiology (Bethesda) 2002; 17:144-9. [PMID: 12136042 DOI: 10.1152/nips.01385.2002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neuronal rapidly exchanging Ca(2+) stores coincide with the endoplasmic reticulum and possess ample, nonrandom distribution, dual receptor channels, IP(3) and ryanodine receptors, and heterogeneous membranes. Because of these properties, the stores are able to reinforce and expand the Ca(2+) signals generated at the surface, working as partners of voltage- and receptor-gated channels.
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Affiliation(s)
- Jacopo Meldolesi
- Department of Neuroscience and Excellence Centre in Cell Differentiation, Vita-Salute San Raffaele University, 20132 Milan, Italy
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Meldolesi J. Rapidly exchanging Ca2+ stores in neurons: molecular, structural and functional properties. Prog Neurobiol 2001; 65:309-38. [PMID: 11473791 DOI: 10.1016/s0301-0082(01)00004-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- J Meldolesi
- DIBIT, Scientific Institute S. Raffaele, Vita-Salute University, Via Olgettina, 58, 20132, Milan, Italy.
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