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Saravanan V, Ahammed I, Bhattacharya A, Bhattacharya S. Uncovering allostery and regulation in SORCIN through molecular dynamics simulations. J Biomol Struct Dyn 2024; 42:1812-1825. [PMID: 37098805 DOI: 10.1080/07391102.2023.2202772] [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: 02/02/2023] [Accepted: 04/08/2023] [Indexed: 04/27/2023]
Abstract
Soluble resistance-related calcium-binding protein or Sorcin is an allosteric, calcium-binding Penta-EF hand (PEF) family protein implicated in multi-drug resistant cancers. Sorcin is known to bind chemotherapeutic molecules such as Doxorubicin. This study uses in-silico molecular dynamics simulations to explore the dynamics and allosteric behavior of Sorcin in the context of Ca2+ uptake and Doxorubicin binding. The results show that Ca2+ binding induces large, but reversible conformational changes in the Sorcin structure which manifest as rigid body reorientations that preserve the local secondary structure. A reciprocal allosteric handshake centered around the EF5 hand is found to be key in Sorcin dimer formation and stabilization. Binding of Doxorubicin results in rearrangement of allosteric communities which disrupts long-range allosteric information transfer from the N-terminal domain to the middle lobe. However, this binding does not result in secondary structure destabilization. Sorcin does not appear to have a distinct Ca2+ activated mode of Doxorubicin binding.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Vinnarasi Saravanan
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Ijas Ahammed
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Akash Bhattacharya
- Visiting Assistant Professor of Physics, St. Mary's University, San Antonio, Texas, USA
| | - Swati Bhattacharya
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
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Tanwar S, Qais FA, Naaz F, Rashid N, Ahmad F, Ur Rehman S. Identification of a novel Sorcin isoform with a different C-terminal but intact dimerization property. Sci Rep 2023; 13:15262. [PMID: 37709787 PMCID: PMC10502117 DOI: 10.1038/s41598-023-40913-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 08/18/2023] [Indexed: 09/16/2023] Open
Abstract
Sorcin (Sri), a member of penta EF-hand protein family plays a diverse role in maintaining calcium homeostasis, cell cycle and vesicular trafficking. Sri is highly conserved amongst mammals and consists of N-terminal glycine rich domain and C-terminal calcium binding domain that mediates its dimerization and interacts with different compounds. In the present study, with the help of combination of computational and molecular biology techniques, we have identified a novel isoform (Sri-N) in mouse which differs only in the C-terminal domain with that of Sri reported earlier. The novel isoform contains a new last exon that is different from the one present in the reported transcript (Sri). The presence of the novel isoform was further validated in different tissues by RT-PCR and DNA sequencing. The transcript was conceptually translated and subjected to in-silico analysis using different bioinformatics tools. The novel transcript variant encodes for a longer protein isoform without any change in the sub-cellular localization as predicted by PSORT-II online tool. Molecular modelling was performed to compare the structural changes in Sri-N and Sri isoforms. The structural characterization of the novel isoform using MD simulation depicted its overall stability under the physiological conditions. The molecular docking of proteins with various chemotherapeutic drugs revealed that their binding affinity is more for Sri-N as compared to that for the previously reported transcript Sri.
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Affiliation(s)
- Supriya Tanwar
- Department of Biochemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Faizan Abul Qais
- Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, UP, 202002, India
| | - Farheen Naaz
- Department of Biochemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Naira Rashid
- Department of Biochemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Faizan Ahmad
- Department of Biochemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Sayeed Ur Rehman
- Department of Biochemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, 110062, India.
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Tito C, Genovese I, Giamogante F, Benedetti A, Miglietta S, Barazzuol L, Cristiano L, Iaiza A, Carolini S, De Angelis L, Masciarelli S, Nottola SA, Familiari G, Petrozza V, Lauriola M, Tamagnone L, Ilari A, Calì T, Valdivia HH, Valdivia CR, Colotti G, Fazi F. Sorcin promotes migration in cancer and regulates the EGF-dependent EGFR signaling pathways. Cell Mol Life Sci 2023; 80:202. [PMID: 37442828 PMCID: PMC10345051 DOI: 10.1007/s00018-023-04850-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 06/03/2023] [Accepted: 06/28/2023] [Indexed: 07/15/2023]
Abstract
The epidermal growth factor receptor (EGFR) is one of the main tumor drivers and is an important therapeutic target for many cancers. Calcium is important in EGFR signaling pathways. Sorcin is one of the most important calcium sensor proteins, overexpressed in many tumors, that promotes cell proliferation, migration, invasion, epithelial-to-mesenchymal transition, malignant progression and resistance to chemotherapeutic drugs. The present work elucidates a functional mechanism that links calcium homeostasis to EGFR signaling in cancer. Sorcin and EGFR expression are significantly correlated and associated with reduced overall survival in cancer patients. Mechanistically, Sorcin directly binds EGFR protein in a calcium-dependent fashion and regulates calcium (dys)homeostasis linked to EGF-dependent EGFR signaling. Moreover, Sorcin controls EGFR proteostasis and signaling and increases its phosphorylation, leading to increased EGF-dependent migration and invasion. Of note, silencing of Sorcin cooperates with EGFR inhibitors in the regulation of migration, highlighting calcium signaling pathway as an exploitable target to enhance the effectiveness of EGFR-targeting therapies.
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Affiliation(s)
- Claudia Tito
- Section of Histology and Medical Embryology, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Via A. Scarpa, 14-16, 00161 Rome, Italy
| | - Ilaria Genovese
- Institute of Molecular Biology and Pathology, Italian National Research Council, IBPM-CNR, P.le A. Moro 5, 00185 Rome, Italy
| | - Flavia Giamogante
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Anna Benedetti
- Section of Histology and Medical Embryology, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Via A. Scarpa, 14-16, 00161 Rome, Italy
| | - Selenia Miglietta
- Section of Human Anatomy, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Rome, Italy
| | - Lucia Barazzuol
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Loredana Cristiano
- Department of Life, Health and Environmental Sciences, University of L’Aquila, L’Aquila, Italy
| | - Alessia Iaiza
- Section of Histology and Medical Embryology, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Via A. Scarpa, 14-16, 00161 Rome, Italy
| | - Sabatino Carolini
- Institute of Molecular Biology and Pathology, Italian National Research Council, IBPM-CNR, P.le A. Moro 5, 00185 Rome, Italy
| | - Luciana De Angelis
- Section of Histology and Medical Embryology, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Via A. Scarpa, 14-16, 00161 Rome, Italy
| | - Silvia Masciarelli
- Section of Histology and Medical Embryology, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Via A. Scarpa, 14-16, 00161 Rome, Italy
| | - Stefania Annarita Nottola
- Section of Human Anatomy, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Rome, Italy
| | - Giuseppe Familiari
- Section of Human Anatomy, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Rome, Italy
| | - Vincenzo Petrozza
- Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome, Latina, Italy
| | - Mattia Lauriola
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), University of Bologna, Bologna, Italy
| | - Luca Tamagnone
- Department of Life Science and Public Health, Histology and Embryology Unit - Catholic University of the Sacred Hearth, Fondazione Policlinico Gemelli - IRCCS, Rome, Italy
| | - Andrea Ilari
- Institute of Molecular Biology and Pathology, Italian National Research Council, IBPM-CNR, P.le A. Moro 5, 00185 Rome, Italy
| | - Tito Calì
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Hector H. Valdivia
- Department of Medicine, Cardiovascular Research Center, University of Wisconsin, Madison, WI USA
| | - Carmen R. Valdivia
- Department of Medicine, Cardiovascular Research Center, University of Wisconsin, Madison, WI USA
| | - Gianni Colotti
- Institute of Molecular Biology and Pathology, Italian National Research Council, IBPM-CNR, P.le A. Moro 5, 00185 Rome, Italy
| | - Francesco Fazi
- Section of Histology and Medical Embryology, Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Sapienza University of Rome, Via A. Scarpa, 14-16, 00161 Rome, Italy
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Wang Y, Zhu Y, Pu Z, Li Z, Deng Y, Li N, Peng F. Soluble resistance-related calcium-binding protein participates in multiple diseases via protein-protein interactions. Biochimie 2021; 189:76-86. [PMID: 34153376 DOI: 10.1016/j.biochi.2021.06.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 05/21/2021] [Accepted: 06/14/2021] [Indexed: 11/17/2022]
Abstract
Soluble resistance-related calcium-binding protein (sorcin), a 22 kDa penta-EF-hand protein, has been intensively studied in cancers and multidrug resistance over a prolonged period. Sorcin is widely distributed in tissues and participates in the regulation of Ca2+ homeostasis and Ca2+-dependent signaling. Protein-protein interactions (PPIs) are essential for regulating protein functions in almost all biological processes. Sorcin interaction partners tend to vary in type, including Ca2+ receptors, Ca2+ transporters, endoplasmic reticulum stress markers, transcriptional regulatory elements, immunomodulation-related factors, and viral proteins. Recent studies have shown that sorcin is involved in a broad range of pathological conditions, such as cardiomyopathy, type 2 diabetes mellitus, neurodegenerative diseases, liver diseases, and viral infections. As a multifunctional cellular protein, in these diseases, sorcin has a role by interacting with or regulating the expression of other proteins, such as sarcoplasmic reticulum/endoplasmic reticulum Ca2+ ATPase, ryanodine receptors, presenilin 2, L-type Ca2+ channels, carbohydrate-responsive element-binding protein, tau, α-synuclein, signal transducer and activator of transcription 3, HCV nonstructural 5A protein, and viral capsid protein 1. This review summarizes the roles that sorcin plays in various diseases, mainly via different PPIs, and focuses principally on non-neoplastic diseases to help acquire a more comprehensive understanding of sorcin's multifunctional characteristics.
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Affiliation(s)
- Yinmiao Wang
- Department of Blood Transfusion, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China; NHC Key Laboratory of Cancer Proteomics, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China
| | - Yuanyuan Zhu
- Department of Blood Transfusion, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China; NHC Key Laboratory of Cancer Proteomics, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China
| | - Zhangya Pu
- Department of Infectious Diseases and Hunan Key Laboratory of Viral Hepatitis, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China
| | - Zhenfen Li
- Department of Blood Transfusion, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China; NHC Key Laboratory of Cancer Proteomics, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China
| | - Ying Deng
- People's Hospital of Ningxiang, Changsha, Hunan Province 410600, China
| | - Ning Li
- Department of Blood Transfusion, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China
| | - Fang Peng
- Department of Blood Transfusion, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China; NHC Key Laboratory of Cancer Proteomics, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan Province 410008, China.
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Berrocal M, Saez L, Mata AM. Sorcin Activates the Brain PMCA and Blocks the Inhibitory Effects of Molecular Markers of Alzheimer's Disease on the Pump Activity. Int J Mol Sci 2021; 22:ijms22116055. [PMID: 34205207 PMCID: PMC8200006 DOI: 10.3390/ijms22116055] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/26/2021] [Accepted: 06/01/2021] [Indexed: 11/16/2022] Open
Abstract
Since dysregulation of intracellular calcium (Ca2+) levels is a common occurrence in neurodegenerative diseases, including Alzheimer’s disease (AD), the study of proteins that can correct neuronal Ca2+ dysregulation is of great interest. In previous work, we have shown that plasma membrane Ca2+-ATPase (PMCA), a high-affinity Ca2+ pump, is functionally impaired in AD and is inhibited by amyloid-β peptide (Aβ) and tau, two key components of pathological AD hallmarks. On the other hand, sorcin is a Ca2+-binding protein highly expressed in the brain, although its mechanism of action is far from being clear. Sorcin has been shown to interact with the intracellular sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA), and other modulators of intracellular Ca2+ signaling, such as the ryanodine receptor or presenilin 2, which is closely associated with AD. The present work focuses on sorcin in search of new regulators of PMCA and antagonists of Aβ and tau toxicity. Results show sorcin as an activator of PMCA, which also prevents the inhibitory effects of Aβ and tau on the pump, and counteracts the neurotoxicity of Aβ and tau by interacting with them.
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Genovese I, Giamogante F, Barazzuol L, Battista T, Fiorillo A, Vicario M, D'Alessandro G, Cipriani R, Limatola C, Rossi D, Sorrentino V, Poser E, Mosca L, Squitieri F, Perluigi M, Arena A, van Petegem F, Tito C, Fazi F, Giorgi C, Calì T, Ilari A, Colotti G. Sorcin is an early marker of neurodegeneration, Ca 2+ dysregulation and endoplasmic reticulum stress associated to neurodegenerative diseases. Cell Death Dis 2020; 11:861. [PMID: 33060591 PMCID: PMC7566454 DOI: 10.1038/s41419-020-03063-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 09/16/2020] [Accepted: 09/18/2020] [Indexed: 12/12/2022]
Abstract
Dysregulation of calcium signaling is emerging as a key feature in the pathogenesis of neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD), and targeting this process may be therapeutically beneficial. Under this perspective, it is important to study proteins that regulate calcium homeostasis in the cell. Sorcin is one of the most expressed calcium-binding proteins in the human brain; its overexpression increases endoplasmic reticulum (ER) calcium concentration and decreases ER stress in the heart and in other cellular types. Sorcin has been hypothesized to be involved in neurodegenerative diseases, since it may counteract the increased cytosolic calcium levels associated with neurodegeneration. In the present work, we show that Sorcin expression levels are strongly increased in cellular, animal, and human models of AD, PD, and HD, vs. normal cells. Sorcin partially colocalizes with RyRs in neurons and microglia cells; functional experiments with microsomes containing high amounts of RyR2 and RyR3, respectively, show that Sorcin is able to regulate these ER calcium channels. The molecular basis of the interaction of Sorcin with RyR2 and RyR3 is demonstrated by SPR. Sorcin also interacts with other ER proteins as SERCA2 and Sigma-1 receptor in a calcium-dependent fashion. We also show that Sorcin regulates ER calcium transients: Sorcin increases the velocity of ER calcium uptake (increasing SERCA activity). The data presented here demonstrate that Sorcin may represent both a novel early marker of neurodegenerative diseases and a response to cellular stress dependent on neurodegeneration.
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Affiliation(s)
- Ilaria Genovese
- Department of Medical Sciences, Laboratory for Technology of Advanced Therapies (LTTA) University of Ferrara, Ferrara, Italy
| | - Flavia Giamogante
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,Padova Neuroscience Center (PNC), University of Padova, Padova, Italy
| | - Lucia Barazzuol
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,Padova Neuroscience Center (PNC), University of Padova, Padova, Italy
| | - Theo Battista
- Department of Biochemical Sciences "A. Rossi Fanelli", University Sapienza of Rome, Rome, Italy
| | - Annarita Fiorillo
- Department of Biochemical Sciences "A. Rossi Fanelli", University Sapienza of Rome, Rome, Italy
| | - Mattia Vicario
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Giuseppina D'Alessandro
- Department of Physiology and Pharmacology, University of Rome "Sapienza", Rome, Italy.,IRCCS Neuromed, Pozzilli, Isernia, Italy
| | - Raffaela Cipriani
- Department of Physiology and Pharmacology, University of Rome "Sapienza", Rome, Italy
| | - Cristina Limatola
- IRCCS Neuromed, Pozzilli, Isernia, Italy.,Department of Physiology and Pharmacology, Sapienza University, Laboratory Affiliated to Istituto Pasteur Italia - Rome, Rome, Italy
| | - Daniela Rossi
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Vincenzo Sorrentino
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - Elena Poser
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Luciana Mosca
- Department of Biochemical Sciences "A. Rossi Fanelli", University Sapienza of Rome, Rome, Italy
| | - Ferdinando Squitieri
- Huntington's and Rare Diseases Unit, IRCCS Ospedale Casa Sollievo della Sofferenza, Rome, Italy
| | - Marzia Perluigi
- Department of Biochemical Sciences "A. Rossi Fanelli", University Sapienza of Rome, Rome, Italy
| | - Andrea Arena
- Department of Biochemical Sciences "A. Rossi Fanelli", University Sapienza of Rome, Rome, Italy
| | - Filip van Petegem
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Claudia Tito
- Department of Anatomical, Histological, Forensic & Orthopedic Sciences, Section of Histology & Medical Embryology, Sapienza University of Rome, Laboratory affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Rome, Italy
| | - Francesco Fazi
- Department of Anatomical, Histological, Forensic & Orthopedic Sciences, Section of Histology & Medical Embryology, Sapienza University of Rome, Laboratory affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Rome, Italy
| | - Carlotta Giorgi
- Department of Medical Sciences, Laboratory for Technology of Advanced Therapies (LTTA) University of Ferrara, Ferrara, Italy
| | - Tito Calì
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,Padova Neuroscience Center (PNC), University of Padova, Padova, Italy
| | - Andrea Ilari
- Institute of Molecular Biology and Pathology, Italian National Research Council, IBPM-CNR, Rome, Italy.
| | - Gianni Colotti
- Institute of Molecular Biology and Pathology, Italian National Research Council, IBPM-CNR, Rome, Italy.
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The potential mechanism of action of Sorcin and its interacting proteins. Clin Chim Acta 2020; 510:741-745. [PMID: 32946798 DOI: 10.1016/j.cca.2020.09.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 09/09/2020] [Accepted: 09/09/2020] [Indexed: 12/14/2022]
Abstract
Sorcin (Soluble resistance-related calcium binding protein) is a calcium binding oncoprotein. Sorcin is overexpressed in several human tumors and cancer cells lines which confers multidrug resistance (MDR) to these cells. This review summarizes the biochemical functions of Sorcin which includes modulation of calcium homeostasis, apoptosis, and cancer metastasis. Sorcin is involved in various biological processes by interacting with other proteins, such as p-glycoprotein, programmed cell death protein 6, tumor necrosis factor receptor-associated protein 1, Annexin A7, polo-like kinase 1, HCV nonstructural 5A, signal transducer and activator of transcription 3, presenilin 2, α-synuclein, Ca2+-release channel and others. A deeper look into the function and interacting partners of Sorcin sheds more light on the possible effects of its physical activity and more elaborately, exploring the role of Sorcin in future research prospects.
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Genovese I, Carotti A, Ilari A, Fiorillo A, Battista T, Colotti G, Ivarsson Y. Profiling calcium-dependent interactions between Sorcin and intrinsically disordered regions of human proteome. Biochim Biophys Acta Gen Subj 2020; 1864:129618. [PMID: 32305337 DOI: 10.1016/j.bbagen.2020.129618] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 03/05/2020] [Accepted: 04/12/2020] [Indexed: 11/18/2022]
Abstract
BACKGROUND Sorcin is a calcium sensor that exerts many calcium-related functions in the cells, e.g. it regulates calcium concentration in the cytoplasm, endoplasmic reticulum (ER) and mitochondria, by interacting with calcium pumps, exchangers and channels. Albeit Sorcin is an interesting potential cancer target, little is known about its interactors upon calcium-mediated activation. Our previous study suggested that Sorcin may recognize short linear binding motifs as the crystal structure revealed a self-interaction with a GYYPGG stretch in its N-terminus, and combinatorial peptide-phage display provided support for peptide-mediated interactions. METHODS In this study we screened for motif-based interactions between Sorcin and intrinsically disordered regions of the human proteome using proteomic peptide phage display (ProP-PD). We identified a peptide belonging to protein phosphatase 1 regulatory subunit 3G (PPP1R3G) as a potential novel interactor and confirm the interaction through biophysical and cell-based approaches, and provide structural information through molecular dynamics simulations. RESULTS Altogether, we identify a preferred motif in the enriched pool of binders and a peptide belonging to protein phosphatase 1 regulatory subunit 3G (PPP1R3G) as a preferred ligand. CONCLUSION Through this study we gain information on a new Sorcin binding partner and profile Sorcin's motif-based interaction. GENERAL SIGNIFICANCE The interaction between Sorcin and PPP1R3G may suggest a close dependence between glucose homeostasis and calcium concentration in the different cell compartments, opening a completely new and interesting scenery yet to be fully disclosed.
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Affiliation(s)
- Ilaria Genovese
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, via Fossato di Mortara 70, 44121 Ferrara, Italy; Department of Biochemical Sciences, University Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy; Department of Chemistry - BMC, Uppsala University, Husargatan 3, 751 23 Uppsala, Sweden.
| | - Andrea Carotti
- Department of Pharmaceutical Sciences, University of Perugia, Via Fabretti 48, 06123 Perugia, Italy
| | - Andrea Ilari
- Institute of Molecular Biology and Pathology National Research Council, IBPM-CNR, c/o Department of Biochemical Sciences, University Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Annarita Fiorillo
- Department of Biochemical Sciences, University Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Theo Battista
- Department of Biochemical Sciences, University Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Gianni Colotti
- Institute of Molecular Biology and Pathology National Research Council, IBPM-CNR, c/o Department of Biochemical Sciences, University Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Ylva Ivarsson
- Department of Chemistry - BMC, Uppsala University, Husargatan 3, 751 23 Uppsala, Sweden
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Battista T, Fiorillo A, Chiarini V, Genovese I, Ilari A, Colotti G. Roles of Sorcin in Drug Resistance in Cancer: One Protein, Many Mechanisms, for a Novel Potential Anticancer Drug Target. Cancers (Basel) 2020; 12:cancers12040887. [PMID: 32268494 PMCID: PMC7226229 DOI: 10.3390/cancers12040887] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 03/31/2020] [Accepted: 04/03/2020] [Indexed: 02/07/2023] Open
Abstract
The development of drug resistance is one of the main causes of failure in anti-cancer treatments. Tumor cells adopt many strategies to counteract the action of chemotherapeutic agents, e.g., enhanced DNA damage repair, inactivation of apoptotic pathways, alteration of drug targets, drug inactivation, and overexpression of ABC (Adenosine triphosphate-binding cassette, or ATP-binding cassette) transporters. These are broad substrate-specificity ATP-dependent efflux pumps able to export toxins or drugs out of cells; for instance, ABCB1 (MDR1, or P-glycoprotein 1), overexpressed in most cancer cells, confers them multidrug resistance (MDR). The gene coding for sorcin (SOluble Resistance-related Calcium-binding proteIN) is highly conserved among mammals and is located in the same chromosomal locus and amplicon as the ABC transporters ABCB1 and ABCB4, both in human and rodent genomes (two variants of ABCB1, i.e., ABCB1a and ABCB1b, are in rodent amplicon). Sorcin was initially characterized as a soluble protein overexpressed in multidrug (MD) resistant cells and named "resistance-related" because of its co-amplification with ABCB1. Although for years sorcin overexpression was thought to be only a by-product of the co-amplification with ABC transporter genes, many papers have recently demonstrated that sorcin plays an important part in MDR, indicating a possible role of sorcin as an oncoprotein. The present review illustrates sorcin roles in the generation of MDR via many mechanisms and points to sorcin as a novel potential target of different anticancer molecules.
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Affiliation(s)
- Theo Battista
- Department of Biochemical Sciences, Sapienza University, P.le A.Moro 5, 00185 Rome, Italy; (T.B.); (A.F.)
| | - Annarita Fiorillo
- Department of Biochemical Sciences, Sapienza University, P.le A.Moro 5, 00185 Rome, Italy; (T.B.); (A.F.)
| | - Valerio Chiarini
- Doctoral Programme in Integrative Life Science, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland;
| | - Ilaria Genovese
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies, University of Ferrara, 44121 Ferrara, Italy;
| | - Andrea Ilari
- Institute of Molecular Biology and Pathology, Italian National Research Council, Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche (IBPM-CNR), c/o Department of Biochemical Sciences, Sapienza University, P.le A.Moro 5, 00185 Rome, Italy
- Correspondence: (A.I.); (G.C.)
| | - Gianni Colotti
- Institute of Molecular Biology and Pathology, Italian National Research Council, Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche (IBPM-CNR), c/o Department of Biochemical Sciences, Sapienza University, P.le A.Moro 5, 00185 Rome, Italy
- Correspondence: (A.I.); (G.C.)
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Kobuke K, Oki K, Gomez-Sanchez CE, Gomez-Sanchez EP, Ohno H, Itcho K, Yoshii Y, Yoneda M, Hattori N. Calneuron 1 Increased Ca 2+ in the Endoplasmic Reticulum and Aldosterone Production in Aldosterone-Producing Adenoma. Hypertension 2017; 71:125-133. [PMID: 29109191 DOI: 10.1161/hypertensionaha.117.10205] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/01/2017] [Accepted: 10/10/2017] [Indexed: 11/16/2022]
Abstract
Aldosterone production is initiated by angiotensin II stimulation and activation of intracellular Ca2+ signaling. In aldosterone-producing adenoma (APA) cells, the activation of intracellular Ca2+ signaling is independent of the renin-angiotensin-aldosterone systems. The purpose of our study was to clarify molecular mechanisms of aldosterone production related to Ca2+ signaling. Transcriptome analysis revealed that the CALN1 gene encoding calneuron 1 had the strongest correlation with CYP11B2 (aldosterone synthase) among genes encoding Ca2+-binding proteins in APA. CALN1 modulation and synthetic or fluorescent compounds were used for functional studies in human adrenocortical carcinoma (HAC15) cells. CALN1 expression was 4.4-fold higher in APAs than nonfunctioning adrenocortical adenomas. CALN1 expression colocalized with CYP11B2 expression as investigated using immunohistochemistry in APA and zona glomerulosa of male rats fed by a low-salt diet. CALN1 expression was detected in the endoplasmic reticulum (ER) by using GFP-fused CALN1, CellLight ER-RFP, and the corresponding antibodies. CALN1-overexpressing HAC15 cells showed increased Ca2+ in the ER and cytosol fluorescence-based studies. Aldosterone production was potentiated in HAC15 cells by CALN1 expression, and dose-responsive inhibition with TMB-8 showed that CALN1-mediated Ca2+ storage in ER involved sarcoendoplasmic reticulum calcium transport ATPase. The silencing of CALN1 decreased Ca2+ in ER, and abrogated angiotensin II- or KCNJ5 T158A-mediated aldosterone production in HAC15 cells. Increased CALN1 expression in APA was associated with elevated Ca2+ storage in ER and aldosterone overproduction. Suppression of CALN1 expression prevented angiotensin II- or KCNJ5 T158A-mediated aldosterone production in HAC15 cells, suggesting that CALN1 is a potential therapeutic target for excess aldosterone production.
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Affiliation(s)
- Kazuhiro Kobuke
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Kenji Oki
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.).
| | - Celso E Gomez-Sanchez
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Elise P Gomez-Sanchez
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Haruya Ohno
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Kiyotaka Itcho
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Yoko Yoshii
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Masayasu Yoneda
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
| | - Noboru Hattori
- From the Department of Molecular and Internal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan (K.K., K.O., H.O., K.I., Y.Y., M.Y., N.H.); Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS (C.E.G.-S., E.P.G.-S.); and University of Mississippi Medical Center, Jackson (C.E.G.-S., E.P.G.-S.)
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11
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Kim SI, Lee HJ, Kim SS, Kwon YS, Chun W. Sequestration of sorcin by aberrant forms of tau results in the defective calcium homeostasis. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:387-97. [PMID: 27382355 PMCID: PMC4930907 DOI: 10.4196/kjpp.2016.20.4.387] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/23/2016] [Accepted: 04/09/2016] [Indexed: 11/15/2022]
Abstract
Neurofi brillary tangles (NFTs) of microtubule-associated protein tau are a pathological hallmark of Alzheimer's disease (AD). Endoplasmic reticulum (ER) stress has been known to be involved in the pathogenesis of AD. However, the exact role of ER stress in tau pathology has not yet been clearly elucidated. In present study, the possible relationship between tau pathology and ER stress was examined in terms of sorcin, which is a calcium binding protein and plays an important role in calcium homeostasis. Our previous yeast two hybrid study showed that sorcin is a novel tau interacting protein. Caspase-3-cleaved tau (T4C3) showed significantly increased tau-sorcin interaction compared to wild type tau (T4). Thapsigargin-induced ER stress and co-expression of constitutively active GSK3β (GSK3β-S9A) also exhibited significantly increased tau-sorcin interactions. T4C3-expressing cells showed potentiated thapsigargin-induced apoptosis and disruption of intracellular calcium homeostasis compared to T4-expressing cells. Overexpression of sorcin signifi cantly attenuated thapsigargin-induced apoptosis and disruption of calcium homeostasis. In contrary, siRNA-mediated knock-down of sorcin showed significantly increased thapsigargin-induced apoptosis and disruption of calcium homeostasis. These data strongly suggest that sequestration of sorcin by aberrant forms of tau compromises the function of sorcin, such as calcium homeostasis and cellular resistance by ER stress, which may consequently result in the contribution to the progression of AD.
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Affiliation(s)
- Song-In Kim
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
| | - Hee Jae Lee
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
| | - Sung-Soo Kim
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
| | - Yong-Soo Kwon
- School of Pharmacy, Kangwon National University, Chuncheon 24341, Korea
| | - Wanjoo Chun
- Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea
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12
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Structural basis of Sorcin-mediated calcium-dependent signal transduction. Sci Rep 2015; 5:16828. [PMID: 26577048 PMCID: PMC4649501 DOI: 10.1038/srep16828] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Accepted: 10/20/2015] [Indexed: 12/11/2022] Open
Abstract
Sorcin is an essential penta-EF hand calcium binding protein, able to confer the multi-drug resistance phenotype to drug-sensitive cancer cells and to reduce Endoplasmic Reticulum stress and cell death. Sorcin silencing blocks cell cycle progression in mitosis and induces cell death by triggering apoptosis. Sorcin participates in the modulation of calcium homeostasis and in calcium-dependent cell signalling in normal and cancer cells. The molecular basis of Sorcin action is yet unknown. The X-ray structures of Sorcin in the apo (apoSor) and in calcium bound form (CaSor) reveal the structural basis of Sorcin action: calcium binding to the EF1-3 hands promotes a large conformational change, involving a movement of the long D-helix joining the EF1-EF2 sub-domain to EF3 and the opening of EF1. This movement promotes the exposure of a hydrophobic pocket, which can accommodate in CaSor the portion of its N-terminal domain displaying the consensus binding motif identified by phage display experiments. This domain inhibits the interaction of sorcin with PDCD6, a protein that carries the Sorcin consensus motif, co-localizes with Sorcin in the perinuclear region of the cell and in the midbody and is involved in the onset of apoptosis.
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13
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Colotti G, Poser E, Fiorillo A, Genovese I, Chiarini V, Ilari A. Sorcin, a calcium binding protein involved in the multidrug resistance mechanisms in cancer cells. Molecules 2014; 19:13976-89. [PMID: 25197934 PMCID: PMC6271628 DOI: 10.3390/molecules190913976] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 08/27/2014] [Accepted: 08/28/2014] [Indexed: 11/23/2022] Open
Abstract
Sorcin is a penta-EF hand calcium binding protein, which participates in the regulation of calcium homeostasis in cells. Sorcin regulates calcium channels and exchangers located at the plasma membrane and at the endo/sarcoplasmic reticulum (ER/SR), and allows high levels of calcium in the ER to be maintained, preventing ER stress and possibly, the unfolded protein response. Sorcin is highly expressed in the heart and in the brain, and overexpressed in many cancer cells. Sorcin gene is in the same amplicon as other genes involved in the resistance to chemotherapeutics in cancer cells (multi-drug resistance, MDR) such as ABCB4 and ABCB1; its overexpression results in increased drug resistance to a number of chemotherapeutic agents, and inhibition of sorcin expression by sorcin-targeting RNA interference leads to reversal of drug resistance. Sorcin is increasingly considered a useful marker of MDR and may represent a therapeutic target for reversing tumor multidrug resistance.
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Affiliation(s)
- Gianni Colotti
- Institute of Biology, Molecular Medicine and Nanobiotechnology, Consiglio Nazionale delle Ricerche, P.le A Moro 5, Rome 00185, Italy.
| | - Elena Poser
- Department Biochemical Sciences "A. Rossi Fanelli", University Sapienza, P.le A. Moro 5, Rome 00185, Italy.
| | - Annarita Fiorillo
- Department Biochemical Sciences "A. Rossi Fanelli", University Sapienza, P.le A. Moro 5, Rome 00185, Italy.
| | - Ilaria Genovese
- Department Biochemical Sciences "A. Rossi Fanelli", University Sapienza, P.le A. Moro 5, Rome 00185, Italy.
| | - Valerio Chiarini
- Department Biochemical Sciences "A. Rossi Fanelli", University Sapienza, P.le A. Moro 5, Rome 00185, Italy.
| | - Andrea Ilari
- Institute of Biology, Molecular Medicine and Nanobiotechnology, Consiglio Nazionale delle Ricerche, P.le A Moro 5, Rome 00185, Italy.
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Song DW, Lee JG, Youn HS, Eom SH, Kim DH. Ryanodine receptor assembly: A novel systems biology approach to 3D mapping. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 105:145-61. [DOI: 10.1016/j.pbiomolbio.2010.09.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Revised: 09/14/2010] [Accepted: 09/28/2010] [Indexed: 10/19/2022]
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15
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Activation of the cardiac Na(+)-Ca(2+) exchanger by sorcin via the interaction of the respective Ca(2+)-binding domains. J Mol Cell Cardiol 2010; 49:132-41. [PMID: 20298697 PMCID: PMC2958309 DOI: 10.1016/j.yjmcc.2010.03.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 01/21/2010] [Accepted: 03/08/2010] [Indexed: 11/24/2022]
Abstract
Sorcin is a penta-EF-hand protein that interacts with intracellular target proteins after Ca2+ binding. The sarcolemmal Na+/Ca2+ exchanger (NCX1) may be an important sorcin target in cardiac muscle. In this study, RNAi knockdown of sorcin, purified sorcin or sorcin variants was employed in parallel measurements of: (i) NCX activity in isolated rabbit cardiomyocytes using electrophysiological techniques and (ii) sorcin binding to the NCX1 calcium binding domains (CBD1 and (iii) using surface plasmon resonance and gel overlay techniques. Sorcin is activated by Ca2+ binding to the EF3 and EF2 regions, which are connected by the D helix. To investigate the importance of this region in the interaction with NCX1, three variants were examined: W105G and W99G, mutated respectively near EF3 and EF2, and E124A that does not bind Ca2+ due to a mutation at EF3. Downregulation of sorcin decreased and supplementation with wt sorcin (3 μM) increased NCX activity in isolated cardiomyocytes. The relative stimulatory effects of the sorcin variants were: W105G > wt sorcin > Sorcin Calcium Binding Domain (SCBD) > W99G > E124A. Sorcin binding to both CBD1 and 2 was observed. In the presence of 50 µM Ca2+, the interaction with CBD1 followed the order W105G > SCBD > wt sorcin > W99G > E124A. In sorcin, the interacting surface can be mapped on the C-terminal Ca2+-binding domain in the D helix region comprising W99. The fast association/dissociation rates that characterize the interaction of sorcin with CBD1 and 2 may permit complex formation/dissociation during an excitation/contraction cycle.
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16
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Vernarecci S, Colotti G, Ornaghi P, Schiebel E, Chiancone E, Filetici P. The yeast penta-EF protein Pef1p is involved in cation-dependent budding and cell polarization. Mol Microbiol 2007; 65:1122-38. [PMID: 17640275 DOI: 10.1111/j.1365-2958.2007.05852.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Penta-EF-hand (PEF) proteins bind calcium and participate in a variety of calcium-dependent processes in vertebrates. In yeast, intracellular cations regulate processes like cell division and polarized growth. This study reports the identification of a unique PEF protein in Saccharomyces cerevisiae encoded by the uncharacterized open reading frame YGR058w. Pef1p has a long and unstructured N-terminal domain conserved in ascomycetes, and a highly conserved C-terminal calcium binding domain homologous to human ALG-2 and sorcin. Pef1p binds calcium and zinc and homodimerizes in vitro and in vivo like vertebrate homologues. Disruption of PEF1 induces defective growth in SDS and cation depletion conditions. Significantly, a critical substitution in the second EF hand (E218A) lowers the in vitro affinity for zinc and phenocopies growth defects. The dissection of protein-protein interactions and the cellular localization of Pef1p analogous to that of RAM pathway components controlling daughter-specific gene expression at the site of bud emergence bring out the importance of this novel protein. Our data suggest that cation homeostasis is involved in the control of polarized growth and in stress response in budding yeast.
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Affiliation(s)
- Stefano Vernarecci
- Istituto di Biologia e Patologia Molecolari, CNR, and Dipartemento di Genetica e Biologia Molecolare, Sapienza Università di Roma, P. le A. Moro 5, 00185 Rome, Italy
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17
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Appelblom H, Nurmi J, Soukka T, Pasternack M, Penttilä KE, Lövgren T, Niemelä P. Homogeneous TR-FRET High-Throughput Screening Assay for Calcium-Dependent Multimerization of Sorcin. ACTA ACUST UNITED AC 2007; 12:842-8. [PMID: 17579123 DOI: 10.1177/1087057107303973] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A homogeneous high-throughput screening method based on time-resolved fluorescence resonance energy transfer (TR-FRET) for the measurement of calcium-dependent multimerization of an EF-hand protein, sorcin, is described. The assay is based on a specific sorcin binding peptide conjugated either with an intrinsically highly fluorescent europium chelate (donor) or an Alexa Fluor 700 fluorophore (acceptor). Addition of calcium results in multimerization of sorcin, allowing several peptides to bind simultaneously to the epitopes of the multimeric protein complex, and the proximity of peptides labeled either with donor or acceptor label results in fluorescence resonance energy transfer between the 2 labels. When no calcium is present, the protein remains in a monomer form, and thus no FRET can take place. In the optimized assay construct, the assay was performed in 45 min, and a more than 20-fold signal-to-background ratio was achieved. The reversibility of sorcin multimerization was shown by chelating free calcium with ethylenediamine tetraacetic acid (EDTA). The developed homogeneous assay can be used in screening molecules that either inhibit or enhance multimerization of sorcin, and the assay format is applicable to various noncompetitive high-throughput screening assays detecting protein multimerization reactions. ( Journal of Biomolecular Screening 2007:842-848)
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18
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Barry JK, Selinger DA, Wang C, Olsen OA, Rao AG. Biochemical characterization of a truncated penta-EF-hand Ca2+ binding protein from maize. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:239-45. [PMID: 16269278 DOI: 10.1016/j.bbapap.2005.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 09/30/2005] [Accepted: 10/03/2005] [Indexed: 10/25/2022]
Abstract
Plants possess multiple genes encoding calcium sensor proteins that are members of the penta-EF-hand (PEF) family. Characterized PEF proteins such as ALG-2 (apoptosis-linked gene 2 product) and the calpain small subunit function in diverse cellular processes in a calcium-dependent manner by interacting with their target proteins at either their N-terminal extension or Ca2+ binding domains. We have identified a previously unreported class of PEF proteins in plants that are notable because they do not possess the hydrophobic amino acid rich N-terminal extension that is typical of these PEF proteins. We demonstrate that the maize PEF protein without the N-terminal extension has the characteristics of known PEF proteins; the protein binds calcium in the 100 nM range and, as a result of calcium binding, displays an increase in hydrophobicity. Characterization of the truncated maize PEF protein provides insights into the role of the N-terminal extension in PEF protein signaling. In the context of the current model of how PEF proteins are activated by calcium binding, these results demonstrate that this distinctive class of PEF proteins could function as calcium sensor proteins in plants even in the absence of the N-terminal extension.
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Affiliation(s)
- Jennifer K Barry
- Pioneer Hi-Bred International, A DuPont Company, 7300 NW 62nd Avenue, Johnston, Iowa 50131, USA
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19
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Leinala EK, Arthur JSC, Grochulski P, Davies PL, Elce JS, Jia Z. A second binding site revealed by C-terminal truncation of calpain small subunit, a penta-EF-hand protein. Proteins 2003; 53:649-55. [PMID: 14579356 DOI: 10.1002/prot.10453] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The subunits in calpain and in the related penta-EF-hand (PEF) proteins are bound through contacts between the unpaired EF-hand 5 from each subunit. To study subunit binding further, a tetra-EF-hand 18 kDa N- and C-terminally truncated form of the calpain small subunit was prepared (18k). This protein does not combine with the calpain large subunit to form active calpain, but forms homodimers in solution, as shown by ultracentrifugation. The X-ray structure of the 18k protein in the presence of cadmium was solved to a resolution of 2.0 A. The structure of the monomer is almost identical to the known structure of the calpain small subunit, but the 18k protein forms an oligomer in the crystal by the use of two binding sites. One of these sites is an artefact arising from the C-terminal truncation, but the other is a naturally occurring site that is fully exposed to water in intact purified calpain. The characteristics of this site suggest that it may be important in binding other protein modulators involved in the regulation of calpain and of PEF proteins.
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Affiliation(s)
- E K Leinala
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
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20
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Farrell EF, Antaramian A, Rueda A, Gómez AM, Valdivia HH. Sorcin inhibits calcium release and modulates excitation-contraction coupling in the heart. J Biol Chem 2003; 278:34660-6. [PMID: 12824171 DOI: 10.1074/jbc.m305931200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of Ca2+ release channels/ryanodine receptors (RyR) by the inward Ca2+ current (ICa) gives rise to Ca2+-induced Ca2+ release (CICR), the amplifying Ca2+ signaling mechanism that triggers contraction of the heart. CICR, in theory, is a high-gain, self-regenerating process, but an unidentified mechanism stabilizes it in vivo. We reported previously (Lokuta, A. J., Meyers, M. B., Sander, P. R., Fishman, G. I., and Valdivia, H. H. (1997) J. Biol. Chem. 272, 25333-25338) that sorcin, a 22-kDa Ca2+-binding protein, binds to cardiac RyRs with high affinity and completely inhibits channel activity. Here we show that sorcin significantly inhibits both the spontaneous activity of RyRs in quiescent cells (visualized as Ca2+ sparks) and the ICa-triggered activity of RyRs that gives rise to [Ca2+]i transients. Because sorcin decreased the amplitude of the [Ca2+]i transient without affecting the amplitude or kinetics of ICa, the overall effect of sorcin was to reduce the "gain" of excitation-contraction coupling. Immunocytochemical staining shows that sorcin localizes to the dyadic space of ventricular cardiac myocytes. Ca2+ induces conformational changes and promotes translocation of sorcin between soluble and membranous compartments, but the [Ca2+] required for the latter process (ED50 = approximately 200 microM) appears to be reached only within the dyadic space. Rapid injection of 5 microM sorcin onto the cytosolic face of RyRs reconstituted in lipid bilayers resulted in complete inhibition of channel activity in < or = 20 ms. Thus, sorcin is a potent inhibitor of both spontaneous and ICa-triggered RyR activity and is kinetically capable of playing a role in terminating the positive feedback loop of CICR.
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Affiliation(s)
- Emily F Farrell
- Department of Physiology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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21
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Herr C, Clemen CS, Lehnert G, Kutschkow R, Picker SM, Gathof BS, Zamparelli C, Schleicher M, Noegel AA. Function, expression and localization of annexin A7 in platelets and red blood cells: insights derived from an annexin A7 mutant mouse. BMC BIOCHEMISTRY 2003; 4:8. [PMID: 12925238 PMCID: PMC194730 DOI: 10.1186/1471-2091-4-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Accepted: 08/19/2003] [Indexed: 11/13/2022]
Abstract
BACKGROUND Annexin A7 is a Ca2+- and phospholipid-binding protein expressed as a 47 and 51 kDa isoform, which is thought to be involved in membrane fusion processes. Recently the 47 kDa isoform has been identified in erythrocytes where it was proposed to be a key component in the process of the Ca2+-dependent vesicle release, a process with which red blood cells might protect themselves against an attack by for example complement components. RESULTS The role of annexin A7 in red blood cells was addressed in erythrocytes from anxA7-/- mice. Interestingly, the Ca2+-mediated vesiculation process was not impaired. Also, the membrane organization appeared not to be disturbed as assessed using gradient fractionation studies. Instead, lack of annexin A7 led to an altered cell shape and increased osmotic resistance of red blood cells. Annexin A7 was also identified in platelets. In these cells its loss led to a slightly slower aggregation velocity which seems to be compensated by an increased number of platelets. The results appear to rule out an important role of annexin A7 in membrane fusion processes occurring in red blood cells. Instead the protein might be involved in the organization of the membrane cytoskeleton. Red blood cells may represent an appropriate model to study the role of annexin A7 in cellular processes. CONCLUSION We have demonstrated the presence of both annexin A7 isoforms in red blood cells and the presence of the small isoform in platelets. In both cell types the loss of annexin A7 impairs cellular functions. The defects observed are however not compatible with a crucial role for annexin A7 in membrane fusion processes in these cell types.
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Affiliation(s)
- Claudia Herr
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Christoph S Clemen
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Gisela Lehnert
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
| | - Rüdiger Kutschkow
- Institute for Clinical Chemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 9, 50924 Cologne, Germany
| | - Susanne M Picker
- Transfusion Medicine, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 9, 50924 Cologne, Germany
| | - Birgit S Gathof
- Transfusion Medicine, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 9, 50924 Cologne, Germany
| | - Carlotta Zamparelli
- Centro Biologia Molecolare CNR, Dipartimento di Scienze Biochimiche, Universita La Sapienza, P.le A. Moro, 5, 00185 Roma, Italy
| | - Michael Schleicher
- Institut für Zellbiologie, Ludwig-Maximilians-Universität München, Germany
| | - Angelika A Noegel
- Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany
- Center for Molecular Medicine Cologne, Germany
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Meyers MB, Fischer A, Sun YJ, Lopes CMB, Rohacs T, Nakamura TY, Zhou YY, Lee PC, Altschuld RA, McCune SA, Coetzee WA, Fishman GI. Sorcin regulates excitation-contraction coupling in the heart. J Biol Chem 2003; 278:28865-71. [PMID: 12754254 DOI: 10.1074/jbc.m302009200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sorcin is a penta-EF hand Ca2+-binding protein that associates with both cardiac ryanodine receptors and L-type Ca2+ channels and has been implicated in the regulation of intracellular Ca2+ cycling. To better define the function of sorcin, we characterized transgenic mice in which sorcin was overexpressed in the heart. Transgenic mice developed normally with no evidence of cardiac hypertrophy and no change in expression of other calcium regulatory proteins. In vivo hemodynamics revealed significant reductions in global indices of contraction and relaxation. Contractile abnormalities were also observed in isolated adult transgenic myocytes, along with significant depression of Ca2+ transient amplitudes. Whole cell ICa density and the time course of activation were normal in transgenic myocytes, but the rate of inactivation was significantly accelerated. These effects of sorcin on L-type Ca2+ currents were confirmed in Xenopus oocyte expression studies. Finally, we examined the expression of sorcin in normal and failing hearts from spontaneous hypertensive heart failure rats. In normal myocardium, sorcin extensively co-localized with ryanodine receptors at the Z-lines, whereas in myopathic hearts the degree of co-localization was markedly disrupted. Together, these data indicate that sorcin modulates intracellular Ca2+ cycling and Ca2+ influx pathways in the heart.
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Affiliation(s)
- Marian B Meyers
- Department of Medicine and Pediatrics, New York University School of Medicine, New York, New York, 10016, USA
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Mella M, Colotti G, Zamparelli C, Verzili D, Ilari A, Chiancone E. Information transfer in the penta-EF-hand protein sorcin does not operate via the canonical structural/functional pairing. A study with site-specific mutants. J Biol Chem 2003; 278:24921-8. [PMID: 12711611 DOI: 10.1074/jbc.m213276200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sorcin is a typical penta-EF-hand protein that participates in Ca2+-regulated processes by translocating reversibly from cytosol to membranes, where it interacts with different target proteins in different tissues. Binding of two Ca2+/monomer triggers translocation, although EF1, EF2, and EF3 are potentially able to bind calcium at micromolar concentrations. To identify the functional pair, the conserved bidentate -Z glutamate in these EF-hands was mutated to yield E53Q-, E94A-, and E124A-sorcin, respectively. Limited structural perturbations occur only in E124A-sorcin due to involvement of Glu-124 in a network of interactions that comprise the long D helix connecting EF3 to EF2. The overall affinity for Ca2+ and for two sorcin targets, annexin VII and the ryanodine receptor, follows the order wild-type > E53Q- > E94A- > E124A-sorcin, indicating that disruption of EF3 has the largest functional impact and that disruption of EF2 and EF1 has progressively smaller effects. Based on this experimental evidence, EF3 and EF2, which are not paired in the canonical manner, are the functional EF-hands. Sorcin is proposed to be activated upon Ca2+ binding to EF3 and transmission of the conformational change at Glu-124 via the D helix to EF2 and from there to EF1 via the canonical structural/functional pairing. This mechanism may be applicable to all penta-EF-hand proteins.
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Affiliation(s)
- Manuela Mella
- Consiglio Nazionale delle Ricerche Institute of Molecular Biology and Pathology, Department of Biochemical Sciences A. Rossi Fanelli, University of Rome La Sapienza, Italy
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Maki M, Kitaura Y, Satoh H, Ohkouchi S, Shibata H. Structures, functions and molecular evolution of the penta-EF-hand Ca2+-binding proteins. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1600:51-60. [PMID: 12445459 DOI: 10.1016/s1570-9639(02)00444-2] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Penta-EF-hand (PEF) proteins comprise a family of Ca(2+)-binding proteins that have five repetitive EF-hand motifs. Among the eight alpha-helices (alpha1-alpha8), alpha4 and alpha7 link EF2-EF3 and EF4-EF5, respectively. In addition to the structural similarities in the EF-hand regions, the PEF protein family members have common features: (i) dimerization through unpaired C-terminal EF5s, (ii) possession of hydrophobic Gly/Pro-rich N-terminal domains, and (iii) Ca(2+)-dependent translocation to membranes. Based on comparison of amino acid sequences, mammalian PEF proteins are classified into two groups: Group I PEF proteins (ALG-2 and peflin) and Group II PEF proteins (Ca(2+)-dependent protease calpain subfamily members, sorcin and grancalcin). The Group I genes have also been found in lower animals, plants, fungi and protists. Recent findings of specific interacting proteins have started to gradually unveil the functions of the noncatalytic mammalian PEF proteins.
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Affiliation(s)
- Masatoshi Maki
- Laboratory of Molecular and Cellular Regulation, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan.
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Aubry L, Mattei S, Blot B, Sadoul R, Satre M, Klein G. Biochemical characterization of two analogues of the apoptosis-linked gene 2 protein in Dictyostelium discoideum and interaction with a physiological partner in mammals, murine Alix. J Biol Chem 2002; 277:21947-54. [PMID: 11927596 DOI: 10.1074/jbc.m201718200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two homologues, Dd-ALG-2a and Dd-ALG-2b, of the mammalian calcium-binding protein ALG-2 (apoptosis-linked gene 2) have been characterized in the cellular slime mold Dictyostelium discoideum. Fluorescence titrations showed that both proteins bind calcium ions with affinities (Ca2+)(0.5) of 30 and 450 microm, respectively, at sites specific to calcium. Calcium ion binding resulted in changes of conformation associated with the unmasking of hydrophobic regions of the proteins. Surface plasmon resonance analysis showed that Dd-ALG-2a homodimers formed (K(D) of 1 microm) at calcium ion concentrations similar to those necessary for Ca2+-induced conformational changes. Deletion of the hydrophobic N-terminal sequence or EF-hand 5 of Dd-ALG-2a prevented dimerization. The Dd-ALG-2b homodimer was not detected, and the Dd-ALG-2a/2b heterodimer formed only when Dd-ALG-2b was the immobilized partner. Murine Alix formed a heterodimer (K(D) = 0.6 microm) with Dd-ALG-2a but not with Dd-ALG-2b, and the interaction strictly depended upon calcium ions. The DeltaNter construct of Dd-ALG-2a lost its interaction capacity with mouse Alix. The genes encoding both proteins, Dd-alg-2a and -2b, were expressed in growing cells. The levels of mRNA were at a maximum during aggregation (4-8 h) and decreased rapidly thereafter. In contrast, the levels of proteins remained fairly stable. Dd-ALG-2a and Dd-ALG-2b were found to be dispensable for growth and development, based on the finding that single Dd-alg2a- or Dd-alg-2b- and double Dd-alg2a-/Dd-alg-2b- mutant cell lines showed normal growth in axenic medium or on bacterial lawns and exhibited unaltered development.
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Affiliation(s)
- Laurence Aubry
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, Unité Mixte de Recherche 5092 CNRS-Commissariat à l'Energie Atomique-Université Joseph-Fourier, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
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Salzer U, Hinterdorfer P, Hunger U, Borken C, Prohaska R. Ca(++)-dependent vesicle release from erythrocytes involves stomatin-specific lipid rafts, synexin (annexin VII), and sorcin. Blood 2002; 99:2569-77. [PMID: 11895795 DOI: 10.1182/blood.v99.7.2569] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cytosolic Ca(++) induces the shedding of microvesicles and nanovesicles from erythrocytes. Atomic force microscopy was used to determine the sizes of these vesicles and to resolve the patchy, fine structure of the microvesicle membrane. The vesicles are highly enriched in glycosyl phosphatidylinositol-linked proteins, free of cytoskeletal components, and depleted of the major transmembrane proteins. Both types of vesicles contain 2 as-yet-unrecognized red cell proteins, synexin and sorcin, which translocate from the cytosol to the membrane upon Ca(++) binding. In nanovesicles, synexin and sorcin are the most abundant proteins after hemoglobin. In contrast, the microvesicles are highly enriched in stomatin. The membranes of both microvesicles and nanovesicles contain lipid rafts. Stomatin is the major protein of the microvesicular lipid rafts, whereas synexin and sorcin represent the major proteins of the nanovesicular rafts in the presence of Ca(++). Interestingly, the raft proteins flotillin-1 and flotillin-2 are not found in the vesicles but remain in the red cell membrane. These data indicate the presence of different types of lipid rafts in the erythrocyte membrane with distinct fates after Ca(++) entry. Synexin, which is known to be vital to the process of membrane fusion, is suggested to be a key component in the process of vesicle release from erythrocytes.
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Affiliation(s)
- Ulrich Salzer
- Institute of Medical Biochemistry, Biocenter, University of Vienna, Dr Bohr-Gasse 9/3, A-1030 Vienna, Austria
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Ilari A, Johnson KA, Nastopoulos V, Verzili D, Zamparelli C, Colotti G, Tsernoglou D, Chiancone E. The crystal structure of the sorcin calcium binding domain provides a model of Ca2+-dependent processes in the full-length protein. J Mol Biol 2002; 317:447-58. [PMID: 11922676 DOI: 10.1006/jmbi.2002.5417] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sorcin is a 21.6 kDa calcium binding protein, expressed in a number of mammalian tissues that belongs to the small, recently identified penta-EF-hand (PEF) family. Like all members of this family, sorcin undergoes a Ca2+-dependent translocation from cytosol to membranes where it binds to target proteins. For sorcin, the targets differ in different tissues, indicating that it takes part in a number of Ca2+-regulated processes. The sorcin monomer is organized in two domains like in all PEF proteins: a flexible, hydrophobic, glycine-rich N-terminal region and a calcium binding C-terminal domain. In vitro, the PEF proteins are dimeric in their Ca2+-free form, but have a marked tendency to precipitate when bound to calcium. Stabilization of the dimeric structure is achieved by pairing of the uneven EF-hand, EF5. Sorcin can also form tetramers at acid pH. The sorcin calcium binding domain (SCBD, residues 33-198) expressed in Escherichia coli was crystallized in the Ca2+-free form. The structure was solved by molecular replacement and was refined to 2.2 A with a crystallographic R-factor of 22.4 %. Interestingly, the asymmetric unit contains two dimers. The structure of the SCBD leads to a model that explains the solution properties and describes the Ca2+-induced conformational changes. Phosphorylation studies show that the N-terminal domain hinders phosphorylation of SCBD, i.e. the rate of phosphorylation increased twofold in the absence of the N-terminal region. In addition, previous fluorescence studies indicated that hydrophobic residues are exposed to solvent upon Ca2+ binding to full-length sorcin. The model accounts for these data by proposing that Ca2+ binding weakens the interactions between the two domains and leads to their reorientation, which exposes hydrophobic regions facilitating the Ca2+-dependent binding to target proteins at or near membranes.
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Affiliation(s)
- Andrea Ilari
- CNR, Centro Studio sulla Biologia Molecolare and Dipartimento di Scienze Biochimiche, Università La Sapienza, P.le Aldo Moro 5, Roma, 00185, Italy
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Xie X, Dwyer MD, Swenson L, Parker MH, Botfield MC. Crystal structure of calcium-free human sorcin: a member of the penta-EF-hand protein family. Protein Sci 2001; 10:2419-25. [PMID: 11714909 PMCID: PMC2374028 DOI: 10.1110/ps.36701] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sorcin is a 22 kD calcium-binding protein that is found in a wide variety of cell types, such as heart, muscle, brain and adrenal medulla. It belongs to the penta-EF-hand (PEF) protein family, which contains five EF-hand motifs that associate with membranes in a calcium-dependent manner. Prototypic members of this family are the calcium-binding domains of calpain, such as calpain dVI. Full-length human sorcin has been crystallized in the absence of calcium and the structure determined at 2.2 A resolution. Apart from an extended N-terminal portion, the sorcin molecule has a globular shape. The C-terminal domain is predominantly alpha-helical, containing eight alpha-helices and connecting loops incorporating five EF hands. Sorcin forms dimers through the association of the unpaired EF5, confirming this as the mode of association in the dimerization of PEF proteins. Comparison with calpain dVI reveals that the general folds of the individual EF-hand motifs are conserved, especially that of EF1, the novel EF-hand motif characteristic of the family. Detailed structural comparisons of sorcin with other members of PEF indicate that the EF-hand pair EF1-EF2 is likely to correspond to the two physiologically relevant calcium-binding sites and that the calcium-induced conformational change may be modest and localized within this pair of EF-hands. Overall, the results derived from the structural observations support the view that, in sorcin, calcium signaling takes place through the first pair of EF-hands.
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Affiliation(s)
- X Xie
- Vertex Pharmaceuticals Incorporated, Cambridge, Massachusetts 02139-4211, USA.
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