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Jia Z, Yu W, Li J, Zhang M, Zhan B, Yan L, Ming Z, Cheng Y, Tian X, Shao S, Huang J, Zhu X. Crystal structure of Trichinella spiralis calreticulin and the structural basis of its complement evasion mechanism involving C1q. Front Immunol 2024; 15:1404752. [PMID: 38690267 PMCID: PMC11059001 DOI: 10.3389/fimmu.2024.1404752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Accepted: 03/25/2024] [Indexed: 05/02/2024] Open
Abstract
Helminths produce calreticulin (CRT) to immunomodulate the host immune system as a survival strategy. However, the structure of helminth-derived CRT and the structural basis of the immune evasion process remains unclarified. Previous study found that the tissue-dwelling helminth Trichinella spiralis produces calreticulin (TsCRT), which binds C1q to inhibit activation of the complement classical pathway. Here, we used x-ray crystallography to resolve the structure of truncated TsCRT (TsCRTΔ), the first structure of helminth-derived CRT. TsCRTΔ was observed to share the same binding region on C1q with IgG based on the structure and molecular docking, which explains the inhibitory effect of TsCRT on C1q-IgG-initiated classical complement activation. Based on the key residues in TsCRTΔ involved in the binding activity to C1q, a 24 amino acid peptide called PTsCRT was constructed that displayed strong C1q-binding activity and inhibited C1q-IgG-initiated classical complement activation. This study is the first to elucidate the structural basis of the role of TsCRT in immune evasion, providing an approach to develop helminth-derived bifunctional peptides as vaccine target to prevent parasite infections or as a therapeutic agent to treat complement-related autoimmune diseases.
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Affiliation(s)
- Zhihui Jia
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Wen Yu
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Jingmo Li
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Mingming Zhang
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Bin Zhan
- Departments of Pediatrics and Molecular Virology and Microbiology, National School of Tropical Medicine, Baylor College of Medicine, Houston, TX, United States
| | - Liming Yan
- Ministry of Education Key Laboratory of Protein Science, School of Medicine, Tsinghua University, Beijing, China
| | - Zhenhua Ming
- College of Life Science and Technology, Guangxi University, Nanning, China
| | - Yuli Cheng
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Xiaolin Tian
- Ministry of Education Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, China
| | - Shuai Shao
- Beijing institute of Clinical Medicine, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China
| | - Jingjing Huang
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Xinping Zhu
- Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
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Maor-Landaw K, Avidor I, Rostowsky N, Salti B, Smirnov M, Ofek-Lalzar M, Levin L, Brekhman V, Lotan T. The Molecular Mechanisms Employed by the Parasite Myxobolus bejeranoi (Cnidaria: Myxozoa) from Invasion through Sporulation for Successful Proliferation in Its Fish Host. Int J Mol Sci 2023; 24:12824. [PMID: 37629003 PMCID: PMC10454682 DOI: 10.3390/ijms241612824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Revised: 08/08/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023] Open
Abstract
Myxozoa is a unique group of obligate endoparasites in the phylum Cnidaria that can cause emerging diseases in wild and cultured fish populations. Recently, we identified a new myxozoan species, Myxobolus bejeranoi, which infects the gills of cultured tilapia while suppressing host immunity. To uncover the molecular mechanisms underlying this successful parasitic strategy, we conducted transcriptomics analysis of M. bejeranoi throughout the infection. Our results show that histones, which are essential for accelerated cell division, are highly expressed even one day after invasion. As the infection progressed, conserved parasitic genes that are known to modulate the host immune reaction in different parasitic taxa were upregulated. These genes included energy-related glycolytic enzymes, as well as calreticulin, proteases, and miRNA biogenesis proteins. Interestingly, myxozoan calreticulin formed a distinct phylogenetic clade apart from other cnidarians, suggesting a possible function in parasite pathogenesis. Sporogenesis was in its final stages 20 days post-exposure, as spore-specific markers were highly expressed. Lastly, we provide the first catalog of transcription factors in a Myxozoa species, which is minimized compared to free-living cnidarians and is dominated by homeodomain types. Overall, these molecular insights into myxozoan infection support the concept that parasitic strategies are a result of convergent evolution.
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Affiliation(s)
- Keren Maor-Landaw
- Marine Biology Department, The Leon H. Charney School of Marine Sciences, University of Haifa, Mt. Carmel, Haifa 3103301, Israel; (K.M.-L.); (I.A.); (N.R.); (B.S.); (V.B.)
| | - Itamar Avidor
- Marine Biology Department, The Leon H. Charney School of Marine Sciences, University of Haifa, Mt. Carmel, Haifa 3103301, Israel; (K.M.-L.); (I.A.); (N.R.); (B.S.); (V.B.)
| | - Nadav Rostowsky
- Marine Biology Department, The Leon H. Charney School of Marine Sciences, University of Haifa, Mt. Carmel, Haifa 3103301, Israel; (K.M.-L.); (I.A.); (N.R.); (B.S.); (V.B.)
| | - Barbara Salti
- Marine Biology Department, The Leon H. Charney School of Marine Sciences, University of Haifa, Mt. Carmel, Haifa 3103301, Israel; (K.M.-L.); (I.A.); (N.R.); (B.S.); (V.B.)
| | - Margarita Smirnov
- Central Fish Health Laboratory, Department of Fisheries and Aquaculture, Ministry of Agriculture and Rural Development, Nir David 1080300, Israel;
| | - Maya Ofek-Lalzar
- Bioinformatic Unit, University of Haifa, Mt. Carmel, Haifa 3498838, Israel;
| | - Liron Levin
- Bioinformatics Core Facility, llse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel;
| | - Vera Brekhman
- Marine Biology Department, The Leon H. Charney School of Marine Sciences, University of Haifa, Mt. Carmel, Haifa 3103301, Israel; (K.M.-L.); (I.A.); (N.R.); (B.S.); (V.B.)
| | - Tamar Lotan
- Marine Biology Department, The Leon H. Charney School of Marine Sciences, University of Haifa, Mt. Carmel, Haifa 3103301, Israel; (K.M.-L.); (I.A.); (N.R.); (B.S.); (V.B.)
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3
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Desikan H, Kaur A, Pogozheva ID, Raghavan M. Effects of calreticulin mutations on cell transformation and immunity. J Cell Mol Med 2023; 27:1032-1044. [PMID: 36916035 PMCID: PMC10098294 DOI: 10.1111/jcmm.17713] [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: 11/04/2022] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 03/16/2023] Open
Abstract
Myeloproliferative neoplasms (MPNs) are cancers involving dysregulated production and function of myeloid lineage hematopoietic cells. Among MPNs, Essential thrombocythemia (ET), Polycythemia Vera (PV) and Myelofibrosis (MF), are driven by mutations that activate the JAK-STAT signalling pathway. Somatic mutations of calreticulin (CRT), an endoplasmic reticulum (ER)-localized lectin chaperone, are driver mutations in approximately 25% of ET and 35% of MF patients. The MPN-linked mutant CRT proteins have novel frameshifted carboxy-domain sequences and lack an ER retention motif, resulting in their secretion. Wild type CRT is a regulator of ER calcium homeostasis and plays a key role in the assembly of major histocompatibility complex (MHC) class I molecules, which are the ligands for antigen receptors of CD8+ T cells. Mutant CRT-linked oncogenesis results from the dysregulation of calcium signalling in cells and the formation of stable complexes of mutant CRT with myeloproliferative leukemia (MPL) protein, followed by downstream activation of the JAK-STAT signalling pathway. The intricate participation of CRT in ER protein folding, calcium homeostasis and immunity suggests the involvement of multiple mechanisms of mutant CRT-linked oncogenesis. In this review, we highlight recent findings related to the role of MPN-linked CRT mutations in the dysregulation of calcium homeostasis, MPL activation and immunity.
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Affiliation(s)
- Harini Desikan
- Department of Microbiology and ImmunologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
| | - Amanpreet Kaur
- Department of Microbiology and ImmunologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
| | - Irina D. Pogozheva
- Department of Medicinal ChemistryCollege of Pharmacy, University of MichiganAnn ArborMichiganUSA
| | - Malini Raghavan
- Department of Microbiology and ImmunologyUniversity of Michigan Medical SchoolAnn ArborMichiganUSA
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4
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Structural and Dynamic Differences between Calreticulin Mutants Associated with Essential Thrombocythemia. Biomolecules 2023; 13:biom13030509. [PMID: 36979444 PMCID: PMC10046389 DOI: 10.3390/biom13030509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/28/2023] [Accepted: 03/03/2023] [Indexed: 03/12/2023] Open
Abstract
Essential thrombocythemia (ET) is a blood cancer. ET is characterized by an overproduction of platelets that can lead to thrombosis formation. Platelet overproduction occurs in megakaryocytes through a signaling pathway that could involve JAK2, MPL, or CALR proteins. CALR mutations are associated with 25–30% of ET patients; CALR variants must be dimerized to induce ET. We classified these variants into five classes named A to E; classes A and B are the most frequent classes in patients with ET. The dynamic properties of these five classes using structural models of CALR’s C-domain were analyzed using molecular dynamics simulations. Classes A, B, and C are associated with frameshifts in the C-domain. Their dimers can be stable only if a disulfide bond is formed; otherwise, the two monomers repulse each other. Classes D and E cannot be stable as dimers due to the absence of disulfide bonds. Class E and wild-type CALR have similar dynamic properties. These results suggest that the disulfide bond newly formed in classes A, B, and C may be essential for the pathogenicity of these variants. They also underline that class E cannot be directly related to ET but corresponds to human polymorphisms.
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Esperante D, Flisser A, Mendlovic F. The many faces of parasite calreticulin. Front Immunol 2023; 14:1101390. [PMID: 36993959 PMCID: PMC10040973 DOI: 10.3389/fimmu.2023.1101390] [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: 11/17/2022] [Accepted: 01/23/2023] [Indexed: 03/16/2023] Open
Abstract
Calreticulin from parasites and its vertebrate hosts share ~50% identity and many of its functions are equally conserved. However, the existing amino acid differences can affect its biological performance. Calreticulin plays an important role in Ca2+ homeostasis and as a chaperone involved in the correct folding of proteins within the endoplasmic reticulum. Outside the endoplasmic reticulum, calreticulin is involved in several immunological functions such as complement inhibition, enhancement of efferocytosis, and immune upregulation or inhibition. Several parasite calreticulins have been shown to limit immune responses and promote infectivity, while others are strong immunogens and have been used for the development of potential vaccines that limit parasite growth. Furthermore, calreticulin is essential in the dialogue between parasites and hosts, inducing Th1, Th2 or regulatory responses in a species-specific manner. In addition, calreticulin participates as initiator of endoplasmic reticulum stress in tumor cells and promotion of immunogenic cell death and removal by macrophages. Direct anti-tumoral activity has also been reported. The highly immunogenic and pleiotropic nature of parasite calreticulins, either as positive or negative regulators of the immune response, render these proteins as valuable tools to modulate immunopathologies and autoimmune disorders, as well as a potential treatment of neoplasms. Moreover, the disparities in the amino acid composition of parasite calreticulins might provide subtle variations in the mechanisms of action that could provide advantages as therapeutic tools. Here, we review the immunological roles of parasite calreticulins and discuss possible beneficial applications.
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Affiliation(s)
- Diego Esperante
- Plan de Estudios Combinados en Medicina (PECEM), Facultad de Medicine, Universidad Nacional Autonóma de México (UNAM), Mexico City, Mexico
| | - Ana Flisser
- Plan de Estudios Combinados en Medicina (PECEM), Facultad de Medicine, Universidad Nacional Autonóma de México (UNAM), Mexico City, Mexico
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autonóma de México (UNAM), Mexico City, Mexico
| | - Fela Mendlovic
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autonóma de México (UNAM), Mexico City, Mexico
- Facultad de Ciencias de la Salud, Universidad Anahuac Mexico Norte, Huixquilucan, Mexico
- *Correspondence: Fela Mendlovic,
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Mamidi AS, Surolia A. Mixed mechanism of conformational selection and induced fit as a molecular recognition process in the calreticulin family of proteins. PLoS Comput Biol 2022; 18:e1010661. [PMID: 36508460 PMCID: PMC9744295 DOI: 10.1371/journal.pcbi.1010661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 10/17/2022] [Indexed: 12/14/2022] Open
Abstract
The fundamental question on the mechanism of molecular recognition during ligand binding has attracted a lot of scientific scrutiny. The two competing theories of ligand binding-"induced fit" and "conformational selection" have been proposed to explain biomolecular recognition. Since exploring a family of proteins with similar structural architectures and conserved functional roles can provide valuable insight into the significance of molecular structure and function, we performed molecular dynamics simulations on the calreticulin family of proteins, which specifically recognize monoglucosylated N-glycan during the protein folding process. Atomistic simulations of lectins in free and bound forms demonstrated that they exist in several conformations spanning from favorable to unfavorable for glycan binding. Our analysis was confined to the carbohydrate recognition domain (CRD) of these lectins to demonstrate the degree of conservation in protein sequence and structure and relate them with their function. Furthermore, we computed the lectin-glycan binding affinity using the mmPBSA approach to identify the most favorable lectin conformation for glycan binding and compared the molecular interaction fields in terms of noncovalent bond interactions. We also demonstrated the involvement of Tyr and Trp residues in the CRD with the non-reducing end glucose and central mannose residues, which contribute to some of the specific interactions. Furthermore, we analyzed the conformational changes in the CRD through SASA, RMSFs and protein surface topography mapping of electrostatic and hydrophobic potentials. Our findings demonstrate a hybrid mechanism of molecular recognition, initially driven by conformational selection followed by glycan-induced fluctuations in the key residues to strengthen the glycan binding interactions.
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Affiliation(s)
| | - Avadhesha Surolia
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore–India
- * E-mail: (ASM); (AS)
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7
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Ramírez-Toloza G, Aguilar-Guzmán L, Valck C, Menon SS, Ferreira VP, Ferreira A. Is It Possible to Intervene in the Capacity of Trypanosoma cruzi to Elicit and Evade the Complement System? Front Immunol 2021; 12:789145. [PMID: 34975884 PMCID: PMC8716602 DOI: 10.3389/fimmu.2021.789145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 11/19/2021] [Indexed: 11/23/2022] Open
Abstract
Chagas' disease is a zoonotic parasitic ailment now affecting more than 6 million people, mainly in Latin America. Its agent, the protozoan Trypanosoma cruzi, is primarily transmitted by endemic hematophagous triatomine insects. Transplacental transmission is also important and a main source for the emerging global expansion of this disease. In the host, the parasite undergoes intra (amastigotes) and extracellular infective (trypomastigotes) stages, both eliciting complex immune responses that, in about 70% of the cases, culminate in permanent immunity, concomitant with the asymptomatic presence of the parasite. The remaining 30% of those infected individuals will develop a syndrome, with variable pathological effects on the circulatory, nervous, and digestive systems. Herein, we review an important number of T. cruzi molecules, mainly located on its surface, that have been characterized as immunogenic and protective in various experimental setups. We also discuss a variety of parasite strategies to evade the complement system - mediated immune responses. Within this context, we also discuss the capacity of the T. cruzi infective trypomastigote to translocate the ER-resident chaperone calreticulin to its surface as a key evasive strategy. Herein, it is described that T. cruzi calreticulin inhibits the initial stages of activation of the host complement system, with obvious benefits for the parasite. Finally, we speculate on the possibility to experimentally intervene in the interaction of calreticulin and other T. cruzi molecules that interact with the complement system; thus resulting in significant inhibition of T. cruzi infectivity.
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Affiliation(s)
- Galia Ramírez-Toloza
- Department of Preventive Veterinary Medicine, Faculty of Veterinary Medicine and Livestock Sciences, University of Chile, Santiago, Chile
| | - Lorena Aguilar-Guzmán
- Department of Pathology, Faculty of Veterinary Medicine and Livestock Sciences, University of Chile, Santiago, Chile
| | - Carolina Valck
- Department of Immunology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
| | - Smrithi S. Menon
- Department of Medical Microbiology and Immunology, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Viviana P. Ferreira
- Department of Medical Microbiology and Immunology, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Arturo Ferreira
- Department of Immunology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
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8
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Venkatesan A, Geng J, Kandarpa M, Wijeyesakere SJ, Bhide A, Talpaz M, Pogozheva ID, Raghavan M. Mechanism of mutant calreticulin-mediated activation of the thrombopoietin receptor in cancers. J Cell Biol 2021; 220:212031. [PMID: 33909030 PMCID: PMC8085772 DOI: 10.1083/jcb.202009179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 02/10/2021] [Accepted: 03/17/2021] [Indexed: 12/21/2022] Open
Abstract
Myeloproliferative neoplasms (MPNs) are frequently driven by mutations within the C-terminal domain (C-domain) of calreticulin (CRT). CRTDel52 and CRTIns5 are recurrent mutations. Oncogenic transformation requires both mutated CRT and the thrombopoietin receptor (Mpl), but the molecular mechanism of CRT-mediated constitutive activation of Mpl is unknown. We show that the acquired C-domain of CRTDel52 mediates both Mpl binding and disulfide-linked CRTDel52 dimerization. Cysteine mutations within the novel C-domain (C400A and C404A) and the conserved N-terminal domain (N-domain; C163A) of CRTDel52 are required to reduce disulfide-mediated dimers and multimers of CRTDel52. Based on these data and published structures of CRT oligomers, we identify an N-domain dimerization interface relevant to both WT CRT and CRTDel52. Elimination of disulfide bonds and ionic interactions at both N-domain and C-domain dimerization interfaces is required to abrogate the ability of CRTDel52 to mediate cell proliferation via Mpl. Thus, MPNs exploit a natural dimerization interface of CRT combined with C-domain gain of function to achieve cell transformation.
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Affiliation(s)
- Arunkumar Venkatesan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
| | - Jie Geng
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
| | - Malathi Kandarpa
- Department of Internal Medicine/Division of Hematology/Oncology, University of Michigan Rogel Cancer Center, Ann Arbor, MI
| | | | - Ashwini Bhide
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
| | - Moshe Talpaz
- Department of Internal Medicine/Division of Hematology/Oncology, University of Michigan Rogel Cancer Center, Ann Arbor, MI
| | - Irina D Pogozheva
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI
| | - Malini Raghavan
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
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Roles of Calreticulin in Protein Folding, Immunity, Calcium Signaling and Cell Transformation. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 59:145-162. [PMID: 34050865 DOI: 10.1007/978-3-030-67696-4_7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The endoplasmic reticulum (ER) is an organelle that mediates the proper folding and assembly of proteins destined for the cell surface, the extracellular space and subcellular compartments such as the lysosomes. The ER contains a wide range of molecular chaperones to handle the folding requirements of a diverse set of proteins that traffic through this compartment. The lectin-like chaperones calreticulin and calnexin are an important class of structurally-related chaperones relevant for the folding and assembly of many N-linked glycoproteins. Despite the conserved mechanism of action of these two chaperones in nascent protein recognition and folding, calreticulin has unique functions in cellular calcium signaling and in the immune response. The ER-related functions of calreticulin in the assembly of major histocompatibility complex (MHC) class I molecules are well-studied and provide many insights into the modes of substrate and co-chaperone recognition by calreticulin. Calreticulin is also detectable on the cell surface under some conditions, where it induces the phagocytosis of apoptotic cells. Furthermore, mutations of calreticulin induce cell transformation in myeloproliferative neoplasms (MPN). Studies of the functions of the mutant calreticulin in cell transformation and immunity have provided many insights into the normal biology of calreticulin, which are discussed.
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Structural Analysis of Calreticulin, an Endoplasmic Reticulum-Resident Molecular Chaperone. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 59:13-25. [PMID: 34050860 DOI: 10.1007/978-3-030-67696-4_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Calreticulin (Calr) is an endoplasmic reticulum (ER) chaperone involved in protein quality control, Ca2+ regulation and other cellular processes. The structure of Calr is unusual, reflecting different functions of the protein: a proline-rich β-hairpin arm and an acidic C-terminal tail protrude from a globular core, composed of a β-sheet sandwich and an α-helix. The arm and tail interact in the presence of Ca2+ and cover the upper β-sheet, where a carbohydrate-binding site gives the chaperone glycoprotein affinity. At the edge of the carbohydrate-binding site is a conserved, strained disulphide bridge, formed between C106 and C137 of human Calr, which lies in a polypeptide-binding site. The lower β-sheet has several conserved residues, comprised of a characteristic triad, D166-H170-D187, Tyr172 and the free C163. In addition to its role in the ER, Calr translocates to the cell surface upon stress and functions as an immune surveillance marker. In some myeloproliferative neoplasms, the acidic Ca2+-binding C-terminal tail is transformed into a polybasic sequence.
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11
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Kozlov G, Gehring K. Calnexin cycle - structural features of the ER chaperone system. FEBS J 2020; 287:4322-4340. [PMID: 32285592 PMCID: PMC7687155 DOI: 10.1111/febs.15330] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 03/31/2020] [Accepted: 04/08/2020] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum (ER) is the major folding compartment for secreted and membrane proteins and is the site of a specific chaperone system, the calnexin cycle, for folding N-glycosylated proteins. Recent structures of components of the calnexin cycle have deepened our understanding of quality control mechanisms and protein folding pathways in the ER. In the calnexin cycle, proteins carrying monoglucosylated glycans bind to the lectin chaperones calnexin and calreticulin, which recruit a variety of function-specific chaperones to mediate protein disulfide formation, proline isomerization, and general protein folding. Upon trimming by glucosidase II, the glycan without an inner glucose residue is no longer able to bind to the lectin chaperones. For proteins that have not yet folded properly, the enzyme UDP-glucose:glycoprotein glucosyltransferase (UGGT) acts as a checkpoint by adding a glucose back to the N-glycan. This allows the misfolded proteins to re-associate with calnexin and calreticulin for additional rounds of chaperone-mediated refolding and prevents them from exiting the ERs. Here, we review progress in structural studies of the calnexin cycle, which reveal common features of how lectin chaperones recruit function-specific chaperones and how UGGT recognizes misfolded proteins.
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Affiliation(s)
- Guennadi Kozlov
- From the Department of Biochemistry & Centre for Structural BiologyMcGill UniversityMontréalQCCanada
| | - Kalle Gehring
- From the Department of Biochemistry & Centre for Structural BiologyMcGill UniversityMontréalQCCanada
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12
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Ramírez-Toloza G, Aguilar-Guzmán L, Valck C, Ferreira VP, Ferreira A. The Interactions of Parasite Calreticulin With Initial Complement Components: Consequences in Immunity and Virulence. Front Immunol 2020; 11:1561. [PMID: 32793217 PMCID: PMC7391170 DOI: 10.3389/fimmu.2020.01561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 06/12/2020] [Indexed: 12/17/2022] Open
Abstract
Because of its capacity to increase a physiologic inflammatory response, to stimulate phagocytosis, to promote cell lysis and to enhance pathogen immunogenicity, the complement system is a crucial component of both the innate and adaptive immune responses. However, many infectious agents resist the activation of this system by expressing or secreting proteins with a role as complement regulatory, mainly inhibitory, proteins. Trypanosoma cruzi, the causal agent of Chagas disease, a reemerging microbial ailment, possesses several virulence factors with capacity to inhibit complement at different stages of activation. T. cruzi calreticulin (TcCalr) is a highly-conserved, endoplasmic reticulum-resident chaperone that the parasite translocates to the extracellular environment, where it exerts a variety of functions. Among these functions, TcCalr binds C1, MBL and ficolins, thus inhibiting the classical and lectin pathways of complement at their earliest stages of activation. Moreover, the TcCalr/C1 interaction also mediates infectivity by mimicking a strategy used by apoptotic cells for their removal. More recently, it has been determined that these Calr strategies are also used by a variety of other parasites. In addition, as reviewed elsewhere, TcCalr inhibits angiogenesis, promotes wound healing and reduces tumor growth. Complement C1 is also involved in some of these properties. Knowledge on the role of virulence factors, such as TcCalr, and their interactions with complement components in host-parasite interactions, may lead toward the description of new anti-parasite therapies and prophylaxis.
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Affiliation(s)
- Galia Ramírez-Toloza
- Department of Preventive Veterinary Medicine, Faculty of Veterinary Medicine and Livestock Sciences, University of Chile, Santiago, Chile
| | - Lorena Aguilar-Guzmán
- Department of Pathology, Faculty of Veterinary Medicine and Livestock Sciences, University of Chile, Santiago, Chile
| | - Carolina Valck
- Department of Immunology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Viviana P Ferreira
- Department of Medical Microbiology and Immunology, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, United States
| | - Arturo Ferreira
- Department of Immunology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile
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Abstract
Calcium signaling plays a key role in many essential processes in almost all eukaryotic systems. It is believed that it may also be an important signaling system of the protist parasite Entamoeba histolytica. Motility, adhesion, cytolysis, and phagocytosis/trogocytosis are important steps in invasion and pathogenesis of E. histolytica, and Ca2+ signaling is thought to be associated with these processes leading to tissue invasion. There are a large number of Ca2+-binding proteins (CaBPs) in E. histolytica, and a number of these proteins appear to be associated with different steps in pathogenesis. The genome encodes 27 EF-hand–containing CaBPs in addition to a number of other Ca2+-binding domain/motif-containing proteins, which suggest intricate calcium signaling network in this parasite. Unlike other eukaryotes, a typical calmodulin-like protein has not been seen in E. histolytica. Though none of the CaBPs display sequence similarity with a typical calmodulin, extensive structural similarity has been seen in spite of lack of significant functional overlap with that of typical calmodulins. One of the unique features observed in E. histolytica is the identification of CaBPs (EhCaBP1, EhCaBP3) that have the ability to directly bind actin and modulate actin dynamics. Direct interaction of CaBPs with actin has not been seen in any other system. Pseudopod formation and phagocytosis are some of the processes that require actin dynamics, and some of the amoebic CaBPs (EhC2Pk, EhCaBP1, EhCaBP3, EhCaBP5) participate in this process. None of these E. histolytica CaBPs have any homolog in organisms other than different species of Entamoeba, suggesting a novel Ca2+ signaling pathway that has evolved in this genus.
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Affiliation(s)
- Mrigya Babuta
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Sudha Bhattacharya
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Alok Bhattacharya
- Department of Biology, Ashoka University, Sonepat, Haryana, India
- * E-mail:
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14
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Ramírez-Toloza G, Sosoniuk-Roche E, Valck C, Aguilar-Guzmán L, Ferreira VP, Ferreira A. Trypanosoma cruzi Calreticulin: Immune Evasion, Infectivity, and Tumorigenesis. Trends Parasitol 2020; 36:368-381. [PMID: 32191851 DOI: 10.1016/j.pt.2020.01.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 01/25/2020] [Accepted: 01/26/2020] [Indexed: 02/06/2023]
Abstract
To successfully infect, Trypanosoma cruzi evades and modulates the host immune response. T. cruzi calreticulin (TcCalr) is a multifunctional, endoplasmic reticulum (ER)-resident chaperone that, translocated to the external microenvironment, mediates crucial host-parasite interactions. TcCalr binds and inactivates C1 and mannose-binding lectin (MBL)/ficolins, important pattern- recognition receptors (PRRs) of the complement system. Using an apoptotic mimicry strategy, the C1-TcCalr association facilitates the infection of target cells. T. cruzi infection also seems to confer protection against tumorigenesis. Thus, recombinant TcCalr has important antiangiogenic properties, detected in vitro, ex vivo, and in ovum, most likely contributing at least in part, to its antitumor properties. Consequently, TcCalr is useful for investigating key issues of host-parasite interactions and possible new immunological/pharmacological interventions in the areas of Chagas' disease and experimental cancer.
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Affiliation(s)
- Galia Ramírez-Toloza
- Faculty of Veterinary Medicine and Livestock Sciences, University of Chile, Santiago, Chile.
| | | | - Carolina Valck
- Department of Immunology, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Lorena Aguilar-Guzmán
- Faculty of Veterinary Medicine and Livestock Sciences, University of Chile, Santiago, Chile
| | - Viviana P Ferreira
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, OH, USA
| | - Arturo Ferreira
- Department of Immunology, Faculty of Medicine, University of Chile, Santiago, Chile.
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15
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Ihara Y, Ikezaki M, Takatani M, Ito Y. Calnexin/Calreticulin and Assays Related to N-Glycoprotein Folding In Vitro. Methods Mol Biol 2020; 2132:295-308. [PMID: 32306337 DOI: 10.1007/978-1-0716-0430-4_29] [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] [Indexed: 01/17/2023]
Abstract
Calnexin (CNX) and calreticulin (CRT) are ER-resident lectin-like molecular chaperones involved in the quality control of secretory or membrane glycoproteins. They can exert molecular chaperone functions via specific binding to the early processing intermediates of Glc1Man9GlcNAc2 oligosaccharides of N-glycoproteins. CNX and CRT have similar N-terminal luminal domains and share the same jelly roll tertiary structure as legume lectins. In addition to the lectin-like interactions, CNX and CRT also suppress the aggregation of non-glycosylated substrates through interaction with hydrophobic peptide parts, suggesting a general chaperone function in glycan-dependent and glycan-independent manners. This chapter describes the isolation and purification of CRT produced in a bacterial expression system. We also introduce in vitro assays to estimate the molecular chaperone functions of CRT via the interaction with monoglucosylated N-glycans using Jack bean α-mannosidase as a target substrate. These assays are valuable in assessing quality control events related to the CNX/CRT chaperone cycle and lectin functions.
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Affiliation(s)
- Yoshito Ihara
- Department of Biochemistry, Wakayama Medical University, Wakayama, Japan.
| | - Midori Ikezaki
- Department of Biochemistry, Wakayama Medical University, Wakayama, Japan
| | - Maki Takatani
- Synthetic Cellular Chemistry Laboratory, RIKEN, Saitama, Japan
| | - Yukishige Ito
- Synthetic Cellular Chemistry Laboratory, RIKEN, Saitama, Japan
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16
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Structural bases that underline Trypanosoma cruzi calreticulin proinfective, antiangiogenic and antitumor properties. Immunobiology 2019; 225:151863. [PMID: 31732192 DOI: 10.1016/j.imbio.2019.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Accepted: 10/29/2019] [Indexed: 12/24/2022]
Abstract
Microbes have developed mechanisms to resist the host immune defenses and some elicit antitumor immune responses. About 6 million people are infected with Trypanosoma cruzi, the protozoan agent of Chagas' disease, the sixth neglected tropical disease worldwide. Eighty years ago, G. Roskin and N. Klyuyeva proposed that T. cruzi infection mediates an anti-cancer activity. This observation has been reproduced by several other laboratories, but no molecular basis has been proposed. We have shown that the highly pleiotropic chaperone calreticulin (TcCalr, formerly known as TcCRT), translocates from the parasite ER to the exterior, where it mediates infection. Similar to its human counterpart HuCALR (formerly known as HuCRT), TcCalr inhibits C1 in its capacity to initiate the classical pathway of complement activation. We have also proposed that TcCalr inhibits angiogenesis and it is a likely mediator of antitumor effects. We have generated several in silico structural TcCalr models to delimit a peptide (VC-TcCalr) at the TcCalr N-domain. Chemically synthesized VC-TcCalr did bind to C1q and was anti-angiogenic in Gallus gallus chorioallantoic membrane assays. These properties were associated with structural features, as determined in silico. VC-TcCalr, a strong dipole, interacts with charged proteins such as collagen-like tails and scavenger receptors. Comparatively, HuCALR has less polarity and spatial stability, probably due to at least substitutions of Gln for Gly, Arg for Lys, Arg for Asp and Ser for Arg that hinder protein-protein interactions. These differences can explain, at least in part, how TcCalr inhibits the complement activation pathway and has higher efficiency as an antiangiogenic and antitumor agent than HuCALR.
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17
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Varricchio L, Falchi M, Dall'Ora M, De Benedittis C, Ruggeri A, Uversky VN, Migliaccio AR. Calreticulin: Challenges Posed by the Intrinsically Disordered Nature of Calreticulin to the Study of Its Function. Front Cell Dev Biol 2017; 5:96. [PMID: 29218307 PMCID: PMC5703715 DOI: 10.3389/fcell.2017.00096] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 10/31/2017] [Indexed: 12/16/2022] Open
Abstract
Calreticulin is a Ca2+-binding chaperone protein, which resides mainly in the endoplasmic reticulum but also found in other cellular compartments including the plasma membrane. In addition to Ca2+, calreticulin binds and regulates almost all proteins and most of the mRNAs deciding their intracellular fate. The potential functions of calreticulin are so numerous that identification of all of them is becoming a nightmare. Still the recent discovery that patients affected by the Philadelphia-negative myeloproliferative disorders essential thrombocytemia or primary myelofibrosis not harboring JAK2 mutations carry instead calreticulin mutations disrupting its C-terminal domain has highlighted the clinical need to gain a deeper understanding of the biological activity of this protein. However, by contrast with other proteins, such as enzymes or transcription factors, the biological functions of which are strictly defined by a stable spatial structure imprinted by their amino acid sequence, calreticulin contains intrinsically disordered regions, the structure of which represents a highly dynamic conformational ensemble characterized by constant changes between several metastable conformations in response to a variety of environmental cues. This article will illustrate the Theory of calreticulin as an intrinsically disordered protein and discuss the Hypothesis that the dynamic conformational changes to which calreticulin may be subjected by environmental cues, by promoting or restricting the exposure of its active sites, may affect its function under normal and pathological conditions.
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Affiliation(s)
- Lilian Varricchio
- Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Mario Falchi
- National HIV/AIDS Center, Istituto Superiore Sanità, Rome, Italy
| | - Massimiliano Dall'Ora
- Department of Biomedical and Neuromotorial Sciences, Alma Mater University, Bologna, Italy
| | - Caterina De Benedittis
- Department of Biomedical and Neuromotorial Sciences, Alma Mater University, Bologna, Italy
| | - Alessandra Ruggeri
- Department of Biomedical and Neuromotorial Sciences, Alma Mater University, Bologna, Italy
| | - Vladimir N Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, United States.,Laboratory of New Methods in Biology, Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Russia
| | - Anna Rita Migliaccio
- Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States.,Department of Biomedical and Neuromotorial Sciences, Alma Mater University, Bologna, Italy
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18
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Ramírez-Toloza G, Ferreira A. Trypanosoma cruzi Evades the Complement System as an Efficient Strategy to Survive in the Mammalian Host: The Specific Roles of Host/Parasite Molecules and Trypanosoma cruzi Calreticulin. Front Microbiol 2017; 8:1667. [PMID: 28919885 PMCID: PMC5585158 DOI: 10.3389/fmicb.2017.01667] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 08/17/2017] [Indexed: 12/20/2022] Open
Abstract
American Trypanosomiasis is an important neglected reemerging tropical parasitism, infecting about 8 million people worldwide. Its agent, Trypanosoma cruzi, exhibits multiple mechanisms to evade the host immune response and infect host cells. An important immune evasion strategy of T. cruzi infective stages is its capacity to inhibit the complement system activation on the parasite surface, avoiding opsonizing, immune stimulating and lytic effects. Epimastigotes, the non-infective form of the parasite, present in triatomine arthropod vectors, are highly susceptible to complement-mediated lysis while trypomastigotes, the infective form, present in host bloodstream, are resistant. Thus T. cruzi susceptibility to complement varies depending on the parasite stage (amastigote, trypomastigotes or epimastigote) and on the T. cruzi strain. To avoid complement-mediated lysis, T. cruzi trypomastigotes express on the parasite surface a variety of complement regulatory proteins, such as glycoprotein 58/68 (gp58/68), T. cruzi complement regulatory protein (TcCRP), trypomastigote decay-accelerating factor (T-DAF), C2 receptor inhibitor trispanning (CRIT) and T. cruzi calreticulin (TcCRT). Alternatively, or concomitantly, the parasite captures components with complement regulatory activity from the host bloodstream, such as factor H (FH) and plasma membrane-derived vesicles (PMVs). All these proteins inhibit different steps of the classical (CP), alternative (AP) or lectin pathways (LP). Thus, TcCRP inhibits the CP C3 convertase assembling, gp58/68 inhibits the AP C3 convertase, T-DAF interferes with the CP and AP convertases assembling, TcCRT inhibits the CP and LP, CRIT confers ability to resist the CP and LP, FH is used by trypomastigotes to inhibit the AP convertases and PMVs inhibit the CP and LP C3 convertases. Many of these proteins have similar molecular inhibitory mechanisms. Our laboratory has contributed to elucidate the role of TcCRT in the host-parasite interplay. Thus, we have proposed that TcCRT is a pleiotropic molecule, present not only in the parasite endoplasmic reticulum, but also on the trypomastigote surface, participating in key processes to establish T. cruzi infection, such as inhibition of the complement system and serving as an important virulence factor. Additionally, TcCRT interaction with key complement components, participates as an anti-angiogenic and anti-tumor molecule, inhibiting at least in important part, tumor growth in infected animals.
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Affiliation(s)
- Galia Ramírez-Toloza
- Laboratory of Parasitology, Department of Animal Preventive Medicine, Faculty of Veterinary Medicine and Livestock Sciences, University of ChileSantiago, Chile
| | - Arturo Ferreira
- Program of Immunology, Institute of Biomedical Sciences, Faculty of Medicine, University of ChileSantiago, Chile
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Migliaccio AR, Uversky VN. Dissecting physical structure of calreticulin, an intrinsically disordered Ca 2+-buffering chaperone from endoplasmic reticulum. J Biomol Struct Dyn 2017; 36:1617-1636. [PMID: 28504081 DOI: 10.1080/07391102.2017.1330224] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Calreticulin (CALR) is a Ca2+ binding multifunctional protein that mostly resides in the endoplasmic reticulum (ER) and plays a number of important roles in various physiological and pathological processes. Although the major functions ascribed to CALR are controlling the Ca2+ homeostasis in ER and acting as a lectin-like ER chaperon for many glycoproteins, this moonlighting protein can be found in various cellular compartments where it has many non-ER functions. To shed more light on the mechanisms underlying polyfunctionality of this moonlighting protein that can be found in different cellular compartments and that possesses a wide spectrum of unrelated biological activities, being able to interact with Ca2+ (and potentially other metal ions), RNA, oligosaccharides, and numerous proteins, we used a set of experimental and computational tools to evaluate the intrinsic disorder status of CALR and the role of calcium binding on structural properties and conformational stability of the full-length CALR and its isolated P- and C-domains.
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Affiliation(s)
- Anna Rita Migliaccio
- a Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai (ISMMS) , New York , NY , USA.,b Department of Biomedical and Neuromotorial Sciences , Alma Mater University , Bologna , Italy
| | - Vladimir N Uversky
- c Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute , Morsani College of Medicine, University of South Florida , Tampa , FL , USA.,d Laboratory of New Methods in Biology , Institute for Biological Instrumentation, Russian Academy of Sciences , Pushchino , Moscow Region 142290 , Russia
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