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Maravelez Acosta VA, Crisóstomo Vázquez MDP, Eligio García L, Franco Sandoval LO, Castro Pérez D, Patiño López G, Medina Contreras O, Jiménez Cardoso E. Tumor-Suppressive Cross-Linking of Anti- T. cruzi Antibodies in Acute Lymphoblastic Leukemia. Int J Mol Sci 2024; 25:8307. [PMID: 39125875 PMCID: PMC11313589 DOI: 10.3390/ijms25158307] [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: 06/12/2024] [Revised: 07/16/2024] [Accepted: 07/18/2024] [Indexed: 08/12/2024] Open
Abstract
Parasites have been associated with possible anticancer activity, including Trypanosoma cruzi, which has been linked to inhibiting the growth of solid tumors. To better understand this antitumor effect, we investigated the association of anti-T. cruzi antibodies with B cells of the acute lymphoblastic leukemia (ALL) SUPB15 cell line. The antibodies were generated in rabbits. IgGs were purified by affinity chromatography. Two procedures (flow cytometry (CF) and Western blot(WB)) were employed to recognize anti-T. cruzi antibodies on SUPB15 cells. We also used CF to determine whether the anti-T. cruzi antibodies could suppress SUPB15 cells. The anti-T. cruzi antibodies recognized 35.5% of the surface antigens of SUPB15. The complement-dependent cytotoxicity (CDC) results demonstrate the cross-suppression of anti-T. cruzi antibodies on up to 8.4% of SUPB15 cells. For the WB analysis, a band at 100 kDa with high intensity was sequenced using mass spectrometry, identifying the protein as nucleolin. This protein may play a role in the antitumor effect on T. cruzi. The anti-T. cruzi antibodies represent promising polyclonal antibodies that have the effect of tumor-suppressive cross-linking on cancer cells, which should be further investigated.
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Affiliation(s)
- Víctor Alberto Maravelez Acosta
- Laboratorio de Investigación en Parasitología, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico; (V.A.M.A.); (M.d.P.C.V.); (L.E.G.); (L.O.F.S.); (D.C.P.)
| | - María del Pilar Crisóstomo Vázquez
- Laboratorio de Investigación en Parasitología, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico; (V.A.M.A.); (M.d.P.C.V.); (L.E.G.); (L.O.F.S.); (D.C.P.)
| | - Leticia Eligio García
- Laboratorio de Investigación en Parasitología, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico; (V.A.M.A.); (M.d.P.C.V.); (L.E.G.); (L.O.F.S.); (D.C.P.)
| | - Luz Ofelia Franco Sandoval
- Laboratorio de Investigación en Parasitología, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico; (V.A.M.A.); (M.d.P.C.V.); (L.E.G.); (L.O.F.S.); (D.C.P.)
| | - Denia Castro Pérez
- Laboratorio de Investigación en Parasitología, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico; (V.A.M.A.); (M.d.P.C.V.); (L.E.G.); (L.O.F.S.); (D.C.P.)
| | - Genaro Patiño López
- Unidad de Investigación en Inmunología y Proteomica, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico;
| | - Oscar Medina Contreras
- Unidad de Investigación Epidemiologica en Endocrinologia y Nutricion, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico;
| | - Enedina Jiménez Cardoso
- Laboratorio de Investigación en Parasitología, Hospital Infantil de México Federico Gómez (HIMFG), Dr. Márquez 162. Col Doctores, Cuauhtémoc, México City 06720, Mexico; (V.A.M.A.); (M.d.P.C.V.); (L.E.G.); (L.O.F.S.); (D.C.P.)
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2
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Guan L, Ge R, Ma S. Newsights of endoplasmic reticulum in hypoxia. Biomed Pharmacother 2024; 175:116812. [PMID: 38781866 DOI: 10.1016/j.biopha.2024.116812] [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: 04/15/2024] [Revised: 05/19/2024] [Accepted: 05/20/2024] [Indexed: 05/25/2024] Open
Abstract
The endoplasmic reticulum (ER) is important to cells because of its essential functions, including synthesizing three major nutrients and ion transport. When cellular homeostasis is disrupted, ER quality control (ERQC) system is activated effectively to remove misfolded and unfolded proteins through ER-phagy, ER-related degradation (ERAD), and molecular chaperones. When unfolded protein response (UPR) and ER stress are activated, the cell may be suffering a huge blow, and the most probable consequence is apoptosis. The membrane contact points between the ER and sub-organelles contribute to communication between the organelles. The decrease in oxygen concentration affects the morphology and structure of the ER, thereby affecting its function and further disrupting the stable state of cells, leading to the occurrence of disease. In this study, we describe the functions of ER-, ERQC-, and ER-related membrane contact points and their changes under hypoxia, which will help us further understand ER and treat ER-related diseases.
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Affiliation(s)
- Lu Guan
- Qinghai University, Xining, Qinghai, China
| | - Rili Ge
- Key Laboratory of the Ministry of High Altitude Medicine, Qinghai University, Xining, Qinghai, China; Key Laboratory of Applied Fundamentals of High Altitude Medicine, (Qinghai-Utah Joint Key Laboratory of Plateau Medicine), Qinghai University, Xining, Qinghai, China; Laboratory for High Altitude Medicine of Qinghai Province, Qinghai University, Xining, Qinghai, China
| | - Shuang Ma
- Key Laboratory of the Ministry of High Altitude Medicine, Qinghai University, Xining, Qinghai, China; Key Laboratory of Applied Fundamentals of High Altitude Medicine, (Qinghai-Utah Joint Key Laboratory of Plateau Medicine), Qinghai University, Xining, Qinghai, China; Laboratory for High Altitude Medicine of Qinghai Province, Qinghai University, Xining, Qinghai, China.
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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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Michalak M. Calreticulin: Endoplasmic reticulum Ca 2+ gatekeeper. J Cell Mol Med 2024; 28:e17839. [PMID: 37424156 PMCID: PMC10902585 DOI: 10.1111/jcmm.17839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/21/2023] [Accepted: 06/27/2023] [Indexed: 07/11/2023] Open
Abstract
Endoplasmic reticulum (ER) luminal Ca2+ is vital for the function of the ER and regulates many cellular processes. Calreticulin is a highly conserved, ER-resident Ca2+ binding protein and lectin-like chaperone. Over four decades of studying calreticulin demonstrate that this protein plays a crucial role in maintaining Ca2+ supply under different physiological conditions, in managing access to Ca2+ and how Ca2+ is used depending on the environmental events and in making sure that Ca2+ is not misused. Calreticulin plays a role of ER luminal Ca2+ sensor to manage Ca2+-dependent ER luminal events including maintaining interaction with its partners, Ca2+ handling molecules, substrates and stress sensors. The protein is strategically positioned in the lumen of the ER from where the protein manages access to and distribution of Ca2+ for many cellular Ca2+-signalling events. The importance of calreticulin Ca2+ pool extends beyond the ER and includes influence of cellular processes involved in many aspects of cellular pathophysiology. Abnormal handling of the ER Ca2+ contributes to many pathologies from heart failure to neurodegeneration and metabolic diseases.
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Affiliation(s)
- Marek Michalak
- Department of BiochemistryUniversity of AlbertaEdmontonAlbertaCanada
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Zheng Z, Lu X, Zhou D, Deng XF, Liu QX, Liu XB, Zhang J, Li YQ, Zheng H, Dai JG. A novel enemy of cancer: recent investigations into protozoan anti-tumor properties. Front Cell Infect Microbiol 2024; 13:1325144. [PMID: 38274735 PMCID: PMC10808745 DOI: 10.3389/fcimb.2023.1325144] [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: 11/17/2023] [Accepted: 12/28/2023] [Indexed: 01/27/2024] Open
Abstract
Cancer remains a significant global health issue, despite advances in screening and treatment. While existing tumor treatment protocols such as surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy have proven effective in enhancing the prognosis for some patients, these treatments do not benefit all patients. Consequently, certain types of cancer continue to exhibit a relatively low 5-year survival rate. Therefore, the pursuit of novel tumor intervention strategies may help improve the current effectiveness of tumor treatment. Over the past few decades, numerous species of protozoa and their components have exhibited anti-tumor potential via immune and non-immune mechanisms. This discovery introduces a new research direction for the development of new and effective cancer treatments. Through in vitro experiments and studies involving tumor-bearing mice, the anti-tumor ability of Toxoplasma gondii, Plasmodium, Trypanosoma cruzi, and other protozoa have unveiled diverse mechanisms by which protozoa combat cancer, demonstrating encouraging prospects for their application. In this review, we summarize the anti-tumor ability and anti-tumor mechanisms of various protozoa and explore the potential for their clinical development and application.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Hong Zheng
- Department of Thoracic Surgery, Xinqiao Hospital, Army (Third Military) Medical University, Chongqing, China
| | - Ji-gang Dai
- Department of Thoracic Surgery, Xinqiao Hospital, Army (Third Military) Medical University, Chongqing, China
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Kaufman CD, Farré C, Biscari L, Pérez AR, Alloatti A. Trypanosoma cruzi, Chagas disease and cancer: putting together the pieces of a complex puzzle. Front Cell Dev Biol 2023; 11:1260423. [PMID: 38188016 PMCID: PMC10768204 DOI: 10.3389/fcell.2023.1260423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 11/27/2023] [Indexed: 01/09/2024] Open
Abstract
Considering the extensive and widespread impact on individuals, cancer can presently be categorized as a pandemic. In many instances, the development of tumors has been linked to endemic microbe infections. Among parasitic infections, Trypanosoma cruzi stands out as one of the most extensively discussed protozoans in the literature that explores the association between diseases of parasite origin and cancer. However, the effective association remains an unsolved paradox. Both the parasite, along with protozoan-derived molecules, and the associated antiparasitic immune response can induce alterations in various host cell pathways, leading to modifications in cell cycle, metabolism, glycosylation, DNA mutations, or changes in neuronal signaling. Furthermore, the presence of the parasite can trigger cell death or a senescent phenotype and modulate the immune system, the metastatic cascade, and the formation of new blood vessels. The interaction among the parasite (and its molecules), the host, and cancer undoubtedly encompasses various mechanisms that operate differentially depending on the context. Remarkably, contrary to expectations, the evidence tilts the balance toward inhibiting tumor growth or resisting tumor development. This effect is primarily observed in malignant cells, rather than normal cells, indicating a selective or specific component. Nevertheless, nonspecific bystander mechanisms, such as T. cruzi's adjuvancy or the presence of proinflammatory cytokines, may also play a significant role in this phenomenon. This work aims to elucidate this complex scenario by synthesizing the main findings presented in the literature and by proposing new questions and answers, thereby adding pieces to this challenging puzzle.
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Affiliation(s)
- Cintia Daniela Kaufman
- Instituto de Inmunología Clínica y Experimental de Rosario (IDICER), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Cecilia Farré
- Instituto de Inmunología Clínica y Experimental de Rosario (IDICER), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina
- Centro de Investigación y Producción de Reactivos Biológicos, Facultad de Ciencias Médicas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Lucía Biscari
- Instituto de Inmunología Clínica y Experimental de Rosario (IDICER), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Ana Rosa Pérez
- Instituto de Inmunología Clínica y Experimental de Rosario (IDICER), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina
| | - Andrés Alloatti
- Instituto de Inmunología Clínica y Experimental de Rosario (IDICER), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, Rosario, Argentina
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Ribeiro Franco PI, do Carmo Neto JR, Miguel MP, Machado JR, Nunes Celes MR. Cancer and Trypanosoma cruzi: Tumor induction or protection? Biochimie 2023; 207:113-121. [PMID: 36368477 DOI: 10.1016/j.biochi.2022.10.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 11/09/2022]
Abstract
Trypanosoma cruzi causes Chagas disease, a neglected disease that can be divided, overall, into acute and chronic phases. Understanding the mechanisms underlying its progression is based on the parasite-host interactions occurring during the infection. Although the pathophysiology of the main symptomatic forms of Chagas disease has been the subject of several studies, little is known about their relationship with the development of different types of cancer. Therefore, knowledge regarding the molecular aspects of infection in the host, as well as the influence of the immune response in the parasite and the host, can help to understand the association between Chagas disease and tumor development. This review aims to summarize the main molecular mechanisms related to T. cruzi-dependent carcinogenic development and the mechanisms associated with tumor protection mediated by different parasite components.
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Affiliation(s)
- Pablo Igor Ribeiro Franco
- Department of Bioscience and Technology, Institute of Tropical Pathology and Public Health, Federal University of Goiás, 74605-050, Goiania, Goiás, Brazil.
| | - José Rodrigues do Carmo Neto
- Department of Bioscience and Technology, Institute of Tropical Pathology and Public Health, Federal University of Goiás, 74605-050, Goiania, Goiás, Brazil
| | - Marina Pacheco Miguel
- Department of Bioscience and Technology, Institute of Tropical Pathology and Public Health, Federal University of Goiás, 74605-050, Goiania, Goiás, Brazil; Veterinary and Animal Science School, Federal University of Goiás, 74605-050, Goiania, Goiás, Brazil
| | - Juliana Reis Machado
- Department of General Pathology, Institute of Biological and Natural Sciences, Federal University of Triângulo Mineiro, 38025-180, Uberaba, Minas Gerais, Brazil
| | - Mara Rúbia Nunes Celes
- Department of Bioscience and Technology, Institute of Tropical Pathology and Public Health, Federal University of Goiás, 74605-050, Goiania, Goiás, Brazil
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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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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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