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Projects / Programmes source: ARIS

Role of legumain in infection and inflammation

Research activity

Code Science Field Subfield
3.01.00  Medical sciences  Microbiology and immunology   

Code Science Field
B000  Biomedical sciences   

Code Science Field
3.01  Medical and Health Sciences  Basic medicine 
Keywords
legumain, infection, immunology, proteomics, proteolysis, substrates, peroxidase
Evaluation (rules)
source: COBISS
Researchers (7)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  18801  PhD Marko Fonović  Biochemistry and molecular biology  Head  2018 - 2022  189 
2.  29544  PhD Ajda Taler Verčič  Biochemistry and molecular biology  Researcher  2018 - 2019  80 
3.  07561  PhD Boris Turk  Biochemistry and molecular biology  Researcher  2018 - 2022  1,038 
4.  26515  PhD Aleksandra Usenik  Biochemistry and molecular biology  Researcher  2019 - 2022  56 
5.  21619  PhD Olga Vasiljeva  Oncology  Researcher  2018 - 2022  183 
6.  33762  PhD Robert Vidmar  Biochemistry and molecular biology  Researcher  2018 - 2022  149 
7.  32171  PhD Matej Vizovišek  Biochemistry and molecular biology  Researcher  2018  143 
Organisations (2)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  91,971 
2.  2990  Center of excellence for integrated approaches in chemistry and biology of proteins, Ljubljana  Ljubljana  3663388  731 
Abstract
Legumain or asparaginyl endopeptidase (AEP) is a member of the CD clan of cysteine proteases and cleaves protein substrates exclusively after asparagine or (to a minor extent) aspartic acid residues. It is a highly conserved protein which is present in a large variety of animal species. It was shown that legumain has possible roles in normal lysosomal functions, antigen presentation, immune response and immune signalling, but also in apoptosis and osteoclast remodelling. The most reliable experimental evidence for major physiological roles of legumain was obtained from animal models, where legumain null mice exhibited hemophagocytic syndrome, impaired kidney function and accumulation of macromolecules in the lysosomes which is characteristic for lysosomal storage diseases. Recently, several reports linked legumain to various pathological conditions such as cancer and Alzheimer’s disease. However, one of the most important physiological roles of mammalian legumain is in the immune response, where it was originally thought to participate solely in the processing of foreign proteins for presentation on the MHCII complex. In the last decade it was also shown to activate TLR receptors of the innate immune system and influence signalling pathways through the processing of other membrane receptors. Contrary to many other proteases, physiological substrates of legumain were never studied on a system wide level and all known substrates were identified on a case-by-case basis. Although legumain is emerging as physiologically and clinically relevant target, due to the lack of experimental data on its substrates the majority of legumain physiological functions, especially the ones related to immune response, still remain largely unknown. This emphasizes the need to address its physiological functions by identification of its substrates, which has the potential for a major scientific breakthrough and could therefore significantly improve our understanding of legumain-dependent mechanisms behind immunity. We recently performed a pilot proteomic analysis of macrophages from legumain null mice and our preliminary results showed that legumain ablation in macrophages caused extremely high upregulation of two peroxidases related to the antimicrobial immune response (myeloperoxidase and eosinophil peroxidase). Both peroxidases are known to produce hypochlorous acid which is a potent antimicrobial agent involved in elimination of infectous organisms. However, hypohalous acids were also reported to damage the host tissue during the inflammatory conditions such as asthma and hypereosinophilic syndrome which means that legumain could be directly involved in regulation of those processes, but the molecular mechanisms remain unknown. The data obtained in our preliminary experiments demonstrated that the proposed research can provide an explanation of legumain-null phenotype at the molecular level. Moreover, this project enables a novel and unique insight into the role of legumain in immune response and inflammation, as well as on the regulation of immune response and inflammation in general. In this proposal, we plan to expand our research by performing a systematic proteomic analysis of several tissue types of young and aged mice in order to obtain a detailed understanding of how legumain regulates physiological processes at the molecular level. The obtained results will be supplemented with quantitative PCR and antibody array data and will be used for biochemical and biological validations of the identified molecular processes and pathways. Finally, the in vivo role of legumain in defense against pathogen infection will be examined in animal models. Legumain dependant effect on antimicrobial action of immune cells through the generation of hypochlorous acid could open new venues for development of therapeutic approaches to fight infection.
Significance for science
The immune system protects the organism from the harmful influence of the environment and is essential for its survival. It is composed of a large variety of organs, cells and proteins and is the second most complex system in the human body (right after the nervous system). Disorders of the immune system do not only compromise the ability to fight off infections but can also cause severe health issues such as allergies, autoimmune disorders, inflammatory diseases and cancer. Proposed research project is based on our preliminary data which revealed a novel and unique connection between cysteine protease legumain and severe upregulation of peroxidases related to immune response. Furthermore, we also discovered processing of putative regulatory proteins through which legumain could trigger the immune response and subsequent inflammation. Work proposed in this project could therefore answer two important basic questions. First, it would systematically reveal physiological substrates of legumain which would provide unpresedented insight into its physiological functions. Legumain structure and its unique proteolytic specificity has remained higly conserved during the last 1000 million years which means that we can obtain a physiological insight into one of the crucial mammalian proteases. The second basic scientific question this project aims to answer is related to the general regulation of immune response, where we will investigate how legumain upregulates proteins involved in inflammation and immune and pathogen killing. This part of the project could reveal a completely novel physiological pathway which would represent a major scientific breakthrough. Beside answering both basic scientific questions, proposed research could also have very practical implications since observed legumain triggered boost of peroxidase activity might be applied in clinical setting to increase immune resistance and clearance efficiency of pathogen infection. We are convinced that results of the proposed research project will have a significant impact in the field of immunology and biochemical sciences. As such, they will be noted also in international research conferences and high impact publications which will strenghten the international visibility and position of Slovenian science.
Significance for the country
The immune system protects the organism from the harmful influence of the environment and is essential for its survival. It is composed of a large variety of organs, cells and proteins and is the second most complex system in the human body (right after the nervous system). Disorders of the immune system do not only compromise the ability to fight off infections but can also cause severe health issues such as allergies, autoimmune disorders, inflammatory diseases and cancer. Proposed research project is based on our preliminary data which revealed a novel and unique connection between cysteine protease legumain and severe upregulation of peroxidases related to immune response. Furthermore, we also discovered processing of putative regulatory proteins through which legumain could trigger the immune response and subsequent inflammation. Work proposed in this project could therefore answer two important basic questions. First, it would systematically reveal physiological substrates of legumain which would provide unpresedented insight into its physiological functions. Legumain structure and its unique proteolytic specificity has remained higly conserved during the last 1000 million years which means that we can obtain a physiological insight into one of the crucial mammalian proteases. The second basic scientific question this project aims to answer is related to the general regulation of immune response, where we will investigate how legumain upregulates proteins involved in inflammation and immune and pathogen killing. This part of the project could reveal a completely novel physiological pathway which would represent a major scientific breakthrough. Beside answering both basic scientific questions, proposed research could also have very practical implications since observed legumain triggered boost of peroxidase activity might be applied in clinical setting to increase immune resistance and clearance efficiency of pathogen infection. We are convinced that results of the proposed research project will have a significant impact in the field of immunology and biochemical sciences. As such, they will be noted also in international research conferences and high impact publications which will strenghten the international visibility and position of Slovenian science.
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