Novel mechanisms of PAD activity regulation. Substrate specificity and activation of peptidyl arginine deiminase in the context of rheumatoid arthritis.
Jagiellonian University in Kraków ·Poland
About this project
<p>Rheumatoid arthritis (RA) is one of the most widespread autoimmune conditions, affecting ~1% of population worldwide. The inflammation of the joints in RA is driven by autoantibodies against citrullinated epitopes (ACPA). Proteins citrullination is a posttranslational modification catalyzed by peptidylarginine deiminases (PAD1, PAD2, PAD3, PAD4 and PAD6) converting positively charged Arg residues to neutral citrulline residues. Although citrullination occurs both in physiological and pathological conditions, ACPA are found exclusively in RA patients and appear in circulation years before clinical onset of the disease. It is accepted that in subjects with specific genetic risk factors immunotolerance breakdown leading to ACPA generation happens on inflamed mucosal surfaces where excessive protein citrullination is carried out by PAD2 or PAD4. However, despite intense research on PADs it is still a mystery how citrullination happens in vivo. PADs activity is calcium-dependent and requires non-physiologically high concentration of Ca2+ (above 5 mM). Up to date, an intense search for PAD cofactors lowering their Ca2+ requirement failed. The groundbreaking character of the project is based on our seminal finding that a group of glycosaminoglycans (GAG), including heparin, heparan sulphate and chondroitin are PAD activators, which lower the Ca2+ requirement of these enzymes to physiological levels, explaining in vivo activity of PADs. The experimental results are fully supported by initial structural docking/modelling studies in silico showing the potential high-affinity heparin binding pockets formed by a cluster of positively charged residues within the PAD2 and PAD4 structure. The aim of the project is to identify and characterize the binding pocket(s) responsible for activation, which will allow targeted design of the novel PAD-specific, allosteric blockers with therapeutic potential, based on previously unidentified activation mechanism.</p>
Bilateral cooperation results
The bilateral cooperation proceeded as planned in the contract, focusing on the implementation of research tasks and the exchange of expertise between the Polish and Norwegian partners. It was based on implementing research tasks and exchanging expertise between Polish and Norwegian partners. Although this collaboration has not yet resulted in joint publications, the project supported 17 researchers, exceeding the planned 7. Of these, 14 were from Poland (5 female, 9 male), and 3 were from Norway (2 female, 1 male), demonstrating active involvement from both sides. Although no new joint project proposals were applied yet, this is due to the proposal calendar. Project is highly prospective, with results indicating potential involvement of other GAG molecules, cartilage proteins and nucleic acids as potential PAD4 activators and these development will be pursued in the future in a collaborative effort. In December 2024, the principal investigator Tomasz Kantyka, PhD submitted a proposal "Characterization of PAD4 enzyme activation by biopolymers from glycosaminoglycan family" (Reg. No: 2023/51/B/NZ1/00958) under the Opus call. This project assumed the collaboration between Jagiellonian University in Krakow, University of Bergen and Wrocław University of Science and Technology, but not in a form of scientific consortium. The next joint proposal "Characterization of nucleic acids as the allosteric activators of PAD4" (Opus call) is in preparation and will be submitted in June 2024.
Project partners
- University of Bergen Donor project partner· Norway
- Wrocław University of Science and Technology Project partner· Poland