Protein arginine methylation - a posttranslational collagen modification relevant for crosslinking and degradation of collagen in aortic aneurysms?

• Applicant: Privatdozentin Dr. Juliane Hannemann
• Subject Area: Cardiology, Angiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 513189294

Collagen is the most important protein of the connective tissue; it also contributes to the stability of the vascular wall of the arteries. In patients with aneurysms, the metabolism of collagen is disturbed: The cross-linking between individual collagen strands is reduced and the collagen breakdown by matrix metalloproteinases is increased. The molecular mechanisms underlying this process have not yet been fully understood. Abdominal aortic aneurysms are particularly common in patients with Marfan's syndrome, a congenital connective tissue disease; aneurysm rupture is a life-threatening emergency condition. We and others have previously shown that methylated arginines play a role as biomarkers in patients with aortic or cerebral aneurysms. L-arginine residues of proteins are methylated by a specific group of enzymes named protein arginine methyltransferases (PRMTs). The dimethylarginines (ADMA, asymmetrical dimethylarginine; SDMA, symmetrical dimethylarginine) are formed during the hydrolysis of methylated proteins. Our own preliminary data show that collagen 1 is highly post-translationally methylated; after acid hydrolysis of collagen 1, ADMA and SDMA are released. Since consensus sequences for arginine methylation and for crosslinking are in close proximity in the amino acid sequence of collagen 1, we hypothesize that the posttranslational methylation of collagen is a process regulating crosslinking and, thus, collagen turnover. Therefore, the project has the following objectives: We aim to identify the specific PRMT isoform(s) responsible for collagen methylation using cultured human fibroblast cell lines. Furthermore, we will investigate whether pharmacological inhibition or siRNA-mediated knockdown of this PRMT isoform(s) reduces the crosslinking of collagen and increases its degradation by matrix metalloproteinases. In addition, we aim to identify the specific arginine residues at which methylation takes place using mass spectrometry. In two translational approaches, we will quantify the concentrations of collagen turnover markers and dimethylarginines in plasma samples of patients with Marfan's syndrome with and without aortic aneurysm and correlate these data with the clinical data of the patients. In addition, in paired samples of aneurysm tissue and healthy aortic wall obtained intraoperatively from patients with an aortic aneurysm, we will determine the expression of PRMTs, matrix metalloproteinases, and the enzymes responsible for collagen crosslinking using molecular biology techniques. By this, we will strive to identify differences in the regulation of collagen crosslinking and turnover between healthy and diseased vascular walls in humans. The results of the project will contribute to the development of new therapeutic approaches to prevent aneurysm rupture.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Rainer Böger