Tolloid Protease-Mediated Regulation of GDF11 in the Pathogenesis of Atrial Fibrosis

Project Summary: Atrial fibrillation (AF) is the most common cardiac arrhythmia, significantly increasing the risk of myocardial infarction, stroke, and heart failure. Despite its widespread impact, the mechanisms underlying AF remain incompletely understood. A key driver of AF is atrial fibrosis, which alters the heart’s structure and disrupts electrical signaling, creating a substrate for arrhythmia initiation and progression. Effective prevention and management of AF, therefore, requires targeted strategies to address fibrosis. Growth differentiation factor 11 (GDF11), a TGF-β superfamily member, has shown anti-fibrotic properties in the heart, distinguishing it as a promising therapeutic target. Although GDF11 shares ~90% sequence homology with its counterpart GDF8, their biochemical functions are distinct. Recent work from our lab has established methods to reliably differentiate these ligands and highlighted their unique roles in cardiac health. While circulating levels of GDF11 and GDF8 measured by mass spectrometry show no correlation with cardiovascular disease, aptamer- based dual detection of GDF11/8 cleaved mature domains has robustly predicted AF in at-risk patients. The activation of GDF11 requires cleavage of its inhibitory prodomain by Tolloid (TLD) proteases, a critical step in enhancing its biological activity. Notably, unpublished single-nuclei data from our lab reveals reduced TLD transcript expression in the left atrial appendages of AF patients. Moreover, exogenous administration of TLD- cleaved GDF11 significantly reduces cardiac fibrosis in preclinical models, underscoring TLD protease activity as a vital mechanism in atrial fibrosis and AF pathogenesis. This proposal aims to investigate the role of TLD proteases in experimental atrial fibrosis through the use of gene-edited mouse models, both with and without surgically induced atrial fibrosis. Additionally, the study will explore the therapeutic potential of exogenous, prodomain-cleaved GDF11. By elucidating the molecular mechanisms linking TLD proteases and atrial fibrosis, this research seeks to advance our understanding of AF pathogenesis and identify novel therapeutic approaches for its treatment.