Lysosomal cysteine proteases localized in lysosomes and endosomes that function to degrade cellular substrates (Turk et al., 2000). Stimulated by TNF and linked to hypertrophic and fibrotic cardiac remodeling (Cheng et al., 2012b). Upregulated in AF (Thomas et al., 2019). This evidence concerns the gene CTSB and atrial fibrillation.