Cathepsin L (E3R3P) Rabbit mAb #55914

Cathepsin L belongs to the C1 family of peptidases, a large and diverse family of cysteine (thiol) proteases that play fundamental roles in protein processing and degradation. The catalytic activity of C1 peptidases maps to a nucleophilic cysteine thiol, usually found within a catalytic dyad or triad (1). Cathepsin L, initially synthesized as procathepsin L before undergoing proteolytic cleavage to its active form, is a ubiquitously expressed thiol protease, expressed primarily in lysosomes but which is also secreted by some cell types. Its diverse functions include general protein catabolism and autophagy (2), antigen processing (3), promoting angiogenesis (4), and extracellular matrix degradation (5,6). An isoform of cathepsin L has also been reported in the nucleus, where it was shown to be involved in the regulation of transcription factor activity (7). Targeted deletion of the Ctsl gene in mice embryos was non-lethal, but resulted in periodic hair loss and skin defects, including epidermal hyperplasia, acanthosis, and hyperkeratosis (8). More recently, research studies have reported that cathepsin L is involved in viral protein processing during viral replication, and that cathepsin L inhibitors may have utility in combating infection by SARS-CoV-2 and related coronaviruses (9).