Cathepsin A (CTSA), also known as lysosomal protective protein or carboxypeptidase A, is a multifunctional serine protease belonging to the peptidase S10 family. It plays a critical role in lysosomal protein degradation by stabilizing and activating two key lysosomal enzymes: β-galactosidase (GLB1) and neuraminidase-1 (NEU1). CTSA forms a protective multienzyme complex with these proteins, preventing their premature degradation and ensuring proper lysosomal function. Dysregulation of CTSA is linked to lysosomal storage disorders, particularly galactosialidosis, an inherited condition caused by CTSA gene mutations that lead to systemic accumulation of undegraded substrates.
CTSA also participates in extracellular processes, including peptide hormone processing, blood pressure regulation via inactivation of bradykinin, and extracellular matrix remodeling. Its dual intra- and extracellular roles connect it to various pathologies beyond lysosomal disorders, including cancer metastasis, cardiovascular diseases, and neurodegeneration.
CTSA antibodies are essential tools for studying its expression, localization, and function in both physiological and pathological contexts. They enable detection in tissue samples, cell lysates, and biological fluids through techniques like Western blot, immunohistochemistry, and ELISA. Therapeutic interest in CTSA inhibitors has emerged, particularly for cancer treatment, given its role in tumor invasion and angiogenesis. Research continues to explore CTSA's complex biology and its potential as a diagnostic marker or therapeutic target.