Abstract:
Protease-mediated degradation of proteins is critical in a plethora of physiological processes.
Neutrophils secrete serine proteases including cathepsin G (CatG), neutrophile
elastase (NE), and proteinase 3 (PR3) together with lactoferrin (LF) as a first cellular
immune response against pathogens. Here, we demonstrate that LF increases the catalytic
activity of CatG at physiological concentration, with its highest enhancing capacity under
acidic (pH 5.0) conditions, and broadens the substrate selectivity of CatG. On a functional
level, the enzymatic activity of CatG was increased in the presence of LF in granulocytederived
supernatant. Furthermore, LF enhanced CatG-induced activation of platelets as
determined by cell surface expression of CD62P. Consequently, LF-mediated enhancement
of CatG activity might promote innate immunity during acute inflammation.