PR3s

PR3s commonly refers to proteinase 3, a serine protease of the neutrophil azurophil granules. The plural form may denote multiple molecules, isoforms, or related enzymes within this family. Proteinase 3 is encoded by the PRTN3 gene in humans and belongs to the chymotrypsin-like serine protease subfamily.

Proteinase 3 is stored in azurophilic granules of neutrophils and released during degranulation. It is activated from its zymogen form and functions as a protease with broad substrate specificity. Its substrates include a range of host proteins, including components of the extracellular matrix and antimicrobial peptides, contributing to antimicrobial defense and tissue remodeling. PR3 can also process cytokines and chemokines, thus influencing inflammatory signaling. In the circulation or at sites of inflammation, PR3 activity is regulated by endogenous inhibitors such as alpha-1 antitrypsin.

In medicine, PR3 is best known as an autoantigen targeted by anti-neutrophil cytoplasmic antibodies (PR3-ANCA). PR3-ANCA is strongly associated with granulomatosis with polyangiitis (formerly Wegener’s granulomatosis) and is used in diagnostic testing and disease monitoring in some cases. Elevated or dysregulated PR3 activity has been studied in inflammatory states and certain infections, though its precise role can vary by context.

Beyond clinical use, PR3s are subjects of ongoing research into neutrophil biology, inflammation, and potential therapeutic targeting. The term PR3s may also be used in broader discussions to refer to related serine proteases in the same family or to multiple PR3 molecules observed in a given sample.