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Owen CA, Campbell EJ. Angiotensin II Generation at the Cell Surface of Activated Neutrophils: Novel Cathepsin G-Mediated Catalytic Activity That Is Resistant to Inhibition. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.3.1436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Human neutrophils express inducible, catalytically active cathepsin G on their cell surface. Herein, we report that membrane-bound cathepsin G on intact neutrophils has potent angiotensin II-generating activity. Membrane-bound cathepsin G on activated neutrophils 1) converts both human angiotensin I and angiotensinogen to angiotensin II; 2) expresses angiotensin II-generating activity equivalent to 8.6 ± 2.3 (±SD) × 10−18 mol of free cathepsin G (5.2 ± 1.4 × 106 molecules)/cell; and 3) has similar high affinity for angiotensin I compared with free cathepsin G (Km = 5.9 × 10−4 and 4.6 × 10−4 M; kcat = 4.0 and 2.0/s, respectively). In marked contrast to soluble cathepsin G, membrane-bound enzyme was substantially resistant to inhibition by plasma proteinase inhibitors and converted angiotensin I to angiotensin II even in undiluted plasma. There was a striking inverse relationship between inhibitor size and its effectiveness against membrane-bound cathepsin G activity. α1-Antichymotrypsin was a markedly ineffective inhibitor of membrane-bound enzyme (IC50 = 2.18 μM and 1.38 nM when tested against 1 nM membrane-bound and free cathepsin G, respectively). These data indicate that membrane-bound cathepsin G expressed on neutrophils is an inducible and mobile angiotensin II-generating system that may exert potent local vasoactive and chemoattractant properties at sites of inflammation.
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Affiliation(s)
- Caroline A. Owen
- Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake City, UT 84132
| | - Edward J. Campbell
- Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake City, UT 84132
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