Measuring elastase, proteinase 3 and cathepsin G activities at the surface of human neutrophils with fluorescence resonance energy transfer substrates.
The neutrophil serine proteases (NSPs) elastase, proteinase 3 and cathepsin G are multifunctional proteases involved in pathogen destruction and the modulation of inflammatory processes. A fraction of secreted NSPs remains bound to the external plasma membrane, where they remain enzymatically active. This protocol describes the spectrofluorometric measurement of NSP activities on neutrophil surfaces using highly sensitive Abz-peptidyl-EDDnp fluorescence resonance energy transfer (FRET) substrates that fully discriminate between the three human NSPs. We describe FRET substrate synthesis, neutrophil purification and handling, and kinetic experiments on quiescent and activated cells. These are used to measure subnanomolar concentrations of membrane-bound or free NSPs in low-binding microplates and to quantify the activities of individual proteases in biological fluids like expectorations and bronchoalveolar lavages. The whole procedure, including neutrophil purification and kinetic measurements, can be done in 4-5 h and should not be longer because of the lifetime of neutrophils. Using this protocol will help identify the contributions of individual NSPs to the development of inflammatory diseases and may reveal these proteases to be targets for therapeutic inhibitors.
Korkmaz
Brice
B
Department of Neuroimmunology, Max-Planck Institute of Neurobiology, Planegg-Martinsried D-82152, Germany.
Attucci
Sylvie
S
Juliano
Maria Aparecida
MA
Kalupov
Timofey
T
Jourdan
Marie-Lise
ML
Juliano
Luiz
L
Gauthier
Francis
F
D056649:Cathepsin G; D002403:Cathepsins / Q000097:blood* / Q000378:metabolism; D002469:Cell Separation; D005434:Flow Cytometry; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D005456:Fluorescent Dyes; D006801:Humans; D007700:Kinetics; D053146:Myeloblastin / Q000097:blood* / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology*; D010196:Pancreatic Elastase / Q000097:blood* / Q000378:metabolism; D012697:Serine Endopeptidases / Q000097:blood* / Q000378:metabolism; D013379:Substrate Specificity
D005456:Fluorescent Dyes; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D010196:Pancreatic Elastase; D053146:Myeloblastin