Protein-A activates membrane bound multicomponent enzyme complex, NADPH oxidase in human neutrophils.
Protein-A, 42KD cell wall glycoprotein of S. aureus Cowan I enhance mononuclear and polymorphonuclear cell counts in vivo and possesses antitoxic, antitumor, properties. In order to explain the mechanism of its function, the respiratory burst phenomenon in cell and cell free system was studied using lucigenin-dependent chemiluminescence technique. A dose dependent increase in protein A-mediated generation of superoxide radical was observed in resting and PMA stimulated neutrophils. Superoxide dismutase (SOD) was used to confirm the production of superoxide radicals (O2-). To understand the mechanism of protein-A induced O2- generation; NADPH oxidase activity was measured in cell free system using NADPH as a substrate. A significant increase in NADPH oxidase activity was observed in the membrane and post-nuclear supernatant fraction of activated human neutrophils. Cytosolic fraction showed slight enzyme activation. Protein A (SpA)-induced NADPH oxidase activation in the membrane fraction was observed even in the absence of the substrate NADPH. These data indicate that protein A attenuate the NADPH oxidase system to produce O2- radicals.
Mishra
A
A
Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
Dwivedi
P D
PD
Verma
A S
AS
Ray
P K
PK
D000166:Acridines; D002462:Cell Membrane / Q000201:enzymology; D002469:Cell Separation; D002474:Cell-Free System; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008163:Luminescent Measurements; D019255:NADPH Oxidases / Q000378:metabolism*; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D016897:Respiratory Burst / Q000187:drug effects; D013205:Staphylococcal Protein A / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism
D000166:Acridines; D013205:Staphylococcal Protein A; D013481:Superoxides; C033472:10,10'-dimethyl-9,9'-biacridinium; D019255:NADPH Oxidases