SK3 channel and mitochondrial ROS mediate NADPH oxidase-independent NETosis induced by calcium influx.
Neutrophils cast neutrophil extracellular traps (NETs) to defend the host against invading pathogens. Although effective against microbial pathogens, a growing body of literature now suggests that NETs have negative impacts on many inflammatory and autoimmune diseases. Identifying mechanisms that regulate the process termed "NETosis" is important for treating these diseases. Although two major types of NETosis have been described to date, mechanisms regulating these forms of cell death are not clearly established. NADPH oxidase 2 (NOX2) generates large amounts of reactive oxygen species (ROS), which is essential for NOX-dependent NETosis. However, major regulators of NOX-independent NETosis are largely unknown. Here we show that calcium activated NOX-independent NETosis is fast and mediated by a calcium-activated small conductance potassium (SK) channel member SK3 and mitochondrial ROS. Although mitochondrial ROS is needed for NOX-independent NETosis, it is not important for NOX-dependent NETosis. We further demonstrate that the activation of the calcium-activated potassium channel is sufficient to induce NOX-independent NETosis. Unlike NOX-dependent NETosis, NOX-independent NETosis is accompanied by a substantially lower level of activation of ERK and moderate level of activation of Akt, whereas the activation of p38 is similar in both pathways. ERK activation is essential for the NOX-dependent pathway, whereas its activation is not essential for the NOX-independent pathway. Despite the differential activation, both NOX-dependent and -independent NETosis require Akt activity. Collectively, this study highlights key differences in these two major NETosis pathways and provides an insight into previously unknown mechanisms for NOX-independent NETosis.
Innate Immunity Research Laboratory, Program in Physiology and Experimental Medicine, SickKids Research Institute and Department of Laboratory Medicine and Pathobiology and.
David Nobuhiro
DN
Douda
Innate Immunity Research Laboratory, Program in Physiology and Experimental Medicine, SickKids Research Institute and.
Meraj A
MA
Khan
Department of Paediatrics, Division of Respiratory Medicine, The Hospital For Sick Children, Toronto, ON, Canada M5G 1X8; and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada M5S 1A8.
Hartmut
H
Grasemann
Innate Immunity Research Laboratory, Program in Physiology and Experimental Medicine, SickKids Research Institute and Department of Laboratory Medicine and Pathobiology and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada M5S 1A8 nades.palaniyar@sickkids.ca.
Nades
N
Palaniyar
D020013:Calcium Signaling / Q000502:physiology*; D016923:Cell Death; D065206:Extracellular Traps / Q000378:metabolism*; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism*; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C406328:KCNN3 protein, human; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D051640:Small-Conductance Calcium-Activated Potassium Channels; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases
NADPH oxidase; NETosis; SK channels; neutrophil extracellular traps; neutrophils