Expression and activity of N-myristoyltransferase in lung inflammation of cattle and its role in neutrophil apoptosisAnuraag Shrivastav1, Sarabjeet S. Suri2, Ryan Mohr2, Kyathanahalli S. Janardhan2, Rajendra K. Sharma1 and Baljit Singh2
1 Department of Pathology and Laboratory Medicine, College of Medicine and Saskatchewan Cancer Agency, 20 Campus Drive, Saskatoon, SK S7N 4H4, Canada
2 Department of Veterinary Biomedical Sciences, University of Saskatchewan, Western College of Veterinary Medicine, 52 Campus Drive, Saskatoon, SK S7N 5B4, Canada
Received 20 March 2009; accepted 1 October 2009; published online 2 October 2009
Abstract - N-myristoyltransferase (NMT) attaches a 14 carbon fatty acid, myristic acid, to the N-terminal glycine residue of proteins. NMT exists in two isoforms NMT1 and NMT2. Myristoylated proteins play critical roles in protein–protein interactions, cell signaling and oncogenesis. Although elevated expression of NMT1 has been described in colorectal carcinoma, its expression and roles in normal and inflamed lungs of the cattle are unknown. Therefore, we investigated the expression and activity of NMT in a bovine model of lung inflammation induced with Mannheimia hemolytica and in vitro in neutrophils and macrophages. Western blots revealed increased expression of NMT1 in lungs from infected animals compared to control animals. Total NMT activity was reduced in inflamed lungs compared to control animals (p < 0.05) along with increased expression of enolase, a putative inhibitor of NMT. NMT1 staining was observed in the septum, vascular endothelium and the epithelium in the lungs from control as well as infected calves. NMT1 expression was intense in neutrophils in the necrotic areas in the inflamed lungs. Immuno-electron microscopy localized NMT1 in cytoplasm and nuclei of endothelium, pulmonary intravascular macrophages and airway epithelium. Total NMT activity and NMT1 expression were increased in neutrophils and macrophages exposed to Escherichia coli LPS in vitro. NMT knockdown increased apoptosis in activated neutrophils. This is the first report demonstrating expression of NMT in normal and inflamed lungs and a novel role for NMT in regulation of neutrophil lifespan.
Key words: NMT / neutrophil / macrophage / apoptosis / RNA knockdown
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© INRA, EDP Sciences 2009