Activation of the epidermal growth factor receptor (EGFR) by a novel metalloprotease pathway.
Neutrophil Elastase (NE) is a pro-inflammatory protease present at higher than normal levels in the lung during inflammatory disease. NE regulates IL-8 production from airway epithelial cells and can activate both EGFR and TLR4. TACE/ADAM17 has been reported to trans-activate EGFR in response to NE. Here, using 16HBE14o-human bronchial epithelial cells we demonstrate a new mechanism by which NE regulates both of these events. A high molecular weight soluble metalloprotease activity detectable only in supernatants from NE-treated cells by gelatin and casein zymography was confirmed to be meprin alpha by Western immunoblotting. In vitro studies demonstrated the ability of NE to activate meprin alpha, which in turn could release soluble TGFalpha and induce IL-8 production from 16HBE14o- cells. These effects were abrogated by actinonin, a specific meprin inhibitor. NE-induced IL-8 expression was also inhibited by meprin alpha siRNA. Immunoprecipitation studies detected EGFR/TLR4 complexes in NE-stimulated cells overexpressing these receptors. Confocal studies confirmed colocalization of EGFR and TLR4 in 16HBE14o- cells stimulated with meprin alpha. NFkappaB was also activated via MyD88 in these cells by meprin alpha. In bronchoalveolar lavage fluid from NE knock-out mice infected intra-tracheally with Pseudomonas aeruginosa meprin alpha was significantly decreased compared with control mice, and was significantly increased and correlated with NE activity, in bronchoalveolar lavage fluid from individuals with cystic fibrosis but not healthy controls. The data describe a previously unidentified lung metalloprotease meprin alpha, and its role in NE-induced EGFR and TLR4 activation and IL-8 production.
Bergin
David A
DA
Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.
Greene
Catherine M
CM
Sterchi
Erwin E
EE
Kenna
Cliona
C
Geraghty
Patrick
P
Belaaouaj
Abderrazzaq
A
Belaaouaj
Abderazzaq
A
Taggart
Clifford C
CC
O'Neill
Shane J
SJ
McElvaney
Noel G
NG
D001980:Bronchi / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid; D002460:Cell Line; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis; D019272:Leukocyte Elastase / Q000378:metabolism; D045726:Metalloproteases / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D008625:Tiopronin / Q000378:metabolism; D016211:Transforming Growth Factor alpha / Q000378:metabolism
D016209:Interleukin-8; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D008625:Tiopronin; D066246:ErbB Receptors; D045726:Metalloproteases; D019272:Leukocyte Elastase