title: The epidermal growth factor receptor mediates tumor necrosis factor-alpha-induced activation of the ERK/GEF-H1/RhoA pathway in tubular epithelium.
abstract: Tumor necrosis factor (TNF)-α induces cytoskeleton and intercellular junction remodeling in tubular epithelial cells; the underlying mechanisms, however, are incompletely explored. We have previously shown that ERK-mediated stimulation of the RhoA GDP/GTP exchange factor GEF-H1/Lfc is critical for TNF-α-induced RhoA stimulation. Here we investigated the upstream mechanisms of ERK/GEF-H1 activation. Surprisingly, TNF-α-induced ERK and RhoA stimulation in tubular cells were prevented by epidermal growth factor receptor (EGFR) inhibition or silencing. TNF-α also enhanced phosphorylation of the EGFR. EGF treatment mimicked the effects of TNF-α, as it elicited potent, ERK-dependent GEF-H1 and RhoA activation. Moreover, EGF-induced RhoA activation was prevented by GEF-H1 silencing, indicating that GEF-H1 is a key downstream effector of the EGFR. The TNF-α-elicited EGFR, ERK, and RhoA stimulation were mediated by the TNF-α convertase enzyme (TACE) that can release EGFR ligands. Further, EGFR transactivation also required the tyrosine kinase Src, as Src inhibition prevented TNF-α-induced activation of the EGFR/ERK/GEF-H1/RhoA pathway. Importantly, a bromodeoxyuridine (BrdU) incorporation assay and electric cell substrate impedance-sensing (ECIS) measurements revealed that TNF-α stimulated cell growth in an EGFR-dependent manner. In contrast, TNF-α-induced NFκB activation was not prevented by EGFR or Src inhibition, suggesting that TNF-α exerts both EGFR-dependent and -independent effects. In summary, in the present study we show that the TNF-α-induced activation of the ERK/GEF-H1/RhoA pathway in tubular cells is mediated through Src- and TACE-dependent EGFR activation. Such a mechanism could couple inflammatory and proliferative stimuli and, thus, may play a key role in the regulation of wound healing and fibrogenesis.
authors.affiliation: Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Department of Surgery, University of Toronto, Toronto, Ontario M5B 1W8, Canada.
authors.forename: Eli
authors.initials: E
authors.lastname: Kakiashvili
authors.forename: Qinghong
authors.initials: Q
authors.lastname: Dan
authors.forename: Matthew
authors.initials: M
authors.lastname: Vandermeer
authors.forename: Yuqian
authors.initials: Y
authors.lastname: Zhang
authors.forename: Faiza
authors.initials: F
authors.lastname: Waheed
authors.forename: Monica
authors.initials: M
authors.lastname: Pham
authors.forename: Katalin
authors.initials: K
authors.lastname: Szászi
mesh_terms: D000818:Animals; D002460:Cell Line; D004285:Dogs; D004789:Enzyme Activation / Q000502:physiology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D010766:Phosphorylation / Q000502:physiology; D064067:Rho Guanine Nucleotide Exchange Factors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D019459:Urothelium / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C577356:ARHGEF2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; D014409:Tumor Necrosis Factor-alpha; C066737:RHOA protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D020742:rhoA GTP-Binding Protein