title: STAT3 attenuates EGFR-mediated ERK activation and cell survival during oxidant stress in mouse proximal tubular cells.
abstract: We have shown that renal epithelial cell survival depends on the sustained activation of the extracellular signal-regulated protein kinase (ERK) and lack of this activation was associated with death during oxidative stress. ERK is activated via the canonical epidermal growth factor receptor (EGFR)-Ras-MEK pathway, which could be attenuated by oxidants. We now show that the failure to activate ERK in a sustained manner during severe oxidative stress is owing to the activation of the signal transducer and activator of transcription-3 (STAT3) rather than the failure to activate the EGFR. Tyrosine phosphorylation of the EGFR and STAT3 was studied in hydrogen peroxide (H(2)O(2))-treated mouse proximal tubule (TKPTS) cells or in mouse kidney after ischemia/reperfusion (I/R) injury by Western blotting. STAT3 activation was inhibited by either pharmacologically (AG490) through its upstream janus kinase (JAK2) or by a dominant-negative STAT3 adenovirus. EGFR was inhibited by AG1478. Survival was determined by fluorescence-activated cell sorter analysis and trypan blue exclusion. We found that the EGFR was phosphorylated on its major autophosphorylation site (Tyr1173) regardless of the H(2)O(2) dose. On the other hand, both I/R and severe oxidative stress - but not moderate stress - increased tyrosine phosphorylation of STAT3 in an EGFR and JAK2-dependent manner. Inhibition of JAK2 or STAT3 lead to increased ERK activation and survival of TKPTS cells during severe oxidative stress. Our data suggest a role of tyrosine-phosphorylated STAT3 in the suppression of ERK activation. These data suggest that the STAT3 pathway might represent a new target for improved survival of proximal tubule cells exposed to severe oxidant injury.
authors.affiliation: Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA. iarany@uams.edu
authors.forename: I
authors.initials: I
authors.lastname: Arany
authors.forename: J K
authors.initials: JK
authors.lastname: Megyesi
authors.forename: B D
authors.initials: BD
authors.lastname: Nelkin
authors.forename: R L
authors.initials: RL
authors.lastname: Safirstein
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D053614:Janus Kinase 2; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018384:Oxidative Stress / Q000502:physiology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D011799:Quinazolines; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D011799:Quinazolines; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; C101044:RTKI cpd; D014443:Tyrosine; D006861:Hydrogen Peroxide; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases