Src-dependent ERK5 and Src/EGFR-dependent ERK1/2 activation is required for cell proliferation by asbestos

Our plain-English summary of Src-dependent ERK5 and Src/EGFR-dependent ERK1/2 activation is required for cell proliferation by asbestos, by L. Scapoli, M.E. Ramos-Nino, M. Martinelli, et al (Oncogene, 2004).

The study

• Authors: L. Scapoli, M.E. Ramos-Nino, M. Martinelli, B.T. Mossman
• Journal: Oncogene
• Published: 2004;23(3):805-13
• Cited by: 69 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Crocidolite asbestos elicits oxidative stress and cell proliferation, but the signaling cascades linked to these outcomes are unclear. To determine the role of mitogen-activated protein kinases (MAPK) in asbestos-induced cell signaling, we evaluated the effects of crocidolite asbestos, EGF and H2O2, on MAPK activation in murine lung epithelial cells (C10 line). In contrast to rapid and transient activation of extracellular signal-regulated kinase 5 (ERK5) by EGF or H2O2, asbestos caused protracted oxidant-dependent ERK5 activation that was inhibited by an Src kinase inhibitor (PP2), but not by an inhibitor of epidermal growth factor receptor (EGFR) phosphorylation (AG1478). ERK1/2 activation by asbestos was inhibited by either PP2 or AG1478. To confirm the involvement of Src in ERK1/2 and ERK5 activation, a dominant-negative Src construct was used. These experiments showed that Src was essential for ERK1/2 and also ERK5 phosphorylation by asbestos. Time frame studies indicated immediate activation of Src by asbestos fibers, whereas EGFR phosphorylation occurred subsequently. Data suggest that asbestos causes activation of ERK5 through an EGFR-independent pathway, whereas ERK1/2 activation is dependent on Src through a mechanism involving phosphorylation of the EGFR. Furthermore, Src, ERK1/2 and ERK5 activation are essential for cell proliferation by asbestos. The use of a dominant-negative ERK5 construct caused selective downregulation of c-jun expression, whereas inhibition of Src by PP2 or MEK1 by PD98059 caused decreases in c-fos, fra-1 and c-jun expression in asbestos-exposed C10 cells. These observations may have broad relevance to cell proliferation by carcinogenic mineral fibers and oxidants.

In plain English

This laboratory study used a mouse lung cell line (C10 alveolar epithelial type II cells) grown in dishes, not people. The authors exposed the cells to crocidolite asbestos and compared its effects with epidermal growth factor (EGF) and hydrogen peroxide on signaling enzymes called ERK5 and ERK1/2. EGF and hydrogen peroxide switched ERK5 on quickly, and it was back to control levels by 1 hour. Asbestos switched it on later, and it was still increasing at 24 hours. Glass beads and the non-fibrous mineral riebeckite did not do this, and catalase blocked the asbestos effect. Blocking the enzyme Src prevented ERK5 activation by asbestos. Blocking the EGF receptor did not, although it did block asbestos-induced ERK1/2 activation. Src was activated within 1 minute of asbestos exposure, the EGF receptor only after 2 hours. Blocking Src, the ERK1/2 pathway or ERK5 reduced the number of cells copying their DNA, a sign of cell division. The authors concluded that the ERK1/2 and ERK5 pathways are both important in asbestos-induced proliferation and that proliferation is also Src-dependent.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory cell-culture (in vitro) experiments
• Who was studied: A non-transformed mouse lung epithelial cell line (C10 alveolar epithelial type II cells); no human or animal subjects
• Exposure: Crocidolite asbestos (NIEHS reference sample) at 5 micrograms per square centimetre of dish. It was compared with EGF at 5 ng/ml and with hydrogen peroxide. Glass beads and riebeckite particles served as control particles.
• Main results:
  • In C10 cells, EGF or hydrogen peroxide raised ERK5 activation immediately. It peaked around 20 minutes and returned to control levels at 1 hour.
  • In asbestos-exposed C10 cells, ERK5 activation came later and lasted longer; it was still increasing at 24 hours.
  • ERK5 activation by asbestos was dose-related and was inhibited when catalase was added.
  • Asbestos fibers induced ERK5 activation; glass beads and the non-fibrous analog riebeckite did not.
  • The Src inhibitor PP2 inhibited ERK5 activation by asbestos at 8 and 24 hours.
  • The EGF receptor inhibitor AG1478 and the MEK1 inhibitor PD98059 did not block ERK5 activation by asbestos.
  • Asbestos increased ERK5 activation in control (empty vector) cells but not in cells carrying a dominant-negative Src construct.
  • Inhibitors of EGF receptor and MEK1/2 phosphorylation blocked asbestos-induced ERK1/2 activation.
  • Transfection with the dominant-negative Src construct inhibited ERK1/2 activation.
  • Src activation by asbestos started at 1 minute and peaked at 30 minutes to 1 hour. EGF receptor phosphorylation was not apparent until 2 hours.
  • EGF and hydrogen peroxide phosphorylated the EGF receptor at the Tyr 1173 site, but asbestos did not.
  • Blocking Src or MEK1 with inhibitors, or using a dominant-negative ERK5 construct, reduced the number of asbestos-exposed cells incorporating BrdU (replicating cells).
  • Inhibiting Src or MEK1 decreased asbestos-induced mRNA levels of fra-1, c-fos and c-jun.
  • The dominant-negative ERK5 construct reduced only c-jun mRNA.
• The authors' conclusion: The authors concluded that the ERK1/2 and ERK5 pathways are both important in asbestos-induced proliferation of these cells, and that this proliferation is also Src-dependent.
• Limitations the authors state:
  • The authors state that how asbestos causes EGF receptor phosphorylation is complex and was beyond the scope of the report.
  • The authors describe asbestos's unusual effects on EGF receptor phosphorylation as a subject for future investigation.

Topics

Medical terms in this study, explained in our Lexicon: EGFR, Crocidolite, Oxidative Stress, Carcinogenic, Mineral Fiber.

Related studies

• EGFR-dependent signalling reduced and p38 dependent apoptosis required by Gallic acid in Malignant Mesothelioma cells — A. Demiroglu-Zergeroglu, G. Candemir, et al. (2016)
• Mechanisms of silica-induced IL-8 release from A549 cells: initial kinase-activation does not require EGFR activation or particle uptake — J. Øvrevik, M. Refsnes, et al. (2006)
• The duration of nuclear extracellular signal-regulated kinase 1 and 2 signaling during cell cycle reentry distinguishes proliferation from apoptosis in response to asbestos — Z. Yuan, D.J. Taatjes, et al. (2004)
• Activation of p38 MAP kinase by asbestos in rat mesothelial cells is mediated by oxidative stress — W.A. Swain, K.J. O'Byrne, et al. (2004)
• Combined inhibition of MET and EGFR suppresses proliferation of malignant mesothelioma cells — K. Kawaguchi, H. Murakami, et al. (2009)
• Gefitinib targets EGFR dimerization and ERK1/2 phosphorylation to inhibit pleural mesothelioma cell proliferation — R.E. Favoni, A. Pattarozzi, et al. (2010)

Browse more research in Oncogene, or return to medical research.