Dopamine activates ERKs in alveolar epithelial cells via Ras-PKC-dependent and Grb2/Sos-independent mechanisms

Abstract

Recently it has been described that dopamine (DA), via dopaminergic type 2 receptors (D2R), activates the mitogen-activated protein kinase extracellular signal-regulated kinase (MAPK/ERK) proteins in alveolar epithelial cells (AEC), which results in the upregulation of Na+-K+-ATPase. In the present report, we used AEC to investigate the signaling pathway that links DA with ERK activation. Incubation of AEC with DA resulted in rapid and transient stimulation of ERK activity, which was mediated by Ras proteins and the serine/threonine kinase Raf-1. Pretreatment of AEC with Src homology 3 binding peptide, which blocks the interaction between Grb2 and Sos, did not prevent DA activation of ERK. Diacylglycerol (DAG)-dependent protein kinase C (PKC) isoenzymes, involved in the DA-mediated activation of ERK proteins as pretreatment with either bisindolylmaleimide or Ro-31-8220, prevented the phosphorylation of Elk-1, and quinpirole, a D2R activator, stimulates the translocation of PKCε. Together, the data suggest that DA activated MAPK/ERK via Ras, Raf-1 kinase, and DAG-dependent PKC isoenzymes, but, importantly and contrary to the classical model, this pathway did not involve the Grb2-Sos complex formation.

Modulation of Na+transport and epithelial sodium channel expression by protein kinase C in rat alveolar epithelial cells

“…Although this finding might be surprising, since PKC has been shown to modulate Na + -K + -ATPase activity in alveolar type II cells, it is not totally unexpected as most of these studies have evaluated the impact of short-term PKC activation on Na + -K + -ATPase activity and membrane translocation Guerrero et al 2002), whereas we are looking at the impact more than 24 h after the beginning of PMA treatment. Furthermore, the effect of PKC activation on Na + -K + -ATPase can lead to either stimulation or inhibition of its activity.…”

“…Transepithelial Na + transport is also highly dependent on Na + -K + -ATPase activity , and PKC is well known to phosphorylate (Bertorello et al 1991;Kazanietz et al 2001) and modify Na + -K + -ATPase activity (Vasilets et al 1990;Liang and Knox 1999;Ridge et al 2002;Guerrero et al 2002). We decided to also investigate the potential role of Na + -K + -ATPase inhibition in the decrease of I te .…”

Keratin 8 Phosphorylation by Protein Kinase C δ Regulates Shear Stress-mediated Disassembly of Keratin Intermediate Filaments in Alveolar Epithelial Cells

“…Twenty to 50 g of cytosolic and membrane fractions were then subjected to immunoblotting using isozyme-specific anti-PKC antibodies. Specificity of membrane fractionation was determined by histone H1, a nuclear protein that mainly localizes in the P1: nuclear fraction, and MEK-1, a marker of cytosol protein, present in the S: cytosol fraction but not in the P1 or P2 fractions (23,31).…”

C3G-mediated suppression of oncogene-induced focus formation in fibroblasts involves inhibition of ERK activation, cyclin A expression and alterations of anchorage-independent growth

“…After treatment, cells were washed twice with cold phosphate-buffered saline (PBS) and the levels of Ras-GTP were determined using an 'Ras activation assay kit' (Upstate Biotechnology, Lake Placid, NY, USA) as described previously (Guerrero et al, 2002).…”