RT Journal Article
SR Electronic
T1 Lysophosphatidic Acid Induces Rapid and Sustained Decreases in Epidermal Growth Factor Receptor Binding via Different Signaling Pathways in BEAS-2B Airway Epithelial Cells
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 809
OP 817
DO 10.1124/jpet.107.133736
VO 325
IS 3
A1 Karen M. Kassel
A1 Puttappa R. Dodmane
A1 Nancy A. Schulte
A1 Myron L. Toews
YR 2008
UL http://jpet.aspetjournals.org/content/325/3/809.abstract
AB Lysophosphatidic acid (LPA) and epidermal growth factor (EGF) are important mediators of lung cell function and lung diseases. We showed previously that LPA decreases epidermal growth factor receptor (EGFR) binding rapidly in BEAS-2B airway epithelial cells, and this decrease is sustained to at least 18 h. The current studies investigate which LPA signaling pathways mediate the rapid versus sustained decreases in EGFR binding in BEAS-2B cells. The Gi/o inhibitor pertussis toxin and the Rho kinase inhibitor Y-27632 [(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide] had no effect on the rapid or sustained decreases. However, the mitogen-activated protein kinase kinase (MEK) inhibitor U0126 [1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)-butadiene ethanolate] decreased extracellular signal-regulated kinase (ERK) 1/2 phosphorylation, completely inhibited the rapid decrease in binding, and partially inhibited the sustained decrease. The direct Ca2+- and phospholipid-dependent protein kinase (PKC) activator phorbol-12-myristate-13-acetate stimulated ERK1/2 phosphorylation and decreased EGFR binding at both 15 min and 18 h. Furthermore, inhibitors of PKC partially inhibited ERK1/2 phosphorylation and the 15-min decrease but completely inhibited the 18-h decrease. Inhibitor time course studies showed that PKC induction of the 18-h decrease occurred during the first 3 h of treatment. We showed previously that LPA-stimulated EGFR transactivation contributes to the rapid decrease. Two transactivation inhibitors partially inhibited ERK1/2 phosphorylation, and U0126 partially inhibited EGFR transactivation, indicating that MEK may be involved both upstream and downstream of EGFR activation. Together, the data presented here indicate that LPA mediates the rapid decrease in EGFR binding via EGFR transactivation, MEK/ERK, and PKC, whereas the sustained decrease is regulated primarily by PKC. The American Society for Pharmacology and Experimental Therapeutics