title: Epidermal growth factor potentiates cholecystokinin/gastrin receptor-mediated Ca2+ release by activation of mitogen-activated protein kinases.
abstract: Small differences in amplitude, duration, and temporal patterns of change in the concentration of free intracellular Ca2+ ([Ca2+](i)) can profoundly affect cell physiology, altering programs of gene expression, cell proliferation, secretory activity, and cell survival. We report a novel mechanism for amplitude modulation of [Ca2+](i) that involves mitogen-activated protein kinase (MAPK). We show that epidermal growth factor (EGF) potentiates gastrin-(1-17) (G17)-stimulated Ca2+ release from intracellular Ca2+ stores through a MAPK-dependent pathway. G17 activation of the cholecystokinin/gastrin receptor (CCK(2)R), a G protein-coupled receptor, stimulates release of Ca2+ from inositol 1,4,5-triphosphate-sensitive Ca2+ stores. Pretreating rat intestinal epithelial cells expressing CCK(2)R with EGF increased the level of G17-stimulated Ca2+ release from intracellular stores. The stimulatory effect of EGF on CCK(2)R-mediated Ca2+ release requires activation of the MAPK kinase (MEK)1,2/extracellular signal-regulated kinase (ERK)1,2 pathway. Inhibition of the MEK1,2/ERK1,2 pathway by either serum starvation or treatment with selective MEK1,2 inhibitors PD98059 and U0126 or expression of a dominant-negative mutant form of MEK1 decreased the amplitude of the G17-stimulated Ca2+ release response. Activation of the MEK1,2/ERK1,2 pathway either by pretreating cells with EGF or by expression of constitutively active K-ras (K-rasV12G) or MEK1 (MEK1*) increased the amplitude of G17-stimulated Ca2+ release. Although EGF, MEK1*, and K-rasV12G activated the MEK1,2/ERK1,2 pathway, they did not increase [Ca2+](i) in the absence of G17. These data demonstrate that the activation state of the MEK1,2/ERK1,2 pathway can modulate the amplitude of the CCK(2)R-mediated Ca2+ release response and identify a novel mechanism for cross-talk between EGF receptor- and CCK(2)R-regulated signaling pathways.
authors: Department of Surgery, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA.
authors: Barbara
authors: B
authors: Olszewska-Pazdrak
authors: Kirk L
authors: KL
authors: Ives
authors: Jeseong
authors: J
authors: Park
authors: Courtney M
authors: CM
authors: Townsend
authors: Mark R
authors: MR
authors: Hellmich
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005755:Gastrins / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D051381:Rats; D011949:Receptors, Cholecystokinin / Q000502:physiology*
chemical_list: D005755:Gastrins; D011949:Receptors, Cholecystokinin; D004815:Epidermal Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium