Activation of MAP kinase by muscarinic cholinergic receptors induces cell proliferation and protein synthesis in human breast cancer cells

✍ Scribed by Eugenio Jiménez; Mercedes Montiel

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 378 KB
• Volume: 204
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.20326

✦ Synopsis

Abstract

Carbachol (Cch), a muscarinic acetylcholine receptor (mAChR) agonist, increases intracellular‐free Ca^2+^ mobilization and induces mitogen‐activated protein kinase/extracellular signal‐regulated kinase (MAPK/ERK) phosphorylation in MCF‐7 human breast cancer cells. Pretreatment of cells with the selective phospholipase C (PLC) inhibitor U73122, or incubation of cells in a Ca^2+^‐free medium did not alter Cch‐stimulated MAPK/ERK phosphorylation. Phosphorylation of MAPK/ERK was mimicked by phorbol 12‐myristate acetate (PMA), an activator of protein kinase C (PKC), but Cch‐evoked MAPK/ERK activation was unaffected by down‐regulation of PKC or by pretreatment of cells with GF109203X, a PKC inhibitor. However, Cch‐stimulated MAPK/ERK phosphorylation was completely blocked by myristoylated PKC‐ζ pseudosubstrate, a specific inhibitor of PKC‐ζ, and high doses of staurosporine. Pretreatment of human breast cancer cells with wortmannin or LY294002, selective inhibitors of phosphoinositide 3‐kinase (PI3K), diminished Cch‐mediated MAPK/ERK phosphorylation. Similar results were observed when MCF‐7 cells were pretreated with genistein, a non‐selective inhibitor of tyrosine kinases, or with the specific Src tyrosine kinase inhibitor PP2. Moreover, in MCF‐7 human breast cancer cells mAChR stimulation induced an increase of protein synthesis and cell proliferation, and these effects were prevented by PD098059, a specific inhibitor of the mitogen activated kinase kinase. In conclusion, analyses of mAChR downstream effectors reveal that PKC‐ζ, PI3K, and Src family of tyrosine kinases, but not intracellular‐free Ca^2+^ mobilization or conventional and novel PKC activation, are key molecules in the signal cascade leading to MAPK/ERK activation. In addition, MAPK/ERK are involved in the regulation of growth and proliferation of MCF‐7 human breast cancer cells. © 2005 Wiley‐Liss, Inc.