Non-neuronal alpha 7 nicotinic receptor regulates cell signaling in human mammary epithelial cell lines

Abstract

Nicotine acetylcholine receptors (nAChRs) constitute a heterologous family of ion channels that mediate fast synaptic transmission in neurons. They are also expressed in numerous cell types, where they have other functions well beyond neurotransmission such as cell proliferation or migration. Nicotine has been implicated in cancer progression by activation of nAChRs, mainly through pentameric α7 and α9 receptors. Here we examine the possible downstream signaling pathway of the α7 nAChR in human breast cell lines. For this purpose, MCF-10A, MCF-7, MDA-MB-231 and T47D cells were used. By using RT-PCR and Western Blot, we determined the expression of the α7 nAChR subunit in all cell lines. No expression o the α9 nAChR subunit was detected. Relative quantitation (qPCR) demonstrated up-regulation of the α7 subunit expression in MCF-7 cells after 48 hr incubation with nicotine (10 μM). Kinetics of α7 activation by a specific agonist PNU-282987 demonstrated an increase of ERK1/2 and Akt phosphorylation, in all cell lines, measured by Western blot. Moreover, PNU-282987 incubation stimulated significantly MCF-7 cell proliferation, and this effect was reversed by the α7 specific antagonist bungarotoxin. These results highlight the pathophysiological role of α7 receptors in promoting cell growth and intracellular signaling and provide a framework for the development of new drugs that specifically target these receptors.