alpha 3*and alpha 7 nAChR-mediated Ca2+ transient generation in IMR-32 neuroblastoma cells

作者：Ween Hilde; Thorin Hagene Kirsten; Andersen Elisabeth; Gronlien Jens Halyard; Lee Chih Hung; Gopalakrishnan Murali; Malysz John^*

来源：Neurochemistry International, 2010, 57(3): 269-277.

DOI：10.1016/j.neuint.2010.06.005

• Ca2+ signaling
• IMR-32 neuroblastoma
• Nicotinic acetylcholine receptor
• alpha 3
• alpha 7
• Ca2+ imaging
• Patch clamp

alpha 3-Containing (alpha 3*) and alpha 7 nicotinic acetylcholine receptors (nAChRs) are expressed in human IMR-32 neuroblastoma cells and implicated in Ca2+ signaling. In this study, we investigated the intracellular Ca2+ transient generation evoked by selective activation of alpha 3* (agonist potency rank order: epibatidine > varenicline > nicotine approximate to cytisine) and alpha 7 (rank order in the presence of alpha 7 positive allosteric modulator or PAM: A-795723> NS6784 approximate to PNU-282987) using, respectively, varenicline and NS6784 (+alpha 7 PAM) by Ca2+ imaging. Effects of inhibitors of nAChRs (MLA and mecamylamine), ER Ca2+ ATPase pump (CPA and thapsigargin), Ca2+-induced Ca2+ release (ryanodine and dantrolene), Ca2+ channels (nitrendipine, diltiazem, and Cd2+), and removal of extracellular Ca2+ were examined. alpha 7 PAMs, when tested in the presence of NS6784, were more active when added first, followed by the agonist, than in the reverse order. Removal of extracellular Ca2+ - but not CPA, thapsigargin, ryanodine, dantrolene, nitrendipine, diltiazem, or Cd2+ - diminished the alpha 7 agonist-evoked Ca2+ transients. In contrast, only diltiazem and nitrendipine and removal of extracellular Ca2+ inhibited the alpha 3*-mediated Ca2+ transients. The differential effect of diltiazem and nitrendipine versus Cd2+ was due to direct inhibition of alpha 3* nAChRs as revealed by Ca2+ imaging in HEK-293 cells expressing human alpha 3 beta 4 nAChRs and patch clamp in IMR-32 cells. In summary, this study provides evidence that alpha 3* and alpha 7 nAChR agonist-evoked global Ca2+ transient generation in IMR-32 cells does not primarily involve voltage-dependent Ca2+ channels, intracellular Ca2+ stores, or Ca2+-induced Ca2+ release. These mechanisms may, however, be still involved in other forms of nAChR-mediated Ca2+ signaling.

• 出版日期2010-10