title: The sigma-1 receptor antagonist PB212 reduces the Ca²⁺-release through the inositol (1, 4, 5)-trisphosphate receptor in SK-N-SH cells.
abstract: Sigma-1 receptors are specifically located at the endoplasmic reticulum-mitochondrion interface, but upon stimulation by ligands or under prolonged cellular stress, they translocate to other areas of the cell. Sigma-1 receptors are involved in the regulation of intracellular [Ca(2+)] by affecting the Ca(2+)-influx or the release from intracellular stores. In SK-N-SH cells, we measured the affinity of 4-methyl-1-[4-(6-methoxynaphthalen-1-yl)butyl]piperidine (PB212) at sigma-1 receptor by using a competition binding assay with specific radioligand; we obtained a K(i) value=316 ± 19 nM. PB212 also showed an antiproliferative effect in SK-N-SH cells (EC(50)=32 ± 4 μM) but had no effect in MCF7 cells, which only express sigma-2 receptor; these findings suggest that PB212 behaves as a sigma-1 receptor antagonist. We have studied the effect of PB212 on Ca(2+) homeostasis of the SK-N-SH cell line with the fluorescent probe Fura-2. 100 μM PB212 induced a Ca(2+)-efflux from the endoplasmic reticulum through the inositol (1, 4, 5)-trisphosphate (IP(3)) receptor. Moreover, [PB212] ranging from 1 to 100μM reduced the Ca(2+)-response, triggered by carbachol or bradykinin that engage the phospholipase C/IP(3) pathway; such a response is generally increased by sigma-1 receptor agonists. On the other hand, PB212 did not reduce the Ca(2+)-response mediated by IP(3) in LoVo cells, which do not express neither sigma-1 nor sigma-2 receptors, and in MCF7 cells. The fact that the activity of the sigma-1 receptor can be experimentally modulated by agonists and antagonists supports the intriguing hypothesis that some endogenous molecules, unknown at the moment, modulate the sigma-1 receptor and its cellular targets.
authors.affiliation: Dipartimento di Bioscienze, Biotecnologie e Scienze Farmacologiche, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Gasparre
authors.forename: Carmen
authors.initials: C
authors.lastname: Abate
authors.forename: Francesco
authors.initials: F
authors.lastname: Berardi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cassano
mesh_terms: D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008024:Ligands; D009281:Naphthalenes / Q000378:metabolism / Q000494:pharmacology*; D010880:Piperidines / Q000378:metabolism / Q000494:pharmacology*; D017480:Receptors, sigma / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013379:Substrate Specificity; D000097605:Sigma-1 Receptor
chemical_list: D002118:Calcium; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008024:Ligands; D009281:Naphthalenes; D010880:Piperidines; D017480:Receptors, sigma; D000097605:Sigma-1 Receptor; C574778:PB212; C032727:piperidine