title: Galanin decreases proliferation of PC12 cells and induces apoptosis via its subtype 2 receptor (GalR2).
abstract: Galanin is a neuropeptide with a wide range of effects in the nervous and endocrine systems, mediated through three G protein-coupled receptor subtypes (GalR1-3). Interestingly, galanin and its receptors are also expressed in certain tumors. Here we studied the effects of galanin in rat pheochromocytoma (PC12) cells stably transfected with GFP-tagged GalR2. Galanin at 100 nM inhibited cell proliferation in both nontransfected and transfected cells. Conversly, both galanin and the GalR2(R3)-agonist AR-M1896 induced caspase-dependent apoptotic cell death only in GalR2-transfected cells. Western-blot analyses of downstream mediators of the G(q/11)-type G protein showed down-regulation of pAkt and pBad in galanin-exposed transfected cells. Also, the specific PI3 kinase inhibitor LY-294002 increased the level of pBad and decreased activation of caspases. In addition, p21(cip1) levels were up-regulated in galanin-exposed PC12 cells and down-regulated in galanin-exposed GalR2-transfected cells. In agreement, FACS analyses of galanin exposed cells showed occurrence of cell cycle arrest in PC12 cells and cell death in transfected cells. Finally, as shown with real-time PCR, galanin and its receptors were expressed at very high levels in human pheochromocytoma tissues as compared with normal adrenal medulla. These findings point to GalR2 as a possible target for therapeuthic interventions in pheochromocytoma.
authors.affiliation: Institute of Environmental Medicine, Division of Toxicology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Tofighi
authors.forename: B
authors.initials: B
authors.lastname: Joseph
authors.forename: S
authors.initials: S
authors.lastname: Xia
authors.forename: Z-Q D
authors.initials: ZQ
authors.lastname: Xu
authors.forename: B
authors.initials: B
authors.lastname: Hamberger
authors.forename: T
authors.initials: T
authors.lastname: Hökfelt
authors.forename: S
authors.initials: S
authors.lastname: Ceccatelli
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D019004:Galanin / Q000235:genetics / Q000494:pharmacology*; D005786:Gene Expression Regulation; D006801:Humans; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D044091:Receptor, Galanin, Type 1 / Q000235:genetics; D044092:Receptor, Galanin, Type 2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D044091:Receptor, Galanin, Type 1; D044092:Receptor, Galanin, Type 2; D019004:Galanin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases