title: Mastoparan inhibits beta-adrenoceptor-G(s) signaling by changing the localization of Galpha(s) in lipid rafts.
abstract: Mastoparan, a wasp venom toxin, has various pharmacological activities, the mechanisms of which are still unknown. To clarify the action of mastoparan on G protein-coupled receptor-mediated signaling, we previously examined the effect of mastoparan on G(q)-mediated signaling and demonstrated that mastoparan binds to gangliosides causing a decrease in Galpha(q/11) content in lipid rafts, and resulting in the inhibition of G(q)-mediated phosphoinositide hydrolysis (Sugama et al., Mol. Pharmacol., 68, 1466, 2005). In the present study, we examined the effect of mastoparan on beta-adrenoceptor-G(s) signaling in 1321N1 human astrocytoma cells. Mastoparan inhibited isoproterenol-induced elevation of cyclic AMP in a concentration-dependent manner. Although mastoparan is known to be an activator of G(i), pertussis toxin only slightly attenuated mastoparan-induced inhibition of cyclic AMP elevation, suggesting that a major part of the inhibition of cyclic AMP elevation induced by mastoparan is not mediated by Galpha(i). By contrast, mastoparan-induced inhibition of cyclic AMP elevation was clearly attenuated by preincubation of the cells with ganglioside mixtures. Moreover, mastoparan changed the localization of Galpha(s) in lipid rafts without disrupting the structure of lipid rafts. Fluorescent staining analysis showed that mastoparan released GFP-Galpha(s) from plasma membranes into the cytosol. These results suggest that the mastoparan-induced suppression of cyclic AMP elevation is mainly caused by changing the localization of Galpha(s) in lipid rafts into a compartment in the cellular interior where it is not available to activate adenylyl cyclase.
authors: Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors: Jun
authors: J
authors: Sugama
authors: Jiang-Zhou
authors: JZ
authors: Yu
authors: Mark M
authors: MM
authors: Rasenick
authors: Norimichi
authors: N
authors: Nakahata
mesh_terms: D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000096:biosynthesis; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007545:Isoproterenol / Q000494:pharmacology; D021962:Membrane Microdomains / Q000187:drug effects* / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D021381:Protein Transport / Q000187:drug effects; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013347:Subcellular Fractions / Q000187:drug effects; D014862:Wasp Venoms / Q000494:pharmacology*
chemical_list: D044387:GTP-Binding Protein beta Subunits; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011943:Receptors, Adrenergic, beta; D011993:Recombinant Fusion Proteins; D014862:Wasp Venoms; D049452:Green Fluorescent Proteins; C037500:mastoparan; D000242:Cyclic AMP; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D007545:Isoproterenol