title: Direct involvement of G protein alpha(q/11) subunit in regulation of muscarinic receptor-mediated sAPPalpha release.
abstract: The G(q/11) protein-coupled receptors, such as muscarinic (M1 & M3) receptors, have been shown to regulate the release of a soluble amyloid precursor protein (sAPPalpha) produced from alpha-secretase processing. However, there is no direct evidence for the precise characteristics of G proteins, and the signaling mechanism for the regulation of G(q/11) protein-coupled receptor-mediated sAPPalpha release is not clearly understood. This study examined whether the muscarinic receptor-mediated release of sAPPalpha is directly regulated by Galpha(q/11) proteins. The HEK293 cells were transiently cotransfected with muscarinic M3 receptors and a dominant-negative minigene construct of the G protein alpha subunit. The sAPPalpha release in the media was measured using an antibody specific for sAPP. The sAPPalpha release enhancement induced by muscarinic receptor stimulation was decreased by a G(q/11) minigene construct, whereas it was not blocked by a control minigene construct (the Galpha carboxy peptide in random order, Galpha(q)R) or Galpha(i) constructs. This indicated a direct role of the Galpha(q/11) protein in the regulation of muscarinic M3 receptor-mediated sAPPalpha release. We also investigated whether the transactivation of the epidermal growth factor receptor (EGFR) by a muscarinic agonist could regulate the sAPPalpha release in SH-SY5Y cells. Pretreatment of a specific EGFR kinase inhibitor, tyrophostin AG1478 (250 nM), blocked the EGF-stimulated sAPPalpha release, but did not block the oxoM-stimulated sAPPalpha release. This demonstrated that the transactivation of the EGFR by muscarinic receptor activation was not involved in the muscarinic receptor-mediated sAPPalpha release.
authors.affiliation: Division of Pharmaceutical Bioscience, College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Jin Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Hwa-Jung
authors.initials: HJ
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D018721:Muscarinic Agonists / Q000494:pharmacology; D011799:Quinazolines; D012334:RNA, Neoplasm / Q000096:biosynthesis; D020239:Receptor Cross-Talk / Q000187:drug effects; D043587:Receptor, Muscarinic M3 / Q000187:drug effects / Q000235:genetics; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000685:Serum Amyloid A Protein / Q000378:metabolism*; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D018721:Muscarinic Agonists; D011799:Quinazolines; D012334:RNA, Neoplasm; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D000685:Serum Amyloid A Protein; D020032:Tyrphostins; C101044:RTKI cpd; D004815:Epidermal Growth Factor; D043802:GTP-Binding Protein alpha Subunits, Gq-G11