title: Selective Gαi subunits as novel direct activators of transient receptor potential canonical (TRPC)4 and TRPC5 channels.
abstract: The ubiquitous transient receptor potential canonical (TRPC) channels function as non-selective, Ca(2+)-permeable channels and mediate numerous cellular functions. It is commonly assumed that TRPC channels are activated by stimulation of Gα(q)-PLC-coupled receptors. However, whether the Gα(q)-PLC pathway is the main regulator of TRPC4/5 channels and how other Gα proteins may regulate these channels are poorly understood. We previously reported that TRPC4/TRPC5 can be activated by Gα(i). In the current work, we found that Gα(i) subunits, rather than Gα(q), are the primary and direct activators of TRPC4 and TRPC5. We report a novel molecular mechanism in which TRPC4 is activated by several Gα(i) subunits, most prominently by Gα(i2), and TRPC5 is activated primarily by Gα(i3). Activation of Gα(i) by the muscarinic M2 receptors or expression of the constitutively active Gα(i) mutants equally and fully activates the channels. Moreover, both TRPC4 and TRPC5 are activated by direct interaction of their conserved C-terminal SESTD (SEC14-like and spectrin-type domains) with the Gα(i) subunits. Two amino acids (lysine 715 and arginine 716) of the TRPC4 C terminus were identified by structural modeling as mediating the interaction with Gα(i2). These findings indicate an essential role of Gα(i) proteins as novel activators for TRPC4/5 and reveal the molecular mechanism by which G-proteins activate the channels.
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Jae-Pyo
authors.initials: JP
authors.lastname: Jeon
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Chansik
authors.initials: C
authors.lastname: Hong
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Eun Jung
authors.initials: EJ
authors.lastname: Park
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Ju-Hong
authors.initials: JH
authors.lastname: Jeon
authors.affiliation: Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: Nam-Hyuk
authors.initials: NH
authors.lastname: Cho
authors.affiliation: Department of Biochemistry, Seoul National University College of Medicine, Seoul 110-799, Korea.
authors.forename: In-Gyu
authors.initials: IG
authors.lastname: Kim
authors.affiliation: Department of Physiology, University of Ulsan College of Medicine, Seoul 136-748, Korea.
authors.forename: Han
authors.initials: H
authors.lastname: Choe
authors.affiliation: Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Shmuel
authors.initials: S
authors.lastname: Muallem
authors.affiliation: Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea. Electronic address: kimhyunjin@skku.edu.
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea. Electronic address: insuk@snu.ac.kr.
authors.forename: Insuk
authors.initials: I
authors.lastname: So
mesh_terms: D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000235:genetics / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D009154:Mutation; D017434:Protein Structure, Tertiary; D043585:Receptor, Muscarinic M2 / Q000235:genetics / Q000378:metabolism; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D043585:Receptor, Muscarinic M2; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; C491780:TRPC5 protein, human; D051960:GTP-Binding Protein alpha Subunit, Gi2; D043802:GTP-Binding Protein alpha Subunits, Gq-G11