title: Ric-8A-mediated stabilization of the trimeric G protein subunit Gαi is inhibited by pertussis toxin-catalyzed ADP-ribosylation.
abstract: The heterotrimeric G protein subunit Gαi can be activated by G protein-coupled receptors and the cytosolic protein Ric-8A, the latter of which is also known to prevent ubiquitin-dependent degradation of Gαi. Here we show that the amounts of the three Gαi-related proteins Gαi1, Gαi2, and Gαi3, but not that of Gαq, are rapidly decreased by cell treatment with pertussis toxin (PTX). The decrease appears to be due to ADP-ribosylation of Gαi, because PTX treatment does not affect the amount of a mutant Gαi2 carrying alanine substitution for Cys352, the residue that is ADP-ribosylated by the toxin. The presence of endogenous and exogenous Ric-8A increases Gαi stability as shown in cells treated with the protein synthesis inhibitor cycloheximide; however, Ric-8A fails to efficiently stabilize ADP-ribosylated Gαi. The failure agrees with the inability of Ric-8A to bind to ADP-ribosylated Gαi both in vitro and in vivo. Thus PTX appears to exert its pathological effects at least in part by converting Gαi to an unstable ADP-ribosylated form, in addition to the well-known inability of ADP-ribosylated Gαi to transduce signals triggered by G protein-coupled receptors.
authors.affiliation: Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Chishiki
authors.affiliation: Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Kamakura
authors.affiliation: Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
authors.forename: Junya
authors.initials: J
authors.lastname: Hayase
authors.affiliation: Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Yuzawa
authors.affiliation: Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan. Electronic address: hsumi@med.kyushu-u.ac.jp.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sumimoto
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004285:Dogs; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000737:chemistry / Q000378:metabolism; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D051379:Mice; D037342:Pertussis Toxin / Q000633:toxicity*; D055550:Protein Stability / Q000187:drug effects; D000067996:RAW 264.7 Cells; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D011994:Recombinant Proteins; C561938:Ric8A protein, human; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11
keywords: ADP-ribosylation; Gαi; Pertussis toxin; Ric-8A