title: Mono-ADP-ribosylation of the G protein betagamma dimer is modulated by hormones and inhibited by Arf6.
abstract: Mono-ADP-ribosylation is a reversible post-translational modification that can modulate the functions of target proteins. We have previously demonstrated that the β subunit of heterotrimeric G proteins is endogenously mono-ADP-ribosylated, and once modified, the βγ dimer is inactive toward its effector enzymes. To better understand the physiological relevance of this post-translational modification, we have studied its hormonal regulation. Here, we report that Gβ subunit mono-ADP-ribosylation is differentially modulated by G protein-coupled receptors. In intact cells, hormone stimulation of the thrombin receptor induces Gβ subunit mono-ADP-ribosylation, which can affect G protein signaling. Conversely, hormone stimulation of the gonadotropin-releasing hormone receptor (GnRHR) inhibits Gβ subunit mono-ADP-ribosylation. We also provide the first demonstration that activation of the GnRHR can activate the ADP-ribosylation factor Arf6, which in turn inhibits Gβ subunit mono-ADP-ribosylation. Indeed, removal of Arf6 from purified plasma membranes results in loss of GnRHR-mediated inhibition of Gβ subunit mono-ADP-ribosylation, which is fully restored by re-addition of purified, myristoylated Arf6. We show that Arf6 acts as a competitive inhibitor of the endogenous ADP-ribosyltransferase and is itself modified by this enzyme. These data provide further understanding of the mechanisms that regulate endogenous ADP-ribosylation of the Gβ subunit, and they demonstrate a novel role for Arf6 in hormone regulation of Gβ subunit mono-ADP-ribosylation.
authors.affiliation: G Protein-mediated Signalling Laboratory, Consorzio Mario Negri Sud, Via Nazionale, 8/A 66030 Santa Maria Imbaro (Chieti), Italy. nadia.dani@ircc.it
authors.forename: Nadia
authors.initials: N
authors.lastname: Dani
authors.forename: Emilia
authors.initials: E
authors.lastname: Mayo
authors.forename: Annalisa
authors.initials: A
authors.lastname: Stilla
authors.forename: Adriano
authors.initials: A
authors.lastname: Marchegiani
authors.forename: Simone
authors.initials: S
authors.lastname: Di Paola
authors.forename: Daniela
authors.initials: D
authors.lastname: Corda
authors.forename: Maria
authors.initials: M
authors.lastname: Di Girolamo
mesh_terms: D036002:ADP Ribose Transferases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000246:Adenosine Diphosphate Ribose / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D002417:Cattle; D006224:Cricetinae; D003412:Cricetulus; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000235:genetics / Q000378:metabolism*; D006728:Hormones / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000502:physiology*; D011966:Receptors, LHRH / Q000235:genetics / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; C484844:GNRHR protein, human; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D006728:Hormones; D011966:Receptors, LHRH; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human