title: Mechanism of action and structural requirements of constrained peptide inhibitors of RGS proteins.
abstract: Regulators of G-protein signaling (RGS) accelerate guanine triphosphate hydrolysis by Galpha-subunits and profoundly inhibit signaling by G protein-coupled receptors. The distinct expression patterns and pathophysiologic regulation of RGS proteins suggest that inhibitors may have therapeutic potential. We previously reported the design of a constrained peptide inhibitor of RGS4 (1: Ac-Val-Lys-[Cys-Thr-Gly-Ile-Cys]-Glu-NH2, S-S) based on the structure of the Galphai switch 1 region but its mechanism of action was not established. In the present study, we show that 1 inhibits RGS4 by mimicking and competing for binding with the switch 1 region of Galphai and that peptide 1 shows selectivity for RGS4 and RGS8 versus RGS7. Structure-activity relationships of analogs related to 1 are described that illustrate key features for RGS inhibition. Finally, we demonstrate activity of the methylene dithioether-bridged peptide inhibitor, 2, to modulate muscarinic receptor-regulated potassium currents in atrial myocytes. These data support the proposed mechanism of action of peptide RGS inhibitors, demonstrate their action in native cells, and provide a starting point for the design of RGS inhibitor drugs.
authors.affiliation: Department of Pharmacology, 1150 W. Medical Center Dr, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Roof
authors.forename: Yafei
authors.initials: Y
authors.lastname: Jin
authors.forename: David L
authors.initials: DL
authors.lastname: Roman
authors.forename: Roger K
authors.initials: RK
authors.lastname: Sunahara
authors.forename: Masaru
authors.initials: M
authors.lastname: Ishii
authors.forename: Henry I
authors.initials: HI
authors.lastname: Mosberg
authors.forename: Richard R
authors.initials: RR
authors.lastname: Neubig
mesh_terms: D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism; D005998:Glycine / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D020710:RGS Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D012694:Serine / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D013997:Time Factors
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D044385:GTP-Binding Protein alpha Subunits; D020690:GTPase-Activating Proteins; D010456:Peptides, Cyclic; D020710:RGS Proteins; C512140:acetyl-valyl-lysyl-cyclo(cysteinyl-threonyl-glycyl-isoleucyl-cysteinyl)-glutamamide; C098799:RGS4 protein; D012694:Serine; D020558:GTP Phosphohydrolases; D000109:Acetylcholine; D005998:Glycine