title: Selectivity and anti-Parkinson's potential of thiadiazolidinone RGS4 inhibitors.
abstract: Many current therapies target G protein coupled receptors (GPCR), transporters, or ion channels. In addition to directly targeting these proteins, disrupting the protein-protein interactions that localize or regulate their function could enhance selectivity and provide unique pharmacologic actions. Regulators of G protein signaling (RGS) proteins, especially RGS4, play significant roles in epilepsy and Parkinson's disease. Thiadiazolidinone (TDZD) inhibitors of RGS4 are nanomolar potency blockers of the biochemical actions of RGS4 in vitro. Here, we demonstrate the substantial selectivity (8- to >5000-fold) of CCG-203769 for RGS4 over other RGS proteins. It is also 300-fold selective for RGS4 over GSK-3β, another target of this class of chemical scaffolds. It does not inhibit the cysteine protease papain at 100 μM. CCG-203769 enhances Gαq-dependent cellular Ca(2+) signaling in an RGS4-dependent manner. TDZD inhibitors also enhance Gαi-dependent δ-OR inhibition of cAMP production in SH-SY-5Y cells, which express endogenous receptors and RGS4. Importantly, CCG-203769 potentiates the known RGS4 mechanism of Gαi-dependent muscarinic bradycardia in vivo. Furthermore, it reverses raclopride-induced akinesia and bradykinesia in mice, a model of some aspects of the movement disorder in Parkinson's disease. A broad assessment of compound effects revealed minimal off-target effects at concentrations necessary for cellular RGS4 inhibition. These results expand our understanding of the mechanism and specificity of TDZD RGS inhibitors and support the potential for therapeutic targeting of RGS proteins in Parkinson's disease and other neural disorders.
authors.affiliation: †Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States.
authors.forename: Levi L
authors.initials: LL
authors.lastname: Blazer
authors.affiliation: †Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States.|‡Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Storaska
authors.affiliation: †Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Jutkiewicz
authors.affiliation: §Department of Pharmacy and Pharmacology, University of Bath, Bath, U.K.
authors.forename: Emma M
authors.initials: EM
authors.lastname: Turner
authors.affiliation: ∥Section of Pharmacology, Department of Medical Science, University of Ferrara, Ferrara, Italy 44121.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Calcagno
authors.affiliation: †Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Wade
authors.affiliation: †Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States.
authors.forename: Qin
authors.initials: Q
authors.lastname: Wang
authors.affiliation: ⊥National Institute of Mental Health Psychoactive Drug Screening Program (NIMH PDSP), Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
authors.forename: Xi-Ping
authors.initials: XP
authors.lastname: Huang
authors.affiliation: †Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States.
authors.forename: John R
authors.initials: JR
authors.lastname: Traynor
authors.affiliation: §Department of Pharmacy and Pharmacology, University of Bath, Bath, U.K.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Husbands
authors.affiliation: ∥Section of Pharmacology, Department of Medical Science, University of Ferrara, Ferrara, Italy 44121.
authors.forename: Michele
authors.initials: M
authors.lastname: Morari
authors.affiliation: ‡Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, United States.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Neubig
mesh_terms: D000818:Animals; D000978:Antiparkinson Agents / Q000494:pharmacology*; D001919:Bradycardia / Q000188:drug therapy / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D045744:Cell Line, Tumor; D018679:Cholinergic Agonists / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D010206:Papain / Q000378:metabolism; D020734:Parkinsonian Disorders / Q000188:drug therapy / Q000503:physiopathology; D020710:RGS Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020891:Raclopride; D017207:Rats, Sprague-Dawley
chemical_list: D000978:Antiparkinson Agents; D018679:Cholinergic Agonists; D020710:RGS Proteins; C098799:RGS4 protein; D020891:Raclopride; D002217:Carbachol; D000242:Cyclic AMP; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D010206:Papain; D002118:Calcium
keywords: PPI; Parkinson’s disease; RGS; Regulator of G-protein signaling; protein−protein interaction; thiadiazolidinone