A Nanomolar-Potency Small Molecule Inhibitor of Regulator of G-Protein Signaling Proteins

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• 作者：Levi L. Blazer ; Haoming Zhang ; Emma M. Casey ; Stephen M. Husbands ; Richard R. Neubig
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：April 19, 2011
• 年：2011
• 卷：50
• 期：15
• 页码：3181-3192
• 全文大小：1147K
• 年卷期：v.50,no.15(April 19, 2011)
• ISSN：1520-4995

文摘

Regulators of G-protein signaling (RGS) proteins are potent negative modulators of signal transduction through G-protein-coupled receptors. They function by binding to activated (GTP-bound) G伪 subunits and accelerating the rate of GTP hydrolysis. Modulation of RGS activity by small molecules is an attractive mechanism for fine-tuning GPCR signaling for therapeutic and research purposes. Here we describe the pharmacologic properties and mechanism of action of CCG-50014, the most potent small molecule RGS inhibitor to date. It has an IC₅₀ for RGS4 of 30 nM and is >20-fold selective for RGS4 over other RGS proteins. CCG-50014 binds covalently to the RGS, forming an adduct on two cysteine residues located in an allosteric regulatory site. It is not a general cysteine alkylator as it does not inhibit activity of the cysteine protease papain at concentrations >3000-fold higher than those required to inhibit RGS4 function. It is also >1000-fold more potent as an RGS4 inhibitor than are the cysteine alkylators N-ethylmaleimide and iodoacetamide. Analysis of the cysteine reactivity of the compound shows that compound binding to Cys¹⁰⁷ in RGS8 inhibits G伪 binding in a manner that can be reversed by cleavage of the compound鈭扲GS disulfide bond. If the compound reacts with Cys¹⁶⁰ in RGS8, the adduct induces RGS denaturation, and activity cannot be restored by removal of the compound. The high potency and good selectivity of CCG-50014 make it a useful tool for studying the functional roles of RGS4.