Deciphering Specificity Determinants for FR900359‐Derived G_qα Inhibitors Based on Computational and Structure–Activity Studies

Abstract

Direct targeting of intracellular Gα subunits of G protein-coupled receptors by chemical tools is a challenging task in current pharmacological studies and in the development of novel therapeutic approaches. In this study we analyzed novel FR900359-based analogs from natural sources, synthetic cyclic peptides, as well as all so-far known G α inhibitors in a comprehensive study to devise a strategy for the elucidation of characteristics that determine interactions with and inhibition of G in the specific FR/YM-binding pocket. Using 2D NMR spectroscopy and molecular docking we identified unique features in the macrocyclic structures responsible for binding to the target protein correlating with inhibitory activity. While all novel compounds were devoid of effects on G and G proteins, no inhibitor surpassed the biological activity of FR. This raises the question of whether depsipeptides such as FR already represent valuable chemical tools for specific inhibition of G and, at the same time, are suitable natural lead structures for the development of novel compounds to target Gα subunits other than G .

Recent achievements in developing selective Gq inhibitors

“…The IP 1 and cAMP assays used to examine the biological activity of YM‐254890 and related analogs were also used to measure the inhibitory effects of FR900359 and related analogs on G q ‐mediated signaling, while the experimental setups were different in terms of cell number, cell incubation time, concentration of related agents, and the machine of detection. These different experimental set ups might account for the variation in potency of the same compounds as previously reported (Figure ) . Moreover, two semisynthetic analogs of FR900359 were also reported, which were obtained either by esterification of the β‐HyLeu‐1 hydroxyl group with hexanoic anhydride ( 52 , Figure ), or by Michael addition, applying 2‐aminoethanethiol to form the corresponding thioether at the double bond of N ‐MeDha ( 53 , Figure ).…”

“…b, Inhibition of the adenosine diphosphate (ADP)‐induced platelet aggregation in human platelet‐rich plasma . c, d, and e, Inhibition of carbachol‐induced inositol monophosphate (IP 1 ) production in Chinese hamster ovary (CHO) cells that stably express the M 1 muscarinic receptor in different papers: (c) from Xiong et al, (d) from Zhang et al and Xiong et al, and (e) from Reher et al Equipotent analogs are highlighted (pink). The chemical structures were determined by mass spectrometry, one‐ and two‐dimensional nuclear magnetic resonance (NMR) spectrum analysis, chiral high‐performance liquid chromatography (HPLC), Marfey's analysis, high‐resolution mass spectroscopy (HRMS), infrared spectroscopy (IR), and optical rotation.…”

“…d, Inhibition of the adenosine diphosphate (ADP)‐induced platelet aggregation in vitro . e, f, g, h, i, and j, Inhibition of carbachol‐induced IP 1 production in Chinese hamster ovary (CHO) cells that stably express the M 1 muscarinic receptor in different papers: (e) from Xiong et al, (f) from Xiong et al, (g) from Zhang et al, (h) from Zhang et al, (i) from Reher et al, and (j) from Zhang…”

“…C, The yield only for semisynthesis step. a, b, c, and d, Inhibition of carbachol‐induced inositol monophosphate (IP 1 ) production in Chinese hamster ovary (CHO) cells that stably express the M 1 muscarinic receptor in different papers: a and b from Xiong et al, c from Reher et al and d from Schrage et al e, Inhibition of [ 35 S] GTPγS uptake (up to 40% inhibition) in the receptor assisted [ 35 S] GTPγS binding assay mass spectrometry, one‐ and two‐dimensional nuclear magnetic resonance (NMR) spectrum analysis, liquid chromatography‐mass spectrometry (LC‐MS), extracted ion chromatograms, high‐performance liquid chromatography (HPLC), high‐resolution mass spectroscopy (HRMS), amino acid analysis and optical rotation.…”

“…Reher et al reported the synthesis of 10 simplified FR900359 analogs ( 42 ‐ 51 , Figure ) by a standard SPPS Fmoc‐protocol …”