A series of substituted isoindolinones as selective small molecule modulators of the Gβγ‐SNARE interaction

The interaction of G betagamma (Gβγ) subunits with its effectors is a key mechanism for G protein coupled receptor‐mediated signal transduction. One such effector is the soluble N‐ethylmaleimide‐sensitive attachment protein receptor (SNARE) complex, to which Gβγ binds to inhibit exocytosis downstream of calcium release. Starting from a single hit from a focused high‐throughput screen of a library of small molecules designed to block protein‐protein interactions, we have generated relatively potent and selective modulators of Gβγ‐effector interactions, in particular, the interaction of Gβγ with the SNARE protein SNAP25. From this hit, a series of substituted isoindolinones was developed. It was then determined that these compounds were also able to inhibit a second effector of Gβγ subunits, the G‐protein coupled inwardly rectifying potassium channel (GIRK). Utilizing structure‐activity relationships, we were able to further refine the potency and selectivity of these compounds, generating Gβγ‐binding small molecules that were selective for blocking interaction with an individual effector. Finally, we show that these compounds are able to abolish the inhibitory effect of the α 2 adrenergic receptor on vesicle release in neurons. Together, these studies demonstrate the ability to generate selective small molecule modulators of Gβγ‐effector interactions and the suitability of such molecules for investigating mechanisms of G i/o ‐coupled GPCR‐mediated inhibition of exocytosis. Support or Funding Information This work was supported by the National Institutes of Health National Eye Institute [R01‐EY010291]; and the National Institutes of Health National Institute of Mental Health [MH101679‐ 01A1]. ZZ was supported by the T32 Training in Pharmacological Sciences, T32 GM07628.