Discovery of a functionally selective ghrelin receptor (GHSR1a) ligand for modulating brain dopamine.

SignificanceThe modulation of growth hormone secretagogue receptor-1a (GHSR1a) signaling is a promising strategy for treating brain conditions of metabolism, aging, and addiction. GHSR1a activation results in pleiotropic physiological outcomes through distinct and pharmacologically separable G protein- and ß-arrestin (ßarr)-dependent signaling pathways. Thus, pathway-selective modulation can enable improved pharmacotherapeutics that can promote therapeutic efficacy while mitigating side effects. Here, we describe the discovery of a brain-penetrant small molecule, N8279 (NCATS-SM8864), that biases GHSR1a conformations toward Gαq activation and reduces aberrant dopaminergic behavior in mice. N8279 represents a promising chemical scaffold to advance the development of better treatments for GHSR1a-related brain disorders involving the pathological dysregulation of dopamine.

Probing the hydrophobic pocket of farnesyltransferase: aromatic substitution of CAAX peptidomimetics leads to highly potent inhibitors.

Cysteine farnesylation at the carboxylate terminal tetrapeptide CAAX of Ras protein is catalyzed by farnesyltransferase. This lipid modification is necessary for regulatory function of both normal and oncogenic Ras. The high frequency of Ras mutation in human cancers has prompted an intensive study on finding ways of controlling oncogenic Ras function. Inhibition of farnesyltransferase is among the most sought after targets for cancer chemotherapy. We report here the design, synthesis and biological characterization of a series of peptidomimetics as farnesyltransferase inhibitors. These compounds are extremely potent towards farnesyltransferase with IC50 values ranging from subnanomolar to low nanomolar concentrations. They have a high selectivity for farnesyltransferase over the closely related geranylgeranyltransferase-I. Structure-activity relationship studies demonstrated that a properly positioned hydrophobic group significantly enhanced inhibition potency, reflecting an improved complementarity to the large hydrophobic pocket in the CAAX binding site.