Small-Molecule Positive Allosteric Modulators of the ß2-Adrenoceptor Isolated from DNA-Encoded Libraries.

Conventional drug discovery efforts at the ß2-adrenoceptor (ß2AR) have led to the development of ligands that bind almost exclusively to the receptor's hormone-binding orthosteric site. However, targeting the largely unexplored and evolutionarily unique allosteric sites has potential for developing more specific drugs with fewer side effects than orthosteric ligands. Using our recently developed approach for screening G protein-coupled receptors (GPCRs) with DNA-encoded small-molecule libraries, we have discovered and characterized the first ß2AR small-molecule positive allosteric modulators (PAMs)-compound (Cmpd)-6 [(R)-N-(4-amino-1-(4-(tert-butyl)phenyl)-4-oxobutan-2-yl)-5-(N-isopropyl-N-methylsulfamoyl)-2-((4-methoxyphenyl)thio)benzamide] and its analogs. We used purified human ß2ARs, occupied by a high-affinity agonist, for the affinity-based screening of over 500 million distinct library compounds, which yielded Cmpd-6. It exhibits a low micro-molar affinity for the agonist-occupied ß2AR and displays positive cooperativity with orthosteric agonists, thereby enhancing their binding to the receptor and ability to stabilize its active state. Cmpd-6 is cooperative with G protein and ß-arrestin1 (a.k.a. arrestin2) to stabilize high-affinity, agonist-bound active states of the ß2AR and potentiates downstream cAMP production and receptor recruitment of ß-arrestin2 (a.k.a. arrestin3). Cmpd-6 is specific for the ß2AR compared with the closely related ß1AR. Structure-activity studies of select Cmpd-6 analogs defined the chemical groups that are critical for its biologic activity. We thus introduce the first small-molecule PAMs for the ß2AR, which may serve as a lead molecule for the development of novel therapeutics. The approach described in this work establishes a broadly applicable proof-of-concept strategy for affinity-based discovery of small-molecule allosteric compounds targeting unique conformational states of GPCRs.

Allosteric "beta-blocker" isolated from a DNA-encoded small molecule library.

The ß2-adrenergic receptor (ß2AR) has been a model system for understanding regulatory mechanisms of G-protein-coupled receptor (GPCR) actions and plays a significant role in cardiovascular and pulmonary diseases. Because all known ß-adrenergic receptor drugs target the orthosteric binding site of the receptor, we set out to isolate allosteric ligands for this receptor by panning DNA-encoded small-molecule libraries comprising 190 million distinct compounds against purified human ß2AR. Here, we report the discovery of a small-molecule negative allosteric modulator (antagonist), compound 15 [([4-((2S)-3-(((S)-3-(3-bromophenyl)-1-(methylamino)-1-oxopropan-2-yl)amino)-2-(2-cyclohexyl-2-phenylacetamido)-3-oxopropyl)benzamide], exhibiting a unique chemotype and low micromolar affinity for the ß2AR. Binding of 15 to the receptor cooperatively enhances orthosteric inverse agonist binding while negatively modulating binding of orthosteric agonists. Studies with a specific antibody that binds to an intracellular region of the ß2AR suggest that 15 binds in proximity to the G-protein binding site on the cytosolic surface of the ß2AR. In cell-signaling studies, 15 inhibits cAMP production through the ß2AR, but not that mediated by other Gs-coupled receptors. Compound 15 also similarly inhibits ß-arrestin recruitment to the activated ß2AR. This study presents an allosteric small-molecule ligand for the ß2AR and introduces a broadly applicable method for screening DNA-encoded small-molecule libraries against purified GPCR targets. Importantly, such an approach could facilitate the discovery of GPCR drugs with tailored allosteric effects.

Metabolic reprogramming is required for antibody production that is suppressed in anergic but exaggerated in chronically BAFF-exposed B cells.

B cell activation leads to proliferation and Ab production that can protect from pathogens or promote autoimmunity. Regulation of cell metabolism is essential to support the demands of lymphocyte growth and effector function and may regulate tolerance. In this study, we tested the regulation and role of glucose uptake and metabolism in the proliferation and Ab production of control, anergic, and autoimmune-prone B cells. Control B cells had a balanced increase in lactate production and oxygen consumption following activation, with proportionally increased glucose transporter Glut1 expression and mitochondrial mass upon either LPS or BCR stimulation. This contrasted with metabolic reprogramming of T cells, which had lower glycolytic flux when resting but disproportionately increased this pathway upon activation. Importantly, tolerance greatly affected B cell metabolic reprogramming. Anergic B cells remained metabolically quiescent, with only a modest increase in glycolysis and oxygen consumption with LPS stimulation. B cells chronically stimulated with elevated BAFF, however, rapidly increased glycolysis and Ab production upon stimulation. Induction of glycolysis was critical for Ab production, as glycolytic inhibition with the pyruvate dehydrogenase kinase inhibitor dichloroacetate sharply suppressed B cell proliferation and Ab secretion in vitro and in vivo. Furthermore, B cell-specific deletion of Glut1 led to reduced B cell numbers and impaired Ab production in vivo. Together, these data show that activated B cells require Glut1-dependent metabolic reprogramming to support proliferation and Ab production that is distinct from T cells and that this glycolytic reprogramming is regulated in tolerance.