Biology subjects

Lefkowitz, R. J.

Publications and source records attributed to Lefkowitz, R. J..

3 recordsLinked to original sources

bioRxiv2024

Small Molecule Modulators of Beta-arrestins

{beta}-arrestins are multifunctional regulators of G protein-coupled receptor (GPCR) signaling, orchestrating diverse downstream signaling events and physiological responses across the vast GPCR superfamily. While GPCR pharmacology has advanced to target orthosteric and allosteric sites, as well as G proteins and GRKs, comparable chemical tools to study {beta}-arrestins remain lacking. Here, we report the discovery of small-molecule inhibitors that selectively target {beta}-arrestins and delineate their mechanism of action through integrated pharmacological, biochemical, biophysical, and structural analyses. These inhibitors disrupt {beta}-arrestin-engagement with agonist-activated GPCRs, impairing desensitization, internalization, and {beta}-arrestin-dependent functions while sparing G protein-receptor coupling. Cryo-EM, MD simulations, and structure-guided mutagenesis reveal that one modulator, Cmpd-5, engages a cryptic pocket formed by the middle, C-, and lariat loops of {beta}-arrestin1--a critical receptor-binding interface--stabilizing a distinct conformation incompatible with GPCR engagement. Together, these findings provide a mechanistic framework for {beta}-arrestin modulation, introducing transducer-targeted strategies to fine-tune GPCR signaling and guide the development of pathway-specific therapeutics.

biochemistry↗

bioRxiv2024

Beta-arrestin 1 mediated Src activation via Src SH3 domain revealed by cryo-electron microscopy

Beta-arrestins ({beta}arrs) are key regulators and transducers of G-protein coupled receptor signaling; however, little is known of how {beta}arrs communicate with their downstream effectors. Here, we report the first structural insights into the fundamental mechanisms driving {beta}arr-mediated signal transduction. Using cryo-electron microscopy, we elucidate how {beta}arr1 recruits and activates the non-receptor tyrosine kinase Src, the first identified signaling partner of {beta}arrs. {beta}arr1 engages Src SH3 through two distinct sites, each employing a different recognition mechanism: a polyproline motif in the N-domain and a non-proline-based interaction in the central crest region. At both sites {beta}arr1 interacts with the aromatic surface of SH3, disrupting the autoinhibited conformation of Src and directly triggering its allosteric activation. This structural evidence establishes {beta}arr1 as an active regulatory protein rather than a passive scaffold and suggests a potentially general mechanism for {beta}arr-mediated signaling across diverse effectors.

biochemistry↗

bioRxiv2024

Molecular insights into G protein specificity and biased agonism at the β2-adrenergic receptor

G protein coupled receptors (GPCRs) exhibit varying degrees of selectivity for different G protein isoforms. Despite the abundant structures of GPCR-G protein complexes, little is known about the mechanism of G protein coupling specificity. The {beta}2-adrenergic receptor is an example of GPCR with high selectivity for Gs, the stimulatory G protein for adenylyl cyclase, and much weaker for the Gi family of G proteins inhibiting adenylyl cyclase. By developing a Gi-biased agonist (LM189), we provide structural and biophysical evidence supporting that distinct conformations at ICL2 and TM6 are required for coupling of the different G protein subtypes Gs and Gi. These results deepen our understanding of G protein specificity and bias and can accelerate the design of ligands that select for preferred signaling pathways.

molecular biology↗