Abstact

Beta-arrestins (betaarrs) are key regulators and transducers of G-protein coupled receptor signaling; however, little is known of how betaarrs communicate with their downstream effectors. Here, we delineate structural mechanisms underlying betaarr-mediated signal transduction. Using cryo-electron microscopy, we elucidate how betaarr1 recruits and activates the non-receptor tyrosine kinase Src, a well-established signaling partner of betaarrs. betaarr1 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 betaarr1 interacts with the aromatic surface of SH3, disrupting the autoinhibited conformation of Src and directly triggering its allosteric activation. This structural evidence establishes betaarr1 as an active regulatory protein rather than a passive scaffold and suggests a potentially general mechanism for betaarr-mediated signaling across diverse effectors.