Laporte, S. A. | bioRxiv Science

bioRxiv2025

Tunable Bias Signaling of the Angiotensin II Type 1 Receptor for Inotropy via C-Terminal Peptide Modifications and Allosteric Site Targeting

The angiotensin II (AngII) type 1 receptor (AT1R) is a key prototypical G protein-coupled receptor in cardiovascular regulation. Biased agonists that activate G protein or {beta}-arrestin pathways provide promising therapeutic potential, but the molecular determinants for this signaling bias and its physiological implications remain poorly understood. This study profiles AngII analogs with modifications at the C-terminal Phe8, revealing that analogs 11, 12, and 29a exhibit varying degrees of Gq engagement while maintaining potent {beta}-arrestin recruitment. Notably, 12 enhances left ventricular ejection fraction with minimal pressor responses in normotensive rats, while other analogs with variable Gq activity do not promote inotropy. Molecular modeling indicates that the unique profile of 12 results from its flexible long side chain engaging a deep allosteric pocket within AT1R. This study demonstrates that engineering AngIIs C-terminus enables selective tuning of AT1R signaling to control arterial versus cardiac responses, providing strategies for developing improved cardiovascular therapeutics. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/670122v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@52b49corg.highwire.dtl.DTLVardef@1cf92dcorg.highwire.dtl.DTLVardef@b2c103org.highwire.dtl.DTLVardef@19db799_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2022

Molecular insights into intrinsic transducer-coupling bias in the CXCR4-CXCR7 system

Chemokine receptors constitute an important subfamily of G protein-coupled receptors (GPCRs), and they are critically involved in a broad range of immune response mechanisms. Ligand promiscuity among these receptors makes them an interesting target to explore novel aspects of biased agonism. Here, we comprehensively characterize two chemokine receptors namely, CXCR4 and CXCR7, which share a common chemokine agonist (CXCL12), in terms of their G-protein coupling, {beta}-arrestin ({beta}arr) recruitment, contribution of GRKs, and ERK1/2 MAP kinase activation. We observe that CXCR7 lacks G-protein coupling while maintaining robust {beta}arr recruitment with a major contribution of GRK5/6. On the other hand, CXCR4 displays robust G-protein activation as expected, however, it exhibits significantly reduced {beta}arr-coupling compared to CXCR7 in response to their shared natural agonist, CXCL12. These two receptors induce distinct {beta}arr conformations even when activated by the same agonist, and CXCR7, unlike CXCR4, fails to activate ERK1/2 MAP kinase. We further determine the crystal structure of {beta}arr2 in complex with a carboxyl-terminal phosphopeptide derived from CXCR7, which reveals a smaller interdomain rotation than observed previously for activated {beta}arrs. Importantly, structure-guided cellular experiments reveal a key contribution of a single phosphorylation site in CXCR7 on {beta}arr recruitment and endosomal trafficking. Taken together, our study provides molecular insights into intrinsic bias encoded in the CXCR4-CXCR7 system, and it has broad implications for therapeutically important framework of biased agonism.

biochemistry↗