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Abstract Histamine is a biogenic amine that is critical in various physiological and pathophysiological processes, including but not limited to allergic reactions, wakefulness, gastric acid secretion and neurotransmission. Here, we determine 9 cryo-electron microscopy (cryo-EM) structures of the 4 histamine receptors in complex with four different G protein subtypes, with endogenous or synthetic agonists bound. Inside the ligand pocket, we identify key motifs for the recognition of histamine, the distinct binding orientations of histamine and three subpockets that facilitate the design of specific ligands. In addition, we also identify key residues responsible for the selectivity of immethridine. Moreover, we reveal distinct structural features as determinants of Gq vs. Gs or Gs vs. Gi coupling differences among the histamine receptors. Our study provides a structural framework for understanding the ligand recognition and G protein coupling of all 4 histamine receptors, which may facilitate the rational design of ligands targeting these receptors.

Abstract MRGPRX1, a Mas-related GPCR (MRGPR), is a key receptor for itch perception and targeting MRGPRX1 may have potential to treat both chronic itch and pain. Here we report cryo-EM structures of the MRGPRX1-Gi1 and MRGPRX1-Gq trimers in complex with two peptide ligands, BAM8-22 and CNF-Tx2. These structures reveal a shallow orthosteric pocket and its conformational plasticity for sensing multiple different peptidic itch allergens. Distinct from MRGPRX2, MRGPRX1 contains a unique pocket feature at the extracellular ends of TM3 and TM4 to accommodate the peptide C-terminal “RF/RY” motif, which could serve as key mechanisms for peptidic allergen recognition. Below the ligand binding pocket, the G6.48XP6.50F6.51G6.52X(2)F/W6.55 motif is essential for the inward tilting of the upper end of TM6 to induce receptor activation. Moreover, structural features inside the ligand pocket and on the cytoplasmic side of MRGPRX1 are identified as key elements for both Gi and Gq signaling. Collectively, our studies provide structural insights into understanding itch sensation, MRGPRX1 activation, and downstream G protein signaling.

In this work, the authors demonstrate that LLPS of the quaternary USH2 protein complex initiates the formation of stereociliary ankle link condensates, providing insights into the pathogenesis of deafness.

S-nitrosylation can influence many pathophysiological processes. Here the authors show that the coupling efficiency of GNAI2 with CXCR5 is enhanced by S-nitrosylation of GNAI2, leading to Hippo-YAP dysfunction in endothelium, and plays a role in diabetes-accelerated atherosclerosis.

The interaction between a GPCR, such as the vasopressin receptor-2 (V2R), and arrestin depends on the receptors’ phosphorylation pattern. Here authors use FRET and NMR to analyze the phosphorylation patterns of the V2R-arrestin complex and show that phospho-interactions are the key determinants of selective arrestin conformational states and correlated functions.

Characterization of dynamic conformational changes in membrane protein complexes by NMR spectroscopy remains challenging. Here authors report the site-specific incorporation of 4-trimethylsilyl phenylalanine (TMSiPhe) into proteins, which enabled the characterization of multiple conformational states of a phospho-β2 adrenergic receptor/β-arrestin-1 complex in response to different receptor ligands.

Angiotensin II type 1 receptor (AT1R)-mediated acute catecholamine release is modulated by β-arrestin. Here the authors show that β-arrestin-1 recruits the Ca2+channel TRPC3 and the PLCγ to the AT1R-β-arrestin complex, triggering G protein-independent calcium influx and catecholamine secretion.