资源环境科技发展态势分析平台

The beta(1)-adrenoceptor (beta(1)AR) is a G-protein-coupled receptor (GPCR) that couples(1)to the heterotrimeric G protein G(s). G-protein-mediated signalling is terminated by phosphorylation of the C terminus of the receptor by GPCR kinases (GRKs) and by coupling of beta-arrestin 1 (beta arr1, also known as arrestin 2), which displaces G(s)and induces signalling through the MAP kinase pathway(2). The ability of synthetic agonists to induce signalling preferentially through either G proteins or arrestins-known as biased agonism(3)-is important in drug development, because the therapeutic effect may arise from only one signalling cascade, whereas the other pathway may mediate undesirable side effects(4). To understand the molecular basis for arrestin coupling, here we determined the cryo-electron microscopy structure of the beta(1)AR-beta arr1 complex in lipid nanodiscs bound to the biased agonist formoterol(5), and the crystal structure of formoterol-bound beta(1)AR coupled to the G-protein-mimetic nanobody(6)Nb80. beta arr1 couples to beta(1)AR in a manner distinct to that(7)of G(s)coupling to beta(2)AR-the finger loop of beta arr1 occupies a narrower cleft on the intracellular surface, and is closer to transmembrane helix H7 of the receptor when compared with the C-terminal alpha 5 helix of G(s). The conformation of the finger loop in beta arr1 is different from that adopted by the finger loop of visual arrestin when it couples to rhodopsin(8). beta(1)AR coupled to beta arr1 shows considerable differences in structure compared with beta(1)AR coupled to Nb80, including an inward movement of extracellular loop 3 and the cytoplasmic ends of H5 and H6. We observe weakened interactions between formoterol and two serine residues in H5 at the orthosteric binding site of beta(1)AR, and find that formoterol has a lower affinity for the beta(1)AR-beta arr1 complex than for the beta(1)AR-G(s)complex. The structural differences between these complexes of beta(1)AR provide a foundation for the design of small molecules that could bias signalling in the beta-adrenoceptors.

A cryo-electron microscopy structure of the beta 1-adrenoceptor coupled to beta-arrestin 1 and activated by the biased agonist formoterol, as well as the crystal structure of a related formoterol-bound adrenoreceptor, provide insights into biased signalling in these systems.

Respiratory syncytial virus enters cells by binding to cell-surface IGFR1, which activates PKC zeta and induces trafficking of the NCL coreceptor to the RSV particles at the cell surface.

Pneumonia resulting from infection is one of the leading causes of death worldwide. Pulmonary infection by the respiratory syncytial virus (RSV) is a large burden on human health, for which there are few therapeutic options(1). RSV targets ciliated epithelial cells in the airways, but how viruses such as RSV interact with receptors on these cells is not understood. Nucleolin is an entry coreceptor for RSV2 and also mediates the cellular entry of influenza, the parainfluenza virus, some enteroviruses and the bacterium that causes tularaemia(3,4). Here we show a mechanism of RSV entry into cells in which outside-in signalling, involving binding of the prefusion RSV-F glycoprotein with the insulin-like growth factor-1 receptor, triggers the activation of protein kinase C zeta (PKC zeta). This cellular signalling cascade recruits nucleolin from the nuclei of cells to the plasma membrane, where it also binds to RSV-F on virions. We find that inhibiting PKC zeta activation prevents the trafficking of nucleolin to RSV particles on airway organoid cultures, and reduces viral replication and pathology in RSV-infected mice. These findings reveal a mechanism of virus entry in which receptor engagement and signal transduction bring the coreceptor to viral particles at the cell surface, and could form the basis of new therapeutics to treat RSV infection.