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.

Mycobacterium tuberculosis suppresses the production of inflammatory cytokines by host cells through the host-mediated ubiquitination of a mycobacterial protein, enhancing the interaction of a host signalling inhibitor with another signalling molecule.

Mycobacterium tuberculosis is an intracellular pathogen that uses several strategies to interfere with the signalling functions of host immune molecules. Many other bacterial pathogens exploit the host ubiquitination system to promote pathogenesis(1,2), but whether this same system modulates the ubiquitination of M. tuberculosis proteins is unknown. Here we report that the host E3 ubiquitin ligase ANAPC2-a core subunit of the anaphase-promoting complex/cyclosome-interacts with the mycobacterial protein Rv0222 and promotes the attachment of lysine-11-linked ubiquitin chains to lysine 76 of Rv0222 in order to suppress the expression of proinflammatory cytokines. Inhibition of ANAPC2 by specific short hairpin RNA abolishes the inhibitory effect of Rv0222 on proinflammatory responses. Moreover, mutation of the ubiquitination site on Rv0222 impairs the inhibition of proinflammatory cytokines by Rv0222 and reduces virulence during infection in mice. Mechanistically, lysine-11-linked ubiquitination of Rv0222 by ANAPC2 facilitates the recruitment of the protein tyrosine phosphatase SHP1 to the adaptor protein TRAF6, preventing the lysine-63-linked ubiquitination and activation of TRAF6. Our findings identify a previously unrecognized mechanism that M. tuberculosis uses to suppress host immunity, and provide insights relevant to the development of effective immunomodulators that target M. tuberculosis.