The Molecular Control of Calcitonin Receptor Signaling

The calcitonin receptor (CTR) is a class B G protein-coupled receptor (GPCR) that responds to the peptide hormone calcitonin (CT). CTs are clinically approved for the treatment of bone diseases. We previously reported a 4.1 Å structure of the activated CTR bound to salmon CT (sCT) and heterotrimeric Gs protein by cryo-electron microscopy (Liang, Y.-L., et al. Phase-plate cryo- EM structure of a class B GPCR-G protein complex. Nature 2017, 546, 118–123). In the current study, we have reprocessed the electron micrographs to yield a 3.3 Å map of the complex. This has allowed us to model extracellular loops (ECLs) 2 and 3, and the peptide N-terminus that previously could not be resolved. We have also performed alanine scanning mutagenesis of ECL1 and the upper segment of transmembrane helix 1 (TM1) and its extension into the receptor extracellular domain (TM1 stalk), with effects on peptide binding and function assessed by cAMP accumulation and ERK1/2 phosphorylation. These data were combined with previously published alanine scanning mutagenesis of ECL2 and ECL3 and the new structural information to provide a comprehensive 3D map of the molecular surface of the CTR that controls binding and signaling of distinct CT and related peptides. The work highlights distinctions in how different, related, class B receptors may be activated. The new mutational data on the TM1 stalk and ECL1 have also provided critical insights into the divergent control of cAMP versus pERK signaling and, collectively with previous mutagenesis data, offer evidence that the conformations linked to these different signaling pathways are, in many ways, mutually exclusive. This study furthers our understanding of the complex nature of signaling elicited by GPCRs and, in particular, that of the therapeutically important class B subfamily

Structure-function studies on proteins involved in DNA damage prevention

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The ABO blood group locus and a chromosome 3 gene cluster associate with SARS-CoV-2 respiratory failure in an Italian-Spanish genome-wide association analysis

[Background] Respiratory failure is a key feature of severe Covid-19 and a critical driver of mortality, but for reasons poorly defined affects less than 10% of SARS-CoV-2 infected patients.[Methods] We included 1,980 patients with Covid-19 respiratory failure at seven centers in the Italian and Spanish epicenters of the SARS-CoV-2 pandemic in Europe (Milan, Monza, Madrid, San Sebastian and Barcelona) for a genome-wide association analysis. After quality control and exclusion of population outliers, 835 patients and 1,255 population-derived controls from Italy, and 775 patients and 950 controls from Spain were included in the final analysis. In total we analyzed 8,582,968 single-nucleotide polymorphisms (SNPs) and conducted a metaanalysis of both case-control panels.[Results] We detected cross-replicating associations with rs11385942 at chromosome 3p21.31 and rs657152 at 9q34, which were genome-wide significant (P<5×10-8) in the meta-analysis of both study panels, odds ratio [OR], 1.77; 95% confidence interval [CI], 1.48 to 2.11; P=1.14×10-10 and OR 1.32 (95% CI, 1.20 to 1.47; P=4.95×10-8), respectively. Among six genes at 3p21.31, SLC6A20 encodes a known interaction partner with angiotensin converting enzyme 2 (ACE2). The association signal at 9q34 was located at the ABO blood group locus and a blood-group-specific analysis showed higher risk for A-positive individuals (OR=1.45, 95% CI, 1.20 to 1.75, P=1.48×10-4) and a protective effect for blood group O (OR=0.65, 95% CI, 0.53 to 0.79, P=1.06×10-5).[Conclusions] We herein report the first robust genetic susceptibility loci for the development of respiratory failure in Covid-19. Identified variants may help guide targeted exploration of severe Covid19 pathophysiology.The IKMB's core facilities received infrastructure support by the Deutsche Forschungsgemeinschaft (DFG) Cluster of Excellence "Precision Medicine in Chronic Inflammation" (PMI, EXC2167). The project also received support through a philanthropic donation by Stein Erik Hagen and Canica AS. L.V. was funded by the Fondazione IRCCS Ca’ Granda «COVID-19 Biobank» research grant. This work was also supported by the Ministero dell’Istruzione, dell’Università e della Ricerca – MIUR project "Dipartimenti di Eccellenza 2018 – 2022" (n° D15D18000410001) to the Department of Medical Sciences, University of Torino. The IKMB authors received financial support from the UKSH Foundation "Gutes Tun!" (special thanks to Alexander Eck, Jenspeter Horst and Jens Scholz) and the German Federal Ministry of Education and Research (BMBF; grant ID 01KI20197). HLA-Typing was performed and supported by the Stefan-MorschStiftung. M.A.H was supported by the Spanish Ministry of Science and Innovation ‘JdC fellowship IJC2018-035131-I.N