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Selective G Protein Signaling Driven by Substance P–Neurokinin Receptor Dynamics

Harris  et al., Nature Chemical Biology. 2021.

https://www.nature.com/articles/s41589-021-00890-8

Investigators determined the cryogenic-electron microscopy structures of active neurokinin-1 receptor (NK1R) bound to neuropeptide substance P (SP) or the G protein q (Gq)-biased peptide SP6–11. Peptide interactions deep within NK1R are critical for receptor activation. Conversely, interactions between SP and NK1R extracellular loops are required for potent Gs-signaling but not Gq-signaling. Molecular dynamics simulations showed that these superficial contacts restrict SP flexibility. SP6–11, which lacks these interactions, is dynamic while bound to NK1R. Structural dynamics of NK1R agonists therefore depend on interactions with the receptor extracellular loops and regulate G protein signaling selectivity. This data unveils the molecular mechanism of how two stimuli (SP and Neurokinin A) yield distinct G protein signaling at the same G protein-coupled receptor. Supported by ORIP (S10OD021741, S10OD020054) and others.

In Vitro and In Vivo Functions of SARS-CoV-2 Infection-Enhancing and Neutralizing Antibodies

Li et al., Cell. 2021.

https://doi.org/10.1016/j.cell.2021.06.021

Antibody-dependent enhancement of infection is a concern for clinical use of antibodies. Researchers isolated neutralizing antibodies against the receptor-binding domain (RBD) or N-terminal domain (NTD) of SARS-CoV-2 spike from COVID-19 patients. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific binding modes. RBD and NTD antibodies mediated both neutralization and infection enhancement in vitro. However, infusion of these antibodies into mice or macaques resulted in suppression of virus replication, demonstrating that antibody-enhanced infection in vitro does not necessarily predict enhanced infection in vivo. RBD-neutralizing antibodies having cross-reactivity against coronaviruses were protective against SARS-CoV-2, the most potent of which was DH1047. Supported by ORIP (P40OD012217, U42OD021458, S10OD018164), NIAID, NCI, NIGMS, and NIH Common Fund.

Thioesterase Superfamily Member 1 Undergoes Stimulus-Coupled Conformational Reorganization to Regulate Metabolism in Mice

Li et al., Nature Communications. 2021.

https://doi.org/10.1038/s41467-021-23595-x

Thermogenesis is suppressed in brown adipose tissue by thioesterase superfamily member 1 (Them1), a long chain fatty acyl-CoA thioesterase. Them1 is highly upregulated by cold ambient temperature, where it reduces fatty acid availability and limits thermogenesis. Investigators show that Them1 regulates metabolism by undergoing conformational changes in response to β-adrenergic stimulation that alter Them1 intracellular distribution. Them1 forms metabolically active puncta near lipid droplets and mitochondria. Upon stimulation, Them1 is phosphorylated at the N-terminus, inhibiting puncta formation and activity, and resulting in a diffuse intracellular localization. Investigators show that Them1 puncta are biomolecular condensates that are inhibited by phosphorylation. Them1 forms intracellular biomolecular condensates that limit fatty acid oxidation and suppress thermogenesis. When energy is demanded, the condensates are disrupted by phosphorylation to allow for maximal thermogenesis. The stimulus-coupled reorganization of Them1 provides fine-tuning of thermogenesis and energy expenditure. Supported by ORIP (S10OD019988) and others.

Best Practices for Correctly Identifying Coronavirus by Transmission Electron Microscopy

Bullock  et al., Kidney International. 2021.

https://pubmed.ncbi.nlm.nih.gov/33493525/

This paper provides strategies for identifying coronaviruses by transmission electron microscopy in ultrathin sections of tissues or tissue cultures. As illustrated by results in the literature, organ damage may be incorrectly attributed to the presence of virus, since images of coronavirus may resemble subcellular organelles. The paper also references numerous biochemical and imaging techniques to aid an investigator in avoiding pseudo positive identifications. Supported by ORIP (S10OD026776) and others.