We report on a combined activation mechanism for a class B G-protein–coupled receptor (GPCR), the glucagon receptor. By computing the conformational free-energy landscape associated with the ...activation of the receptor–agonist complex and comparing it with that obtained with the ternary complex (receptor–agonist–G protein) we show that the agonist stabilizes the receptor in a preactivated complex, which is then fully activated upon binding of the G protein. The proposed mechanism contrasts with the generally assumed GPCR activation mechanism, which proceeds through an opening of the intracellular region allosterically elicited by the binding of the agonist. The mechanism found here is consistent with electron cryo-microscopy structural data and might be general for class B GPCRs. It also helps us to understand the mode of action of the numerous allosteric antagonists of this important drug target.
Adenosine receptors are involved in many pathological conditions and are thus promising drug targets. However, developing drugs that target this GPCR subfamily is a challenging task. A number of drug ...candidates fail due to lack of selectivity which results in unwanted side effects. The extensive structural similarity of adenosine receptors complicates the design of selective ligands. The problem of selective targeting is a general concern in GPCRs, and in this respect adenosine receptors are a prototypical example. Here we use enhanced sampling simulations to decipher the determinants of selectivity of ligands in A2a and A1 adenosine receptors. Our model shows how small differences in the binding pocket and in the water network around the ligand can be leveraged to achieve selectivity.
A chemoenzymatic cascade process for the sustainable production of pyrroles has been developed. Pyrroles were synthesized by exploiting the previously unexplored aromatizing activity of monoamine ...oxidase enzymes (MAO-N and 6-HDNO). MAO-N/6-HDNO whole cell biocatalysts are able to convert 3-pyrrolines into pyrroles under mild conditions and in high yields. Moreover, MAO-N can work in combination with the ruthenium Grubbs catalyst, leading to the synthesis of pyrroles from diallylamines/-anilines in a one-pot cascade metathesis–aromatization sequence.
G protein-coupled receptors (GPCRs) are a large superfamily of transmembrane proteins found in eukaryotes. They play a crucial role in the transduction of signals across the plasma membrane of cells, ...and are involved in the regulation of a plethora of processes. Due to their function in countless biological pathways they have a primary role in many pathological conditions, and are thus therapeutic targets of great importance. Notwithstanding the growing availability of X-ray and cryo-EM structures and the intense involvement of the scientific community, many gaps are still present in our understanding of the mechanisms of ligand binding, receptor activation and allostery. Computational methods open the possibility for the study of the dynamics of such processes at atomistic resolution, complementing experimental findings. In this work key processes of a number of different GPCRs are explored with the use of computational approaches. Molecular dynamics and enhanced sampling methods are leveraged for sampling rare events of great interest and for the calculation of the associated free energy landscapes. In the first place our study of ligand binding and the selectivity mechanism in adenosine A2a and A1 receptors is reported, elucidating how selectivity arises from an interplay of structural factors. The activation mechanism of glucagon receptor and the coupling with a G protein is then investigated, highlighting the cooperative action of glucagon and G protein in the process. A detailed overview of allosteric antagonism in chemokine receptors is built by mining databases of experimental data and complementing this picture with insights on the dynamics of these receptors. Finally, the performance of TS-PPTIS (Transition State-Partial Path Transition State Sampling), a method for the calculation of kinetic rate constants, is studied for the prediction of ligand binding kinetic rates. The findings of this study add to the understanding of the mechanism of signal transduction through GPCRs, and detail this process from its origin outside the cell to the intracellular medium.
The recent outbreaks of Zika virus (ZIKV) infection worldwide make the discovery of novel antivirals against flaviviruses a research priority. This work describes the identification of novel ...inhibitors of ZIKV through a structure‐based virtual screening approach using the ZIKV NS5‐MTase. A novel series of molecules with a carbazoyl‐aryl‐urea structure has been discovered and a library of analogues has been synthesized. The new compounds inhibit ZIKV MTase with IC50 between 23–48 μM. In addition, carbazoyl‐aryl‐ureas also proved to inhibit ZIKV replication activity at micromolar concentration.
Novel antivirals targeting ZIKA virus: The recent outbreaks of Zika virus (ZIKV) worldwide make the discovery of novel antivirals a priority. Using a structure‐based virtual screening approach we were able to identify and develop a novel series of carbazoyl‐urea derivatives that are able to inhibit the ZIKV NS5‐MTase as well as ZIKV replication at micromolar concentration.
Current therapies for Alzheimer’s disease seek to correct for defective cholinergic transmission by preventing the breakdown of acetylcholine through inhibition of acetylcholinesterase, these however ...have limited clinical efficacy. An alternative approach is to directly activate cholinergic receptors responsible for learning and memory. The M1-muscarinic acetylcholine (M1) receptor is the target of choice but has been hampered by adverse effects. Here we aimed to design the drug properties needed for a well-tolerated M1-agonist with the potential to alleviate cognitive loss by taking a stepwise translational approach from atomic structure, cell/tissue-based assays, evaluation in preclinical species, clinical safety testing, and finally establishing activity in memory centers in humans. Through this approach, we rationally designed the optimal properties, including selectivity and partial agonism, into HTL9936—a potential candidate for the treatment of memory loss in Alzheimer’s disease. More broadly, this demonstrates a strategy for targeting difficult GPCR targets from structure to clinic.
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•Agonist:receptor co-structures inform synthesis of a M1-receptor partial agonist•M1-receptor agonist shows pro-cognitive activity in preclinical models•M1-receptor agonist shows low cholinergic adverse effects in human studies•M1-receptor agonist activates centers of learning and memory in elderly volunteers
A selective M1 receptor agonist, developed using structure-guided synthesis, exhibits pro-cognitive effects in animal models of Alzheimer’s disease and activates brain regions associated with learning and memory in humans.
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