Colorectal cancer (CRC) has long been known for its tight association with chronic inflammation, thought to play a key role in tumor onset and malignant progression through the modulation of cancer stemness. However, the underlying molecular and cellular mechanisms are still largely elusive. Here we show that the IL-6/STAT3 inflammatory signaling axis induces the deacetylation of FRA1 at the Lys-116 residue located within its DNA-binding domain. The HDAC6 deacetylase underlies this key modification leading to the increase of FRA1 transcriptional activity, the subsequent transactivation of NANOG expression, and the acquisition of stem-like cellular features. As validated in a large (n = 123) CRC cohort, IL-6 secretion was invariably accompanied by increased FRA1 deacetylation at K116 and an overall increase in its protein levels, coincident with malignant progression and poor prognosis. Of note, combined treatment with the conventional cytotoxic drug 5-FU together with Tubastatin A, a HDAC6-specific inhibitor, resulted in a significant in vivo synergistic inhibitory effect on tumor growth through suppression of CRC stemness. Our results reveal a novel transcriptional and posttranslational regulatory cross-talk between inflammation and stemness signaling pathways that underlie self-renewal and maintenance of CRC stem cells and promote their malignant behavior. Combinatorial treatment aimed at the core regulatory mechanisms downstream of IL-6 may offer a novel promising approach for CRC treatment.

Binding of different ligands to glucocorticoid receptor (GR) may induce different conformational changes and even trigger completely opposite biological functions. To understand the allosteric communication within the GR ligand binding domain, the folding pathway of helix 12 (H12) induced by the binding of the agonist dexamethasone (DEX), antagonist RU486, and modulator AZD9567 are explored by molecular dynamics simulations and Markov state model analysis. The ligands can regulate the volume of the activation function‐2 through the residues Phe737 and Gln738. Without ligand or with agonist binding, H12 swings from inward to outward to visit different folding positions. However, the binding of RU486 or AZD9567 perturbs the structural state, and the passive antagonist state appears more stable. Structure‐based virtual screening and in vitro bioassays are used to discover novel GR ligands that bias the conformation equilibria toward the passive antagonist state. HP‐19 exhibits the best anti‐inflammatory activity (IC50 = 0.041 ± 0.011 µm) in nuclear factor‐kappa B signaling pathway, which is comparable to that of DEX. HP‐19 also does not induce adverse effect‐related transactivation functions of GR. The novel ligands discovered here may serve as promising starting points for the development of GR modulators.

The number of solved G-protein-coupled receptor (GPCR) crystal structures has expanded rapidly, but most GPCR structures remain unsolved. Therefore, computational techniques, such as homology modeling, have been widely used to produce the theoretical structures of various GPCRs for structure-based drug design (SBDD). Due to the low sequence similarity shared by the transmembrane domains of GPCRs, accurate prediction of GPCR structures by homology modeling is quite challenging. In this study, angiotensin II type I receptor (AT1R) was taken as a typical case to assess the reliability of class A GPCR homology models for SBDD. Four homology models of angiotensin II type I receptor (AT1R) at the inactive state were built based on the crystal structures of CXCR4 chemokine receptor, CCR5 chemokine receptor, and δ-opioid receptor, and refined through molecular dynamics (MD) simulations and induced-fit docking, to allow for backbone and side-chain flexibility. Then, the quality of the homology models was assessed relative to the crystal structures in terms of two criteria commonly used in SBDD: prediction accuracy of ligand-binding poses and screening power of docking-based virtual screening. It was found that the crystal structures outperformed the homology models prior to any refinement in both assessments. MD simulations could generally improve the docking results for both the crystal structures and homology models. Moreover, the optimized homology model refined by MD simulations and induced-fit docking even shows a similar performance of the docking assessment to the crystal structures. Our results indicate that it is possible to establish a reliable class A GPCR homology model for SBDD through the refinement by integrating multiple molecular modeling techniques.

Highlights d The lipid A pocket is illustrated in EptA and Ah762 d The MCR-3 inside Linker 59 acts as a facilitator to govern its enzymatic action d The facilitator allows binding of MCR to lipid PE, its first substrate d Linker 59 is a sufficient (rather than prerequisite) element for MCR colistin resistance

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is mainly mediated through the interaction between the spike protein (S-pro) of the virus and the host angiotensin-converting enzyme II (ACE2). The attachment of heparan sulfate (HS) to S-pro is necessary for its binding to ACE2. In this study, the binding process of the receptor-binding domain (RBD) of S-pro to ACE2 was explored by enhanced sampling simulations. The free-energy landscape was characterized to elucidate the binding mechanism of S-pro to ACE2 with and without HS fragment DP4. We found that the stability of the T470-F490 loop and the hydrophobic interactions contributed from F486/Y489 in the T470-F490 loop of S-pro are quite crucial for the binding, which is enhanced by the presence of DP4. Our study provides valuable insights for rational drug design to prevent the invasion of SARS-CoV-2.

As a major drug target for anti-inflammatory therapy, the glucocorticoid receptor (GR) regulates a wide range of physiological processes through transactivation (TA) or transrepression. GR TA is involved in many adverse effects of GR-targeting drugs, and therefore, the discovery of novel GR ligands with lower TA activity and longer residence time is quite urgent. Undoubtedly, understanding the ligand dissociation mechanisms and the structural basis of the TA regulation is crucial for the development of novel GR-targeting drugs. Here, we used random accelerated molecular dynamics (RAMD) and funnel metadynamics (FM) simulations to explore the dissociation mechanisms of 5 classic glucocorticoids and 6 nonsteroidal GR ligands. Multiple ligand dissociation pathways were discovered. The classic glucocorticoids exhibit a strong preference for Path I, and most nonsteroidal ligands tend to dissociate along mixed pathways. We also find that the distinct unbinding preferences for AZD2906 and AZD9567, two representative nonsteroidal ligands with similar scaffolds but different TA activities, are primarily determined by their different polar interactions with the surrounding residues. Notably, the binding of AZD9567 poses a substantial impact on the conformation of the GR homodimer interface, which provides a valuable clue to understand the mechanisms of the TA-related side effects induced by the adjustments of the homodimerization process. These findings are critical for the structure-based rational design of novel GR ligands with more potent anti-inflammatory potency and reduced side effects.

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Voltage-gated sodium channels (VGSCs/Na v s), which control the flow of Na + and affect the generation of action potentials (APs), have been regarded as essential targets for many diseases. The biological and pharmacological functions of VGSCs have been extensively studied and many efforts have been made to discover and design ligands of VGSCs as potential therapies. Here, we summarize the recent and representative studies of VGSCs from the perspective of computer-aided drug design (CADD) and molecular modeling, including the structural biology of VGSCs, virtual screening and drug design toward VGSCs based on CADD, and functional studies using molecular modeling technologies. Furthermore, we conclude the achievements that have been made in the field of VGSCs and discuss the shortcomings found in previous studies. We hope that this review can provide some inspiration and reference for future investigations of VGSCs and drug design. This article is categorized under:Structure and Mechanism > Computational Biochemistry and Biophysicscomputer-aided drug design, molecular dynamic simulation, structural biology, voltage-gated sodium channels | INTRODUCTIONVoltage-gated sodium channels (VGSCs/Na v s) are widely expressed in eukaryotes and prokaryotes, and play especially important roles in the generation and propagation of action potentials (APs). 1,2 Since Hodgkin and Huxley successfully recorded the first Na + -based APs from the giant axons of the squid Loligo, 3,4 researchers came to realize the important role of VGSCs in nerve impulse conduction, which opened a new door for VGSCs studies. To date, 10 subtypes of VGSCs (Na v 1.1-Na v 1.9 and Nax) have been found in mammals, and each subtype has its own unique functions (Table S1). Na v 1.1, Na v 1.2, Na v 1.3, and Na v 1.6 are primarily expressed in the central nervous system (CNS), and associated with many diseases such as epilepsy, migraine, autism, and ataxia. 5 Na v 1.4 is predominantly expressed in skeletal