Potent Antiplasmodial Derivatives of the Antitussive Drug Dextromethorphan Reveal the Ent-Morphinan Pharmacophore of Tazopsine-Type Alkaloids

The alkaloid tazopsine 1 was introduced in the late 2000's as a novel antiplasmodial hit compound active against Plasmodium falciparum hepatic stages, with potential to develop prophylactic drugs based on this novel chemical scaffold. However, the structural determinants of tazopsine 1 bioactivity, together with the exact definition of the pharmacophore, remained elusive, impeding further development. We found that the antitussive drug dextromethorphan (DXM) 3, although lacking the complex pattern of stereospecific functionalization of the natural hit, was harboring significant antiplasmodial activity in vitro despite suboptimal prophylactic activity in a murine model of malaria, which precluded its direct repurposing against malaria. The targeted N-alkylation of nor-DXM 15 delivered a small library of analogues with greatly improved activity over DXM 3 against P. falciparum asexual stages. Amongst these, N-2’-pyrrolylmethyl-nor-DXM 16i showed a 2- to 36-fold superior inhibitory potency compared to tazopsine 1 and DXM 3 against parasite liver and blood stages, with 760 ± 130 nM and 2.1 ± 0.4 µM IC50 values, respectively, as well as liver/blood phase selectivity of 2.8. Furthermore, cpd. 16i showed a 5 to 8-fold increase of activity relatively to DXM 3 against P. falciparum stages I-II and V gametocytes, with 18.5 µM and 13.2 µM IC50 values, respectively. Cpd. 16i can thus be considered a promising novel hit compound against malaria in the ent-morphinan series with putative pan-cycle activity, paving the way for further therapeutic development (e. g., investigation of its prophylactic activity in a mouse model of malaria).

4-Deoxy-l-erythro-5-hexoseulose Uronate (DEH) and DEH Reductase: Key Molecule and Enzyme for the Metabolism and Utilization of Alginate

4-Deoxy-l-erythro-5-hexoseulose uronate (DEH), DEH reductase, and alginate lyase have key roles in the metabolism of alginate, a promising carbon source in brown macroalgae for biorefinery. In contrast to the widely reviewed alginate lyase, DEH and DEH reductase have not been previously reviewed. Here, we summarize the current understanding of DEH and DEH reductase, with emphasis on (i) the non-enzymatic and enzymatic formation and structure of DEH and its reactivity to specific amino groups, (ii) the molecular identification, classification, function, and structure, as well as the structural determinants for coenzyme specificity of DEH reductase, and (iii) the significance of DEH for biorefinery. Improved understanding of this and related fields should lead to the practical utilization of alginate for biorefinery.

Towards an optimal monoclonal antibody with higher binding affinity to the receptor-binding domain of SARS-CoV-2 spike proteins from different variants

A highly efficient and robust multiple scales in silico protocol, consisting of atomistic constant charge Molecular Dynamics (MD), constant-charge coarse-grain (CG) MD and constant-pH CG Monte Carlo (MC), has been used to study the binding affinities, the free energy of complexation of selected antigen-binding fragments of the monoclonal antibody (mAbs) CR3022 (originally derived from SARS-CoV-1 patients almost two decades ago) and 11 SARS-CoV-2 variants including the wild type. CR3022 binds strongly to the receptor-binding domain (RBD) of SARS-CoV-2 spike protein, but chooses a different site rather than the receptor-binding motif (RBM) of RBD, allowing its combined use with other mAbs against new emerging virus variants. Totally 235,000 mAbs structures were generated using the RosettaAntibodyDesign software, resulting in top 10 scored CR3022-RBD complexes with critical mutations and compared to the native one, all having the potential to block virus-host cell interaction. Of these 10 finalists, two candidates were further identified in the CG simulations to be clearly best against all virus variants, and surprisingly, all 10 candidates and the native CR3022 did exhibit a higher affinity for the Omicron variant with its highest number of mutations (15) of them all considered in this study. The multiscale protocol gives us a powerful rational tool to design efficient mAbs. The electrostatic interactions play a crucial role and appear to be controlling the affinity and complex building. Clearly, mAbs carrying a lower net charge show a higher affinity. Structural determinants could be identified in atomistic simulations and their roles are discussed in detail to further hint at a strategy towards designing the best RBD binder. Although the SARS-CoV-2 was specifically targeted in this work, our approach is generally suitable for many diseases and viral and bacterial pathogens, leukemia, cancer, multiple sclerosis, rheumatoid, arthritis, lupus, and more.

Integrative Study of the Structural and Dynamical Properties of a KirBac3.1 Mutant: Functional Implication of a Highly Conserved Tryptophan in the Transmembrane Domain

ATP-sensitive potassium (K-ATP) channels are ubiquitously expressed on the plasma membrane of cells in several organs, including the heart, pancreas, and brain, and they govern a wide range of physiological processes. In pancreatic β-cells, K-ATP channels composed of Kir6.2 and SUR1 play a key role in coupling blood glucose and insulin secretion. A tryptophan residue located at the cytosolic end of the transmembrane helix is highly conserved in eukaryote and prokaryote Kir channels. Any mutation on this amino acid causes a gain of function and neonatal diabetes mellitus. In this study, we have investigated the effect of mutation on this highly conserved residue on a KirBac channel (prokaryotic homolog of mammalian Kir6.2). We provide the crystal structure of the mutant KirBac3.1 W46R (equivalent to W68R in Kir6.2) and its conformational flexibility properties using HDX-MS. In addition, the detailed dynamical view of the mutant during the gating was investigated using the in silico method. Finally, functional assays have been performed. A comparison of important structural determinants for the gating mechanism between the wild type KirBac and the mutant W46R suggests interesting structural and dynamical clues and a mechanism of action of the mutation that leads to the gain of function.

In-work Poverty in Russia: How Determinants Have Changed over the 20 years?

This paper examines the determinants of in-work poverty and estimates the probability of falling into poverty for various groups of the Russian population in 1998 and 2018. Drawing from the representative RLMS HSE cross-sections, we showed that, despite a large-scale reduction in Russian poverty in 1998–2018, the ratio of structural and individual determinants did not change substantially. At the same time, the configuration of structural determinants has changed. In 2018, personal efforts became less crucial in reducing the likelihood of falling into poverty; the job characteristics and settlement inequalities have become eventually prominent. By 2018, women and rural residents were at the highest chance of poverty, although in 1998, men and a predominantly urban population were at risk. The long-term conservation of “bad” jobs in routine labour and the unequal distribution of the gains from de-industrialization between urban and rural areas over the past two decades are seen as the main explanations for the nature of Russian in-work poverty.

Structure-Based Design of an RNase Chimera for Antimicrobial Therapy

Bacterial resistance to antibiotics urges the development of alternative therapies. Based on the structure-function of antimicrobial members of the RNase A superfamily, we have developed a hybrid enzyme. Within this family, RNase 1 exhibits the highest catalytic activity and the lowest cytotoxicity; in contrast, RNase 3 shows the highest bactericidal action, alas with a reduced catalytic activity. Starting from both parental proteins, we designed a first RNase 3/1-v1 chimera. The construct had a catalytic activity much higher than RNase 3, unfortunately without reaching an equivalent antimicrobial activity. Thus, two new versions were created with improved antimicrobial properties. Both of these versions (RNase 3/1-v2 and -v3) incorporated an antimicrobial loop characteristic of RNase 3, while a flexible RNase 1-specific loop was removed in the latest construct. RNase 3/1-v3 acquired both higher antimicrobial and catalytic activities than previous versions, while retaining the structural determinants for interaction with the RNase inhibitor and displaying non-significant cytotoxicity. Following, we tested the constructs’ ability to eradicate macrophage intracellular infection and observed an enhanced ability in both RNase 3/1-v2 and v3. Interestingly, the inhibition of intracellular infection correlates with the variants’ capacity to induce autophagy. We propose RNase 3/1-v3 chimera as a promising lead for applied therapeutics.

Determinants shaping the nanoscale architecture of the mouse rod outer segment

The unique membrane organization of the rod outer segment (ROS), the specialized sensory cilium of rod photoreceptor cells, provides the foundation for phototransduction, the initial step in vision. ROS architecture is characterized by a stack of identically shaped and tightly packed membrane disks loaded with the visual receptor rhodopsin. A wide range of genetic aberrations have been reported to compromise ROS ultrastructure, impairing photoreceptor viability and function. Yet, the structural basis giving rise to the remarkably precise arrangement of ROS membrane stacks and the molecular mechanisms underlying genetically inherited diseases remain elusive. Here, cryo-electron tomography (cryo-ET) performed on native ROS at molecular resolution provides insights into key structural determinants of ROS membrane architecture. Our data confirm the existence of two previously observed molecular connectors/spacers which likely contribute to the nanometer-scale precise stacking of the ROS disks. We further provide evidence that the extreme radius of curvature at the disk rims is enforced by a continuous supramolecular assembly composed of peripherin-2 (PRPH2) and rod outer segment membrane protein 1 (ROM1) oligomers. We suggest that together these molecular assemblies constitute the structural basis of the highly specialized ROS functional architecture. Our Cryo-ET data provide novel quantitative and structural information on the molecular architecture in ROS and substantiate previous results on proposed mechanisms underlying pathologies of certain PRPH2 mutations leading to blindness.

Expanding the understanding of viral tropism by characterizing the N-glycomic profiles of transducible cell lines and tissue types and Characterizing functional receptors that mediate the inhibitory relationship between 4-O-sulfated chondroitin sulfate and neurons

1: Glycosylation plays an important role in facilitating viral transduction by acting as preliminary cell surface receptors. For this reason, the structural determinants in glycans that dictate viral tissue tropism need to be extensively studied to improve the efficacy of gene therapy vectors in basic research and eventually the clinic. Elucidating the dependencies for viral transduction initiation and understanding how these structural nuances of glycans initiate virion specific tropic effects is paramount when considering how to use vectors to improve clinical outcomes for patients suffering from illnesses with few treatment options. The goal of this project was to use MALDI-TOF-MS to provide baseline N-glycan profiles of the cell lines and tissues used to test gene therapy vectors. In doing so these profiles will be valuable to the field by clarifying what structural determinants may influence viral tropism. It was discovered Neu5Ac sialic acid content differs qualitatively amongst the seven cell lines analyzed. These differences may play into why some cell lines such as CHO-K1 and COS-7 can transduce more preferentially with some AAV serotypes like AAV5. In addition, sialic acid differences were also assessed in three tissue types used in transduction assays. Abstract 2: After injury to the CNS, reactive astrocytes form a protective extracellular matrix to isolate damaged tissue. These astrocytes influence the surrounding tissue by upregulating the production of proteoglycans containing chondroitin sulfate. Due to the new cellular environment, chondroitin sulfate (CS) glycosaminoglycan chains are upregulated with predominately 4-O-sulated sulfation patterns. These sulfation patterns are known to inhibit axonal guidance, and ultimately neuronal regeneration. While the inhibitory effect of CS is well known, the mechanism by which these specific sulfation patterns may interact with receptors also known to have inhibitory effects on neuro-regeneration such as protein tyrosine phosphatase σ is unknown. To characterize these interactions reductive amination was used to immobilize these CS chains onto solid beads. Chondroitin sulfate was isolated from the organs of an ARSB null mouse model which lacks the N-acetylgalactosamine-4-sulfatase (arylsulfatase B, ARSB) which is involved in the degradation of glycosaminoglycans (GAGs). Disruption of arylsulfatase B leads to the production of CS chains with 4-O-sulfated non-reducing ends exclusively. Key findings indicate that purified GAG chains retain their ligand specificity after being covalently immobilized onto solid supports, and that these systems can be utilized to characterize the relationship between inhibitory forms of CS and protein tyrosine phosphatase σ.