GXMR-CAR containing distinct GXM-specific single-chain variable fragment (scFv) mediated the cell activation against Cryptococcus spp. And had difference in the strength of tonic signaling

Cryptococcus spp. has a polysaccharide capsule composed of glucuronoxylomannan-GXM, a major virulence factor that can prevent the recognition of fungi by immune cells. Chimeric Antigen Receptor (CAR) redirects T cells to target Cryptococcus spp. as previously demonstrated by a CAR specific to GXM, GXMR-CAR. The current study evaluated the strength of the signal transduction triggered by GXMR-CAR, composed of a distinct antigen-binding domain sourced from a single-chain variable fragment (scFv). GXM-specific scFv derived from mAbs 2H1 and 18B7, 2H1-GXMR-CAR and 18B7-GXMR-CAR, respectively, were designed to express CD8 molecule as hinge/transmembrane, and the costimulatory molecule CD137 (4-1BB) coupled to CD3ζ. The 2H1-GXMR-CAR or 18B7-GXMR-CAR Jurkat cells recognized soluble GXM from C. gattii and C. neoformans, and the levels of IL-2 released by the modified cells did not differ between the GXMR-CAR constructs after exposure to Cryptococcus spp. 18B7-GXMR-CAR triggered tonic signaling was more pronounced in modified Jurkat cells, and a protein kinase inhibitor of the Src family (dasatinib) significantly reduced GXMR-CAR tonic signaling and inhibited cell activation against ligands. 18B7 scFv showed a structural modification of the variable heavy (VH) chain that clarified the difference in the strength of tonic signaling and the level of cell activation between 2H1-GXMR-CAR and 18B7-GXMR-CAR. GXMR-CAR constructs induced T-cell activation against clinical isolates of Cryptococcus spp. and serum from patients with cryptococcosis induced high levels of IL-2, mainly in cells modified with 18B7-GXMR-CAR. Thus, 18B7-GXMR-CAR and 2H1-GXMR-CAR mediated T cell activation against Cryptococcus spp. and 18B7 and 2H1 scFv influenced the strength of tonic signaling.

Structural evolution of an amphibian-specific globin: A computational evolutionary biochemistry approach

Studies on the globin family are continuously revealing insights into the mechanisms of gene and protein evolution. The rise of a new globin gene type in Pelobatoidea and Neobatrachia (Amphibia:Anura) from an α-globin precursor provides the opportunity to investigate the genetic and physical mechanisms underlying the origin of new protein structural and functional properties. This amphibian-specific globin (globin A/GbA) discovered in the heart of Rana catesbeiana is a monomer. As the ancestral oligomeric state of α-globins is a homodimer, we inferred that the ancestral state was lost somewhere in the GbA lineage. Here, we combined computational molecular evolution with structural bioinformatics to determine the extent to which the loss of the homodimeric state is pervasive in the GbA clade. We also characterized the loci of GbA genes in Bufo bufo. We found two GbA clades in Neobatrachia. One was deleted in Ranidae, but retained and expanded to yield a new globin cluster in Bufonidae species. Loss of the ancestral oligomeric state seems to be pervasive in the GbA clade. However, a taxonomic sampling that includes more Pelobatoidea, as well as early Neobatrachia, lineages would be necessary to determine the oligomeric state of the last common ancestor of all GbA. The evidence presented here points out a possible loss of oligomerization in Pelobatoidea GbA as a result of amino acid substitutions that weaken the homodimeric state. In contrast, the loss of oligomerization in both Neobatrachia GbA clades was linked to independent deletions that disrupted many packing contacts at the homodimer interface.

Molecular dynamics simulations of human L-asparaginase1: Insights into structural determinants of enzymatic activity

The l-asparaginase enzyme is used in cancer therapy, mainly acute lymphoid leukemia (ALL). Commercial enzymes (EcASNase2) cause adverse reactions during treatment, such as immunogenicity. A human enzyme could be a non-immunogenic substitute. However, no candidate was found showing efficient kinetic properties. HASNase1 is an l-asparaginase that comes from the N-terminal domain of a protein called 60 kDa-lysophospholipase and its 3D structure has not been resolved. HASNase1 is homologous to EcASNase1 and gpASNase1, and this last one has shown efficient kinetic properties. Homology modeling was used to find the 3D structure of hASNase1, so one could submit it to Molecular Dynamics (MD), in order to understand structural differences that lead to different catalytic efficiency compared to EcASNase2 and gpASNase1. The interaction potential between L-Asn and active site residues showed that the substrate can rotate in the site when Region1 is open. Region1 residues sequence favors deformations and movements as shown in MD. Region2-A is linear in gpASNase1, and it features a helix portion in hASNase1, which leaves the Tyr308 position projected to the active site ratifying its role in catalytic efficiency. Analysis of Lys188 orientation and movement showed the effect of positive cooperativity in hASNase1. It was found that the presence of Asn at the allosteric site helps, not only in Region1 stabilization, but also in Lys188 stabilization for the maintenance of the triad. Despite structural similarities in hASNase1, gpASNase1, and EcASNase2, there are differences in structural determinants that, in addition to allosterism, may explain the different kinetic properties.

Alemtuzumab scFv fragments and CD52 interaction study through molecular dynamics simulation and binding free energy

Specific antibody-antigen recognition is crucial for the immune response. Knowledge of molecular interaction details in the recognition process is fundamental for the rational design of antibodies with improved properties. We used state-of-the-art computer simulation tools to deepen the molecular-level understanding of the interactions between the monoclonal antibody Alemtuzumab and its antigen, the CD52 membrane receptor, of great biotechnological importance. Thus, we seek such responses by modeling the interaction of native and known mutants single-chain fragment variable (scFv) of Alemtuzumab with CD52 inserted in a membrane model to mimic the physiological conditions of antibody-antigen binding. Extensive molecular dynamics simulations of the interaction between Alemtuzumab's scFvs and CD52 promoted greater understanding of the structural and energetic bases, which can be translated into the biological action and affinity of this antibody. The quantification of the scFv-CD52 complexes binding free energy (ΔG_bind) by Molecular Mechanics-Poisson-Boltzmann Surface Area (MM-PBSA) correlated with the experimental binding energies described before. Thus, the mutants D53K, K54D, and K56D resulted in less attractive ΔG_bind, therefore lower scFv-CD52 affinity than the native scFv. On the other hand, K56D and K54D/K56D showed lower binding to CD52. These Results revealed that the model system mimicking an environment close to the physiological with the presence of the CD52 in a membrane model proved essential for this system's study. The present study allowed to unveil the molecular mechanisms involved in antigen-antibody interaction and the effects of mutations. Thus, these mechanisms may be explored in the Alemtuzumab variants' rational design with enhanced properties.

A natural cell-penetrating nanopeptide combined with pentavalent antimonial as experimental therapy against cutaneous leishmaniasis

The inadequacy of available treatments for leishmaniasis has presented up to 40% therapeutic failure. This fact suggests an urgency in the discovery of new drugs or alternative approaches for treating this disease. The objective of this study was to evaluate the antileishmanial activity of combined therapy between crotamine (CTA) from Crotalus durissus terrificus and the pentavalent antimonial Glucantime® (GLU). The assays were in vitro performed measuring the inhibition of Leishmania amazonensis amastigotes, followed by the evaluation of cellular production of cytokines and nitrites. After that, analytical methods were performed in order to characterize the molecules involved in the study by Mass Spectrometry, molecular affinity through an in silico assay and Surface Plasmon Resonance. In vivo experiments with BALB/c mice were performed by analyzing parasitemia, lesion size and immunological mediators. In the in vitro experiments, the pharmacological association improved the inhibition of the amastigotes, modulated the production of cytokines and nitric oxide. The therapy improved the effectiveness of the GLU, demonstrating a decreased parasitemia in the infected tissues. Altogether, the results suggest that the combined approach with CTA and GLU may be a promising alternative for the treatment of cutaneous leishmaniasis.

The role of the quaternary structure in the activation of human L-asparaginase

Human L-asparaginase-like protein 1 (ASRGL1) has hydrolytic activity against L-asparagine and isoaspartyl dipeptides. As an N-terminal nucleophile hydrolase family member, its activation depends on an intramolecular autoprocessing step between G167 and T168. In vitro, autoprocessing reaches only 50% completion, which restrains the activity and hampers the full understanding of the activation process. The ASRGL1 dimer interface plays a critical role in intramolecular processing, and the interactions within oligomers can offer relevant information about autoprocessing. In this work, a fully processed trimeric conformation of ASRGL1 was observed for the first time, and we combined biophysical and structural proteomics assays to characterize trimeric ASRGL1. Our analyses show that oligomerization is critical for autoprocessing, hydrolytic activity and thermal stability. The newest trimeric ASRGL1 conformation enhances protein activity and presents a melting temperature deviation of 4.33 °C in comparison to the monomeric conformation. The interaction of the third monomer in the trimeric conformation is driven by an α-helix comprising residues KVNLARLTLF (227-236).

Mapping of suramin binding sites on the group IIA human secreted phospholipase A2

Suramin is a polysulphonated napthylurea used as an antiprotozoal/anthelminitic drug, which also inhibits a broad range of enzymes. Suramin binding to recombinant human secreted group IIA phospholipase A(2) (hsPLA(2)GIIA) was investigated by molecular dynamics simulations (MD) and isothermal titration calorimetry (ITC). MD indicated two possible bound suramin conformations mediated by hydrophobic and electrostatic interactions with amino-acids in three regions of the protein, namely the active-site and residues located in the N- and C-termini, respectively. All three binding sites are located on the phospholipid membrane recognition surface, suggesting that suramin may inhibit the enzyme, and indeed a 90% reduction in hydrolytic activity was observed in the presence of 100nM suramin. These results correlated with ITC data, which demonstrated 2.7 suramin binding sites on the hsPLA(2)GIIA, and indicates that suramin represents a novel class of phospholipase A(2) inhibitor.

Study of the influence of ethanol on basic fibroblast growth factor structure

The growth of cells is controlled by stimulatory or inhibitory factors. More than twenty different families of polypeptide growth factors have been structurally and functionally characterized. Basic fibroblast growth factor (bFGF) of the fibroblast growth factor family was characterized in 1974 as having proliferative activity for fibroblastic cells. The inhibitory effects of ethanol on cell proliferation result from interference with mitogenic growth factors (e.g., bFGF, EGF and PDGF). In order to better understand the mode of action of bFGF, particularly regarding the influence of ethanol on the biological activity of bFGF, three recombinant bFGF mutants were produced (M6B-bFGF, M1-bFGF and M1Q-bFGF). In the present study, wild bFGF and these mutants were examined by molecular dynamics simulations in systems consisting of a solute molecule in ethanol solution at 298 K and physiological pH over 4.0 ns. The hydrogen bonds, the root mean square deviations and specific radial distribution functions were employed to identify changes in the hydrogen bond structures, in the stability and in the approximation of groups in the different peptides to get some insight into the biological role of specific bFGF regions. The detailed description of the intramolecular hydrogen bonds, hydration, and intermolecular hydrogen bonds taking place in bFGF and its mutants in the presence of ethanol established that the residues belonging to the beta5 and beta9 strands, especially SER-73(beta5), TYR-112(beta9), THR-114(beta9), TYR-115(beta9), and SER-117(beta9), are the regions most affected by the presence of ethanol molecules in solution.