Receptor Complex Formation Research Articles

In silico Assessment of Phytochemicals from Selected Plants as Prospective TGF‐β1 Inhibitors for Prostate Cancer Therapy

AbstractTransforming growth factor β1 (TGF‐β) is a cytokine with pleiotropic biological functions. Recently, its signaling pathway has been highlighted for its implicative paradoxical roles in prostate cancer (PCa). Suppressing downstream effects of this pathway by interfering with receptor complex formation through inhibition of the TGF‐β1 leads to its antitumor effects, illuminating the TGF‐β1 as a viable therapeutic target for PCa. Our compound library—established by a literature‐based approach that identified phytochemicals with published evidence against the TGF‐β1—was screened by employing molecular docking, density functional theory (DFT), and molecular dynamic (MD) simulations to identify TGF‐β1 inhibitors. Eight of the 24 phytochemicals docked from our compound library had a good binding affinity (ranging from −11.7 to −10 kcal/mol) to the TGF‐β1 (PDB: 1PY5). The phytochemicals displayed good stability and reactivity as revealed by the DFT analysis and a desirable pharmacokinetic profile. The top four phytochemical complexes with high binding energies maintained stability throughout the 100 ns simulation. Qualitative studies on the drug repurposing attributes of bisindolylmaleimide, flavopiridol, baicalin, and gefitinib as inhibitors of TGF‐β1 are recommended; most importantly, suggest further wet‐lab studies to corroborate these phytochemicals—SB 202190, SB 203580, silymarin, and cryptotanshinone—in TGF‐β1 targeted drug development.

Eupafolin hinders cross-talk between gastric cancer cells and cancer-associated fibroblasts by abrogating the IL18/IL18RAP signaling axis

BackgroundCancer-associated fibroblasts (CAFs) are involved in the progression of gastric cancer (GC) as a critical component of the tumor microenvironment (TME), yet specific interventions remain limited. Natural products hold a promising application prospect in the field of anti-tumor in view of their high activity and ease of binding with biological macromolecules. However, the role of natural products in modulating the cross-talk between CAFs and GC cells has not been fully investigated. PurposeThe aim of this study was to identify a potential therapeutic target in CAFs and then screen for natural small molecule drugs with anti-tumor activity against this target. MethodsIntegrating bioinformatics analysis of public databases and experimental validation of human samples and cell lines to identify a candidate target in CAFs. Molecular docking and biolayer interferometry technique were utilized for screening potential natural small molecule drugs. The efficacy and underlying mechanisms of the candidates were explored in vitro and in vivo through techniques such as lentiviral infection, cell spheroids culture, immunoprecipitation and cells-derived xenografts. ResultsIL18 receptor accessory protein (IL18RAP) was found to be overexpressed in CAFs derived from GC tissues and facilitated the protumor function of CAFs on GC. Based on virtual screening and experimental validation, we identified a natural product, eupafolin, that interfered with IL18 signaling. Phenotyping studies confirmed that the proliferation, spheroids formation and tumorigenesis of GC cells facilitated by CAFs were greatly attenuated by eupafolin both in vitro and in vivo. Mechanistically, eupafolin impeded the formation of IL18 receptor (IL18R) complex by directly binding to IL18RAP, thus blocking IL18-mediated nuclear factor kappa B (NF-κB) activation and reduced the synthesis and secretion of IL6 in CAFs. As a consequence, it inactivated signal transducer and activator of transcription 3 (STAT3) in GC cells. ConclusionThis study provides new evidence that IL18 signaling regulates the cross-talk between GC cells and CAFs. And it highlights a novel pharmacological role of eupafolin in inhibiting IL18 signaling, thereby curbing the development of GC via modulating CAFs.

Computational prediction of protein interactions in single cells by proximity sequencing.

Proximity sequencing (Prox-seq) simultaneously measures gene expression, protein expression and protein complexes on single cells. Using information from dual-antibody binding events, Prox-seq infers surface protein dimers at the single-cell level. Prox-seq provides multi-dimensional phenotyping of single cells in high throughput, and was recently used to track the formation of receptor complexes during cell signaling and discovered a novel interaction between CD9 and CD8 in naïve T cells. The distribution of protein abundance can affect identification of protein complexes in a complicated manner in dual-binding assays like Prox-seq. These effects are difficult to explore with experiments, yet important for accurate quantification of protein complexes. Here, we introduce a physical model of Prox-seq and computationally evaluate several different methods for reducing background noise when quantifying protein complexes. Furthermore, we developed an improved method for analysis of Prox-seq data, which resulted in more accurate and robust quantification of protein complexes. Finally, our Prox-seq model offers a simple way to investigate the behavior of Prox-seq data under various biological conditions and guide users toward selecting the best analysis method for their data.

Copine proteins are required for brassinosteroid signaling in maize and Arabidopsis

Copine proteins are highly conserved and ubiquitously found in eukaryotes, and their indispensable roles in different species were proposed. However, their exact function remains unclear. The phytohormone brassinosteroids (BRs) play vital roles in plant growth, development and environmental responses. A key event in effective BR signaling is the formation of functional BRI1-SERK receptor complex and subsequent transphosphorylation upon ligand binding. Here, we demonstrate that BONZAI (BON) proteins, which are plasma membrane-associated copine proteins, are critical components of BR signaling in both the monocot maize and the dicot Arabidopsis. Biochemical and molecular analyses reveal that BON proteins directly interact with SERK kinases, thereby ensuring effective BRI1-SERK interaction and transphosphorylation. This study advances the knowledge on BR signaling and provides an important target for optimizing valuable agronomic traits, it also opens a way to study steroid hormone signaling and copine proteins of eukaryotes in a broader perspective.

In silico design of sgRNA for CRISPR/Cas9-mediated FaRALF33 gene mutagenesis to decrease the infection process to Colletotrichum acutatum in strawberry

Rapid alkalinization factors (RALFs) are ubiquitous cysteine-rich peptides present in plants. They exert diverse functions as hormonal signals in various processes, including cell growth, root elongation, and fertilization. RALF peptides can also act as negative regulators of the plant immune response, inhibiting the formation of the signal receptor complex for immune activation. In Fragaria × ananassa, silencing of FaRALF33 gene plays a key role in the defense against the fungal pathogen Colletotrichum acutatum. In this study, single-guide RNA (sgRNAs) were designed in silico for clustered regularly interspaced short palindromic repeats/CRISPR-associated (CRISPR/Cas) 9-mediated FaRALF33 gene mutagenesis in F. × ananassa for the reduction of C. acutatum infection. FaRALF33 was compared with homologous RALF33 sequences from other plant species, showing that the amino acid sequence of FaRALF33 presents typical sequences of known RALF peptides in RRILA proteolytic site, in addition to tight clustering presented by FaRALF33 with FvRALF33. The online tool CHOPCHOP provided 73 hits for FaRALF33 gene, selecting two sgRNA sequences for mutagenesis, sgRNA 1 (5’-CGACTCTCCCATCTCTTGGACT-3’) and sgRNA 2 (5’-GCAAGCAACGGCAGCGATCA-3’). The predicted secondary structures of the selected sgRNAs presented efficient structures in targeted mutagenesis. The pCas9-TPC-GFP-2XsgRNA vector for CRISPR/Cas9-mediated FaRALF33 gene mutagenesis was designed in silico with two sgRNA sequences (with Arabidopsis thaliana U6-26 promoters) and a green fluorescent protein marker.

ABP1/ABLs and TMKs form receptor complexes to perceive extracellular auxin and trigger fast phosphorylation responses

ABP1/ABLs and TMKs form receptor complexes to perceive extracellular auxin and trigger fast phosphorylation responses

Molecular Mechanism of Calycosin Inhibited Vascular Calcification.

Vascular calcification (VC) is a pathological condition frequently observed in cardiovascular diseases. Primary factors contributing to VC are osteogenic differentiation of vascular smooth muscle and hydroxyapatite deposition. Targeted autophagy (a lysosome-mediated mechanism for degradation/recycling of unnecessary cellular components) is a useful approach for inhibiting VC and promoting vascular cell health. Calycosin has been shown to alleviate atherosclerosis by enhancing macrophage autophagy, but its therapeutic effect on VC has not been demonstrated. Using an in vitro model (rat thoracic aortic smooth muscle cell line A7r5), we demonstrated effective inhibition of VC using calycosin (the primary flavonoid component of astragalus), based on the enhancement of autophagic flux. Calycosin treatment activated AMPK/mTOR signaling to induce initiation of autophagy and restored mTORC1-dependent autophagosome-lysosome fusion in late-stage autophagy by promoting soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex formation, thereby preventing stoppage of autophagy in calcified cells. Calycosin substantially reduced degrees of both osteogenic differentiation and calcium deposition in our VC cell model by enhancing autophagy. The present findings clarify the mechanism whereby calycosin mitigates autophagy stoppage in calcified smooth muscle cells and provide a basis for effective VC treatment via autophagy enhancement.

ALLOSTERIC SITES AND ALLOSTERIC REGULATORS OF G-PROTEIN-COUPLED RECEPTORS: GRAY CARDINALS OF SIGNAL TRANSDUCTION

Membrane G protein-coupled receptors (GPCRs) are key components of most eukaryotic signaling systems, transducing external signals to intracellular effector proteins. Activation of GPCRs occurs through the specific binding of ligands of different nature to their orthosteric site. However, regulation of the affinity of an orthosteric agonist for the receptor, control of its effectiveness, and selection of the preferentially activated intracellular signaling cascade is carried out using allosteric mechanisms. This is due to the presence in GPCRs of many allosteric sites, which differ in structural and functional organization and topology in the receptor molecule, and are located in all its functional subdomains. The endogenous regulators of these sites are simple ions (Na+, Zn2+, Mg2+, Ca2+, Cl– and others), lipids (cholesterol, phospholipids, steroids), amino acids and their derivatives, polypeptides, as well as signaling proteins that form functionally active complexes with GPCRs (G proteins, β‑arrestins, RAMPs), and autoantibodies to the extracellular regions of GPCRs. Based on pharmacological activity, ligands of allosteric sites of GPCRs are divided into positive, negative or silent modulators of the effects of orthosteric agonists, as well as full and inverse agonists or neutral antagonists, which affect the basal activity of the receptor in the absence of an orthosteric agonist, although combining the properties of a modulator and an agonist is also possible. The multiplicity of allosteric sites and allosteric regulators, complex interactions between them, and the involvement of allosteric mechanisms in the formation of receptor complexes play a key role in fine-tuning the functional activity of signaling cascades, in biased agonism, and predetermine the processes of receptor desensitization and the fate of the receptor complex after hormonal signal transduction. The review summarizes and analyzes current concepts and new trends in the field of studying the allosteric regulation of GPCRs, the localization and functional role of allosteric sites, and their endogenous and synthetic ligands. As an example, synthetic allosteric regulators of the receptors of thyroid-stimulating and luteinizing hormones, as potential drugs for the correction of endocrine disorders, are discussed in detail.

Modulation of Neuron and Astrocyte Dopamine Receptors via Receptor-Receptor Interactions.

Dopamine neurotransmission plays critical roles in regulating complex cognitive and behavioral processes including reward, motivation, reinforcement learning, and movement. Dopamine receptors are classified into five subtypes, widely distributed across the brain, including regions responsible for motor functions and specific areas related to cognitive and emotional functions. Dopamine also acts on astrocytes, which express dopamine receptors as well. The discovery of direct receptor-receptor interactions, leading to the formation of multimeric receptor complexes at the cell membrane and providing the cell decoding apparatus with flexible dynamics in terms of recognition and signal transduction, has expanded the knowledge of the G-protein-coupled receptor-mediated signaling processes. The purpose of this review article is to provide an overview of currently identified receptor complexes containing dopamine receptors and of their modulatory action on dopamine-mediated signaling between neurons and between neurons and astrocytes. Pharmacological possibilities offered by targeting receptor complexes in terms of addressing neuropsychiatric disorders associated with altered dopamine signaling will also be briefly discussed.

Molecular analysis of the type III interferon complex and its applications in protein engineering

Type III interferons (IFNλs) are cytokines with critical roles in the immune system and are attractive therapeutic candidates due to their tissue-specific activity. Despite entering several clinical trials, results have demonstrated limited efficacy and potency, partially attributed to low-affinity protein-protein interactions (PPIs) responsible for receptor complex formation. Subsequently, structural studies of the native IFNλ signaling complexes remain inaccessible. While protein engineering can overcome affinity limitations, tools to investigate low-affinity systems like these remain limited. To provide insights into previous efforts to strengthen the PPIs within this complex, we perform a molecular analysis of the extracellular ternary complexes of IFNλ3 using both computational and experimental approaches. We first use molecular simulations and modeling to quantify differences in PPIs and residue strain fluctuations, generate detailed free energy landscapes, and reveal structural differences between an engineered, high-affinity complex, and a model of the wild-type, low-affinity complex. This analysis illuminates distinct behaviors of these ligands, yielding mechanistic insights into IFNλ complex formation. We then apply these computational techniques in protein engineering and design by utilizing simulation data to identify hotspots of interaction to rationally engineer the native cytokine-receptor complex for increased stability. These simulations are then validated by experimental techniques, showing that a single mutation at a computationally predicted site of interaction between the two receptors increases PPIs and improves complex formation for all IFNλs. This study highlights the power of molecular dynamics simulations for protein engineering and design as applied to the IFNλ family but also presents a potential tool for analysis and engineering of other systems with low-affinity PPIs.

Intrinsic disorder and conformational coexistence in auxin coreceptors

AUXIN/INDOLE 3-ACETIC ACID (Aux/IAA) transcriptional repressor proteins and the TRANSPORT INHIBITOR RESISTANT 1/AUXIN SIGNALING F-BOX (TIR1/AFB) proteins to which they bind act as auxin coreceptors. While the structure of TIR1 has been solved, structural characterization of the regions of the Aux/IAA protein responsible for auxin perception has been complicated by their predicted disorder. Here, we use NMR, CD and molecular dynamics simulation to investigate the N-terminal domains of the Aux/IAA protein IAA17/AXR3. We show that despite the conformational flexibility of the region, a critical W-P bond in the core of the Aux/IAA degron motif occurs at a strikingly high (1:1) ratio of cis to trans isomers, consistent with the requirement of the cis conformer for the formation of the fully-docked receptor complex. We show that the N-terminal half of AXR3 is a mixture of multiple transiently structured conformations with a propensity for two predominant and distinct conformational subpopulations within the overall ensemble. These two states were modeled together with the C-terminal PB1 domain to provide the first complete simulation of an Aux/IAA. Using MD to recreate the assembly of each complex in the presence of auxin, both structural arrangements were shown to engage with the TIR1 receptor, and contact maps from the simulations match closely observations of NMR signal-decreases. Together, our results and approach provide a platform for exploring the functional significance of variation in the Aux/IAA coreceptor family and for understanding the role of intrinsic disorder in auxin signal transduction and other signaling systems.

BAK1 protects the receptor-like kinase BIR2 from SNIPER2a/b-mediated degradation to promote pattern-triggered immunity in Nicotiana benthamiana.

The detection of microbial infections by plants induces the rapid formation of immune receptor complexes at the plasma membrane. However, how this process is controlled to ensure proper immune signaling remains largely unknown. Here, we found that the Nicotiana benthamiana membrane-localized leucine-rich repeat receptor-like kinase BAK1-INTERACTING RLK 2 (NbBIR2) constitutively associates with BRI1-ASSOCIATED RECEPTOR KINASE 1 (NbBAK1) in vivo and in vitro and promotes complex formation with pattern recognition receptors. In addition, NbBIR2 is targeted by 2 RING-type ubiquitin E3 ligases, SNC1-INFLUENCING PLANT E3 LIGASE REVERSE 2a (NbSNIPER2a) and NbSNIPER2b, for ubiquitination and subsequent degradation in planta. NbSNIPER2a and NbSNIPER2b interact with NbBIR2 in vivo and in vitro and are released from NbBIR2 upon treatment with different microbial patterns. Furthermore, accumulation of NbBIR2 in response to microbial patterns is tightly associated with NbBAK1 abundance in N. benthamiana. NbBAK1 acts as a modular protein that stabilizes NbBIR2 by competing with NbSNIPER2a or NbSNIPER2b for association with NbBIR2. Similar to NbBAK1, NbBIR2 positively regulates pattern-triggered immunity and resistance to bacterial and oomycete pathogens in N. benthamiana, whereas NbSNIPER2a and NbSNIPER2b have the opposite effect. Together, these results reveal a feedback regulatory mechanism employed by plants to tailor pattern-triggered immune signaling.

An EPFL peptide signaling pathway promotes stamen elongation via enhancing filament cell proliferation to ensure successful self-pollination in Arabidopsis thaliana.

Proper stamen filament elongation is essential for plant self-pollination and reproduction. Several phytohormones such as jasmonate and gibberellin play important roles in controlling filament elongation, but other endogenous signals involved in this developmental process remain unknown. We report here that three EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family peptides, EPFL4, EPFL5 and EPFL6, act redundantly to promote stamen filament elongation via enhancing filament cell proliferation in Arabidopsis thaliana. Knockout of EPFL4-6 genes led to shortened filaments due to defective filament cell proliferation, resulting in pollination failure and male sterility. Further genetic and biochemical analyses indicated that the ERECTA family and the SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK) family RLKs form receptor complexes to perceive EPFL4-6 peptides and promote filament cell proliferation. Moreover, based on both loss- and gain-of-function genetic analyses, the mitogen-activated protein kinase cascade MKK4/MKK5-MPK6 was shown to function downstream of EPFL4-6 to positively regulate cell proliferation in stamen filaments. Together, this study reveals that an EPFL peptide signaling pathway composed of the EPFL4-6 peptide ligands, the ERECTA-SERK receptor complexes and the downstream MKK4/MKK5-MPK6 cascade promotes stamen filament elongation via enhancing filament cell proliferation to ensure successful self-pollination and normal fertility in Arabidopsis.

Use of NanoBiT and NanoBRET to characterise interleukin-23 receptor dimer formation in living cells.

Interleukin-23 (IL-23) and its receptor are important drug targets for the treatment of auto-inflammatory diseases. IL-23 binds to a receptor complex composed of two single transmembrane spanning proteins IL23R and IL12Rβ1. In this study, we aimed to gain further understanding of how ligand binding induces signalling of IL-23 receptor complexes using the proximity-based techniques of NanoLuc Binary Technology (NanoBiT) and Bioluminescence Resonance Energy Transfer (BRET). To monitor the formation of IL-23 receptor complexes, we developed a split luciferase (NanoBiT) assay whereby heteromerisation of receptor subunits can be measured through luminescence. The affinity of NanoBiT complemented complexes for IL-23 was measured using NanoBRET, and cytokine-induced signal transduction was measured using a phospho-STAT3 AlphaLISA assay. NanoBiT measurements demonstrated that IL-23 receptor complexes formed to an equal degree in the presence and absence of ligand. NanoBRET measurements confirmed that these complexes bound IL-23 with a picomolar binding affinity. Measurement of STAT3 phosphorylation demonstrated that pre-formed IL-23 receptor complexes induced signalling following ligand binding. It was also demonstrated that synthetic ligand-independent signalling could be induced by high affinity (HiBit) but not low affinity (SmBit) NanoBiT crosslinking of the receptor N-terminal domains. These results indicate that receptor complexes form prior to ligand binding and are not sufficient to induce signalling alone. Our findings indicate that IL-23 induces a conformational change in heteromeric receptor complexes, to enable signal transduction. These observations have direct implications for drug discovery efforts to target the IL-23 receptor.

PS-B12-11: FUNCTIONAL VERSATILITY OF (PRO) RENIN RECEPTOR CLARIFIED BY STRUCTURAL AND EVOLUTIONARY ANALYSES

Objective: (Pro)renin receptor [(P)RR] is a single-span membrane protein originally identified as a regulator of the renin-angiotensin-aldosterone system. (P)RR reportedly exerts various functions, including an accessory protein of vacuolar ATPase complex and a component of Wnt receptor complex. The soluble form of (P)RR [s(P)RR] which comprises of most of extracellular domain (ECD) exerts an antidiuretic action. although the versatile functions should be mediated through the interactions between (p)rr ecd and its respective binding partners, the one-to-many bindings has not been fully explained. Here we investigated the binding mode of this receptor by structural and evolutionary analyses using three-dimensional structural models of (P)RR, which were predicted by the AlphaFold2 (AF2) program, a machine learning-based algorithm capable of predicting protein structure to near experimental accuracy. Design and method: Monoclonal antibodies against (P)RR reduce the Wnt/beta-catenin-dependent development of pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic cancer. Antibodies against two (P)RR regions (residues 47–60 and 200–213) located in ECD reduce the proliferation of human PDAC cells in vitro. The spatial distribution of the two regions was examined using human (P)RR AF2 structural models (monomer and dimer). The evolutionary conservation profile and hydrophobicity were mapped on the models. Results: The dimer structure predicted by AF2 shows that (P)RR homodimerizes via ECD, which explains the experimentally proven dimer formation. The 47–60 and 200–213 regions of (P)RR formed a continuous surface patch on the structural model, which comprised evolutionarily conserved hydrophobic residues. The dimer model revealed the presence of two hand-like grooves, with 47–60 and 200–213 regions as its palm and 270–296 region (intrinsically disordered region, IDR) as its fingers. Conclusions: Considering conformational flexibility of IDR allowing for multiple protein interactions, we propose that the grooves may act as a binding interface with Wnt signaling molecules and antibodies against the grooves probably interfere with the formation of Wnt receptor complex due to steric hindrance and direct competition with the binding interface residues. The hydrophobic nature of the grooves may explain why (P)RR shows one-to-many bindings underpinning its functional versatility. This study provides new insights into the binding mode of (P)RR for the first time. s(P)RR is considered a useful biomarker for diseases, including essential hypertension and cancer. Our findings may help explore a new treatment and biomarker testing of human diseases, and contribute to quality of life in a longevity society.

Unveiling the Nanoscale Dynamics of the Exocytic Machinery in Chromaffin Cells with Single-Molecule Imaging.

Neuronal and hormonal communication relies on the exocytic fusion of vesicles containing neurotransmitters and hormones with the plasma membrane. This process is tightly regulated by key protein-protein and protein-lipid interactions and culminates in the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex formation and zippering that promotes vesicular fusion. Located on both sides of the vesicle and the plasma membrane, the zippering of the SNARE complex acts to overcome the energy barrier afforded by the repulsive electrostatic force stemming from apposing two negatively charged phospholipid membranes. Another component opposing the timely organization of the fusion machinery is thermal Brownian energy that tends to homogenize all cellular molecules by constantly switching their motions and directions through short-lived molecular interactions. Much less is known of the mechanisms counteracting these chaotic forces, allowing seamless cellular functions such as exocytic fusion. Super-resolution microscopy techniques such as single-molecule imaging have proven useful to start uncovering these nanoscale mechanisms. Here, we used single-particle tracking photoactivatable localization microscopy (sptPALM) to track syntaxin-1-mEos, a SNARE protein located on the plasma membrane of cultured bovine chromaffin cells. We demonstrate that syntaxin-1-mEos undergoes dramatic change in its mobility in response to secretagogue stimulation leading to increased nanoclustering. These nanoclusters are transient in nature and likely to provide docked vesicles with a molecular environment conducive to exocytic fusion.

Conformational GPCR BRET Sensors Based on Bioorthogonal Labeling of Noncanonical Amino Acids.

Here we describe the application of genetic code expansion and site-specific incorporation of noncanonical amino acids that serve as anchor points for fluorescent labeling to generate bioluminescence resonance energy transfer (BRET)-based conformational sensors. Using a receptor with an N-terminal NanoLuciferase (Nluc) and a fluorescently labeled noncanonical amino acid in the receptor's extracellular part allows to analyze receptor complex formation, dissociation, and conformational rearrangements over time and in living cells. These BRET sensors can be used to investigate ligand-induced intramolecular (cysteine-rich domain [CRD] dynamics), but also intermolecular (dimer dynamics) receptor rearrangements. With the design of BRET conformational sensors based on the minimally invasive bioorthogonal labeling procedure, we describe a method that can be used in a microtiter plate format and can be easily adopted to investigate ligand-induced dynamics in various membrane receptors.

Structure-guided insights into potential function of novel genetic variants in the malaria vaccine candidate PfRh5

The recent stall in the global reduction of malaria deaths has made the development of a highly effective vaccine essential. A major challenge to developing an efficacious vaccine is the extensive diversity of Plasmodium falciparum antigens. While genetic diversity plays a major role in immune evasion and is a barrier to the development of both natural and vaccine-induced protective immunity, it has been under-prioritized in the evaluation of malaria vaccine candidates. This study uses genomic approaches to evaluate genetic diversity in next generation malaria vaccine candidate PfRh5. We used targeted deep amplicon sequencing to identify non-synonymous Single Nucleotide Polymorphisms (SNPs) in PfRh5 (Reticulocyte-Binding Protein Homologue 5) in 189 P. falciparum positive samples from Southern Senegal and identified 74 novel SNPs. We evaluated the population prevalence of these SNPs as well as the frequency in individual samples and found that only a single SNP, C203Y, was present at every site. Many SNPs were unique to the individual sampled, with over 90% of SNPs being found in just one infected individual. In addition to population prevalence, we assessed individual level SNP frequencies which revealed that some SNPs were dominant (frequency of greater than 25% in a polygenomic sample) whereas most were rare, present at 2% or less of total reads mapped to the reference at the given position. Structural modeling uncovered 3 novel SNPs occurring under epitopes bound by inhibitory monoclonal antibodies, potentially impacting immune evasion, while other SNPs were predicted to impact PfRh5 structure or interactions with the receptor or binding partners. Our data demonstrate that PfRh5 exhibits greater genetic diversity than previously described, with the caveat that most of the uncovered SNPs are at a low overall frequency in the individual and prevalence in the population. The structural studies reveal that novel SNPs could have functional implications on PfRh5 receptor binding, complex formation, or immune evasion, supporting continued efforts to validate PfRh5 as an effective malaria vaccine target and development of a PfRh5 vaccine.

Antagonization of OX1 Receptor Potentiates CB2 Receptor Function in Microglia from APPSw/Ind Mice Model.

Microdialysis assays demonstrated a possible role of orexin in the regulation of amyloid beta peptide (Aß) levels in the hippocampal interstitial fluid in the APP transgenic model. CB2R is overexpressed in activated microglia, showing a neuroprotective effect. These two receptors may interact, forming CB2-OX1-Hets and becoming a new target to combat Alzheimer's disease. Aims: Demonstrate the potential role of CB2-OX1-Hets expression and function in microglia from animal models of Alzheimer's disease. Receptor heteromer expression was detected by immunocytochemistry, bioluminescence resonance energy transfer (BRET) and proximity ligation assay (PLA) in transfected HEK-293T cells and microglia primary cultures. Quantitation of signal transduction events in a heterologous system and in microglia cells was performed using the AlphaScreen® SureFire® kit, western blot, the GCaMP6 calcium sensor and the Lance Ultra cAMP kit (PerkinElmer). The formation of CB2-OX1 receptor complexes in transfected HEK-293T cells has been demonstrated. The tetrameric complex is constituted by one CB2R homodimer, one OX1R homodimer and two G proteins, a Gi and a Gq. The use of TAT interfering peptides showed that the CB2-OX1 receptor complex interface is TM4-TM5. At the functional level it has been observed that the OX1R antagonist, SB334867, potentiates the action induced by CB2R agonist JWH133. This effect is observed in transfected HEK-293T cells and microglia, and it is stronger in the Alzheimer's disease (AD) animal model APPSw/Ind where the expression of the complex assessed by the proximity ligation assay indicates an increase in the number of complexes compared to resting microglia. The CB2-OX1 receptor complex is overexpressed in microglia from AD animal models where OX1R antagonists potentiate the neuroprotective actions of CB2R activation. Taken together, these results point to OX1R antagonists as drugs with therapeutic potential to combat AD. Data access statement: Raw data will be provided by the corresponding author upon reasonable requirement.

Lewis glycosphingolipids as critical determinants of TRAIL sensitivity in cancer cells.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cancer cell death and contributes to tumor rejection by cytotoxic lymphocytes in cancer immunosurveillance and immunotherapy. TRAIL and TRAIL receptor agonists have garnered wide popularity as promising agents for cancer therapy. We previously demonstrated that the loss of fucosylation in cancer cells impairs TRAIL sensitivity; however, the precise structures of the fucosylated glycans that regulate TRAIL sensitivity and their carrier molecules remain elusive. Herein, we observed that Lewis glycans among various fucosylated glycans positively regulate TRAIL-induced cell death. Specifically, Lewis glycans on lacto/neolacto glycosphingolipids, but not glycoproteins including TRAIL receptors, enhanced TRAIL-induced formation of the cytosolic caspase 8 complex, without affecting the formation of the membranous receptor complex. Furthermore, type I Lewis glycan expression in colon cancer cell lines and patient-derived cancer organoids was positively correlated with TRAIL sensitivity. These findings provide novel insights into the regulatory mechanism of TRAIL-induced cell death and facilitate the identification of novel predictive biomarkers for TRAIL-related cancer therapies in future.