Regulatory Properties Research Articles

Improving Enhancer Identification with a Multi-Classifier Stacked Ensemble Model

Enhancers are DNA regions that are responsible for controlling the expression of genes. Enhancers are usually found upstream or downstream of a gene, or even inside a gene’s intron region, but are normally located at a distant location from the genes they control. By integrating experimental and computational approaches, it is possible to uncover enhancers within DNA sequences, which possess regulatory properties. Experimental techniques such as ChIP-seq and ATAC-seq can identify genomic regions that are associated with transcription factors or accessible to regulatory proteins. On the other hand, computational techniques can predict enhancers based on sequence features and epigenetic modifications. In our study, we have developed a multi-classifier stacked ensemble (MCSE-enhancer) model that can accurately identify enhancers. We utilized feature descriptors from various physiochemical properties as input for our six baseline classifiers and built a stacked classifier, which outperformed previous enhancer classification techniques in terms of accuracy, specificity, sensitivity, and Mathew’s correlation coefficient. Our model achieved an accuracy of 81.5%, representing a 2–3% improvement over existing models.

Plants of the Rubiaceae Family with Effect on Metabolic Syndrome: Constituents, Pharmacology, and Molecular Targets.

Metabolic syndrome (MetS) predisposes individuals to chronic non-communicable diseases (NCDs) like type 2 diabetes (T2D), non-alcoholic fatty liver disease, atherosclerosis, and cardiovascular disorders caused by systemic inflammation, intestinal dysbiosis, and diminished antioxidant ability, leading to oxidative stress and compromised insulin sensitivity across vital organs. NCDs present a global health challenge characterized by lengthy and costly pharmacological treatments. Complementary and alternative medicine using herbal therapies has gained popularity. Approximately 350,000 plant species are considered medicinal, with 80% of the world's population opting for traditional remedies; however, only 21,000 plants are scientifically confirmed by the WHO. The Rubiaceae family is promissory for preventing and treating MetS and associated NCDs due to its rich content of metabolites renowned for their antioxidative, anti-inflammatory, and metabolic regulatory properties. These compounds influence transcription factors and mitigate chronic low-grade inflammation, liver lipotoxicity, oxidative stress, and insulin resistance, making them a cost-effective non-pharmacological approach for MetS prevention and treatment. This review aims to collect and update data that validate the traditional uses of the Rubiaceae family for treating MetS and associated NCDs from experimental models and human subjects, highlighting the mechanisms through which their extracts and metabolites modulate glucose and lipid metabolism at the molecular, biochemical, and physiological levels.

Deciphering Evolutionary Trajectories of Lactate Dehydrogenases Provides New Insights into Allostery.

Lactate dehydrogenase (LDH, EC.1.1.127) is an important enzyme engaged in the anaerobic metabolism of cells, catalyzing the conversion of pyruvate to lactate and NADH to NAD+. LDH is a relevant enzyme to investigate structure-function relationships. The present work provides the missing link in our understanding of the evolution of LDHs. This allows to explain (i) the various evolutionary origins of LDHs in eukaryotic cells and their further diversification and (ii) subtle phenotypic modifications with respect to their regulation capacity. We identified a group of cyanobacterial LDHs displaying eukaryotic-like LDH sequence features. The biochemical and structural characterization of Cyanobacterium aponinum LDH, taken as representative, unexpectedly revealed that it displays homotropic and heterotropic activation, typical of an allosteric enzyme, whereas it harbors a long N-terminal extension, a structural feature considered responsible for the lack of allosteric capacity in eukaryotic LDHs. Its crystallographic structure was solved in 2 different configurations typical of the R-active and T-inactive states encountered in allosteric LDHs. Structural comparisons coupled with our evolutionary analyses helped to identify 2 amino acid positions that could have had a major role in the attenuation and extinction of the allosteric activation in eukaryotic LDHs rather than the presence of the N-terminal extension. We tested this hypothesis by site-directed mutagenesis. The resulting C. aponinum LDH mutants displayed reduced allosteric capacity mimicking those encountered in plants and human LDHs. This study provides a new evolutionary scenario of LDHs that unifies descriptions of regulatory properties with structural and mutational patterns of these important enzymes.

A PINK1 input threshold arises from positive feedback in the PINK1/Parkin mitophagy decision circuit

Mechanisms that prevent accidental activation of the PINK1/Parkin mitophagy circuit on healthy mitochondria are poorly understood. On the surface of damaged mitochondria, PINK1 accumulates and acts as the input signal to a positive feedback loop of Parkin recruitment, which in turn promotes mitochondrial degradation via mitophagy. However, PINK1 is also present on healthy mitochondria, where it could errantly recruit Parkin and thereby activate this positive feedback loop. Here, we explore emergent properties of the PINK1/Parkin circuit by quantifying the relationship between mitochondrial PINK1 concentrations and Parkin recruitment dynamics. We find that Parkin is recruited to mitochondria only if PINK1 levels exceed a threshold and then only after a delay that is inversely proportional to PINK1 levels. Furthermore, these two regulatory properties arise from the input-coupled positive feedback topology of the PINK1/Parkin circuit. These results outline an intrinsic mechanism by which the PINK1/Parkin circuit can avoid errant activation on healthy mitochondria.

MODIFICATION OF NEURAL INTERACTIONS AND FUNCTIONAL ACTIVITY OF MEDIATOR SYSTEMS UNDER CONDITIONS OF METABOLIC SYNDROME

The review examines the peculiarities of mediator systems under the conditions of metabolic syndrome. The processes of oxidative stress that occur in adipose tissue are described and can be caused not only by an increase in ROS production, but also by a decrease in the antioxidant protection of adipocytes. Features of the eff ects of antioxidant enzymes are shown, which creates prerequisites for further study of their activity in various tissues against the background of metabolic disorders characteristic of metabolic syndrome. Convincing evidence is provided that functional changes in the expression, activity, and regulatory properties of neuronal NO synthase play a key role among the molecular causes of MS. Understanding the molecular basis of the functioning of the signifi cant components of the NO cycle, the patterns of their changes, the relationship between this cycle and oxidative and nitrosative stress will allow in the future to develop methods of more eff ective diagnosis, treatment and prevention of metabolic syndrome.

FCRL1 immunoregulation in B cell development and malignancy.

Immunotherapeutic targeting of surface regulatory proteins and pharmacologic inhibition of critical signaling pathways has dramatically shifted our approach to the care of individuals with B cell malignancies. This evolution in therapy reflects the central role of the B cell receptor (BCR) signaling complex and its co-receptors in the pathogenesis of B lineage leukemias and lymphomas. Members of the Fc receptor-like gene family (FCRL1-6) encode cell surface receptors with complex tyrosine-based regulation that are preferentially expressed by B cells. Among them, FCRL1 expression peaks on naïve and memory B cells and is unique in terms of its intracellular co-activation potential. Recent studies in human and mouse models indicate that FCRL1 contributes to the formation of the BCR signalosome, modulates B cell signaling, and promotes humoral responses. Progress in understanding its regulatory properties, along with evidence for its over-expression by mature B cell leukemias and lymphomas, collectively imply important yet unmet opportunities for FCRL1 in B cell development and transformation. Here we review recent advances in FCRL1 biology and highlight its emerging significance as a promising biomarker and therapeutic target in B cell lymphoproliferative disorders.

Celastrol attenuates human parvovirus B19 NS1‑induced NLRP3 inflammasome activation in macrophages.

Human parvovirus B19 (B19V) has been strongly associated with a variety of inflammatory disorders, such as rheumatoid arthritis (RA), inflammatory bowel disease and systemic lupus erythematosus. Non‑structural protein 1 (NS1) of B19V has been demonstrated to play essential roles in the pathological processes of B19V infection due to its regulatory properties on inflammatory cytokines. Celastrol, a quinone methide isolated from Tripterygiumwilfordii, has displayed substantial potential in treating inflammatory diseases, such as psoriasis and RA. However, little is known about the effects of celastrol on B19V NS1‑induced inflammation. Therefore, cell viability assay, migration assay, phagocytosis analysis, zymography assay, ELISA and immunoblotting were conducted to verify the influences of celastrol on macrophages. The present study reported the attenuating effects of celastrol on B19V NS1‑induced inflammatory responses in macrophages derived from human acute monocytic leukemia cell lines, U937 and THP‑1. Although the migration was not significantly decreased by celastrol in both U937 and THP‑1 macrophages, significantly decreased viability, migration and phagocytosis were detected in both B19V NS1‑activated U937 and THP‑1 macrophages in the presence of celastrol. Additionally, celastrol significantly decreased MMP‑9 activity and the levels of inflammatory cytokines, including IL‑6, TNF‑α and IL‑1β, in B19V NS1‑activated U937 and THP‑1 cells. Notably, significantly decreased levels of NLR family pyrin domain‑containing 3, apoptosis‑associated speck‑like, caspase‑1 and IL‑18 proteins were observed in both B19V NS1‑activated U937 and THP‑1 cells in the presence of celastrol, indicating the involvement of the inflammasome pathway. To the best of our knowledge, the present study is the first to report on the attenuating effects of celastrol on B19V NS1‑induced inflammatory responses in macrophages, suggesting a therapeutic role for celastrol in B19V NS1‑related inflammatory diseases.

Titanium Carbide MXene Quantum Dots-Modified Hydroxyapatite Hollow Microspheres as pH/Near-Infrared Dual-Response Drug Carriers.

Titanium carbide MXene quantum dots (MQDs) possess intrinsic regulatory properties and selective toxicity to cancer cells. Here, MDQs were selected for the modification of hydroxyapatite (HA) microspheres, and MXene quantum dots-modified hydroxyapatite (MQDs-HA) hollow microspheres with controllable shapes and sizes were prepared as bone drug carriers. The results show that the prepared MQDs-HA hollow microspheres had a large BET surface area (231.2 m2/g), good fluorescence, and low toxicity. In addition, MQDs-HA showed a mild storage-release behavior and good responsiveness of pH and near-infrared (NIR). Thus, the MQDs-HA hollow microspheres have broad application prospects in the field of drug delivery and photothermal therapy.

A switchable ionic diode membrane enabled by sub-3 nm covalent organic framework channels

Various efforts have been made to mimic the regulatory properties of biological channels that exist in cell membranes of living organisms. Such ion channels are able to tune electric signals in response to changes in surrounding environments (e.g., pH or ions). Here, we report the design and fabrication of a novel pH-switchable ionic diode membrane (IDM), TFP-EB COF@PET, composed of a thin layer of sub-3 nm covalent organic framework (COF) channels and a polyethylene terephthalate (PET) membrane having conical nanochannels with tip size of 20–40 nm. The designed IDM is found to exhibit ion current rectification (ICR) over a wide range of electrolyte concentrations, attributable to its structural and charge asymmetries. Interestingly, the TFP-EB COF@PET can exhibit pH-switchable ion transport behaviors even though the surface charge natures of TFP-EB COF and PET channels remain unchanged. The mechanisms for the pH-switchable ICR properties are proposed to explain the inversion phenomenon. This work highlights the pH-switchable ionic transport properties of the sub-3 nm-scale COF-based IDM, as well as its potential for long-term operation under high salinity conditions.

Reactive Sulfur Species in human diseases.

Reactive sulfur species (RSS) have been recently recognized as redox molecules no less important than reactive oxygen or nitrogen species. They possess regulatory and protective properties and are involved in various metabolic processes thereby contributing to the maintenance of human health. It has been documented that many disorders, including neurological, cardiovascular and respiratory diseases, diabetes mellitus and cancer are related to the disruption of RSS homeostasis. There is still a growing interest in the role of RSS in human diseases. Since a decrease in H2S or other RSS has been reported in many disorders, safe and efficient RSS donors have been developed and tested under in vitro conditions or on animal models. Cardiovascular diseases and diabetes mellitus are currently the most common chronic diseases worldwide due to stressful and unhealthy lifestyles. In addition, because of high prevalence and aging of the population, neurological disorders including Parkinson's disease and Alzheimer's disease as well as respiratory diseases are a formidable challenge for health care systems. From this point of view, the knowledge of the role of RSS in these disorders and RSS modulation options are important and could be useful in therapeutic strategies. Improvement and standardization of analytical methods used for RSS estimation are crucial for the use RSS as diagnostic biomarkers. Finding good, safe RSS donors applicable for therapeutic purposes could be useful as primary or adjunctive therapy in many common diseases.

Adipose-Derived Mesenchymal Stromal Cells Co-Cultured with Primary Mixed Glia to Reduce Prion-Induced Inflammation.

Mesenchymal stromal cells (MSCs) are potent regulators of inflammation through the production of anti-inflammatory cytokines, chemokines, and growth factors. These cells show an ability to regulate neuroinflammation in the context of neurodegenerative diseases such as prion disease and other protein misfolding disorders. Prion diseases can be sporadic, acquired, or genetic; they can result from the misfolding and aggregation of the prion protein in the brain. These diseases are invariably fatal, with no available treatments. One of the earliest signs of disease is the activation of astrocytes and microglia and associated inflammation, which occurs prior to detectable prion aggregation and neuronal loss; thus, the anti-inflammatory and regulatory properties of MSCs can be harvested to treat astrogliosis in prion disease. Recently, we showed that adipose-derived MSCs (AdMSCs) co-cultured with BV2 cells or primary mixed glia reduce prion-induced inflammation through paracrine signaling. This paper describes a reliable treatment using stimulated AdMSCs to decrease prion-induced inflammation. A heterozygous population of AdMSCs can easily be isolated from murine adipose tissue and expanded in culture. Stimulating these cells with inflammatory cytokines enhances their ability to both migrate toward prion-infected brain homogenate and produce anti-inflammatory modulators in response. Together, these techniques can be used to investigate the therapeutic potential of MSCs on prion infection and can be adapted for other protein misfolding and neuroinflammatory diseases.

Novel Mutation Glu98Lys in Cardiac Tropomyosin Alters Its Structure and Impairs Myocardial Relaxation.

We characterized a novel genetic variant c.292G > A (p.E98K) in the TPM1 gene encoding cardiac tropomyosin 1.1 isoform (Tpm1.1), found in a proband with a phenotype of complex cardiomyopathy with conduction dysfunction and slow progressive neuromuscular involvement. To understand the molecular mechanism by which this mutation impairs cardiac function, we produced recombinant Tpm1.1 carrying an E98K substitution and studied how this substitution affects the structure of the Tpm1.1 molecule and its functional properties. The results showed that the E98K substitution in the N-terminal part of the Tpm molecule significantly destabilizes the C-terminal part of Tpm, thus indicating a long-distance destabilizing effect of the substitution on the Tpm coiled-coil structure. The E98K substitution did not noticeably affect Tpm's affinity for F-actin but significantly impaired Tpm's regulatory properties. It increased the Ca2+ sensitivity of the sliding velocity of regulated thin filaments over cardiac myosin in an in vitro motility assay and caused an incomplete block of the thin filament sliding at low Ca2+ concentrations. The incomplete motility block in the absence of Ca2+ can be explained by the loosening of the Tpm interaction with troponin I (TnI), thus increasing Tpm mobility on the surface of an actin filament that partially unlocks the myosin binding sites. This hypothesis is supported by the molecular dynamics (MD) simulation that showed that the E98 Tpm residue is involved in hydrogen bonding with the C-terminal part of TnI. Thus, the results allowed us to explain the mechanism by which the E98K Tpm mutation impairs sarcomeric function and myocardial relaxation.

San Jie Tong Mai Fang Protects Against Atherosclerosis Progression by Regulating Macroautophagy through the PI3K/AKT/mTOR Signaling Pathway.

Many studies have confirmed that macrophage autophagy injury negatively impacts the pathogenesis of atherosclerosis (AS). Meanwhile, the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway affects AS progression by regulating macrophage autophagy. We previously reported that the herbal formula San Jie Tong Mai Fang (SJTMF) elicits lipid regulatory and anti-inflammatory properties. Hence, the current study used an ApoE -/- high-fat diet-fed mouse model to determine whether SJTMF elicits protective effects against AS progression by means of the regulation of macrophage autophagy through the PI3K/AKT/mTOR signaling pathway. Our results show that SJTMF reduced the number of atherosclerotic plaques, foam cell formation, and intimal thickness in mouse aorta. In addition, SJTMF improved blood lipid metabolism and inflammatory levels in mice. We also observed that SJTMF caused macrophages to be polarized toward the M2 phenotype through the inhibition of the PI3K/AKT/mTOR signaling pathway. In addition, the abundances of LC3-II/I and beclin1 proteins-key autophagy molecules-were increased, whereas that of p62 was decreased, resulting in the promotion of macrophage autophagy. Taken together, these findings indicate that SJTMF may regulate the polarization of macrophages by inhibiting the PI3K/AKT/mTOR signaling pathway, thereby reducing atherosclerotic plaque damage in ApoE -/- mice, thereby promoting macrophage autophagy and eliciting a significant antiarteriosclerosis effect. Hence, SJTMF may represent a promising new candidate drug for the treatment of AS.

Modification of the Properties of Extracellular Matrix of Senescent Mesenchymal Stem Cells.

Cell senescence leads to changes in the secretory activity of mesenchymal stem cells (MSC), including proteins of extracellular matrix (ECM). Here we studied the regulatory properties of ECM of senescent MSC in a model with endothelial cells (EC). EC were seeded onto a decellularized extracellular matrix of senescent MSC. Changes in cell morphology and a decrease in cell growth were observed. In addition, increased production of inflammatory chemokines MCP-1 and GROα and reduced synthesis of proangiogenic growth factor FGF-2 were revealed. Analysis of ECM showed quantitative and qualitative changes, including fibronectin layer morphology, total protein content, and concentration of deposited growth factors such as VEGF. Thus, our work demonstrates that senescence of MSC can lead to modification of the effects of their ECM on EC activity.

ApoE expression in macrophages communicates immunometabolic signaling that controls hyperlipidemia-driven hematopoiesis & inflammation via extracellular vesicles.

While apolipoprotein E (apoE) expression by myeloid cells is recognized to control inflammation, whether such benefits can be communicated via extracellular vesicles is not known. Through the study of extracellular vesicles produced by macrophages derived from the bone marrow of Wildtype (WT-BMDM-EV) and ApoE deficient (EKO-BMDM-EV) mice, we uncovered a critical role for apoE expression in regulating their cell signaling properties. WT-BMDM-EV communicated anti-inflammatory properties to recipient myeloid cells by increasing cellular levels of apoE and miR-146a-5p, that reduced NF-κB signalling. They also downregulated cellular levels of miR-142a-3p, resulting in increased levels of its target carnitine palmitoyl transferase 1A (CPT1A) which improved fatty acid oxidation (FAO) and oxidative phosphorylation (OxPHOS) in recipient cells. Such favorable metabolic polarization enhanced cell-surface MerTK levels and the phagocytic uptake of apoptotic cells. In contrast, EKO-BMDM-EV exerted opposite effects by reducing cellular levels of apoE and miR-146a-5p, which increased NF-κB-driven GLUT1-mediated glucose uptake, aerobic glycolysis, and oxidative stress. Furthermore, EKO-BMDM-EV increased cellular miR-142a-3p levels, which reduced CPT1A levels and impaired FAO and OxPHOS in recipient myeloid cells. When cultured with naïve CD4+ T lymphocytes, EKO-BMDM-EV drove their activation and proliferation, and fostered their transition to a Th1 phenotype. While infusions of WT-BMDM-EV into hyperlipidemic mice resolved inflammation, infusions of EKO-BMDM-EV increased hematopoiesis and drove inflammatory responses in myeloid cells and T lymphocytes. ApoE-dependent immunometabolic signaling by macrophage extracellular vesicles was dependent on transcriptional axes controlled by miR-146a-5p and miR-142a-3p that could be reproduced by infusing miR-146a mimics & miR-142a antagonists into hyperlipidemic apoE-deficient mice. Together, our findings unveil a novel property for apoE expression in macrophages that modulates the immunometabolic regulatory properties of their secreted extracellular vesicles.

Human granzyme B regulatory B cells prevent effector CD4+CD25- T cell proliferation through a mechanism dependent from lymphotoxin alpha.

Human Granzyme B (GZMB) regulatory B cells (Bregs) have suppressive properties on CD4+ effector T cells by a mechanism partially dependent on GZMB. Moreover, these cells may be easily induced in vitro making them interesting for cell therapy. We characterized this population of in vitro induced GZMB+Bregs using single cell transcriptomics. To investigate their regulatory properties, Bregs or total B cells were also co-cultured with T cells and scRNAseq was used to identify receptor ligand interactions and to reveal gene expression changes in the T cells. We find that Bregs exhibit a unique set of 149 genes differentially expressed and which are implicated in proliferation, apoptosis, metabolism, and altered antigen presentation capacity consistent with their differentiated B cells profile. Notably, Bregs induced a strong inhibition of T cell genes associated to proliferation, activation, inflammation and apoptosis compared to total B cells. We identified and validated 5 receptor/ligand interactions between Bregs and T cells. Functional analysis using specific inhibitors was used to test their suppressive properties and we identified Lymphotoxin alpha (LTA) as a new and potent Breg ligand implicated in Breg suppressive properties. We report for the first time for a role of LTA in GZMB+Bregs as an enhancer of GZMB expression, and involved in the suppressive properties of GZMB+Bregs in human. The exact mechanism of LTA/GZMB function in this specific subset of Bregs remains to be determined.

Dual function of glucocorticoid hormones in the body and using this duality for preventing complications of glucocorticoid therapy

Glucocorticoid preparations are used in all areas of medicine for more than 70 years as the most effective anti-inflammatory drugs possessing also anti-allergic and immunosuppressive actions. However, the use of these preparations, unique in the combination and expression of therapeutic properties, is associated with nearly inevitable serious adverse effects. The complications of glucocorticoid therapy are caused by the duality of glucocorticoid hormone functions. Glucocorticoid hormones in the body act: · As the most universal regulators of virtually all metabolic and physiological processes and · As hormones mainly responsible for the organism behavior under stress conditions. In clinical practice, glucocorticoid preparations are used mainly as stress-responsible agents, and their regulatory activities are neglected, but they are manifested inevitably as complications. To prevent these complications, it is necessary to follow the regulatory properties of glucocorticoid preparations which are realized through regulation of activities of many enzymes. The hepatic tyrosine amino transferase seems to be, possibly, the best example of the regulatory activity of glucocorticoids. Based on the literature data and results of the author’s studies, it is proposed to use blood level of tyrosine as a promising laboratory parameter for monitoring glucocorticoid therapy.

Metabolic control analysis as a strategy to identify therapeutic targets, the case of cancer glycolysis

The use of kinetic modeling and metabolic control analysis (MCA) to identify possible therapeutic targets and to investigate the controlling and regulatory mechanisms in cancer glycolysis is here reviewed. The glycolytic pathway has been considered a target to decrease cancer cell growth; however, its occurrence in normal cells makes it difficult to design therapeutic strategies that target this pathway in pathological cells. Notwithstanding, the over-expression of all enzymes and transporters, as well as the expression of isoenzymes with different kinetic and regulatory properties in cancer cells, suggested a different distribution of the control of glycolytic flux than that observed in normal cells. Kinetic models of glycolysis are constructed with enzyme kinetics experimental data, validated with the steady-state metabolite concentrations and glycolytic fluxes; applying MCA, permitted us to identify the steps with the highest control of glycolysis in cancer cells, but low control in normal cells. The cancer glycolysis main controlling steps under several metabolic conditions were: glucose transport, hexokinase and hexose-6-phosphate isomerase (HPI); whereas in normal cells were: the first two and phosphofructokinase-1. HPI is the best therapeutic target because it exerts high control in cancer glycolytic flux, but not in normal cells. Furthermore, kinetic modeling also contributed to identifying new feed-back and feed-forward regulatory loops in cancer cells glycolysis, and to understanding the mode of metabolic action of glycolytic inhibitors. Thus, MCA and metabolic modeling allowed to propose new strategies for inhibiting glycolysis in cancer cells.

Microtubule-associated septin complexes modulate kinesin and dynein motility with differential specificities

Long-range membrane traffic is guided by microtubule-associated proteins and posttranslational modifications, which collectively comprise a traffic code. The regulatory principles of this code and how it orchestrates the motility of kinesin and dynein motors are largely unknown. Septins are a large family of GTP-binding proteins, which assemble into complexes that associate with microtubules. Using single-molecule invitro motility assays, we tested how the microtubule-associated SEPT2/6/7, SEPT2/6/7/9, and SEPT5/7/11 complexes affect the motilities of the constitutively active kinesins KIF5C and KIF1A and the dynein-dynactin-bicaudal D (DDB) motor complex. We found that microtubule-associated SEPT2/6/7 is a potent inhibitor of DDB and KIF5C, preventing mainly their association with microtubules. SEPT2/6/7 also inhibits KIF1A by obstructing stepping along microtubules. On SEPT2/6/7/9-coated microtubules, KIF1A inhibition is dampened by SEPT9, which alone enhances KIF1A, showing that individual septin subunits determine the regulatory properties of septin complexes. Strikingly, SEPT5/7/11 differs from SEPT2/6/7, in permitting the motility of KIF1A and immobilizing DDB to the microtubule lattice. In hippocampal neurons, filamentous SEPT5 colocalizes with somatodendritic microtubules that underlie Golgi membranes and lack SEPT6. Depletion of SEPT5 disrupts Golgi morphology and polarization of Golgi ribbons into the shaft of somato-proximal dendrites, which is consistent with the tethering of DDB to microtubules by SEPT5/7/11. Collectively, these results suggest that microtubule-associated complexes have differential specificities in the regulation of the motility and positioning of microtubule motors. We posit that septins are an integral part of the microtubule-based code that spatially controls membrane traffic.

Distinct evolution of type I glutamine synthetase in Plasmodium and its species-specific requirement

Malaria parasite lacks canonical pathways for amino acid biosynthesis and depends primarily on hemoglobin degradation and extracellular resources for amino acids. Interestingly, a putative gene for glutamine synthetase (GS) is retained despite glutamine being an abundant amino acid in human and mosquito hosts. Here we show Plasmodium GS has evolved as a unique type I enzyme with distinct structural and regulatory properties to adapt to the asexual niche. Methionine sulfoximine (MSO) and phosphinothricin (PPT) inhibit parasite GS activity. GS is localized to the parasite cytosol and abundantly expressed in all the life cycle stages. Parasite GS displays species-specific requirement in Plasmodium falciparum (Pf) having asparagine-rich proteome. Targeting PfGS affects asparagine levels and inhibits protein synthesis through eIF2α phosphorylation leading to parasite death. Exposure of artemisinin-resistant Pf parasites to MSO and PPT inhibits the emergence of viable parasites upon artemisinin treatment.