Biology subjects

Mikros, E.

Publications and source records attributed to Mikros, E..

6 recordsLinked to original sources

bioRxiv2026

Mitigating CYP450-Mediated Insecticide Resistance in Malaria Vectors with Cannabis-Derived Synergists: The Potential of Cannabidiol

Insecticide resistance in mosquitoes, largely mediated by cytochrome P450 monooxygenases (CYPs), compromises the efficacy of vector control tools. In this study, chemically-wise selected natural extracts and compounds were screened for their CYP inhibition potential. Among 37 tested plant extracts and fractions, a decarboxylated acidic fraction of industrial hemp (Cannabis sativa Linnaeus var. Futura 75) emerged as a promising hit, and phytochemical profiling identified cannabidiol (CBD) as its major component (IC = 18.37 M for CYP9K1). CBD was used as a scaffold to generate semisynthetic analogues; of which a piperazinyl analogue outperformed the natural scaffold demonstrating significantly greater potency (IC = 2.50 M for CYP9K1). Docking studies using homology-derived CYP9K1 models also supported a stronger binding affinity of the piperazinyl analogue relative to CBD. Toxicity assays using pyrethroid-resistant Anopheles gambiae Giles adults confirmed that neither CBD nor the piperazinyl analogue had intrinsic toxicity, yet the semisynthetic analogue significantly enhanced deltamethrin efficacy, showing a threefold synergistic effect. The safety profile of the cannabis compounds for non-target organisms was evaluated through human cell line cytotoxicity tests and bee toxicity assays, suggesting low non-target organism toxicity. Our study describes the identification of a plant-derived synergist lead with strong potential as an insecticide additive to combat metabolic resistance in malaria-transmitting mosquitoes.

pharmacology and toxicology↗

bioRxiv2024

High-resolution structures of the UapA purine transporter reveal unprecedented aspects of the elevator-type transport mechanism.

UapA is an extensively studied elevator-type purine transporter from the model fungus Aspergillus nidulans. Determination of a 3.6[A] inward-facing crystal structure lacking the cytoplasmic N-and C-tails, molecular dynamics (MD), and functional studies have led to speculative models of its transport mechanism and determination of substrate specificity. Here, we report full-length cryo-EM structures of UapA in new inward-facing apo- and substrate-loaded conformations at 2.05-3.5 [A] in detergent and lipid nanodiscs. The structures reveal in an unprecedented level of detail the role of water molecules and lipids in substrate binding, specificity, dimerization, and activity, rationalizing accumulated functional data. Unexpectedly, the N-tail is structured and interacts with both the core and scaffold domains. This finding, combined with mutational and functional studies and MD, points out how N-tail interactions couple proper subcellular trafficking and transport activity by wrapping UapA in a conformation necessary for ER-exit and but also critical for elevator-type conformational changes associated with substrate translocation once UapA has integrated into the plasma membrane. Our study provides detailed insights into important aspects of the elevator-type transport mechanism and opens novel issues on how the evolution of extended cytosolic tails in eukaryotic transporters, apparently needed for subcellular trafficking, might have been integrated into the transport mechanism.

biophysics↗

bioRxiv2022

Molecular basis of uracil/H+ symport mechanism operated by the FurE/NCS1 transporter

Transporters mediate the uptake of solutes, metabolites and drugs across the cell membrane. The eukaryotic FurE nucleobase/H+ symporter of Aspergillus nidulans has been used as a model protein to address structure-function relationships in the APC transporter superfamily, members of which are characterized by the LeuT-fold and seem to operate by the so-called rocking-bundle mechanism. In this study, we reveal the binding mode, translocation and release pathway of uracil/H+ by FurE, using path collective variable, funnel metadynamics and rationally designed mutational analysis. Our study reveals a step-wise, induced-fit, mechanism of ordered sequential transport of proton and uracil, which in turn suggests that the FurE symporter, and probably structurally similar transporters, functions as a multi-step gated pore, rather than employing rocking of compact domains, as generally proposed for APC transporters. In addition, our work further supports the emerging concept that specific elements of cytosolic terminal regions of transporters might be functionally important.

molecular biology↗

bioRxiv2019

Distinct specific interactions of the UapA transporter with membrane lipids are critical for dimerization, ER-exit and function

Transporters are transmembrane proteins that mediate the selective translocation of solutes across biological membranes. Recently, we have shown that specific interactions with plasma membrane phospholipids are essential for formation and/or stability of functional dimers of the purine transporter, UapA, a prototypic eukaryotic member of the ubiquitous NAT family. Here, we show that distinct interactions of UapA with specific or annular lipids are essential for ab initio formation of functional dimers in the ER or ER-exit and further subcellular trafficking. Through genetic screens we identify mutations that restore defects in dimer formation and/or trafficking. Suppressors of defective dimerization restore ab initio formation of UapA dimers in the ER. Most of these suppressors are located in the movable core domain, but also in the core-dimerization interface and in residues of the dimerization domain exposed to lipids. Molecular Dynamics suggest the majority of suppressors stabilize interhelical interactions in the core domain and thus assist the formation of functional UapA dimers. Among suppressors restoring dimerization, a specific mutation, T401P, was also isolated independently as a suppressor restoring trafficking, suggesting that stabilization of the core domain restores function by sustaining structural defects caused by abolishment of essential interactions with specific or annular lipids. Importantly, introduction of mutations topologically equivalent to T401P into a rat homologue of UapA, namely rSNBT1, permitted the functional expression of a mammalian NAT in A. nidulans. Thus, our results provide a potential route for the functional expression and manipulation of mammalian transporters in the model Aspergillus system.\n\nAuthor SummaryTransporters are proteins found in biological membranes, where they are involved in the selective movement of nutrients, ions, drugs and other small molecules across membranes. Consequently, their function is essential for cell viability, while their malfunction often results to disease. Recent findings have suggested that transporter functioning depends on proper interactions with associated membrane lipids. In this article, using UapA, a very well-studied transporter from a model fungus (Aspergillus nidulans), we show that two types of specific interactions with lipids are essential for tight and specific association of two UapA molecules in a single functional unit (UapA dimer), and for targeting to the cell membrane and transport activity. The first type of interaction concerns specific lipids associating with positively charged amino acids at the interface of the UapA dimer, whereas the other type involves lipids that interact with charged amino acids at the outer shell of the transporter. Most interestingly, defects due to abolishment of UapA-lipid interactions were shown to be restored by mutations that increase UapA stability. Using this information, we genetically manipulated and increased the stability of a mammalian transporter (rSNBT1), and thus achieved its functional expression in the experimentally tractable system of A. nidulans.

genetics↗

bioRxiv2019

Cytosolic termini of the FurE transporter regulate endocytosis, pH-dependent gating and specificity

FurE, a member of the NCS1 family, is an Aspergillus nidulans transporter specific for uracil, allantoin and uric acid. Recently we showed that C- or N-terminally truncated FurE versions are blocked for endocytosis and, surprisingly, show modified substrate specifities. Bifluorescence complementation assays and genetic analyses supported that the C- and N-termini interact dynamically and through this interaction regulate selective substrate translocation. Here we functionally dissect and delimit distinct motifs crucial for endocytosis, transport activity, substrate specificity and folding, in both cytosolic termini of FurE. Subsequently, we obtain novel genetic and in silico evidence supporting that the molecular dynamics of specific N- and C-terminal regions affect allosterically the gating mechanism responsible for substrate selection, via pH-dependent interactions with other internal cytosolic loops and membrane lipids. Our work shows that elongated cytoplasmic termini, acquired through evolution mostly in eukaryotic transporters, provide novel specific functional roles.

molecular biology↗

bioRxiv2018

Hydroxytyrosol (HT) analogues act as potent antifungals by direct disruption of the fungal cell membrane

Fungal infections constitute an emerging threat and a prevalent health problem due to increasing number of immunocompromised people and pharmacological or other treatments aiming at viral infections, cancer or allergies. Currently used antifungals suffer from inefficiency, toxic side effects and developing drug-resistance. Additionally, over the last two decades no new classes of antifungals have been approved, emphasizing the urgent need for developing a novel generation of antifungals. Here we investigate the antifungal activity of a series of chemically synthesized Hydroxytyrosol (HT) analogues. HT is one of the major phenolic compounds in olive oil, shown to possess radical-scavenging antioxidant, antiproliferative, proapoptotic and anti-inflammatory activities. No previous report has studied HT analogues as antifungals. We show that specific analogues have broad and strong antifungal activity, significantly stronger than the parent compound HT. Using A. nidulans as an in vivo cellular model system, we show that antifungal HT analogues have an unprecedented efficiency in fungal plasma membrane destruction. Importantly, antifungal HT analogues did not show toxicity in a mammalian cell line, whereas no resistance to HT analogues was obtained by standard mutagenesis. Our results open the way for the development of a novel, efficient and safer class of antifungals.

microbiology↗