Development of potent fluorescent polyamine toxins and application in labeling of ionotropic glutamate receptors in hippocampal neurons

Spider and Wasp Acylpolyamines: Venom Components and Versatile Pharmacological Leads, Probes, and Insecticidal Agents

Polyamines (PAs) are polycationic biogenic amines ubiquitously present in all life forms and are involved in molecular signaling and interaction, determining cell fate (e.g., cell proliferation, dif-ferentiation, and apoptosis). The intricate balance in the PAs' levels in the tissues will determine whether beneficial or detrimental effects will affect homeostasis. It's crucial to note that endoge-nous polyamines, like spermine and spermidine, play a pivotal role in our understanding of neu-rological disorders as they interact with membrane receptors and ion channels, modulating neuro-transmission. In spiders and wasps, monoamines (histamine, dopamine, serotonin, tryptamine) and polyamines (spermine, spermidine, acyl polyamines) comprise, with peptides and other sub-stances, the low molecular weight fraction of the venom. Acylpolyamines are venom components exclusively from spiders and a species of solitary wasp, which cause inhibition chiefly of iono-tropic glutamate receptors (AMPA, NMDA, and KA iGluRs) and nicotinic acetylcholine receptors (nAChRs). The first venom acylpolyamines ever discovered (argiopines, Joro and Nephila toxins, and philanthotoxins) have provided templates for the design and synthesis of numerous analogs. Thus far, analogs with high potency exert their effect at nanomolar concentrations, with high se-lectivity toward their ionotropic and ligand receptors. These potent and selective acylpolyamine analogs can serve biomedical purposes and pest control management. The structural modification of acylpolyamine with photolabile and fluorescent groups converted these venom toxins into use-ful molecular probes to discriminate iGluRs and nAchRs in cell populations. In various cases, the linear polyamines, like spermine and spermidine, constituting venom acyl polyamine backbones, have served as cargoes to deliver active molecules via a polyamine uptake system on diseased cells for targeted therapy. In this review, we examined examples of biogenic amines that play an essential role in neural homeostasis and cell signaling, contributing to human health and disease outcomes, which can be present in the venom of arachnids and hymenopterans. With an empha-sis on the spider and wasp venom acylpolyamines, we focused on the origin, structure, derivatiza-tion, and biomedical and biotechnological application of these pharmacologically attractive, chemically modular venom components.

Development and Characterization of Fluorescent Probes for the G Protein-Coupled Receptor 35

The orphan G protein-coupled receptor 35 (GPR35) is a potential target for the treatment of pain, inflammation, and metabolic diseases. Although many GPR35 agonists have been discovered, research on functional GPR35 ligands, such as fluorescent probes, is still limited. Herein, we developed a series of GPR35 fluorescent probes by conjugating a BODIPY fluorophore to DQDA, a known GPR35 agonist. All probes exhibited excellent GPR35 agonistic activity and desired spectroscopic properties, as determined by the DMR assay, bioluminescence resonance energy transfer (BRET)-based saturation, and kinetic binding experiments. Notably, compound 15 showed the highest binding potency and the weakest nonspecific BRET binding signal (K d = 3.9 nM). A BRET-based competition binding assay with 15 was also established and used to determine the binding constants and kinetics of unlabeled GPR35 ligands.

Natural-product-based fluorescent probes: recent advances and applications

Fluorescent probes are attractive tools for biology, drug discovery, disease diagnosis, and environmental analysis. In bioimaging, these easy-to-operate and inexpensive probes can be used to detect biological substances, obtain detailed cell images, track in vivo biochemical reactions, and monitor disease biomarkers without damaging biological samples. Over the last few decades, natural products have attracted extensive research interest owing to their great potential as recognition units for state-of-the-art fluorescent probes. This review describes representative natural-product-based fluorescent probes and recent discoveries, with a particular focus on fluorescent bioimaging and biochemical studies.

Boron-containing compounds on neurons: Actions and potential applications for treating neurodegenerative diseases

Boron-containing compounds (BCC) exert effects on neurons. After the expanding of both the identification and synthesis of new BCC, novel effects in living systems have been reported, many of these involving neuronal action. In this review, the actions of BCC on neurons are described; the effects have been inferred by boron deprivation or addition. Also, the effects can be related to those mediated by interaction on ionic channels, G-protein coupled receptors, or other receptors exerting modification on neuronal behavior. Additionally, BCC have exhibited effects by the modulation of inflammation or oxidative processes. BCC are expanding as drugs. Deprivation of boron sources from the diet shows the role of some natural BCC. However, the observations of several new synthesized compounds suggest their ability to act with attractive potency, efficacy, and long-term action on neuronal receptors or processes related with the origin and evolution of neurodegenerative processes. The details of BCC-target interactions are currently being elucidated in progress, as those observed from BCC-protein crystal complexes. Taking all of the above into account, the expansion is presumably near to having studies on the application of BCC as drugs on specific targets for treating neurodegenerative diseases.

A Structure-Activity Relationship Study of Bimodal BODIPY-Labeled PSMA-Targeting Bioconjugates

The aim of this study was to identify a high-affinity BODIPY peptidomimetic that targets the prostate-specific membrane antigen (PSMA) as a potential bimodal imaging probe for prostate cancer. For the structure-activity study, several BODIPY (difluoroboron dipyrromethene) derivatives with varying spacers between the BODIPY dye and the PSMA Glu-CO-Lys binding motif were prepared. Corresponding affinities were determined by competitive binding assays in PSMA-positive LNCaP cells. One compound was identified with comparable affinity (IC50 =21.5±0.1 nM) to Glu-CO-Lys-Ahx-HBED-CC (PSMA-11) (IC50 =18.4±0.2 nM). Radiolabeling was achieved by Lewis-acid-mediated 19 F/18 F exchange in moderate molar activities (∼0.7 MBq nmol-1 ) and high radiochemical purities (>99 %) with mean radiochemical yields of 20-30 %. Cell internalization of the 18 F-labeled high-affinity conjugate was demonstrated in LNCaP cells showing gradual increasing PSMA-mediated internalization over time. By fluorescence microscopy, localization of the high-affinity BODIPY-PSMA conjugate was found in the cell membrane at early time points and also in subcellular compartments at later time points. In summary, a high-affinity BODIPY-PSMA conjugate has been identified as a suitable candidate for the development of PSMA-specific dual-imaging agents.

Lighting Up the Plasma Membrane: Development and Applications of Fluorescent Ligands for Transmembrane Proteins

Despite the fact that transmembrane proteins represent the main therapeutic targets for decades, complete and in-depth knowledge about their biochemical and pharmacological profiling is not fully available. In this regard, target-tailored small-molecule fluorescent ligands are a viable approach to fill in the missing pieces of the puzzle. Such tools, coupled with the ability of high-precision optical techniques to image with an unprecedented resolution at a single-molecule level, helped unraveling many of the conundrums related to plasma proteins' life-cycle and druggability. Herein, we review the recent progress made during the last two decades in fluorescent ligand design and potential applications in fluorescence microscopy of voltage-gated ion channels, ligand-gated ion channels and G-coupled protein receptors.

BODIPY-based probes for the fluorescence imaging of biomolecules in living cells

Fluorescence imaging techniques have been widely used to visualize biological molecules and phenomena. In particular, several studies on the development of small-molecule fluorescent probes have been carried out, because their fluorescence properties can be easily tuned by synthetic chemical modification. For this reason, various fluorescent probes have been developed for targeting biological components, such as proteins, peptides, amino acids, and ions, to the interior and exterior of cells. In this review, we cover advances in the development of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based fluorescent probes for biological studies over the past decade.

Pharmacological Alternatives for the Treatment of Neurodegenerative Disorders: Wasp and Bee Venoms and Their Components as New Neuroactive Tools

Neurodegenerative diseases are relentlessly progressive, severely impacting affected patients, families and society as a whole. Increased life expectancy has made these diseases more common worldwide. Unfortunately, available drugs have insufficient therapeutic effects on many subtypes of these intractable diseases, and adverse effects hamper continued treatment. Wasp and bee venoms and their components are potential means of managing or reducing these effects and provide new alternatives for the control of neurodegenerative diseases. These venoms and their components are well-known and irrefutable sources of neuroprotectors or neuromodulators. In this respect, the present study reviews our current understanding of the mechanisms of action and future prospects regarding the use of new drugs derived from wasp and bee venom in the treatment of major neurodegenerative disorders, including Alzheimer’s Disease, Parkinson’s Disease, Epilepsy, Multiple Sclerosis and Amyotrophic Lateral Sclerosis.

Methods to locate and track ion channels and receptors expressed in live neurons

Brain cells use electrical and chemical signaling to communicate with each other and to send and receive information from the body. These neurons also encode information such as memories and are constantly adapting to changes as a result of positive alterations, such as learning, or negative events, such as neurological insults or neurodegeneration. In the last two decades, it has become clear that the placement of minute branches of neurons and, more importantly for the topic of this review, the placement of individual protein molecules, are the key events that enable neuronal network building and pruning. Advances in both electrophysiology and light-based imaging have allowed neuroscientists to answer fundamental questions about the key proteins involved in memory formation, maintenance, and loss. These findings have been enabled often through the clever use of chemical biology, biotechnology, and genetic engineering. In this review, we highlight numerous examples where chemical biology was used to provide new tools to answer difficult and near impossible questions in neurobiology.

Critical design issues in the targeted molecular imaging of cell surface receptors

The molecular imaging of cell-surface receptors draws closer to reality.