The mammalian actin elongation factor ENAH/MENA contributes to autophagosome formation via its actin regulatory function

Macroautophagy/autophagy is a catabolic process crucial for degrading cytosolic components and damaged organelles to maintain cellular homeostasis, enabling cells to survive in extreme extracellular environments. ENAH/MENA, a member of the Ena/VASP protein family, functions as a highly efficient actin elongation factor. In this study, our objective was to explore the role of ENAH in the autophagy process. Initially, we demonstrated that depleting ENAH in cancer cells inhibits autophagosome formation. Subsequently, we observed ENAH's colocalization with MAP1LC3/LC3 during tumor cell starvation, dependent on actin cytoskeleton polymerization and the interaction between ENAH and BECN1 (beclin 1). Additionally, mammalian ATG9A formed a ring-like structure around ENAH-LC3 puncta during starvation, relying on actin cytoskeleton polymerization. Furthermore, ENAH's EVH1 and EVH2 domains were found to be indispensable for its colocalization with LC3 and BECN1, while the PRD domain played a crucial role in the formation of the ATG9A ring. Finally, our study revealed ENAH-led actin comet tails in autophagosome trafficking. In conclusion, our findings provide initial insights into the regulatory role of the mammalian actin elongation factor ENAH in autophagy.

Hydrazo Pyrazole-Pyridone Fluorescent tag for NLO, Live cell imaging, LFPs visualization, Photophysical probing, and Electrochemical sensor for Dopamine detection

The present communication reports on the synthesis of a novel methyl-pyridone azo fluorescent tag (MPAFT) were proven through 1H (NMR), FT-IR, UV-vis, and high-resolution mass spectrometry. The quantum chemical parameters of MPAFT were evaluated using density functional theory (DFT) analysis. It was further investigated for its latent fingerprint (LFPs) in various surfaces and anticounterfeiting applications. By exposing Level I-Level III, ridge features to UV light with a wavelength of 365 nm, a bioimaging investigation has also demonstrated the potential of MPAFT's emission behaviour. The cyclic voltammetry (CV) and linear sweep voltammetry (LSV) at MPAFT/MGCE (modified glassy carbon electrode) were used to explore the electrochemical sensitivity and reliable detection of dopamine (DA) in neutral PBS (pH 7) electrolyte solution, and the results show good sensitivity and detection. The lower detection limit for LSV was 0.81 μM under optimum conditions.

Inhibition of Autophagy Alters Intracellular Transport of APP Resulting in Increased APP Processing

Alzheimer's disease (AD) pathology is characterized by amyloid beta (Aβ) plaques and dysfunctional autophagy. Aβ is generated by sequential proteolytic cleavage of amyloid precursor protein (APP), and the site of intracellular APP processing is highly debated, which may include autophagosomes. Here, we investigated the involvement of autophagy, including the role of ATG9 in APP intracellular trafficking and processing by applying the RUSH system, which allows studying the transport of fluorescently labeled mCherry-APP-EGFP in a systematic way, starting from the endoplasmic reticulum. HeLa cells, expressing the RUSH mCherry-APP-EGFP system, were investigated by live cell imaging, immunofluorescence, and Western blot. We found that mCherry-APP-EGFP passed through the Golgi faster in ATG9 knockout cells. Furthermore, ATG9 deletion shifted mCherry-APP-EGFP from early endosomes and lysosomes toward the plasma membrane concomitant with reduced endocytosis. Importantly, this alteration in mCherry-APP-EGFP transport resulted in increased secreted mCherry-soluble APP and C-terminal fragment-EGFP. These effects were also phenocopied by pharmacological inhibition of ULK1, indicating that autophagy is regulating the intracellular trafficking and processing of APP. These findings contribute to the understanding of the role of autophagy in APP metabolism and could potentially have implications for new therapeutic approaches for AD.

Acoustic Wave-Induced Stroboscopic Optical Mechanotyping of Adherent Cells

In this study, a novel, high content technique using a cylindrical acoustic transducer, stroboscopic fast imaging, and homodyne detection to recover the mechanical properties (dynamic shear modulus) of living adherent cells at low ultrasonic frequencies is presented. By analyzing the micro-oscillations of cells, whole populations are simultaneously mechanotyped with sub-cellular resolution. The technique can be combined with standard fluorescence imaging allowing to further cross-correlate biological and mechanical information. The potential of the technique is demonstrated by mechanotyping co-cultures of different cell types with significantly different mechanical properties.

Exo84c-regulated degradation is involved in the normal self-incompatible response in Brassicaceae

The self-incompatibility system evolves in angiosperms to promote cross-pollination by rejecting self-pollination. Here, we show the involvement of Exo84c in the SI response of both Brassica napus and Arabidopsis. The expression of Exo84c is specifically elevated in stigma during the SI response. Knocking out Exo84c in B. napus and SI Arabidopsis partially breaks down the SI response. The SI response inhibits both the protein secretion in papillae and the recruitment of the exocyst complex to the pollen-pistil contact sites. Interestingly, these processes can be partially restored in exo84c SI Arabidopsis. After incompatible pollination, the turnover of the exocyst-labeled compartment is enhanced in papillae. However, this process is perturbed in exo84c SI Arabidopsis. Taken together, our results suggest that Exo84c regulates the exocyst complex vacuolar degradation during the SI response. This process is likely independent of the known SI pathway in Brassicaceae to secure the SI response.

Chromo-Fluorogenic Rhodamine-Based Amphiphilic Probe as a Selective and Sensitive Sensor for Intracellular Cu(I) in Living Cells

Fluorescent probes are widely studied for metal ion detection because of their multiple favorable properties such as high sensitivity and selectivity, quick response, naked eye detection, and in situ monitoring. However, optical probes that can effectively detect the Cu(I) level in cell interiors are rare due to the difficulty associated with selectively and sensitively detecting this metal ion in a cell environment. Therefore, we designed and synthesized three water-soluble probes (1-3) with a 1,3,5-triazine core decorated by three substituents: a hydrophobic alkyl chain, a hydrophilic maltose, and a rhodamine B hydrazine fluorophore. Among the probes, probe 1, which has an octyl chain and a branched maltose group, was the most effective at sensing Cu+ in aqueous solution. Upon addition of Cu+, this probe showed a dramatic color change from colorless to pink in daylight and displayed an intense yellow fluorescence emission under 365 nm light. The limit of detection and dissociation constant (Kd) of this probe were 20 nM and 1.1 × 10-12 M, respectively, which are the lowest values reported to date. The two metal ion-binding sites and the aggregation-induced emission enhancement effect, endowed by the branched maltose group and the octyl chain, respectively, are responsible for the high sensitivity and selectivity of this probe for Cu+ detection, as demonstrated by 1H NMR, dynamic light scattering, and transmission electron microscopy studies. Furthermore, the probe successfully differentiated the Cu(I) level of cancer cells from that of the normal cells. Thus, the probe holds potential for real-time monitoring of Cu(I) level in biological samples and bioimaging of cancer cells.

Near-infrared imaging of phytochrome-derived autofluorescence in plant nuclei

Capturing images of the nuclear dynamics within live cells is an essential technique for comprehending the intricate biological processes inherent to plant cell nuclei. While various methods exist for imaging nuclei, including combining fluorescent proteins and dyes with microscopy, there is a dearth of commercially available dyes for live-cell imaging. In Arabidopsis thaliana, we discovered that nuclei emit autofluorescence in the near-infrared (NIR) range of the spectrum and devised a non-invasive technique for the visualization of live cell nuclei using this inherent NIR autofluorescence. Our studies demonstrated the capability of the NIR imaging technique to visualize the dynamic behavior of nuclei within primary roots, root hairs, and pollen tubes, which are tissues that harbor a limited number of other organelles displaying autofluorescence. We further demonstrated the applicability of NIR autofluorescence imaging in various other tissues by incorporating fluorescence lifetime imaging techniques. Nuclear autofluorescence was also detected across a wide range of plant species, enabling analyses without the need for transformation. The nuclear autofluorescence in the NIR wavelength range was not observed in animal or yeast cells. Genetic analysis revealed that this autofluorescence was caused by the phytochrome protein. Our studies demonstrated that nuclear autofluorescence imaging can be effectively employed not only in model plants but also for studying nuclei in non-model plant species.

Deep Learning-Assisted Automated Multidimensional Single Particle Tracking in Living Cells

The translational and rotational dynamics of anisotropic optical nanoprobes revealed in single particle tracking (SPT) experiments offer molecular-level information about cellular activities. Here, we report an automated high-speed multidimensional SPT system integrated with a deep learning algorithm for tracking the 3D orientation of anisotropic gold nanoparticle probes in living cells with high localization precision (<10 nm) and temporal resolution (0.9 ms), overcoming the limitations of rotational tracking under low signal-to-noise ratio (S/N) conditions. This method can resolve the azimuth (0°-360°) and polar angles (0°-90°) with errors of less than 2° on the experimental and simulated data under S/N of ∼4. Even when the S/N approaches the limit of 1, this method still maintains better robustness and noise resistance than the conventional pattern matching methods. The usefulness of this multidimensional SPT system has been demonstrated with a study of the motions of cargos transported along the microtubules within living cells.

Exploring the potential of pheophorbide A, a chlorophyll-derived compound in modulating GLUT for maintaining glucose homeostasis

Introduction

Pheophorbide A, a chlorophyll-breakdown product, is primarily investigated for its anti-oxidant and anti-inflammatory activity. Recent reports on pheophorbide A have shown its potential in lowering blood glucose levels, thus leading to the exploration of its use in diabetes management. Literature has also shown its effect on enhanced insulin secretion, whereas its mechanism on glucose stimulated insulin secretion (GSIS) in pancreatic β cells remains unexplored.

Methods

In-silico and in-vitro investigations were used to explore the effect of pheophorbide A on class I glucose transporters (GLUTs). In-silico studies include - Molecular docking studies and stability assessment using GROMACS. In-vitro studies include - MTT assay, Glucose uptake assay, Live-cell imaging and tracking of GLUTs in presence of Pheophorbide A compared to control.

Results

Molecular docking studies revealed better binding affinity of pheophorbide A with GLUT4 (-11.2 Kcal/mol) and GLUT1 (-10.7 Kcal/mol) when compared with metformin (-5.0 Kcal/mol and -4.9 Kcal/mol, respectively). Glucose levels are largely regulated by GLUTs where GLUT1 is one of the transporters that is ubiquitously present in human β cells. Thus, we confirmed the stability of the complex, that is, pheophorbide A-GLUT1 using GROMACS for 100 ns. We further assessed its effect on a pancreatic β cell line (INS-1) for its viability using an MTT assay. Pheophorbide A (0.1-1 µM) showed a dose-dependent response on cell viability and was comparable to standard metformin. To assess how pheophorbide A mechanistically acts on GLUT1 in pancreatic β cell, we transfected INS-1 cells with GLUT1-enhanced green fluorescent protein and checked how the treatment of pheophorbide A (0.50 µM) modulates GLUT1 trafficking using live-cell imaging. We observed a significant increase in GLUT1 density when treated with pheophorbide A (0.442 ± 0.01 µm-2) at 20 mM glucose concentration when compared to GLUT1 control (0.234 ± 0.01 µm-2) and metformin (0.296 ± 0.02 µm-2). The average speed and distance travelled by GLUT1 puncta were observed to decrease when treated with pheophorbide A. The present study also demonstrated the potential of pheophorbide A to enhance glucose uptake in β cells.

Conclusion

The current study's findings were validated by in-silico and cellular analyses, suggesting that pheophorbide A may regulate GLUT1 and might be regarded as a potential lead for boosting the GSIS pathway, thus maintaining glucose homeostasis.

Integrin α5 regulates motility of human monocyte-derived Langerhans cells during immune response

Langerhans cells (LCs) are mainly present in the epidermis and mucosa, and have important roles during skin infection. Migration of LCs to lymph nodes is essential for antigen presentation. However, due to the difficulties in isolating and culturing human LCs, it is not fully understood how LCs move and interact with the extracellular matrix (ECM) through their adhesion molecules such as integrin, during the immune responses. In this study, we aimed to investigate LC motility, cell shape and the role of integrin under inflammatory conditions using monocyte-derived Langerhans cells (moLCs) as a model. As a result, lipopolysaccharide (LPS) stimulation increased adhesion on fibronectin coated substrate and integrin α5 expression in moLCs. Time-lapse imaging of moLCs revealed that stimulation with LPS elongated cell shape, whilst decreasing their motility. Additionally, this decrease in motility was not observed when pre-treated with a neutralising antibody targeting integrin α5. Together, our data suggested that activation of LCs decreases their motility by promoting integrin α5 expression to enhance their affinity to the fibronectin, which may contribute to their migration during inflammation.

Spatial-Temporal Mapping Reveals the Golgi as the Major Processing Site for the Pathogenic Swedish APP Mutation: Familial APP Mutant Shifts the Major APP Processing Site

Alzheimer's disease is associated with increased levels of amyloid beta (Aβ) generated by sequential intracellular cleavage of amyloid precursor protein (APP) by membrane-bound secretases. However, the spatial and temporal APP cleavage events along the trafficking pathways are poorly defined. Here, we use the Retention Using Selective Hooks (RUSH) to compare in real time the anterograde trafficking and temporal cleavage events of wild-type APP (APPwt) with the pathogenic Swedish APP (APPswe) and the disease-protective Icelandic APP (APPice). The analyses revealed differences in the trafficking profiles and processing between APPwt and the APP familial mutations. While APPwt was predominantly processed by the β-secretase, BACE1, following Golgi transport to the early endosomes, the transit of APPswe through the Golgi was prolonged and associated with enhanced amyloidogenic APP processing and Aβ secretion. A 20°C block in cargo exit from the Golgi confirmed β- and γ-secretase processing of APPswe in the Golgi. Inhibition of the β-secretase, BACE1, restored APPswe anterograde trafficking profile to that of APPwt. APPice was transported rapidly through the Golgi to the early endosomes with low levels of Aβ production. This study has revealed different intracellular locations for the preferential cleavage of APPwt and APPswe and Aβ production, and the Golgi as the major processing site for APPswe, findings relevant to understand the molecular basis of Alzheimer's disease.

Tracing endogenous proteins in living cells through electrotransfer of mRNA encoding chromobodies

Chromobodies made of nanobodies fused to fluorescent proteins are powerful tools for targeting and tracing intracellular proteins in living cells. Typically, this is achieved by transfecting plasmids encoding the chromobodies. However, an excess of unbound chromobody relative to the endogenous antigen can result in high background fluorescence in live cell imaging. Here, we overcome this problem by using mRNA encoding chromobodies. Our approach allows one to precisely control the amount of chromobody expressed inside the cell by adjusting the amount of transfected mRNA. To challenge our method, we evaluate three chromobodies targeting intracellular proteins of different abundance and cellular localization, namely lamin A/C, Dnmt1 and actin. We demonstrate that the expression of chromobodies in living cells by transfection of tuned amounts of the corresponding mRNAs allows the accurate tracking of their cellular targets by time-lapse fluorescence microscopy.

A new method to measure aquaporin-facilitated membrane diffusion of hydrogen peroxide and cations in plant suspension cells

Plant aquaporins (AQPs) facilitate the membrane diffusion of water and small solutes, including hydrogen peroxide (H2 O2 ) and, possibly, cations, essential signalling molecules in many physiological processes. While the determination of the channel activity generally depends on heterologous expression of AQPs in Xenopus oocytes or yeast cells, we established a genetic tool to determine whether they facilitate the diffusion of H2 O2 through the plasma membrane in living plant cells. We designed genetic constructs to co-express the fluorescent H2 O2 sensor HyPer and AQPs, with expression controlled by a heat shock-inducible promoter in Nicotiana tabacum BY-2 suspension cells. After induction of ZmPIP2;5 AQP expression, a HyPer signal was recorded when the cells were incubated with H2 O2 , suggesting that ZmPIP2;5 facilitates H2 O2 transmembrane diffusion; in contrast, the ZmPIP2;5W85A mutated protein was inactive as a water or H2 O2 channel. ZmPIP2;1, ZmPIP2;4 and AtPIP2;1 also facilitated H2 O2 diffusion. Incubation with abscisic acid and the elicitor flg22 peptide induced the intracellular H2 O2 accumulation in BY-2 cells expressing ZmPIP2;5. We also monitored cation channel activity of ZmPIP2;5 using a novel fluorescent photo-switchable Li+ sensor in BY-2 cells. BY-2 suspension cells engineered for inducible expression of AQPs as well as HyPer expression and the use of Li+ sensors constitute a powerful toolkit for evaluating the transport activity and the molecular determinants of PIPs in living plant cells.

Live Cell Imaging by Single-Shot Common-Path Wide Field-of-View Reflective Digital Holographic Microscope

Quantitative phase imaging by digital holographic microscopy (DHM) is a nondestructive and label-free technique that has been playing an indispensable role in the fields of science, technology, and biomedical imaging. The technique is competent in imaging and analyzing label-free living cells and investigating reflective surfaces. Herein, we introduce a new configuration of a wide field-of-view single-shot common-path off-axis reflective DHM for the quantitative phase imaging of biological cells that leverages several advantages, including being less-vibration sensitive to external perturbations due to its common-path configuration, also being compact in size, simple in optical design, highly stable, and cost-effective. A detailed description of the proposed DHM system, including its optical design, working principle, and capability for phase imaging, is presented. The applications of the proposed system are demonstrated through quantitative phase imaging results obtained from the reflective surface (USAF resolution test target) as well as transparent samples (living plant cells). The proposed system could find its applications in the investigation of several biological specimens and the optical metrology of micro-surfaces.

Gene Editing and Small Molecule Inhibitors of the RNA Binding Protein IGF2BP2/IMP2 Show its Potential as an Anti-Cancer Drug Target

BACKGROUND

The RNA-binding protein IGF2BP2/IMP2/VICKZ2/p62 is an oncofetal protein that is overexpressed in several cancer entities. Employing IMP2 knockout colorectal cancer cells, we could show the important role of IMP2 in several hallmarks of cancer. This study aimed to functionally characterize IMP2 in lung (A549, LLC1) and hepatocellular carcinoma (HepG2, Huh7) cell lines to assess its role as a potential target for these cancer entities.

METHODS

IMP2 knockouts were generated by CRISPR/Cas9 and its variant approach prime editing; the editing efficiency of two single guide RNAs (sgRNAs) was verified via next-generation sequencing. We studied the effect of IMP2 knockout on cell proliferation, colony formation, and migration and employed small-molecule inhibitors of IMP2.

RESULTS

Despite multiple attempts, it was not possible to generate IMP2 biallelic knockouts in A549 and Huh7 cells. Both sgRNAs showed good editing efficiency. However, edited cells lost their ability to proliferate. The attempt to generate an IMP2 biallelic knockout in LLC1 cells using CRISPR/Cas9 was successful. Monoallelic knockout cell lines of IMP2 showed a reduction in 2D cell proliferation and reduced migration. In 3D cultures, a change in morphology from compact spheroids to loose aggregates and a distinct reduction in the colony formation ability of the IMP2 knockouts was observed, an effect that was mimicked by previously identified IMP2 inhibitor compounds that also showed an inhibitory effect on colony formation.

CONCLUSIONS

Our in vitro target validation supports that IMP2 is essential for tumor cell proliferation, migration, and colony formation in several cancer entities.

DARTS: an open-source Python pipeline for Ca2+ microdomain analysis in live cell imaging data

Ca2+ microdomains play a key role in intracellular signaling processes. For instance, they mediate the activation of T cells and, thus, the initial adaptive immune system. They are, however, also of utmost importance for activation of other cells, and a detailed understanding of the dynamics of these spatially localized Ca2+ signals is crucial for a better understanding of the underlying signaling processes. A typical approach to analyze Ca2+ microdomain dynamics is live cell fluorescence microscopy imaging. Experiments usually involve imaging a larger number of cells of different groups (for instance, wild type and knockout cells), followed by a time consuming image and data analysis. With DARTS, we present a modular Python pipeline for efficient Ca2+ microdomain analysis in live cell imaging data. DARTS (Deconvolution, Analysis, Registration, Tracking, and Shape normalization) provides state-of-the-art image postprocessing options like deep learning-based cell detection and tracking, spatio-temporal image deconvolution, and bleaching correction. An integrated automated Ca2+ microdomain detection offers direct access to global statistics like the number of microdomains for cell groups, corresponding signal intensity levels, and the temporal evolution of the measures. With a focus on bead stimulation experiments, DARTS provides a so-called dartboard projection analysis and visualization approach. A dartboard projection covers spatio-temporal normalization of the bead contact areas and cell shape normalization onto a circular template that enables aggregation of the spatiotemporal information of the microdomain detection results for the individual cells of the cell groups of interest. The dartboard visualization allows intuitive interpretation of the spatio-temporal microdomain dynamics at the group level. The application of DARTS is illustrated by three use cases in the context of the formation of initial Ca2+ microdomains after cell stimulation. DARTS is provided as an open-source solution and will be continuously extended upon the feedback of the community. Code available at: 10.5281/zenodo.10459243.

Red-Fluorescent Covalent Organic Framework Nanospheres for Trackable Anticancer Drug Delivery

Covalent organic frameworks (COFs) have emerged as promising drug carriers due to their structural variability, inherent porosity, and customizable functions. However, most COFs used in drug delivery suffer from low cellular bioavailability and poor luminescence properties. In this study, we designed a series of size-tunable, crystalline, and red-fluorescent COF nanospheres (COFNSs) for trackable anticancer drug delivery. The semiconducting COFNSs were prepared by condensations of 1,3,5-triformylbenzene (TFB) with various dihydrazide blocks through the Schiff-base reaction, resulting in red emission at 647 nm and excellent fluorescence stability (∼100% for 1 h). Such fluorescence property allowed for systematic investigation of the cellular endocytosis pathway of COFNSs, visualization of drug delivery, and observation of the cell apoptosis process. The COFNSs exhibited high cell viability (>90%), a loading capacity of 183 wt % for the anticancer drug camptothecin (CPT), and significant enhancement in inhibiting 4T1 cancers both in vitro and in vivo as the CPT nanocarrier. This progress presents a valuable approach to design COF nanocarriers with integrated fluorescent and drug delivery functions.

Akt activator SC79 stimulates antibacterial nitric oxide generation in human nasal epithelial cells in vitro

BACKGROUND

The role of Akt in nasal immunity is unstudied. Akt phosphorylates and activates endothelial nitric oxide synthase (eNOS) expressed in epithelial ciliated cells. Nitric oxide (NO) production by ciliated cells can have antibacterial and antiviral effects. Increasing nasal NO may be a useful antipathogen strategy in chronic rhinosinusitis (CRS). We previously showed that small-molecule Akt activator SC79 induces nasal cell NO production and suppresses IL-8 via the transcription factor Nrf-2. We hypothesized that SC79 NO production may additionally have antibacterial effects.

METHODS

NO production was measured using fluorescent dye DAF-FM. We tested effects of SC79 during co-culture of Pseudomonas aeruginosa with primary nasal epithelial cells, using CFU counting and live-dead staining to quantify bacterial killing. Pharmacology determined the mechanism of SC79-induced NO production and tested dependence on Akt.

RESULTS

SC79 induced dose-dependent, Akt-dependent NO production in nasal epithelial cells. The NO production required eNOS and Akt. The NO released into the airway surface liquid killed P. aeruginosa. No toxicity (LDH release) or inflammatory effects (IL8 transcription) were observed over 24 h.

CONCLUSIONS

Together, these data suggest multiple immune pathways are stimulated by SC79, with antipathogen effects. This in vitro pilot study suggests that a small-molecule Akt activator may have clinical utility in CRS or respiratory other infection settings, warranting future in vivo studies.

Transparent Intracellular Sensing Platform with Si Needles for Simultaneous Live Imaging

Vertically ordered Si needles are of particular interest for long-term intracellular recording owing to their capacity to infiltrate living cells with negligible damage and minimal toxicity. Such intracellular recordings could greatly benefit from simultaneous live cell imaging without disrupting their culture, contributing to an in-depth understanding of cellular function and activity. However, the use of standard live imaging techniques, such as inverted and confocal microscopy, is currently impeded by the opacity of Si wafers, typically employed for fabricating vertical Si needles. Here, we introduce a transparent intracellular sensing platform that combines vertical Si needles with a percolated network of Au-Ag nanowires on a transparent elastomeric substrate. This sensing platform meets all prerequisites for simultaneous intracellular recording and imaging, including electrochemical impedance, optical transparency, mechanical compliance, and cell viability. Proof-of-concept demonstrations of this sensing platform include monitoring electrical potentials in cardiomyocyte cells and in three-dimensionally engineered cardiovascular tissue, all while conducting live imaging with inverted and confocal microscopes. This sensing platform holds wide-ranging potential applications for intracellular research across various disciplines such as neuroscience, cardiology, muscle physiology, and drug screening.

Aberrations in Cell Signaling Quantified in Diabetic Murine Globes after Injury

The corneal epithelium is an avascular structure that has a unique wound healing mechanism, which allows for rapid wound closure without compromising vision. This wound healing mechanism is attenuated in diabetic patients, resulting in poor clinical outcomes and recurrent non-healing erosion. We investigated changes in cellular calcium signaling activity during the wound response in murine diabetic tissue using live cell imaging from both ex vivo and in vitro models. The calcium signaling propagation in diabetic cells was significantly decreased and displayed altered patterns compared to non-diabetic controls. Diabetic cells and tissue display distinct expression of the purinergic receptor, P2X7, which mediates the wound healing response. We speculate that alterations in P2X7 expression, interactions with other proteins, and calcium signaling activity significantly impact the wound healing response. This may explain aberrations in the diabetic wound response.

Human neutrophil extracellular traps do not impair in vitro Toxoplasma gondii infection

Introduction

Toxoplasma gondii, responsible for causing toxoplasmosis, is a prevalent food and waterborne pathogen worldwide. It commonly infects warm-blooded animals and affects more than a third of the global human population. Once ingested, the parasite enters the host's small intestine and rapidly disseminates throughout the body via the bloodstream, infiltrating various tissues. Leukocyte-driven responses are vital against T. gondii, with neutrophils playing a dual role: swiftly recruited to infection sites, releasing inflammatory mediators, and serving as a replication hub and Trojan horses, aiding parasite spread. Neutrophils from various hosts release extracellular traps (NETs) against the protozoan. However, gaps persist regarding the mechanisms of NETs production to parasite and their significance in infection control. This study investigates the interplay between human neutrophils and T. gondii, exploring dynamics, key molecules, and signaling pathways involved in NETs production upon protozoan challenge.

Methods and Results

Using confocal and electron microscopy, live cell imaging, pharmacological inhibitors, and DNA quantification assays, we find that human neutrophils promptly release both classical and rapid NETs upon pathogen stimulation. The NETs structure exhibits diverse phenotypes over time and is consistently associated with microorganisms. Mechanisms involve neutrophil elastase and peptidylarginine deiminase, along with intracellular calcium signaling and the PI3K pathway. Unexpectedly, human traps do not diminish viability or infectivity, but potentially aid in capturing parasites for subsequent neutrophil phagocytosis and elimination.

Discussion

By revealing NETs formation mechanisms and their nuanced impact on T. gondii infection dynamics, our findings contribute to broader insights into host-pathogen relationships.

Dynamics of mitochondrial membranes under photo-oxidative stress with high spatiotemporal resolution

In our study, we harnessed an original Enhanced Speed Structured Illumination Microscopy (Fast-SIM) imaging setup to explore the dynamics of mitochondrial and inner membrane ultrastructure under specific photo-oxidation stress induced by Chlorin-e6 and light irradiation. Notably, our Fast-SIM system allowed us to observe and quantify a distinct remodeling and shortening of the mitochondrial structure after 60-80 s of irradiation. These changes were accompanied by fusion events of adjacent inner membrane cristae and global swelling of the organelle. Preceding these alterations, a larger sequence was characterized by heightened dynamics within the mitochondrial network, featuring events such as mitochondrial fission, rapid formation of tubular prolongations, and fluctuations in cristae structure. Our findings provide compelling evidence that, among enhanced-resolution microscopy techniques, Fast-SIM emerges as the most suitable approach for non-invasive dynamic studies of mitochondrial structure in living cells. For the first time, this approach allows quantitative and qualitative characterization of successive steps in the photo-induced oxidation process with sufficient spatial and temporal resolution.

Thermus thermophilus polyploid cells directly imaged by X-ray laser diffraction

Thermus thermophilus is reportedly polyploid and carries four to five identical genome copies per cell, based on molecular biological experiments. To directly detect polyploidy in this bacterium, we performed live cell imaging by X-ray free-electron laser (XFEL) diffraction and observed its internal structures. The use of femtosecond XFEL pulses enables snapshots of live, undamaged cells. For successful XFEL imaging, we developed a bacterial culture method using a starch- and casein-rich medium that produces a predominance of rod-shaped cells shorter than the focused XFEL beam size, which is slightly smaller than 2 µm. When cultured in the developed medium, the length of T. thermophilus cells, which is typically ~4 µm, was less than half its usual length. We placed living cells in a micro-liquid enclosure array and successively exposed each enclosure to a single XFEL pulse. A cell image was successfully obtained by the coherent diffractive imaging technique with iterative phase retrieval calculations. The reconstructed cell image revealed five peaks, which are most likely to be nucleoids, arranged in a row in the polyploid cell without gaps. This study demonstrates that XFELs offer a novel approach for visualizing the internal nanostructures of living, micrometer-sized, polyploid bacterial cells.

pH-Dependence Cytotoxicity Evaluation of Artepillin C against Tumor Cells

Brazilian green propolis is a well-known product that is consumed globally. Its major component, Artepillin C, showed potential as an antitumor product. This study explored the impact of Artepillin C on fibroblast and glioblastoma cell lines, used as healthy and very aggressive tumor cell lines, respectively. The focus of the study was to evaluate the pH-dependence of Artepillin C cytotoxicity, since tumor cells are known to have a more acidic extracellular microenvironment compared to healthy cells, and Artepillin C was shown to become more lipophilic at lower pH values. Investigations into the pH-dependency of Artepillin C (6.0-7.4), through viability assays and live cell imaging, revealed compelling insights. At pH 6.0, MTT assays showed the pronounced cytotoxic effects of Artepillin C, yielding a notable reduction in cell viability to less than 12% among glioblastoma cells following a 24 h exposure to 100 µM of Artepillin C. Concurrently, LDH assays indicated significant membrane damage, affecting approximately 50% of the total cells under the same conditions. Our Laurdan GP analysis suggests that Artepillin C induces autophagy, and notably, provokes a lipid membrane packing effect, contributing to cell death. These combined results affirm the selective cytotoxicity of Artepillin C within the acidic tumor microenvironment, emphasizing its potential as an effective antitumor agent. Furthermore, our findings suggest that Artepillin C holds promise for potential applications in the realm of anticancer therapies given its pH-dependence cytotoxicity.

An Improved Toolkit of Gateway- and Gibson Assembly-Compatible Vectors for Protoplast Transfection and Agrobacterium-Mediated Plant Transformation

Objective

Understanding the regulation and function of plant genes is essential for addressing the challenges faced by modern agriculture. Plant transformation, in conjunction with fluorescence microscopy, offers a powerful approach to investigate the dynamic behavior of plant genes and the proteins they encode. We previously developed a set of Gateway-compatible tissue-specific plant transformation vectors. In this paper we aim to expand the toolkit of vectors available for Agrobacterium-mediated plant transformation and protoplast transfection.

Results

Here, we introduce new Agrobacterium-mediated plant transformation vectors by introducing additional fluorophores to create the pJRA vector series. Additionally, we introduce the pLCS series of vectors, a new set of modular Gateway- and Gibson assembly-compatible vectors designed for protoplast transfection. All described vectors are available from Addgene to serve as a resource for the plant research community.

A pH-Sensitive Fluorescent Chemosensor Turn-On Based in a Salen Iron (III) Complex: Synthesis, Photophysical Properties, and Live-Cell Imaging Application

pH regulation is essential to allow normal cell function, and their imbalance is associated with different pathologic situations, including cancer. In this study, we present the synthesis of 2-(((2-aminoethyl)imino)methyl)phenol (HL1) and the iron (III) complex (Fe(L1)2Br, (C1)), confirmed by X-ray diffraction analysis. The absorption and emission properties of complex C1 were assessed in the presence and absence of different physiologically relevant analytes, finding a fluorescent turn-on when OH- was added. So, we determined the limit of detection (LOD = 3.97 × 10-9 M), stoichiometry (1:1), and association constant (Kas = 5.86 × 103 M-1). Using DFT calculations, we proposed a spontaneous decomposition mechanism for C1. After characterization, complex C1 was evaluated as an intracellular pH chemosensor on the human primary gastric adenocarcinoma (AGS) and non-tumoral gastric epithelia (GES-1) cell lines, finding fluorescent signal activation in the latter when compared to AGS cells due to the lower intracellular pH of AGS cells caused by the increased metabolic rate. However, when complex C1 was used on metastatic cancer cell lines (MKN-45 and MKN-74), a fluorescent turn-on was observed in both cell lines because the intracellular lactate amount increased. Our results could provide insights about the application of complex C1 as a metabolic probe to be used in cancer cell imaging.

Characterization of the far-red fluorescent probe MitoView 633 for dynamic mitochondrial membrane potential measurement

Introduction: MitoView 633, a far-red fluorescent dye, exhibits the ability to accumulate within mitochondria in a membrane potential-dependent manner, as described by the Nernst equation. This characteristic renders it a promising candidate for bioenergetics studies, particularly as a robust indicator of mitochondrial membrane potential (DYm). Despite its great potential, its utility in live cell imaging has not been well characterized. Methods: This study seeks to characterize the spectral properties of MitoView 633 in live cells and evaluate its mitochondrial staining, resistance to photobleaching, and dynamics during DYm depolarization. The co-staining and imaging of MitoView 633 with other fluorophores such as MitoSOX Red and Fluo-4 AM were also examined in cardiomyocytes using confocal microscopy. Results and Discussion: Spectrum analysis showed that MitoView 633 emission could be detected at 660 ± 50 nm, and exhibited superior thermal stability compared to tetramethylrhodamine methyl ester (TMRM), a commonly used DYm indicator, which emits at 605 ± 25 nm. Confocal imaging unequivocally illustrated MitoView 633's specific localization within the mitochondrial matrix, corroborated by its colocalization with MitoTracker Green, a well-established mitochondrial marker. Furthermore, our investigation revealed that MitoView 633 exhibited minimal photobleaching at the recommended in vitro concentrations. Additionally, the dynamics of MitoView 633 fluoresce during carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP, a mitochondrial uncoupler)-induced DYm depolarization mirrored that of TMRM. Importantly, MitoView 633 demonstrated compatibility with co-staining alongside MitoSOX Red and Fluo-4 AM, enabling concurrent monitoring of DYm, mitochondrial ROS, and cytosolic Ca2+ in intact cells. Conclusion: These findings collectively underscore MitoView 633 as a superb molecular probe for the singular or combined assessment of DYm and other indicators in live cell imaging applications.

Insulin C-peptide secretion on-a-chip to measure the dynamics of secretion and metabolism from individual islets

First-phase glucose-stimulated insulin secretion is mechanistically linked to type 2 diabetes, yet the underlying metabolism is difficult to discern due to significant islet-to-islet variability. Here, we miniaturize a fluorescence anisotropy immunoassay onto a microfluidic device to measure C-peptide secretion from individual islets as a surrogate for insulin (InsC-chip). This method measures secretion from up to four islets at a time with ∼7 s resolution while providing an optical window for real-time live-cell imaging. Using the InsC-chip, we reveal two glucose-dependent peaks of insulin secretion (i.e., a double peak) within the classically defined 1st phase (<10 min). By combining real-time secretion and live-cell imaging, we show islets transition from glycolytic to oxidative phosphorylation (OxPhos)-driven metabolism at the nadir of the peaks. Overall, these data validate the InsC-chip to measure glucose-stimulated insulin secretion while revealing new dynamics in secretion defined by a shift in glucose metabolism.

NAP (Davunetide): The Neuroprotective ADNP Drug Candidate Penetrates Cell Nuclei Explaining Pleiotropic Mechanisms

(1) Background: Recently, we showed aberrant nuclear/cytoplasmic boundaries/activity-dependent neuroprotective protein (ADNP) distribution in ADNP-mutated cells. This malformation was corrected upon neuronal differentiation by the ADNP-derived fragment drug candidate NAP (davunetide). Here, we investigated the mechanism of NAP nuclear protection. (2) Methods: CRISPR/Cas9 DNA-editing established N1E-115 neuroblastoma cell lines that express two different green fluorescent proteins (GFPs)-labeled mutated ADNP variants (p.Tyr718* and p.Ser403*). Cells were exposed to NAP conjugated to Cy5, followed by live imaging. Cells were further characterized using quantitative morphology/immunocytochemistry/RNA and protein quantifications. (3) Results: NAP rapidly distributed in the cytoplasm and was also seen in the nucleus. Furthermore, reduced microtubule content was observed in the ADNP-mutated cell lines. In parallel, disrupting microtubules by zinc or nocodazole intoxication mimicked ADNP mutation phenotypes and resulted in aberrant nuclear-cytoplasmic boundaries, which were rapidly corrected by NAP treatment. No NAP effects were noted on ADNP levels. Ketamine, used as a control, was ineffective, but both NAP and ketamine exhibited direct interactions with ADNP, as observed via in silico docking. (4) Conclusions: Through a microtubule-linked mechanism, NAP rapidly localized to the cytoplasmic and nuclear compartments, ameliorating mutated ADNP-related deficiencies. These novel findings explain previously published gene expression results and broaden NAP (davunetide) utilization in research and clinical development.

Live imaging of the airway epithelium reveals that mucociliary clearance modulates SARS-CoV-2 spread

SARS-CoV-2 initiates infection in the conducting airways, which rely on mucocilliary clearance (MCC) to minimize pathogen penetration. However, it is unclear how MCC impacts SARS-CoV-2 spread after infection is established. To understand viral spread at this site, we performed live imaging of SARS-CoV-2 infected differentiated primary human bronchial epithelium cultures for up to 9 days. Fluorescent markers for cilia and mucus allowed longitudinal monitoring of MCC, ciliary motion, and infection. The number of infected cells peaked at 4 days post-infection in characteristic foci that followed mucus movement. Inhibition of MCC using physical and genetic perturbations limited foci. Later in infection, MCC was diminished despite relatively subtle ciliary function defects. Resumption of MCC and infection spread after mucus removal suggests that mucus secretion mediates this effect. We show that MCC facilitates SARS-CoV-2 spread early in infection while later decreases in MCC inhibit spread, suggesting a complex interplay between SARS-CoV-2 and MCC.

Probing archaeal cell biology: exploring the use of dyes in the imaging of Sulfolobus cells

Archaea are key players in many critical ecological processes. In comparison to eukaryotes and bacteria, however, our understanding of both the cell biology and diversity of archaea remains limited. While archaea inhabit a wide range of environmental conditions, many species are extremophiles, surviving in extreme temperature, salt or pH conditions, making their cell biology hard to study. Recently, our understanding of archaeal cell biology has been advanced significantly by the advent of live cell imaging in extremis as well as the development of genetic tools to exogenously express fluorescent proteins in some mesophilic archaeal model systems, e.g., Haloferax volcanii. However, for most archaeal species, especially thermophilic species or emerging model systems without well characterized genetic tools, live cell imaging remains dependent on fluorescent chemical probes to label and track the dynamics of living cells. While a wide range of fluorescent stains and markers that label different components of the cell are available commercially, their use has usually been optimized for use in a small number of eukaryotic cell systems. Here we report the successes and failures of the application of membrane, DNA, S-layer and cytoplasm markers in live cell imaging of archaea, as well as the optimization of fixation and immunolabelling approaches. We have applied these markers to the thermoacidophilic archaeon Sulfolobus acidocaldarius, but expect some to work in other archaeal species. Furthermore, those procedures that failed in S. acidocaldarius may still prove useful for imaging archaea that grow at a more neutral pH and/or at a less extreme temperature.

Monocyte-Derived Chicken Macrophages Exposed to Eimeria tenella Sporozoites Display Reduced Susceptibility to Invasion by Toxoplasma gondii Tachyzoite

Both Eimeria tenella and Toxoplasma gondii are common apicomplexan parasites in chickens. Host cell invasion by both protozoans includes gliding motility, host cell attachment and active penetration. Chicken macrophages as phagocytic cells participate in the innate host immune response against these two parasites. In this study, primary chicken monocyte-derived macrophages (MM) were infected with both pathogens to investigate mutual and host-parasite interactions. MM cultures were assigned to groups that were infected with E. tenella, T. gondii or both. In co-infected cultures, MM were first exposed to E. tenella sporozoites for 2 h. Afterwards, T. gondii tachyzoite infection was performed. Live-cell imaging was carried out to observe cell invasion and survival of T. gondii by single parasite tracking over a period of 20 h post infection (hpi). Quantitative analysis for parasite replication was performed by real-time quantitative PCR (qPCR) at 2, 6, 12 and 24 hpi. Overall, the ability of T. gondii to penetrate the cell membrane of the potential host cell was reduced, although high motility was displayed. We found that T. gondii tachyzoites adhered for more than 4 h to macrophages during early co-infection. qPCR results confirmed that significantly less T. gondii entered in E. tenella-activated MM at 2 hpi, and a reduced proportion of intracellular T. gondii survived and replicated in these cells at 24 hpi. We conclude that E. tenella modulates host cell responses to another apicomplexan agent, T. gondii, reducing active invasion and multiplication in chicken primary macrophages.

Organelle mapping in dendrites of human iPSC-derived neurons reveals dynamic functional dendritic Golgi structures

Secretory pathways within dendrites of neurons have been proposed for local transport of newly synthesized proteins. However, little is known about the dynamics of the local secretory system and whether the organelles are transient or stable structures. Here, we quantify the spatial and dynamic behavior of dendritic Golgi and endosomes during differentiation of human neurons generated from induced pluripotent stem cells (iPSCs). In early neuronal development, before and during migration, the entire Golgi apparatus transiently translocates from the soma into dendrites. In mature neurons, dynamic Golgi elements, containing cis and trans cisternae, are transported from the soma along dendrites, in an actin-dependent process. Dendritic Golgi outposts are dynamic and display bidirectional movement. Similar structures were observed in cerebral organoids. Using the retention using selective hooks (RUSH) system, Golgi resident proteins are transported efficiently into Golgi outposts from the endoplasmic reticulum. This study reveals dynamic, functional Golgi structures in dendrites and a spatial map for investigating dendrite trafficking in human neurons.

In vitro models to study natural killer cell dynamics in the tumor microenvironment

Immunotherapy is revolutionizing cancer therapy. The rapid development of new immunotherapeutic strategies to treat solid tumors is posing new challenges for preclinical research, demanding novel in vitro methods to test treatments. Such methods should meet specific requirements, such as enabling the evaluation of immune cell responses like cytotoxicity or cytokine release, and infiltration into the tumor microenvironment using cancer models representative of the original disease. They should allow high-throughput and high-content analysis, to evaluate the efficacy of treatments and understand immune-evasion processes to facilitate development of new therapeutic targets. Ideally, they should be suitable for personalized immunotherapy testing, providing information for patient stratification. Consequently, the application of in vitro 3-dimensional (3D) cell culture models, such as tumor spheroids and organoids, is rapidly expanding in the immunotherapeutic field, coupled with the development of novel imaging-based techniques and -omic analysis. In this paper, we review the recent advances in the development of in vitro 3D platforms applied to natural killer (NK) cell-based cancer immunotherapy studies, highlighting the benefits and limitations of the current methods, and discuss new concepts and future directions of the field.

Activity and Selectivity of Novel Chemical Metallic Complexes with Potential Anticancer Effects on Melanoma Cells

Human malignant melanoma cells from lymph node metastatic site (MeWo) were selected for testing several synthesized and purified silver(I) and gold(I) complexes stabilized by unsymmetrically substituted N-heterocyclic carbene (NHC) ligands, called L20 (N-methyl, N'-[2-hydroxy ethylphenyl]imidazol-2-ylide) and M1 (4,5-dichloro, N-methyl, N'-[2-hydroxy ethylphenyl]imidazol-2-ylide), having halogenide (Cl^- or I^-) or aminoacyl (Gly=N-(tert-Butoxycarbonyl)glycinate or Phe=(S)-N-(tert-Butoxycarbonyl)phenylalaninate) counterion. For AgL20, AuL20, AgM1 and AuM1, the Half-Maximal Inhibitory Concentration (IC₅₀) values were measured, and all complexes seemed to reduce cell viability more effectively than Cisplatin, selected as control. The complex named AuM1 was the most active just after 8 h of treatment at 5 μM, identified as effective growth inhibition concentration. AuM1 also showed a linear dose and time-dependent effect. Moreover, AuM1 and AgM1 modified the phosphorylation levels of proteins associated with DNA lesions (H2AX) and cell cycle progression (ERK). Further screening of complex aminoacyl derivatives indicated that the most powerful were those indicated with the acronyms: GlyAg, PheAg, AgL20Gly, AgM1Gly, AuM1Gly, AgL20Phe, AgM1Phe, AuM1Phe. Indeed, the presence of Boc-Glycine (Gly) and Boc-L-Phenylalanine (Phe) showed an improved efficacy of Ag main complexes, as well as that of AuM1 derivatives. Selectivity was further checked on a non-cancerous cell line, a spontaneously transformed aneuploid immortal keratinocyte from adult human skin (HaCaT). In such a case, AuM1 and PheAg complexes resulted as the most selective allowing HaCaT viability at 70 and 40%, respectively, after 48 h of treatment at 5 μM. The same complexes tested on 3D MeWo static culture induced partial spheroid disaggregation after 24 h of culture, with almost half of the cells dead.

The RHOA Mutation G17V Does Not Lead to Increased Migration of Human Malignant T Cells but Is Associated with Matrix Remodelling

Nodal T-follicular helper cell lymphoma, angioimmunoblastic-type (AITL), is characterized by constitutional symptoms, advanced-stage disease, and generalized lymphadenopathy. A genetic hallmark of this lymphoma is the frequent occurrence of the RHOA mutation G17V in neoplastic cells, which is observed in around 60% of patients. Because RHOA is involved in both T-cell receptor downstream signalling and cell migration, we hypothesized that the characteristic presentation of AITL could be the result of enhanced tumor cell migration. Therefore, this study aimed to elucidate the impact of the RHOA variant G17V on the migration of neoplastic T cells. We transfected the T-cell lymphoma cell lines HH and HuT78 to stably express the RHOA-G17V variant. RHOA-G17V-expressing T cells did not exhibit enhanced motility compared to empty-vector-transfected cells in microchannels, a 3D collagen gel, or primary human lymphatic tissue. Cells of the HH cell line expressing RHOA-G17V had an increased number of cells with cleaved collagen compared with the empty-vector-transfected cells. Therefore, we hypothesized that the early spread of AITL tumor cells may be related to remodelling of the extracellular matrix. Accordingly, we observed a significant negative correlation between the relative area of collagen in histological sections from 18 primary AITL and the allele frequency of the RHOA-G17V mutation. In conclusion, our results suggest that the characteristic presentation of AITL with early, widespread dissemination of lymphoma cells is not the result of an enhanced migration capacity due to the RHOA-G17V mutation; instead, this feature may rather be related to extracellular matrix remodelling.

Live cell imaging of DNA and RNA with fluorescent signal amplification and background reduction techniques

Illuminating DNA and RNA dynamics in live cell can elucidate their life cycle and related biochemical activities. Various protocols have been developed for labeling the regions of interest in DNA and RNA molecules with different types of fluorescent probes. For example, CRISPR-based techniques have been extensively used for imaging genomic loci. However, some DNA and RNA molecules can still be difficult to tag and observe dynamically, such as genomic loci in non-repetitive regions. In this review, we will discuss the toolbox of techniques and methodologies that have been developed for imaging DNA and RNA. We will also introduce optimized systems that provide enhanced signal intensity or low background fluorescence for those difficult-to-tag molecules. These strategies can provide new insights for researchers when designing and using techniques to visualize DNA or RNA molecules.

Multifaceted Chiral Probe 2,3-Dihydro-4-hydroxy-chromene Schiff Base in Detecting Cu2+ Ions, l-Histidine, and Indazole: Spectroscopic Investigation and Confocal and Live Cell Imaging

2,3-Dihydro-4-hydroxy-chromene-4(N)-ethyl thiosemicarbazone (probe F4) is used as a chemosensor, and it selectively detected Cu²⁺ ions among the metal ions by showing fluorescence "TURN ON" behavior. The stoichiometric binding of the probe with Cu²⁺ (CF4) was confirmed by Job's plot and mass spectroscopy. Further, CF4 was used as a sensor for the detection of l-amino acids and N-heterocyclic compounds. Among them, CF4 selectively detected l-histidine by showing fluorescence "TURN-OFF" behavior and selectively detected indazole by showing fluorescence "TURN-ON" behavior. These behaviors were further confirmed by in vivo live cell imaging studies by using Caenorhabditis elegans as a model. In vitro cytotoxicity was assayed for probe F4, complex CF4, and CF4 with l-histidine and indazole. The IC₅₀ concentration was used for confocal imaging studies by using the MDA-MB-231 cell line (breast cancer cell line).

Engineering Female Germline Stem Cells with Exocytotic Polymer Dots

Germline stem cells (GSCs) are the only cell population capable of passing genetic information to offspring, making them attractive targets in reproductive biology and fertility research. However, it is generally more difficult to introduce exogenous biomolecules into GSCs than other cell types, impeding the exploration and manipulation of these cells for biomedical purposes. Herein, semiconductor polymer dots (Pdots)-based nanocomplex Pdot-siRNA is developed and achieves effective knockdown of target genes in female germline stem cells (FGSCs). Advantage of high fluorescence brightness of Pdots is taken for comprehensive investigation of their cellular uptake, intracellular trafficking, and exocytosis in FGSCs. Importantly, Pdots show excellent biocompatibility and minimally disturb the differentiation of FGSCs. Intracellular Pdots escape from the lysosomes and undergo active exocytosis, which makes them ideal nanocarriers for bioactive cargos. Moreover, Pdot-siRNA can penetrate into 3D ovarian organoids derived from FGSCs and down-regulate the expression levels of target genes. This study investigates the interface between a type of theranostic nanoparticles and FGSCs for the first time and sheds light on the manipulation and medical application of FGSCs.

MAVS-Based Reporter Systems for Real-Time Imaging of EV71 Infection and Antiviral Testing

Enterovirus consists of a variety of viruses that could cause a wide range of illness in human. The pathogenesis of these viruses remains incompletely understood and no specific treatment is available. Better methods to study enterovirus infection in live cells will help us better understand the pathogenesis of these viruses and might contribute to antiviral development. Here in this study, we developed fluorescent cell-based reporter systems that allow sensitive distinction of individual cells infected with enterovirus 71 (EV71). More importantly, these systems could be easily used for live-cell imaging by monitoring viral-induced fluorescence translocation after EV71 infection. We further demonstrated that these reporter systems could be used to study other enterovirus-mediated MAVS cleavage and they are sensitive for antiviral activity testing. Therefore, integration of these reporters with modern image-based analysis has the potential to generate new insights into enterovirus infection and facilitate antiviral development.

Live Cell Imaging Reveals HBV Capsid Translocation from the Nucleus To the Cytoplasm Enabled by Cell Division

Hepatitis B virus (HBV) capsid assembly is traditionally thought to occur predominantly in the cytoplasm, where the virus gains access to the virion egress pathway. To better define sites of HBV capsid assembly, we carried out single cell imaging of HBV Core protein (Cp) subcellular trafficking over time under conditions supporting genome packaging and reverse transcription in Huh7 hepatocellular carcinoma cells. Time-course analyses including live cell imaging of fluorescently tagged Cp derivatives showed Cp to accumulate in the nucleus at early time points (~24 h), followed by a marked re-distribution to the cytoplasm at 48 to 72 h. Nucleus-associated Cp was confirmed to be capsid and/or high-order assemblages using a novel dual label immunofluorescence strategy. Nuclear-to-cytoplasmic re-localization of Cp occurred predominantly during nuclear envelope breakdown in conjunction with cell division, followed by strong cytoplasmic retention of Cp. Blocking cell division resulted in strong nuclear entrapment of high-order assemblages. A Cp mutant, Cp-V124W, predicted to exhibit enhanced assembly kinetics, also first trafficked to the nucleus to accumulate at nucleoli, consistent with the hypothesis that Cp's transit to the nucleus is a strong and constitutive process. Taken together, these results provide support for the nucleus as an early-stage site of HBV capsid assembly, and provide the first dynamic evidence of cytoplasmic retention after cell division as a mechanism underpinning capsid nucleus-to-cytoplasm relocalization. IMPORTANCE Hepatitis B virus (HBV) is an enveloped, reverse-transcribing DNA virus that is a major cause of liver disease and hepatocellular carcinoma. Subcellular trafficking events underpinning HBV capsid assembly and virion egress remain poorly characterized. Here, we developed a combination of fixed and long-term (>24 h) live cell imaging technologies to study the single cell trafficking dynamics of the HBV Core Protein (Cp). We demonstrate that Cp first accumulates in the nucleus, and forms high-order structures consistent with capsids, with the predominant route of nuclear egress being relocalization to the cytoplasm during cell division in conjunction with nuclear membrane breakdown. Single cell video microscopy demonstrated unequivocally that Cp's localization to the nucleus is constitutive. This study represents a pioneering application of live cell imaging to study HBV subcellular transport, and demonstrates links between HBV Cp and the cell cycle.

Boron Dopants in Red-Emitting B and N Co-Doped Carbon Quantum Dots Enable Targeted Imaging of Lysosomes

Lysosomes are of great significance to cell growth, metabolism, and survival, as they independently maintain acidity and regulate various balances in cells. Therefore, it is essential to develop advanced probes for lysosome visualization and live tracking. Herein, a type of lysosome-targeting probe based on boron (B) and nitrogen (N) co-doped carbon quantum dots (B/N-CQDs) is presented, which exhibits red emission at 618 nm, high quantum yield (28%), and excellent fluorescence stability (97% at 1 h). These B/N-CQDs are prepared by a novel and green solid-state reaction and purified using a simple extraction process without additional chemical modifications. It is found that the boron dopants in the structure play a crucial role in the resultant lysosome-specific targeting property through borate esterification between boronic acid groups in the sample and diol structures in glycoproteins. This can be applied as a powerful tool for cell apoptosis, necrosis, and endosomal escape tracking. This work not only offers a new concept for targeted subcellular probe designs via chemical doping but also demonstrates the feasibility of these tools for analyzing complex cellular physiological activities.

Label-Free Long-Term Methods for Live Cell Imaging of Neurons: New Opportunities

Time-lapse light microscopy combined with in vitro neuronal cultures has provided a significant contribution to the field of Developmental Neuroscience. The establishment of the neuronal polarity, i.e., formation of axons and dendrites, key structures responsible for inter-neuronal signaling, was described in 1988 by Dotti, Sullivan and Banker in a milestone paper that continues to be cited 30 years later. In the following decades, numerous fluorescently labeled tags and dyes were developed for live cell imaging, providing tremendous advancements in terms of resolution, acquisition speed and the ability to track specific cell structures. However, long-term recordings with fluorescence-based approaches remain challenging because of light-induced phototoxicity and/or interference of tags with cell physiology (e.g., perturbed cytoskeletal dynamics) resulting in compromised cell viability leading to cell death. Therefore, a label-free approach remains the most desirable method in long-term imaging of living neurons. In this paper we will focus on label-free high-resolution methods that can be successfully used over a prolonged period. We propose novel tools such as scanning ion conductance microscopy (SICM) or digital holography microscopy (DHM) that could provide new insights into live cell dynamics during neuronal development and regeneration after injury.

Simultaneous Measurement of Changes in Mitochondrial and Endoplasmic Reticulum Free Calcium in Pancreatic Beta Cells

The free calcium (Ca2+) levels in pancreatic beta cell organelles have been the subject of many recent investigations. Under pathophysiological conditions, disturbances in these pools have been linked to altered intracellular communication and cellular dysfunction. To facilitate studies of subcellular Ca2+ signaling in beta cells and, particularly, signaling between the endoplasmic reticulum (ER) and mitochondria, we designed a novel dual Ca2+ sensor which we termed DS-1. DS-1 encodes two stoichiometrically fluorescent proteins within a single plasmid, G-CEPIA-er, targeted to the ER and R-CEPIA3-mt, targeted to mitochondria. Our goal was to simultaneously measure the ER and mitochondrial Ca2+ in cells in real time. The Kds of G-CEPIA-er and R-CEPIA3-mt for Ca2+ are 672 and 3.7 μM, respectively. Confocal imaging of insulin-secreting INS-1 832/13 expressing DS-1 confirmed that the green and red fluorophores correctly colocalized with organelle-specific fluorescent markers as predicted. Further, we tested whether DS-1 exhibited the functional properties expected by challenging an INS-1 cell to glucose concentrations or drugs having well-documented effects on the ER and mitochondrial Ca2+ handling. The data obtained were consistent with those seen using other single organelle targeted probes. These results taken together suggest that DS-1 is a promising new approach for investigating Ca2+ signaling within multiple organelles of the cell.

Quantitative DNA-PAINT imaging of AMPA receptors in live neurons

DNA-point accumulation for imaging at nanoscale topography (DNA-PAINT) can image fixed biological specimens with nanometer resolution and absolute stoichiometry. In living systems, however, the usage of DNA-PAINT has been limited due to high salt concentration in the buffer required for specific binding of the imager to the docker attached to the target. Here, we used multiple binding motifs of the docker, from 2 to 16, to accelerate the binding speed of the imager under physiological buffer conditions without compromising spatial resolution and maintaining the basal level homeostasis during the measurement. We imaged endogenous α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in cultured neurons-critical proteins involved in nerve communication-by DNA-PAINT in 3-dimensions using a monovalent single-chain variable fragment (scFv) to the GluA1 subunit of AMPAR. We found a heterogeneous distribution of synaptic AMPARs: ≈60% are immobile, primarily in nanodomains, defined as AMPARs that are within 0.3 μm of the Homer1 protein in the postsynaptic density; the other ∼40% of AMPARs have restricted mobility and trajectory.

High-speed 2D light-sheet fluorescence microscopy enables quantification of spatially varying calcium dynamics in ventricular cardiomyocytes

Introduction: Reduced synchrony of calcium release and t-tubule structure organization in individual cardiomyocytes has been linked to loss of contractile strength and arrhythmia. Compared to confocal scanning techniques widely used for imaging calcium dynamics in cardiac muscle cells, light-sheet fluorescence microscopy enables fast acquisition of a 2D plane in the sample with low phototoxicity. Methods: A custom light-sheet fluorescence microscope was used to achieve dual-channel 2D timelapse imaging of calcium and the sarcolemma, enabling calcium sparks and transients in left and right ventricle cardiomyocytes to be correlated with the cell microstructure. Imaging electrically stimulated dual-labelled cardiomyocytes immobilized with para-nitroblebbistatin, a non-phototoxic, low fluorescence contraction uncoupler, with sub-micron resolution at 395 fps over a 38 μm × 170 µm FOV allowed characterization of calcium spark morphology and 2D mapping of the calcium transient time-to-half-maximum across the cell. Results: Blinded analysis of the data revealed sparks with greater amplitude in left ventricle myocytes. The time for the calcium transient to reach half-maximum amplitude in the central part of the cell was found to be, on average, 2 ms shorter than at the cell ends. Sparks co-localized with t-tubules were found to have significantly longer duration, larger area and spark mass than those further away from t-tubules. Conclusion: The high spatiotemporal resolution of the microscope and automated image-analysis enabled detailed 2D mapping and quantification of calcium dynamics of n = 60 myocytes, with the findings demonstrating multi-level spatial variation of calcium dynamics across the cell, supporting the dependence of synchrony and characteristics of calcium release on the underlying t-tubule structure.

IL18 Receptor Signaling Inhibits Intratumoral CD8+ T-Cell Migration in a Murine Pancreatic Cancer Model

In pancreatic ductal adenocarcinoma (PDAC), the infiltration of CD8⁺ cytotoxic T cells (CTLs) is an important factor in determining prognosis. The migration pattern and interaction behavior of intratumoral CTLs are pivotal to tumor rejection. NLRP3-dependent proinflammatory cytokines IL-1β and IL-18 play a prominent role for CTL induction and differentiation. Here, we investigate the effects of T-cellular IL-1R and IL-18R signaling for intratumoral T-cell motility. Murine adenocarcinoma cell line Panc02 was stably transfected with ovalbumin (OVA) and fluorophore H2B-Cerulean to generate PancOVA H2B-Cerulean tumor cells. Dorsal skinfold chambers (DSFC) were installed on wild-type mice, and PancOVA H2B-Cerulean tumor cells were implanted into the chambers. PancOVA spheroids were formed using the Corning^® Matrigel^®-based 3D cell culture technique. CTLs were generated from OT-1 mice, Il1r^-/- OT-1 mice, or Il18r^-/- OT-1 mice and were marked with fluorophores. This was followed by the adoptive transfer of CTLs into tumor-bearing mice or the application into tumor spheroids. After visualization with multiphoton microscopy (MPM), Imaris software was used to perform T-cell tracking. Imaris analysis indicates a significantly higher accumulation of Il18r^-/- CTLs in PancOVA tumors and a significant reduction in tumor volume compared to wild-type CTLs. Il18r^-/- CTLs covered a longer distance (track displacement length) in comparison to wild-type (WT) CTLs, and had a higher average speed (mean track speed). The analysis of instantaneous velocity suggests a higher percentage of arrested tracks (arrests: <4 μm/min) for Il18r^-/- CTLs. Our data indicate the contribution of IL-18R signaling to T-cell effector strength, warranting further investigation on phenomena such as intratumoral T-cell exhaustion.

Dendrimer-like Hierarchical Framework Nucleic Acid for Real-Time Imaging of Intracellular Trafficking

Framework nucleic acids (FNAs) represent a new type of DNA-based nanomaterials and possess great potentials in biosensing, bioimaging, and molecular delivery. Hierarchical DNA nanostructures that consist of multiple FNA monomers increase the capacity for drug delivery and multifunctional modification. However, there are relatively few studies devoted to the behavior and regulation of hierarchical FNAs in living cells, impeding their further applications. Herein, we constructed a dendritic nanostructure with five tetrahedral DNA nanocages and characterized the real-time internalization, inter-organelle trafficking, and exocytosis in living mammalian cells. In comparison to FNA monomers, FNA dendrimers exhibit increased endocytosis and prolonged cellular retention. Single-particle tracking on hundreds of FNA dendrimers exhibits no interference on the mobility or kinetics of subcellular organelles, implying that FNAs as well as their higher-order derivatives are ideal intracellular imaging probes and nanocarriers. Our study validates the suitability and superiority of hierarchical DNA nanostructures as high-valency scaffolds for biomedical applications.

Corrigendum: Effects of extracellular adhesion molecules on immune cell mediated solid tumor cell killing

[This corrects the article DOI: 10.3389/fimmu.2022.1004171.].

An approach for live imaging of first cleavage in mouse embryos using fluorescent chemical probes for DNA, microtubules, and microfilaments

Purpose

Dynamic morphological changes in the chromosome and cytoskeleton occur in mammals and humans during early embryonic development, and abnormalities such as embryonic chromosomal aneuploidy occur when development does not proceed normally. Visualization of the intracellular organelles and cytoskeleton allows elucidation of the development of early mammalian embryos. The behavior of the DNA and cytoskeleton in early mammalian embryos has conventionally been observed by injecting target molecule mRNAs, incorporating a fluorescent substance-expressing gene, into embryos. In this study, we visualized the chronological behavior of male and female chromosome condensation in mouse embryos, beginning in the two-pronuclear zygote, through the first division to the two-cell stage, using fluorescent chemical probes to visualize the behavior of DNA, microtubules, and microfilaments.

Method

Mouse two-pronuclear stage embryo were immersed in medium containing fluorescent chemical probes to visualize DNA, microtubules, and microfilaments. Observation was performed with a confocal microscope.

Results

This method allowed us to observe how chromosome segregation errors in first somatic cell divisions in mouse embryos and enabled dynamic analysis of a phenomenon called lagging chromosomes.

Conclusions

By applying this method, we can observe any stage of embryonic development, which may provide new insights into embryonic development in other mammals.