Proper positioning of organelles by cytoskeleton-based motor proteins underlies cellular events such as signalling, polarization and growth. For many organelles, however, the precise connection ...between position and function has remained unclear, because strategies to control intracellular organelle positioning with spatiotemporal precision are lacking. Here we establish optical control of intracellular transport by using light-sensitive heterodimerization to recruit specific cytoskeletal motor proteins (kinesin, dynein or myosin) to selected cargoes. We demonstrate that the motility of peroxisomes, recycling endosomes and mitochondria can be locally and repeatedly induced or stopped, allowing rapid organelle repositioning. We applied this approach in primary rat hippocampal neurons to test how local positioning of recycling endosomes contributes to axon outgrowth and found that dynein-driven removal of endosomes from axonal growth cones reversibly suppressed axon growth, whereas kinesin-driven endosome enrichment enhanced growth. Our strategy for optogenetic control of organelle positioning will be widely applicable to explore site-specific organelle functions in different model systems.
Ionizing radiation (IR) is effectively used in cancer therapy. However, in subsets of patients, a few radioresistant cancer cells survive and cause disease relapse with metastatic progression. The ...MET oncogene encodes the hepatocyte growth factor (HGF) receptor and is known to drive "invasive growth", a regenerative and prosurvival program unduly activated in metastasis.
Human tumor cell lines (MDA-MB-231, MDA-MB-435S, U251) were subjected to therapeutic doses of IR. MET mRNA, and protein expression and signal transduction were compared in treated and untreated cells, and the involvement of the DNA-damage sensor ataxia telangiectasia mutated (ATM) and the transcription factor nuclear factor kappa B (NF-κB) in activating MET transcription were analyzed by immunoblotting, chromatin immunoprecipitation, and use of NF-κB silencing RNA (siRNA). Cell invasiveness was measured in wound healing and transwell assays, and cell survival was measured in viability and clonogenic assays. MET was inhibited by siRNA or small-molecule kinase inhibitors (PHA665752 or JNJ-38877605). Combinations of MET-targeted therapy and radiotherapy were assessed in MDA-MB-231 and U251 xenografts (n = 5-6 mice per group). All P values were from two-sided tests.
After irradiation, MET expression in cell lines was increased up to fivefold via activation of ATM and NF-κB. MET overexpression increased ligand-independent MET phosphorylation and signal transduction, and rendered cells more sensitive to HGF. Irradiated cells became more invasive via a MET-dependent mechanism that was further enhanced in the presence of HGF. MET silencing by siRNA or inhibition of its kinase activity by treatment with PHA665752 or JNJ-38877605 counteracted radiation-induced invasiveness, promoted apoptosis, and prevented cells from resuming proliferation after irradiation in vitro. Treatment with MET inhibitors enhanced the efficacy of IR to stop the growth of or to induce the regression of xenografts (eg, at day 13, U251 xenografts, mean volume increase relative to mean tumor volume at day 0: vehicle = 438%, 5 Gy IR = 151%, 5 Gy IR + JNJ-38877605 = 76%; difference, IR vs JNJ-38877604 + IR = 75%, 95% CI = 59% to 91%, P = .01).
IR induces overexpression and activity of the MET oncogene through the ATM-NF-κB signaling pathway; MET, in turn, promotes cell invasion and protects cells from apoptosis, thus supporting radioresistance. Drugs targeting MET increase tumor cell radiosensitivity and prevent radiation-induced invasiveness.
Telomeres are essential for genome stability. Oxidative stress caused by excess reactive oxygen species (ROS) accelerates telomere shortening. Although telomeres are hypersensitive to ROS-mediated ...8-oxoguanine (8-oxoG) formation, the biological effect of this common lesion at telomeres is poorly understood because ROS have pleiotropic effects. Here we developed a chemoptogenetic tool that selectively produces 8-oxoG only at telomeres. Acute telomeric 8-oxoG formation increased telomere fragility in cells lacking OGG1, the enzyme that removes 8-oxoG, but did not compromise cell survival. However, chronic telomeric 8-oxoG induction over time shortens telomeres and impairs cell growth. Accumulation of telomeric 8-oxoG in chronically exposed OGG1-deficient cells triggers replication stress, as evidenced by mitotic DNA synthesis at telomeres, and significantly increases telomere losses. These losses generate chromosome fusions, leading to chromatin bridges and micronucleus formation upon cell division. By confining base damage to the telomeres, we show that telomeric 8-oxoG accumulation directly drives telomere crisis.
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•Targeted chronic 8-oxoG damage at telomeres promotes telomere shortening•Unrepaired telomeric 8-oxoG in OGG1-deficient cells impairs telomere replication•8-oxoG-induced telomere losses cause dicentric chromosomes and anaphase bridges•Persistent telomeric 8-oxoG drives telomere crisis and global genomic instability
Chronic oxidative stress accelerates telomere shortening, thought to result from telomeric DNA damage. By developing a tool to selectively target 8-oxoguanine damage to telomeres, Fouquerel et al. demonstrate that this DNA lesion directly drives telomere shortening and impairs replication. Lesion-induced telomere losses promote chromosome fusions and overall genomic instability.
Cellular fate decisions are influenced by their topographical location in the adult body. For instance, tissue repair and neoplastic growth are greater in anterior than in posterior regions of adult ...animals. However, the molecular underpinnings of these regional differences are unknown. We identified a regional switch in the adult planarian body upon systemic disruption of homologous recombination with RNA-interference of Rad51 Rad51 knockdown increases DNA double-strand breaks (DSBs) throughout the body, but stem cells react differently depending on their location along the anteroposterior axis. In the presence of extensive DSBs, cells in the anterior part of the body resist death, whereas cells in the posterior region undergo apoptosis. Furthermore, we found that proliferation of cells with DNA damage is induced in the presence of brain tissue and that the retinoblastoma pathway enables overproliferation of cells with DSBs while attending to the demands of tissue growth and repair. Our results implicate both autonomous and non-autonomous mechanisms as key mediators of regional cell behavior and cellular transformation in the adult body.
In nature, plants are challenged by constantly changing light conditions. To reveal the molecular mechanisms behind acclimation to sometimes drastic and frequent changes in light intensity, we grew ...Arabidopsis thaliana under fluctuating light conditions, in which the low light periods were repeatedly interrupted with high light peaks. Such conditions had only marginal effect on photosystem II but induced damage to photosystem I (PSI), the damage being most severe during the early developmental stages. We showed that PROTON GRADIENT REGULATIONS (PGR5)—dependent regulation of electron transfer and proton motive force is crucial for protection of PSI against photodamage, which occurred particularly during the high light phases of fluctuating light cycles. Contrary to PGR5, the NAD(P)H dehydrogenase complex, which mediates cyclic electron flow around PSI, did not contribute to acclimation of the photosynthetic apparatus, particularly PSI, to rapidly changing light intensities. Likewise, the Arabidopsis pgr5 mutant exhibited a significantly higher mortality rate compared with the wild type under outdoor field conditions. This shows not only that regulation of PSI under natural growth conditions is crucial but also the importance of PGR5 in PSI protection.
We report an optogenetic method based on Arabidopsis thaliana cryptochrome 2 for rapid and reversible protein oligomerization in response to blue light. We demonstrated its utility by photoactivating ...the β-catenin pathway, achieving a transcriptional response higher than that obtained with the natural ligand Wnt3a. We also demonstrated the modularity of this approach by photoactivating RhoA with high spatiotemporal resolution, thereby suggesting a previously unknown mode of activation for this Rho GTPase.
Singlet oxygen (1O2) signalling in plants is essential to trigger both acclimatory mechanisms and programmed cell death under high light stress. However, because of its chemical features, 1O2 ...requires mediators, and the players involved in this pathway are largely unknown. The β‐carotene oxidation product, β‐cyclocitral, is one such mediator. Produced in the chloroplast, β‐cyclocitral induces changes in nuclear gene expression leading to photoacclimation. Recently, the METHYLENE BLUE SENSITIVITY protein MBS has been identified as a key player in 1O2 signalling leading to tolerance to high light. Here, we provide evidence that MBS1 is essential for acclimation to 1O2 and cross‐talks with β‐cyclocitral to mediate transfer of the 1O2 signal to the nucleus, leading to photoacclimation. The presented results position MBS1 downstream of β‐cyclocitral in 1O2 signalling and suggest an additional role for MBS1 in the regulation of plant growth and development under chronic 1O2 production.
In this work, we show that the MBS1 gene (METHYLENE BLUE SENSITIVITY 1) is required for the tolerance of the 1O2‐overproducing Arabidopsis mutant ch1 to photooxidative stress: the ch1 mbs1 double mutant lost its capacity to acclimate to 1O2. Moreover, introduction of the mbs1 mutation in the ch1 genetic background resulted in a marked growth phenotype in low light, indicating an additional role for MBS1 in the regulation of 1O2 signalling which controls growth and development. Exposing Arabidopsis plants to high light or to the signal molecule β‐cyclocitral induced accumulation of the MBS1 protein. Mutational suppression of MBS1 inhibited the effects of β‐cyclocitral on gene expressions and the associated phototolerance. We have thus identified the first downstream partner in the β‐cyclocitral‐mediated 1O2 signalling pathway in plants.
The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant ...photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the function of optical power limiting. All known mechanisms of optical limiting have been analyzed and discussed for the different types of materials.
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•Sonication-assisted deposition-precipitation and hydrothermal method have been used to fabricate AgI/g-C3N4 nanocomposites.•Different preparation procedures affected the morphology, ...purity, and size of the product.•The as-prepared AgI/g-C3N4 nanocomposites possessed higher photocatalytic activity than the pure AgI and g-C3N4.•AgI/g-C3N4 nanocomposites could be a great antimicrobial agent.
Silver iodide/graphitic carbon nitride nanocomposites have been successfully fabricated through sonication-assisted deposition-precipitation route at room temperature and hydrothermal method. Varied mass ratios and preparation processes can modify the structure, purity, shape, and scale of specimens. The purity of the product was confirmed by Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray crystallography. The morphology and size of specimens could be observed with transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The bandgap was evaluated around 2.82 eV for pure g-C3N4. The bandgap has reduced to 2.70 eV by increasing the quantity of silver iodide in the nanocomposites. The photocatalytic activity of AgI/C3N4 has been studied over the destruction of rhodamine B (RhB) and methyl orange (MO) through visible radiation due to their suitable bandgap. The as-prepared AgI/C3N4 nanocomposites photocatalyst revealed better photocatalytic behavior than the genuine AgI and C3N4 which ascribed to synergic impacts at the interconnection of C3N4 and AgI. Furthermore, these nanocomposites have great potential for being a great antibacterial agent.
Group 3 innate lymphoid cells (ILC3s) are major regulators of inflammation, infection, microbiota composition and metabolism
. ILC3s and neuronal cells have been shown to interact at discrete mucosal ...locations to steer mucosal defence
. Nevertheless, it is unclear whether neuroimmune circuits operate at an organismal level, integrating extrinsic environmental signals to orchestrate ILC3 responses. Here we show that light-entrained and brain-tuned circadian circuits regulate enteric ILC3s, intestinal homeostasis, gut defence and host lipid metabolism in mice. We found that enteric ILC3s display circadian expression of clock genes and ILC3-related transcription factors. ILC3-autonomous ablation of the circadian regulator Arntl led to disrupted gut ILC3 homeostasis, impaired epithelial reactivity, a deregulated microbiome, increased susceptibility to bowel infection and disrupted lipid metabolism. Loss of ILC3-intrinsic Arntl shaped the gut 'postcode receptors' of ILC3s. Strikingly, light-dark cycles, feeding rhythms and microbial cues differentially regulated ILC3 clocks, with light signals being the major entraining cues of ILC3s. Accordingly, surgically or genetically induced deregulation of brain rhythmicity led to disrupted circadian ILC3 oscillations, a deregulated microbiome and altered lipid metabolism. Our work reveals a circadian circuitry that translates environmental light cues into enteric ILC3s, shaping intestinal health, metabolism and organismal homeostasis.
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