Bacterial gasdermins reveal an ancient mechanism of cell death

Ancient origin of cell death Gasdermins are cell death proteins in mammals that form membrane pores in response to pathogen infection. Johnson et al . report that diverse bacteria encode structural and functional homologs of mammalian gasdermins. Like their mammalian counterparts, bacterial gasdermins are activated by caspase-like proteases, oligomerize into large membrane pores, and defend against pathogen—in this case, bacteriophage—infection. Proteolytic activation occurs through the release of a short inhibitory peptide, and many bacterial gasdermins are lipidated to facilitate membrane pore formation. Pyroptotic cell death, a central component of mammalian innate immunity, thus has a shared origin with an ancient antibacteriophage defense system. —SMH

Hydrophilic nanoparticles that kill bacteria while sparing mammalian cells reveal the antibiotic role of nanostructures

To dissect the antibiotic role of nanostructures from chemical moieties belligerent to both bacterial and mammalian cells, here we show the antimicrobial activity and cytotoxicity of nanoparticle-pinched polymer brushes (NPPBs) consisting of chemically inert silica nanospheres of systematically varied diameters covalently grafted with hydrophilic polymer brushes that are non-toxic and non-bactericidal. Assembly of the hydrophilic polymers into nanostructured NPPBs doesn’t alter their amicability with mammalian cells, but it incurs a transformation of their antimicrobial potential against bacteria, including clinical multidrug-resistant strains, that depends critically on the nanoparticle sizes. The acquired antimicrobial potency intensifies with small nanoparticles but subsides quickly with large ones. We identify a threshold size (dsilica ~ 50 nm) only beneath which NPPBs remodel bacteria-mimicking membrane into 2D columnar phase, the epitome of membrane pore formation. This study illuminates nanoengineering as a viable approach to develop nanoantibiotics that kill bacteria upon contact yet remain nontoxic when engulfed by mammalian cells.

Membrane interactions and uncoating of Aichi virus, a picornavirus that lacks a VP4

Kobuviruses are an unusual and poorly characterised genus within the picornavirus family, and can cause gastrointestinal enteric disease in humans, livestock and pets. The human Kobuvirus, Aichi virus (AiV) can cause severe gastroenteritis and deaths in children below the age of five years, however this is a very rare occurrence. During the assembly of most picornaviruses (e.g. poliovirus, rhinovirus and foot-and-mouth disease virus), the capsid precursor protein VP0 is cleaved into VP4 and VP2. However, Kobuviruses retain an uncleaved VP0. From studies with other picornaviruses, it is known that VP4 performs the essential function of pore formation in membranes, which facilitates transfer of the viral genome across the endosomal membrane and into the cytoplasm for replication. Here, we employ genome exposure and membrane interaction assays to demonstrate that pH plays a critical role in AiV uncoating and membrane interactions. We demonstrate that incubation at low pH alters the exposure of hydrophobic residues within the capsid, enhances genome exposure and enhances permeabilisation of model membranes. Furthermore, using peptides we demonstrate that the N-terminus of VP0 mediates membrane pore formation in model membranes, indicating that this plays an analogous function to VP4. Importance: To initiate infection, viruses must enter a host cell and deliver their genome into the appropriate location. The picornavirus family of small non-enveloped RNA viruses includes significant human and animal pathogens and are also models to understand the process of cell entry. Most picornavirus capsids contain the internal protein VP4, generated from cleavage of a VP0 precursor. During entry, VP4 is released from the capsid. In enteroviruses this forms a membrane pore, which facilitates genome release into the cytoplasm. Due to high levels of sequence similarity, it is expected to play the same role for other picornaviruses. Some picornaviruses, such as Aichi virus, retain an intact VP0, and it is unknown how these viruses re-arrange their capsids and induce membrane permeability in the absence of VP4. Here we have used Aichi virus as a model VP0 virus to test for conservation of function between VP0 and VP4. This could enhance understanding of pore function and lead to development of novel therapeutic agents that block entry.

P2X7 receptor: the regulator of glioma tumor development and survival

P2X7 is an ionotropic nucleotide receptor, forming the cation channel upon ATP stimulation. It can also function as a large membrane pore as well as transmit ATP-dependent signal without forming a channel at all. P2X7 activity in somatic cells is well-known, but remains poorly studied in glioma tumors. The current paper presents the comprehensive study of P2X7 activity in C6 and glioma cell line showing the wide range of effects the receptor has on glioma biology. We observed that P2X7 stimulation boosts glioma cell proliferation and increases cell viability. P2X7 activation promoted cell adhesion, mitochondria depolarization, and reactive oxygen species overproduction in C6 cells. P2X7 receptor also influenced glioma tumor growth in vivo via activation of pro-survival signaling pathways and ATP release. Treatment with Brilliant Blue G, a selective P2X7 antagonist, effectively inhibited glioma tumor development; decreased the expression of negative prognostic cancer markers pro-survival and epithelial-mesenchymal transition (EMT)-related proteins; and modulated the immune response toward glioma tumor in vivo. Finally, pathway-specific enrichment analysis of the microarray data from human patients also showed an upregulation of P2X7 receptor in gliomas from grades I to III. The presented results shed more light on the role of P2X7 receptor in the biology of this disease.

Temperature Impact on Reverse Osmosis Permeate Flux in the Remediation of Hexavalent Chromium

Reverse osmosis technique was applied in removing hexavalent chromium ions from artificial wastewater. Different operating conditions were studied to monitor the separation process using commercial Reverse Osmosis BW30XFR membrane. Different concentrations of hexavalent chromium; 5, 30, and 100 ppm were tested. Samples were subjected to incrementally increasing operating pressure; 10, 30, and 45 bar and flow rates; 2.2, 3.4, and 4.5 L/min under various temperatures; 25, 35, 45, and 55 °C. Collected permeate and concentrations were measured after each experiment using a UV spectrophotometer. Results obtained presented a higher rejection percentage at lower feed concentrations with a value up to 99.8% for 5 ppm in comparison to 94.3% for 30 ppm and 77.2% for 100 ppm concentration due to concentration polarization; however, it showed no effect of increasing operating flow rates. Moreover, the increase in feed temperature from 25 to 55 °C had positively increased permeate flux to more than 300 times. The permeate flux at 25 °C is recorded for all tested samples in the range of 30 to 158 kg/h·m2, this range has risen at 55 °C under the same conditions to the range of 70 to 226 kg/h·m2, indicating alteration within the membrane pore size due to temperature increase and high applied pressure concluding high sensitivity of polymeric membranes towards changing permeate flow rate with increasing temperatures.

High dilution of Belladonna affect the mycelial growth of Corynespora cassiicola in vitro

Introduction: The target spot is a disease caused by fungus Corynespora cassiicola (Berk. & Curt.) Wei. This disease has occurred in several states of Brazil. It is a late season disease and causes economic losses in various crops such as soybeans [1]. Currently there is no adequate treatment for the control of C. cassiicola in organic cultivation of soybeans, since the application of fungicides for the control and management of diseases is not allowed by Brazilian legislation [2]. Thus, the purpose of this experiment was to test the effectiveness of high dilutions of Belladonna in vitro on mycelial growth of Corynespora cassiicola. Materials and Methods: The preliminary tests were conducted at the Laboratory of Plant Pathology, State University of Maringá (UEM). The fungal isolate of C. cassicola was obtained from Embrapa Soja. The fungus was peaked and grown on PDA (potato dextrose agar) maintained at 25°C ± 2 and 12h photoperiod. Belladonna dilutions (6, 12, 18, 24 and 30dH) were obtained according to the Brazilian Homeopathic Pharmacopoeia [3]. PDA culture medium plus Belladonna dilutions (6, 12, 24 and 30dH) beyond the control containing distilled water were placed in petri dishes after filtration through a Millipore membrane (pore diameter of 0.45µm ). After medium solidification, a disc of mycelium (4 mm diameter) of C. cassiicola was peaked towards the center of each plate and sealed with plastic wrap and then incubated at 25°C with 12h photoperiod. The mycelial growth was measured daily for 8 days. The control consisted of distilled water. The data were analyzed by ANOVA and means were compared by Scott-Knott test (P ≤ 0.05). Results and Discussion: All dilutions of Belladonna (6, 12, 24, 30dH) were effective (p

Differential requirement for the EDS1 catalytic triad in A. thaliana and N. benthamiana

- Heterodimeric complexes incorporating the lipase-like proteins EDS1 with PAD4 or SAG101 are central hubs in plant innate immunity. EDS1 functions encompass signal relay from TIR domain-containing intracellular NLR-type immune receptors (TNLs) towards RPW8-type helper NLRs (RNLs) and, in A. thaliana, bolstering of signaling and resistance mediated by cell-surface pattern recognition receptors (PRRs). Biochemical activities underlying these mechanistic frameworks remain unknown. - We used CRISPR/Cas-generated mutant lines and agroinfiltration-based complementation assays to interrogate functions of EDS1 complexes in N. benthamiana. - We do not detect impaired PRR signaling in N. benthamiana lines deficient in EDS1 complexes or RNLs. Intriguingly, mutations within the catalytic triad of Solanaceae EDS1 can abolish or enhance TNL immunity in N. benthamiana. Furthermore, nuclear EDS1 accumulation is sufficient for N. benthamiana TNL (Roq1) immunity. - Reinforcing PRR signaling in Arabidopsis might be a derived function of the TNL/EDS1 immune sector. Dependency of Solanaceae but not A. thaliana EDS1 on catalytic triad residues raises the possibility that a TNL-derived small molecule binds to the Solanaceae EDS1 lipase-like domain, and that EDS1 lipase-like domain pocket contributions to TNL immune responses vary between lineages. Whether and how nuclear EDS1 activity connects to membrane pore-forming RNLs remains unknown.