The Antiviral Effector IFITM3 Disrupts Intracellular Cholesterol Homeostasis to Block Viral Entry

SummaryVesicle-membrane-protein-associated protein A (VAPA) and oxysterol-binding protein (OSBP) regulate intracellular cholesterol homeostasis, which is required for many virus infections. During entry, viruses or virus-containing vesicles can fuse with endosomal membranes to mediate the cytosolic release of virions, and alterations in endosomal cholesterol can inhibit this invasion step. We show that the antiviral effector protein interferon-inducible transmembrane protein 3 (IFITM3) interacts with VAPA and prevents its association with OSBP, thereby disrupting intracellular cholesterol homeostasis and inhibiting viral entry. By altering VAPA-OSBP function, IFITM3 induces a marked accumulation of cholesterol in multivesicular bodies and late endosomes, which inhibits the fusion of intraluminal virion-containing vesicles with endosomal membranes and thereby blocks virus release into the cytosol. Consequently, ectopic expression or depletion of the VAPA gene profoundly affects IFITM3-mediated inhibition of viral entry. Thus, IFITM3 disrupts intracellular cholesterol homeostasis to block viral entry, further underscoring the importance of cholesterol in virus infection

Enhanced antibacterial activity of streptomycin against some human pathogens using green synthesized silver nanoparticles

AbstractThe development of eco-friendly technologies in nanoparticle synthesis is of utmost importance in order to expand their biological horizons. In the present study, bioreduction of AgNO3 into AgNPs using various leaf extracts of Ficus virens is explained. The resulting AgNPs were characterized by UV–vis spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Synthesis of AgNPs was confirmed by color change from transparent to brown with maximum absorption at 420 nm due to surface plasmon resonance of AgNPs. X-ray diffraction studies showed that the biosynthesized AgNPs were crystalline in nature, and TEM analysis showed spherical shape of the nanoparticles with size ranging from 4.98 to 29 nm. FTIR study indicates that mainly –C = O, -OH and N-H groups in leaf extracts are involved in the reduction of Ag+ ions to Ag atoms, and proteins are responsible for stabilizing the silver nanoparticles. The synthesized AgNPs showed significant antibacterial activity against Gram positive and gram negative human bacterial pathogens. The results showed that AgNPs also synergistically enhance (2.02–57.98%) the antibacterial activity of streptomycin, a common antibiotic. With this approach, AgNPs can be used as a new generation of antimicrobial agents for successful development of drug delivery

The linear ubiquitin assembly complex (LUBAC) is essential for NLRP3 inflammasome activation

Independent of its known role in NF-κB transcription, the HOIL-1L containing LUBAC is required for assembly and activation of the NLRP3 inflammasome via linear ubiquitination of ASC.Linear ubiquitination is a newly discovered posttranslational modification that is currently restricted to a small number of known protein substrates. The linear ubiquitination assembly complex (LUBAC), consisting of HOIL-1L, HOIP, and Sharpin, has been reported to activate NF-κB–mediated transcription in response to receptor signaling by ligating linear ubiquitin chains to Nemo and Rip1. Despite recent advances, the detailed roles of LUBAC in immune cells remain elusive. We demonstrate a novel HOIL-1L function as an essential regulator of the activation of the NLRP3/ASC inflammasome in primary bone marrow–derived macrophages (BMDMs) independently of NF-κB activation. Mechanistically, HOIL-1L is required for assembly of the NLRP3/ASC inflammasome and the linear ubiquitination of ASC, which we identify as a novel LUBAC substrate. Consequently, we find that HOIL-1L−/− mice have reduced IL-1β secretion in response to in vivo NLRP3 stimulation and survive lethal challenge with LPS. Together, these data demonstrate that linear ubiquitination is required for NLRP3 inflammasome activation, defining the molecular events of NLRP3 inflammasome activation and expanding the role of LUBAC as an innate immune regulator. Furthermore, our observation is clinically relevant because patients lacking HOIL-1L expression suffer from pyogenic bacterial immunodeficiency, providing a potential new therapeutic target for enhancing inflammation in immunodeficient patients

The linear ubiquitin assembly complex (LUBAC) is essential for NLRP3 inflammasome activation

Linear ubiquitination is a newly discovered posttranslational modification that is currently restricted to a small number of known protein substrates. The linear ubiquitination assembly complex (LUBAC), consisting of HOIL-1L, HOIP, and Sharpin, has been reported to activate NF-κB–mediated transcription in response to receptor signaling by ligating linear ubiquitin chains to Nemo and Rip1. Despite recent advances, the detailed roles of LUBAC in immune cells remain elusive. We demonstrate a novel HOIL-1L function as an essential regulator of the activation of the NLRP3/ASC inflammasome in primary bone marrow–derived macrophages (BMDMs) independently of NF-κB activation. Mechanistically, HOIL-1L is required for assembly of the NLRP3/ASC inflammasome and the linear ubiquitination of ASC, which we identify as a novel LUBAC substrate. Consequently, we find that HOIL-1L(−/−) mice have reduced IL-1β secretion in response to in vivo NLRP3 stimulation and survive lethal challenge with LPS. Together, these data demonstrate that linear ubiquitination is required for NLRP3 inflammasome activation, defining the molecular events of NLRP3 inflammasome activation and expanding the role of LUBAC as an innate immune regulator. Furthermore, our observation is clinically relevant because patients lacking HOIL-1L expression suffer from pyogenic bacterial immunodeficiency, providing a potential new therapeutic target for enhancing inflammation in immunodeficient patients

Green Synthesis of Nanoparticles and Their Application in Cancer Therapy

none6simixedValeria De Matteis; Mariafrancesca Cascione; Loris Rizzello; Eva Liatsi-Douvitsa; Azzurra Apriceno; Rosaria RinaldiDE MATTEIS, Valeria; Cascione, Mariafrancesca; Rizzello, Loris; Liatsi-Douvitsa, Eva; Apriceno, Azzurra; Rinaldi, Rosari