The molecular basis of tight nuclear tethering and inactivation of cGAS.

Nucleic acids derived from pathogens induce potent innate immune responses1-6. Cyclic GMP-AMP synthase (cGAS) is a double-stranded DNA sensor that catalyses the synthesis of the cyclic dinucleotide cyclic GMP-AMP, which mediates the induction of type I interferons through the STING-TBK1-IRF3 signalling axis7-11. cGAS was previously thought to not react with self DNA owing to its cytosolic localization2,12,13; however, recent studies have shown that cGAS is localized mostly in the nucleus and has low activity as a result of tight nuclear tethering14-18. Here we show that cGAS binds to nucleosomes with nanomolar affinity and that nucleosome binding potently inhibits its catalytic activity. To elucidate the molecular basis of cGAS inactivation by nuclear tethering, we determined the structure of mouse cGAS bound to human nucleosome by cryo-electron microscopy. The structure shows that cGAS binds to a negatively charged acidic patch formed by histones H2A and H2B via its second DNA-binding site19. High-affinity nucleosome binding blocks double-stranded DNA binding and maintains cGAS in an inactive conformation. Mutations of cGAS that disrupt nucleosome binding alter cGAS-mediated signalling in cells.

Structural dynamics of receptor recognition and pH-induced dissociation of full-length Clostridioides difficile Toxin B.

Clostridioides difficile secretes Toxin B (TcdB) as one of its major virulence factors, which binds to intestinal epithelial and subepithelial receptors, including frizzled proteins and chondroitin sulfate proteoglycan 4 (CSPG4). Here, we present cryo-EM structures of full-length TcdB in complex with the CSPG4 domain 1 fragment (D1401-560) at cytosolic pH and the cysteine-rich domain of frizzled-2 (CRD2) at both cytosolic and acidic pHs. CSPG4 specifically binds to the autoprocessing and delivery domains of TcdB via networks of salt bridges, hydrophobic and aromatic/proline interactions, which are disrupted upon acidification eventually leading to CSPG4 drastically dissociating from TcdB. In contrast, FZD2 moderately dissociates from TcdB under acidic pH, most likely due to its partial unfolding. These results reveal structural dynamics of TcdB during its preentry step upon endosomal acidification, which provide a basis for developing therapeutics against C. difficile infections.

Small-Molecule Inhibitor Prevents Insulin Fibrillogenesis and Preserves Activity.

Amyloidosis is a well-known but poorly understood phenomenon caused by the aggregation of proteins, often leading to pathological conditions. For example, the aggregation of insulin poses significant challenges during the preparation of pharmaceutical insulin formulations commonly used to treat diabetic patients. Therefore, it is essential to develop inhibitors of insulin aggregation for potential biomedical applications and for important mechanistic insights into amyloidogenic pathways. Here, we have identified a small molecule M1, which causes a dose-dependent reduction in insulin fibril formation. Biophysical analyses and docking results suggest that M1 likely binds to partially unfolded insulin intermediates. Further, M1-treated insulin had lower cytotoxicity and remained functionally active in regulating cell proliferation in cultured Drosophila wing epithelium. Thus, M1 is of great interest as a novel agent for inhibiting insulin aggregation during biopharmaceutical manufacturing.

Bioremediation of steel plant wastewater and enhanced electricity generation in microbial desalination cell.

Microbial desalination cell (MDC) is a propitious technology towards water desalination by utilizing wastewater as an energy source. In this study, a multi-chambered MDC was used to bioremediate steel plant wastewater using the same wastewater as a fuel for anodic bacteria. A pure culture of Pseudomonas putida MTCC 1194 was isolated and inoculated to remove toxic phenol. Three different inoculum conditions, namely P. putida (INC-A), a mixture of P. putida and activated sludge (INC-B), and activated sludge alone (INC-C) were employed in an anodic chamber to mainly compare the electricity generation and phenol degradation in MDCs. The study revealed the maximum phenol removal of 82 ± 2.4%, total dissolved solids (TDS) removal of 68 ± 1.5%, and power generation of 10.2 mW/m2 using INC-B. The synergistic interactions between microorganisms, can enhance the toxic phenol degradation and also electricity generation in MDC for onsite wastewater application.

Phytoremediation of industrial mines wastewater using water hyacinth.

The wastewater at Sukinda chromite mines (SCM) area of Orissa (India) showed high levels of toxic hexavalent chromium (Cr VI). Wastewater from chromium-contaminated mines exhibit potential threats for biotic community in the vicinity. The aim of the present investigation is to develop a suitable phytoremediation technology for the effective removal of toxic hexavalent chromium from mines wastewater. A water hyacinth species Eichhornia crassipes was chosen to remediate the problem of Cr (VI) pollution from wastewater. It has been observed that this plant was able to remove 99.5% Cr (VI) of the processed water of SCM in 15 days. This aquatic plant not only removed hexavalent Cr, but is also capable of reducing total dissolved solids (TDS), biological oxygen demand (BOD), chemical oxygen demand (COD), and other elements of water also. Large-scale experiment was also performed using 100 L of water from SCM and the same removal efficiency was achieved.

The molecular mechanism of dsDNA sensing through the cGAS-STING pathway.

Double stranded DNA (dsDNA) in the cytoplasm triggers the cGAS-STING innate immune pathway to defend against pathogenic infections, tissue damage and malignant cells. Extensive structural and functional studies over the last couple of years have enabled the molecular understanding of dsDNA induced activation of the cGAS-STING signaling pathway. This review highlights recent advances in the structural characterization of key molecules in the cGAS-STING signaling axis by focusing on the mechanism of cGAS activation by dsDNA, the regulation of cGAS activity, the mechanism of STING activation by cGAMP, the molecular basis of TBK1 recruitment and activation by STING, the structural basis of IRF3 recruitment by STING, and the mechanism of IRF3 activation upon phosphorylation by TBK1. These comprehensive structural studies provide a detailed picture of the mechanism of the cGAS-STING signaling pathway, establishing a molecular framework for the development of novel therapeutic strategies targeting this pathway.

COVID-19 Contraction Among Dental Healthcare Workers in the Department of Conservative Dentistry and Endodontics - A Retrospective Analysis During the Pandemic.

Introduction: The COVID-19 pandemic has led to major challenges for the healthcare sector across the globe including dental healthcare workers (DHCWs) due to the increased risk of transmission of virus during aerosol-generating procedures. We conducted the present retrospective analysis determining the risk of contraction of COVID-19 infection among DHCWs since the outbreak of the pandemic for a year (March 2020 through March 2021) in Mumbai. Methods: In total, 18,058 patients visited the Nair Hospital Dental College for dental treatment related to the Department of Conservative Dentistry and Endodontics during the assessed year. All the patients were subjected to intensive triage, which included recording their body temperature, oxygen saturation level, travel, and COVID-19 exposure history. Results: A total of 26 DHCWs were responsible for attending and treating the patients with all the standard infection control measures. Seventy-four (0.40%) patients out of 18058 were referred for a nasal rapid antigen test (RAT) on giving a positive affirmation about COVID-19 like symptoms when screened at the triage. Of those 74 patients referred, 20 reported a positive nasal rapid antigen test and the infection was confirmed by Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). Among 26, 9 (34,7%) DCHWs were found to have contracted the infection during the assessed year. Conclusion: The analysis found that the risk of COVID-19 infection contraction amongst the DHCWs is considerably less. This could be attributed to the intensive triage and the preventive measures taken while rendering treatment.

The Multifaceted Influence of COVID-19 on Indian Dentists: A Cross-Sectional Survey.

Introduction: COVID-19 has had a new challenge on dental workers, radically altering clinical and personal management. The cross-sectional survey sought to examine and comprehend the influence of COVID-19 on Indian dentistry practitioners. Methods: A 38-item questionnaire-based survey was communicated to Indian dental practitioners through a web-based form (Google form). The questionnaire was categorized into four sections: (i) Personal protective equipment (PPE), (ii) dental treatments, (iii) auxiliary management, and (iv) personal impact. The findings were examined and studied in order to comprehend the repercussions of COVID-19. The questionnaire was completed by 513 of the 1129 dentists to whom it was delivered. Results: For the current questionnaire, a response rate that we received was 45.44%. When compared to the pre-pandemic era, the use of PPE has increased dramatically (95.7%). The use of PPE alleviated dental practitioners' and patients' doubts about viral transmission. The epidemic prompted the Ministry of Health and Family Welfare (MoHFW) to issue specific recommendations for dental treatments, which were followed by 92.5% of dentists. The majority of dentists reported a considerable impact on both financial and mental health concerns. Teleconsulting and distant learning gained greater prominence. The COVID-19 epidemic affected the lives of dental professionals both within and outside of the dental setting, as well as the auxiliary. Conclusion: COVID-19 has left a trail of devastation in its aftermath. Dentists were affected both emotionally and professionally. Dentists rapidly and uniformly followed the revised recommendations.

Endodontic Emergencies in Mumbai City during COVID-19 Lockdown and Different Phases of Unlock.

The present descriptive research focused on determining the traits of patients who required endodontic treatment during the COVID-19 lockdown and various stages of unlocking in Mumbai metropolitan region. The descriptive analysis was carried out by examining the patients who were registered at Nair Hospital Dental College, Mumbai during four phases of lockdown (25 March to 31 May 2020) and eight phases of unlock (1 June 2020 to 31 January 2021). The evaluation was performed by evaluating the number of days and the overall number of patients reported for endodontic treatment for the first and subsequent visits. Each patient underwent intensive triage, which included taking their body temperature, oxygen saturation level, and travel history. The sex, age, and endodontic diagnosis of the offending tooth were also reported. The pain parameters were analyzed using a verbal numerical rating score (VNRS). During the lockdown phases, 297 patients seeking endodontic treatment visited the hospital over a total of 26 working days, and during the unlock phases, 16,195 patients visited the hospital over 189 working days. The average age of the patients that visited were 31-40 years of age (57.23%). The mean VNRS score was 5.85 ± 1.62. For both the lockdown and unlock periods, a significantly higher percentage of males visited dental school (p < 0.001). When compared to other stages, the number of patients attending during lockdown phase 4 (55.56%) and unlock phase 8 (32.35%) was the highest. The majority of endodontic emergency diagnoses were reversible pulpitis (36.5%) and symptomatic irreversible pulpitis (33.14%), all of which had higher mean VNRS (p < 0.05). Of the 49 patients that reported with COVID-19 symptoms, 11 tested positive. During the lockdown and unlock periods, 12 of the 41 treating workers tested positive. Personal protective equipment and patient screening are critical in shielding clinicians during the COVID-19 pandemic.