Biology subjects

Harshan, K.

Publications and source records attributed to Harshan, K..

4 recordsLinked to original sources

bioRxiv2025

STING is a key driver of Japanese encephalitis virus induced inflammatory response

Interferon (IFN) and inflammation are the key early defence mechanisms that combat pathogen infection. The cytosolic DNA sensor cGAS activates immune signaling via the stimulator of interferon genes (STING) protein. Emerging evidence suggests crosstalk between innate immune DNA and RNA sensing, implicating a role of STING protein in RNA virus infection. This study characterizes STING in the context of Japanese encephalitis virus (JEV), an RNA virus of the flaviviridae family. We observe that activation of type I IFN through MAVS is essential for cGAS and STING activation. Knockdown, null mutant and inhibitor studies confirmed that STING restricts JEV replication independently of IFN{beta} signaling and autophagy. Transcriptomic analysis of STINGgt/gt bone-marrow derived macrophages (BMDMs) showed enhanced IFN response, but reduced activation of inflammatory cytokines and chemokines. Phosphorylated STING was recruited on the virus replication complex (RC), marked by the non-structural protein NS1, subsequently triggering the assembly of the NLRP3 inflammasome on the RC. STING proton channel activity was essential for NLRP3 inflammasome activation, IL-1{beta} production, and activation of pyroptotic cell death markers. Stinggt/gt mice, showed higher viremia, earlier disease onset, reduced survival, and decreased brain inflammation. These findings establish STING as a key regulator of JEV-induced inflammation and antiviral defence.

microbiology↗

bioRxiv2022

Anti-COVID-19 Activity of FDA Approved Drugs through RNA G-quadruplex Binding

The COVID-19 pandemic caused by SARS-CoV-2 has caused millions of infections and deaths worldwide. Limited treatment options and the threat from emerging variants underline the need for novel and widely accessible therapeutics. G-quadruplexes (G4s) are nucleic acid secondary structures known to affect many cellular processes including viral replication and transcription. We identified heretofore not reported G4s with remarkably low mutation frequency across >5 million SARS-CoV-2 genomes. The G4 structure was targeted using FDA-approved drugs that can bind G4s - Chlorpromazine (CPZ) and Prochlorperazine (PCZ). We found significant inhibition in lung pathology and lung viral load of SARS-CoV-2 challenged hamsters when treated with CPZ, PCZ that was comparable to the widely used antiviral drug Remdesivir. In support, in vitro G4 binding, inhibition of reverse transcription from RNA isolated from COVID-infected humans, and attenuated viral replication and infectivity in Vero cell cultures were clear in case of both CPZ/PCZ. Apart from the wide accessibility of CPZ/PCZ, targeting relatively invariant nucleic acid structures poses an attractive strategy against fast mutating viruses like SARS-CoV-2.

molecular biology↗

bioRxiv2020

Improved and Simplified Diagnosis of Covid-19 using TE Extraction from Dry Swabs

Rigorous testing is the way forward to fight the Covid-19 pandemic. Here we show that the currently used and most reliable RT-PCR based SARS-CoV-2 procedure can be further simplified to make it faster, safer and economical by bypassing the RNA isolation step. The modified method is not only fast and convenient but also at par with the traditional method in terms of accuracy, and therefore, can be used for mass screening. Our method takes about half the time and is cheaper by about 40% compared to current most widely used method. We also provide a variant of the new method that increases the efficiency of detection by about 20% compared to the currently used method. Taken together, we demonstrate a more effective and reliable method of SARS-CoV-2 detection.

molecular biology↗

bioRxiv2018

mTORC1 Restricts Hepatitis C Virus Replication Through ULK1-mediated Suppression of miR-122 and Facilitates Post-replication Events

Mechanistic target of rapamycin (mTOR) is an important kinase that assimilates several upstream signals including viral infection and facilitates appropriate response by the cell through two unique complexes mTORC1 and mTORC2. Here, we demonstrate that mTORC1 is activated early during HCV infection as antiviral response. Pharmacological inhibition of mTORC1 promoted HCV replication as suggested by elevated levels of HCV (+) and (-) RNA strands. This was accompanied by significant drop in extracellular HCV RNA levels indicating defective post-replication stages. The increase in viral RNA levels failed to augment intracellular infectious virion levels, suggesting that mTORC1 inhibition is detrimental to post-replication steps. Lower infectivity of the supernatant confirmed this observation. Depletion of Raptor and ULK1 accurately reproduced these results suggesting that mTORC1 imparted these effects on HCV through mTORC1-ULK1 arm. Interestingly, ULK1 depletion resulted in increased levels of miR-122, a critical host factor for HCV replication, thus revealing a new mechanism of regulation by ULK1. The binary effect of mTORC1 on HCV replication and egress suggests that mTORC1-ULK1 could be critical in replication: egress balance. Interestingly we discover that ULK1 depletion did not interfere with autophagy in Huh7.5 cells and hence the effects on HCV replication and post-replication events are not resultant of involvement of autophagy. Our studies demonstrate an overall ULK1 mediated anti-HCV function of mTORC1 and identifies an ULK1-independent autophagy that allows HCV replication in spite of mTORC1 activation.

microbiology↗