Biology subjects

Rapole, S.

Publications and source records attributed to Rapole, S..

4 recordsLinked to original sources

bioRxiv2024

The stage-specific regulation imposed by Importin beta-1 on HIV-1 propagation and infectivity dynamics

Dynamics of intra-host molecular evolution of viruses depend on the complexities of the cellular environments through which they transit. HIV infects several cell types in an infected human host, especially during chronic stages, which impose differential regulations on HIV persistence, driving it to latency, rapid propagation, or abortive infection. We observed that HIV-1 emerging from different cell-types differ in their encapsidated protein cargo, and infectivity. We investigated the role of Importin{beta}-1, which is encapsidated in virus emerging from CD4+T lymphocytes, but not in viruses from astrocytes. We deciphered that Importin{beta}-1 is packaged via interactions with HIV-1 Gag/Capsid. The encapsidated Importin{beta}-1 assisted nuclear-entry of the viral core and enhanced the infectivity during pre-integration stages. Conversely, high levels of endogenous Importin{beta}-1, which was observed to be induced upon infection and inflammatory stimulations, such as, IFNg/LPS treatments, restricted LTR-driven viral transcription during post-integration. The regulatory impact of Importin{beta}-1 was verified using primary CD4+T lymphocytes, thereby validating a non-canonical and novel role of Importin{beta}-1 as a restriction factor for HIV-1. Using deletion mutants, we demonstrate that the N-terminal domain of Importin{beta}-1 regulated viral transcription via SP1, and NRE regions of LTR. We propose that sequestering of Importin{beta}-1 by packaging in emerging virions thereby reducing its antiviral impact, is an adaptive strategy of a pathogen, supporting the concepts of evolutionary conflicts between viruses and hosts.

molecular biology↗

bioRxiv2024

Loss of FBXO31-mediated γH2AX foci formation impairs initiation of NHEJ and HR repair pathways, and sensitizes breast cancer to therapy

In response to genotoxic stress, cell initiates complex signalling cascades to combat genomic insults through simultaneous initiation of growth arrest and DNA damage repair process. {gamma}H2AX functions as a crucial initiator in DNA double strand damage repair process. Therefore, {gamma}H2AX foci formation onto the damage sites is essential to initiate the recruitment of repair proteins involved in NHEJ (Non-homologous DNA-end joining) or HR (Homologous recombination) repair process. However, molecular events associated with {gamma}H2AX foci formation onto the DNA damage sites are poorly understood. Here, we show that FBXO31, the first ubiquitin ligase, mediated Lys-63-linked ubiquitination of {gamma}H2AX is essential for its foci formation onto the DNA damage sites to initiate recruitment of proteins involved in NHEJ and HR-mediated DNA damage repair. Therefore, tumors with FBXO31 deficiency show enhanced growth suppression following chemotherapeutic drug treatment because of synthetic lethality, indicating that FBXO31 could be used as a marker for predicting the outcome of chemotherapy treatment.

cancer biology↗

bioRxiv2024

Hypercholesterolemia-induced impairment in sorafenib functionality is overcome by avasimibe co-treatment

Avasimibe; a cholesterol-lowering drug with a proven safety in clinical trials, has recently been repositioned as an anticancer agent in various preclinical investigations. A study from our group reported that hypercholesterolemia promotes hepatocellular carcinoma (HCC) cell survival and hampers the anticancer effect of sorafenib, a kinase inhibitor. In the present study, we demonstrate that in HCC under hypercholesterolemic conditions the anticancer property of sorafenib is potentiated by avasimibe (AVA) co-treatment. Further, to elucidate the role of hypercholesterolemia on sorafenib efficacy, in vitro and in vivo models of HCC were used. In vitro, co-treatment of both drugs synergistically inhibited HCC cell viability and induced cell death under normal and hypercholesterolemic conditions. At the molecular level, downregulation of ERK signalling and induction of endoplasmic reticulum stress are likely to contribute to the combinatorial cytotoxic effect of sorafenib and avasimibe in vitro. In mice, fed on a high-cholesterol diet (HCD), the efficacy of sorafenib was restored by co-administration of AVA. Collectively, these findings suggest that impairment in the efficacy of sorafenib because of hypercholesterolemic phenotype could be restored by AVA co-treatment, which may have implications towards treatment strategy. HighlightsO_LICholesterol impedes sorafenib efficacy in Hepatocellular carcinoma cells. C_LIO_LIAvasimibe restores the functionality of sorafenib under hypercholesterolemic environment. C_LIO_LICombine treatment of sorafenib and avasimibe synergistically enhances cytotoxicity in hepatocellular carcinoma. C_LIO_LISorafenib and avasimibe treatment in the presence of LDLc.is associated with diminished ERK activation and increased ER stress. C_LI

cancer biology↗

bioRxiv2022

The role of thioredoxin proteins in Mycobacterium tuberculosis probed by proteome-wide target profiling

Mycobacterium tuberculosis encounters diverse microenvironments as it attempts to establish itself within its human host. The bacterium survives oxidative assault (ROS and RNS) when it is inside the host macrophages. Redox sensory and regulation processes therefore assume significant importance, as these are essential processes for M. tuberculosis to survive under these hostile conditions. The thioredoxin system that maintains balance between the thiol/dithiol couple plays a key role in maintaining redox homeostasis in M. tuberculosis. The most explored function of the thioredoxin system is elimination of toxic molecules such as free radicals, while very little is known about its role in other metabolic processes. In the present study, we aimed to reduce the knowledge gap about the thioredoxin system in M. tuberculosis. We attempted to capture targets of all the thioredoxins (viz., TrxB and TrxC) and a thioredoxin-like protein, NrdH in M. tuberculosis under aerobic and hypoxic conditions by performing thioredoxin trapping chromatography followed by mass spectrometry. Targets were classified using the PANTHER classification system and most enriched processes were figured out using Gene Ontology analysis. We found that TrxC captured the maximum number of targets in both the physiological conditions. Also, we suggest that the thioredoxin system might play an important role in hypoxic conditions by targeting proteins responsible to sense and maintain hypoxic conditions. Furthermore, our studies establish a link between TrxB and iron-sulfur cluster biogenesis in M. tuberculosis. Ultimately, these findings open a novel avenue to target the thioredoxin system for screening new anti-mycobacterial drug targets. ImportanceTuberculosis (TB), an infectious disease caused by bacteria M. tuberculosis, is the leading cause of death in the list of infectious diseases. Worldwide 1.7 billion people are estimated to be infected with TB, containing active and latent cases. An alarming situation is that M. tuberculosis has developed resistance against one or many of the first line drugs leading to emergence of drug resistant or multidrug resistant TB. Novel drugs targeting the drug resistant bacteria is an urgent need to cure the disease. Our study provides the framework to identify new drug targets. The significance of our study is to understand the thioredoxin system in more details by identifying their target proteins, which might facilitate development of new anti-tubercular drugs.

biochemistry↗