Biology subjects

Gulyani, A.

Publications and source records attributed to Gulyani, A..

8 recordsLinked to original sources

bioRxiv2025

Time-dependent processing of dengue virus polyprotein yields multiple capsid forms that disrupt cellular homeostasis

Dengue virus infections spread to new geographical regions every year, cause significant morbidity and mortality, yet the progress in drug/vaccine development is limited due to an incomplete understanding of its life cycle. While a few of the proteins coded by this virus exist in multiple forms, the sequential events of polyprotein processing to yield them and the consequential effects on host cells are unclear. In this study, the virus infected cell culture data suggest that the polyprotein undergoes a time-dependent processing to yield multiple capsid forms, ie, capsid, capsid-anchor, capsid-anchor-pr, capsid-anchor-prM. Among them, the c-anc and c-anc-pr were found to localize to the mitochondria upon transfection into the HEK cells. The transmission electron microscopy studies suggest that c-anc induces mitochondrial fragmentation. Further studies showed that c-anc affects the mitochondrial fusion-related proteins and the genes involved in their functions. The pulldown experiments indicate that c-anc also interacts with 1-syntrophin (SNTA1), a cytoplasmic protein that plays a role in redox potential, oxidative stress and mitochondrial biogenesis. Importantly, the mitostress analyses suggest that c-anc triggers impaired mitochondrial dysfunctions like potential, respiration and ATP generation. In this study, we also identify ursonic acid (UNA) as a c-anc binding compound that restores mitochondrial functions and suppresses virus multiplication in vitro, ex vivo and in mice. The revealed disrupted mitochondrial homeostasis appears to be common to DENV, ZIKV, JEV, YFV, HCV, ASFV and SARS-CoV-2; hence, UNA or its related compounds could be considered as inhibitors for the above virus infections.

microbiology↗

bioRxiv2025

Genomic diversity analysis enables development of pan-Dengue Toehold RNA sensors

The Dengue virus (DENV) like many other RNA viruses exhibits high genome sequence diversity. This poses a challenge to nucleic acid-based diagnostics, rendering them inefficient at detecting the diverse DENV strains circulating in a population. In this study, we address this challenge by developing a Toehold sensor assay that despite significant genomic diversity is able to detect [~]99.4% of all strains of DENV. To this end, our workflow first identifies relatively conserved short stretches (36-nt) within all DENV genomes, which could potentially serve as triggers that activate Toehold RNA sensors. We then add a crucial step of mismatch-tolerance that allows related triggers with high sequence diversity and multiple mismatches in the sensor-binding region to be efficiently sensed by the same sensor. The sensitivity of the Toehold sensor assay is often increased by inclusion of an isothermal RNA amplification step. We show by employing multiple primer sets that diverse trigger RNAs from all four serotypes of the dengue virus can be successfully amplified and subsequently detected by the same sensor. Together, this approach has resulted in a pan-dengue Toehold sensor assay, which presents a powerful nucleic acid detection platform to detect viruses with high sequence diversity.

molecular biology↗

bioRxiv2025

Temporal integration and active sensing of light in planarians

Animal light sensing and processing are intimately connected to the design of the sensory apparatus, with eye-design a subject of longstanding interest. Understanding animal response to stimuli can elucidate the nature of neural-processing encoded within the photosensory system, tuned to the specific eye-design. Planarians show exquisite photosensitivity and remarkably diverse light-induced behaviors. Further, they are bilaterally-symmetric and possess prototypic cup-shaped eyes, considered an important landmark in eye evolution. Here, using quantitative analysis of behaviour, we address planarian photo-response to distinct presentation of light gradients. Notably, we find that as the nature and presentation of gradients are altered, planarians switch their navigation strategies. When subjected to side-illumination, planarians display negative-phototaxis with a predominantly angular trajectory which presumably allows the animal to maintain the intensity difference between their two eyes for orientation during taxis. However, when subjected to top illumination where light intensity difference between the two eyes would be minimal, animals are still negatively phototactic but the dominant trajectories tend to be directly away from light. Apart from spatial light-intensity sensing, planarians also appear capable of temporal light sensing; confirmed by their response to a spatially-uniform light source with intensity modified over time. Crucially data show that planarians may be using spatial and temporal light sensing to differing degrees depending on the stimuli. Further, when subjected to light illumination from below, planarians fully switch orientation and go belly-up, indicating an active sampling of light distinct from photo-aversive behaviour. Overall, our results show planarian light-sensing to be multilayered, dependent on distinct, highly plastic sensory strategies and beyond basic photo-aversive behaviour.

animal behavior and cognition↗

bioRxiv2022

Mindin differentially regulates fibroblast subpopulations via distinct members of the Src family kinases during fibrogenesis.

Fibrosis is the result of excessive deposition of extracellular matrix (ECM) proteins leading to tissue hardening and loss of organ function. A central player driving fibrosis is the activated fibroblast, which exhibits enhanced migration, proliferation, contraction, and ECM production. However, this raises an interesting puzzle of whether the same fibroblast performs all of the processes that fall under the umbrella term of "activation". Given the heterogeneity of fibroblasts in connective tissues, there are subpopulations of fibroblasts that perform specific functions that are under different regulatory controls. Using a transgenic mouse model of skin fibrosis, we find that the secretion of Mindin from Snail transgenic keratinocytes differentially alters the characteristic of distinct fibroblast subpopulations. Mindin induces migration and inflammatory gene expression of the Sca1+ subpopulation of dermal fibroblasts in a Fyn kinase-dependent manner. On the other hand, Mindin increases the contractile behaviour and collagen production in the papillary CD26+ dermal fibroblasts via c-Src. Moreover, in the context of the fibrotic microenvironment of the tumour stroma, we found that differential responses of resident fibroblasts subpopulations to Mindin extend to the generation of functionally heterogeneous cancer-associated fibroblasts (CAFs). Overall, this work highlights the importance of Mindin in mediating the cellular and signalling heterogeneity of dermal fibroblasts in skin fibrosis and cancer.

cell biology↗

bioRxiv2021

Snail maintains the stem/progenitor state of skin epithelial cells and carcinomas through the autocrine effect of the matricellular protein Mindin

Intratumoral heterogeneity poses a major challenge in designing effective anti-cancer strategies. Accumulating evidence suggests that this heterogeneity arises from cancer stem cells (CSCs) that also drives tumor aggressiveness and drug resistance. The stemness of CSCs are preserved by an ill-defined combination of intrinsic and external factors and is particularly intriguing since they exist within a sea of similar cells at various degrees of differentiation. In models of cutaneous squamous cell carcinoma (cSCC), we discovered a non-EMT function for the transcription factor Snail in maintaining stemness of keratinocytes. This is accomplished by the secretion of the matricellular protein Mindin from Snail expressing cells, which creates a protective niche that impedes differentiation. In an autocrine fashion, extracellular Mindin activates a Src -STAT3 pathway to reinforce the stem/progenitor phenotype and disruption of this signalling module in human cSCC attenuates tumorigenesis. The expression of Mindin in multiple carcinomas, and its critical role in cancer progression suggests that it would be a promising target for therapeutic intervention.

cell biology↗

bioRxiv2020

Molecular and functional characterization of buffalo nasal epithelial odorant binding proteins and their structural insights by in-silico and biochemical approach

The olfactory system is capable of detecting and distinguishing thousands of environmental odorants that play a key role in reproduction, social behaviours including pheromones influenced classical events. Membrane secretary odorant binding proteins (OBPs) are soluble lipocalins, localized in the nasal membrane of mammals. They bind and carry odorants within the nasal epithelium to putative olfactory transmembrane receptors (ORs). While the existence of OBPs and their significant functions are very well known in insects and laboratory mammals, there is little information about the species-specific OBPs in buffaloes. In fact, the OBP of nasal epithelium has not yet been exploited to develop a suitable technique to detect estrus which is being reported as a difficult task in buffalo. In the present study, using molecular biology and protein engineering approaches, we have cloned six novel OBP isoforms from buffalo nasal epithelium (bnOBPs). Furthermore, 3D model was developed and molecular-docking, dynamics experiments were performed by In-silico approach. In particular, we found four residues (Phe104, Phe134, Phe69 and Asn118) from OBP1a, which had strong binding affinities towards two sex pheromones, specifically oleic acid and p-cresol. We expressed this protein in Escherichia coli to examine its involvement in the sex pheromone perception from female buffalo urine and validated through fluorescence quenching studies. Interestingly, fluorescence binding experiments also showed similar strong binding affinities of OBP1a to oleic acid and p-cresol. By using structural data, the binding specificity is also verified by site-directed mutagenesis of the four residues followed by in-vitro binding assays. Our results enable to better understand the functions of different nasal epithelium OBPs in buffaloes. They also lead to improved understanding of the interaction between olfactory proteins and odorants to develop highly selective biosensing devices for non-invasive detection of estrus in buffaloes.

bioinformatics↗

bioRxiv2019

A Fyn - specific biosensor reveals localized, pulsatile kinase activity and spatially regulated signaling crosstalk

Cell behavior is controlled through spatio-temporally localized protein activity. Despite unique and often contradictory roles played by Src-family-kinases (SFKs) in regulating cell physiology, activity patterns of individual SFKs have remained elusive. Here, we report a biosensor for specifically visualizing active conformation of SFK-Fyn in live cells. We deployed combinatorial library screening to isolate a binding-protein (F29) targeting activated Fyn. Nuclear-magnetic-resonance (NMR) analysis provides the structural basis of F29 specificity for Fyn over homologous SFKs. Using F29, we engineered a sensitive, minimally-perturbing fluorescence-resonance-energy-transfer (FRET) biosensor (FynSensor) that reveals cellular Fyn activity to be spatially localized, pulsatile and sensitive to adhesion/integrin signaling. Strikingly, growth factor stimulation further enhanced Fyn activity in pre-activated intracellular zones. However, inhibition of focal-adhesion-kinase activity not only attenuates Fyn activity, but abolishes growth-factor modulation. FynSensor imaging uncovers spatially-organized, sensitized signaling clusters, direct crosstalk between integrin and growth-factor-signaling, and clarifies how compartmentalized Src-kinase activity may drive cell fate.

cell biology↗

bioRxiv2018

Euchromatic histone methyltransferases regulate peripheral heterochromatin tethering via histone and non-histone protein methylations

Euchromatic histone methyltransferases (EHMTs), members of the KMT1 family, methylate histone and non-histone proteins. Here we uncover a novel role for EHMTs in regulating heterochromatin anchorage to the nuclear periphery (NP) via non-histone (LaminB1) methylations. We show that EHMTs methylates and stabilizes LaminB1 (LMNB1), which associates with the H3K9me2-marked peripheral heterochromatin. Loss of LMNB1 methylation or EHMTs abrogates the heterochromatin anchorage from the NP. We further demonstrate that the loss of EHMTs induces many hallmarks of aging including global reduction of H3K27methyl marks along with altered nuclear-morphology. Consistent with this, we observed a gradual depletion of EHMTs, which correlates with loss of methylated LMNB1 and peripheral heterochromatin in aging human fibroblasts. Restoration of EHMT expression reverts peripheral heterochromatin defect in aged cells. Collectively our work elucidates a new mechanism by which EHMTs regulate heterochromatin domain organization and reveals their impact on fundamental changes associated with the intrinsic aging process.

genetics↗