Biology subjects

Mehta, V.

Publications and source records attributed to Mehta, V..

14 recordsLinked to original sources

bioRxiv2026

Interstitial macrophages drive chronic lung allograft dysfunction

Despite immunosuppressive regimens targeting adaptive immunity, chronic lung allograft dysfunction (CLAD) remains the major obstacle to durable lung allograft survival. Here, we identify colony-stimulating factor 1 receptor (CSF1R)-expressing interstitial macrophages as critical orchestrators of CLAD. Using lung tissue from patients with CLAD and a mouse model of mismatched lung transplantation, we show that both donor-derived tissue-resident and recipient- monocyte-derived interstitial macrophages spatially co-localize within peribronchial immune aggregates in patients with CLAD. These interstitial macrophages express distinct cytokine programs that include those implicated in the recruitment of T and B cells. Pharmacological inhibition of CSF1R after lung transplantation in mice reduced interstitial macrophage abundance and attenuated CLAD pathology. Our findings identify donor- and recipient-derived interstitial macrophages as upstream regulators of CLAD and suggest CSF1R as a therapeutic target for its prevention and treatment.

immunology↗

bioRxiv2025

Targeting ALC1 can safely expand the therapeutic utility of PARP inhibitors across high-grade serous ovarian cancers

Poly (ADP-ribose) polymerase inhibitors (PARPi) are approved for homologous recombination-deficient (HRD) high-grade serous ovarian cancers (HGSOCs), but their long-term effectiveness is limited by the emergence of resistance and hematological toxicity. Moreover, PARPi are largely ineffective in HR-proficient HGSOCs, particularly tumors with CCNE1 amplification, which exhibit marked therapeutic resistance and currently lack effective treatment options. Loss of a chromatin remodeling enzyme, Amplified in Liver Cancer 1 (ALC1), has been shown to enhance PARPi sensitivity. However, the clinical contexts in which ALC1 targeting will be clinically meaningful remain elusive. Here we demonstrate that ALC1 loss enhances PARPi sensitivity across HRD and CCNE1-amplified serous ovarian cancer lines, xenograft and patient-derived cells. ALC1 depletion can overcome clinically relevant mechanisms of PARPi resistance while having minimal effects in BRCA-wild-type or heterozygous non-cancerous cells. Consistent with this therapeutic safety, PARPi sensitivity upon ALC1 loss can be reliably predicted by the endogenous levels of phospho-T21 RPA2, a marker for replication stress which is typically higher in ovarian cancer cells compared to their normal counterparts. Together, our studies define the clinical contexts in which the therapeutic utility of PARPi can be expanded by targeting ALC1, whose inhibitors are currently in Phase I clinical trials.

cancer biology↗

bioRxiv2025

Cholinergic modulation of dopamine release drives effortful behavior

Effort is costly: given a choice, we tend to avoid it1. But in many cases, effort adds value to the ensuing rewards2. From ants3 to humans4, individuals prefer rewards that had been harder to achieve. This counterintuitive process may promote reward-seeking even in resource-poor environments, thus enhancing evolutionary fitness5. Despite its ubiquity, the neural mechanisms supporting this behavioral effect are poorly understood. Here we show that effort amplifies the dopamine response to an otherwise identical reward, and this amplification depends on local modulation of dopamine axons by acetylcholine. High-effort rewards evoke rapid acetylcholine release from local interneurons in the nucleus accumbens. Acetylcholine then binds to nicotinic receptors on dopamine axon terminals to augment dopamine release when reward is delivered. Blocking the cholinergic modulation blunts dopamine release selectively in high-effort contexts, impairing effortful behavior while leaving low-effort reward consumption intact. These results reconcile in vitro studies, which have long demonstrated that acetylcholine can trigger dopamine release directly through dopamine axons6-11; with in vivo studies that failed to observe such modulation12-14, but did not examine high-effort contexts. Our findings uncover a mechanism that drives effortful behavior through context-dependent local interactions between acetylcholine and dopamine axons.

neuroscience↗

bioRxiv2023

Using CRISPR/Cas9 to identify genes required for mechanosensory neuron development and function

Tunicates are marine, non-vertebrate chordates that comprise the sister group to the vertebrates. Most tunicates have a biphasic lifecycle that alternates between a swimming larva and a sessile adult. Recent advances have shed light on the neural basis for the tunicate larvas ability to sense a proper substrate for settlement and initiate metamorphosis. Work in the highly tractable laboratory model tunicate Ciona robusta suggests that sensory neurons embedded in the anterior papillae of transduce mechanosensory stimuli to trigger larval tail retraction and initiate the process of metamorphosis. Here, we take advantage of the low-cost and simplicity of Ciona by using tissue-specific CRISPR/Cas9-mediated mutagenesis to screen for genes potentially involved in mechanosensation and metamorphosis, in the context of an undergraduate "capstone" research course. This small screen revealed at least one gene, Vamp1/2/3, that appears crucial for the ability of the papillae to trigger metamorphosis. We also provide step-by-step protocols and tutorials associated with this course, in the hope that it might be replicated in similar CRISPR-based laboratory courses wherever Ciona are available.

developmental biology↗

bioRxiv2023

Structural basis of activation and inhibition of the Ca2+/calmodulin-sensitive adenylyl cyclase 8

Membrane adenylyl cyclase AC8 is regulated by G proteins and calmodulin (CaM), mediating the crosstalk between the cAMP pathway and Ca2+ signalling. Despite the importance of AC8 in physiology, including cognitive functions and memory, the structural basis of its regulation by G proteins and CaM is not well defined. Here we report the 3.5 [A] resolution cryo-EM structure of the bovine AC8 bound to Ca2+/CaM and the stimulatory Gs protein. The structure reveals the architecture of the ordered AC8 domains bound to Gs and a small molecule activator forskolin. The extracellular surface of AC8 features a negatively charged pocket, a potential site for unknown interactors. Despite the well resolved forskolin density, the captured state of AC8 does not favour tight nucleotide binding. The structural proteomics approaches, limited proteolysis and crosslinking mass spectrometry, allow us to identify the contact sites between AC8 and its regulators, CaM, Gs, and G{beta}{gamma}, as well as to infer the conformational changes induced by these interactions. Our results provide a framework for understanding the role of flexible regions in the mechanism of AC regulation.

biochemistry↗

bioRxiv2023

Screening of herbal molecules for the management of Alzheimer's Disorder through molecular docking and in-vitro investigation

At present, there is not a single disease-modifying drug available for the management of Alzheimers disease (AD) pathogenesis. The exact pathology of AD is still not known, which opens up the wide scope of research for developing some novel therapeutic strategies for AD management. In the present study, 100 herbal molecules were identified through the literature survey which could be beneficial for Acetylcholinesterase (AChE), Butyrylcholinesterase (BChE), {beta}-Secretase inhibition, and neurodegeneration. AutoDock Tools-1.5.6 docking software is used to screen the herbal molecules against AChE, BChE, and {beta}-Secretase with Protein Data Bank (PDB) ID 1B41, 1P0I, and 1FKN respectively. Based on the docking parameters quercetin, rutin, vitisinol-C, dihydrotanshinone-I, and {beta}-carotene were found to be the best molecules against their respective proteins receptors. Moreover, in-vitro AChE and BChE assay demonstrated that quercetin and rutin could modulate cholinergic pathways during AD and thereby could impart beneficial effects during AD. Further, our results for in-vitro neurodegeneration studies also support the neuroprotective effect of quercetin and rutin against HgCl2-induced neurodegeneration and suggested the protective role of these molecules against neurodegeneration during AD. However, a preclinical investigation is required to support the potential effect on AD pathogenesis.

pharmacology and toxicology↗

bioRxiv2022

Evaluation of the safety, immunogenicity and efficacy of a new live-attenuated lumpy skin disease vaccine in India

Lumpy skin disease (LSD) was reported for the first time in India in 2019 and since then, it has become endemic. Since a homologous (LSD-virus based) vaccine was not available in the country, goatpox virus (GPV)-based heterologous vaccine was authorized for mass immunization against LSD in cattle. This study describes the evaluation of safety, immunogenicity and efficacy of a new live-attenuated LSD vaccine developed using an Indian field strain (LSDV/India/2019/Ranchi). The virus was attenuated by continuous passage (P=50) in Vero cells. The vaccine (50th LSDV passage in Vero cells, named as Lumpi-ProVacInd) did not induce any local or systemic reaction upon its experimental inoculation in calves (n=10). At day 30 post-vaccination (pv), the vaccinated animals were shown to develop antibody- and cell-mediated immune response and exhibited complete protection upon virulent LSDV challenge. We observed a minimum Neethling response (0.018% animals; 5 out of 26940 animals) of the vaccine in field trials among 26940 animals. There was no significant reduction in the milk yield in lactating animals (n=10108), besides there was no abortion or any other reproductive disorder in the pregnant animals (n=2889). Sero-conversion was observed in 85.18% animals in the field by day 30 pv.

microbiology↗

bioRxiv2022

GABAergic neuron-to-glioma synapses in diffuse midline gliomas

Pediatric high-grade gliomas are the leading cause of brain cancer-related death in children. High-grade gliomas include clinically and molecularly distinct subtypes that stratify by anatomical location into diffuse midline gliomas (DMG) such as diffuse intrinsic pontine glioma (DIPG) and hemispheric high-grade gliomas. Neuronal activity drives high-grade glioma progression both through paracrine signaling1,2 and direct neuron-to-glioma synapses3-5. Glutamatergic, AMPA receptor-dependent synapses between neurons and malignant glioma cells have been demonstrated in both pediatric3 and adult high-grade gliomas4, but neuron-to-glioma synapses mediated by other neurotransmitters remain largely unexplored. Using whole-cell patch clamp electrophysiology, in vivo optogenetics and patient-derived glioma xenograft models, we have now identified functional, tumor-promoting GABAergic neuron-to-glioma synapses mediated by GABAA receptors in DMGs. GABAergic input has a depolarizing effect on DMG cells due to NKCC1 expression and consequently elevated intracellular chloride concentration in DMG tumor cells. As membrane depolarization increases glioma proliferation3, we find that the activity of GABAergic interneurons promotes DMG proliferation in vivo. Increasing GABA signaling with the benzodiazepine lorazepam - a positive allosteric modulator of GABAA receptors commonly administered to children with DMG for nausea or anxiety - increases GABAA receptor conductance and increases glioma proliferation in orthotopic xenograft models of DMG. Conversely, levetiracetam, an anti-epileptic drug that attenuates GABAergic neuron-to-glioma synaptic currents, reduces glioma proliferation in patient-derived DMG xenografts and extends survival of mice bearing DMG xenografts. Concordant with gene expression patterns of GABAA receptor subunit genes across subtypes of glioma, depolarizing GABAergic currents were not found in hemispheric high-grade gliomas. Accordingly, neither lorazepam nor levetiracetam influenced the growth rate of hemispheric high-grade glioma patient-derived xenograft models. Retrospective real-world clinical data are consistent with these conclusions and should be replicated in future prospective clinical studies. Taken together, these findings uncover GABAergic synaptic communication between GABAergic interneurons and diffuse midline glioma cells, underscoring a tumor subtype-specific mechanism of brain cancer neurophysiology with important potential implications for commonly used drugs in this disease context.

neuroscience↗

bioRxiv2022

PIC50: An open source tool for interconversion of PIC50 values and IC50 for efficient data representation and analysis

Half-maximal inhibitory concentration (IC50) is used to determine the potency of a drug against a variety of enzymes/ biological targets associated with the pathogenesis of multiple disorders. The IC50 values can be depicted in multiple ways, which makes it difficult to analyze the results presented in different concentrations. Representing data in the form of PIC50 values depicting the IC50 values as the negative logarithm of IC50 in molar concentration is considered to be a better approach as it not only makes data easily understandable but also eliminates the possibility of errors in data representation and reproducibility. Considering the importance of data representation for a better understanding of data and comparing efficacy and potency of the drugs, besides, the significance of PIC50 value in the field of CADD, we found that at present there is no single open-source software available to convert the IC50 values to PIC50 values and vice versa from millimolar to picomolar range. Therefore, in the present study, we develop a tool that could help researchers to interconvert IC50 values and PIC50 values in a reliable way to eliminate the possibility of errors. We validated our tool through three case studies where the data generated by our tool was found to be 100% accurate. Moreover, we present a case where data was published in literature with errors in calculated PIC50 values and demonstrated the importance and reliability of our tool.

bioinformatics↗

bioRxiv2022

2D-QSAR and Molecular Docking based virtual screening of the herbal molecules against Alzheimers Disorder: An approach to predict CNS activity

Acetylcholinesterase (AChE) is one of the key enzyme targets that have been used clinically for the management of Alzheimers Disorder (AD). Numerous reports in the literature predict and demonstrate in-vitro, and in-silico anticholinergic activity of synthetic and herbal molecules, however, the majority of them failed to reproduce the results in preclinical or clinical settings. To address these issues, we developed a 2D-QSAR model that could not only efficiently predict the AChE inhibitory activity of herbal molecules but also predicted their potential to cross BBB to exert their beneficial effects during AD. Applying this model, virtual screening of the herbal molecules was performed and amentoflavone, asiaticoside, astaxanthin, bahouside, biapigenin, glycyrrhizin, hyperforin, hypericin, and tocopherol were predicted as the most promising herbal molecules for inhibiting AChE. Results were validated through molecular docking studies against human AChE (PDB ID: 4EY7). To determine whether or not these molecules can cross BBB to inhibit AChE within the CNS for being beneficial for the management of AD, we determined a CNS PPO score, which was found in the range of 1 to 3.76. Overall, the best results were observed for amentoflavone and our results demonstrated a PIC50 value of 7.377 nM, molecular docking score of -11.5 kcal/mol, and CNS MPO score of 3.76. In conclusion, we successfully developed a reliable and efficient 2D-QSAR model and predicted amentoflavone to be the most promising molecule that could inhibit human AChE enzyme within the CNS and could prove beneficial for the management of AD.

bioinformatics↗

bioRxiv2022

SPECC1L binds MYPT1/PP1β and can regulate its distribution between microtubules and filamentous actin

The subcellular localization, activity and substrate specificity of the serine/threonine protein phosphatase 1 catalytic subunit (PP1 cat) is mediated through its dynamic association with regulatory subunits in holoenzyme complexes. While some functional overlap is observed for the three human PP1cat isoforms, they also show distinct targeting based on relative preferences for specific regulatory subunits. A well-known example is the preferential association of MYPT1 with PP1{beta} in the myosin phosphatase complex. In smooth muscle, MYPT1/ PP1{beta} counteracts the muscle contraction induced by phosphorylation of the light chains of myosin by the myosin light chain kinase. This phosphatase complex is also found in non-muscle cells, where it is targeted to both myosin and non-myosin substrates and contributes to regulation of the balance of cytoskeletal structure and motility during cell migration and division. Although it remains unclear how MYPT1/PP1{beta} traffics between microtubule- and actin-associated substrates, our identification of the microtubule- and actin-binding protein SPECC1L in both the PP1{beta} and MYPT1 interactomes suggested that it may be the missing link. Validation of their association, together with the strong overlap that we observed for the SPECC1L and MYPT1 interactomes, suggested that they exist in a stable complex in the cell. We further showed that SPECC1L binds MYPT1 directly, and that it can impact the balance of the distribution of the MYPT1/ PP1{beta} complex between the microtubule and filamentous actin networks.

cell biology↗

bioRxiv2022

Subcellular distribution of PP1 isoforms in holoenzyme complexes

Unlike its counterpart Ser/Thr kinases, the predominant Ser/Thr protein phosphatase 1 (PP1) is a promiscuous enzyme that gains its subcellular localization and substrate specificity from a large panel of regulatory proteins with which it associates in predominantly dimeric complexes. Inhibition of specific PP1-mediated dephosphorylation events relies on targeting the regulatory rather than the catalytic subunit, which in turn relies on a comprehensive understanding of the holoenzyme complexes that underlie its distribution throughout the cell. Proteomic, bioinformatic and biochemical screens have assembled lists of putative regulatory proteins, which have been studied to varying degrees. We took a non-biased approach to link steady-state localization to complexes, using a combination of fluorescence imaging, cellular fractionation and quantitative affinity purification/mass spectrometry (AP/MS) to map interactomes for PP1[a]/{beta}/{gamma} in 3 human cell lines. Comparing the distribution of each isoform between the pool of identified regulatory subunits highlighted key signaling pathways and identified c20orf27 as a novel PP1 regulatory protein. Steady-state association of a large fraction of PP1 with the evolutionarily conserved SDS22 was demonstrated, as was redistribution at the entry to mitosis. This is consistent with recent work suggesting that SDS22 acts as a PP1 sink from which it can be recruited as needed. Moving forward, this approach can be used to assess the redistribution of PP1 during other cellular processes or in response to perturbations or disease states, facilitating identification of the relevant complexes and the design of strategies to target them therapeutically.

cell biology↗

bioRxiv2021

Structure of Mycobacterium tuberculosis Cya, an evolutionary ancestor of the mammalian membrane adenylyl cyclases

Mycobacterium tuberculosis adenylyl cyclase (AC) Rv1625c / Cya is an evolutionary ancestor of the mammalian membrane ACs and a model system for studies of their structure and function. Although the vital role of ACs in cellular signaling is well established, the function of their transmembrane (TM) regions remains unknown. Here we describe the cryo-EM structure of Cya bound to a stabilizing nanobody at 3.6 [A] resolution. The TM helices 1-5 form a structurally conserved domain that facilitates the assembly of the helical and catalytic domains. The TM region contains discrete pockets accessible from the extracellular and cytosolic side of the membrane. Neutralization of the negatively charged extracellular pocket Ex1 destabilizes the cytosolic helical domain and reduces the catalytic activity of the enzyme. The TM domain acts as a functional component of Cya, guiding the assembly of the catalytic domain and providing the means for direct regulation of catalytic activity in response to extracellular ligands. One-Sentence SummaryStructure of M. tuberculosis membrane adenylyl cyclase Cya

biochemistry↗

bioRxiv2021

Structural basis of adenylyl cyclase 9 activation

Adenylyl cyclase 9 (AC9) is a membrane-bound enzyme that converts ATP into cAMP. The enzyme is weakly activated by forskolin, fully activated by the G protein Gs subunit and is autoinhibited by the AC9 C-terminus. Although our recent structural studies of the AC9-Gs complex provided the framework for understanding AC9 autoinhibition, the conformational changes that AC9 undergoes in response to activator binding remains poorly understood. Here, we present the cryo-EM structures of AC9 in several distinct states: (i) AC9 bound to a nucleotide inhibitor MANT-GTP, (ii) bound to an artificial activator (DARPin C4) and MANT-GTP, (iii) bound to DARPin C4 and a nucleotide analogue ATPS, (iv) bound to Gs and MANT-GTP. The artificial activator DARPin C4 partially activates AC9 by binding at a site that overlaps with the Gs binding site. Together with the previously observed occluded and forskolin-bound conformations, structural comparisons of AC9 in the four new conformations show that secondary structure rearrangements in the region surrounding the forskolin binding site are essential for AC9 activation. One Sentence SummaryCryo-EM reveals activator-induced conformational changes in adenylyl cyclase AC9

biochemistry↗