Biology subjects

Trivedi, N.

Publications and source records attributed to Trivedi, N..

6 recordsLinked to original sources

bioRxiv2026

Cell-based epitope screen identifies a novel B chain-derived Hybrid Insulin Peptide recognized by human and mouse autoreactive CD4 T cells

Type 1 diabetes (T1D) is mediated by autoreactive CD4 T cells that recognize pancreatic {beta}-cell antigens MHC class II molecules. The B-chain of insulin is thought to be a primary autoantigen although native peptide sequences from the B-chain bind weakly to disease-associated MHC risk alleles. Hybrid Insulin Peptides (HIPs), consist of proinsulin fragments fused with peptides from other {beta}-cell proteins, and may endow B-chain peptides with C-terminal acid residues that allow strong binding to MHC risk alleles and subsequent stimulation of autoreactive T cells. Here we applied a high-throughput cell-based screening platform with Signaling and Antigen-presenting Bifunctional Receptors (SABRs) to interrogate a theoretical library of insulin B-chain HIPs against clonally expanded CD4 T cell receptors from NOD mouse islets. We identified a previously undescribed HIP containing a fragment of insulin B-chain combined with a calreticulin-derived peptide. I-Ag7 tetramers loaded with the InsB/Calr HIP bind to T cell clones as well as islet-infiltrating CD4 T cells and CD4 T cells from a recent-onset HLA-DQ2 T1D donor reacted exclusively to the InsB/Calr HIP. Collectively, these results demonstrate that insulin B-chain-derived peptides can undergo post-translational modification through HIP formation to generate neoepitopes with increased antigenicity, and underscore the utility of cell-based screening for identifying disease-relevant neoepitopes in T1D.

immunology↗

bioRxiv2022

De novo identification of CD4+ T cell epitopes

CD4+ T cells recognize peptide antigens presented on class II Major Histocompatibility Complex (MHC-II) molecules to carry out their function. The remarkable diversity of T cell receptor (TCR) sequences and lack of antigen discovery approaches for MHC-II make profiling the specificities of CD4+ T cells challenging. We have expanded our platform of Signaling and Antigen-presenting Bifunctional Receptors to encode MHC-II molecules presenting covalently linked peptides (SABR-IIs) for CD4+ cell antigen discovery. SABR-IIs can present epitopes to CD4+ T cells and induce signaling upon their recognition, allowing a readable output. Here, we demonstrate that SABR-IIs libraries presenting endogenous and post-translationally modified epitopes can be used for antigen discovery. Using SABR-II libraries in conjunction with single cell RNA sequencing, we de-convoluted multiple highly expanded TCRs from pancreatic islets of Non-Obese Diabetic (NOD) mice. We compounded antigen discovery by incorporating computational TCR similarity prediction metrics followed by experimental validation. Finally, we showed SABR-IIs presenting epitopes in class II HLA alleles can be used for antigen discovery for human CD4+ T cells. Taken together, we have developed a rapid, flexible, scalable, and versatile approach for the de novo identification of CD4+ T cell ligands from single cell RNA sequencing data using experimental and computational approaches.

immunology↗

bioRxiv2022

Antagonistic action of Siah2 and Pard3/JamC to promote germinal zone exit of differentiated cerebellar granule neurons by modulating Ntn1 signaling via Dcc

Germinal zone (GZ) exit is at the top of a cascade of events promoting the maturation of neurons and their assembly into neuronal circuits. Developing neurons and their progenitors must interpret varied niche signals like morphogens, guidance molecules, extracellular matrix, or adhesive cues to navigate GZ occupancy. How newborn neurons integrate multiple cell-extrinsic niche cues with their cell-intrinsic machinery in exiting a GZ is unknown. We establish cooperation between cell polarity-regulated adhesion and Netrin-1 signaling comprises a coincidence detection circuit repelling maturing neurons from their GZ. In this circuit, the Partitioning defective 3 (Pard3) polarity protein and Junctional adhesion molecule-C (JAM-C) adhesion protein promote, while the Seven in absentia 2 (Siah2) ubiquitin ligase inhibits, Deleted in colorectal cancer (DCC) receptor surface recruitment to gate differentiation linked repulsion to GZ Netrin-1. These results demonstrate cell polarity as a central integrator of adhesive- and guidance cues cooperating to spur GZ exit. Highlights-Netrin1 expressed in the cerebellar GZ ranges from an attractive to repulsive cue depending on differentiation status or extracellular matrix context. -Modulation of DCC expression levels impacts the nature of the Netrin1 response and GZ occupancy status. -Siah2, Pard3, and JamC function to modulate responsiveness to purified Netrin1 and cooperate with Dcc to regulate GZ exit. -Pard3 and JamC promote both basal and Netrin1 stimulated DCC surface recruitment to control GZ exit and Netrin1 repulsion

neuroscience↗

bioRxiv2021

Bioactivity, chemical profiling, and 16S rRNA-based phylogeny of haloalkaliphilic Nocardiopsis sp. GhM-HA-6 isolated from the Gulf of Khambhat

ObjectivesActinomycetes are well known sources of antibiotics, however; recently the focus of antimicrobial research has been turning towards actinomycetes of extreme environments. Therefore, present work would highlight the isolation, identification and characterization of antimicrobial metabolites produced by marine haloalkaliphilic actinomycetes. MethodsSaline soil sample was collected from Ghogha coast (Gulf of Khambhat), Bhavnagar, Western India. Isolation was carried out using selective media while identification was done based on morphological, cultural and molecular characterization. The antimicrobial potential was checked by spot inoculation method. Optimization was carried out by the one variable at a time (OVAT) method. The antimicrobial compounds were extracted using ethyl acetate and characterized by GC-MS. ResultsThe haloalkaliphilic actinomycetes Nocardiopsis sp. GhM-HA-6 was isolated from saline soil of Ghogha coast using starch agar with 10% w/v NaCl and pH 9 and was identified as Nocardiopsis sp. based on morphology, cultural characteristics and 16S rRNA phylogenetic analysis (NCBI Genbank Accession number: KF384492). The organism showed antimicrobial activity against five Gram positive and three Gram negative bacteria while the isolate didnt show any antifungal activity. Results of optimization showed that the highest production of antimicrobial compounds was obtained using starch broth with 0.5% w/v starch, 1% w/v yeast extract, 10% w/v NaCl and pH 9. GC-MS analysis of ethyl acetate extract of the isolate showed presence of total 18 compounds including various antimicrobial compounds like 2, 4-bis (1, 1-dimethylethyl)-Phenol, various types of alkanes and their derivatives. ConclusionHaloalkaliphilic actinomycete Nocardiopsis sp. GhM-HA-6, from a rarely explored marine habitat, can be a source of antimicrobial compounds with the novel biotechnological applications.

microbiology↗

bioRxiv2021

Chemical Profiling of Antimicrobial Metabolites from Halophilic Actinomycete Nocardiopsis_sp. Al-H10-1 (KF384482) Isolated from Alang, Gulf of Khambhat, India

The overuse of antibiotics has resulted in the development of drug resistant, a major problem in disease curing processes i.e. development of drug resistance. The World Health Organization (WHO) released its first list of the most concerning pathogens for human health in 2017 which suggested that there are total 12 bacterial families which have developed multiple drug resistance and for which novel antibiotics are required immediately (WHO 2017). There is a requirement to explore some novel compounds to overcome this issue. Thus our study aimed at exploration of marine actinomycetes as a valuable resource for novel products with antimicrobial properties. The halophilic actinomycete Nocardiopsis_sp. Al-H10-1 (KF384482) was isolated from saline water (20 m away from shore) of Alang coast (Gulf of Khambhat), Bhavnagar, Gujarat, India. The isolate Al-H10-1 was identified as Nocardiopsis sp. through rigorous morphological and cultural characteristics; the species was confirmed through 16s rRNA phylogenetic analysis. The antimicrobial potential of Nocardiopsis sp. Al-H10-1 was assessed against a range of Gram-positive and Gram-negative bacteria as well as three fungi, there it demonstrated antimicrobial activity against four Gram negative bacteria and one Gram positive bacteria. Further active antimicrobial compounds present in ethyl acetate extract was identified using Gas Chromatography-Mass Spectroscopy (GC-MS). GC-MS analysis showed the presence of 17 compounds which included antimicrobial compounds like 2, 4-bis (1, 1-dimethylethyl)-Phenol, Dibutyl phthalate as well as various types of alkanes and their derivatives.

microbiology↗

bioRxiv2019

Siah2 integrates mitogenic and extracellular matrix signalslinking neuronal progenitor ciliogenesis with germinal zoneoccupancy.

Evidence is lacking as to how developing neurons integrate mitogenic signals with microenvironment cues to control proliferation and differentiation. We determined that the Siah2 E3 ubiquitin ligase functions in a coincidence detection circuit linking responses to the Shh mitogen and the extracellular matrix to control cerebellar granule neurons (CGN) germinal zone (GZ) occupancy. We found that Shh maintains Siah2 expression in CGN progenitors (GNPs) in a Ras/Mapk-dependent manner. Siah2 supports ciliogenesis in a feed-forward fashion by restraining ciliogenic targets. Efforts to identify GZ sources of Ras/Mapk signaling led us to discover that GNPs respond to laminin, but not vitronectin, in the microenvironment via integrin {beta}1 receptors, which engages the Ras/Mapk cascade, and that this niche interaction is essential for promoting GNP ciliogenesis. As GNPs leave the GZ, differentiation is seamlessly driven by changing extracellular cues that diminish Siah2-activity leading to primary cilia retraction and attenuation of mitogenic responses.

neuroscience↗