bioRxiv Science⌕ Search

Biology subjects

Joseph, D.

Publications and source records attributed to Joseph, D..

6 recordsLinked to original sources

In Vivo Transcriptomics-Based Framework for Systematic Indication Expansion

Capturing the systemic effects of drugs in vivo remains a fundamental challenge for drug repurposing strategies. Here, we present an in vivo transcriptomics-based drug repurposing framework that profiles multi-organ RNA-seq from drug-treated rodents to model systemic drug responses and match tissue-specific drug signatures against a compendium of disease signatures for indication expansion. We applied this framework to semaglutide, a GLP-1 receptor agonist originally developed for diabetes and subsequently expanded for several other indications. By harmonizing more than 900 human disease transcriptomic signatures via agentic AI and using Z-transformed reversal of gene expression scoring to quantify drug-disease relationships, our approach successfully recovered established semaglutide indications while deprioritizing Alzheimers disease, an indication for which semaglutide was not effective. Top predictions for common diseases were supported by real-world electronic health record data from the Mount Sinai Health System and several predictions for rare indications are proposed for further investigation. This framework provides a scalable strategy for indication expansion across diverse therapeutic agents, especially investigational compounds for which real-world evidence remains sparse.

systems biology↗

Activity-dependent FosB gene expression negatively regulates mast cell functions.

Mast cells are innate immune cells that regulate physiological processes by releasing pre-stored and newly synthesized mediators in response to allergens, infection, and other stimuli. Dysregulated mast cell activity can lead to multisystemic pathologies, but the underlying regulatory mechanisms remain poorly understood. We found that FOSB and {Delta}FOSB, transcription factors encoded by the FosB gene, are robustly expressed in mast cells following IgE-antigen stimulation, suggesting a role in modulating stimulus-induced mast cell functions. Using phenotypic, gene binding, and gene expression analyses in wild-type and mast cell-specific FosB knockout male mice, we demonstrate that FOSB/{Delta}FOSB modulates mast cell functions by limiting reactivity to allergen-like stimuli both in vitro and in vivo. These effects seem to be mediated, at least in part, by FOSB/{Delta}FOSB-driven enhanced expression of DUSP4, a dual-specificity phosphatase that attenuates MAPK signaling. These findings highlight FOSB/{Delta}FOSB as critical regulators of mast cell activity and potential targets for therapeutic intervention. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/592755v2_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@190be2corg.highwire.dtl.DTLVardef@1b53f9borg.highwire.dtl.DTLVardef@631997org.highwire.dtl.DTLVardef@250bc7_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

Metabotropic signaling within somatostatin interneurons regulates thalamocortical inputs during development

During brain development, neural circuits undergo major activity-dependent restructuring. Circuit wiring mainly occurs through synaptic strengthening following the Hebbian "fire together, wire together" precept. However, select connections, essential for circuit development, are transient. They are effectively connected early in development, but strongly diminish during maturation. The mechanisms by which transient connectivity recedes are unknown. To investigate this process, we characterize transient thalamocortical inputs, which depress onto somatostatin inhibitory interneurons during development, by employing optogenetics, chemogenetics, transcriptomics and CRISPR-based strategies. We demonstrate that in contrast to typical activity-dependent mechanisms, transient thalamocortical connectivity onto somatostatin interneurons is non-canonical and involves metabotropic signaling. Specifically, metabotropic-mediated transcription, of guidance molecules in particular, supports the elimination of this connectivity. Remarkably, we found that this developmental process impacts the development of normal exploratory behaviors of adult mice.

neuroscience↗

Short-chain di-carboxylates as positive allosteric modulators of the pH-dependent pentameric ligand-gated ion channel GLIC: requirement of an intact vestibular pocket

GLIC is a prokaryotic orthologue of brain pentameric neurotransmitter receptors. Using whole-cell patch-clamp electrophysiology in a host cell line, we show that short-chain di-carboxylate compounds are positive modulators of pHo 5-evoked GLIC activity, with a rank order of action fumarate > succinate > malonate > glutarate. Potentiation by fumarate depends on intracellular pH, mainly as a result of a strong decrease of the pHo 5-evoked current when intracellular pH decreases. The modulating effect of fumarate also depends on extracellular pH, as fumarate is a weak inhibitor at pHo 6 and shows no agonist action at neutral pHo. A mutational analysis of residue-dependency for succinate and fumarate effects, based on two carboxylate-binding pockets previously identified by crystallography (Fourati et al. 2020), shows that positive modulation involves both the inter-subunit pocket, homologous to the neurotransmitter-binding orthotopic site, and the intra-subunit (also called vestibular) pocket. An almost similar pattern of mutational impact is observed for the effect of caffeate, a known negative modulator. We propose, for both di-carboxylate compounds and caffeate, a model where the inter-subunit pocket is the actual binding site, and the region corresponding to the vestibular pocket is required either for inter-subunit binding itself, or for binding-to-gating coupling during the allosteric transitions involved in pore gating modulation. Key points summaryO_LIUsing a bacterial orthologue of brain pentameric neurotransmitter receptors, we show that the orthotopic/orthosteric agonist site and the adjacent vestibular region are functionally inter-dependent in mediating compound-elicited modulation. We propose that the two sites in the extracellular domain are involved "in series", a mechanism which may have relevance to Eukaryote receptors. C_LIO_LIWe show that short-chain di-carboxylate compounds are positive modulators of GLIC. The most potent compound identified is fumarate, known to occupy the orthotopic/orthosteric site in previously published crystal structures. C_LIO_LIWe show that intracellular pH modulates GLIC allosteric transitions, as previously known for extracellular pH. C_LIO_LIWe report a caesium to sodium permeability ratio (PCs/PNa) of 0.54 for GLIC ion pore. C_LI

neuroscience↗

Biochemical characterization of a GDP-mannose transporter from Chaetomium thermophilum

Nucleotide Sugar Transporters (NSTs) belong to the SLC35 family (human solute carrier) of membrane transport proteins and are crucial components of the glycosylation machinery. NSTs are localized in the ER and Golgi apparatus membranes, where they accumulate nucleotide sugars from the cytosol for subsequent polysaccharide biosynthesis. Loss of NST function impacts the glycosylation of cell surface molecules. Mutations in NSTs cause several developmental disorders, immune disorders, and increased susceptibility to infection. Atomic resolution structures of three NSTs have provided a blueprint for a detailed molecular interpretation of their biochemical properties. In this work, we have identified, cloned, and expressed 18 members of the SLC35 family from various eukaryotic organisms in Saccharomyces cerevisiae. Out of 18 clones, we determined Vrg4 from Chaetomium thermophilum (CtVrg4) is a GDP-mannose transporter with an enhanced melting point temperature (Tm) of 56.9 {degrees}C, which increases with the addition of substrates, GMP and GDP-mannose. In addition, we report--for the first time--that the CtVrg4 shows an affinity to bind to phosphatidylinositol lipids.

biochemistry↗

Structural basis of norepinephrine recognition and transport inhibition in neurotransmitter transporters

Norepinephrine is a biogenic amine neurotransmitter that has widespread effects on cardiovascular tone, alertness and sensation of pain. As a consequence, blockers of norepinephrine uptake have served as vital tools to treat depression and chronic pain. Here, we employ a modified Drosophila melanogaster dopamine transporter as a surrogate for the human norepinephrine transporter and determine the X-ray structures of the transporter in its substrate-free and norepinephrine-bound forms. We also report structures of the transporter in complex with inhibitors of chronic pain including duloxetine, milnacipran and a synthetic opioid, tramadol. When compared to dopamine, we observe that norepinephrine binds in a different pose, in the vicinity of subsite C within the primary binding site. Our experiments reveal that this region is the binding site for chronic pain inhibitors and a determinant for norepinephrine-specific reuptake inhibition, thereby providing a paradigm for the design of specific inhibitors for catecholamine neurotransmitter transporters. HighlightsO_LIX-ray structures of the Drosophila dopamine transporter in substrate-free and norepinephrine bound forms. C_LIO_LINorepinephrine and dopamine bind in distinct conformations within the binding pocket. C_LIO_LIChronic pain inhibitors S-duloxetine, milnacipran and tramadol bind in the primary binding site and overlap with the norepinephrine-binding pose. C_LIO_LISelective norepinephrine reuptake inhibition occurs through specific interactions at the subsite C in the primary binding pocket. C_LI

biochemistry↗