Biology subjects

Rao, G.

Publications and source records attributed to Rao, G..

At least 19 recordsLinked to original sources

bioRxiv2026

Protein Scaffolds Modulate the Electronic Structure of a Common Ketyl Radical Intermediate in Thiamine Pyrophos-phate-Dependent Radical Biocatalysis: Insights from EPR and ENDOR Spectroscopy

New-to-nature radical biocatalysis has emerged as a powerful strategy for asymmetric C--C bond formation, yet the enzyme-bound radi-cal intermediates that underpin these transformations have remained largely uncharacterized. Here, we combine photo biocatalytic reaction development with multifrequency electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) spectroscopy, and density functional theory (DFT) calculations to elucidate the ketyl radical intermediates formed during thiamine pyrophosphate (TPP)-dependent radical biocatalysis. We first develop an oxidative photobiocatalytic cross-coupling of aldehydes with alkyltri-fluoroborates catalyzed by engineered benzoylformate decarboxylase (BFD) variants, providing enantioenriched -chiral ketones through a new oxidative radical manifold inaccessible to benzaldehyde lyases (BALs). Freeze-quench multifrequency EPR and ENDOR spectroscopy directly identify the catalytically generated TPP-bound ketyl radical and reveal that this common radical intermediate adopts distinct electronic structures in BFD and BAL despite their identical chemical composition. Analysis of 1H, 19F, 31P, and 14N hyper-fine interactions, together with DFT calculations, demonstrates that enzyme-specific active-site conformations redistribute spin density between the TPP cofactor and substrate fragment. Greater substrate-centered spin delocalization in BFD provides a mechanistic basis for its superior radical C--C coupling activity relative to BAL. These results establish a direct relationship between protein-controlled electronic structure and catalytic function in TPP-dependent radical biocatalysis and demonstrate that engineering the electronic properties of a common radical intermediate represents a useful strategy for controlling enzyme reactivity in radical biocatalysis.

biochemistry↗

bioRxiv2026

Homozygosity for rare or common hypomorphic IL23R variants confers a predisposition to tuberculosis in humans

Homozygosity for rare loss-of-function IL23R variants abolishes IL-23-dependent IFN-{gamma} production by lymphocytes, including NK and innate-like T cells, thereby underlying clinical disease due to weakly virulent mycobacterial species. We report selective enrichment in homozygosity for four hypomorphic IL23R variants in our cohort of patients with tuberculosis. Three of these IL23R alleles are rare (G300V, G149R, and L372F), with a minor allele frequency (MAF) under 1%, but the fourth (R381Q) is surprisingly common, with an MAF as high as 10.2% in certain populations. The other 15 missense alleles found in the homozygous state in public databases are isomorphic. The four hypomorphic IL-23R variants identified dimerize with IL-12R{beta}1 and bind IL-23. However, their function is impaired by low levels of cell surface expression (R381Q, G300V) and/or as a consequence of conformational changes altering agonist efficacy. IFN-{gamma} production in response to IL-23 is impaired in innate-like T cells and NK cells. These data suggest that recessive partial IL-23R deficiency, whether due to rare or common variants, confers a predisposition to tuberculosis while preserving immunity to less virulent mycobacteria. One sentence summaryHomozygous hypomorphic IL23R variants impair IL-23-dependent IFN-{gamma} production and underlie tuberculosis.

genetics↗

bioRxiv2025

Cystathionine Beta-Synthase Promotes Anoikis Resistance and Transcoelomic Metastasis in Ovarian Cancer via the SP1-ITGB1 axis

Anoikis resistance is crucial for ovarian cancer (OvCa) transcoelomic metastasis, during which exfoliated OvCa cells survive as spheroids before invading the omentum. Here, we demonstrate that cystathionine {beta}-synthase (CBS), an H2S-producing transsulfuration pathway enzyme, is a key determinant of OvCa spheroidal viability and metastatic potential. Analysis of publicly available patient datasets, as well as an in-house tissue microarray, revealed that high CBS expression positively correlates with both poor progression-free survival and clinically observed peritoneal/omental metastasis. Integrated functional and proteomic analyses indicated that CBS silencing induces apoptosis in 2D monolayers. Consistent with this, CBS silencing in spheroids caused apoptosis and disrupted spheroid architecture. Mechanistically, this phenotype was associated with downregulation of oncogenic stemness and epithelial-mesenchymal transition. Further, through proteomic and bioinformatic analyses, we identified ITGB1 to be the hub protein in OvCa spheroidogenesis. Interestingly, knockdown of CBS led to abrogation of the ITGB1-mediated downstream pathway. Moreover, by proteomic and network analyses, we identified SP1 as a key transcriptional regulator of CBS-induced pro-spheroidal transcriptional programs of stemness and invasiveness. Stabilization of SP1 through persulfidation by H2S supplementation restored spheroidal viability and underlying protein signaling. Further, our results reveal that loss of CBS, through ITGB1 repression, disrupts spheroid architecture, leading to reduced metastatic docking on the murine omental surface in vivo. Collectively, these findings identify CBS as a central regulator of anoikis resistance and OvCa transcoelomic metastasis, highlighting the therapeutic potential of targeting CBS-dependent SP1-ITGB1 regulation to control metastatic spread.

cancer biology↗

bioRxiv2025

Design-driven optimization of low-cost reagent formulations for reproducible and high-yielding cell-free gene expression

Access to recombinant proteins is vital in basic science and biotechnology research. Cell-free gene expression systems provide one approach to address this need, but widespread utilization remains limited by the cost, complexity, and inconsistency of current platforms. To address these limitations, we carry out a multi-dimensional definitive screening design to reduce the number of reagent components and remove costly secondary energy substrates. From more than 1,200 reagent formulations, we discover a simple and reproducible system based on 12 components. The optimized reagent formulation can produce 2.4 {+/-} 0.3 g/L of protein product at the 15-L scale ([~]$55/gprotein) and 3.7 {+/-} 0.2 g/L ([~]$36/gprotein) at the 4-mL scale with oxygen supplementation. This provides an 84 to 99% reduction in cost over previous cell-free reagent formulations. We further show that the optimized reagent formulation can produce nucleoside triphosphates from nucleotides and ribose and that it is robust to failure across batches of cell lysates, users/locations, and in the synthesis of different proteins. Specifically, we demonstrate the production of fifteen therapeutically relevant products, including full-length aglycosylated monoclonal antibodies. We anticipate that our optimized reagent formulation will further democratize the use of cell-free systems for protein manufacturing and synthetic biology applications.

synthetic biology↗

bioRxiv2025

Viral adsorption to Moore swabs in passive wastewater sampling

Moore swabs have been used extensively for passive sampling in wastewater surveillance, typically yielding presence/absence information for targets of interest. Quantitative analysis of Moore swab data is only possible if target uptake is well characterized, specifically the relationship between quantity of the target in the liquid sample matrix and the quantity of target sorbing to the Moore swab as a function of time. The mechanism of Moore swab absorption remains unclear and is important to understand toward using them more quantitatively. We conducted viral adsorption and desorption experiments using nonpathogenic SARS-CoV-2 surrogates: {Phi}6, MHV, and BCoV as well as heat-inactivated Zika virus (ZIKV). We fit empirical adsorption data from batch experiments to Langmuir, Freundlich and Redlich-Peterson isotherm models. We observed the adsorption behavior of viral targets onto Moore swabs is best characterized by the Redlich-Peterson isotherm model. Moore swabs retained the highest viral RNA concentrations after exposure durations between 9-12 hours in the presence of target microbes during kinetic viral adsorption experiments. The results inform current and future use of Moore swabs to produce quantitative data during wastewater surveillance, especially in settings where composite sampling remains infeasible. ImportanceThis paper describes the adsorption behavior of viruses and bacteriophages to Moore swabs. Passive sampling via Moore swabs is among the most scalable form of passive wastewater sampling, considered critical to advance wastewater surveillance globally. But key unknowns constrain the utility of Moore swabs and all passive sampling approaches, including the quantitative relationship between targets in wastewater and recovery via Moore swabs. Practical questions such as how long they should be deployed and whether they can be interpreted quantitatively really depend on a characterization of viral target loading behaviors on Moore swab material as a function of time and concentration in the wastewater. Here, we use an approach that is seldom applied to microbial targets to examine adsorption behavior of viruses to Moore swabs, deriving isotherms that describe the relationships between concentration of the viral targets in wastewater and time on attachment to swab material. This is a critical step in advancing the application of Moore swab passive sampling for wastewater surveillance, with potential relevance to other microbial targets of interest.

microbiology↗

bioRxiv2025

On-demand insulin manufacturing using cell-free systems with an "on-column" conversion approach

Recent studies project that the prevalence of diabetes is expected to increase significantly and lead to escalating demand on the insulin supply chain. Despite being the first recombinant therapeutic approved by the FDA, insulin remains challenging to access for many around the globe. Here we report on advancements in manufacturing insulin using cell-free protein synthesis (CFPS) systems to rapidly produce mature desB30-insulin in less than a day. This is a major advance towards decentralizing insulin manufacturing and bringing production closer to the point-of-care, thereby improving diabetic patient accessibility. To this end, a purified cell-free extract, PUREfrex(R) 2.1, was utilized to synthesize a tagged proinsulin construct that can be captured and converted into mature insulin using an on-column affinity chromatography process. Notably, two chaperones, peptidyl prolyl isomerase (FkpA), and seven kilodalton protein (Skp) were observed to play a critical role during cell-free expression of proinsulin. The proinsulin was then immobilized on a Ni-NTA column where the purification and conversion of cell-free products were performed sequentially to yield desB30-insulin. Following further optimization, this method serves as a time and resource-efficient production process as compared to current methods. When applied simultaneously, the cell-free expression and on-column conversion methods reported here can be adopted to enable rapid on-demand insulin manufacturing in order to improve the accessibility of insulin and prevent future shortages.

synthetic biology↗

bioRxiv2025

Mutant IDH impairs chromatin binding by PDGFB to promote chromosome instability

Non-canonical roles for growth factors in the nucleus have been previously described, but their mechanism of action and biological roles remain enigmatic. Platelet-derived growth factor B (PDGFB) can drive formation of low-grade glioma and here we show that it localizes to the nucleus of human glioma cells where it binds chromatin to preserve genome stability and cell lineage. Failure of PDGFB to localize to the nucleus leads to chromosomal abnormalities, aberrant heterochromatin architecture and accelerated tumorigenesis. Furthermore, nuclear localization of PDGFB is reliant upon the expression levels and mutation status of isocitrate dehydrogenase (IDH). Unexpectedly, we identified macrophages as the predominant source of PDGFB in human, finding that immune-derived PDGFB can localize to the nucleus of glioma cells. Collectively, these studies show that immune derived PDGFB enters the nucleus of glioma cells to maintain genomic stability, while identifying a new mechanism by which IDH mutations promote gliomagenesis.

cancer biology↗

bioRxiv2024

Cell type transcriptional identities are maintained in cultured ex vivo human brain tissue

It is becoming more broadly accepted that human-based models are needed to better understand the complexities of the human nervous system and its diseases. The recently developed human brain organotypic culture model is one highly promising model that requires the involvement of neurosurgeons and neurosurgical patients. Studies have investigated the electrophysiological properties of neurons in such ex vivo human tissues, but the maintenance of other cell types within explanted brain remains largely unknown. Here, using single-nucleus RNA sequencing, we systematically evaluate the transcriptional identities of the various cell types found in six patient samples after fourteen days in culture (83,501 nuclei from day 0 samples and 45,738 nuclei from day 14 samples). We used two pediatric temporal lobectomy samples, an adult frontal cortex sample, two IDH wild-type glioblastoma samples, and one medulloblastoma sample. We found remarkably high correlations of day 14 transcriptional identities to day 0 tissue, especially in tumor cells (r = 0.90 to 0.93), though microglia (r = 0.86), oligodendrocytes (r = 0.80), pericytes (r = 0.77), endothelial cells (r = 0.78), and fibroblasts (r = 0.76) showed strong preservation of their transcriptional profiles as well. Astrocytes and excitatory neurons showed more moderate preservation (r = 0.66 and 0.47, respectively). Because the main difficulty with organotypic brain cultures is the acquisition of human tissue, which is readily available to neurosurgeons, this model is easily accessible to neurosurgeon-scientists and neurosurgeons affiliated with research laboratories. Broad uptake of this more representative model should prompt advances in our understanding of many uniquely human diseases, lead to more reliable clinical trial performance, and ultimately yield better therapies for our patients.

neuroscience↗

bioRxiv2024

The impact of transplant location on the gut microbiome and resistome in patients undergoing hematopoietic stem cell transplantation at home versus in the hospital

ObjectivesHome-based hematopoietic stem cell transplantation (HCT) is a novel approach that has the potential to improve outcomes, however, the impact of transplant location on the gut microbiome remains uncharacterized. We hypothesized that patients randomized to undergo home HCT would have higher gut taxonomic diversity and lower antimicrobial resistance (AMR) gene abundance compared to those undergoing standard hospital HCT. MethodsWe identified 28 patients enrolled in Phase II randomized trials of home (n=16) v. hospital (n=12) HCT at Duke and performed shotgun metagenomic sequencing of stools to compare taxonomic and AMR gene composition between groups. We performed a secondary analysis of patients from each group transplanted at an outpatient infusion clinic with those who underwent standard inpatient HCT ("outpatient" v. "inpatient"). ResultsNo significant differences in duration of hospitalization were found in those randomized to home v. hospital HCT. Taxonomic and AMR gene - and {beta}-diversity were comparable. In contrast, secondary analyses demonstrated that patients from both home and hospital groups transplanted at an outpatient infusion clinic spent significantly less time in the hospital and demonstrated higher taxonomic -diversity and differential {beta}-diversity compared to standard inpatient HCT, although AMR gene -diversity did not differ, and comparisons were confounded by both differences in transplant type and use of antibiotics. ConclusionsRandomization by transplant location did not impact the gut microbiota to the same extent as the duration of hospitalization, although secondary analyses were heavily confounded. Even when taxonomic differences were observed, AMR genes were similar between groups.

microbiology↗

bioRxiv2024

Common AAV gene therapy vectors show indiscriminate transduction of living human brain cell types

The development of cell-type-specific gene therapy vectors for treating neurological diseases holds great promise, but has relied on animal models with limited translational utility. We have adapted an ex vivo organotypic model to evaluate adeno-associated virus (AAV) transduction properties in living slices of human brain tissue. Using fluorescent reporter expression and single-nucleus RNA sequencing, we found that common AAV vectors show broad transduction of normal cell types, with protein expression most apparent in astrocytes; this work introduces a pipeline for identifying and optimizing AAV gene therapy vectors in human brain samples.

bioengineering↗

bioRxiv2024

Inferred Developmental Origins of Brain Tumors from Single Cell RNA-Sequencing Data

The reactivation of neurodevelopmental programs in cancer highlights parallel biological processes that occur in both normal development and brain tumors. Achieving a deeper understanding of how dysregulated developmental factors play a role in the progression of brain tumors is therefore crucial for identifying potential targets for therapeutic interventions. Single-cell RNA sequencing (scRNA-Seq) provides an opportunity to understand how developmental programs are dysregulated and reinitiated in brain tumors at single-cell resolution. Here, we introduce COORS (Cell Of ORigin like CellS), as a computational tool trained on developmental human brain single-cell datasets that enables annotation of "developmental-like" cell states in brain tumor cells. Applying COORS to various brain cancer datasets, including medulloblastoma (MB), glioma, and diffuse midline glioma (DMG), we identified developmental-like cells that represent putative cells of origin in these tumors. Our work adds to our cumulative understanding of brain tumor heterogeneity and helps pave the way for tailored treatment strategies.

bioinformatics↗

bioRxiv2024

Spiking GABAergic OPC tumor cells prolong survival in IDH1 mutant glioma

Prior studies have described the complex interplay that exists between glioma cells and neurons, however, the electrophysiological properties endogenous to tumor cells remain obscure. To address this, we employed Patch-sequencing on human glioma specimens and found that one third of patched cells in IDH mutant (IDHmut) tumors demonstrate properties of both neurons and glia by firing single, short action potentials. To define these hybrid cells (HCs) and discern if they are tumor in origin, we developed a computational tool, Single Cell Rule Association Mining (SCRAM), to annotate each cell individually. SCRAM revealed that HCs represent tumor and non-tumor cells that feature GABAergic neuron and oligodendrocyte precursor cell signatures. These studies are the first to characterize the combined electrophysiological and molecular properties of human glioma cells and describe a new cell type in human glioma with unique electrophysiological and transcriptomic properties that are likely also present in the non-tumor mammalian brain.

cancer biology↗

bioRxiv2024

Multiplexing of temporal and spatial information in the lateral entorhinal cortex

Episodic memory involves the processing of spatial and temporal aspects of personal experiences. The lateral entorhinal cortex (LEC) plays an essential role in subserving memory. However, the specific mechanism by which LEC integrates spatial and temporal information remains elusive. Here, we recorded LEC neurons while rats performed foraging and shuttling behaviors on one-dimensional, linear or circular tracks. Unlike open-field foraging tasks, many LEC cells displayed spatial firing fields in these tasks and demonstrated selectivity for traveling directions. Furthermore, some LEC neurons displayed changes in the firing rates of their spatial rate maps during a session, a phenomenon referred to as rate remapping. Importantly, this temporal modulation was consistent across sessions, even when the spatial environment was altered. Notably, the strength of temporal modulation was found to be greater in LEC compared to other brain regions, such as the medial entorhinal cortex (MEC), CA1, and CA3. Thus, the spatial rate mapping observed in LEC neurons may serve as a coding mechanism for temporal context, allowing for flexible multiplexing of spatial and temporal information.

neuroscience↗

bioRxiv2023

Remote neuronal activity drives glioma infiltration via Sema4f

The tumor microenvironment (TME) plays an essential role in malignancy and neurons have emerged as a key component of the TME that promotes tumorigenesis across a host of cancers. Recent studies on glioblastoma (GBM) highlight bi-directional signaling between tumors and neurons that propagates a vicious cycle of proliferation, synaptic integration, and brain hyperactivity; however, the identity of neuronal subtypes and tumor subpopulations driving this phenomenon are incompletely understood. Here we show that callosal projection neurons located in the hemisphere contralateral to primary GBM tumors promote progression and widespread infiltration. Using this platform to examine GBM infiltration, we identified an activity dependent infiltrating population present at the leading edge of mouse and human tumors that is enriched for axon guidance genes. High-throughput, in vivo screening of these genes identified Sema4F as a key regulator of tumorigenesis and activity-dependent infiltration. Furthermore, Sema4F promotes the activity-dependent infiltrating population and propagates bi-directional signaling with neurons by remodeling tumor adjacent synapses towards brain network hyperactivity. Collectively, our studies demonstrate that subsets of neurons in locations remote to primary GBM promote malignant progression, while revealing new mechanisms of tumor infiltration that are regulated by neuronal activity.

cancer biology↗

bioRxiv2023

Enzymatic Hydroxylation of Aliphatic C-H Bonds by a Mn/Fe Cofactor

Manganese cofactors activate strong chemical bonds in many essential enzymes. Yet very few manganese-dependent enzymes are known to functionalize ubiquitous carbon-hydrogen (C-H) bonds, and those that catalyze this important reaction display limited intrinsic reactivity. Herein, we report that the 2-aminoisobutyric acid hydroxylase from Rhodococcus wratislaviensis requires manganese to functionalize a C-H bond possessing a bond dissociation enthalpy (BDE) exceeding 100 kcal/mol. Structural and spectroscopic studies of this enzyme reveal a redox-active, heterobimetallic manganese-iron active site that utilizes a manganese ion at the locus for O2 activation and substrate coordination. Accordingly, this enzyme represents the first documented Mn-dependent monooxygenase in biology. Related proteins are widespread in microorganisms suggesting that many uncharacterized monooxygenases may utilize manganese-containing cofactors to accomplish diverse biological tasks.

biochemistry↗

bioRxiv2022

An approach to rapid distributed manufacturing of broad spectrum anti-viral griffithsin using cell-free systems to mitigate pandemics

This study describes the cell-free biomanufacturing of a broad-spectrum antiviral protein, griffithsin (GRFT) such that it can be produced with consistent purity and potency in less than 24 hours. We demonstrate GRFT production using two independent cell-free systems, one plant and one microbial. Griffithsin purity and quality were verified using standard regulatory metrics. Efficacy was demonstrated in vitro against SARS-CoV-2 and HIV-1 and was nearly identical to that of GRFT expressed in vivo. The proposed production process is efficient and can be readily scaled up and deployed anywhere in the world where a viral pathogen might emerge. The current emergence of viral variants has resulted in frequent updating of existing vaccines and loss of efficacy for front-line monoclonal antibody therapies. Proteins such as GRFT with its efficacious and broad virus neutralizing capability provide a compelling pandemic mitigation strategy to promptly suppress viral emergence at the source of an outbreak.

bioengineering↗

bioRxiv2022

Diversified repertoire of phage defenses in Klebsiella pneumoniae: Bi-directional steering effects impacting antibiotic susceptibility

Bacteriophage (phage) therapy is rising as a promising anti-infective option to combat antimicrobial resistance; however, its clinical utilization is severely hindered by the potential emergence of phage resistance. Fortunately, certain phage resistance mechanisms can restore bacterial antibiotic susceptibility, making the combination of phages with antibiotics a potential strategic approach. Here, we demonstrated that phage resistance can also lead to increased antibiotic resistance and provided mechanistic insights into bacterial phage defense mechanisms. We discovered a repertoire of phage resistance mechanisms in Klebsiella pneumoniae, including the disruption of phage binding site (fhuA::Tn and tonB::Tn), extension of phage latent period (mnmE::Tn and rpoN::Tn) and increased mutation frequency (mutS::Tn and mutL::Tn). Different from the prevailing view that phage resistance re-sensitizes antibiotic-resistant bacteria, we revealed a bidirectional steering effect on the bacterial antibiotic susceptibility. Specifically, it was uncovered that, while rpoN::Tn became more susceptible to colistin, mutS::Tn and mutL::Tn caused increased resistance to rifampicin and colistin. Our findings highlight the diversified strategies utilized by K. pneumoniae to overcome phage infection and the parallel effect on the antibiotic susceptibility. Mechanism-guided phage steering represents a rational strategy that should be incorporated into phage therapy to better inform clinical decisions.

microbiology↗

bioRxiv2022

Identification of functional immune and neuronal tumor cells in glioma

Despite advances in molecular profiling, therapeutic development has been hindered by the inability to identify and target tumour-specific mechanisms without consequence to healthy tissue. Correspondingly, a computational framework capable of accurately distinguishing tumour from non-tumour cells has yet to be developed and cell annotation algorithms are unable to assign integrated genomic and transcriptional profiles to single cells on a cell-by-cell basis. To address these barriers, we developed the Single Cell Rule Association Mining (SCRAM) tool that integrates RNA-inferred genomic alterations with co-occurring cell type signatures for individual cells. Applying SCRAM to glioma, we identified tumour cell trajectories recapitulate temporally-restricted developmental paradigms and feature unique co-occurring identities. Specifically, we validated two previously unreported tumour cell populations with immune and neuronal signatures as hallmarks of human glioma subtypes. In vivo modeling revealed a rare immune-like tumour cell population resembling antigen presenting cells can direct CD8+ T cell responses. In parallel, Patch sequencing studies in human tumours confirmed that neuronal-like glioma cells fire action potentials and represent 40% of IDH1 mutant tumor cells. These studies identified new glioma cell types with functional properties similar to their non-tumour analogues and demonstrate the ability of SCRAM to identify these cell types in unprecedented detail.

cancer biology↗