Biology subjects

Xie, T.

Publications and source records attributed to Xie, T..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Molecular mechanism of Na+/H+ antiporting in NhaA

Sodium-proton antiporter NhaA of Escherichia coli is a paradigm to investigate the mechanistic basis of the fundamental Na+/H+ exchange in cells. However, all existing crystal structures of NhaA are inward-facing (IF) and the putative outward-facing (OF) structures are still unsolved by experiment, limiting a complete understanding of the transport cycle where Lys300 plays a key role in both structural stability and transport function. Here, we report a set of regular molecular dynamics (MD) simulations that start from the structure predicted by an artificial intelligence method that generates function-relevant alternative conformations. It is found that NhaA rapidly relaxes into either the IF or OF conformation. Further-more, neutralization of Lys300 allows two sodium ions bound to the reaction cavity, which is associated with enhanced conformational sampling. Based on these observations, we propose a sodium-coupled mechanism of Na+/H+ antiporting.

biophysics↗

bioRxiv2024

Human single-neuron activity is modulated by intracranial theta burst stimulation of the basolateral amygdala

Direct electrical stimulation of the human brain has been used for numerous clinical and scientific applications. At present, however, little is known about how intracranial stimulation affects activity at the microscale. In this study, we recorded intracranial EEG data from a cohort of patients with medically refractory epilepsy as they completed a visual recognition memory task. During the memory task, brief trains of intracranial theta burst stimulation (TBS) were delivered to the basolateral amygdala (BLA). Using simultaneous microelectrode recordings, we isolated neurons in the hippocampus, amygdala, orbitofrontal cortex, and anterior cingulate cortex and tested whether stimulation enhanced or suppressed firing rates. Additionally, we characterized the properties of modulated neurons, clustered presumed excitatory and inhibitory neurons by waveform morphology, and examined the extent to which modulation affected memory task performance. We observed a subset of neurons ([~]30%) whose firing rate was modulated by TBS, exhibiting highly heterogeneous responses with respect to onset latency, duration, and direction of effect. Notably, location and baseline activity predicted which neurons were most susceptible to modulation, although the impact of this neuronal modulation on memory remains unclear. These findings advance our limited understanding of how focal electrical fields influence neuronal firing at the single-cell level. HighlightsIndividual neurons in the human brain were responsive to theta burst stimulation Basolateral amygdala stimulation preferentially modulated neurons in the hippocampus, orbitofrontal cortex, and amygdala Excitatory and inhibitory neurons were modulated equally Neurons modulated by stimulation tended to have greater baseline firing rates Duration, onset, and valence of neuronal modulation were heterogeneous

neuroscience↗

bioRxiv2024

Multiomics mapping and characterization of cellular senescence in aging human muscle uncovers novel senotherapeutics for sarcopenia

Cellular senescence is recognized as a hallmark of organismal aging but how it drives aging particularly in human tissues is not fully understood, partly due to the complex heterogeneous nature of senescence. Here in this study, we leverage single-nucleus multiomics to profile senescence in mononucleated cells of human skeletal muscle and provide the first senescence atlas. We demonstrate the intra-and inter-populational transcriptomic and epigenomic heterogeneity and dynamics of senescence in the cells. We also identify commonalities and variations in senescence-associated secretory phenotypes (SASPs) among the cells and elucidate the function of SASPs in mediating cellular interactions and niche deregulation. Furthermore, we identify targetable SASP factors and demonstrate the possibility of using Maraviroc as a pharmacological senotherapeutic for treating age-associated sarcopenia in muscle. Lastly, we define transcription factors that govern senescence state and SASP induction in aging muscle and elucidate the key function and the underlying mechanism of JUNB in regulating SASP activation in senescent cells. Altogether, our findings demonstrate the prevalence and function of cellular senescence in skeletal muscle and identify a novel pharmacological intervention for sarcopenia.

cell biology↗

bioRxiv2024

Orthosteric STING inhibition elucidates molecular correction of SAVI STING

STING is broadly implicated in diseases ranging from cancer, autoimmune disease, neurodegeneration to rare, monogenic diseases.1 Early drug discovery campaigns focused on STING activation as a promising platform for cancer immunotherapy yet failed in multiple clinical trials due to lack of efficacy thus far.2 Current research and development activities concentrate on STING inhibition for treating autoimmune disease and neuroinflammation. While the progression of STING activators into the clinic has been successful, the discovery and clinical progression of STING inhibitors remain elusive. Questions persist about the molecular properties needed to distinguish between a STING activator and inhibitor, particularly within SAVI disease, a monogenic autoinflammatory disease that renders STING constitutively active.3 Here we leverage an orthosteric STING activator and inhibitor from the same chemical series to discover that STING M271 is a critical residue for molecular activation. The M271CH3 NMR chemical shifts reveal a unique molecular signature for pharmacological or genetically driven activation and inhibition that is not captured by x-ray crystallography. Additionally, M271 directly interacts with the most common SAVI mutation, V155M, and using an orthosteric STING inhibitor, we show partial rescue and molecular correction of STING V155M. Finally, these data present insights into therapeutic STING molecular correction for treating SAVI patients. Our results elucidate an unappreciated structural interaction critical for STING modulation that could be utilized as a molecular diagnostic tool for drug discovery. Furthermore, we demonstrate for the first time how the therapeutic requirements of a molecular corrector differ from an orthosteric STING inhibitor, and why this is important for the SAVI disease population.

molecular biology↗

bioRxiv2024

Skeletal Muscle Stem Cells Modulate Niche Function in Duchenne Muscular Dystrophy through YY1-CCL5 Axis

Stem cell activity is known to be tightly regulated by both intrinsic and extrinsic pathways but less is known about whether and how stem cells modulate their niche microenvironment. Adult skeletal muscle stem cells (MuSCs) are indispensable for muscle regeneration and also tightly regulated by macrophages (MPs) and fibro-adipogenic progenitors (FAPs) in the niche. Deregulated MuSC/MP/FAP interactions and the ensuing inflammation and fibrosis are hallmarks of dystrophic muscle. Here in this study we demonstrate that intrinsic deletion of transcription factor YY1 in MuSCs exacerbates dystrophic pathologies by altering the cellular composition and heterogeneity of MPs and FAPs. Further analysis reveals that the YY1 loss induces the expression of immune genes in MuSCs, including Ccl5. Augmented secretion of CCL5 from MuSCs promotes the recruitment of MPs via CCL5/CCR5 mediated crosstalk, which subsequently hinders the apoptosis and clearance of FAPs through elevated TGF{beta}1 accumulation. Maraviroc mediated pharmacological blockade of the CCL5/CCR5 axis effectively mitigates muscle dystrophy and improves muscle performance. Lastly, we further demonstrate that YY1 represses Ccl5 transcription in MuSCs by directly binding to its enhancer thus facilitating promoter-enhancer looping. Altogether, our study has demonstrated the previously unappreciated role of MuSCs in actively shaping their niche microenvironment through secreting immunomodulatory cytokines, and has also provided novel insight into the therapeutic intervention of muscle dystrophy.

cell biology↗

bioRxiv2023

Conditioned Protein Structure Prediction

Deep learning based protein structure prediction has facilitated major breakthroughs in biological sciences. However, current methods struggle with alternative conformation prediction and offer limited integration of expert knowledge on protein dynamics. We introduce AFEXplorer, a generic approach that tailors AlphaFold predictions to user-defined constraints in coarse coordinate spaces by optimizing embedding features. Its effectiveness in generating functional protein conformations in accordance with predefined conditions were demonstrated through comprehensive examples. AFEXplorer serves as a versatile platform for conditioned protein structure prediction, bridging the gap between automated models and domain-specific insights.

bioinformatics↗

bioRxiv2023

Plug-and-play protein biosensors using aptamer-regulated in vitro transcription

Molecular biosensors that accurately measure protein concentrations without external equipment are critical for solving numerous problems in diagnostics and therapeutics. Modularly transducing the binding of protein antibodies, protein switches or aptamers into a useful output remains challenging. Here, we develop a biosensing platform based on aptamer-regulated transcription in which aptamers integrated into transcription templates serve as inputs to molecular circuits that can be programmed to a produce a variety of responses. We modularly design molecular biosensors using this platform by swapping aptamer domains for specific proteins and downstream domains that encode different RNA transcripts. By coupling aptamer-regulated transcription with diverse transduction circuits, we rapidly construct analog protein biosensors or digital protein biosensors with detection ranges that can be tuned over two orders of magnitude. Aptamer-regulated transcription is a straightforward and inexpensive approach for constructing programmable protein biosensors suitable for diverse research and diagnostic applications. One sentence summaryWe develop a modular platform for biosensing across a wide dynamic range using aptamer-regulated transcription to detect different proteins and molecular circuits to process the RNA transcript outputs.

bioengineering↗

bioRxiv2023

Can Protein Structure Prediction Methods Capture Alternative Conformations of Membrane Proteins?

Understanding the conformational dynamics of proteins, such as the inward-facing (IF) and outward-facing (OF) transition observed in transporters, is vital for elucidating their functional mechanisms. Despite significant advances in protein structure prediction (PSP) over the past three decades, most efforts have been focused on single-state prediction, leaving multi-state or alternative conformation prediction (ACP) relatively unexplored. This discrepancy has led to the development of highly accurate PSP methods such as AlphaFold, yet their capabilities for ACP remain limited. To investigate the performance of current PSP methods in ACP, we curated a dataset, named IOMemP, consisting of 32 experimentally determined high-resolution IF and OF structures of 16 membrane proteins. We benchmarked 12 representative PSP methods, along with two recent multi-state methods based on AlphaFold, against this dataset. Our findings reveal an escalating bias towards one specific state in deep learning-based methods and a remarkably consistent preference for specific states across various PSP methods. We elucidated how coevolution information in MSAs influences the state preference. Moreover, we showed that AlphaFold, when excluding coevolution information, estimated similar energies between the experimental IF and OF conformations, indicating that the energy model learned by AlphaFold is not biased towards any particular state. Our IOMemP dataset and benchmark results are anticipated to advance the development of robust ACP methods.

bioinformatics↗

bioRxiv2023

Extreme structural heterogeneity rewires glioblastoma chromosomes to sustain patient-specific transcriptional programs

Glioblastoma multiforme (GBM) encompasses brain malignancies marked by phenotypic and transcriptional heterogeneity thought to render these tumors aggressive, resistant to therapy, and inevitably recurrent. However, little is known about how the spatial organization of GBM genomes underlies this heterogeneity and its effects. Here, we compiled a cohort of 28 patient-derived glioblastoma stem cell-like lines (GSCs) known to reflect the properties of their tumor-of-origin; six of these were primary-relapse tumor pairs from the same patient. We generated and analyzed kbp-resolution chromosome conformation capture (Hi-C) data from all GSCs to systematically map >3,100 standalone and complex structural variants (SVs) and the >6,300 neoloops arising as a result. By combining Hi-C, histone modification, and gene expression data with chromatin folding simulations, we explain how the pervasive, uneven, and idiosyncratic occurrence of neoloops sustains tumor-specific transcriptional programs via the formation of new enhancer-promoter contacts. We also show how even moderately recurrent neoloops can help us infer patient-specific vulnerabilities. Together, our data provide a resource for dissecting GBM biology and heterogeneity, as well as for informing therapeutic approaches.

genomics↗

bioRxiv2022

Microglial process dynamics enhance neuronal activity by shielding GABAergic synaptic inputs

Microglia are resident immune cells of the central nervous system (CNS) and play key roles in brain homeostasis. During anesthesia, microglia increase their dynamic process surveillance and interact more closely with neurons. However, the functional significance of microglial process dynamics and neuronal interaction has remained unclear. Using in vivo two-photon imaging in awake mice, we discover that microglia enhance neuronal activity after the cessation of general anesthesia. Hyperactive neuron somata are directly contacted by microglial processes, which specifically co-localize with GABAergic boutons. Electron microscopy-based synaptic reconstruction after two-photon imaging reveals that microglial processes enter into the synaptic cleft to shield GABAergic inputs. Microglial ablation or loss of microglial {beta}2-adrenergic receptors prevent post-anesthesia neuronal hyperactivity. Together, our study demonstrates a previously unappreciated function of microglial process dynamics, which allow microglia to transiently boost neuronal activity by physically shielding inhibitory inputs.

neuroscience↗

bioRxiv2022

Topological Links in Predicted Protein Complex Structures Reveal Limitations of AlphaFold

AlphaFold is making great progress in protein structure prediction, not only for single-chain proteins but also for multi-chain protein complexes. When using AlphaFold-Multimer to predict protein-protein complexes, we observed some unusual structures in which chains are looped around each other to form topologically intertwining links at the interface. To our knowledge, such topological links are never observed in the experimental structures deposited in the Protein Data Bank (PDB). Although it is well known and has been well studied that protein structures may have topologically complex shapes such as knots and links, existing methods are hampered by the chain closure problem and show poor performance in identifying topologically linked structures in protein-protein complexes. Therefore, we address the chain closure problem by using sliding windows from a local perspective and propose an algorithm to measure the topological-geometric features that can be used to identify topologically linked structures. An application of the method to AlphaFold-Multimer-predicted protein complex structures finds that approximately 0.7% of the predicted structures contain topological links. The method presented in this work will facilitate the computational study of protein-protein interactions and help further improve the structural prediction of multi-chain protein complexes.

bioinformatics↗

bioRxiv2022

ATF3 Preserves Skeletal Muscle Stem Cell Quiescence by Preventing Precocious Activation

Skeletal muscle stem cells (also called satellite cells, SCs) are important for maintaining muscle tissue homeostasis and damage-induced regeneration. However, it remains poorly understood how the SC quiescence is preserved. Here we report that AP-1 family member ATF3 preserves the SC quiescence by preventing their premature activation. Atf3 is rapidly and transiently induced in SCs upon activation. Short-term deletion of Atf3 in SCs accelerates acute injury-induced regeneration, and however, its long-term deletion exhausts the SC pool and thus impairs muscle regeneration. The Atf3 loss also provokes SC activation during voluntary exercise and enhances SC activation during resistance exercise. Mechanistically, ATF3 directly activates the transcription of Histone 2B genes, which reduction accelerates nucleosome displacement and gene transcription required for SC activation. Finally, the ATF3-dependent H2B expression also prevents genome instability and replicative senescence in SCs. Therefore, this study has revealed a novel mechanism for preserving the SC population by actively suppressing precocious activation, in which ATF3 is a key regulator.

cell biology↗

bioRxiv2022

Spike-specific CXCR3+ TFH cells play a dominant functional role in supporting antibody responses in SARS-CoV-2 infection and vaccination

CD4+ T follicular helper (TFH) cells are required for high-quality antibody generation and maintenance. However, the longevity and functional role of these cells are poorly defined in COVID-19 convalescents and vaccine recipients. Here, we longitudinally investigated the dynamics and functional roles of spike-specific circulating TFH cells and their subsets in convalescents at the 2nd, 5th, 8th, 12th and 24th months after COVID-19 symptom onset and in vaccinees after two and three doses of inactivated vaccine. SARS-CoV-2 infection elicited robust spike-specific TFH cell and antibody responses, of which spike-specific CXCR3+ TFH cells but not spike-specific CXCR3- TFH cells and neutralizing antibodies were persistent for at least two years in more than 80% of convalescents who experienced symptomatic COVID-19, which was well coordinated between spike-specific TFH cell and antibody responses at the 5th month after infection. Inactivated vaccine immunization also induced spike-specific TFH cell and antibody responses; however, these responses rapidly declined after six months with a two-dose standard administration, and a third dose significantly promoted antibody maturation and potency. Functionally, spike-specific CXCR3+ TFH cells exhibited better responsiveness than spike-specific CXCR3- TFH cells upon spike protein stimulation in vitro and showed superior capacity in supporting spike-specific antibody secreting cell (ASC) differentiation and antibody production than spike-specific CXCR3- TFH cells cocultured with autologous memory B cells. In conclusion, spike-specific CXCR3+ TFH cells played a dominant functional role in antibody elicitation and maintenance in SARS-CoV-2 infection and vaccination, suggesting that induction of CXCR3-biased spike-specific TFH cell differentiation will benefit SARS-CoV-2 vaccine development aiming to induce long-term protective immune memory. HighlightsO_LISARS-CoV-2 infection elicited robust spike-specific TFH cell and antibody responses, which persisted for at least two years in the majority of symptomatic COVID-19 convalescent patients. C_LIO_LIInactivated vaccine immunization also elicited spike-specific TFH cell and antibody responses, which rapidly declined over time, and a third dose significantly promoted antibody maturation and potency. C_LIO_LISpike-specific CXCR3+ TFH cells exhibited more durable responses than spike-specific CXCR3- TFH cells, correlated with antibody responses and showed superior capacity in supporting ASC differentiation and antibody production than spike-specific CXCR3- TFH cells. C_LI

immunology↗

bioRxiv2022

Self-organized anteroposterior regionalization of early midbrain and hindbrain using micropatterned human embryonic stem cells

Anterior-posterior (AP) spatial regionalization is crucial for central nervous system development. Previous studies suggest that morphogen gradients can induce AP patterning in animal and organoid models. While self-organization in early embryogenesis and neurogenesis has been found using geometrically confined microtissues, spontaneously induced AP patterning has not been reported. Here, we show that circularly micropatterned human pluripotent stem cells self-organize into spatially distinct FOXG1-FOXA1+OTX2+ midbrain-like and HOXB4+ hindbrain/spinal cord-like regions. Notably, the tissue then folds inwardly to form a 3D annular structure, maintaining a distinct boundary between OTX2+ and HOXB4+ zones. The reaction-diffusion of BMP/Noggin plays a key role in the mechanism of AP patterning. Our model is validated by its capability to distinguish the teratogenic effects of valproic acid and isotretinoin. Our work suggests a novel regulatory mechanism for AP patterning and provides a tool for fast screening of teratogens.

bioengineering↗

bioRxiv2022

Identification of pre-existing microbiome and metabolic vulnerabilities to escalation of oxycodone self-administration and identification of a causal role of short-chain fatty acids in addiction-like behaviors.

The gut brain axis is thought to play a role in behavior and physiological responses through chemical, immunological, and metabolite signaling. Antibiotics, diet, and drugs can alter the transit time of gut contents as well as the makeup of the microbiome. Heterogeneity in genetics and environment are also well-known factors involved in the initiation and perpetuation of substance use disorders. Few viable genetic or biological markers are available to identify individuals who are at risk of escalating opioid intake. Primarily, the addiction field has focused on the nervous system, limiting the discovery of peripheral factors that contribute to addiction. To address this gap, we characterized the microbiome before and after drug exposure, and after antibiotics depletion in male and female heterogenous stock rats to determine if microbiome constituents are protective of escalation. We hypothesized that individuals that are prone to escalation of opioid self-administration will have distinct microbial and metabolic profiles. The fecal microbiome and behavioral responses were measured over several weeks of oxycodone self-administration and after antibiotic treatment. Antibiotic treatment reduces circulating short-chain fatty acids (SCFA) by depleting microbes that ferment fiber into these essential signaling molecules for the gut-brain axis. Depletion of the microbiome increased oxycodone self-administration in a subpopulation of animals (Responders). Supplementation of SCFAs in antibiotic depleted animals decreased elevated oxycodone self-administration. Phylogenetic functional analysis reveals distinct metabolic differences in the subpopulations of animals that are sensitive to antibiotic depletion and animals rescued by SCFA supplementation. In conclusion, this study identifies pre-existing microbiome and metabolic vulnerabilities to escalation of oxycodone self-administration, demonstrates that escalation of oxycodone self-administration dysregulates the microbiome and metabolic landscape, and identifies a causal role of short-chain fatty acids in addiction-like behaviors.

neuroscience↗

bioRxiv2022

Droplet-based microfluidics as a media optimization tool for cyanobacteria

The urgent need to increase sustainability in biotechnology has led to an increased interest in photosynthetic production platforms. Cyanobacteria are particularly attractive for their fast photoautotrophic growth and genetic accessibility. However, the lack of systematic strain optimization is holding back progress towards industrialization. To overcome this bottleneck, here we introduce a droplet-based microfluidics platform capable of one- (1D) and two-dimension (2D) screening of key parameters in cyanobacterial cultivation. We successfully grew three different unicellular, biotechnologically relevant cyanobacteria: Synechocystis sp. PCC 6803, Synechococcus elongatus UTEX 2973 and Synechococcus sp. UTEX 3154. Highly-resolved 1D screening of nitrate, phosphate, carbonate, and salt content show that nitrate and/or phosphate can be limiting in standard cultivation media. Finally, we show that 2D screening results from our microfluidic setup translate well to a laboratory scale high-density cultivation setup. This study demonstrates that droplet-based microfluidics by micro segmented-flow are a powerful tool for high-throughput optimization of cyanobacterial cultivation.

microbiology↗

bioRxiv2022

FAK drives resistance to therapy in HPV-negative head and neck cancer in a p53-dependent manner.

Radiation and platinum-based chemotherapy form the backbone of therapy in HPV-negative head and neck squamous cell carcinoma (HNSCC). We have correlated focal adhesion kinase (FAK/PTK2) expression with radioresistance and worse outcome in these patients. However, the importance of FAK in driving radioresistance and its effects on chemoresistance in these patients remain unclear. We performed an in vivo shRNA screen using targetable libraries to address these questions and identified FAK as an excellent target for both radio- and chemosensitization. Because TP53 is mutated in over 80% of HPV-negative HNSCC, we hypothesized that mutant TP53 may facilitate FAK-mediated therapy resistance. FAK inhibitor increased sensitivity to radiation, increased DNA damage and repressed homologous recombination and non-homologous end joining repair in mutant, but not wild-type, TP53 HPV-negative HNSCC cell lines. Mutant TP53 cisplatin-resistant cell line had increased FAK phosphorylation compared to wild-type, and FAK inhibition partially reversed cisplatin resistance. To validate these findings, we utilized a HNSCC cohort to show that FAK copy number and gene expression were associated with worse disease-free survival in mutant TP53, but not wild-type TP53, HPV-negative HNSCC tumors. Thus, FAK may represent a targetable therapeutic sensitizer linked to a known genomic marker of resistance.

cancer biology↗

bioRxiv2022

Stem Cell Secretome Promotes Scarless Corneal Wound Healing and Rescues Corneal Sensory Nerves

Corneal scarring is a leading cause of blindness in the world. In this study, we explored the therapeutic potential of corneal stromal stem cell (CSSC)-derived secretome in a mechanical debridement mouse model of corneal scarring. CSSC secretome was able to promote scarless corneal wound healing. The mechanisms include 1) dampening inflammation with reduced CD45+, CD11b+/GR1+, and CD11b+/F4/80+ inflammatory cells in the wounded corneas; 2) reducing fibrotic extracellular matrix deposition such as collagen IV, collagen 3A1, SPARC, and -SMA; 3) rescuing sensory nerves. The proteomic analysis shows upregulated proteins related to wound healing and cell adhesion which boost scarless wound healing. It also shows upregulated neuroprotective proteins in CSSC secretome related to axon guidance, neurogenesis, neuron projection development, and neuron differentiation. Four unique complement inhibitory proteins CD59, vitronectin, SERPING1, and C1QBP found in CSSC secretome contribute to reducing a complement cascade mediating cell death and membrane attacking complex autoantibodies after corneal injury. This study provides novel insights into mechanisms of stem cell secretome induced scarless corneal wound healing and neuroprotection and identifies regenerative proteins in the CSSC secretome. Significance StatementIn this study, we report the therapeutic role of corneal stromal stem cell (CSSC) secretome for scarless corneal wound healing and corneal sensory nerve rescuing. We uncovered that CSSC secretome dampens inflammation, reduces fibrosis, induces sensory nerve regeneration, and rescues corneal cells by inhibiting the complement system in the wounded mouse corneas. This study provides pre-clinical evidence for the use of CSSC secretome as a biologic treatment for corneal scarring to prevent corneal blindness. We delineated a plethora of proteins in the CSSC secretome, which individually or in combination have the potential as future therapies for scarless corneal wound healing.

cell biology↗