Biology subjects

Chen, X.

Publications and source records attributed to Chen, X..

At least 541 records · Page 30Linked to original sources

bioRxiv2024

Cholecystokinin-expressing GABA neurons elicit long-term potentiation in the cortical inhibitory synapses and attenuate sound-shock associative memory

Neuronal interactions between inhibitory and excitatory neurons play a pivotal role in regulating the balance of excitation and inhibition in the central nervous system (CNS). Consequently, the efficacy of inhibitory/excitatory synapses profoundly affects neural network processing and overall neuronal functions. Here, we describe a novel form of long-term potentiation (LTP) induced at cortical inhibitory synapses and its behavioral consequences. We show that high-frequency laser stimulation (HFLS) of GABAergic neurons elicit inhibitory LTP (i-LTP) in pyramidal neurons of the auditory cortex (AC). The selective activation of cholecystokinin-expressing GABA (GABACCK) neurons is essential for the formation of HFLS-induced i-LTP, rather than the classical parvalbumin (PV) neurons and somatostatin (SST) neurons. Intriguingly, i-LTP can be evoked in the AC by adding the exogenous neuropeptide CCK when PV neurons and SST neurons are selectively activated in PV-Cre and SST-Cre mice, respectively. Additionally, we discovered that low-frequency laser stimulation (LFLS) of PV neurons paired with HFLS of GABACCK neurons potentiates the inhibitory effect of PV interneurons on pyramidal neurons, thereby generating heterosynaptic i-LTP in the AC. Notably, light activation of GABACCK neurons in CCK-Cre mice significantly attenuates sound-shock associative memory, while stimulation of PV neurons does not affect this memory in PV-Cre mice. In conclusion, these results demonstrate a critical mechanism regulating the excitation-inhibition balance and modulating learning and memory in cortical circuits. This mechanism might serve as a potential target for the treatment of neurological disorders, including epilepsy and Alzheimers disease.

neuroscience↗

bioRxiv2024

JunB-HBZ nuclear translocation by TGF-beta is a key driver in HTLV-1-mediated leukemogenesis

The HTLV-1 bZIP factor (HBZ) gene, which is the only viral gene conserved and consistently expressed in all adult T-cell leukemia-lymphoma (ATL) cases, is critical for ATL oncogenesis. Although HBZ protein is found in both the nucleus and the cytoplasm, the dynamics of HBZ protein localization and its contribution to oncogenesis have not been fully elucidated. In this study, we analyzed the subcellular expression pattern of HBZ in primary HTLV-1-infected T cells from asymptomatic carriers and leukemic cells of ATL patients using the Proximity Ligation Assay. Nuclear localization of HBZ protein was significantly higher in fresh ATL cells than in HTLV-1-infected cells from carriers. Importantly, translocation of HBZ protein from the cytoplasm to the nucleus after TGF-{beta} activation was observed in ATL patients, but not in HTLV-1 carriers. In ATL cells, the cellular transcription factors JunB and pSmad3 interact with HBZ and facilitate its nuclear translocation upon TGF-{beta} stimulation. JUNB knockdown inhibits cell proliferation in vitro and in vivo and promotes apoptosis in ATL cells but not in HTLV-1-infected non-leukemic cells, indicating that JunB has important roles in maintaining ATL cells. In conclusion, TGF-{beta}-induced nuclear translocation of HBZ-JunB complexes is associated with ATL oncogenesis.

microbiology↗

bioRxiv2024

Endogenous Huntingtin aggregates are a huge organized scaffold and mold for Golgi apparatus impaired by mutant Huntingtin protein

Abstract Huntingtin (HTT) is a naturally aggregating protein that causes Huntington's disease (HD) when its polyglutamine (polyQ) tract exceeds 38 repeats. Despite its importance, the biology of HTT aggregates remains poorly defined. Here, using high resolution imaging of cells derived from HD families, we redefine polyQ assemblies, traditionally regarded as pathogenic aggregates, as dynamic and structurally organized intracellular compartments resembling knitted-fabric patches. These assemblies closely associate with and encircle the Golgi apparatus, integrating Golgi ribbons and stacks to form a previously unrecognized polyQ assembly-Golgi complex. Mechanistically, fragmentation of polyQ assemblies is dynamically coupled with mitotic Golgi fragmentation, whereas inhibition of ADP-ribosylation factor (ARF) function by Brefeldin A disrupts and fragments the complex, revealing an intimate structural and functional coupling between polyQ assemblies and Golgi architecture. The presence of mutant HTT (mHTT) destabilizes these assemblies and complexes, altering their response to nutrient deprivation and autophagy enhancers but not to antisense oligonucleotide (ASO) therapy. Functionally, polyQ assemblies in HD cells compromise the scaffolding capacity of the Golgi apparatus, clathrin-coated vesicles, and ARF1, impair Golgi glycosylation, and promote aberrant neuronal firing activity. Collectively, these findings establish polyQ assemblies as dynamic structural regulators of Golgi organization and function and demonstrate that mHTT disrupts the homeostatic dynamics of the polyQ assembly-Golgi complex, leading to Golgipathy.

pathology↗

bioRxiv2024

The FIP 1.0 Data Set: Highly Resolved Annotated Image Time Series of 4,000 Wheat Plots Grown in Six Years

BackgroundUnderstanding genotype-environment interactions of plants is crucial for crop improvement, yet limited by the scarcity of quality phenotyping data. This data note presents the Field Phenotyping Platform 1.0 data set, a comprehensive resource for winter wheat research that combines imaging, trait, environmental, and genetic data. FindingsWe provide time series data for more than 4,000 wheat plots, including aligned high-resolution image sequences totaling more than 153,000 aligned images across six years. Measurement data for eight key wheat traits is included, namely canopy cover values, plant heights, wheat head counts, senescence ratings, heading date, final plant height, grain yield, and protein content. Genetic marker information and environmental data complement the time series. Data quality is demonstrated through heritability analyses and genomic prediction models, achieving accuracies aligned with previous research. ConclusionsThis extensive data set offers opportunities for advancing crop modeling and phenotyping techniques, enabling researchers to develop novel approaches for understanding genotype-environment interactions, analyzing growth dynamics, and predicting crop performance. By making this resource publicly available, we aim to accelerate research in climate-adaptive agriculture and foster collaboration between plant science and machine learning communities.

plant biology↗

bioRxiv2024

Trans-generational adaptation to maternal climate through hormone transport in plants

Whether organisms can inherit parental adaptations to the environment is a major question in evolutionary biology. Plant development is highly plastic and dependent on the seasonal cues which are used to control growth and reproduction. Seed dormancy and germination are key traits which respond strongly to temperature during seed development and here we show that progeny adaptation to seasonal climate is inherited from the mother plant. Loss of maternal LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) causes an inability of progeny seeds to sense temperature and this is linked mechanistically to reduced ABA levels in seeds and activation of the primary nitrate response. At the single cell level, small changes in temperature activate nitrate signalling specifically in the mother, and ABA biosensor imaging reveals temperature-dependent fluxes of ABA into seeds necessary for dormancy induction. Thus, we reveal that progeny seeds inherit the climate adaptation of mother plants via active hormone transport during seed set.

plant biology↗

bioRxiv2024

ADT-1004: A First-in-Class, Orally Bioavailable Selective pan-RAS Inhibitor for Pancreatic Ductal Adenocarcinoma

Here, we evaluated in vivo antitumor activity, target engagement, selectivity, and tumor specificity of ADT-1004, an orally bioavailable prodrug of ADT-007 having highly potent and selective pan-RAS inhibitory activity. ADT-1004 strongly blocked tumor growth and RAS activation in mouse PDAC models without discernable toxicity. As evidence of target engagement and tumor specificity, ADT-1004 inhibited activated RAS and ERK phosphorylation in PDAC tumors at dosages approximately 10-fold below the maximum tolerated dose and without discernable toxicity. ADT-1004 inhibited ERK phosphorylation in PDAC tumors. In addition, ADT-1004 blocked tumor growth and ERK phosphorylation in PDX PDAC models with KRASG12D, KRASG12V, KRASG12C, or KRASG13Q mutations. ADT-1004 treatment increased CD4+ and CD8+ T cells in the TME consistent with exhaustion and increased MHCII+ M1 macrophage and dendritic cells. ADT-1004 demonstrated superior efficacy over sotorasib and adagrasib in tumor models involving human PDAC cells resistant to these KRASG12C inhibitors. As evidence of selectivity for tumors from PDAC cells with mutant KRAS, ADT-1004 did not impact the growth of tumors from RASWT PDAC cells. Displaying broad antitumor activity in multiple mouse models of PDAC, along with target engagement and selectivity at dosages that were well tolerated, ADT-1004 warrants further development. SignificanceADT-1004 displayed robust antitumor activity in aggressive and clinically relevant PDAC models with unique tumor specificity to block RAS activation and MAPK signaling in RAS mutant cells. As a pan-RAS inhibitor, ADT-1004 has broad activity and potential efficacy advantages over allele-specific KRAS inhibitors by averting resistance. These findings support clinical trials of ADT-1004 for KRAS mutant PDAC.

cancer biology↗

bioRxiv2024

Quantitative proteomic mass spectrometry of protein kinases to determine dynamic heterogeneity of the human kinome

The kinome is a dynamic system of kinases regulating signaling networks in cells and dysfunction of protein kinases contributes to many diseases. Regulation of the protein expression of kinases alters cellular responses to environmental changes and perturbations. We configured a library of 672 proteotypic peptides to quantify >300 kinases in a single LC-MS experiment using ten micrograms protein from human tissues including biopsies. This enables absolute quantitation of kinase protein abundance at attomole-femtomole expression levels, requiring no kinase enrichment and less than ten micrograms of starting protein from flash-frozen and formalin fixed paraffin embedded tissues. Breast cancer biopsies, organoids, and cell lines were analyzed using the SureQuant method, demonstrating the heterogeneity of kinase protein expression across and within breast cancer clinical subtypes. Kinome quantitation was coupled with nanoscale phosphoproteomics, providing a feasible method for novel clinical diagnosis and understanding of patient kinome responses to treatment.

biochemistry↗

bioRxiv2024

Brainstem neurons coordinate the bladder and urethra sphincter for urination

Urination, a vital and conserved process of emptying urine from the urinary bladder in mammals, requires precise coordination between the bladder and external urethral sphincter (EUS) that is tightly controlled by a complex neural network. However, the specific subpopulation of neurons that accounts for such coordination remains unidentified, limiting the development of target-specific therapies for certain urination disorders, e.g., detrusor-sphincter dyssynergia. Here, we find that cells expressing estrogen receptor 1 (ESR1+) in the pontine micturition center (PMC) initiate voiding when activated and suspend ongoing voiding when suppressed, each at 100% reliability. Transection of the pelvic nerve does not impair PMCESR1+ neurons control of the EUS via the pudendal nerve, whereas transection of the pudendal nerve does not impair their control of the bladder via the pelvic nerve. Anatomically, PMCESR1+ neurons consist of three distinct spinal-projection-based subpopulations: one targeting the sacral parasympathetic nucleus (SPN), one innervating the dorsal gray commissure (DGC), and a third that projects to both regions, thereby enforcing the coordination of bladder contraction and sphincter relaxation in a rigid temporal sequence. Thus, we identify a cell type in the brainstem that controls the bladder-urethra coordination for urination.

neuroscience↗

bioRxiv2024

Cryo-EM structural insights into Vγ9Vδ2 TCR activation via multiple butyrophilins

Human V{gamma}9V{delta}2 T cells detect cancerous and pathogen-infected cells through an "inside-out" mechanism wherein intracellular domains of butyrophilin (BTN) proteins recognize phosphoantigens (pAgs) to prime BTN ectodomains to engage with the T cell receptor (TCR) to activate V{gamma}9V{delta}2 T cells. Here, we present cryo-electron microscopy (cryo-EM) structures, including the full-length BTN3A1-BTN3A2-BTN2A1 complex stabilized by the pAg HMBPP and an HMBPP-primed BTN multimer complex engaged with the V{gamma}9V{delta}2 TCR. The HMBPP-primed BTN3A1-BTN3A2-BTN2A1 complex confirms that this pAg bridges the intracellular B30.2 domains of BTN3A1 and BTN2A1, while also revealing an association of the ectodomains of BTN3A2 and BTN2A1. Upon TCR engagement, the TCR undergoes a substantial conformational change and BTN3A2-BTN2A1 ectodomain interaction dissociates, allowing BTN2A1 to bind to the lateral surface of the V{gamma}9 chain, while BTN3A2 binds to the apical surface of the V{delta}2 chain. Beyond demonstrating that BTN3A2 as a bona fide TCR ligand, this dissociation/binding sequence suggests a "pliers-like gripping" mechanism for TCR activation. We also obtained cryo-EM structures of BTN proteins in complex with functional antibodies, further elucidating the overall V{gamma}9V{delta}2 T cell activation process. Thus, our structural insights into how BTN proteins sense antigens and drive TCR activation lay the groundwork for developing targeted {gamma}{delta} T cell immunotherapies.

immunology↗

bioRxiv2024

CREATE: cell-type-specific cis-regulatory elements identification via discrete embedding

Identifying cis-regulatory elements (CREs) within non-coding genomic regions--such as enhancers, silencers, promoters, and insulators--is pivotal for elucidating the intricate gene regulatory mechanisms underlying complex biological traits. The current prevalent sequence-based methods often focus on singular CRE types, limiting insights into cell-type-specific biological implications. Here, we introduce CREATE, a multimodal deep learning model based on the Vector Quantized Variational AutoEncoder framework, designed to extract discrete CRE embeddings and classify multiple CRE classes using genomic sequences, chromatin accessibility, and chromatin interaction data. CREATE excels in accurate CRE identification and exhibits strong effectiveness and robustness. We showcase CREATEs capability in generating comprehensive CRE-specific feature spectrum, offering quantitative and interpretable insights into CRE specificity. By enabling large-scale prediction of CREs in specific cell types, CREATE facilitates the recognition of disease- or phenotype-related biological variabilities of CREs, thereby expanding our understanding of gene regulation landscapes.

bioinformatics↗

bioRxiv2024

Posterior Parietal Cortex Regulates Intrinsic Neural Timescales and Attentional Processing in Frontal Eye Field

Intrinsic neural timescales quantify how long spontaneous neuronal activity patterns persist, reflecting dynamics of endogenous fluctuations. We measured intrinsic timescales of frontal eye field (FEF) neurons and examined their changes during posterior parietal cortex (PPC) inactivation. We observed two distinct classes of FEF neurons based on their intrinsic timescales: short-timescale neurons ([~]25 ms) or long-timescale neurons ([~]100 ms). Short-timescale neurons showed stronger transient visual responses, suggesting their role in rapid visual processing, whereas long-timescale neurons exhibited pronounced sustained attentional modulation, suggesting their role in maintaining stimulus-driven attention. During PPC inactivation, intrinsic timescales increased in both neuron types, with a significantly larger effect in short-timescale neurons. In addition, PPC inactivation reduced attentional modulation, particularly in long-timescale neurons. Our findings provide the first causal evidence linking intrinsic local neural timescales to long-range inter-area communications. These findings also suggest the presence of at least two distinct network motifs that support different neuronal dynamics and functional computations within the FEF.

neuroscience↗

bioRxiv2024

CPK3-mediated cytosolic-nuclear translocation of bHLH107 recruits HY5 to regulate the Cu2+-triggered upregulation of ACS8

Copper serves as a micronutrient for plant growth and development and has been a key component of copper-based antimicrobial compounds (CBACs) for protection against plant diseases for more than 130 years. We previously revealed that nanomolar- to-micromolar concentrations of Cu2+ elicit plant immune responses by activating the expression of the ethylene synthesis rate-limiting enzyme ACS8, which is dependent on the promoter copper response element (CuRE) cis-element. Here, we genetically confirmed that Cu2+-induced resistance to Pseudomonas syringae pv. tomato (Pst) DC3000 is dependent on the CuRE in ACS8. Upon screening for CuRE-binding transcription factors, bHLH107, which is required for Cu2+-triggered activation of ACS8 expression and resistance to Pst DC3000, was identified via DNA-pull-down and mass spectrometry (MS) assays. Calcium-dependent protein kinase 3 (CPK3) interacts with and phosphorylates bHLH107 at Ser62 and Ser72 to mediate bHLH07 translocation from the cytoplasm into the nucleus, where it interacts with Arabidopsis ELONGATED HYPOCOTYL5 (HY5). HY5 directly binds to the G-box and acts as a coactivator to promote bHLH107 binding to the CuRE cis-element and to increase transcription of ACS8 upon Cu2+ treatment. Overall, we revealed a CPK3-bHLH107-HY5 module that regulates the Cu2+-responsive regulatory network upstream of ACS8 that is involved in the cytosolic-nuclear translocation of bHLH107.

plant biology↗

bioRxiv2024

Structural Characterization of mRNA Lipid Nanoparticles in the Presence of Intrinsic Drug-free Lipid Nanoparticles

Lipid nanoparticles (LNPs) have emerged as a versatile platform for mRNA delivery across a range of applications, including disease prevention, cancer immunotherapy, and gene editing. Structural models of mRNA-containing lipid nanoparticles (mRNA-LNPs) have also been proposed based on characterization of samples by using various advanced techniques. Among these, small angle neutron scattering (SANS) has proven essential for elucidating the lipid distribution within mRNA-LNPs, a factor crucial to both their preparation and efficacy. However, recent findings suggest that the mRNA-LNP samples prepared via commercial microfluidic techniques may contain a substantial fraction of drug-free LNPs, casting doubt on the validity of earlier structural models. In this study, we employed contrast variation SANS to characterize both drug-free LNPs and our mRNA-LNP sample, and quantified the proportion of drug-free LNPs present to be [~]30% in our mRNA-LNP sample using nano flow cytometry. By removing the contributions of drug-free LNPs from the SANS data of our mRNA-LNP sample, we were able to precisely characterize the structure of mRNA-LNPs. Consequently, we proposed structural models for both drug-free LNPs and mRNA-LNPs. Notably, our analysis revealed similar lipid distributions and shell thicknesses between the two particle types, while the solvent content in mRNA-LNPs was significantly higher, leading to a larger core size. This work not only offers a method for accurately characterizing the structure of mRNA-LNPs, but also establishes criteria for selecting appropriate analytical techniques based on the structural parameters of interest. Therefore, our findings hold significant implications for the mechanistic understanding and quality control of mRNA-based vaccines. SignificancePrecise structural determination of mRNA-containing lipid nanoparticles (mRNA-LNPs) is vital for mechanistic insights into their preparation, delivery, immunogenicity, and storage, which are critical to the development of mRNA-based vaccines. However, most previous studies overlooked the substantial presence of drug-free LNPs within these samples. Here, we identified that approximately 30% of the nanoparticles in our mRNA-LNP sample were drug-free. By integrating contrast variation small angle neutron scattering (SANS) data from both drug-free LNPs and mRNA-LNPs, we developed structural models for both particle types, and provided a guidance for characterization technique selection based on concerned structural features. Beyond mechanistic insight on structure, our approach offers a robust method for quality assessment and process monitoring in mRNA-based vaccine production.

biophysics↗

bioRxiv2024

Identification of Human Pathways Acting on Nuclear Non-Coding RNAs Using the Mirror Forward Genetic Approach

Despite critical roles in diseases, human pathways acting on strictly nuclear non-coding RNAs have been refractory to forward genetics. To enable their forward genetic discovery, we developed a single-cell approach that "Mirrors" activities of nuclear pathways with cytoplasmic fluorescence. Application of Mirror to two nuclear pathways targeting MALAT1s 3' end, the pathway of its maturation and the other, the degradation pathway blocked by the triple-helical Element for Nuclear Expression (ENE), identified nearly all components of three complexes: Ribonuclease P and the RNA Exosome, including nuclear DIS3, EXOSC10, and C1D, as well as the Nuclear Exosome Targeting (NEXT) complex. Additionally, Mirror identified DEAD-box helicase DDX59 associated with the genetic disorder Oral-Facial-Digital syndrome (OFD), yet lacking known substrates or roles in nuclear RNA degradation. Knockout of DDX59 exhibits stabilization of the full-length MALAT1 with a stability-compromised ENE and increases levels of 3'-extended forms of small nuclear RNAs. It also exhibits extensive retention of minor introns, including in OFD-associated genes, suggesting a mechanism for DDX59 association with OFD. Mirror efficiently identifies pathways acting on strictly nuclear non-coding RNAs, including essential and indirectly-acting components, and, as a result, uncovers unexpected links to human disease.

genetics↗

bioRxiv2024

GPR30 in spinal cholecystokinin-positive neurons modulates neuropathic pain via mediating descending facilitation

Neuropathic pain, a major health problem affecting 7-10% of the global population, lacks effective treatment due to its elusive mechanisms. Cholecystokinin-positive (CCK+) neurons in the spinal dorsal horn (SDH) are critical for neuropathic pain, yet the underlying molecular mechanisms remain unclear. Here, we show that the membrane estrogen receptor G-protein coupled estrogen receptor (GPER/GPR30) in spinal neurons was significantly upregulated in chronic constriction injury (CCI) mice and that inhibition of GPR30 in CCK+ neurons reversed CCI-induced neuropathic pain. Furthermore, GPR30 in spinal CCK+ neurons was essential for the enhancement of AMPA-mediated excitatory synaptic transmission in CCI mice. Moreover, GPR30 was expressed in spinal CCK+ neurons that received direct projection from the primary sensory cortex (S1-SDH). Chemogenetic inhibition of S1-SDH post-synaptic neurons alleviated CCI-induced neuropathic pain. Conversely, chemogenetic activation of these neurons mimicked neuropathic pain symptoms, which were attenuated by spinal inhibition of GPR30. Finally, we confirmed that GPR30 in S1-SDH post-synaptic neurons was required for CCI-induced neuropathic pain. Taken together, our findings suggest that GPR30 in spinal CCK+ neurons and S1-SDH postsynaptic neurons is pivotal for neuropathic pain, thereby representing a promising therapeutic target for neuropathic pain.

neuroscience↗

bioRxiv2024

Early Prediction of Ischaemic Stroke Outcomes: A Novel Computational Approach

Malignant stroke can lead to a death rate as high as 80%. Although early interventions can improve patient outcomes, they also lead to side effects. Therefore, the early prediction of stroke outcomes is crucial for clinical strategies. Imaging markers such as brain swelling volume and midline shift have been critical predictors in various stroke scoring systems. However, these markers can only become visible on brain images days after stroke onset, which delays clinical decisions. A primary challenge in predicting these markers is that brain swelling is a biomechanical process that relies on anatomical features, such as lesion size and location. To tackle this problem, we propose a novel computational pipeline to predict brain swelling after stroke. We first provide a mathematical model of the brain by using a five-compartment poroelastic theory. It allows us to generate high-quality stroke cases with varied 3D brain and lesion anatomy, which are then used to train and validate a deep neural network (DNN). Our in silico experimentation with 3,000 cases shows that anatomical features of stroke brains are well-learned by the DNN, with minimal errors in brain swelling prediction found in the hold-out testing cases. In addition, we used the DNN to process clinical imaging data of 60 stroke patients. The results show that the markers generated from the DNN can predict 3-month stroke outcomes with an AUC of around 0.7. It indicates that the proposed computational pipeline can potentially advance the time point for clinical decisions. Significance StatementStroke is the second leading cause of death in the world, and malignant stroke can lead to a death rate of 80%. Early interventions can improve patient outcomes but can also cause side effects. Therefore, it is crucial to predict stroke outcomes at an early stage. Radiological markers such as brain swelling volume and midline shift have been used in various stroke scoring systems. However, these markers can only become visible after days to stroke onset, which delays clinical decisions. To tackle this issue, we propose a novel computational pipeline to predict brain swelling after stroke onset. The proposed pipeline is found to predict brain swelling accurately and can potentially assist early clinical decision-making.

bioengineering↗

bioRxiv2024

Innate immune epigenomic landscape following controlled human influenza virus infection

Viral infections can induce changes in innate immunity that persist after virus clearance. Here, we used blood samples from a human influenza H3N2 challenge study to perform comprehensive multi-omic analyses. We detected remodeling of immune programs in innate immune cells after resolution of the infection that was proportional in magnitude to the level of prior viral load. We found changes associated with suppressed inflammation including decreased cytokine and AP-1 gene expression as well as decreased accessibility at AP-1 targets and interleukin-related gene promoter regions. We also found decreased histone deacetylase gene expression, increased MAP kinase gene expression, and increased accessibility at interferon-related gene promoter regions. Genes involved in inflammation and epigenetic-remodeling showed modulation of gene-chromatin site regulatory circuit activity. These results reveal a coordinated rewiring of the epigenetic landscape in innate immune cells induced by mild influenza virus infection.

immunology↗

bioRxiv2024

Evolutionary fingerprint in rodent PD1 confers weakened activity and enhanced tumor immunity compared to human PD1

Mechanistic understanding of the immune checkpoint receptor PD1 is largely based on mouse models, but human and mouse PD1 orthologs exhibit only 59.6% identity in amino acid sequences. Here we show that human PD1 is more inhibitory than mouse PD1 due to stronger interactions with the ligands PDL1 and PDL2 and with the effector phosphatase Shp2. A novel motif highly conserved among PD1 orthologs in vertebrates except in rodents is primarily responsible for the differential Shp2 recruitment. Evolutionary analysis suggested that rodent PD1 orthologs uniquely underwent functional relaxation, particularly during the K-Pg boundary. Humanization of the PD1 intracellular domain disrupted the anti-tumor activity of mouse T cells while increasing the magnitude of anti-PD1 response. Together, our study uncovers species-specific features of the PD1 pathway, with implications to PD1 evolution and differential anti-PD(L)1 responses in mouse models and human patients.

immunology↗