Biology subjects

Shen, J.

Publications and source records attributed to Shen, J..

At least 145 records · Page 8Linked to original sources

bioRxiv2023

Cas12a/Cpf1 knock-in mice enable efficient multiplexed immune cell engineering

Cas9 transgenic animals have drastically accelerated the discovery of novel immune modulators. But due to its inability to process its own CRISPR RNAs (crRNAs), simultaneous multiplexed gene perturbations using Cas9 remains limited, especially by pseudoviral vectors. Cas12a/Cpf1, however, can process concatenated crRNA arrays for this purpose. Here, we created conditional and constitutive LbCas12a knock-in transgenic mice. With these mice, we demonstrated efficient multiplexed gene editing and surface protein knockdown within individual primary immune cells. We showed genome editing across multiple types of primary immune cells including CD4 and CD8 T cells, B cells, and bone-marrow derived dendritic cells. These transgenic animals, along with the accompanying viral vectors, together provide a versatile toolkit for a broad range of ex vivo and in vivo gene editing applications, including fundamental immunological discovery and immune gene engineering.

genetics↗

bioRxiv2023

Characterization of a mouse model of ICF syndrome reveals enhanced CD19 activation in inducing hypogammaglobulinemia

Immunodeficiency, centromeric instability and facial anomalies (ICF) syndrome is a rare autosomal recessive disorder characterized by DNA hypomethylation and antibody deficiency. It is caused by mutations in DNMT3B, ZBTB24, CDCA7 or HELLS. While progress has been made in elucidating the roles of these genes in regulating DNA methylation, little is known about the pathogenesis of the life-threatening hypogammaglobulinemia phenotype. Here we show that mice deficient for Zbtb24 in the hematopoietic lineage recapitulate major clinical features of patients with ICF syndrome. Specifically, Vav-Cre-mediated ablation of Zbtb24 does not affect lymphocyte development but results in reduced plasma cells and low levels of IgM, IgG1 and IgA. Zbtb24-deficient mice are hyper- and hypo-responsive to T-dependent and Tindependent type 2 antigens, respectively, and marginal zone B cell activation is impaired. B cells from Zbtb24-deficient mice display elevated CD19 phosphorylation. Heterozygous disruption of Cd19 can revert the hypogammaglobulinemia phenotype in these mice. Mechanistically, Il5ra (interleukin-5 receptor subunit alpha) is derepressed in Zbtb24-deficient B cells, and elevated IL-5 signaling enhances CD19 phosphorylation. Our results reveal a novel link between IL-5 signaling and CD19 activation and suggest that abnormal CD19 activity contributes to immunodeficiency in ICF syndrome. SIGNIFICANCE STATEMENTICF syndrome is a rare immunodeficiency disorder first reported in the 1970s. The lack of appropriate animal models has hindered the investigation of the pathogenesis of antibody deficiency, the major cause of death in ICF syndrome. Here we show that, in mice, disruption of Zbtb24, one of the ICF-related genes, in the hematopoietic lineage results in low levels of immunoglobulins. Characterization of these mice reveals abnormal B cell activation due to elevated CD19 phosphorylation. Mechanistically, Il5ra (interleukin-5 receptor subunit alpha) is derepressed in Zbtb24-deficient B cells, and increased IL-5 signaling enhances CD19 phosphorylation.

immunology↗

bioRxiv2023

Structure-Kinetics Relationships of Opioids from Metadynamics and Machine Learning

The nations opioid overdose deaths reached an all-time high in 2021. The majority of deaths are due to synthetic opioids represented by fentanyl. Naloxone, which is a FDA-approved reversal agent, antagonizes opioids through competitive binding at the -opioid receptor (mOR). Thus, knowledge of opioids residence time is important for assessing the effectiveness of naloxone. Here we estimated the residence times of 15 fentanyl and 4 morphine analogs using metadynamics, and compared them with the most recent measurement of the opioid kinetic, dissociation, and naloxone inhibitory constants (Mann, Li et al, Clin. Pharmacol. Therapeut. 2022). Importantly, the microscopic simulations offered a glimpse at the common binding mechanism and molecular determinants of dissociation kinetics for fentanyl analogs. The insights inspired us to develop a machine learning (ML) approach to analyze the kinetic impact of fentanyls substituents based on the interactions with mOR residues. This proof-of-concept approach is general; for example, it may be used to tune ligand residence times in computeraided drug discovery. Graphical TOC Entry O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/531338v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@15e4093org.highwire.dtl.DTLVardef@e17398org.highwire.dtl.DTLVardef@16c2aaaorg.highwire.dtl.DTLVardef@6527a2_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2023

UBE3A and transsynaptic complex NRXN1-CBLN1-GluD1 in a hypothalamic VMHvl-arcuate feedback circuit regulates aggression

The circuit origins of aggression in autism spectrum disorder remain undefined. Here we report Tac1-expressing glutamatergic neurons in ventrolateral division of ventromedial hypothalamus (VMHvl) drive intermale aggression. Aggression is increased due to increases of Ube3a gene dosage in the VMHvl neurons when modeling autism due to maternal 15q11-13 triplication. Targeted deletion of increased Ube3a copies in VMHvl reverses the elevated aggression adult mice. VMHvl neurons form excitatory synapses onto hypothalamic arcuate nucleus AgRP/NPY neurons through a NRXN1-CBLN1-GluD1 transsynaptic complex and UBE3A impairs this synapse by decreasing Cbln1 gene expression. Exciting AgRP/NPY arcuate neurons leads to feedback inhibition of VMHvl neurons and inhibits aggression. Asymptomatic increases of UBE3A synergize with a heterozygous deficiency of presynaptic Nrxn1 or postsynaptic Grid1 (both ASD genes) to increase aggression. Targeted deletions of Grid1 in arcuate AgRP neurons impairs the VMHvl to AgRP/NPY neuron excitatory synapses while increasing aggression. Chemogenetic/optogenetic activation of arcuate AgRP/NPY neurons inhibits VMHvl neurons and represses aggression. These data reveal that multiple autism genes converge to regulate the VMHvl-arcuate AgRP/NPY glutamatergic synapse. The hypothalamic circuitry implicated by these data suggest impaired excitation of AgRP/NPY feedback inhibitory neurons may explain the increased aggression behavior found in genetic forms of autism. One Sentence SummaryA feedback circuit in the hypothalamus that inhibits aggression is impaired by converging autism genetic defects.

neuroscience↗

bioRxiv2023

Glutamine metabolism inhibition has dual immunomodulatory and antibacterial activities against Mycobacterium tuberculosis

As one of the most successful human pathogens, Mycobacterium tuberculosis (Mtb) has evolved a diverse array of determinants to subvert host immunity and alter host metabolic patterns. However, the mechanisms of pathogen interference with host metabolism remain poorly understood. Here we show that a novel glutamine metabolism antagonist, JHU083, inhibits Mtb proliferation in vitro and in vivo. JHU083-treated mice exhibit weight gain, improved survival, a 2.5 log lower lung bacillary burden at 35 days post-infection, and reduced lung pathology. JHU083 treatment also initiates earlier T-cell recruitment, increased proinflammatory myeloid cell infiltration, and a reduced frequency of immunosuppressive myeloid cells when compared to uninfected and rifampin-treated controls. Metabolomics analysis of lungs from JHU083-treated Mtb-infected mice revealed reduced glutamine levels, citrulline accumulation suggesting elevated NOS activity, and lowered levels of quinolinic acid which is derived from the immunosuppressive metabolite kynurenine. When tested in an immunocompromised mouse model of Mtb infection, JHU083 lost its therapeutic efficacy suggesting the drugs host-directed effects are likely to be predominant. Collectively, these data reveal that JHU083-mediated glutamine metabolism inhibition results in dual antibacterial and host-directed activity against tuberculosis.

microbiology↗

bioRxiv2023

RNA-to-image multi-cancer synthesis using cascaded diffusion models

Data scarcity presents a significant obstacle in the field of biomedicine, where acquiring diverse and sufficient datasets can be costly and challenging. Synthetic data generation offers a potential solution to this problem by expanding dataset sizes, thereby enabling the training of more robust and generalizable machine learning models. Although previous studies have explored synthetic data generation for cancer diagnosis, they have predominantly focused on single modality settings, such as whole-slide image tiles or RNA-Seq data. To bridge this gap, we propose a novel approach, RNA-Cascaded-Diffusion-Model or RNA-CDM, for performing RNA-to-image synthesis in a multi-cancer context, drawing inspiration from successful text-to-image synthesis models used in natural images. In our approach, we employ a variational auto-encoder to reduce the dimensionality of a patients gene expression profile, effectively distinguishing between different types of cancer. Subsequently, we employ a cascaded diffusion model to synthesize realistic whole-slide image tiles using the latent representation derived from the patients RNA-Seq data. Our results demonstrate that the generated tiles accurately preserve the distribution of cell types observed in real-world data, with state-of-the-art cell identification models successfully detecting important cell types in the synthetic samples. Furthermore, we illustrate that the synthetic tiles maintain the cell fraction observed in bulk RNA-Seq data and that modifications in gene expression affect the composition of cell types in the synthetic tiles. Next, we utilize the synthetic data generated by RNA-CDM to pretrain machine learning models and observe improved performance compared to training from scratch. Our study emphasizes the potential usefulness of synthetic data in developing machine learning models in sarce-data settings, while also highlighting the possibility of imputing missing data modalities by leveraging the available information. In conclusion, our proposed RNA-CDM approach for synthetic data generation in biomedicine, particularly in the context of cancer diagnosis, offers a novel and promising solution to address data scarcity. By generating synthetic data that aligns with real-world distributions and leveraging it to pretrain machine learning models, we contribute to the development of robust clinical decision support systems and potential advancements in precision medicine.

bioinformatics↗

bioRxiv2022

Retrieving the near-complete genome of a threatened bird from wild frozen samples

Conservation genomics often relies on non-invasive methods to obtain DNA fragments which limit the power of multi-omic analyses for threatened species. Collecting samples from frozen dead animals in the wild provides an alternative approach to obtaining high-quality nucleic acids. Here, we report multi-omic analyses based on a well-preserved great bustard individual (Otis tarda, Otidiformes) of a recent death found in the mountainous region in Gansu, China. We generated a near-complete genome assembly (OTswu) having only 18 gaps scattering in 8 out of the 40 assembled chromosomes. Unlikely most other bird genome assemblies, OTswu contains complete chromosome models (2n = 80). We demonstrated that the great bustard genome likely retained the ancestral avian karyotype. We also characterized the DNA methylation landscapes of OTswu which are strongly correlated with GC content and gene expression. Our phylogenomic analysis suggested Otidiformes and Musophagiformes were sister groups that diverged from each other 46.3 million years ago. The genetic diversity of great bustard was found the lowest among the four available Otidiformes genomes, possibly due to population declines during past glacial periods. As one of the heaviest migratory birds, great bustard possesses several expanded gene families related to cardiac contraction, actin contraction, calcium ion signaling transduction, as well as positively selected genes enriching for metabolism. Finally, we identified an extremely young evolutionary stratum on the sex chromosome, a rare case among Neoaves. Together, our study combining long-read sequencing and RNA-seq technology provides a working strategy for conducting multi-omic analyses for threatened species by retrieving high-quality nucleic acids from dead animals frozen in the wild.

genomics↗

bioRxiv2022

Fine-Mapping and Credible Set Construction using a Multipopulation Joint Analysis of Marginal Summary Statistics from Genome-wide Association Studies

Recent advancement in Genome-wide Association Studies (GWAS) comes from not only increasingly larger sample sizes but also the shifted focus towards underrepresented populations. Multi-population GWAS may increase power to detect novel risk variants and improve fine-mapping resolution by leveraging evidence from diverse populations and accounting for the difference in linkage disequilibrium (LD) across ethnic groups. Here, we expand upon our previous approach for single-population fine-mapping through Joint Analysis of Marginal SNP Effects (JAM) to a multi-population analysis (mJAM). Under the assumption that true causal variants are common across studies, we implement a novel version of JAM that conditions on multiple SNPs while explicitly incorporating the different LD structures across populations. The mJAM framework can be used to first select index variants using the mJAM likelihood with any feature selection approach. In addition, we present a novel approach leveraging the ideas of mediation to construct credible sets for these index variants. Construction of such credible sets can be performed given any existing index variants. We illustrate the implementation of the mJAM likelihood through two implementations: mJAM-SuSiE (a Bayesian approach) and mJAM-Forward selection. Through simulation studies based on realistic effect sizes and levels of LD, we demonstrated that mJAM performs better than other existing multi-ethnic methods for constructing concise credible sets that include the underlying causal variants. In real data examples taken from the most recent multi-population prostate cancer GWAS, we showed several practical advantages of mJAM over other existing methods.

genetics↗

bioRxiv2022

Synthetic whole-slide image tile generation with gene expression profiles infused deep generative models

The acquisition of multi-modal biological data for the same sample, such as RNA sequencing and whole slide imaging (WSI), has increased in recent years, enabling studying human biology from multiple angles. However, despite these emerging multi-modal efforts, for the majority of studies only one modality is typically available, mostly due to financial or logistical constraints. Given these difficulties, multi-modal data imputation and multi-modal synthetic data generation are appealing as a solution for the multi-modal data scarcity problem. Currently, most studies focus on generating a single modality (e.g. WSI), without leveraging the information provided by additional data modalities (e.g. gene expression profiles). In this work, we propose an approach to generate WSI tiles by using deep generative models infused with matched gene expression profiles. First, we train a variational autoencoder (VAE) that learns a latent, lower dimensional representation of multi-tissue gene expression profiles. Then, we use this representation to infuse generative adversarial networks (GAN) that generate lung and brain cortex tissue tiles, resulting in a new model that we call RNA-GAN. Tiles generated by RNA-GAN were preferred by expert pathologists in comparison to tiles generated using traditional GANs and in addition, RNA-GAN needs fewer training epochs to generate high-quality tiles. Finally, RNA-GAN was able to generalize to gene expression profiles outside of the training set, showing imputation capabilities. A web-based quiz is available for users to play a game distinguishing real and synthetic tiles: https://rna-gan.stanford.edu/ and the code for RNA-GAN is available here: https://github.com/gevaertlab/RNA-GAN.

bioinformatics↗

bioRxiv2022

Mechanism of pH sensing in the human voltage-gated proton channel hHv1

The molecular mechanisms governing the human voltage-gated proton channel hHv1 remain elusive. Here we used membrane-enabled hybrid-solvent continuous constant pH molecular dynamics (CpHMD) simulations with pH replica exchange to further evaluate the recently obtained structural models of hHv1 in hyperpolarized (closed channel) and depolarized (open channel) states (Geragotelis, Tobias et al., Proc. Natl. Acad. Sci. USA 2020) and explore potential pH-sensing residues. The CpHMD titration at a set of symmetric pH conditions revealed three residues that can gain or lose protons upon channel depolarization. Among them residue H168 at the intracellular end of the S3 helix switches from the deprotonated to the protonated state and its protonation is correlated with the increased tilting of the S3 helix during the transition from the hyper-to the depolarized state. Thus, the simulation data suggest H168 as an interior pH sensor, in support of a recent finding based on electrophysiological experiments of Hv1 mutants (Cherny, DeCoursey et al., J. Gen. Physiol. 2018). Our work represents an important step towards deciphering the pH-dependent gating mechanism of hHv1. SIGNIFICANCEThe human voltage-gated proton channel hHv1 is comprised of a proton-selective voltage sensing domain and responsible for cellular pH homeostasis. Despite intense experimental and theoretical investigations, its pH-dependent gating mechanism is not understood. Our simulation data offer strong evidence supporting the role of H168 as a pHi sensor (Cherny, DeCoursey et al., J. Gen. Physiol. 2018). Deciphering the interior pH sensor moves us a step closer to elucidating the structure-function relationship of hHv1.

biophysics↗

bioRxiv2022

Rapid and Signal Crowdedness-Robust In-Situ Sequencing through Hybrid Block Coding

Spatial transcriptomics technology has revolutionized our understanding of cell types and tissue organization, opening new possibilities for researchers to explore transcript distributions at subcellular levels. However, existing methods have limitations in resolution, sensitivity, or speed. To overcome these challenges, we introduce SPRINTseq (Spatially Resolved and signal-diluted Next-generation Targeted sequencing), an innovative in situ sequencing strategy that combines hybrid block coding and molecular dilution strategies. Our method enables fast and sensitive high-resolution data acquisition, as demonstrated by recovering over 142 million transcripts using a 108 gene panel from 453,843 cells from four mouse brain coronal slices in less than two days. Using this advanced technology, we uncover the cellular and subcellular molecular architecture of Alzheimers disease, providing additional information into abnormal cellular behaviors and their subcellular mRNA distribution. This improved spatial transcriptomics technology holds great promise for exploring complex biological processes and disease mechanisms.

genomics↗

bioRxiv2022

Distinct modes of heat shock transcription factor interactions with mitotic chromosomes

A large number of transcription factors have been shown to bind and interact with mitotic chromosomes, which may promote the efficient reactivation of transcriptional programs following cell division. Although the DNA-binding domain (DBD) contributes strongly to TF behavior, TFs from the same DBD family can display distinct binding behaviors during mitosis. To define the mechanisms governing TF behavior during mitosis in mouse embryonic stem cells, we examined two related TFs: Heat Shock Factor 1 and 2 (HSF1 and HSF2). We found that HSF2 maintains site-specific binding genome-wide during mitosis, whereas HSF1 binding is globally decreased. Surprisingly, live-cell imaging shows that both factors appear excluded from mitotic chromosomes, and are similarly more dynamic in mitosis than in interphase. Exclusion from mitotic DNA is not due to extrinsic factors like nuclear import and export mechanisms. Rather, we found that the HSF2 DBD alone can coat mitotic chromosomes, but is insufficient to promote HSF1 coating. These data further confirm that site-specific binding and chromosome coating are independent properties, and that for some TFs, mitotic behavior is largely determined by the non-DBD regions.

molecular biology↗

bioRxiv2022

RefDeduR: A text-normalization and decision-tree aided R package enabling accurate and high-throughput reference deduplication for large datasets

As the scientific literature grows exponentially and research becomes increasingly interdisciplinary, accurate and high-throughput reference deduplication is vital in evidence synthesis studies (e.g., systematic reviews, meta-analyses) to ensure the completeness of datasets while reducing the manual screening burden. Existing tools fail to fulfill these emerging needs, as they are often labor-intensive, insufficient in accuracy, and limited to clinical fields. Here, we present RefDeduR, a text-normalization and decision-tree aided R package that enables accurate and high-throughput reference deduplication. We modularize the pipeline into text normalization, three-step exact matching, and two-step fuzzy matching processes. We also introduce a decision-tree algorithm, consider preprints when they co-exist with a peer-reviewed version, and provide actionable recommendations. Therefore, the tool is customizable, accurate, high-throughput, and practical. RefDeduR provides an effective solution to perform reference deduplication and represents a valuable advance in expanding the open-source toolkit to support evidence synthesis research.

scientific communication and education↗

bioRxiv2022

A Purinergic Mechanism Underlying Metformin Regulation of Hyperglycemia

Metformin, created in 1922, has been the first-line medication treating type 2 diabetes mellitus for almost 70 years; however, its mechanism of action has been heavily debated, partly because most prior studies used supratherapeutic concentrations exceeding 1mM. Here we report that at a clinically relevant concentration of 10 M, metformin blocks high glucose-stimulated ATP secretion from hepatocytes mediating its antihyperglycemic action. Following glucose administration, mice demonstrate increased circulating ATP concentrations, which are prevented by metformin. Extracellular ATP through P2Y2 receptors (P2Y2R) compromises insulin-induced AKT activation and increases hepatic glucose production. In addition, metformin-dependent improvement in glucose tolerance is abolished in P2Y2R-null mice. Thus, removing the target of extracellular ATP, P2Y2R, mimics the effects of metformin, revealing a novel purinergic antidiabetic mechanism for metformin. One-Sentence SummaryMetformin abolishes high glucose-stimulated ATP secretion, preventing purinergic mechanism-mediated hepatic insulin resistance and glucose production.

pharmacology and toxicology↗

bioRxiv2022

Yeast mtDNA transcription initiation in single nucleotide addition steps

Transcription initiation catalyzed by the RNA polymerase is a multistep process involving promoter binding, transcription bubble formation, abortive RNA synthesis, and transition into elongation following promoter escape. We report cryo-EM structures of yeast mitochondrial RNA polymerase initiation complexes (ICs) with transcription factor MTF1 catalyzing RNA synthesis from de novo initiation to 6-mer synthesis at single-nucleotide steps on fully-resolved transcription bubbles. The growing RNA:DNA hybrid is accommodated by continuous scrunching of the template strand while the non-template and MTF1 C-tail in the polymerase cleft are structurally reorganized. Each nucleotide addition accumulates stress energy, which drives abortive RNA synthesis during early transcription initiation steps and promoter release later. The non-template scrunches as loops in IC2/IC3, and unscrunching assists abortive synthesis of 2-/3-mer RNAs. Subsequently, in IC5 and IC6, the non-template strand assumes a stable structure by stacking its bases into a spiral staircase-like structure that supports processive synthesis. In IC6, the template scrunches to the maximum and places the -1 nucleotide in a pocket near the thumb domain. Subsequently, the -1 nucleotide acts as a pivot point for promoter escape ushering the IC into the elongation phase. The structural snapshots visualize the interplay between abortive and productive synthesis regulating transcription initiation.

biochemistry↗

bioRxiv2022

Nogo-A regulates the fate of human dental pulp stem cells towards osteogenic, adipogenic, and neurogenic differentiation

Human teeth are highly innervated organs that contain a variety of mesenchymal stem cell populations that could be used for cell-based regenerative therapies. Specific molecules are often used in these treatments to favorably modulate stem cells function and fate. Nogo-A, a key regulator of neuronal growth and differentiation, is already used in clinical tissue regeneration trials. While the functions of Nogo-A in neuronal tissues are extensively explored, its role in teeth still remains unknown. In this work, we first immunohistochemically analyzed the distribution of Nogo-A protein in the dental pulp of human teeth. Nogo-A is localized in a variety of cellular and structural components of the dental pulp, including odontoblasts, fibroblasts, neurons and vessels. We also cross-examined Nogo expression in the various pulp cell clusters in a single cell RNA sequencing dataset of human dental pulp, which showed high levels of expression in all cell clusters, including that of stem cells. We then assessed the role of Nogo-A on the fate of human dental pulp stem cells and their differentiation capacity in vitro. Using immunostaining, Alizarin Red S and Oil Red O staining we showed that Nogo-A delayed the differentiation of cultured dental pulp stem cells towards the osteogenic, adipogenic and neurogenic lineages, while addition of the blocking anti-Nogo-A antibody had opposite effects. These results were further confirmed by qRT-PCR, which demonstrated overexpression of genes involved in osteogenic (RUNX2, ALP, SP7/OSX), adipogenic (PPAR-{gamma}2, LPL) and neurogenic (DCX, TUBB3, NEFL) differentiation in presence of the anti-Nogo-A antibody. Conversely, the osteogenic and adipogenic genes were downregulated by Nogo-A. Taken together, our results show that the functions of Nogo-A are not restricted to neuronal cells, but are extended to other cell populations, including dental pulp stem cells. We show that Nogo-A regulates their fates towards osteogenic, adipogenic and neurogenic differentiation, thus indicating its potential use in the clinics.

cell biology↗

bioRxiv2022

Global loss of fine-scale chromatin architecture and rebalancing of gene expression during early colorectal cancer development

Although 3D genome architecture can be essential for gene regulation, the biological implications of long-range chromatin interactions in disease remain elusive. In this study, we traced the early evolution and malignant transformation of colorectal cancer by generating high-resolution chromatin conformation maps of 33 colon samples spanning different stages of early neoplastic growth from polyps of Familial Adenomatous Polyposis (FAP) patients. Our analysis reveals a substantial progressive loss of genome-wide cis-regulatory connectivity at early stages of malignancy, which correlates with a non-linear effect on gene regulation. Genes with high promoter-enhancer (P-E) connectivity in unaffected mucosa are not correlated with elevated baseline expression, but instead tend to be up-regulated at advanced stages. Inhibition of highly connected promoters preferentially represses gene expression in colorectal cancer cells relative to normal colonic epithelial cells. Our results suggest a two-phase model whereby neoplastic transformation reduces P-E connectivity from a redundant state to a rate-limiting one for transcriptional levels. Overall, our study illuminates the intricate interplay between 3D genome architecture and gene regulation during early colorectal cancer progression, and provides valuable insights for potential therapeutic interventions targeting the connectivity of cis-regulatory elements.

genomics↗

bioRxiv2022

Mechanism of Ca2+ transport by ferroportin

Ferroportin (Fpn) is a transporter that releases Fe2+ from cells and is important for iron homeostasis in circulation. Export of Fe2+ by Fpn is coupled to import of H+ to maintain charge balance. Although Ca2+ was shown to modulate Fe2+ transport in Fpn, transport of Ca2+ by Fpn has not been demonstrated. Here we show that human Fpn (HsFpn) mediates Ca2+ transport, and that the Ca2+ transport does not rely on the transport of other ions. We determine the structure of Ca2+-bound HsFpn and identify a single Ca2+ binding site distinct from the Fe2+ binding sites. Further studies validate the Ca2+ binding site and show that Ca2+ transport is inhibited in the presence of Fe2+ but not vice versa. Function of Fpn as a Ca2+ uniporter in the absence of Fe2+ provides a molecular basis for regulations of iron homeostasis by Ca2+.

biochemistry↗