Critical Sites Research Articles

How can informal science learning centers advance climate resilience partnerships? Lessons from two coastal communities

ABSTRACT Informal science learning centers (ISLCs) like zoos, aquariums and botanic gardens are trusted community assets and perceived as critical sites for learning outside the classroom for multigenerational learners. Moreover, their role in engaging the public in critical topics, such as climate change is widely recognized. As extreme weather events grow more frequent, building climate resilient social and ecological systems will be necessary. However, how ISLCs facilitate climate resilience is understudied. This paper presents findings from two qualitative case studies of climate resilience projects, through partnerships between community organizations and ISLCs. The results demonstrated the need to prioritize relationship building so that organizations with distinct approaches authentically appreciate each other’s work and foster power symmetries. Diverse definitions of ‘resilience’ emerged, where ecological and social resilience held unique meaning for residents most vulnerable to climate events. Ultimately, the research highlighted how ISLCs and community partners can advance equitable and inclusive climate resilience.

Identification of novel monoclonal antibodies specific for the conserved epitopes in the E2 protein of genotype 2 classical swine fever virus: implication for differential diagnosis

Since the last century, the spread of the genotype 2 classical swine fever virus (CSFV) has caused significant issues for the pig breeding industries. Ideal strategies for controlling CSFV include vaccination and keeping farms free of CSFV. For vaccination, several attenuated CSFV viruses originating from genotype 1 are widely used; for the latter, accurate diagnosis is required for detection of the CSFV infection. Nucleic acid testing for CSFV usually uses tonsil samples, which requires an inconvenient sampling operation that injures pigs. Commercial serological tests for CSFV antibodies or antigens are unable to distinguish the genotype for originating virus. In this study, 20 mAbs were developed from the mice hybridoma cells. Four of the mAbs were identified to have the ability to only recognize the peptides derived from sub-genotype 2.1 strain, and two of them, MM1 and MM5, were further studied to identify critical binding sites (epitopes) on the E2 protein of CSFV. A total of 353 genotype 2 collections were made worldwide in GeneBank, 90.9% of which contained MM1 or MM5 epitopes. Moreover, 95.1% of sub-genotype 2.1 isolations contained MM5 epitope. Therefore, MM1 and MM5 have the potential to be developed as a diagnostic tool for detection of genotype 2 virus antigen by indirect ELISA or antibodies by competitive ELISA.

Evolution and functional role prediction of the CYP6DE and CYP6DJ subfamilies in Dendroctonus (Curculionidae: Scolytinae) bark beetles.

Dendroctonus-bark beetles are natural components and key ecological agents of coniferous forests. They spend most of their lives under the bark, where they are exposed to highly toxic terpenes present in the oleoresin. Cytochrome P450 (CYP) is a multigene family involved in the detoxification of these compounds. It has been demonstrated that CYP6DE and CYP6DJ subfamilies hydroxylate monoterpenes, whose derivatives can act as pheromone synergist compounds or be pheromones themselves in these insects. Given the diversity and functional role of CYPs, we investigated whether these cytochromes have retained their function throughout the evolution of these insects. To test this hypothesis, we performed a Bayesian phylogenetic analysis to determine phylogenetic subgroups of cytochromes in these subfamilies. Subgroups were mapped and reconciled with the Dendroctonus phylogeny. Molecular docking analyses were performed with the cytochromes of each subgroup and enantiomers of α-pinene and β-pinene, (+)-3-carene, β-myrcene and R-(+)-limonene. In addition, functional divergence analysis was performed to identify critical amino acid sites that influence changes in catalytic site conformation and/or protein folding. Three and two phylogenetic subgroups were recovered for the CYP6DE and CYP6DJ subfamilies, respectively. Mapping and reconciliation analysis showed different gain and loss patterns for cytochromes of each subgroup. Functional predictions indicated that the cytochromes analyzed are able to hydroxylate all monoterpenes; however, they showed preferential affinities to different monoterpenes. Functional divergence analyses indicated that the CYP6DE subfamily has experimented type I and II divergence, whereas the CYP6DJ subfamily has evolved under strong functional constraints. Results suggest cytochromes of the CYP6DE subfamily evolve to reinforce their detoxifying capacity hydroxylating mainly α- and β-pinene to (+) and (-)-trans-verbenol, being the negative enantiomer used as a pheromone by several Dendroctonus species; whereas cytochromes of the CYP6DJ subfamily appear to retain their original function related to the detoxification of these compounds.

‘A video or a flat fee?’ on the performances of concert fees

ABSTRACTWhile the literature on musical employment is growing, little research has been conducted on how concert fees are calculated, discussed, or contested. This article aims to explore these questions by drawing on the in-depth study of one new actor within the live music business: Sofar Sounds. Since 2009, Sofar Sounds has been organizing ‘secret concerts’ in ‘unconventional spaces.’ Between 2017 and 2019, the company has been publicly criticized on several occasions for its fee policy. I analyze these controversies over musicians’ remuneration as a critical site to understand the kind of economization performed within music industries. I argue that taking fees seriously allows for considering calculation of musical remuneration as a world-making operation. I identify three different and competing ways to calculate musicians’ fee: ‘appointment-fee,’ ‘co-production-fee,’ and ‘compensation-fee.’ I show that these calculations are performative achievements that contribute to the defining of what a musical performance is and of the actors who take part in it. In conclusion, I argue that the controversies about Sofar Sounds’ musicians’ fee policy cannot be understood only from a market and commodity point of view. The company uses ‘exposure’ to attach musicians and to strengthen its own (financial) value.

Conformal covariance of connection probabilities and fields in 2D critical percolation

AbstractFitting percolation into the conformal field theory framework requires showing that connection probabilities have a conformally invariant scaling limit. For critical site percolation on the triangular lattice, we prove that the probability that n vertices belong to the same open cluster has a well‐defined scaling limit for every . Moreover, the limiting functions transform covariantly under Möbius transformations of the plane as well as under local conformal maps, that is, they behave like correlation functions of primary operators in conformal field theory. In particular, they are invariant under translations, rotations and inversions, and for any . This implies that and , for some constants C2 and C3.We also define a site‐diluted spin model whose n‐point correlation functions Cn can be expressed in terms of percolation connection probabilities and, as a consequence, have a well‐defined scaling limit with the same properties as the functions . In particular, . We prove that the magnetization field associated with this spin model has a well‐defined scaling limit in an appropriate space of distributions. The limiting field transforms covariantly under Möbius transformations with exponent (scaling dimension) 5/48. A heuristic analysis of the four‐point function of the magnetization field suggests the presence of an additional conformal field of scaling dimension 5/4, which counts the number of percolation four‐arm events and can be identified with the so‐called “four‐leg operator” of conformal field theory.

A PrP EGFR signaling axis controls neural stem cell senescence through modulating cellular energy pathways

Mis-folding of the prion protein (PrP) is known to cause neurodegenerative disease; however, the native function of this protein remains poorly defined. PrP has been linked with many cellular functions, including cellular proliferation and senescence. It is also known to influence epidermal growth factor receptor (EGFR) signaling, a pathway that is itself linked with both cell growth and senescence. Adult neural stem cells (NSCs) persist at low levels in the brain throughout life and retain the ability to proliferate and differentiate into new neural lineage cells. KO of PrP has previously been shown to reduce NSC proliferative capacity. We used PrP KO and WT NSCs from adult mouse brain to examine the influence of PrP on cellular senescence, EGFR signaling, and the downstream cellular processes. PrP KO NSCs showed decreased cell proliferation and increased senescence in invitro cultures. Expression of EGFR was decreased in PrP KO NSCs compared with WT NSCs and additional supplementation of EGF was sufficient to reduce senescence. RNA-seq analysis confirmed that significant changes were occurring at the mRNA level within the EGFR signaling pathway and these were associated with reduced expression of mitochondrial components and correspondingly reduced mitochondrial function. Metabolomic analysis of cellular energy pathways showed that blockages were occurring at critical sites for production of energy and biomass, including catabolism of pyruvate. We conclude that, in the absence of PrP, NSC growth pathways are downregulated as a consequence of insufficient energy and growth intermediates.

SARS-COV-2 protein NSP9 promotes cytokine production by targeting TBK1.

SARS-COV-2 infection-induced excessive or uncontrolled cytokine storm may cause injury of host tissue or even death. However, the mechanism by which SARS-COV-2 causes the cytokine storm is unknown. Here, we demonstrated that SARS-COV-2 protein NSP9 promoted cytokine production by interacting with and activating TANK-binding kinase-1 (TBK1). With an rVSV-NSP9 virus infection model, we discovered that an NSP9-induced cytokine storm exacerbated tissue damage and death in mice. Mechanistically, NSP9 promoted the K63-linked ubiquitination and phosphorylation of TBK1, which induced the activation and translocation of IRF3, thereby increasing downstream cytokine production. Moreover, the E3 ubiquitin ligase Midline 1 (MID1) facilitated the K48-linked ubiquitination and degradation of NSP9, whereas virus infection inhibited the interaction between MID1 and NSP9, thereby inhibiting NSP9 degradation. Additionally, we identified Lys59 of NSP9 as a critical ubiquitin site involved in the degradation. These findings elucidate a previously unknown mechanism by which a SARS-COV-2 protein promotes cytokine storm and identifies a novel target for COVID-19 treatment.

Space invaders: First-time users feel like intruders in the makerspace

Makerspaces have proven to be mainstays within library ecosystems. However, alongside the continued popularization of library makerspaces, there remains a seemingly immovable issue endemic to these environments; makerspaces continue to attract a narrow demographic of patrons. The threshold of the makerspace serves as a critical site for inquiry, specifically, for insight around students' everyday life information seeking (ELIS) behaviors. This study responds to the research question, “Why do students from underrepresented communities turn away at the threshold of a makerspace?” The research design is methodologically informed by participatory action research (PAR) and grounded theory and uses a virtual reality (VR) makerspace to provide a consistent “threshold” experience to capture students' fleeting first impressions. The research findings offer novel insight into the information seeking behaviors of students by capturing and analyzing critical data that haven't been collected before: the real-time thoughts and feelings of students from underrepresented communities entering a makerspace for the first time.

Post-conflict statecraft, land governance and exclusion in Hargeisa, Somaliland

This paper explores urban land governance in Hargeisa as a critical site of Somaliland’s post-conflict statecraft. Two key issues make this study imperative. First, the current research on Somaliland focuses on the central authority( 1 ) with scant attention to the organization and functioning of the urban state and its effect for the urban poor, thus obscuring the importance of the conurbation as a site for statecraft. Second, Somaliland’s post-conflict statecraft is marked by inconsistencies, previously unexplored. While the creation of the subnational state is characterized as bottom-up, with its origins in community-led peacebuilding, its governance practices are characterized by exclusionary top-down procedures imported from colonial and postcolonial periods. Based on interviews with key informants, archival research and document analysis, I historicize these layers of the state-building processes. I argue that the top-down approach of post-conflict land governance, a critical site of statecraft, marginalizes the disadvantaged by creating bureaucracies that favour the affluent.

Comprehending the practical implementation of permanganate and ferrate for water remediation in complex water matrices

Most previous studies examined permanganate or ferrate oxidation using various emerging pollutants (EPs) spiked in ultrapure water with concentrations of orders-of-magnitude higher than those in natural waters. In present study, we assessed the efficiency of permanganate and ferrate (with ozone as a comparison) at mg L−1 level to remove selected EPs at μg L−1 level in complex water matrices. The efficiency of permanganate and ferrate is more easily affected by the humic acid in synthetic water or dissolved organic matter (DOM) in natural river water compared to ozone. Experiment results revealed that humic acid or DOM were not mineralized by oxidants, but changed in compositional nature, including decreases in the aromaticity, electron-donating capacity, and average molecular weight. At molecular level, condensed aromatic, lignin-like, and tannin-like components in humic acid and DOM are the critical sites being attacked by permanganate or ferrate, the alkene groups and aromatic structures were oxidized predominantly to carboxylic acids. Overall, the present study provided insights into the performance of permanganate and ferrate used for EPs treatment under realistic conditions, as well as alternations of DOM that can be expected following exposure to these oxidants.

MRE11:p.K464R mutation mediates olaparib resistance by enhancing DNA damage repair in HGSOC

BackgroundAlthough the clinical application of PARP inhibitors has brought hope to ovarian cancer, the problem of its resistance has become increasingly prominent. Therefore, clinical experts have been focused on finding specific indicators and therapeutic targets that can be used for resistance monitoring of PARP inhibitors.ResultsBy cfDNA detecting during Olaparib maintenance therapy in platinum-sensitive relapsed ovarian cancer, we found the presence of MRE11:p.K464R mutation was strongly associated with acquired Olaparib resistance. Structural analysis revealed that the MRE11:p.K464R mutation is situated at a critical site where the MRE11 protein interacts with other biomolecules, leading to potential structural and functional abnormalities of MRE11 protein. Functionally, MRE11:p.K464R mutation enhanced the tolerance of Olaparib by reducing the DNA damage. Mechanistically, MRE11:p.K464R mutation improved the efficiency of DNA damage repair and induce Olaparib resistance by enhancing its binding activity with the interacting proteins (including RAD50 and RPS3). Among them, the enhanced binding of MRE11:p.K464R mutation to RAD50/RPS3 facilitated non-homologous end joining (NHEJ) repair in tumor cells, thereby expanding the scope of research into acquired resistance to PARP inhibitors.ConclusionsOur findings provide a theoretical basis for MRE11:p.K464R mutation as a specific indicator of resistance monitoring in Olaparib treatment, and the exploration of its resistance mechanism provides a novel insights for the formulation of combination ther therapies after Olaparib resistance.

URBAN ECOLOGICAL FUTURES: Five Eco‐Community Strategies for more Sustainable and Equitable Cities

AbstractCities are critical sites for understanding, and potentially ameliorating, the effects of global ecological change, the climate emergency and natural resource depletion. Contemporary cities are sociomaterially connected through global markets, trade and transportation, placing ever‐increasing demands on the natural environment and generating dangerous pollutants and emissions. Current approaches to address these environmental crises are dominated by neoliberal forms of ‘green’ urban development, carbon accounting and techno‐economic solutions, which extend corporate control over cities and tend to entrench inequality. A more strategic approach for enabling ecologically sustainable and equitable urban futures is urgently needed. We present five strategies for urban ecological futures in the global North, derived from qualitative and ethnographic empirical research with international eco‐communities, which open up discussions about how to tackle this challenge by acknowledging the role and potential of: (1) non‐extractive community economies; (2) democratic processes of co‐operative action; (3) social approaches to resource management; (4) participatory collaborative governance; and (5) urban heterogeneity and social justice. We explore the relational, contested and contextual processes through which these approaches could become embedded in urban policy and planning, thereby offering the strategic capacity required to move towards truly sustainable cities.

Non-Structural Protein-W61 as a Novel Target in Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV): An In-Vitro and In-Silico Study on Protein-Protein Interactions with Nucleoprotein and Viral Replication.

The non-structural protein (NSs) and nucleoprotein (NP) of the severe fever with thrombocytopenia syndrome virus (SFTSV) encoded by the S segment are crucial for viral pathogenesis. They reside in viroplasm-like structures (VLS), but their interaction and their significance in viral propagation remain unclear. Here, we investigated the significance of the association between NSs and NP during viral infection through in-silico and in-vitro analyses. Through in-silico analysis, three possible binding sites were predicted, at positions C6S (Cystein at 6th position to Serine), W61Y (Tryptophan 61st to Tyrosine), and S207T (Serine 207th to Threonine), three mutants of NSs were developed by site-directed mutagenesis and tested for NP interaction by co-immunoprecipitation. NSsW61Y failed to interact with the nucleoprotein, which was substantiated by the conformational changes observed in the structural analyses. Additionally, molecular docking analysis corroborated that the NSW61Y mutant protein does not interact well compared to wild-type NSs. Over-expression of wild-type NSs in HeLa cells increased the SFTSV replication by five folds, but NSsW61Y exhibited 1.9-folds less viral replication than wild-type. We demonstrated that the W61Y alteration was implicated in the reduction of NSs-NP interaction and viral replication. Thus, the present study identified a critical NSs site, which could be targeted for development of therapeutic regimens against SFTSV.

Reversible Pulsed Electrical Fields as an In Vivo Tool to Study Cardiac Electrophysiology: The Advent of Pulsed Field Mapping.

During electrophysiological mapping of tachycardias, putative target sites are often only truly confirmed to be vital after observing the effect of ablation. This lack of mapping specificity potentiates inadvertent ablation of innocent cardiac tissue not relevant to the arrhythmia. But if myocardial excitability could be transiently suppressed at critical regions, their suitability as targets could be conclusively determined before delivering tissue-destructive ablation lesions. We studied whether reversible pulsed electric fields (PFREV) could transiently suppress electrical conduction, thereby providing a means to dissect tachycardia circuits in vivo. PFREV energy was delivered from a 9-mm lattice-tip catheter to the atria of 12 swine and 9 patients, followed by serial electrogram assessments. The effects on electrical conduction were explored in 5 additional animals by applying PFREV to the atrioventricular node: 17 low-dose (PFREV-LOW) and 10 high-dose (PFREV-HIGH) applications. Finally, in 3 patients manifesting spontaneous tachycardias, PFREV was applied at putative critical sites. In animals, the immediate post-PFREV electrogram amplitudes diminished by 74%, followed by 78% recovery by 5 minutes. Similarly, in patients, a 69.9% amplitude reduction was followed by 84% recovery by 3 minutes. Histology revealed only minimal to no focal, superficial fibrosis. PFREV-LOW at the atrioventricular node resulted in transient PR prolongation and transient AV block in 59% and 6%, while PFREV-HIGH caused transient PR prolongation and transient AV block in 30% and 50%, respectively. The 3 tachycardia patients had atypical atrial flutters (n=2) and atrioventricular nodal reentrant tachycardia. PFREV at putative critical sites reproducibly terminated the tachycardias; ablation rendered the tachycardias noninducible and without recurrence during 1-year follow-up. Reversible electroporation pulses can be applied to myocardial tissue to transiently block electrical conduction. This technique of pulsed field mapping may represent a novel electrophysiological tool to help identify the critical isthmus of tachycardia circuits.

Nucleocapsid protein residues 35, 36, and 113 are critical sites in up-regulating the Interleukin-8 production via C/EBPα pathway by highly pathogenic porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly infectious and pathogenic agent that causes considerable economic damage in the swine industry. It regulates the inflammatory response, triggers inflammation-induced tissue damage, suppresses the innate immune response, and leads to persistent infection. Interleukin-8 (IL-8), a pro-inflammatory chemokine, plays a crucial role in inflammatory response during numerous bacteria and virus infections. However, the underlying mechanisms of IL-8 regulation during PRRSV infection are not well understood. In this study, we demonstrate that PRRSV-infected PAMs and Marc-145 cells release higher levels of IL-8. We screened the nucleocapsid protein, non-structural protein (nsp) 9, and nsp11 of PRRSV to enhance IL-8 promoter activity via the C/EBPα pathway. Furthermore, we identified that the amino acids Q35A, S36A, R113A, and I115A of the nucleocapsid protein play a crucial role in the induction of IL-8. Through reverse genetics, we generated two mutant viruses (rQ35-2A and rR113A), which showed lower induction of IL-8 in PAMs during infection. This finding uncovers a previously unrecognized role of the PRRSV nucleocapsid protein in modulating IL-8 production and provides insight into an additional mechanism by which PRRSV modulates immune responses and inflammation.

Viral sites: The oligoptical power of emergency operations centres (EOCs)

Countries all around the world are increasingly coordinating their strategic responses to global health emergencies inside specialized new command centres called emergency operations centres (EOCs). Those bunker-like EOCs are meticulously designed to function as the global health equivalent of war rooms and are rapidly emerging as the internationally preferred sites for ‘making’ global health security in the 21st century. This article advances an in-depth site-ontological investigation into those burgeoning EOC sites. It develops a three-step methodological analytics to reveal the specific economy of prefigurative power that EOCs exude in international relations and names this oligoptical power. The article further shows how this oligoptical power is fundamentally different from the more familiar Foucauldian notion of panoptical power and has very different ramifications as it circulates throughout contemporary international relations. Yet, precisely because the EOC exemplifies this global operation of oligoptical power, the article concludes, it can be considered as one of its international signal institutions – similarly to how the prison was once a critical institutional site for revealing the circulation of disciplinary power, the laboratory for performing the sociological examination of science, and the concentration camp for deepening the analysis of biopower.

A Shortcut from Genome to Drug: The Employment of Bioinformatic Tools to Find New Targets for Gastric Cancer Treatment.

Gastric cancer (GC) is a highly heterogeneous, complex disease and the fifth most common cancer worldwide (about 1 million cases and 784,000 deaths worldwide in 2018). GC has a poor prognosis (the 5-year survival rate is less than 20%), but there is an effort to find genes highly expressed during tumor establishment and use the related proteins as targets to find new anticancer molecules. Data were collected from the Gene Expression Omnibus (GEO) bank to obtain three dataset matrices analyzing gastric tumor tissue versus normal gastric tissue and involving microarray analysis performed using the GPL570 platform and different sources. The data were analyzed using the GEPIA tool for differential expression and KMPlot for survival analysis. For more robustness, GC data from the TCGA database were used to corroborate the analysis of data from GEO. The genes found in in silico analysis in both GEO and TCGA were confirmed in several lines of GC cells by RT-qPCR. The AlphaFold Protein Structure Database was used to find the corresponding proteins. Then, a structure-based virtual screening was performed to find molecules, and docking analysis was performed using the DockThor server. Our in silico and RT-qPCR analysis results confirmed the high expression of the AJUBA, CD80 and NOLC1 genes in GC lines. Thus, the corresponding proteins were used in SBVS analysis. There were three molecules, one molecule for each target, MCULE-2386589557-0-6, MCULE-9178344200-0-1 and MCULE-5881513100-0-29. All molecules had favorable pharmacokinetic, pharmacodynamic and toxicological properties. Molecular docking analysis revealed that the molecules interact with proteins in critical sites for their activity. Using a virtual screening approach, a molecular docking study was performed for proteins encoded by genes that play important roles in cellular functions for carcinogenesis. Combining a systematic collection of public microarray data with a comparative meta-profiling, RT-qPCR, SBVS and molecular docking analysis provided a suitable approach for finding genes involved in GC and working with the corresponding proteins to search for new molecules with anticancer properties.

Gender segregation & women’s rights in Muslim societies: de-constructing feminist opposition to spatial boundaries through the lens of feminist documentary film

ABSTRACT In many Muslim societies including Pakistan, the notions of spatial boundaries and gender segregation are becoming critical site for women’s rights and feminist activism. Sanctified through patriarchal culture and interpretations of religious scriptures, such notions undermine women’s agency and autonomy, hence invite greater attention from feminists, whereby they seek to unravel how these restrictive codes, deprive women of their fundamental rights such as access to the public sphere, education, and financial independence. Lately, feminists in Pakistan, have been demonstrating their opposition to these restrictions through various cultural and political activities that include the arrangement of the annual ‘Aurat March’, social media campaigns and other forms of cultural resistance. Feminist documentary has emerged as one of these effective tools, through which feminists confront religio-cultural constructs such as spatial boundaries and gender segregation, concepts that contribute to women’s oppression. These documentaries are providing new tools for cultural resistance and should be seen as a distinctive Muslim feminist documentary. Owing to the distinctive nature of feminist documentary in Pakistan, this paper explores feminist contestation of spatial boundaries through the lens of feminist documentary.

In Vitro 3D Spheroid Culture System Displays Sustained T Cell-dependent CLL Proliferation and Survival.

Chronic lymphocytic leukemia (CLL) cells are highly dependent on microenvironmental cells and signals. The lymph node (LN) is the critical site of in vivo CLL proliferation and development of resistance to both chemotherapy and targeted agents. We present a new model that incorporates key aspects of the CLL LN, which enables investigation of CLL cells in the context of a protective niche. We describe a three-dimensional (3D) in vitro culture system using ultra-low attachment plates to create spheroids of CLL cells derived from peripheral blood. Starting from CLL:T cell ratios as observed in LN samples, CLL activation was induced by either direct stimulation and/or indirectly via T cells. Compared with two-dimensional cultures, 3D cultures promoted CLL proliferation in a T cell-dependent manner, and enabled expansion for up to 7 weeks, including the formation of follicle-like structures after several weeks of culture. This model enables high-throughput drug screening, of which we describe response to Btk inhibition, venetoclax resistance, and T cell-mediated cytotoxicity as examples. In summary, we present the first LN-mimicking in vitro 3D culture for primary CLL, which enables readouts such as real-time drug screens, kinetic growth assays, and spatial localization. This is the first in vitro CLL system that allows testing of response and resistance to venetoclax and Bruton's tyrosine kinase inhibitors in the context of the tumor microenvironment, thereby opening up new possibilities for clinically useful applications.

The iron chaperone poly(rC)-binding protein 1 regulates iron efflux through intestinal ferroportin in mice

AbstractIron is an essential nutrient required by all cells but used primarily for red blood cell production. Because humans have no effective mechanism for ridding the body of excess iron, the absorption of dietary iron must be precisely regulated. The critical site of regulation is the transfer of iron from the absorptive enterocyte to the portal circulation via the sole iron efflux transporter, ferroportin. Here, we report that poly(rC)-binding protein 1 (PCBP1), the major cytosolic iron chaperone, is necessary for the regulation of iron flux through ferroportin in the intestine of mice. Mice lacking PCBP1 in the intestinal epithelium exhibit low levels of enterocyte iron, poor retention of dietary iron in enterocyte ferritin, and excess efflux of iron through ferroportin. Excess iron efflux occurred despite lower levels of ferroportin protein in enterocytes and upregulation of the iron regulatory hormone hepcidin. PCBP1 deletion and the resulting unregulated dietary iron absorption led to poor growth, severe anemia on a low-iron diet, and liver oxidative stress with iron loading on a high-iron diet. Ex vivo culture of PCBP1-depleted enteroids demonstrated no defects in hepcidin-mediated ferroportin turnover. However, measurement of kinetically labile iron pools in enteroids competent or blocked for iron efflux indicated that PCBP1 functioned to bind and retain cytosolic iron and limit its availability for ferroportin-mediated efflux. Thus, PCBP1 coordinates enterocyte iron and reduces the concentration of unchaperoned “free” iron to a low level that is necessary for hepcidin-mediated regulation of ferroportin activity.