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Autoimmune hepatitis (AIH) is a chronic liver disease characterized by immune dysregulation and hepatocyte damage. FKBP38, a member of the immunophilin family, has been implicated in immune regulation and the modulation of intracellular signaling pathways; however, its role in AIH pathogenesis remains poorly understood. In this study, we aimed to investigate the effects of hepatic FKBP38 deletion on AIH using a hepatic FKBP38 knockout (LKO) mouse model created via cre-loxP technology. We compared the survival rates, incidence, and severity of AIH in LKO mice with those in control mice. Our findings revealed that hepatic FKBP38 deletion resulted in an unfavorable prognosis in LKO mice with AIH. Specifically, LKO mice exhibited heightened liver inflammation and extensive hepatocyte damage compared to control mice, with a significant decrease in anti-apoptotic proteins and a marked increase in pro-apoptotic proteins. Additionally, transcriptional and translational levels of pro-inflammatory cytokines and chemokines were significantly increased in LKO mice compared to control mice. Immunoblot analysis showed that MCP-1 expression was significantly elevated in LKO mice. Furthermore, the phosphorylation of p38 was increased in LKO mice with AIH, indicating that FKBP38 deletion promotes liver injury in AIH by upregulating p38 phosphorylation and increasing MCP-1 expression. Immune cell profiling demonstrated elevated populations of T, NK, and B cells, suggesting a dysregulated immune response in LKO mice with AIH. Overall, our findings suggest that FKBP38 disruption exacerbates AIH severity by augmenting the immune response by activating the MCP-1/p38 signaling pathway., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The FK506 binding protein 51 (FKBP51) is an appealing drug target due to its role in several diseases such as depression, anxiety, chronic pain and obesity. Towards this, selectivity versus the close homolog FKBP52 is essential. However, currently available FKBP51-selective ligands such as SAFit2 are too large and lack drug-like properties. Here, we present a structure activity relationship (SAR) analysis of the pipecolic ester moiety of SAFit1 and SAFit2, which culminated in the discovery of the 1,4-pyrazolyl derivative 23 d, displaying a binding affinity of 0.077 μM for FKBP51, reduced molecular weight (541.7 g/mol), lower hydrophobicity (cLogP=3.72) and higher ligand efficiency (LE=0.25). Cocrystal structures revealed the importance of the 1,4- and 1,3,4- substitution patterns of the pyrazole ring versus the 1,4,5 arrangement., (© 2024 The Author(s). ChemMedChem published by Wiley-VCH GmbH.)

Stress and inflammation are risk factors for schizophrenia. Chronic psychosocial stress is associated with subcortical hyperdopaminergia, a core feature of schizophrenia. Hyperdopaminergia arises from midbrain neurons, leading us to hypothesise that changes in stress response pathways may occur in this region. To identify whether transcriptional changes in glucocorticoid and mineralocorticoid receptors (NR3C1/GR, NR3C2/MR) or other stress signalling molecules (FKBP4, FKBP5) exist in schizophrenia midbrain, we measured gene expression in the human brain (N = 56) using qRT-PCR. We assessed whether alterations in these mRNAs were related to previously identified high/low inflammatory status. We investigated relationships between stress-related transcripts themselves, and between FKBP5 mRNA, dopaminergic, and glial cell transcripts in diagnostic and inflammatory subgroups. Though unchanged by diagnosis, GR mRNA levels were reduced in high inflammatory compared to low inflammatory schizophrenia cases (p = 0.026). We found no effect of diagnosis or inflammation on MR mRNA. FKBP4 mRNA was decreased and FKBP5 mRNA was increased in schizophrenia (p < 0.05). FKBP5 changes occurred in high inflammatory (p < 0.001), whereas FKBP4 changes occurred in low inflammatory schizophrenia cases (p < 0.05). The decrease in mRNA encoding the main stress receptor (GR), as well as increased transcript levels of the stress-responsive negative regulator (FKBP5), may combine to blunt the midbrain response to stress in schizophrenia when neuroinflammation is present. Negative correlations between FKBP5 mRNA and dopaminergic transcripts in the low inflammatory subgroup suggest higher levels of FKBP5 mRNA may also attenuate dopaminergic neurotransmission in schizophrenia even when inflammation is absent. We report alterations in GR-mediated stress signalling in the midbrain in schizophrenia., Competing Interests: Declaration of competing interest As required for submission of this manuscript to Journal of Psychiatric Research, we confirm that none of the authors listed on this manuscript have any conflicts of interest to declare., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Age-associated adipose tissue (AT) dysfunction is multifactorial and often leads to detrimental health consequences. AT is highly vascularized and endothelial cells (ECs) has been recently identified as a key regulator in the homeostasis of AT. However, the alteration of cell composition in AT during aging and the communication between endothelial cells and adipocytes remain poorly understood. In this study, we take advantage of single nucleus RNA sequencing analysis, and discovered a group of FKBP5+ ECs specifically resident in aged AT. Of interest, FKBP5+ ECs exhibited the potential for endothelial-to-mesenchymal transition (EndoMT) and exhibited a critical role in regulating adipocytes. Furthermore, lineage tracing experiments demonstrated that ECs in aged AT tend to express FKBP5 and undergo EndoMT with progressive loss of endothelial marker. This study may provide a basis for a new mechanism of microvascular ECs-induced AT dysfunction during aging., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Aims: FKBP5 encodes FKBP51, which has been implicated in stress-related psychiatric disorders, and its expression is often increased under chronic stress, contributing to mental dysfunctions. However, the precise role of FKBP51 in brain inflammation remains unclear. This study aimed to investigate the role of FKBP51 in microglia-mediated inflammatory responses in the central nervous system., Main Methods: We employed a peripheral lipopolysaccharide (LPS) administration model to compare microglial activation and cytokine gene expression between Fkbp5 knockout (Fkbp5-KO) and wild-type (WT) male mice. Additionally, we used both BV2 and primary microglia in vitro to examine how Fkbp5 deletion influenced inflammation-related pathways and microglial functions., Key Findings: This study revealed that systemic LPS-induced microglial activation was significantly attenuated in Fkbp5-KO mice compared with WT mice. In Fkbp5-KO mice following the LPS challenge, there was a notable decrease in the expression of pro-inflammatory genes, coupled with an increase in the anti-inflammatory gene Arg1. Furthermore, Fkbp5 knockdown in BV2 microglial cells led to reduced expression of LPS-induced inflammatory markers, and targeted inhibition of NF-κB activation, while Akt signaling remained unaffected. Similar results were observed in Fkbp5-KO primary microglia, which exhibited not only decreased microglial activation but also a significant reduction in phagocytic activity in response to LPS stimulation., Significance: This study highlights the critical role of FKBP51 in LPS-induced microglial activation and neuroinflammation. It shows that reducing FKBP51 levels attenuates inflammation through NF-κB signaling in microglia. This suggests that FKBP51 is a potential target for alleviating neuroinflammation-induced stress responses., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Access to small, rigid, and sp 3 -rich molecules is a major limitation in the drug discovery for challenging protein targets. FK506-binding proteins hold high potential as drug targets or enablers of molecular glues but are fastidious in the chemotypes accepted as ligands. We here report an enantioselective synthesis of a highly rigidified pipecolate-mimicking tricyclic scaffold that precisely positions functional groups for interacting with FKBPs. This was enabled by a 14-step gram-scale synthesis featuring anodic oxidation, stereospecific vinylation, and N-acyl iminium cyclization. Structure-based optimization resulted in the discovery of FKBP inhibitors with picomolar biochemical and subnanomolar cellular activity that represent the most potent FKBP ligands known to date., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Deficiencies in maternal nutrition have long-term consequences affecting brain development of the progeny and its behavior. In the present work, female mice were exposed to a normal-protein or a low-protein diet during gestation and lactation. We analyzed behavioral and molecular consequences of malnutrition in dams and how it affects female offspring at weaning. We have observed that a low-protein diet during pregnancy and lactation leads to anxiety-like behavior and anhedonia in dams. Protein malnutrition during the perinatal period delays physical and neurological development of female pups. Glucocorticoid levels increased in the plasma of malnourished female offspring but not in dams when compared to the control group. Interestingly, the expression of glucocorticoid receptor (GR) was reduced in hippocampus and amygdala on both malnourished dams and female pups. In addition, malnourished pups exhibited a significant increase in the expression of Dnmt3b, Gadd45b, and Fkbp5 and a reduction in Bdnf VI variant mRNA in hippocampus. In contrast, a reduction on Dnmt3b has been observed on the amygdala of weaned mice. No changes have been observed on global methylation levels (5-methylcytosine) in hippocampal genomic DNA neither in dams nor female offspring. In conclusion, deregulated behaviors observed in malnourished dams might be mediated by a low expression of GR in brain regions associated with emotive behaviors. Additionally, low-protein diet differentially deregulates the expression of genes involved in DNA methylation/demethylation machinery in female offspring but not in dams, providing an insight into regional- and age-specific mechanisms due to protein malnutrition., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Social status directly affects the health of humans and other animals. Low status individuals receive more antagonistic encounters, have fewer supportive relationships and have worse health outcomes. However, the physiological and cellular processes that mediate the relationship between the social environment and health are incompletely known. Epigenetic regulation of the hypothalamic-pituitary-adrenal (HPA) axis, the neuroendocrine pathway that activates in response to stressors, may be one process that is sensitive to the social environment. Here, we experimentally manipulated plumage, a key social signal in female tree swallows (Tachycineta bicolor) and quantified methylation of four genes in the HPA axis before and after treatment. We found that dulling the white breast plumage affected methylation in one gene, CRHR1; however, the effect depended on the original brightness of the bird. Methylation in this gene was correlated with baseline corticosterone levels, suggesting that DNA methylation of CRHR1 helps regulate glucocorticoid production in this species. Methylation in two other genes, FKBP5 and GR, changed over the course of the experiment, independent of treatment. These results show that methylation of these genes is labile into adulthood and suggest that epigenetic regulation of the HPA axis could help birds respond to current environmental conditions., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Background: Facial infiltrating lipomatosis is characterized by excessive growth of adipose tissue. Its etiology is associated with somatic phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) variants, but the specific mechanisms are not yet fully understood., Methods: We collected facial adipose tissue from both FIL patients and non-FIL individuals, isolated the stromal vascular fraction (SVF) and performed single-cell transcriptome sequencing on these samples., Results: We mapped out the cellular landscape within the SVF, with a specific focus on a deeper analysis of fibro-adipogenic precursor cells (FAPs). Our analysis revealed that FAPs from FIL patients (FIL-FAPs) significantly overexpressed FK506 binding protein 51 (FKBP5) compared to FAPs from individuals without FIL. Further experiments indicated that FKBP5 is regulated by the PI3K-AKT signaling pathway. The overactivation of this pathway led to an increase in FKBP5 expression. In vitro experiments demonstrated that FKBP5 promoted adipogenic differentiation of FAPs, a process that could be hindered by FKBP5 knockdown or inhibition. Additionally, in vivo assessments confirmed FKBP5's role in adipogenesis., Conclusions: These insights into the pathogenesis of FIL underscore FKBP5 as a promising target for developing non-surgical interventions to manage the excessive adipose tissue growth in FIL., (© 2024. The Author(s).)

The FK506 Binding Protein (FKBP), ubiquitously present across diverse species, is characterized by its evolutionarily conserved FK506 binding domain (FKBd). In plants, evidence suggests that this gene family plays integral roles in regulating growth, development, and responses to environmental stresses. Notably, research on the identification and functionality of FKBP genes in rice remains limited. Therefore, this study utilized bioinformatic tools to identify 30 FKBP -encoding genes in rice. It provides a detailed analysis of their chromosomal locations, evolutionary relationships with the Arabidopsis thaliana FKBP family, and gene structures. Further analysis of the promoter elements of these rice FKBP genes revealed a high presence of stress-responsive elements. Quantitative PCR assays under drought and heat stress conditions demonstrated that genes OsFKBP15-2 , OsFKBP15-3 , OsFKBP16-3 , OsFKBP18 , and OsFKBP42b are inducible by these adverse conditions. These findings suggest a significant role for the rice FKBP gene family in stress adaptation. This research establishes a critical foundation for deeper explorations of the functional roles of the OsFKBP genes in rice.

Colorectal cancer (CRC) is a common and deadly tumor. FK506-binding protein 5 (FKBP5) is associated with some cancers, but the role of FKBP5 in CRC is not clear. The present study aimed to reveal the relationship between FKBP5 and CRC and to uncover the roles of FK506 in CRC. In total, 96 CRC patients were recruited. Survival analysis was conducted using the Kaplan-Meier method and COX regression analyses. Bioinformatics analyses were performed to explore the functions of FKBP5. The mechanisms of FKBP5 and the roles of FK506 in CRC progression were clarified by immunohistochemistry, MTS, scratch assay, transwell and flow cytometric analyses via in vitro and in vivo experiments. FKBP5 was overexpressed in 77 cancer tissues compared to that in matched normal tissues, and the overall survival rate of these patients was relatively shorter. Bioinformatics analyses showed that FKBP5 regulates proliferation, invasion, migration, epithelial-mesenchymal transition and nuclear factor-kappa B (NF-κB) signaling. The upregulation or downregulation of FKBP5 dramatically increases or decreases the proliferation, invasion and migration abilities of CRC cells. The expression of NF-κB, inhibitor B kinase α, matrix metalloproteinase-2 and metalloproteinase-9 positively correlated with FKBP5. FK506 inhibits the progression of CRC via the FKBP5/NF-κB signaling pathway. Our study identified a regulatory role for FKBP5 in CRC progression. Therefore, targeting FKBP5 may provide a novel treatment approach for CRC. FK506 can inhibit the progression of CRC by restraining the FKBP5/NF-κB signaling pathway and is expected to become a new drug for the treatment of CRC., (© 2024 Federation of European Biochemical Societies.)

Fear conditioning evokes a physiologic release of glucocorticoids that assists learning. As a cochaperone in the glucocorticoid receptor complex, FKBP51 modulates stress-induced glucocorticoid signaling and may influence conditioned fear responses. This study combines molecular and behavioral approaches to examine whether locally reducing FKBP51 expression in the ventral hippocampus is sufficient to affect fear-related behaviors. We hypothesized that reducing FKBP51 expression in the VH would increase glucocorticoid signaling to alter auditory fear conditioning. Adult male rats were injected with an adeno-associated virus (AAV) vector expressing short hairpin - RNAs (shRNA) targeting FKBP5 into the ventral hippocampus to reduce FKBP5 levels or a control AAV. Infusion of FKBP5-shRNA into the ventral hippocampus decreased auditory fear acquisition and recall. Although animals injected with FKBP5-shRNA showed less freezing during extinction recall, the difference was due to a reduced fear recall rather than improved extinction. Reducing ventral hippocampus FKBP51 did not affect exploratory behavior in either the open field test or the elevated zero maze test but did increase passive behavior in the forced swim test, suggesting that the reduction in auditory fear recall was not due to more active responses to acute stress. Furthermore, lower ventral hippocampus FKBP51 levels did not alter corticosterone release in response to restraint stress, suggesting that the reduced fear recall was not due to lower corticosterone release. Our findings suggest FKBP51 in the ventral hippocampus plays a selective role in modulating fear-learning processes and passive behavioral responses to acute stress rather than hypothalamic-pituitary-adrenal axis reactivity or exploratory responses.

Background: Ferroptosis was reported to possess the therapeutic potentials in various human cancers. In the present study, we explored the expression, clinical significance and the molecular mechanism of FK506 binding protein 3 (FKBP3) in the progression of lung adenocarcinoma (LUAD)., Material and Method: Cox regression was performed to obtain the prognosis related to differentially expressed genes (DEGs) in LUAD datasets from TCGA. We also downloaded the ferroptosis-related gene datasets from GeneCards. Venn diagram was performed to find the intersecting genes and FKBP3 was selected as the targeted gene by analyzing the diagnostic and prognostic values of Top10 intersecting genes. Moreover, univariate and multivariate analyses were performed to evaluate the association between clinicopathological factors and survival rates. GO/KEGG and GSEA analysis was performed to explore the function of FKBP3 in LUAD progression. Protein-protein interaction (PPI) network was performed via STRING database and the top10 hub genes were selected. Finally, the relationship between FKBP3 and immune infiltration was explored by ssGSEA analysis., Results: Firstly, 184 genes associated with the prognosis of LUAD and ferroptosis were obtained. FKBP3 was found to be significantly associated with a poor overall survival rate of LUAD patients. Immunohistochemical staining results showed that FKBP3 was highly located in cytoplasm and membrane of cells in LUAD tissues. PPI network analysis results showed that HDAC1, YY1, HDAC2, MTOR, PSMA3, PIN1, NCL, C14orf166, PIN4, and LARP6 were the top10 hub genes. Furthermore, spearman analysis results showed that the expression of FKBP3 was positively correlated with the abundance of Th2 cells and T helper cells., Conclusion: High level of FKBP3 was associated with poor prognostic outcomes of LUAD patients, which also inhibited immune infiltration in LUAD tissues. Additionally, FKBP3 was involved in regulating the ferroptosis process in LUAD patients. Thus, FKBP3 possessed the tumor promotion role might be involving in regulating ferroptosis and immune infiltration in LUAD progression., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

Molting and metamorphosis are important physiological processes in insects that are tightly controlled by ecdysone receptor (EcR) through the 20-hydroxyecdysone (20E) signaling pathway. EcR is a steroid nuclear receptor (SR). Several FK506-binding proteins (FKBPs) have been identified from the mammal SR complex, and are thought to be involved in the subcellular trafficking of SR. However, their roles in insects are poorly understood. To explore whether FKBPs are involved in insect molting or metamorphosis, we injected an FKBP inhibitor (FK506) into a lepidopteran insect, Spodoptera litura, and found that molting was inhibited in 61.11% of the larvae, and that the time for larvae to pupate was significantly extended. A total of 10 FKBP genes were identified from the genome of S. litura and were clustered into 2 distinct groups, according to their subcellular localization, with FKBP13 and FKBP14 belonging to the endoplasmic reticulum (ER) group and with the other members belonging to the cytoplasmic (Cy) group. All the CyFKBPs were significantly upregulated in the prepupal or pupal stages, with the opposite being observed for the ER group members. FK506 completely blocked the transfer of EcR to the nucleus under 20E induction, and significantly downregulated the transcriptional expression of many 20E signaling genes. A similar phenomenon was observed after RNA interference of 2 CyFKBPs (FKBP45 and FKBP12b), but not for FKBP13. Taken together, our data indicate that the cytoplasmic FKBPs, especially FKBP45 and FKBP12b, mediate the nuclear localization of EcR, thereby regulating the 20E signaling and ultimately affecting molting and metamorphosis in insects., (© 2023 Institute of Zoology, Chinese Academy of Sciences.)

Asthma has striking disparities across ancestral groups, but the molecular underpinning of these differences is poorly understood and minimally studied. A goal of the Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA) is to understand multi-omic signatures of asthma focusing on populations of African ancestry. RNASeq and DNA methylation data are generated from nasal epithelium including cases (current asthma, N = 253) and controls (never-asthma, N = 283) from 7 different geographic sites to identify differentially expressed genes (DEGs) and gene networks. We identify 389 DEGs; the top DEG, FN1, was downregulated in cases (q = 3.26 × 10 -9 ) and encodes fibronectin which plays a role in wound healing. The top three gene expression modules implicate networks related to immune response (CEACAM5; p = 9.62 × 10 -16 and CPA3; p = 2.39 × 10 -14 ) and wound healing (FN1; p = 7.63 × 10 -9 ). Multi-omic analysis identifies FKBP5, a co-chaperone of glucocorticoid receptor signaling known to be involved in drug response in asthma, where the association between nasal epithelium gene expression is likely regulated by methylation and is associated with increased use of inhaled corticosteroids. This work reveals molecular dysregulation on three axes - increased Th2 inflammation, decreased capacity for wound healing, and impaired drug response - that may play a critical role in asthma within the African Diaspora., (© 2024. The Author(s).)

FK506-binding protein 52 (FKBP52) is a member of the FKBP family of proline isomerases. FKBP52 is up-regulated in various cancers and functions as a positive regulator of steroid hormone receptors. Depletion of FKBP52 is known to inhibit cell proliferation; however, the detailed mechanism remains poorly understood. In this study, we found that FKBP52 depletion decreased MDM2 transcription, leading to stabilization of p53, and suppressed cell proliferation. We identified NFATc1 and NFATc3 as transcription factors that regulate MDM2 We also found that FKBP52 associated with NFATc3 and facilitated its nuclear translocation. In addition, calcineurin, a well-known Ca 2+ phosphatase essential for activation of NFAT, plays a role in MDM2 transcription. Supporting this notion, MDM2 expression was found to be regulated by intracellular Ca 2+ Taken together, these findings reveal a new role of FKBP52 in promoting cell proliferation via the NFAT-MDM2-p53 axis, and indicate that inhibition of FKBP52 could be a new therapeutic tool to activate p53 and inhibit cell proliferation., (© 2024 Hanaki et al.)

The primary treatment for glioblastoma (GBM) is removing the tumor mass as defined by MRI. However, MRI has limited diagnostic and predictive value. Tumor-associated macrophages (TAM) are abundant in GBM tumor microenvironment (TME) and are found in peripheral blood (PB). FKBP51 expression, with its canonical and spliced isoforms, is constitutive in immune cells and aberrant in GBM. Spliced FKBP51s supports M2 polarization. To find an immunologic signature that combined with MRI could advance in diagnosis, we immunophenotyped the macrophages of TME and PB from 37 patients with GBM using FKBP51s and classical M1-M2 markers. We also determined the tumor levels of FKBP51s, PD-L1, and HLA-DR. Tumors expressing FKBP51s showed an increase in various M2 phenotypes and regulatory T cells in PB, indicating immunosuppression. Tumors expressing FKBP51s also activated STAT3 and were associated with reduced survival. Correlative studies with MRI and tumor/macrophages cocultures allowed to interpret TAMs. Tumor volume correlated with M1 infiltration of TME. Cocultures with spheroids produced M1 polarization, suggesting that M1 macrophages may infiltrate alongside cancer stem cells. Cocultures of adherent cells developed the M2 phenotype CD163/FKBP51s expressing pSTAT6, a transcription factor enabling migration and invasion. In patients with recurrences, increased counts of CD163/FKBP51s monocyte/macrophages in PB correlated with callosal infiltration and were accompanied by a concomitant decrease in TME-infiltrating M1 macrophages. PB PD-L1/FKBP51s connoted necrotic tumors. In conclusion, FKBP51s identifies a GBM subtype that significantly impairs the immune system. Moreover, FKBP51s marks PB macrophages associated with MRI features of glioma malignancy that can aid in patient monitoring., Significance: Our research suggests that by combining imaging with analysis of monocyte/macrophage subsets in patients with GBM, we can enhance our understanding of the disease and assist in its treatment. We discovered a similarity in the macrophage composition between the TME and PB, and through association with imaging, we could interpret macrophages. In addition, we identified a predictive biomarker that drew more attention to immune suppression of patients with GBM., (© 2024 The Authors; Published by the American Association for Cancer Research.)

Antascomicin B is a natural product that similarly to the macrolides FK506 and Rapamycin binds to the FK506-binding protein 12 (FKBP12). FK506 and Rapamycin act as molecular glues by inducing ternary complexes between FKBPs and additional target proteins. Whether Antascomicin B can induce ternary complexes is unknown. Here we show that Antascomicin B binds tightly to larger human FKBP homologs. The cocrystal structure of FKBP51 in complex with Antascomicin B revealed that large parts of Antascomicin B are solvent-exposed and available to engage additional proteins. Cellular studies demonstrated that Antascomicin B enhances the interaction between human FKBP51 and human Akt. Our studies show that molecules with molecular glue-like properties are more prominent in nature than previously thought. We predict the existence of additional 'orphan' molecular glues that evolved to induce ternary protein complexes but where the relevant ternary complex partners are unknown., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Felix Hausch reports financial support was provided by Technical University of Darmstadt. Felix Hausch reports a relationship with Federal Ministry of Education and Research Berlin Office that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024. Published by Elsevier Ltd. All rights reserved.)

Stress is a common denominator of complex disorders and the FK-506 binding protein (FKBP)51 plays a central role in stress. Hence, it is not surprising that multiple studies imply the involvement of the FKBP51 protein and/or its coding gene, FKBP5 , in complex disorders. This review summarizes such reports concentrating on three disorder clusters-neuropsychiatric, cancer, and type 2 diabetes mellitus (T2DM). We also attempt to point to potential mechanisms suggested to mediate the effect of FKBP5 /FKBP51 on these disorders. Neuropsychiatric diseases considered in this paper include (i) Huntington's disease for which increased autophagic cellular clearance mechanisms related to decreased FKBP51 protein levels or activity is discussed, Alzheimer's disease for which increased FKBP51 activity has been shown to induce Tau phosphorylation and aggregation, and Parkinson's disease in the context of which FKBP12 is mentioned; and (ii) mental disorders, for which significant association with the single nucleotide polymorphism (SNP) rs1360780 of FKBP5 intron 7 along with decreased DNA methylation were revealed. Since cancer is a large group of diseases that can start in almost any organ or tissue of the body, FKBP51's role depends on the tissue type and differences among pathways expressed in those tumors. The FKBP51-heat-shock protein-(Hsp)90-p23 super-chaperone complex might function as an oncogene or as a tumor suppressor by downregulating the serine/threonine protein kinase (AKt) pathway. In T2DM, two potential pathways for the involvement of FKBP51 are highlighted as affecting the pathogenesis of the disease-the peroxisome proliferator-activated receptor-γ (PPARγ) and AKt.

Humanized mouse models can be used to explore human gene regulatory elements (REs), which frequently lie in non-coding and less conserved genomic regions. Epigenetic modifications of gene REs, also in the context of gene x environment interactions, have not yet been explored in humanized mouse models. We applied high-accuracy measurement of DNA methylation (DNAm) via targeted bisulfite sequencing (HAM-TBS) to investigate DNAm in three tissues/brain regions (blood, prefrontal cortex and hippocampus) of mice carrying the human FK506-binding protein 5 (FKBP5) gene, an important candidate gene associated with stress-related psychiatric disorders. We explored DNAm in three functional intronic glucocorticoid-responsive elements (at introns 2, 5, and 7) of FKBP5 at baseline, in cases of differing genotype (rs1360780 single nucleotide polymorphism), and following application of the synthetic glucocorticoid dexamethasone. We compared DNAm patterns in the humanized mouse (N = 58) to those in human peripheral blood (N = 447 and N = 89) and human postmortem brain prefrontal cortex (N = 86). Overall, DNAm patterns in the humanized mouse model seem to recapitulate DNAm patterns observed in human tissue. At baseline, this was to a higher extent in brain tissue. The animal model also recapitulated effects of dexamethasone on DNAm, especially in peripheral blood and to a lesser extent effects of genotype on DNAm. The humanized mouse model could thus assist in reverse translation of human findings in psychiatry that involve genetic and epigenetic regulation in non-coding elements., (© 2024. The Author(s).)

Fullerenes, particularly C 60 , exhibit unique properties that make them promising candidates for various applications, including drug delivery and nanomedicine. However, their interactions with biomolecules, especially proteins, remain not fully understood. This study implements both explicit and implicit C 60 models into the UNRES coarse-grained force field, enabling the investigation of fullerene-protein interactions without the need for restraints to stabilize protein structures. The UNRES force field offers computational efficiency, allowing for longer timescale simulations while maintaining accuracy. Five model proteins were studied: FK506 binding protein, HIV-1 protease, intestinal fatty acid binding protein, PCB-binding protein, and hen egg-white lysozyme. Molecular dynamics simulations were performed with and without C 60 to assess protein stability and investigate the impact of fullerene interactions. Analysis of contact probabilities reveals distinct interaction patterns for each protein. FK506 binding protein (1FKF) shows specific binding sites, while intestinal fatty acid binding protein (1ICN) and uteroglobin (1UTR) exhibit more generalized interactions. The explicit C 60 model shows good agreement with all-atom simulations in predicting protein flexibility, the position of C 60 in the binding pocket, and the estimation of effective binding energies. The integration of explicit and implicit C 60 models into the UNRES force field, coupled with recent advances in coarse-grained modeling and multiscale approaches, provides a powerful framework for investigating protein-nanoparticle interactions at biologically relevant scales without the need to use restraints stabilizing the protein, thus allowing for large conformational changes to occur. These computational tools, in synergy with experimental techniques, can aid in understanding the mechanisms and consequences of nanoparticle-biomolecule interactions, guiding the design of nanomaterials for biomedical applications.

The heat shock protein 90 kDa (Hsp90) molecular chaperone machinery is responsible for the folding and activation of hundreds of important clients such as kinases, steroid hormone receptors, transcription factors, etc. This process is dynamically regulated in an ATP-dependent manner by Hsp90 co-chaperones including a group of tetratricopeptide (TPR) motif proteins that bind to the C-terminus of Hsp90. Among these TPR containing co-chaperones, FK506-binding protein 51 kDa (FKBP51) is reported to play an important role in stress-related pathologies, psychiatric disorders, Alzheimer's disease, and cancer, making FKBP51-Hsp90 interaction a potential therapeutic target. In this study, we report identification of potent and selective inhibitors of FKBP51-Hsp90 protein-protein interaction using a structure-based virtual screening approach. Upon in vitro evaluation, the identified hits show a considerable degree of selectivity towards FKBP51 over other TPR proteins, particularly for highly homologous FKBP52. Tyr355 of FKBP51 emerged as an important contributor to inhibitor's specificity. Additionally, we demonstrate the impact of these inhibitors on cellular energy metabolism, and neurite outgrowth, which are subjects of FKBP51 regulation. Overall, the results from this study highlight a novel pharmacological approach towards regulation of FKBP51 function and more generally, Hsp90 function via its interaction with TPR co-chaperones., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Given the limitation of current routine approaches for pancreatic cancer screening and detection, the mortality rate of pancreatic cancer cases is still critical. The development of blood-based molecular biomarkers for pancreatic cancer screening and early detection which provide less-invasive, high-sensitivity, and cost-effective, is urgently needed. The goal of this study is to identify and validate the potential molecular biomarkers in white blood cells (WBCs) of pancreatic cancer patients. Gene expression profiles of pancreatic cancer patients from NCBI GEO database were analyzed by CU-DREAM. Then, mRNA expression levels of three candidate genes were determined by quantitative RT-PCR in WBCs of pancreatic cancer patients (N = 27) and healthy controls (N = 51). ROC analysis was performed to assess the performance of each candidate gene. A total of 29 upregulated genes were identified and three selected genes were performed gene expression analysis. Our results revealed high mRNA expression levels in WBCs of pancreatic cancer patients in all selected genes, including FKBP1A (p < 0.0001), PLD1 (p < 0.0001), and PSMA4 (p = 0.0002). Among candidate genes, FKBP1A mRNA expression level was remarkably increased in the pancreatic cancer samples and also in the early stage (p < 0.0001). Moreover, FKBP1A showed the greatest performance to discriminate patients with pancreatic cancer from healthy individuals than other genes with the 88.9% sensitivity, 84.3% specificity, and 90.1% accuracy. Our findings demonstrated that the alteration of FKBP1A gene in WBCs serves as a novel valuable biomarker for patients with pancreatic cancer. Detection of FKBP1A mRNA expression level in circulating WBCs, providing high-sensitive, less-invasive, and cost-effective, is simple and feasible for routine clinical setting that can be applied for pancreatic cancer screening and early detection., (© 2024. The Author(s).)

FK506-binding protein 51 kDa (FKBP51), encoded by Fkbp5 gene, gained considerable attention as an important regulator of several aspects of human biology including stress response, metabolic dysfunction, inflammation, and age-dependent neurodegeneration. Its catalytic peptidyl-prolyl isomerase (PPIase) activity is mediated by the N-terminal FK506-binding (FK1) domain, whereas the C-terminal tetratricopeptide motif (TPR) domain is responsible for FKBP51 interaction with molecular chaperone heat shock protein 90 (Hsp90). To understand FKBP51-related biology, several mouse models have been created. These include Fkbp5 complete and conditional knockouts, overexpression, and humanized models. To dissect the role of FKBP51-Hsp90 interaction in FKBP51 biology, we have created an interaction-deficient mouse (Fkbp5 TPRmut ) by introducing two-point mutations in the TPR domain of FKBP51. FKBP51-Hsp90 interaction-deficient mice are viable, fertile and show Mendelian inheritance. Intracellular association of FKBP51 with Hsp90 is significantly reduced in homozygous mutants compared to wild-type animals. No behavioral differences between genotypes were seen at 2 months of age, however, sex-dependent differences were detected in Y-maze and fear conditioning tests at the age of 12 months. Moreover, we have found a significant reduction in plasma levels of corticosterone and adrenocorticotropic hormone in Fkbp5 TPRmut mice after acute stress. In contrast to Fkbp5 knockout mice, females of Fkbp5 TPRmut showed increased body weight gain under high-fat diet treatment. Our data confirm the importance of FKBP51-Hsp90 interactions for stress-related endocrine signaling. Also, Fkbp5 TPRmut mice can serve as a useful in vivo tool to discriminate between Hsp90-dependent and independent functions of FKBP51., (© 2023. The Author(s).)

Purpose: Cell senescence stands as a principal risk factor for various neurodegenerative diseases, with astrocytic senescence emerging as a potentially pivotal player in the pathogenesis of aging and neurodegenerative disorders. Clearing senescent astrocytes holds promise as a potential therapeutic approach for senescence-related diseases., Methods: In this study, we designed and constructed two plasmids aimed at inducing apoptosis in senescent astrocytes. This was achieved through the ligation of FKBP (FK506-binding protein) and FRB (FKBP and FKBP rapamycin binding domain) and the formation of caspase8 dimers, thereby achieving the purpose of eliminating senescent astrocytes., Results: The developed vector system demonstrates a specifically capability to induce apoptosis in aging astrocytes, offering a targeted approach to eliminate these cells., Conclusion: The utilization of the double -inducible suicide gene system provides a versatile tool forstimulating cell apoptosis and inhibiting cellular senescence. This system proves valuable in exploring the intrinsic roles and molecular mechanisms of senescent cells in the occurrence and development of aging-related diseases. Ultimately, it offers a potential avenue for developing an efficient treatment system for such conditions., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Endometrial cancer (EC) is a common gynecological malignancy, and advanced-stage or recurrent EC is associated with a high mortality rate owing to the ineffectiveness of currently available treatments. FK506-binding protein 38 (FKBP38) is a member of the immunophilin family and inhibits melanoma and breast cancer cell metastasis. However, the functions of FKBP38 and its potential mechanism in EC remain unclear. Herein, we analyzed the expression levels of FKBP38 in EC cells and found that the FKBP38 expression was high in Ishikawa cells, and low in AN3CA cells, traditionally considered a low grade and a high grade cell line, respectively, in pathology classification. Moreover, FKBP38 inhibited cell proliferation, migration and invasion in EC cells, FKBP38 knockdown significantly promoted tumor growth of Ishikawa cells in a subcutaneous xenograft model and increased the number of lung metastases of Hec-1-A cells in a metastatic mouse model. Furthermore, FKBP38 suppressed several target proteins of epithelial-to-mesenchymal transition (EMT) and reduced the phosphorylation of ribosomal S6 protein (S6), eukaryotic initiation factor 4E-binding protein 1 (4EBP-1), indicating the potent inhibition of the mammalian target of rapamycin (mTOR) pathway. Meanwhile, the inhibition of mTOR neutralized the elevation of EC cell proliferation, migration and invasion after FKBP38 knockdown. In summary, FKBP38 would exert a tumor-suppressing role by modulating the mTOR pathway. Our results indicate that FKBP38 may be considered as a factor of EC metastasis and a new target for EC therapeutic intervention., Competing Interests: Declaration of competing interest The authors declare no potential conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Transcript stability is an important determinant of its abundance and, consequently, translational output. Transcript destabilisation can be rapid and is well suited for modulating the cellular response. However, it is unclear the extent to which RNA stability is altered under changing environmental conditions in plants. We previously hypothesised that recovery-induced transcript destabilisation facilitated a phenomenon of rapid recovery gene downregulation (RRGD) in Arabidopsis thaliana (Arabidopsis) following light stress, based on mathematical calculations to account for ongoing transcription. Here, we test this hypothesis and investigate processes regulating transcript abundance and fate by quantifying changes in transcription, stability and translation before, during and after light stress. We adapt syringe infiltration to apply a transcriptional inhibitor to soil-grown plants in combination with stress treatments. Compared with measurements in juvenile plants and cell culture, we find reduced stability across a range of transcripts encoding proteins involved in RNA binding and processing. We also observe light-induced destabilisation of transcripts, followed by their stabilisation during recovery. We propose that this destabilisation facilitates RRGD, possibly in combination with transcriptional shut-off that was confirmed for HSP101, ROF1 and GOLS1. We also show that translation remains highly dynamic over the course of light stress and recovery, with a bias towards transcript-specific increases in ribosome association, independent of changes in total transcript abundance, after 30 min of light stress. Taken together, we provide evidence for the combinatorial regulation of transcription and stability that occurs to coordinate translation during light stress and recovery in Arabidopsis., (© 2023 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Renal cell carcinoma (RCC) is one of the three major malignant tumors of the urinary system and originates from proximal tubular epithelial cells. Clear cell renal cell carcinoma (ccRCC) accounts for approximately 80% of RCC cases and is recognized as a metabolic disease driven by genetic mutations and epigenetic alterations. Through bioinformatic analysis, we found that FK506 binding protein 10 (FKBP10) may play an essential role in hypoxia and glycolysis pathways in ccRCC progression. Functionally, FKBP10 promotes the proliferation and metastasis of ccRCC in vivo and in vitro depending on its peptidyl-prolyl cis-trans isomerase (PPIase) domains. Mechanistically, FKBP10 binds directly to lactate dehydrogenase A (LDHA) through its C-terminal region, the key regulator of glycolysis, and enhances the LDHA-Y10 phosphorylation, which results in a hyperactive Warburg effect and the accumulation of histone lactylation. Moreover, HIFα negatively regulates the expression of FKBP10, and inhibition of FKBP10 enhances the antitumor effect of the HIF2α inhibitor PT2385. Therefore, our study demonstrates that FKBP10 promotes clear cell renal cell carcinoma progression and regulates sensitivity to HIF2α blockade by facilitating LDHA phosphorylation, which may be exploited for anticancer therapy., (© 2024. The Author(s).)

Diffuse large B-cell lymphoma (DLBCL) is difficult to treat due to the high recurrence rate and therapy intolerance, so finding potential therapeutic targets for DLBCL is critical. FK506-binding protein 3 (FKBP3) contributes to the progression of various cancers and is highly expressed in DLBCL, but the role of FKBP3 in DLBCL and its mechanism are not clear. Our study demonstrated that FKBP3 aggravated the proliferation and stemness of DLBCL cells, and tumour growth in a xenograft mouse model. The interaction between FKBP3 and parkinsonism associated deglycase (PARK7) in DB cells was found using co-immunoprecipitation assay. Knockdown of FKBP3 enhanced the degradation of PARK7 through increasing its ubiquitination modification. Forkhead Box O3 (FOXO3) belongs to the forkhead family of transcription factors and inhibits DLBCL, but the underlying mechanism has not been reported. We found that FOXO3 bound the promoter of FKBP3 and then suppressed its transcription, eventually weakening DLBCL. Mechanically, FKBP3 activated Wnt/β-catenin signalling pathway mediated by PARK7. Together, FKBP3 increased PARK7 and then facilitated the malignant phenotype of DLBCL through activating Wnt/β-catenin pathway. These results indicated that FKBP3 might be a potential therapeutic target for the treatment of DLBCL., (© 2023 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

GPX4 has attracted much attention as a key molecule of cell ferroptosis, but its role in cell apoptosis is rarely reported, and its role in apoptosis of thyroid cancer (TC) cell has not been reported. The analysis of TCGA database showed that both GPX4 and FKBP8 were highly expressed in TC tumor tissues; The expression of GPX4 and FKBP8 were positively correlated. The immunohistochemical analysis further confirmed that GPX4 and FKBP8 were highly expressed in TC tumor tissues. In addition, the high expression of GPX4 and FKBP8 were both significantly correlated with the poor prognosis of TC. Silencing GPX4 significantly inhibited the proliferation, induced apoptosis of TC cells, and reduced tumor growth in mice. The co-immunoprecipitation assay revealed a physical interaction between GPX4 and FKBP8 observed in the TC cells. Knockdown of FKBP8 significantly inhibited the proliferation and induced apoptosis of TC cells. Rescue experiments suggested that knockdown of FKBP8 could reverse the strengthens of cell proliferation and apoptosis and the higher expression of FKBP8 and Bcl-2 caused by overexpression of GPX4. Our results suggest that the GPX4/FKBP8/Bcl-2 axis promotes TC development by inhibiting TC cell apoptosis, which provides potential molecular targets for TC therapeutic strategies.

Chronic stress exposure during development can have lasting behavioral consequences that differ in males and females. More specifically, increased depressive behaviors in females, but not males, are observed in both humans and rodent models of chronic stress. Despite these known stress-induced outcomes, the molecular consequences of chronic adolescent stress in the adult brain are less clear. The stress hormone corticosterone activates the glucocorticoid receptor, and activity of the receptor is regulated through interactions with co-chaperones-such as the immunophilin FK506 binding proteins 5 (FKBP5). Previously, it has been reported that the adult stress response is modified by a history of chronic stress; therefore, the current study assessed the impact of chronic adolescent stress on the interactions of the glucocorticoid receptor (GR) with its regulatory co-chaperone FKBP5 in response to acute stress in adulthood. Although protein presence for FKBP5 did not differ by group, assessment of GR-FKBP5 interactions demonstrated that adult females with a history of chronic adolescent stress had elevated GR-FKBP5 interactions in the hippocampus following an acute stress challenge which could potentially contribute to a reduced translocation pattern given previous literature describing the impact of FKBP5 on GR activity. Interestingly, the altered co-chaperone interactions of the GR in the stressed female hippocampus were not coupled to an observable difference in transcription of GR-regulated genes. Together, these studies show that chronic adolescent stress causes lasting changes to co-chaperone interactions with the glucocorticoid receptor following stress exposure in adulthood and highlight the potential role that FKBP5 plays in these modifications. Understanding the long-term implications of adolescent stress exposure will provide a mechanistic framework to guide the development of interventions for adult disorders related to early life stress exposures.

Aims: Although hypothalamic-pituitary-adrenal (HPA) axis dysregulation in obsessive-compulsive disorder (OCD) has been reported, epigenetic changes in HPA axis-related genes have not been well studied in OCD. The present study investigated whether the epigenetic regulation of FK506-binding protein 51 gene (FKBP5) intron 7 is associated with OCD status in each sex. In addition, relationships among the DNA methylation levels of FKBP5 intron 7, OCD status and early-life trauma were explored., Methods: A total of 267 patients with OCD and 201 controls aged between 18 and 40 years were recruited. Demographic and clinical assessment, FKBP5 rs1360780 genotyping, and pyrosequencing of FKBP5 intron 7 were conducted. DNA was extracted from peripheral blood leucocytes. First, multivariate analysis of covariance for differential DNA methylation levels between OCD patients and controls was conducted with adjustment for FKBP5 rs1360780 genotype, early-life trauma, depressive symptoms, and age as covariates in each sex. Next, path analysis was conducted to determine the mediation effects of DNA methylation levels of FKBP5 between early-life trauma and OCD status. In addition, sensitivity analyses for medication and lifetime major depression were also performed., Results: DNA methylation at the FKBP5 intron 7 CpG site was significantly lower in men with OCD, compared to controls (mean difference -1.33%, 95% CI -2.11 to -0.55, p < 0.001). The results remained significant for drug naïve or free subjects (mean difference -1.27%, 95% CI -2.18 to -0.37, p = 0.006, in men) and for subjects without lifetime major depressive disorder (mean difference -1.60%, 95% CI -2.54 to -0.66, p < 0.001, in men). The mediation effect of DNA methylation levels was not significant between early-life trauma and OCD status., Conclusion: These findings suggest that epigenetic factors of HPA axis-related gene FKBP5 may play a role in the pathogenesis of OCD. Further studies are needed to determine how altered DNA methylation of FKBP5 intron 7 and HPA axis function are involved in OCD., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The Hsp90 co-chaperones FKBP51 and FKBP52 play key roles in steroid-hormone-receptor regulation, stress-related disorders, and sexual embryonic development. As a prominent target, glucocorticoid receptor (GR) signaling is repressed by FKBP51 and potentiated by FKBP52, but the underlying molecular mechanisms remain poorly understood. Here we present the architecture and functional annotation of FKBP51-, FKBP52-, and p23-containing Hsp90-apo-GR pre-activation complexes, trapped by systematic incorporation of photoreactive amino acids inside human cells. The identified crosslinking sites clustered in characteristic patterns, depended on Hsp90, and were disrupted by GR activation. GR binding to the FKBP FK1 , but not the FKBP FK2 , domain was modulated by FKBP ligands, explaining the lack of GR derepression by certain classes of FKBP ligands. Our findings show how FKBPs differentially interact with apo-GR, help to explain the differentiated pharmacology of FKBP51 ligands, and provide a structural basis for the development of improved FKBP ligands., (© 2023. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Hsp90 is an essential molecular chaperone responsible for the folding and activation of hundreds of 'client' proteins, including the glucocorticoid receptor (GR). Previously, we revealed that Hsp70 and Hsp90 remodel the conformation of GR to regulate ligand binding, aided by co-chaperones. In vivo, the co-chaperones FKBP51 and FKBP52 antagonistically regulate GR activity, but a molecular understanding is lacking. Here we present a 3.01 Å cryogenic electron microscopy structure of the human GR:Hsp90:FKBP52 complex, revealing how FKBP52 integrates into the GR chaperone cycle and directly binds to the active client, potentiating GR activity in vitro and in vivo. We also present a 3.23 Å cryogenic electron microscopy structure of the human GR:Hsp90:FKBP51 complex, revealing how FKBP51 competes with FKBP52 for GR:Hsp90 binding and demonstrating how FKBP51 can act as a potent antagonist to FKBP52. Altogether, we demonstrate how FKBP51 and FKBP52 integrate into the GR chaperone cycle to advance GR to the next stage of maturation., (© 2023. The Author(s).)

Although clinical reports have highlighted association of the deacetylase sirtuin 1 (SIRT1) gene with anxiety, its exact role in the pathogenesis of anxiety disorders remains unclear. The present study was designed to explore whether and how SIRT1 in the mouse bed nucleus of the stria terminalis (BNST), a key limbic hub region, regulates anxiety. In a chronic stress model to induce anxiety in male mice, we used site- and cell-type-specific in vivo and in vitro manipulations, protein analysis, electrophysiological and behavioral analysis, in vivo MiniScope calcium imaging and mass spectroscopy, to characterize possible mechanism underlying a novel anxiolytic role for SIRT1 in the BNST. Specifically, decreased SIRT1 in parallel with increased corticotropin-releasing factor (CRF) expression was found in the BNST of anxiety model mice, whereas pharmacological activation or local overexpression of SIRT1 in the BNST reversed chronic stress-induced anxiety-like behaviors, downregulated CRF upregulation, and normalized CRF neuronal hyperactivity. Mechanistically, SIRT1 enhanced glucocorticoid receptor (GR)-mediated CRF transcriptional repression through directly interacting with and deacetylating the GR co-chaperone FKBP5 to induce its dissociation from the GR, ultimately downregulating CRF. Together, this study unravels an important cellular and molecular mechanism highlighting an anxiolytic role for SIRT1 in the mouse BNST, which may open up new therapeutic avenues for treating stress-related anxiety disorders., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

FK506-binding protein 5 (FKBP5) contributes to many diseases; However, it remains unclear whether FKBP5 is relevant to recurrent spontaneous abortion (RSA) and the mechanisms by which it is involved in maternal-fetal immunological tolerance. Placental tissue was collected in women with normal pregnancy and RSA and examined for FKBP5 expression. Human trophoblast cell lines and THP-1-derived M0 macrophages were used to explore the role of FKBP5 in RSA and its mechanism. The role of FKBP5 on pregnancy outcomes was assessed using a mouse model of miscarriage. This study found that upregulation of FKBP5 at the placental interface is involved in the pathogenesis of RSA by depressing trophoblast function and promoting M1-type macrophage polarization. First, FKBP5 expression was upregulated in the villi of RSA, and FKBP5 regulated trophoblast function by inhibiting HAPLN1 expression through suppression of PI3K/AKT signaling. In addition, FKBP5 inhibited trophoblast IL-6 secretion by suppressing PI3K/AKT signaling, thereby promoting macrophage polarization toward the M1 phenotype. Meanwhile, FKBP5 was significantly elevated in decidual macrophages from patients with RSA and promoted M1 macrophage polarization via ROS/NF-κB signaling and further inhibited trophoblast function. Finally, FKBP5 inhibitors improved embryo resorption rate in miscarried mice. In conclusion, FKBP5 is essential in maintaining pregnancy and trophoblast-macrophage crosstalk in the maternal-fetal interface, which may be a potential target for diagnosing and treating RSA., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Mutations in the FKBP14 gene encoding the endoplasmic reticulum resident collagen-related proline isomerase FK506 binding protein 22 kDa (FKBP22) result in kyphoscoliotic Ehlers-Danlos Syndrome (EDS), which is characterized by a broad phenotypic outcome. A plausible explanation for this outcome is that FKBP22 participates in the biosynthesis of subsets of collagen types: FKBP22 selectively binds to collagens III, IV, VI, and X, but not to collagens I, II, V, and XI. However, these binding mechanisms have never been explored, and they may underpin EDS subtype heterogeneity. Here, we used collagen Toolkit peptide libraries to investigate binding specificity. We observed that FKBP22 binding was distributed along the collagen helix. Further, it (1) was higher on collagen III than collagen II peptides and it (2) was correlated with a positive peptide charge. These findings begin to elucidate the mechanism by which FKBP22 interacts with collagen.

Successful muscle regeneration following injury is essential for functional homeostasis of skeletal muscles. Krüppel-like factor 15 (KLF15) is a metabolic transcriptional regulator in the muscles. However, little is known regarding its function in muscle regeneration. Here, we examined microarray datasets from the Gene Expression Omnibus database, which indicated downregulated KLF15 in muscles from patients with various muscle diseases. Additionally, we found that Klf15 knockout (Klf15KO) impaired muscle regeneration following injury in mice. Furthermore, KLF15 expression was robustly induced during myoblast differentiation. Myoblasts with KLF15 deficiency showed a marked reduction in their fusion capacity. Unbiased transcriptome analysis of muscles on day 7 postinjury revealed downregulated genes involved in cell differentiation and metabolic processes in Klf15KO muscles. The FK506-binding protein 51 (FKBP5), a positive regulator of myoblast differentiation, was ranked as one of the most strongly downregulated genes in the Klf15KO group. A mechanistic search revealed that KLF15 binds directly to the promoter region of FKBP5 and activates FKBP5 expression. Local delivery of FKBP5 rescued the impaired muscle regeneration in Klf15KO mice. Our findings reveal a positive regulatory role of KLF15 in myoblast differentiation and muscle regeneration by activating FKBP5 expression. KLF15 signaling may be a novel therapeutic target for muscle disorders associated with injuries or diseases., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Members of the FK506-binding protein (FKBP) family regulate a range of important physiological processes. Unfortunately, current therapeutics such as FK506 and rapamycin exhibit only modest selectivity among these functionally distinct proteins. Recent progress in developing selective inhibitors has been reported for FKBP51 and FKBP52, which act as mutual antagonists in the regulation of steroid hormone signaling. Two structurally similar inhibitors yield distinct protein conformations at the binding site. Localized conformational transition in the binding site of the unliganded FK1 domain of FKBP51 is suppressed by a K58T mutation that also suppresses the binding of these inhibitors. Here, it is shown that the changes in amide hydrogen exchange kinetics arising from this K58T substitution are largely localized to this structural region. Accurate determination of the hydroxide-catalyzed exchange rate constants in both the wildtype and K58T variant proteins impose strong constraints upon the pattern of amide exchange reactivities within either a single or a pair of transient conformations that could give rise to the differences between these two sets of measured rate constants. Poisson-Boltzmann continuum dielectric calculations provide moderately accurate predictions of the structure-dependent hydrogen exchange reactivity for solvent-exposed protein backbone amides. Applying such calculations to the local protein conformations observed in the two inhibitor-bound FKBP51 domains demonstrated that the experimentally determined exchange rate constants for the wildtype domain are robustly predicted by a population-weighted sum of the experimental hydrogen exchange reactivity of the K58T variant and the predicted exchange reactivities in model conformations derived from the two inhibitor-bound protein structures., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

FKBP10, a member of the FK506-binding protein (FKBP) family, has been implicated in cancer development, although its prognostic function remains controversial. In this study, we analyzed the expression of FKBP10 in tumor tissues using online databases (TCGA) as well as our CRC cohort, and investigated the relationship between its subcellular expression pattern and patient outcomes. Cox regression analysis was used to determine the associations between different subcellular expression patterns of FKBP10 and clinical features of patients. We also discussed the expression level of FKBP10 based on different subcellular expression patterns. Our results showed that FKBP10 was significantly elevated in CRC tissues and exhibited three different subcellular expression patterns which were defined as 'FKBP10-C' (concentrated), 'FKBP10-T' (transitional) and 'FKBP10-D' (dispersive). The FKBP10-D expression pattern was only found in tumor tissues and was associated with unfavorable disease-free survival in CRC patients. High expression levels of FKBP10-C predicted an unfavorable prognosis of recurrence of CRC, while FKBP10-D did not. Our findings suggest that the subcellular expression patterns and expression level of FKBP10 play crucial prognostic roles in CRC, which revealed that FKBP10 may be a viable prognostic and therapeutic target for the diagnosis and treatment of CRC.

Using a zebrafish ionocyte model, transcriptomics and genetic analyses were performed to identify pathways and genes involved in cell quiescence-proliferation regulation. Gene ontology and Kyoto encyclopedia of genes and genomes pathway analyses revealed that genes involved in transcription regulation, cell cycle, Foxo signalling and Wnt signalling pathway are enriched among the up-regulated genes while those involved in ion transport, cell adhesion and oxidation-reduction are enriched among the down-regulated genes. Among the top up-regulated genes is FK506-binding protein 5 (Fkbp5). Genetic deletion and pharmacological inhibition of Fkbp5 abolished ionocyte reactivation and impaired Akt signalling. Forced expression of a constitutively active form of Akt rescued the defects caused by Fkbp5 inhibition. These results uncover a key role of Fbkp5 in regulating the quiescence-proliferation decision via Akt signalling., (© 2023 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Post-traumatic stress disorder (PTSD) leads to enhanced alcohol drinking and development of alcohol use disorder (AUD). Identifying shared neural mechanisms might help discover new therapies for PTSD/AUD. Here, we employed a rat model of comorbid PTSD/AUD to evaluate compounds that inhibit FK506-binding protein 51 (FKBP5), a co-chaperone modulator of glucocorticoid receptors implicated in stress-related disorders. Male and female rats received a familiar avoidance-based shock stress followed by voluntary alcohol drinking. We then assessed trauma-related behaviors through sleep bout cycles, hyperarousal, fear overgeneralization, and irritability. To evaluate the role of stress and alcohol history on the sensitivity to FKBP5 inhibitors, in two separate studies, we administered two FKBP5 inhibitors, benztropine (Study 1) or SAFit2 (Study 2). FKBP5 inhibitors were administered on the last alcohol drinking session and prior to each trauma-related behavioral assessment. We also measured plasma corticosterone to assess the actions of FKBP5 inhibitors after familiar shock stress and alcohol drinking. Benztropine reduced alcohol preference in stressed males and females, while aggressive bouts were reduced in benztropine-treated stressed females. During hyperarousal, benztropine reduced several startle response outcomes across stressed males and females. Corticosterone was reduced in benztropine-treated stressed males. The selective FKBP5 inhibitor, SAFit2, reduced alcohol drinking in stressed males but not females, with no differences in irritability. Importantly, SAFit2 decreased fear overgeneralization in stressed males and females. SAFit2 also reduced corticosterone across stressed males and females. Neither FKBP5 inhibitor changed sleep bout structure. These findings indicate that FKBP5 inhibitors modulate stress-related alcohol drinking and partially modulate trauma-related behaviors. This work supports the hypothesis that targeting FKBP5 may alleviate PTSD/AUD comorbidity., (© 2022. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Stress-induced hyperalgesia is a health-threatening condition that lacks effective therapeutic intervention, impairing the quality of life. Interestingly, a high prevalence of corneal pain symptoms was also found in patients experienced severe stressors. Excessive secretion corticosterone in rodents has been shown to contribute to the development of visceral and mechanical hyperalgesia under stressful conditions. The co-chaperone protein FK506-binding protein 5 (FKBP5) was reported to modulate steroid sensitivity and inhibition of FKBP51 possessed anxiolytic and anti-hyperalgesic in the stressed-mice model. However, whether corticosterone and FKBP5 play a role in chronic stress-induced corneal hyperalgesia remains unknown. The aim of this study was to evaluate the corneal sensitivity after exposure to chronic restraint stress (CRS) and investigate the potential role of corticosterone and FKBP5 mediated proinflammatory cytokines release in trigeminal ganglion (TG) in corneal hyperalgesia under chronic stressful situations. Firstly, mice displayed increased corneal sensitivity without changes in tear production and corneal injury after CRS for 4 hours/day for 14 days. Meanwhile, corticosterone deficiency via adrenalectomy could prevent CRS-induced corneal hyperalgesia, whereas chronic corticosterone feeding increased the corneal sensitivity accompanied by increasing proinflammatory cytokines levels of phospho-NF-κB (p-NF-κB), tumor necrosis factor (TNF)-α and interleukin (IL)-1β in the TG on d14. Notably, we found that FKBP51 was significantly upregulated in the TG in the stressed-mice. Intraperitoneal injection of FKBP51 inhibitor significantly alleviated CRS-induced corneal hyperalgesia, and reversed calcitonin gene related peptide (CGRP) increase and proinflammatory cytokines production in the TG. Moreover, FKBP51 inhibitor could also exert its anti-hyperalgesic effect on corneal pain through intra-TG injection. Our study proves that CRS can induce corneal hyperalgesia in mice and uncovers the role of corticosterone and FKBP51 in modulating corneal sensitivity, providing a novel treatment strategy for stress-induced corneal hyperalgesia. AVAILABILITY OF DATA AND MATERIALS: All data and additional file are available upon request from the corresponding author., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2023. Published by Elsevier Ltd.)

FK506 binding protein 52 (FKBP52) (gene name FKBP4) is a 52 kDa protein that belongs to the FKBP family; it binds to the immunosuppressant FK506 and has proline isomerase activity. In addition to its FK domain-containing peptidylprolyl isomerase activity, FKBP52 also acts as a cochaperone through the tetratricopeptide repeat domain that mediates binding to heat shock protein 90. Previous studies have reported that FKBP52 is associated with hormone-dependent, stress-related, and neurodegenerative diseases, revealing its diverse functions. In particular, the effects of FKBP52 on cancer have attracted considerable attention. FKBP52 promotes the growth of hormone-dependent cancers by activating steroid hormone receptors. Recent studies have shown that the expression of FKBP52 is increased not only in steroid hormone-dependent cancer cells but also in colorectal, lung, and liver cancers, revealing its diverse functions that contribute to cancer growth. This review summarizes reports related to hormone-dependent cancer and cell proliferation in terms of the structure of FKBP52 and its function on interacting molecules., (© 2023 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)

Scaffold proteins are crucial regulators of signaling networks, and their abnormal expression may favor the development of tumors. Among the scaffold proteins, immunophilin covers a unique role as 'protein-philin' (Greek 'philin' = friend) that interacts with proteins to guide their proper assembly. The growing list of human syndromes associated with the immunophilin defect underscores the biological relevance of these proteins that are largely opportunistically exploited by cancer cells to support and enable the tumor's intrinsic properties. Among the members of the immunophilin family, the FKBP5 gene was the only one identified to have a splicing variant. Cancer cells impose unique demands on the splicing machinery, thus acquiring a particular susceptibility to splicing inhibitors. This review article aims to overview the current knowledge of the FKBP5 gene functions in human cancer, illustrating how cancer cells exploit the scaffolding function of canonical FKBP51 to foster signaling networks that support their intrinsic tumor properties and the spliced FKBP51s to gain the capacity to evade the immune system., Competing Interests: The authors declare that they have no conflicts of interest to report regarding the present study., (© 2023 Marrone et al.)

Background : Solute Carrier Family 3 Member 2 (SLC3A2) is a member of the solute carrier family that plays pivotal roles in regulation of intracellular calcium levels and transports L-type amino acids. However, there are insufficient scientific researches on the prognostic and immunological roles of SLC3A2 in breast cancer (BC) and whether everolimus regulates novel SLC3A2 related molecular mechanism in the immuno-oncology context of the tumor microenvironment (TME), therefore, we see a necessity to conduct the current in silico and biological experimental study. Methods : Using diverse online databases, we investigated the role of SLC3A2 in therapy response, clinicopathological characteristics, tumor immune infiltration, genetic alteration, methylation and single cell sequencing in BC. WB, Co-IP, cell proliferation assay, Edu staining, ROS and GSH assay and in vivo tumor xenograft assays were performed to verify FKBP1A/SLC3A2 axis in everolimus inducing ferroptosis of breast cancer. Co-cultures and IL-9 ELISA were performed to demonstrate the T lymphocyte function. Results : We demonstrated that SLC3A2 was aberrantly expressed among various BC cohorts. Our results also suggested that SLC3A2 expression was associated with chemotherapeutic outcome in BC patients. Our results further indicated that SLC3A2 was associated with tumor infiltration of cytotoxic T cell but not other immune cells among BC TME. The alterations in SLC3A2 gene had a significant correlation to relapse free survival and contributed a significant impact on BC tumor mutational burden. Finally, SLC3A2 was illustrated to be expressed in diverse BC cellular populations at single cell level, and negatively linked to angiogenesis, inflammation and quiescence, but positively correlated with other functional phenotypes. Noteworthily, everolimus (a targeted therapy drug for BC) related protein, FK506-binding protein 1A (FKBP1A) was found to bind with SLC3A2, and negatively regulated SLC3A2 expression during the processes of everolimus inducing ferroptosis of BC cells and promoting anti-proliferation of Th9 lymphocytes. Conclusions : Altogether, our study strongly implies that SLC3A2 is an immuno-oncogenic factor and FKBP1A/SLC3A2 axis would provide insights for a novel immunotherapy approach for the treatment of BC in the context of TME., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Single-molecule data are of great significance in biology, chemistry, and medicine. However, new experimental tools to characterize, in a multiplexed manner, protein bond rupture under force are still needed. Acoustic force spectroscopy is an emerging manipulation technique which generates acoustic waves to apply force in parallel on multiple microbeads tethered to a surface. We here exploit this configuration in combination with the recently developed modular junctured-DNA scaffold that has been designed to study protein-protein interactions at the single-molecule level. By applying repetitive constant force steps on the FKBP12-rapamycin-FRB complex, we measure its unbinding kinetics under force at the single-bond level. Special efforts are made in analyzing the data to identify potential pitfalls. We propose a calibration method allowing in situ force determination during the course of the unbinding measurement. We compare our results with well-established techniques, such as magnetic tweezers, to ensure their accuracy. We also apply our strategy to study the force-dependent rupture of a single-domain antibody with its antigen. Overall, we get a good agreement with the published parameters that have been obtained at zero force and population level. Thus, our technique offers single-molecule precision for multiplexed measurements of interactions of biotechnological and medical interest., Competing Interests: Declaration of interests PSL valorisation has submitted a patent related to the J-DNA (PCT FR2018/053533) with D.K., T.S., and C.G. among the inventors., (Copyright © 2023 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Mental health disorders often arise as a combination of environmental and genetic factors. The FKBP5 gene, encoding the GR co-chaperone FKBP51, has been uncovered as a key genetic risk factor for stress-related illness. However, the exact cell type and region-specific mechanisms by which FKBP51 contributes to stress resilience or susceptibility processes remain to be unravelled. FKBP51 functionality is known to interact with the environmental risk factors age and sex, but so far data on behavioral, structural, and molecular consequences of these interactions are still largely unknown. Here we report the cell type- and sex-specific contribution of FKBP51 to stress susceptibility and resilience mechanisms under the high-risk environmental conditions of an older age, by using two conditional knockout models within glutamatergic ( Fkbp5 Nex ) and GABAergic ( Fkbp5 Dlx ) neurons of the forebrain. Specific manipulation of Fkbp51 in these two cell types led to opposing effects on behavior, brain structure and gene expression profiles in a highly sex-dependent fashion. The results emphasize the role of FKBP51 as a key player in stress-related illness and the need for more targeted and sex-specific treatment strategies.

Efficient delivery of functional factors into target cells remains challenging. Although extracellular vesicles (EVs) are considered to be potential therapeutic delivery vehicles, a variety of efficient therapeutic delivery tools are still needed for cancer cells. Herein, we demonstrated a promising method to deliver EVs to refractory cancer cells via a small molecule-induced trafficking system. We generated an inducible interaction system between the FKBP12-rapamycin-binding protein (FRB) domain and FK506 binding protein (FKBP) to deliver specific cargo to EVs. CD9, an abundant protein in EVs, was fused to the FRB domain, and the specific cargo to be delivered was linked to FKBP. Rapamycin recruited validated cargo to EVs through protein-protein interactions (PPIs), such as the FKBP-FRB interaction system. The released EVs were functionally delivered to refractory cancer cells, triple negative breast cancer cells, non-small cell lung cancer cells, and pancreatic cancer cells. Therefore, the functional delivery system driven by reversible PPIs may provide new possibilities for a therapeutic cure against refractory cancers.

Objective: Intestinal barrier loss is a Crohn's disease (CD) risk factor. This may be related to increased expression and enzymatic activation of myosin light chain kinase 1 (MLCK1), which increases intestinal paracellular permeability and correlates with CD severity. Moreover, preclinical studies have shown that MLCK1 recruitment to cell junctions is required for tumour necrosis factor (TNF)-induced barrier loss as well as experimental inflammatory bowel disease progression. We sought to define mechanisms of MLCK1 recruitment and to target this process pharmacologically., Design: Protein interactions between FK506 binding protein 8 (FKBP8) and MLCK1 were assessed in vitro. Transgenic and knockout intestinal epithelial cell lines, human intestinal organoids, and mice were used as preclinical models. Discoveries were validated in biopsies from patients with CD and control subjects., Results: MLCK1 interacted specifically with the tacrolimus-binding FKBP8 PPI domain. Knockout or dominant negative FKBP8 expression prevented TNF-induced MLCK1 recruitment and barrier loss in vitro. MLCK1-FKBP8 binding was blocked by tacrolimus, which reversed TNF-induced MLCK1-FKBP8 interactions, MLCK1 recruitment and barrier loss in vitro and in vivo. Biopsies of patient with CD demonstrated increased numbers of MLCK1-FKBP8 interactions at intercellular junctions relative to control subjects., Conclusion: Binding to FKBP8, which can be blocked by tacrolimus, is required for MLCK1 recruitment to intercellular junctions and downstream events leading to immune-mediated barrier loss. The observed increases in MLCK1 activity, MLCK1 localisation at cell junctions and perijunctional MLCK1-FKBP8 interactions in CD suggest that targeting this process may be therapeutic in human disease. These new insights into mechanisms of disease-associated barrier loss provide a critical foundation for therapeutic exploitation of FKBP8-MLCK1 interactions., Competing Interests: Competing interests: WVG is a founder, shareholder and employee of Thelium Therapeutics. JRT is a founder and shareholder of Thelium Therapeutics and has served as a consultant for Entrinsic, Immunic, and Kallyope., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)