Steroid Receptor Function Research Articles

Abstract P140: Impact Of Ovariectomy On Aldosterone And Blood Pressure In Lysine-Specific Demethylase 1 (LSD1) Deficient Mice

LSD1 regulates steroid receptor function including estrogen and mineralocorticoid receptor. Women of African descent who carry the LSD1 risk allele rs587168 develop salt-sensitive hypertension and aldosterone (ALDO) dysregulation. This phenotype is observed in women above the age of 50 but not below the age of 50, which raises the question whether ovarian function affects the relationship between blood pressure (BP) and LSD1. Therefore, we hypothesized that ovariectomized (OVX) LSD1 +/– female mice will exhibit higher systolic BP (SBP) on liberal salt (LibS) diet as compared to intact LSD1 +/– female littermates. OVX was performed at 40 weeks of age, animals were fully acclimated to tail-cuff BP measurements, and BP was assessed on a LibS diet (1.6% NaCl Purina Chow) at 65 weeks of age, followed by euthanasia of animals and tissue collection. OVX females exhibited lower uterine weight (OVX LSD1 +/– 0.1 ± 0.03 g vs intact LSD1 +/– 0.2 ± 0.02 g, P =0.013) demonstrating OVX was successful. On a LibS diet, 24-h urinary Na + was similar between groups (OVX LSD1 +/– 0.37 ± 0.07 mEq vs intact LSD1 +/– 0.42 ± 0.09 mEq, P =0.678). OVX females exhibited higher SBP (OVX LSD1 +/– 121.5 ± 4.1 mmHg vs intact LSD1 +/– 107.8 ± 4.4 mmHg, P =0.033). 24-h urinary ALDO corrected for urinary creatinine was lower (OVX LSD1 +/– 29.2 ± 2.0 pg/mcg vs intact LSD1 +/– 59.8 ± 7.6 pg/mcg, P <0.001), consistent with a volume expanded state. In Conclusion, OVX increased BP in LSD1 +/- mice, likely related to a mineralocorticoid receptor-mediated volume expansion. This raises the possibility that the reason younger women (<50 years) with LSD1 risk allele do not have salt-sensitive BP is related to ovarian hormones.

Structure and function of the TPR-domain immunophilins FKBP51 and FKBP52 in normal physiology and disease.

Coordinated cochaperone interactions with Hsp90 and associated client proteins are crucial for a multitude of signaling pathways in normal physiology, as well as in disease settings. Research on the molecular mechanisms regulated by the Hsp90 multiprotein complexes has demonstrated increasingly diverse roles for cochaperones throughout Hsp90-regulated signaling pathways. Thus, the Hsp90-associated cochaperones have emerged as attractive therapeutic targets in a wide variety of disease settings. The tetratricopeptide repeat(TPR)-domain immunophilins FKBP51 and FKBP52 are of special interest among the Hsp90-associated cochaperones given their Hsp90 client protein specificity, ubiquitous expression across tissues, and their increasingly important roles in neuronal signaling, intracellular calcium release, peptide bond isomerization, viral replication, steroid hormone receptor function, and cell proliferation to name a few. This review summarizes the current knowledge of the structure and molecular functions of TPR-domain immunophilins FKBP51 and FKBP52, recent findings implicating these immunophilins in disease, and the therapeutic potential of targeting FKBP51 and FKBP52 for the treatment of disease.

Abstract 5728: A druggable FOXA1-glucocorticoid receptor transcriptional axis drives tumor growth in NSCLC

Abstract FOXA1 is a pioneer factor that is essential to steroid receptor function in hormone-dependent adenocarcinomas, including breast and prostate cancer. FOXA1 expression is also observed in other tumors of epithelial lineage such as non-small cell lung cancer (NSCLC), but whether and how it is required for tumor growth in these contexts is not known. Analyzing data from genome-scaled pooled loss-of-function screens, we identified and validated a subset of NSCLC cell lines with reduced cellular fitness following FOXA1 knockout. We performed a rapid immunoprecipitation and mass spectrometry of endogenous proteins (RIME) screen to nominate candidate factors that may cooperate with FOXA1 to mediate oncogenic transcription programs. This screen revealed a chromatin-localized interaction between FOXA1 and the glucocorticoid receptor (GR). Depletion of GR expression using shRNA or CRISPR/Cas9 suppressed the proliferation of FOXA1-dependent, but not FOXA1-independent NSCLC models, suggesting GR specifically contributes to tumor growth in the FOXA1-dependent context. To assess the potential therapeutic utility of targeting the FOXA1-GR signaling axis, we employed two structurally distinct ligand antagonists of GR from ORIC Pharmaceuticals: ORIC-101, a steroidal antagonist, and OP-4954, a non-steroidal antagonist. Both antagonists inhibited dexamethasone stimulated GR-transactivation of a glucocorticoid response element (GRE)-luciferase reporter with equal potency. However, proliferation and colony formation of the FOXA1/GR-dependent NSCLC cells were only inhibited upon treatment with ORIC-101, and not OP-4954. Gene expression analysis uncovered a discrete set of GR target genes, including SFTPB, TRAF4 and SGK1, whose expression was reduced by ORIC-101 but unaffected or even induced by OP-4954. The specific inhibition of GR target gene expression and attendant induction of apoptosis by ORIC-101 suggest a hierarchy of GR targets relevant to the FOXA1/GR-growth program in NSCLC. Finally, we evaluated the in vivo therapeutic potential of ORIC-101 using NSCLC xenografts and found that single-agent ORIC-101 exhibited potent antitumor effects in these models. Taken together, these data establish a model of FOXA1-GR-dependent tumor growth amongst a subset of NSCLCs and demonstrate that effective blockade of this complex is a rational therapeutic avenue to be explored in the clinic. Citation Format: Madeline Dorso. A druggable FOXA1-glucocorticoid receptor transcriptional axis drives tumor growth in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5728.

Heat shock proteins exhibit distinct spatiotemporal expression patterns in the domestic cat (Felis catus) ovary during the oestrous cycle.

Heat shock proteins (HSP) are significant regulators of cell proliferation, differentiation and apoptosis. HSP participate in ovarian physiology through proliferative and apoptotic mechanisms and the modulation of sex steroid receptor functions. We investigated whether the expression and localisation patterns of HSP in the domestic cat ovary vary with the oestrous cycle stage. Immunohistochemical analysis revealed cell type-specific localisation patterns of HSPD1/HSP60, HSPA/HSP70, HSPC/HSP90 and HSPH/HSP105 in several ovarian cells of the domestic cat, including oocytes, follicular (granulosa and theca cells) and luteal cells, stromal and thecal interstitial cells, stromal cells, and vascular endothelial and smooth muscle cells during the anoestrous, follicular and luteal phases of the oestrous cycle. Western blot results showed that the expression of three HSP (HSPD1/HSP60, HSPA/HSP70 and HSPH/HSP105) varied with the oestrous cycle stage. While the maximal expression of HSPD1/HSP60 and HSPH/HSP105 occurred during the luteal phase, the expression of HSPA/HSP70 was minimal. The expressions of HSPA/HSP70 and HSPH/HSP105 were low during the follicular phase compared to the anoestrous phase. In conclusion, the alterations that occur in the expression of HSP in the domestic cat ovary during the different stages of the oestrous cycle imply that these proteins participate in the regulation of ovarian function under different physiological conditions.

Systematic analysis of the pharmacological function of Schisandra as a potential exercise supplement.

[Purpose] Exercise can prevent conditions such as atrophy and degenerative brain diseases. However, owing to individual differences in athletic ability, exercise supplements can be used to improve a person’s exercise capacity. Schisandra chinensis (SC) is a natural product with various physiologically active effects. In this study, we analyzed SC using a pharmacological network and determined whether it could be used as an exercise supplement.[Methods] The active compounds of SC and target genes were identified using the Traditional Chinese Medicine Database and Analysis Platform (TCMSP). The active compound and target genes were selected based on pharmacokinetic (PK) conditions (oral bioavailability (OB) ≥ 30%, Caco-2 permeability (Caco-2) ≥ -0.4, and drug-likeness (DL) ≥ 0.18). Gene ontology (GO) was analyzed using the Cytoscape software.[Results] Eight active compounds were identified according to the PK conditions. Twenty-one target genes were identified after excluding duplicates in the eight active compounds. The top 10 GOs were analyzed using GO-biological process analysis. GO was subsequently divided into three representative categories: postsynaptic neurotransmitter receptor activity (53.85%), an intracellular steroid hormone receptor signaling pathway (36.46%), and endopeptidase activity (10%). SC is related to immune function.[Conclusion] According to the GO analysis, SC plays a role in immunity and inflammation, promotes liver metabolism, improves fatigue, and regulates the function of steroid receptors. Therefore, we suggest SC as an exercise supplement with nutritional and anti-fatigue benefits.

Bisphenol A Analogues Suppress Spheroid Attachment on Human Endometrial Epithelial Cells through Modulation of Steroid Hormone Receptors Signaling Pathway

Bisphenol A (BPA) is a well-known endocrine disruptor, widely used in various consumer products and ubiquitously found in air, water, food, dust, and sewage leachates. Recently, several countries have restricted the use of BPA and replaced them with bisphenol S (BPS) and bisphenol F (BPF), which have a similar chemical structure to BPA. Compared to BPA, both BPS and BPF have weaker estrogenic effects, but their effects on human reproductive function including endometrial receptivity and embryo implantation still remain largely unknown. We used an in vitro spheroid (blastocyst surrogate) co-culture assay to investigate the effects of BPA, BPS, and BPF on spheroid attachment on human endometrial epithelial cells, and further delineated their role on steroid hormone receptor expression. We also used transcriptomics to investigate the effects of BPA, BPS, and BPF on the transcriptome of human endometrial cells. We found that bisphenol treatment in human endometrial Ishikawa cells altered estrogen receptor alpha (ERα) signaling and upregulated progesterone receptors (PR). Bisphenols suppressed spheroid attachment onto Ishikawa cells, which was reversed by the downregulation of PR through PR siRNA. Overall, we found that bisphenol compounds can affect human endometrial epithelial cell receptivity through the modulation of steroid hormone receptor function leading to impaired embryo implantation.

Steroid Receptors in Breast Cancer: Understanding of Molecular Function as a Basis for Effective Therapy Development.

Simple SummaryThe knowledge we currently possess on the molecular function of steroid receptors in breast cancer is incredibly vast. New research in the field is constantly emerging, including studies focusing on potential therapeutic application of steroid receptors other than estrogen receptor which already serves as a crucial therapy target. Therefore we believe that it is necessary to regularly summarize the data on this topic. The aim of this review is to provide breast cancer researchers with a clear explanation of the complex nature of steroid receptor function, including the most up-to-date information, in order to support the effective development of future hormone therapies.Breast cancer remains one of the most important health problems worldwide. The family of steroid receptors (SRs), which comprise estrogen (ER), progesterone (PR), androgen (AR), glucocorticoid (GR) and mineralocorticoid (MR) receptors, along with a receptor for a secosteroid—vitamin D, play a crucial role in the pathogenesis of the disease. They function predominantly as nuclear receptors to regulate gene expression, however, their full spectrum of action reaches far beyond this basic mechanism. SRs are involved in a vast variety of interactions with other proteins, including extensive crosstalk with each other. How they affect the biology of a breast cell depends on such factors as post-translational modifications, expression of coregulators, or which SR isoform is predominantly synthesized in a given cellular context. Although ER has been successfully utilized as a breast cancer therapy target for years, research on therapeutic application of other SRs is still ongoing. Designing effective hormone therapies requires thorough understanding of the molecular function of the SRs. Over the past decades, huge amount of data was obtained in multiple studies exploring this field, therefore in this review we attempt to summarize the current knowledge in a comprehensive way.

How Protein Methylation Regulates Steroid Receptor Function.

Steroid receptors (SRs) are members of the nuclear hormonal receptor family, many of which are transcription factors regulated by ligand binding. SRs regulate various human physiological functions essential for maintenance of vital biological pathways, including development, reproduction, and metabolic homeostasis. In addition, aberrant expression of SRs or dysregulation of their signaling has been observed in a wide variety of pathologies. SR activity is tightly and finely controlled by post-translational modifications (PTMs) targeting the receptors and/or their coregulators. Whereas major attention has been focused on phosphorylation, growing evidence shows that methylation is also an important regulator of SRs. Interestingly, the protein methyltransferases depositing methyl marks are involved in many functions, from development to adult life. They have also been associated with pathologies such as inflammation, as well as cardiovascular and neuronal disorders, and cancer. This article provides an overview of SR methylation/demethylation events, along with their functional effects and biological consequences. An in-depth understanding of the landscape of these methylation events could provide new information on SR regulation in physiology, as well as promising perspectives for the development of new therapeutic strategies, illustrated by the specific inhibitors of protein methyltransferases that are currently available.

90 YEARS OF PROGESTERONE: Steroid receptors as MAPK signaling sensors in breast cancer: let the fates decide.

Steroid hormone receptors (SRs) are classically defined as ligand-activated transcription factors that function as master regulators of gene programs important for a wide range of processes governing adult physiology, development, and cell or tissue homeostasis. A second function of SRs includes the ability to activate cytoplasmic signaling pathways. Estrogen (ER), androgen (AR), and progesterone (PR) receptors bind directly to membrane-associated signaling molecules including mitogenic protein kinases (i.e. c-SRC and AKT), G-proteins, and ion channels to mediate context-dependent actions via rapid activation of downstream signaling pathways. In addition to making direct contact with diverse signaling molecules, SRs are further fully integrated with signaling pathways by virtue of their N-terminal phosphorylation sites that act as regulatory hot-spots capable of sensing the signaling milieu. In particular, ER, AR, PR, and closely related glucocorticoid receptors (GR) share the property of accepting (i.e. sensing) ligand-independent phosphorylation events by proline-directed kinases in the MAPK and CDK families. These signaling inputs act as a 'second ligand' that dramatically impacts cell fate. In the face of drugs that reliably target SR ligand-binding domains to block uncontrolled cancer growth, ligand-independent post-translational modifications guide changes in cell fate that confer increased survival, EMT, migration/invasion, stemness properties, and therapy resistance of non-proliferating SR+ cancer cell subpopulations. The focus of this review is on MAPK pathways in the regulation of SR+ cancer cell fate. MAPK-dependent phosphorylation of PR (Ser294) and GR (Ser134) will primarily be discussed in light of the need to target changes in breast cancer cell fate as part of modernized combination therapies.

Glucocorticoid receptor complexes form cooperatively with the Hsp90 co-chaperones Pp5 and FKBPs

The function of steroid receptors in the cell depends on the chaperone machinery of Hsp90, as Hsp90 primes steroid receptors for hormone binding and transcriptional activation. Several conserved proteins are known to additionally participate in receptor chaperone assemblies, but the regulation of the process is not understood in detail. Also, it is unknown to what extent the contribution of these cofactors is conserved in other eukaryotes. We here examine the reconstituted C. elegans and human chaperone assemblies. We find that the nematode phosphatase PPH-5 and the prolyl isomerase FKB-6 facilitate the formation of glucocorticoid receptor (GR) complexes with Hsp90. Within these complexes, Hsp90 can perform its closing reaction more efficiently. By combining chemical crosslinking and mass spectrometry, we define contact sites within these assemblies. Compared to the nematode Hsp90 system, the human system shows less cooperative client interaction and a stricter requirement for the co-chaperone p23 to complete the closing reaction of GR·Hsp90·Pp5/Fkbp51/Fkbp52 complexes. In both systems, hormone binding to GR is accelerated by Hsp90 alone and in the presence of its cofactors. Our results show that cooperative complex formation and hormone binding patterns are, in many aspects, conserved between the nematode and human systems.

Chromatin reprogramming in breast cancer.

Reprogramming of the chromatin landscape is a critical component to the transcriptional response in breast cancer. Effects of sex hormones such as estrogens and progesterone have been well described to have a critical impact on breast cancer proliferation. However, the complex network of the chromatin landscape, enhancer regions and mode of function of steroid receptors (SRs) and other transcription factors (TFs), is an intricate web of signaling and functional processes that is still largely misunderstood at the mechanistic level. In this review, we describe what is currently known about the dynamic interplay between TFs with chromatin and the reprogramming of enhancer elements. Emphasis has been placed on characterizing the different modes of action of TFs in regulating enhancer activity, specifically, how different SRs target enhancer regions to reprogram chromatin in breast cancer cells. In addition, we discuss current techniques employed to study enhancer function at a genome-wide level. Further, we have noted recent advances in live cell imaging technology. These single-cell approaches enable the coupling of population-based assays with real-time studies to address many unsolved questions about SRs and chromatin dynamics in breast cancer.

Modulation of Nuclear Receptor Function by Chromatin Modifying Factor TIP60.

Nuclear receptors (NRs) are transcription factors that bind to specific DNA sequences known as hormone response elements located upstream of their target genes. Transcriptional activity of NRs can be modulated by binding of the compatible ligand and transient interaction with cellular coregulators, functioning either as coactivators or as corepressors. Many coactivator proteins possess intrinsic histone acetyltransferase (HAT) activity that catalyzes the acetylation of specific lysine residues in histone tails and loosens the histone-DNA interaction, thereby facilitating access of transcriptional factors to the regulatory sequences of the DNA. Tat interactive protein 60 (TIP60), a member of the Mof-Ybf2-Sas2-TIP60 family of HAT protein, is a multifunctional coregulator that controls a number of physiological processes including apoptosis, DNA damage repair, and transcriptional regulation. Over the last two decades or so, TIP60 has been extensively studied for its role as NR coregulator, controlling various aspect of steroid receptor functions. The aim of this review is to summarize the findings on the role of TIP60 as a coregulator for different classes of NRs and its overall functional implications. We also discuss the latest studies linking TIP60 to NR-associated metabolic disorders and cancers for its potential use as a therapeutic drug target in future.

Signaling by Steroid Hormones in the 3D Nuclear Space.

Initial studies showed that ligand-activated hormone receptors act by binding to the proximal promoters of individual target genes. Genome-wide studies have now revealed that regulation of transcription by steroid hormones mainly depends on binding of the receptors to distal regulatory elements. Those distal elements, either enhancers or silencers, act on the regulation of target genes by chromatin looping to the gene promoters. In the nucleus, this level of chromatin folding is integrated within dynamic higher orders of genome structures, which are organized in a non-random fashion. Terminally differentiated cells exhibit a tissue-specific three-dimensional (3D) organization of the genome that favors or restrains the activity of transcription factors and modulates the function of steroid hormone receptors, which are transiently activated upon hormone exposure. Conversely, integration of the hormones signal may require modifications of the 3D organization to allow appropriate transcriptional outcomes. In this review, we summarize the main levels of organization of the genome, review how they can modulate the response to steroids in a cell specific manner and discuss the role of receptors in shaping and rewiring the structure in response to hormone. Taking into account the dynamics of 3D genome organization will contribute to a better understanding of the pleiotropic effects of steroid hormones in normal and cancer cells.

Steroid Receptor-Associated Immunophilins: Candidates for Diverse Drug-Targeting Approaches in Disease.

The steroid receptor-associated TPR cochaperones FKBP51, FKBP52, CyP40 and PP5 have non-redundant roles in steroid receptor function that impact steroid hormone-binding affinity, nucleocyoplasmic shuttling and transcriptional activation of target genes in a tissue-specific manner. Aberrant expression of these TPR immunophilins has the potential to cause steroid-based diseases, including breast and prostate cancer, diabetes and metabolic disorders, male and female infertility and major depressive and neurodegenerative disorders. This review summaries the function of these proteins as cochaperones in steroid receptor-Hsp90 complexes and elaborates on their role in alternative, Hsp90-dependent and -independent signalling pathways not involving steroid receptors. The review also extensively covers current knowledge of the link between the steroid receptor-associated immunophilins and human disease. An improved understanding of their mechanisms of action has revealed opportunities for molecular therapies to enhance or inhibit cellular processes under their control that contribute both to human health and disease.

APPLICATION OF SEREX-ANALYSIS FOR IDENTIFICATION OF HUMAN COLON CANCER ANTIGENS

Colorectal, lung and breast tumors are the most devastating and frequent malignances in clinical oncology. SEREX-analysis of colon cancer leads to identification of more than hundred antigens which are potential tumor markers. With idea that immunoscreening with pool of allogeneic sera is more productive for antigen isolation, SEREX-analysis was applied to four cases of stages II-IV primary colon tumor and 22 new antigens were isolated. To characterize 22 primary colon cancer antigens isolated by SEREX-technique. Allogenic screening, real-time PCR analysis. After allogeneic immunoscreening, for 5 of 22 (22%) isolated antigens were confirmed colon cancer restricted serological profile solely positive for 14% of tested colon cancer sera. Through these five antigens, KY-CC-17/β-actin has cytoskeleton function; KY-CC-14/ACTR1A and KY-CC-19/TSGA2 participate in chromosome segregation; KY-CC-12/FKBP4 regulates steroid receptor function and KY-CC-15/PLRG1 is a component of spliceosome complex. For the last four antigens tested were found aberrant mRNA expression in some cases of colon tumor. The exploration of identified antigens may define suitable targets for immunotherapy or diagnostic of colon cancer.

Biological relevance of Hsp90-binding immunophilins in cancer development and treatment.

Immunophilins are a family of intracellular receptors for immunosuppressive drugs. Those immunophilins that are related to immunosuppression are the smallest proteins of the family, i.e., FKBP12 and CyPA, whereas the other members of the family have higher molecular weight because the show additional domains to the drug-binding site. Among these extra domains, the TPR-domain is perhaps the most relevant because it permits the interaction of high molecular weight immunophilins with the 90-kDa heat-shock protein, Hsp90. This essential molecular chaperone regulates the biological function of several protein-kinases, oncogenes, protein phosphatases, transcription factors and cofactors . Hsp90-binding immunophilins where first characterized due to their association with steroid receptors. They regulate the cytoplasmic transport and the subcellular localization of these and other Hsp90 client proteins, as well as transcriptional activity, cell proliferation, cell differentiation and apoptosis. Hsp90-binding immunophilins are frequently overexpressed in several types of cancers and play a key role in cell survival. In this article we analyze the most important biological actions of the best characterized Hsp90-binding immunophilins in both steroid receptor function and cancer development and discuss the potential use of these immunophilins for therapeutic purposes as potential targets of specific small molecules.

Glucocorticoids and Cancer.

Unlike other steroid hormone receptors, the glucocorticoid receptor (GR) is not considered an oncogene. In breast cancer, the estrogen receptor (ER) drives cell growth, proliferation, and metastasis, and the androgen receptor (AR) plays a similar role in prostate cancer. Accordingly, treatment of these diseases has focused on blocking steroid hormone receptor function. In contrast, glucocorticoids (GCs) work through GR to arrest growth and induce apoptosis in lymphoid tissue. Glucocorticoids are amazingly effective in this role, and have been deployed as the cornerstone of lymphoid cancer treatment for decades. Unfortunately, not all patients respond to GCs and dosage is restricted by immediate and long term side effects. In this chapter we review the treatment protocols that employ glucocorticoids as a curative agent, elaborate on what is known about their mechanism of action in these cancers, and also summarize the palliative uses of glucocorticoids for other cancers.

Dissecting Steroid Receptor Function by Analytical Ultracentrifugation.

Steroid receptors comprise a family of ligand-activated transcription factors. The members include the androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and progesterone receptor (PR). Each receptor controls distinct sets of genes associated with development, metabolism, and homeostasis. Although a qualitative understanding of how individual receptors mediate gene expression has come into focus, quantitative insight remains less clear. As a step toward delineating the physical mechanisms by which individual receptors activate their target genes, we have carried out a systematic dissection of receptor interaction energetics with their multisite regulatory elements. Analytical ultracentrifugation (AUC) has proved indispensable in these studies, in part by revealing the energetics of receptor self-association and its thermodynamic coupling to DNA binding. Here, we discuss these findings in the context of understanding specificity of receptor-mediated gene control. We first highlight the role of sedimentation velocity and sedimentation equilibrium in addressing receptor assembly state, and present a comparative analysis across the receptor family. We then use these results for understanding how receptors assemble at multisite regulatory elements, and hypothesize how these findings might play a role in receptor-specific gene regulation. Finally, we examine receptor behavior in a cellular context, with a view toward linking our in vitro studies with in vivo function.

Abstract 332: Retinol-binding Protein 7 (RBP7) Regulates Endothelial Function, Independent of Metabolic Responses in High-fat Diet Fed Mice

Peroxisome proliferator-activated receptor gamma (PPARG), a ligand-activated transcription factor, plays a protective role in the endothelium through mechanisms that remain unclear. RBP7 is an intracellular retinoid binding protein belonging to the family of fatty acid-binding proteins (FABP) and is a PPARG target. RBP7 expression was increased 2.6-fold by rosiglitazone (RZ), a PPARG agonist in mouse lung endothelial cells, which was blocked by GW9662, a PPARG antagonist. We hypothesized that the protective effects of PPARG on the endothelium are mediated by RBP7. Studies were performed in: 20-week HFD-fed RBP7-deficient (KO) and wild type (WT) and age-matched chow-fed KO and WT mice. HFD increased fasting glucose in both WT and KO mice compared to chow-fed groups, and caused similar hepatic steatosis. HFD-fed mice were more glucose-intolerant and insulin-resistant compared with chow-fed mice, but there were no differences comparing KO with WT mice. Weight gain in response to HFD was also similar in KO and WT mice. Thus KO and WT mice exhibited similar HFD-induced metabolic dysfunction. Endothelium-dependent relaxation to acetylcholine (Ach) was normal in chow-fed KO mice, but was impaired in carotid artery of HFD-fed KO mice (49±6% KO vs 70±4% WT, p<0.05, 30μM Ach). Endothelial-independent relaxation was similar in all groups. Superoxide production in carotid artery (DHE-fluorescence) was elevated 1.5-fold in HFD-fed KO mice compared with the other 3 groups. Normal relaxation to Ach was restored by anti-oxidant treatment, suggesting HFD causes oxidative stress in the absence of RBP7. Systolic blood pressure was similar in HFD-fed KO and WT mice (110±4 mmHg in KO vs 105±0 mmHg in WT). Because other members of the FABP family facilitate steroid hormone receptor function, we hypothesized that RBP7 may facilitate PPARG function. To initially test this, we examined the cellular localization of an RBP7-GFP fusion protein. In vehicle treated COS7 cells, RBP7 was distributed both in cytoplasm and nucleus. RZ treatment resulted in a robust shift of RBP7 into the nucleus. In conclusion, RBP7 protects the endothelium from HFD-induced oxidative and vascular dysfunction, independent of changes to systemic metabolism.

The social network of PELP1 and its implications in breast and prostate cancers.

Proline, glutamic acid- and leucine-rich protein 1 (PELP1) is a multi-domain scaffold protein that serves as a platform for various protein-protein interactions between steroid receptors (SRs) and signaling factors and cell cycle, transcriptional, cytoskeletal, and epigenetic remodelers. PELP1 is known to be a coregulator of transcription and participates in the nuclear and extranuclear functions of SRs, ribosome biogenesis, and cell cycle progression. The expression and localization of PELP1 are dysregulated in hormonal cancers including breast and prostate cancers. This review focuses on the interactive functions and therapeutic and prognostic significance of PELP1 in breast and prostate cancers.