Evidence for a genomic mechanism of action for progesterone receptor membrane component-1

Altered luteal expression patterns of genomic and non-genomic progesterone receptors in bitches at different reproductive states

The binding of steroid hormones to their specific receptors is necessary to exert their effects on target cells. Progesterone (P4), a steroid hormone, carries out its effects through both genomic and non-genomic (the cell membrane-associated) receptors. This study aimed to ascertain luteal expression patterns of genomic and non-genomic progesterone receptors in bitches in physiological (early dioestrus and early pregnant) and pathological (pyometra) reproductive states. Luteal tissue was collected from the bitches at early dioestrus (ED, n = 5), early pregnant (EP, n = 5), and pyometra (PY, n = 5). The expression profiles of Steroidogenic Acute Regulator Protein (STAR), Progesterone Receptor (PGR), Membrane Progestin Receptors (PAQR5, PAQR7 and PAQR8), and Progesterone Membrane Components (PGMRC1 and PGMRC2) were examined at the mRNA levels using Real-Time Polymerase Chain Reaction (RT-PCR). Protein levels of PGR, PGMRC1 and PGMRC2 were detected by western blotting (WB). The STAR expression was found in all groups, with a statistical difference observed between EP and PY groups (P < 0.05). The protein level of PGR was determined to be highest in the EP group and lowest in the PY group. The expression of PAQR8 increased in the EP group (P < 0.05). The PAQR5 exhibited high expression in the EP group and low expression in the PY group (P < 0.05). PGRMC1 was more elevated in the EP group and lower in the PY group (P < 0.05). Protein levels of PGMRC1 and PGMRC2 were also observed at the highest expression in EP group. According to the altered expression profiles for examined receptors, we suggest that those progesterone receptors have roles in early pregnancy or pyometra in bitches.

Genetically incorporated crosslinkers identify regulators of membrane protein PD-L1 in mammalian cells

Profiling membrane proteins' interacting networks is crucial for understanding their regulatory mechanisms and functional characteristics, but it remains a challenging task. Here, by combining genetic incorporation of crosslinkers, tandem denatured purification, and proteomics, we added interaction partners for PD-L1, a cancer cell surface protein that inhibits T cell activity. The site-specifically incorporated crosslinker mediates the covalent capture of interactions under physiological conditions and enabled the PD-L1 complexes to withstand the harsh extraction conditions of membrane proteins. Subsequent experiments led to the identification of potential PD-L1 interaction candidates and verified membrane-associated progesterone receptor component 1 as a novel PD-L1 interaction partner in mammalian cells. Importantly, we demonstrated that PGRMC1 positively regulates PD-L1 expression by regulating GSK3β-mediated PD-L1 degradation in cancer cells. Furthermore, PGRMC1 knockdown results in dramatically enhanced T cell-mediated cytotoxicity in cancer cells. In conclusion, our study elucidated the interactome of PD-L1 and uncovered a new player in the PD-L1 regulation mechanism.

Progesterone signaling in the regulation of luteal steroidogenesis

The corpus luteum is the major source of progesterone, the essential hormone for female reproductive function. While progesterone activity has been the subject of extensive research for decades, characterization of non-canonical progesterone receptor/signaling pathways provided a new perspective for understanding the complex signal transduction mechanisms exploited by the progesterone hormone. Deciphering these mechanisms has significant implications in the management of luteal phase disorders and early pregnancy complications. The purpose of this review is to highlight the complex mechanisms through which progesterone-induced signaling mediates luteal granulosa cell activity in the corpus luteum. Here, we review the literature and discuss the up-to-date evidence on how paracrine and autocrine effects of progesterone regulate luteal steroidogenic activity. We also review the limitations of the published data and highlight future research priorities.

Pleiotropic Actions of PGRMC Proteins in Cancer

Progesterone receptor membrane component (PGRMC) proteins play important roles in tumor growth, progression, and chemoresistance, of which PGRMC1 is the best characterized. The ancestral member predates the evolution of metazoans, so it is perhaps not surprising that many of the purported actions of PGRMC proteins are rooted in fundamental metabolic processes such as proliferation, apoptosis, and DNA damage responses. Despite mediating some of the actions of progesterone (P4) and being fundamentally required for female fertility, PGRMC1 and PGRMC2 are broadly expressed in most tissues. As such, these proteins likely have both progesterone-dependent and progesterone-independent functions. It has been proposed that PGRMC1 acquired the ability to mediate P4 actions over evolutionary time through acquisition of its cytochrome b5-like heme/sterol-binding domain. Diverse reproductive and nonreproductive diseases associate with altered PGRMC1 expression, epigenetic regulation, or gene silencing mechanisms, some of which include polycystic ovarian disease, premature ovarian insufficiency, endometriosis, Alzheimer disease, and cancer. Although many studies have been completed using transformed cell lines in culture or in xenograft tumor approaches, recently developed transgenic model organisms are offering new insights in the physiological actions of PGRMC proteins, as well as pathophysiological and oncogenic consequences when PGRMC expression is altered. The purpose of this mini-review is to provide an overview of PGRMC proteins in cancer and to offer discussion of where this field must go to solidify PGRMC proteins as central contributors to the oncogenic process.

Progesterone Signaling and Mammalian Ovarian Follicle Growth Mediated by Progesterone Receptor Membrane Component Family Members

How progesterone influences ovarian follicle growth is a difficult question to answer because ovarian cells synthesize progesterone and express not only the classic nuclear progesterone receptor but also members of the progestin and adipoQ receptor family and the progesterone receptor membrane component (PGRMC) family. Which type of progestin receptor is expressed depends on the ovarian cell type as well as the stage of the estrous/menstrual cycle. Given the complex nature of the mammalian ovary, this review will focus on progesterone signaling that is transduced by PGRMC1 and PGRMC2 specifically as it relates to ovarian follicle growth. PGRMC1 was identified as a progesterone binding protein cloned from porcine liver in 1996 and detected in the mammalian ovary in 2005. Subsequent studies focused on PGRMC family members as regulators of granulosa cell proliferation and survival, two physiological processes required for follicle development. This review will present evidence that demonstrates a causal relationship between PGRMC family members and the promotion of ovarian follicle growth. The mechanisms through which PGRMC-dependent signaling regulates granulosa cell proliferation and viability will also be discussed in order to provide a more complete understanding of our current concept of how progesterone regulates ovarian follicle growth.

Progesterone Receptor Membrane Component (PGRMC)1 and PGRMC2 and Their Roles in Ovarian and Endometrial Cancer

Cancers of the female reproductive tract are both lethal and highly prevalent. For example, the five-year survival rate of women diagnosed with ovarian cancer is still less than 50%, and endometrial cancer is the fourth most common cancer in women with > 65,000 new cases in the United States in 2020. Among the many genes already established as key participants in ovarian and endometrial oncogenesis, progesterone receptor membrane component (PGRMC)1 and PGRMC2 have gained recent attention given that there is now solid correlative information supporting a role for at least PGRMC1 in enhancing tumor growth and chemoresistance. The expression of PGRMC1 is significantly increased in both ovarian and endometrial cancers, similar to that reported in other cancer types. Xenograft studies using human ovarian and endometrial cancer cell lines in immunocompromised mice demonstrate that reduced expression of PGRMC1 results in tumors that grow substantially slower. While the molecular underpinnings of PGRMCs' mechanisms of action are not clearly established, it is known that PGRMCs regulate survival pathways that attenuate stress-induced cell death. The objective of this review is to provide an overview of what is known about the roles that PGRMC1 and PGRMC2 play in ovarian and endometrial cancers, particularly as related to the mechanisms through which they regulate mitosis, apoptosis, chemoresistance, and cell migration.

Loss of β-Arrestins or six Gα proteins in HEK293 cells caused Warburg effect and prevented progesterone-induced rapid proteasomal degradation of progesterone receptor membrane component 1

Hormonal dysregulation plays a significant role in the metabolic switching during malignant transformation. Progesterone Receptor Membrane Component 1 (PGRMC1) is a single-pass transmembrane receptor activated by the binding of progesterone (P4), a sex hormone. In a previous study, P4 treatment caused rapid (within 30 min) induction of aerobic glycolysis in transformed HEK293 cells, a hallmark malignant phenotype known as the Warburg effect. This metabolic reprogramming was associated with the proteasomal degradation of a 70 kilodalton (kDa) PGRMC1. PGRMC1 interacts with a variety of proteins, including G protein-coupled receptors (GPCRs) and P4-PGRMC1 signaling modulates cyclic adenosine monophosphate (cAMP) production. Therefore, we hypothesized that the P4-induced Warburg effect and proteasomal degradation of PGRMC1 involve G proteins and β-Arrestins (ARRBs). In the present study, we investigated P4-induced aerobic glycolysis, proteasomal degradation of p70 PGRMC1, as well as abundance and subcellular translocation of PGRMC1 along with two key glycolytic enzymes Hexokinase 1 (HK1) and Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) in six Gα subunit (Gsix) proteins or ARRB1/2-deficient HEK293 cells. Loss of ARRB1/2 or Gsix proteins inhibited P4-induced p70 PGRMC1 degradation but failed to prevent the P4-induced Warburg effect. Also, deficiency of ARRB1/2 or Gsix proteins differentially affected the basal as well as P4-induced abundance and subcellular translocation of PGRMC1, HK1, and GAPDH proteins. Overall, the findings indicate that P4-PGRMC1-mediated metabolic reprogramming in HEK293 cells depends on β-Arrestins and Gα proteins suggesting the involvement of an underlying GPCR signal transduction pathway.

Effect of natural pre-luteolytic prostaglandin F2α pulses on the bovine luteal transcriptome during spontaneous luteal regression

The pulsatile pattern of prostaglandin F2alpha (PGF) secretion during spontaneous luteolysis is well-documented, with multiple pulses of exogenous PGF necessary to induce regression using physiologic concentrations of PGF. However, during spontaneous regression, the earliest pulses of PGF are small and not associated with detectable changes in circulating progesterone (P4), bringing into question what, if any, role these early, subluteolytic PGF pulses have during physiologic regression. To investigate the effect of small PGF pulses, luteal biopsies were collected throughout natural luteolysis in conjunction with bihourly blood samples to determine circulating P4 and PGF metabolite to retrospectively assign biopsies to early and later regression. Whole transcriptome analysis was conducted on CL biopsies. Early PGF pulses altered the luteal transcriptome, inducing differential expression of 210 genes (Q < 0.05) during early regression, compared to 4615 differentially expressed genes during later regression. In early regression, few of these differentially expressed genes were directly associated with luteolysis, rather there were changes in local steroid and glutathione metabolism. Most (94%) differentially expressed genes from early regression were also differentially expressed during later regression, with 98% of these continuing to be altered in the same direction compared to CL at a similar stage of the cycle that had not yet been exposed to PGF. Thus, early, subluteolytic PGF pulses impact the luteal transcriptome, though not by altering steroidogenesis or causing direct inhibition of cellular function. Rather, small pulses alter pathways resulting in removal of cellular support systems, which may sensitize the CL to later pulses of PGF.

Pregnancy-induced changes in the transcriptome of the bovine corpus luteum during and after embryonic interferon-tau secretion†

Understanding luteal maintenance during early pregnancy is of substantial biological and practical importance. Characterizing effects of early pregnancy, however, has historically been confounded by use of controls with potential exposure to early Prostaglandin F2-alpha (PGF) pulses or differences in Corpus Luteum (CL) age. To avoid this, the present study utilized bihourly blood sampling to ensure control CL (n = 6) were of a similar age to CL from pregnant animals (n = 5), yet without exposure to PGF pulses. Additionally, CL from second month of pregnancy (n = 4) were analyzed to track fate of altered genes after cessation of embryonic interferon tau (IFNT) secretion. The major alteration in gene expression in first month of pregnancy occurred in interferon-stimulated genes (ISGs), with immune/interferon signaling pathways enriched in three independent over-representation analyses. Most ISGs decreased during second month of pregnancy, though, surprisingly, some ISGs remained elevated in the second month even after cessation of IFNT secretion. Investigation of luteolytic genes found few altered transcripts, in contrast to previous reports, likely due to removal of controls exposed to PGF pulses. An exception to this trend was decreased expression of transcription factor NR4A1. Beyond luteolytic genes and ISGs, over representation analyses highlighted the prevalence of altered genes within the extracellular matrix and regulation of Insulin-like growth factor (IGF) availability, confirming results of other studies independent of luteolytic genes. These results support the idea that CL maintenance in early pregnancy is related to lack of PGF exposure, although potential roles for CL expression of diverse ISGs and other pathways activated during early pregnancy remain undefined.

PGRMC Proteins Are Coming of Age: A Special Issue on the Role of PGRMC1 and PGRMC2 in Metabolism and Cancer Biology

This is a preface by the guest editors of the special issue of Cancers featuring the biology of progesterone (P4) receptor membrane component (PGRMC) proteins as it relates to metabolism and cancer [...].

Progesterone receptor membrane component 1 is involved in oral cancer cell metastasis

Cancer metastasis is a common cause of failure in cancer therapy. However, over 60% of oral cancer patients present with advanced stage disease, and the five‐year survival rates of these patients decrease from 72.6% to 20% as the stage becomes more advanced. In order to manage oral cancer, identification of metastasis biomarker and mechanism is critical. In this study, we use a pair of oral squamous cell carcinoma lines, OC3, and invasive OC3‐I5 as a model system to examine invasive mechanism and to identify potential therapeutic targets. We used two‐dimensional differential gel electrophoresis (2D‐DIGE) and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF/TOF MS) to examine the global protein expression changes between OC3 and invasive OC3‐I5. A proteomic study reveals that invasive properties alter the expression of 101 proteins in OC3‐I5 cells comparing to OC3 cells. Further studies have used RNA interference technique to monitor the influence of progesterone receptor membrane component 1 (PGRMC1) protein in invasion and evaluate their potency in regulating invasion and the mechanism it involved. The results demonstrated that expression of epithelial‐mesenchymal transition (EMT) markers including Twist, p‐Src, Snail1, SIP1, JAM‐A, vimentin and vinculin was increased in OC3‐I5 compared to OC3 cells, whereas E‐cadherin expression was decreased in the OC3‐I5 cells. Moreover, in mouse model, PGRMC1 is shown to affect not only migration and invasion but also metastasis in vivo. Taken together, the proteomic approach allows us to identify numerous proteins, including PGRMC1, involved in invasion mechanism. Our results provide useful diagnostic markers and therapeutic candidates for the treatment of oral cancer invasion.

PGRMC1 effects on metabolism, genomic mutation and CpG methylation imply crucial roles in animal biology and disease

Background

Progesterone receptor membrane component 1 (PGRMC1) is often elevated in cancers, and exists in alternative states of phosphorylation. A motif centered on PGRMC1 Y180 was evolutionarily acquired concurrently with the embryological gastrulation organizer that orchestrates vertebrate tissue differentiation.

Results

Here, we show that mutagenic manipulation of PGRMC1 phosphorylation alters cell metabolism, genomic stability, and CpG methylation. Each of several mutants elicited distinct patterns of genomic CpG methylation. Mutation of S57A/Y180/S181A led to increased net hypermethylation, reminiscent of embryonic stem cells. Pathways enrichment analysis suggested modulation of processes related to animal cell differentiation status and tissue identity, as well as cell cycle control and ATM/ATR DNA damage repair regulation. We detected different genomic mutation rates in culture.

Conclusions

A companion manuscript shows that these cell states dramatically affect protein abundances, cell and mitochondrial morphology, and glycolytic metabolism. We propose that PGRMC1 phosphorylation status modulates cellular plasticity mechanisms relevant to early embryological tissue differentiation.

AG 205, a progesterone receptor membrane component 1 antagonist, ablates progesterone's ability to block oxidative stress-induced apoptosis of human granulosa/luteal cells†

The present studies were designed to determine whether progesterone (P4)-progesterone receptor membrane component 1 (PGRMC1) signaling is able to attenuate the apoptotic effects of oxidative stress induced by hydrogen peroxide (H2O2). To achieve this goal, freshly isolated human granulosa/luteal cells were maintained in culture. After several passages, the cells were treated with H2O2, which induced apoptosis within 2.5 h, while simultaneous treatment with P4 attenuated the apoptotic action of H2O2. AG 205, a PGRMC1 antagonist, eliminated P4's ability to prevent H2O2-induced apoptosis. AG 205 neither affected PGRMC1's cytoplasmic localization nor its interaction with PGRMC2, but appeared to reduce its presence within the nucleus. AG 205 also (1) increased the monomeric and decreased the higher molecular weight forms of PGRMC1 (i.e., dimers/oligomers) and (2) altered the expression of several genes involved in apoptosis. The most dramatic change was an approximate 8-fold increase in Harakiri (Hrk) mRNA. However, AG 205 did not induce apoptosis in the absence of H2O2. Taken together, these observations suggest that the higher molecular weight forms of PGRMC1 likely account in part for PGRMC1's ability to suppress the expression of Hrk. Harakiri is a BH-3 only member of the B-cell lymphoma 2 (BCL2) family that promotes apoptosis by binding to and antagonizing the antiapoptotic action of BCL2- and BCL2-like proteins. It is likely then that PGRMC1's ability to suppress Hrk is part of the mechanism through which P4-PGRMC1 signaling preserves the viability of human granulosa/luteal cells.

Progesterone Receptor Membrane Component 1 suppresses the p53 and Wnt/β-catenin pathways to promote human pluripotent stem cell self-renewal

Progesterone receptor membrane component 1 (PGRMC1) is a multifunctional heme-binding protein involved in various diseases, including cancers and Alzheimer’s disease. Previously, we generated two monoclonal antibodies (MAbs) 108-B6 and 4A68 against surface molecules on human pluripotent stem cells (hPSCs). Here we show that PGRMC1 is the target antigen of both MAbs, and is predominantly expressed on hPSCs and some cancer cells. PGRMC1 is rapidly downregulated during early differentiation of hPSCs. Although PGRMC1 knockdown leads to a spread-out morphology and impaired self-renewal in hPSCs, PGRMC1 knockdown hPSCs do not show apoptosis and autophagy. Instead, PGRMC1 knockdown leads to differentiation of hPSCs into multiple lineage cells without affecting the expression of pluripotency markers. PGRMC1 knockdown increases cyclin D1 expression and decreases Plk1 expression in hPSCs. PGRMC1 knockdown also induces p53 expression and stability, suggesting that PGRMC1 maintains hPSC self-renewal through suppression of p53-dependent pathway. Analysis of signaling molecules further reveals that PGRMC1 knockdown promotes inhibitory phosphorylation of GSK-3β and increased expression of Wnt3a and β-catenin, which leads to activation of Wnt/β-catenin signaling. The results suggest that PGRMC1 suppresses the p53 and Wnt/β-catenin pathways to promote self-renewal and inhibit early differentiation in hPSCs.

Platelet-predominate gene expression and reticulated platelets in nonvalvular atrial fibrillation: Effect of pulmonary veins isolation

INTRODUCTION

Reticulated platelet (RP) content is increased in nonvalvular atrial fibrillation (NVAF). The purpose of this study was to determine if platelet content, morphology, and RP proportion are modulated by platelet genes.

METHODS AND RESULTS

Expression of six platelet-predominate genes impacting platelet formation and release, platelet count, and RP content was assessed in NVAF patients before and 3-4 months after pulmonary veins isolation (PVI) and compared to normal sinus rhythm (NSR) controls. RNA from isolated platelets was reverse-transcribed assayed against selected genes utilizing real-time qPCR, and expressed as mean cycle threshold (ΔCt) using beta-2-microglobulin as endogenous control. RP content was assessed by flow cytometry. A fourfold lower expression of CFL1 gene coding for nonmuscle cofilin (7.8 ± 0.9 vs. 5.7 ± 1.6, P < 0.001) and twofold lower expression of four other genes were associated with similar platelet counts but fourfold higher (28.7+7.0 vs. 6.7+5.4, P < 0.001) RP content (%) in 97 NVAF cases compared to 51 NSR controls. Three to 4 months after PVI, RP decreased by 28%, while CFL1 gene expression increased over twofold but TUBA4A gene expression decreased almost twofold; NFE2 and MYL6 gene expression remained unchanged.

CONCLUSIONS

NVAF is associated with notable downregulation of genes directing platelet production and size but increased RP content. PVI impacts the expression of many of these genes, implying a direct relationship between atrial fibrillation and platelet biogenesis.

Dynamic expression of PGRMC1 and SERBP1 in human endometrium: an implication in the human decidualization process

OBJECTIVE

To characterize PGRMC1 and SERBP1 in human endometrium and to investigate the putative role of PGRMC1 in endometrial decidualization.

DESIGN

The PGRMC1 and SERBP1 expression in human endometrium was determined throughout the menstrual cycle. We analyzed the colocalization of PGRMC1 and SERBP1. Then, endometrial stromal cells (ESCs) were isolated to investigate the functional effect of PGRMC1 overexpression on decidualization.

SETTING

IVI clinic.

PATIENT(S)

Endometrial biopsies were collected from fertile volunteers (n = 61) attending the clinic as ovum donors.

INTERVENTION(S)

Endometrial samples of 61 healthy fertile women.

MAIN OUTCOME MEASURE(S)

In vivo localization of PGRMC1 and SERBP1 was assessed by immunohistochemistry. The PGRMC1/SERBP1 colocalization was investigated in vitro and in vivo. Decidualization effect of PGRMC1 overexpression was evaluated in primary ESC cultures.

RESULT(S)

The PGRMC1 was detected in the endometrial stroma throughout the menstrual cycle, but decreased in the late secretory phase. The SERBP1 immunostaining was present in stroma and increased in the entire the menstrual cycle. The PGRMC1 and SERBP1 colocalized in the cytoplasmic fractions of nondecidualized and decidualized ESC. The PGRMC1 overexpression significantly inhibited in vitro decidualization.

CONCLUSION(S)

Our results suggest that classic P receptors (PRs) are not the only kind playing a role in the normal physiology of the endometrium. The human decidualization process could be altered by the overexpression or mislocalization of PGRMC1 in ESC.

The ESC/E(Z) complex, an effector of response to ovarian steroids, manifests an intrinsic difference in cells from women with premenstrual dysphoric disorder

Clinical evidence suggests that mood and behavioral symptoms in premenstrual dysphoric disorder (PMDD), a common, recently recognized, psychiatric condition among women, reflect abnormal responsivity to ovarian steroids. This differential sensitivity could be due to an unrecognized aspect of hormonal signaling or a difference in cellular response. In this study, lymphoblastoid cell line cultures (LCLs) from women with PMDD and asymptomatic controls were compared via whole-transcriptome sequencing (RNA-seq) during untreated (ovarian steroid-free) conditions and following hormone treatment. The women with PMDD manifested ovarian steroid-triggered behavioral sensitivity during a hormone suppression and addback clinical trial, and controls did not, leading us to hypothesize that women with PMDD might differ in their cellular response to ovarian steroids. In untreated LCLs, our results overall suggest a divergence between mRNA (for example, gene transcription) and protein (for example, RNA translation in proteins) for the same genes. Pathway analysis of the LCL transcriptome revealed, among others, over-expression of ESC/E(Z) complex genes (an ovarian steroid-regulated gene silencing complex) in untreated LCLs from women with PMDD, with more than half of these genes over-expressed as compared with the controls, and with significant effects for MTF2, PHF19 and SIRT1 (P<0.05). RNA and protein expression of the 13 ESC/E(Z) complex genes were individually quantitated. This pattern of increased ESC/E(Z) mRNA expression was confirmed in a larger cohort by qRT-PCR. In contrast, protein expression of ESC/E(Z) genes was decreased in untreated PMDD LCLs with MTF2, PHF19 and SIRT1 all significantly decreased (P<0.05). Finally, mRNA expression of several ESC/E(Z) complex genes were increased by progesterone in controls only, and decreased by estradiol in PMDD LCLs. These findings demonstrate that LCLs from women with PMDD manifest a cellular difference in ESC/E(Z) complex function both in the untreated condition and in response to ovarian hormones. Dysregulation of ESC/E(Z) complex function could contribute to PMDD.

Impact of atrial fibrillation on platelet gene expression

AIMS

Platelets retain cytoplasmic messenger RNA and are capable of protein biosynthesis. Several diseases are known to impact the platelet transcriptome but the effect of non-valvular atrial fibrillation (NVAF) on platelet RNA transcript is essentially unknown. The aim of this study was to evaluate the impact of NVAF on platelet RNA transcript by measuring platelet genes expression in consecutive NVAF patients before and 3-4 months after pulmonary vein isolation (PVI) and compared to normal sinus rhythm controls (NSR).

METHODS AND RESULTS

RNA from isolated platelets were reverse transcribed, assayed against 15 genes using real-time qPCR, and expressed as mean cycle threshold (ΔCt) using beta-2-microglobulin as endogenous control. Expression of all evaluated genes, except cathepsin A gene, was significantly lower (higher ΔCt) in 103 NVAF patients compared to 55 NSR controls. Insulin-like growth factor binding protein acid labile subunit gene (IGFALS) had expression more than 16 fold-lower (17.0±2.8 vs 12.5±3.8, P<.001), follow by genes encoding for prostacyclin receptor, and for von Willebrand factor which had fourfold lower expression compared to NSR controls. Gender, type of atrial fibrillation, heart failure, hypertension, prior stroke, diabetes mellitus, and atherosclerosis were associated with different gene expression. Following PVI, expression of four genes significantly increased, particularly IGFALS gene (increased 256-fold) and ADAMT gene increased 16-fold); expression of three genes significantly decreased, and expression of eight genes has not changed.

CONCLUSIONS

Platelets are capable to respond to the circulatory environment of NVAF by altering transcript and changing prothrombotic status. This shows platelet potential for molecular "reprogramming" possibly induced by flow disturbances of NVAF.

Conditional Ablation of Progesterone Receptor Membrane Component 1 Results in Subfertility in the Female and Development of Endometrial Cysts

Progesterone (P4) is essential for female fertility. The objective of this study was to evaluate the functional requirement of the nonclassical P4 receptor (PGR), PGR membrane component 1, in regulating female fertility. To achieve this goal, the Pgrmc1 gene was floxed by insertion of loxP sites on each side of exon 2. Pgrmc1 floxed (Pgrmc1(fl/fl)) mice were crossed with Pgr(cre) or Amhr2(cre) mice to delete Pgrmc1 (Pgrmc1(d/d)) from the female reproductive tract. A 6-month breeding trial revealed that conditional ablation of Pgrmc1 with Pgr(cre/+) mice resulted in a 40% reduction (P = .0002) in the number of pups/litter. Neither the capacity to ovulate in response to gonadotropin treatment nor the expression of PGR and the estrogen receptor was altered in the uteri of Pgrmc1(d/d) mice compared with Pgrmc1(fl/fl) control mice. Although conditional ablation of Pgrmc1 from mesenchymal tissue using Amhr2(cre/+) mice did not reduce the number of pups/litter, the total number of litters born in the 6-month breeding trial was significantly decreased (P = .041). In addition to subfertility, conditional ablation of Pgrmc1 using either Amhr2(cre/+) or Pgr(cre/+) mice resulted in the development of endometrial cysts starting around 4 months of age. Interestingly, pregnancy attenuated the formation of these uterine cysts. These new findings demonstrate that PGR membrane component 1 plays an important role in female fertility and uterine tissue homeostasis.

Expression of Progesterone Receptor Membrane Component 1 (PGRMC1), Progestin and AdipoQ Receptor 7 (PAQPR7), and Plasminogen Activator Inhibitor 1 RNA-Binding Protein (PAIRBP1) in Glioma Spheroids In Vitro

Objective. Some effects of progesterone on glioma cells can be explained through the slow, genomic mediated response via nuclear receptors; the other effects suggest potential role of a fast, nongenomic action mediated by membrane-associated progesterone receptors. Methods. The effects of progesterone treatment on the expression levels of progesterone receptor membrane component 1 (PGRMC1), plasminogen activator inhibitor 1 RNA-binding protein (PAIRBP1), and progestin and adipoQ receptor 7 (PAQR7) on both mRNA and protein levels were investigated in spheroids derived from human glioma cell lines U-87 MG and LN-229. Results. The only significant alteration at the transcript level was the decrease in PGRMC1 mRNA observed in LN-229 spheroids treated with 30 ng/mL of progesterone. No visible alterations at the protein levels were observed using immunohistochemical analysis. Stimulation of U-87 MG spheroids resulted in an increase of PGRMC1 but a decrease of PAIRBP1 protein. Double immunofluorescent detection of PGRMC1 and PAIRBP1 identified the two proteins to be partially colocalized in the cells. Western blot analysis revealed the expected bands for PGRMC1 and PAIRBP1, whereas two bands were detected for PAQR7. Conclusion. The progesterone action is supposed to be mediated via membrane-associated progesterone receptors as the nuclear progesterone receptor was absent in tested spheroids.

Progesterone receptor membrane component-1 regulates hepcidin biosynthesis

Iron homeostasis is tightly regulated by the membrane iron exporter ferroportin and its regulatory peptide hormone hepcidin. The hepcidin/ferroportin axis is considered a promising therapeutic target for the treatment of diseases of iron overload or deficiency. Here, we conducted a chemical screen in zebrafish to identify small molecules that decrease ferroportin protein levels. The chemical screen led to the identification of 3 steroid molecules, epitiostanol, progesterone, and mifepristone, which decrease ferroportin levels by increasing the biosynthesis of hepcidin. These hepcidin-inducing steroids (HISs) did not activate known hepcidin-inducing pathways, including the BMP and JAK/STAT3 pathways. Progesterone receptor membrane component-1 (PGRMC1) was required for HIS-dependent increases in hepcidin biosynthesis, as PGRMC1 depletion in cultured hepatoma cells and zebrafish blocked the ability of HISs to increase hepcidin mRNA levels. Neutralizing antibodies directed against PGRMC1 attenuated the ability of HISs to induce hepcidin gene expression. Inhibiting the kinases of the SRC family, which are downstream of PGRMC1, blocked the ability of HISs to increase hepcidin mRNA levels. Furthermore, HIS treatment increased hepcidin biosynthesis in mice and humans. Together, these data indicate that PGRMC1 regulates hepcidin gene expression through an evolutionarily conserved mechanism. These studies have identified drug candidates and potential therapeutic targets for the treatment of diseases of abnormal iron metabolism.

Progesterone receptor signalling in retinal photoreceptor neuroprotection

'Norgestrel', a synthetic form of the female hormone progesterone has been identified as potential drug candidate for the treatment of the degenerative eye disease retinitis pigmentosa. However, to date, no work has looked at the compound's specific cellular target. Therefore, this study aimed to identify the receptor target of Norgestrel and begin to examine its potential mechanism of action in the retina. In this work, we identify and characterize the expression of progesterone receptors present in the C57 wild type and rd10 mouse model of retinitis pigmentosa. Classical progesterone receptors A and B (PR A/B), progesterone receptor membrane components 1 and 2 (PGRMC1, PGRMC2) and membrane progesterone receptors α, β and γ were found to be expressed. All receptors excluding PR A/B were also found in the 661W photoreceptor cell line. PGRMC1 is a key regulator of apoptosis and its expression is up-regulated in the degenerating rd10 mouse retina. Activated by Norgestrel through nuclear trafficking, siRNA knock down of PGRMC1 abrogated the protective properties of Norgestrel on damaged photoreceptors. Furthermore, specific inhibition of PGRMC1 by AG205 blocked Norgestrel-induced protection in stressed retinal explants. Therefore, we conclude that PGRMC1 is crucial to the neuroprotective effects of Norgestrel on stressed photoreceptors. The synthetic progestin 'Norgestrel' has been identified as a potential therapeutic for the treatment of Retinitis Pigmentosa, a degenerative eye disease. However, the mechanism behind this neuroprotection is currently unknown. In this work, we identify 'Progesterone Receptor Membrane Component 1' as the major progesterone receptor eliciting the protective effects of Norgestrel, both in vitro and ex vivo. This furthers our understanding of Norgestrel's molecular mechanism, which we hope will help bring Norgestrel one step closer to the clinic.

Induction of proteinases in the human preovulatory follicle of the menstrual cycle by human chorionic gonadotropin

OBJECTIVE

To explore the temporal expression in granulosa and theca cells of key members of the MMP and ADAMTS families across the periovulatory period in women to gain insight into their possible roles during ovulation and early luteinization.

DESIGN

Experimental prospective clinical study and laboratory-based investigation.

SETTING

University medical center and private IVF center.

ANIMAL AND PATIENT(S)

Thirty-eight premenopausal women undergoing surgery for tubal ligation and six premenopausal women undergoing assisted reproductive techniques.

INTERVENTION(S)

Administration of hCG and harvesting of follicles by laparoscopy and collection of granulosa-lutein cells at oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Expression of mRNA for matrix metalloproteinase (MMPs) and the A disintegrin and metalloproteinase with thrombospondin-like motifs (ADAMTS) in human granulosa cells and theca cells collected across the periovulatory period of the menstrual cycle and in cultured granulosa-lutein cells after hCG. Localization of MMPs and ADAMTSs by immunohistochemistry.

RESULT(S)

Expression of MMP1 and MMP19 mRNA increased in both granulosa and theca cells after hCG administration. ADAMTS1 and ADAMTS9 mRNA increased in granulosa cells after hCG treatment, however, thecal cell expression for ADAMTS1 was unchanged, while ADAMTS9 expression was decreased. Expression of MMP8 and MMP13 mRNA was unchanged. Immunohistochemistry confirmed the localization of MMP1, MMP19, ADAMTS1, and ADAMTS9 to the granulosa and thecal cell layers.

CONCLUSION(S)

The collection of the dominant follicle throughout the periovulatory period has allowed the identification of proteolytic remodeling enzymes in the granulosa and theca compartments that may be critically involved in human ovulation. These proteinases may work in concert to regulate breakdown of the follicular wall and release of the oocyte.

Progesterone receptor membrane component 1 deficiency attenuates growth while promoting chemosensitivity of human endometrial xenograft tumors

Endometrial cancer is the leading gynecologic cancer in women in the United States with 52,630 women predicted to be diagnosed with the disease in 2014. The objective of this study was to determine if progesterone (P4) receptor membrane component 1 (PGRMC1) influenced endometrial cancer cell viability in response to chemotherapy in vitro and in vivo. A lentiviral-based shRNA knockdown approach was used to generate stable PGRMC1-intact and PGRMC1-deplete Ishikawa endometrial cancer cell lines that also lacked expression of the classical progesterone receptor (PGR). Progesterone treatment inhibited mitosis of PGRMC1-intact, but not PGRMC1-deplete cells, suggesting that PGRMC1 mediates the anti-mitotic actions of P4. To test the hypothesis that PGRMC1 attenuates chemotherapy-induced apoptosis, PGRMC1-intact and PGRMC1-deplete cells were treated in vitro with vehicle, P4 (1 µM), doxorubicin (Dox, 2 µg/ml), or P4 + Dox for 48 h. Doxorubicin treatment of PGRMC1-intact cells resulted in a significant increase in cell death; however, co-treatment with P4 significantly attenuated Dox-induced cell death. This response to P4 was lost in PGRMC1-deplete cells. To extend these observations in vivo, a xenograft model was employed where PGRMC1-intact and PGRMC1-deplete endometrial tumors were generated following subcutaneous and intraperitoneal inoculation of immunocompromised NOD/SCID and nude mice, respectively. Tumors derived from PGRMC1-deplete cells grew slower than tumors from PGRMC1-intact cells. Mice harboring endometrial tumors were then given three treatments of vehicle (1:1 cremophor EL: ethanol + 0.9% saline) or chemotherapy [Paclitaxel (15 mg/kg, i.p.) followed after an interval of 30 minutes by CARBOplatin (50 mg/kg)] at five day intervals. In response to chemotherapy, tumor volume decreased approximately four-fold more in PGRMC1-deplete tumors when compared with PGRMC1-intact control tumors, suggesting that PGRMC1 promotes tumor cell viability during chemotherapeutic stress. In sum, these in vitro and in vivo findings demonstrate that PGRMC1 plays a prominent role in the growth and chemoresistance of human endometrial tumors.

Nuclear cytoplasmic trafficking of proteins is a major response of human fibroblasts to oxidative stress

We have used a subcellular spatial razor approach based on LC-MS/MS-based proteomics with SILAC isotope labeling to determine changes in protein abundances in the nuclear and cytoplasmic compartments of human IMR90 fibroblasts subjected to mild oxidative stress. We show that response to mild tert-butyl hydrogen peroxide treatment includes redistribution between the nucleus and cytoplasm of numerous proteins not previously associated with oxidative stress. The 121 proteins with the most significant changes encompass proteins with known functions in a wide variety of subcellular locations and of cellular functional processes (transcription, signal transduction, autophagy, iron metabolism, TCA cycle, ATP synthesis) and are consistent with functional networks that are spatially dispersed across the cell. Both nuclear respiratory factor 2 and the proline regulatory axis appear to contribute to the cellular metabolic response. Proteins involved in iron metabolism or with iron/heme as a cofactor as well as mitochondrial proteins are prominent in the response. Evidence suggesting that nuclear import/export and vesicle-mediated protein transport contribute to the cellular response was obtained. We suggest that measurements of global changes in total cellular protein abundances need to be complemented with measurements of the dynamic subcellular spatial redistribution of proteins to obtain comprehensive pictures of cellular function.

Progesterone receptor membrane component-1 (PGRMC1) and PGRMC-2 interact to suppress entry into the cell cycle in spontaneously immortalized rat granulosa cells

Progesterone receptor membrane component 1 (PGRMC1) and PGRMC2 are expressed in rat granulosa cells and spontaneously immortalized granulosa cells (SIGCs) but their biological roles are not well defined. The present studies demonstrate that depleting either Pgrmc1 or Pgrmc2 in SIGCs increases entry into the cell cycle but does not increase cell proliferation. Rather, PGRMC1 and/or PGRMC2-deplete cells accumulate in metaphase and undergo apoptosis. Because both PGRMC1 and PGRMC2 localize to the mitotic spindle, their absence likely accounts for cells arresting in metaphase. Moreover, pull-down assays, colocalization studies and in situ proximity ligation assays (PLA) indicate that PGRMC1 binds PGRMC2. Disrupting the PGRMC1:PGRMC2 complex through the use of siRNA or the cytoplasmic delivery of a PGRMC2 antibody increases entry into the cell cycle. Conversely, overexpressing either PGRMC1-GFP or GFP-PGRMC2 fusion protein inhibits entry into the cell cycle. Subsequent studies reveal that depleting PGRMC1 and/or PGRMC2 reduces the percentage of cells in G0 and increases the percentage of cells in G1. These observations indicate that in addition to their role at metaphase, PGRMC1 and PGRMC2 are involved in regulating entry into the G1 stage of the cell cycle. Interestingly, both PGRMC1 and PGRMC2 bind GTPase-activating protein-binding protein 2 (G3BP2) as demonstrated by pull-down assays, colocalization assays, and PLAs. G3bp2 siRNA treatment also promotes entry into the G1 stage. This implies that dynamic changes in the interaction among PGRMC1, PGRMC2, and G3BP2 play an important protein regulating the rate at which SIGCs enter into the cell cycle.

Hyaluronic acid promotes the expression of progesterone receptor membrane component 1 via epigenetic silencing of miR-139-5p in human and rat granulosa cells

Primary ovarian insufficiency (POI) is a serious reproductive dysfunction in which the follicle pool is reduced and depleted. Abnormal apoptosis of ovarian granulosa cells (GCs) is believed to result in follicle loss. Progesterone receptor membrane component 1 (PGRMC1), which is critical for GC survival, was reported to be reduced in POI patients, but the mechanism is unknown. In the present study, we found that PGRMC1 expression was correlated with the level of hyaluronic acid (HA) in POI patients. HA up-regulated PGRMC1 expression in GCs via suppression of miR-139-5p, which was proven by Western blotting and luciferase reporter assays to target PGRMC1. Consistent with these findings, levels of miR-139-5p were significantly increased and presented an inverse correlation with PGRMC1 in POI patients. Noticeably, HA inhibited CD44-mediated miR-139-5p expression but had no effect on luciferase activity after insertion of miR-139 promoter into luciferase plasmid. Interestingly, miR-139-5p was significantly up-regulated in KGN cells (GC tumor cell line) by the histone deacetylase inhibitor trichostatin A, indicating that HA down-regulated miR-139-5p expression via histone deacetylation. Taken together, we report an unrecognized mechanism of HA in the promotion of PGRMC1 expression, suggesting that HA may be a potential molecule for the prevention and treatment of POI.

Analysis of progesterone receptor membrane component 1 mutation in Han Chinese women with premature ovarian failure

The gene PGRMC1 is highly expressed in the granulose and luteal cells of rodent and primate ovaries. Its role in anti-apoptosis and regulating cell-cycle progression suggests a role in regulating follicle growth. The hypothesis is supported by the study in mice and studies in Sweden. In this study, the coding exons of PGRMC1 were sequenced among 196 Chinese women with premature ovarian failure (POF) and 200 controls, and one novel missense mutation was identified (C.556C>T, p. Pro186Ser) in the POF group and one novel SNP (C.533C>T, p. Trh177Ile) was identified in both groups. The mutation is not considered causative because protein prediction did not indicate a deleterious effect. It is concluded that coding mutations of PGRMC1 do not seem to be a common cause of the disease in Han Chinese women. Future studies in larger cohorts from other ethnic groups are necessary to establish the role of PGRMC1 in POF.

Expression of progesterone receptor membrane component-2 within the immature rat ovary and its role in regulating mitosis and apoptosis of spontaneously immortalized granulosa cells

Progesterone receptor membrane component 2 (Pgrmc2) mRNA was detected in the immature rat ovary. By 48 h after eCG, Pgrmc2 mRNA levels decreased by 40% and were maintained at 48 h post-hCG. Immunohistochemical studies detected PGRMC2 in oocytes and ovarian surface epithelial, interstitial, thecal, granulosa, and luteal cells. PGRMC2 was also present in spontaneously immortalized granulosa cells, localizing to the cytoplasm of interphase cells and apparently to the mitotic spindle of cells in metaphase. Interestingly, PGRMC2 levels appeared to decrease during the G1 stage of the cell cycle. Moreover, overexpression of PGRMC2 suppressed entry into the cell cycle, possibly by binding the p58 form of cyclin dependent kinase 11b. Conversely, Pgrmc2 small interfering RNA (siRNA) treatment increased the percentage of cells in G1 and M stage but did not increase the number of cells, which was likely due to an increase in apoptosis. Depleting PGRMC2 did not inhibit cellular (3)H-progesterone binding, but attenuated the ability of progesterone to suppress mitosis and apoptosis. Taken together these studies suggest that PGRMC2 affects granulosa cell mitosis by acting at two specific stages of the cell cycle. First, PGRMC2 regulates the progression from the G0 into the G1 stage of the cell cycle. Second, PGRMC2 appears to localize to the mitotic spindle, where it likely promotes the final stages of mitosis. Finally, siRNA knockdown studies indicate that PGRMC2 is required for progesterone to slow the rate of granulosa cell mitosis and apoptosis. These findings support a role for PGRMC2 in ovarian follicle development.

Non-canonical progesterone signaling in granulosa cell function

It has been known for over 3 decades that progesterone (P4) suppresses follicle growth. It has been assumed that P4 acts directly on granulosa cells of developing follicles to slow their development, as P4 inhibits both mitosis and apoptosis of cultured granulosa cells. However, granulosa cells of developing follicles of mice, rats, monkeys, and humans do not express the A or B isoform of the classic nuclear receptor for P4 (PGR). By contrast, these granulosa cells express other P4 binding proteins, one of which is referred to as PGR membrane component 1 (PGRMC1). PGRMC1 specifically binds P4 with high affinity and mediates P4's anti-mitotic and anti-apoptotic action as evidenced by the lack of these P4-dependent effects in PGRMC1-depleted cells. In addition, mice in which PGRMC1 is conditionally depleted in granulosa cells show diminished follicle development. While the mechanism through which P4 activation of PGRMC1 affects granulosa cell function is not well defined, it appears that PGRMC1 controls granulosa cell function in part by regulating gene expression in T-cell-specific transcription factor/lymphoid enhancer factor-dependent manner. Clinically, altered PGRMC1 expression has been correlated with premature ovarian failure/insufficiency, polycystic ovarian syndrome, and infertility. These collective studies provide strong evidence that PGRMC1 functions as a receptor for P4 in granulosa cells and that altered expression results in compromised reproductive capacity. Ongoing studies seek to define the components of the signal transduction cascade through which P4 activation of PGRMC1 results in the regulation of granulosa cell function.

Nonclassical progesterone signalling molecules in the nervous system

Progesterone (P4) regulates a wide range of cognitive, neuroendocrine, neuroimmune and neuroprotective functions. Therefore, it is not surprising that this ovarian hormone acts through multiple receptors. Ever since the 1980s, studies investigating the neural effects of P4 have focused mainly on genomic and nongenomic actions of the classical progestin receptor (PGR). More recently, two groups of nonclassical P4 signalling molecules have been identified: (i) the class II progestin and adipoQ receptor (PAQR) family, which includes PAQR 5, 6, 7, 8 and 9, also called membrane progestin receptor α (mPRα; PAQR7), mPRβ (PAQR8), mPRγ (PAQR5), mPRδ (PAQR6) and mPRε (PAQR9), and (ii) the b5-like haeme/steroid-binding protein family, which includes progesterone receptor membrane component 1 (Pgrmc1), Pgrmc2, neudesin and neuferricin. In this review, we describe the structures, neuroanatomical localisation and signalling mechanisms of these molecules. We also discuss gonadotrophin-releasing hormone regulation as an example of a physiological function regulated by multiple progesterone receptors but through different mechanisms.

Revisiting the roles of progesterone and allopregnanolone in the nervous system: resurgence of the progesterone receptors

Progesterone is commonly considered as a female reproductive hormone and is well-known for its role in pregnancy. It is less well appreciated that progesterone and its metabolite allopregnanolone are also male hormones, as they are produced in both sexes by the adrenal glands. In addition, they are synthesized within the nervous system. Progesterone and allopregnanolone are associated with adaptation to stress, and increased production of progesterone within the brain may be part of the response of neural cells to injury. Progesterone receptors (PR) are widely distributed throughout the brain, but their study has been mainly limited to the hypothalamus and reproductive functions, and the extra-hypothalamic receptors have been neglected. This lack of information about brain functions of PR is unexpected, as the protective and trophic effects of progesterone are much investigated, and as the therapeutic potential of progesterone as a neuroprotective and promyelinating agent is currently being assessed in clinical trials. The little attention devoted to the brain functions of PR may relate to the widely accepted assumption that non-reproductive actions of progesterone may be mainly mediated by allopregnanolone, which does not bind to PR, but acts as a potent positive modulator of γ-aminobutyric acid type A (GABA(A) receptors. The aim of this review is to critically discuss effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABA(A) receptors, with main focus on the brain.

PGRMC1 and PGRMC2 in uterine physiology and disease

It is clear from studies using progesterone receptor (PGR) mutant mice that not all of the actions of progesterone (P4) are mediated by this receptor. Indeed, many rapid, non-classical P4 actions have been reported throughout the female reproductive tract. Progesterone treatment of Pgr null mice results in behavioral changes and in differential regulation of genes in the endometrium. Progesterone receptor membrane component (PGRMC) 1 and PGRMC2 belong to the heme-binding protein family and may serve as P4 receptors. Evidence to support this derives chiefly from in vitro culture work using primary or transformed cell lines that lack the classical PGR. Endometrial expression of PGRMC1 in menstrual cycling mammals is most abundant during the proliferative phase of the cycle. Because PGRMC2 expression shows the most consistent cross-species expression, with highest levels during the secretory phase, PGRMC2 may serve as a universal non-classical P4 receptor in the uterus. While the functional importance of PGRMC1/2 in the uterus remains to be fully explored, accumulating evidence suggests that disruption in PGRMC1/2 expression correlates with uterine disease. In this review we will summarize what is known about PGRMC1/2 in uterine physiology and we will provide examples of disrupted expression of these genes in uterine disease states.

Sigma-2 receptor ligands and their perspectives in cancer diagnosis and therapy

The sigma-2 receptor is highly expressed in various rapidly proliferating cancer cells and regarded as a cancer cell biomarker. Selective sigma-2 ligands have been shown to specifically label the tumor sites, induce cancer cells to undergo apoptosis, and inhibit tumor growth. Sigma-2 ligands are potentially useful as cancer diagnostics, anticancer therapeutics, or adjuvant anticancer treatment agents. However, both the cloning of this receptor and the identification of its endogenous ligand have not been successful, and the lack of structural information has severely hindered the understanding of its physiological roles, its signaling pathways, and the development of more selective sigma-2 ligands. Recent data have implicated that sigma-2 binding sites are within the lipid rafts and that PGRMC1 (progesterone receptor membrane component 1) complex and sigma-2 receptor may be coupled with EGFR (epidermal growth factor receptor), mTOR (mammalian target of rapamycin), caspases, and ion channels. Due to its promising applications in cancer management, there are rapidly increasing research efforts that are being directed into this field. This review article updates the current understanding of sigma-2 receptor and its potential physiological roles, applications, interaction with other effectors, with special focuses on the development of sigma-2 ligands, their chemical structures, pharmacological profiles, applications in imaging and anticancer therapy.

Progesterone antagonism of neurite outgrowth depends on microglial activation via Pgrmc1/S2R

Neuronal plasticity is regulated by the ovarian steroids estradiol (E2) and progesterone (P4) in many normal brain functions, as well as in acute response to injury and chronic neurodegenerative disease. In a female rat model of axotomy, the E2-dependent compensatory neuronal sprouting is antagonized by P4. To resolve complex glial-neuronal cell interactions, we used the "wounding-in-a-dish" model of neurons cocultured with astrocytes or mixed glia (microglia to astrocytes, 1:3). Although both astrocytes and mixed glia supported E2-enhanced neurite outgrowth, P4 antagonized E2-induced neurite outgrowth only with mixed glia, but not astrocytes alone. We now show that P4-E2 antagonism of neurite outgrowth is mediated by microglial expression of progesterone receptor (Pgr) membrane component 1 (Pgrmc1)/S2R, a putative nonclassical Pgr mediator with multiple functions. The P4-E2 antagonism of neurite outgrowth was restored by add-back of microglia to astrocyte-neuron cocultures. Because microglia do not express the classical Pgr, we examined the role of Pgrmc1, which is expressed in microglia in vitro and in vivo. Knockdown by siRNA-Pgrmc1 in microglia before add-back to astrocyte-neuron cocultures suppressed the P4-E2 antagonism of neurite outgrowth. Conditioned media from microglia restored the P4-E2 activity, but only if microglia were activated by lipopolysaccharide or by wounding. Moreover, the microglial activation was blocked by Pgmrc1-siRNA knockdown. These findings explain why nonwounded cultures without microglial activation lack P4 antagonism of E2-induced neurite outgrowth. We suggest that microglial activation may influence brain responses to exogenous P4, which is a prospective therapy in traumatic brain injury.

Progesterone receptor membrane component 1 as the mediator of the inhibitory effect of progestins on cytokine-induced matrix metalloproteinase 9 activity in vitro

Progesterone (P4) and the progestin, 17α-hydroxyprogesterone caproate, are clinically used to prevent preterm births (PTBs); however, their mechanism of action remains unclear. Cytokine-induced matrix metalloproteinase 9 (MMP-9) activity plays a key role in preterm premature rupture of the membranes and PTB. We demonstrated that the primary chorion cells and the HTR8/SVneo cells (cytotrophoblast cell line) do not express the classical progesterone receptor (PGR) but instead a novel progesterone receptor, progesterone receptor membrane component 1 (PGRMC1), whose role remains unclear. Using HTR8/SVneo cells in culture, we further demonstrated that 6 hours pretreatment with medroxyprogesterone acetate (MPA) and dexamethasone (Dex) but not P4 or 17α-hydroxyprogesterone hexanoate significantly attenuated tumor necrosis factor α-induced MMP-9 activity after a 24-hour incubation period. The inhibitory effect of MPA, but not Dex, was attenuated when PGRMC1 expression was successfully reduced by PGRMC1 small interfering RNA. Our findings highlight a possible novel role of PGRMC1 in mediating the effects of MPA and in modulating cytokine-induced MMP-9 activity in cytotrophoblast cells in vitro.

Progesterone receptor membrane component 1 and its role in ovarian follicle growth

Progesterone (P4) is synthesized in the ovary and acts directly on granulosa cells of developing ovarian follicles to suppress their rate of mitosis and apoptosis. Granulosa cells do not express nuclear progesterone receptor (PGR) but rather progesterone receptor membrane component-1 (PGRMC1). PGRMC1 binds P4 and mediates P4's actions, as evidenced by PGRMC1 siRNA studies. PGRMC1 acts by binding plasminogen activator inhibitor 1 RNA-binding protein and regulating gene expression. Specifically, PGRMC1 suppresses some genes that promote cell death (i.e., Bad, Caspase-3, Caspase-4). P4 regulates gene expression in part by inhibiting PGRMC1 binding to Tcf/Lef transcription sites, thereby reducing Tcf/Lef transcriptional activity. Since Tcf/Lef transcription sites are located within the promoters of genes that initiate mitosis and/or apoptosis (i.e., c-jun and c-myc), P4-PGRMC1 mediated suppression of these Tcf/Lef regulated genes could account for P4's actions. PGRMC1 expression is also altered in women with polycystic ovarian syndrome, premature ovarian failure and infertility. Collectively, these observations support a role for PGRMC1 in regulating human ovarian follicle development.

Plasminogen activator inhibitor 1 RNA-binding protein interacts with progesterone receptor membrane component 1 to regulate progesterone's ability to maintain the viability of spontaneously immortalized granulosa cells and rat granulosa cells

Progesterone receptor membrane component 1 (PGRMC1) mediates the antiapoptotic action of progesterone (P4). PGRMC1 interacts with plasminogen activator inhibitor 1 RNA-binding protein (PAIRBP1), but the functional significance of this interaction is unknown. To examine the function of PGRMC1-PAIRBP1 interaction, PAIRBP1 was depleted from spontaneously immortalized granulosa cells (SIGCs) and the effects on the expression and localization of PGRMC1 as well as P4's ability to bind to SIGCs and prevent apoptosis was assessed. Depleting PAIRBP1 enhanced cellular (3)H-P4 binding and did not alter the expression or cellular localization of PGRMC1 but attenuated P4's antiapoptotic action. Transfection of a PGRMC1-green fluorescent protein (GFP) peptide mimic, which binds PAIRBP1 as demonstrated by in situ proximity assay, doubled the rate at which SIGCs undergo apoptosis compared to cells transfected with either the empty GFP expression vector or Pairbp1 small interfering RNA. Moreover, P4 did not prevent these cells from undergoing apoptosis. Similar studies conducted with granulosa cells isolated from immature rats also showed that PGRMC1 interacts with PAIRBP1 and that transfection of PGRMC1-GFP peptide mimic accelerates the rate of granulosa cell apoptosis by 4-fold even in the presence of serum and P4. These studies support the concept that the interaction between PAIRBP1-PGRMC1 is an essential component of the mechanism through which P4 inhibits apoptosis. Surprisingly, PGRMC1-PAIRBP1 interaction is not required for P4 binding or the cellular localization of PGRMC1 but rather appears to couple PGRMC1 to downstream components of the P4-PGRMC1 signal transduction pathway.

Progesterone increases the release of brain-derived neurotrophic factor from glia via progesterone receptor membrane component 1 (Pgrmc1)-dependent ERK5 signaling

Progesterone (P4) is cytoprotective in various experimental models, but our understanding of the mechanisms involved is still incomplete. Our laboratory has implicated brain-derived neurotrophic factor (BDNF) signaling as an important mediator of P4's protective actions. We have shown that P4 increases the expression of BDNF, an effect mediated by the classical P4 receptor (PR), and that the protective effects of P4 were abolished using inhibitors of Trk receptor signaling. In an effort to extend our understanding of the interrelationship between P4 and BDNF signaling, we determined whether P4 influenced BDNF release and examined the role of the classical PR and a putative membrane PR, progesterone receptor membrane component-1 (Pgrmc1), as mediators of this response. Given recent data from our laboratory that supported the role of ERK5 in BDNF release, we also tested whether P4-induced BDNF release was mediated by ERK5. In this study, we found that P4 and the membrane-impermeable P4 (P4-BSA) both induced BDNF release from cultured C6 glial cells and primary astrocytes. Both these cells lack the classical nuclear/intracellular PR but express high levels of membrane-associated PR, including Pgrmc1. Using RNA interference-mediated knockdown of Pgrmc1 expression, we determined that P4-induced BDNF release was dependent on the expression of Pgrmc1, although pharmacological inhibition of the PR failed to alter the effects of P4. Furthermore, the BDNF release elicited by P4 was mediated by ERK5, and not ERK1/2. Collectively, our data describe that P4 elicits an increase in BDNF release from glia via a Pgrmc1-induced ERK5 signaling mechanism and identify Pgrmc1 as a potential therapeutic target for future hormone-based drug development for the treatment of such degenerative diseases as Alzheimer's disease as well as other diseases wherein neurotrophin dysregulation is noted.