Progesterone receptor membrane component 1: an integrative review

Possible role of PGRMC1 in breast cancer development

Hormone therapy may increase the risk of breast cancer. Thus, especially the addition of synthetic progestins may play a decisive role according to the results of clinical studies. Overexpression of a special receptor, i.e. the progesterone receptor membrane component-1 (PGRMC1), may offer a potential new pathway to explain the observed increase in breast cancer risk in the combined arm of the Women's Health Initiative. PGRMC1 is expressed in breast cancer tissue and may be important in tumorigenesis. The expression of PGRMC1 in breast cancer tissue is significantly different from that in normal mammary glands. Certain synthetic progestins can increase the proliferation of PGRMC1-overexpressing breast cancer cells and may thus be involved in tumorigenesis, while progesterone and certain synthetic progestins such as nomegestrol or chlormadinone acetate react neutrally. Our investigations point towards an important role of estrogen receptor-α in the signaling cascade, resulting in the proliferative effect induced by progestins. Thus, activation of PGRMC1 may explain the increased breast cancer risk observed during treatment with certain progestins. Very recently, PGRMC1 was investigated in serum samples of lung cancer patients and matched healthy patients; significantly higher concentrations were shown in the cancer patients. Therefore, PGRMC1 might be a predictor for other cancers as well but, according to clinical trials, its importance for a possible screening tool, particularly for breast cancer risk during hormone therapy, seems of interest.

PGRMC2, a yet uncharacterized protein with potential as tumor suppressor, migration inhibitor, and regulator of cytochrome P450 enzyme activity

PGRMC2 (progesterone receptor membrane component 2) is highly homologous if compared with PGRMC1, a cytochrome-related protein, which is induced in several cancers and linked to cell growth in these cancers. Further it seems to be involved in progesterone signalling and cytochrome P450 binding. For PGRMC2 only sparse information is available. Recent data show that PGRMC1 and 2 share several similar characteristics, but there are also important differences in expression and function of the both proteins. Several findings point to the fact that PGRMC2 might play a role in cancer as well. The protein influences the migration rate of ovarian cancer cells and a loss of PGRMC2 might result in higher metastasis rates. In contrast to PGRMC1 it seems more likely to act as a tumor suppressor than a promoter. Altered PGRMC2 expression was further detected in the context of term and preterm labour, though the implications of this finding are currently unknown and need further examination. PGRMC2 further might play a role in gynaecologic diseases like preterm labour and endometriosis. PGRMC2 shares the cellular localisation and the ability to bind cytochrome enzymes with PGRMC1. Further the protein was shown to influence the activity of CYP3A4. In conclusion, though not much is known about PGRMC2 so far, it deserves further examination as data point to a role of PGRMC2 as tumor suppressor, migration inhibitor and regulator of cytochrome P450 proteins.

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.

Expression of progesterone receptor membrane component (PGRMC) 1 and 2, serpine mRNA binding protein 1 (SERBP1) and nuclear progesterone receptor (PGR) in the bovine endometrium during the estrous cycle and the first trimester of pregnancy

Progesterone (P4) is involved in the regulation of essential reproductive functions affecting the target cells through both nuclear progesterone receptors (PGRs) and membrane progesterone receptors. The aim of this study was to determine the mRNA and protein expression for PGRMC1, PGRMC2, SERBP1 and PGR within the bovine endometrium during the estrous cycle and the first trimester of pregnancy. There were no changes in PGRMC1 and PGRMC2 mRNA and protein expression during the estrous cycle, however, mRNA levels of PGRMC1 and PGRMC2 were increased (P<0.001) in pregnant animals. SERBP1 mRNA expression was increased (P<0.05), while the level of this protein was decreased (P<0.05) on days 11-16 of the estrous cycle. The expression of PGR mRNA was higher (P<0.01) on days 17-20 compared to days 6-10 and 11-16 of the estrous cycle and pregnancy. PGR-A and PGR-B protein levels were elevated on days 1-5 and 17-20 of the estrous cycle as compared to other stages of the cycle and during pregnancy. In conclusion, our results indicate that P4 may influence endometrial cells through both genomic and nongenomic way. This mechanism may contribute to the regulation of the estrous cycle and provide protection during pregnancy.

Do mollusks use vertebrate sex steroids as reproductive hormones? Part I: Critical appraisal of the evidence for the presence, biosynthesis and uptake of steroids

The consensus view is that vertebrate-type steroids are present in mollusks and perform hormonal roles which are similar to those that they play in vertebrates. Although vertebrate steroids can be measured in molluscan tissues, a key question is 'Are they formed endogenously or they are picked up from their environment?'. The present review concludes that there is no convincing evidence for biosynthesis of vertebrate steroids by mollusks. Furthermore, the 'mollusk' genome does not contain the genes for key enzymes that are necessary to transform cholesterol in progressive steps into vertebrate-type steroids; nor does the mollusk genome contain genes for functioning classical nuclear steroid receptors. On the other hand, there is very strong evidence that mollusks are able to absorb vertebrate steroids from the environment; and are able to store some of them (by conjugating them to fatty acids) for weeks to months. It is notable that the three steroids that have been proposed as functional hormones in mollusks (i.e. progesterone, testosterone and 17β-estradiol) are the same as those of humans. Since humans (and indeed all vertebrates) continuously excrete steroids not just via urine and feces, but via their body surface (and, in fish, via the gills), it is impossible to rule out contamination as the sole reason for the presence of vertebrate steroids in mollusks (even in animals kept under supposedly 'clean laboratory conditions'). Essentially, the presence of vertebrate steroids in mollusks cannot be taken as reliable evidence of either endogenous biosynthesis or of an endocrine role.

Nomegestrol acetate sequentially or continuously combined to estradiol did not negatively affect membrane-receptor associated progestogenic effects in human breast cancer cells

OBJECTIVES

Recently the first monophasic contraceptive pill containing estradiol has been developed which is thought to be a milestone in contraception. Nomegestrol acetate (NOM) is the progestogenic component. Progesterone receptor membrane component 1 (PGRMC1) is highly expressed in the tissue of breast cancer patients, and can predict a progestogen dependent risk of breast cancer.

METHODS

MCF-7 cells were transfected with PGRMC1 expression plasmid, and were stimulated with estradiol (E2, 10(-12) and 10(-10) M). NOM, progesterone (P), medroxyprogesterone acetate (MPA) and norethisterone (NET) (each 10(-7) M) were added sequentially or continuously.

RESULTS

E2 at 10(-10) M elicited a significant increase of cell proliferation from 150 to 200%. No effect was seen at 10(-12) M. Addition of the progestogens to E2 at 10(-10) M had no significant effect. However, at an E2 10(-12) M, NET significantly stimulated cell proliferation more pronounced in the continuous combined model. No effect was seen for NOM, P and MPA. The E2/NET combined effect could be abrogated by the addition of an estrogen receptor (ER) antagonist.

CONCLUSION

Since NOM did not increase proliferation it may be concluded that it will be neutral in terms of breast cancer risk when combined with E2 at least in women overexpressing PGRMC1.

Expression of nuclear progesterone receptor and progesterone receptor membrane components 1 and 2 in the oviduct of cyclic and pregnant cows during the post-ovulation period

BACKGROUND

Progesterone (P4) may modulate oviductal functions to promote early embryo development in cattle. In addition to its nuclear receptor (PR), P4 may mediate its actions through P4 receptor membrane component 1 (PGRMC1) and its relative, PGRMC2. Two successive experiments were undertaken to characterise the expression of PR, PGRMC1 and PGRMC2 in the bovine oviduct during the post-ovulation period, and to relate their expression to the presence of an embryo, the proximity of the CL and to the region of the oviduct.

METHODS

In the first experiment (Exp. I), whole oviduct sections were collected from Holstein cows at Day 1.5, Day 4 and Day 5 post-ovulation (n = 2 cows per stage). The expression of PR, PGRMC1 and PGRMC2 was studied in the ampulla and isthmus by RT-PCR, western-blot and immunohistochemistry. In Exp. II, oviduct epithelial cells were collected from cyclic and pregnant Charolais cows (n = 4 cows per status) at Day 3.5 post-ovulation and mRNA expression of PR, PGRMC1 and PGRMC2 was examined in the ampulla and isthmus by real-time quantitative PCR.

RESULTS

In Exp. I, PR, PGRMC1 and PGRMC2 were expressed in all oviduct samples. PGRMC1 was mainly localised in the luminal epithelium whereas PR and PGRMC2 were localised in the epithelium as well as in the muscle and stroma layers of the oviduct. The expression was primarily nuclear for PR, primarily cytoplasmic for PGRMC1 and both nuclear and cytoplasmic for PGRMC2. In Exp. II, mRNA levels for PR, PGRMC1 and PGRMC2 were not affected by either the pregnancy status or the side relative to the CL. However, the expression of PR and PGRMC2 varied significantly with the region of the oviduct: PR was more highly expressed in the isthmus whereas PGRMC2 was more highly expressed in the ampulla.

CONCLUSIONS

This is the first evidence of PGRMC2 expression in the bovine oviduct. Our findings suggest that P4 regulates the functions of the bovine oviduct in a region-specific manner and through both classical and non classical pathways during the post-ovulation period.

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.

Progesterone suppresses the mTOR pathway and promotes generation of induced regulatory T cells with increased stability

While induced FoxP3(+) T cells (iTreg cells) are promising cellular therapeutics to treat inflammatory diseases, a limitation in utilizing iTreg cells prepared in vitro is their low stability in inflammatory conditions. Progesterone (P4) is an immune regulatory nuclear hormone with a potent Treg induction activity. We reasoned that this function of progesterone would be utilized to generate iTreg cells with highly suppressive activity and improved stability in vivo. Here we generated iTreg cells with progesterone in vitro and found that progesterone generates iTreg cells that are highly stable in inflammatory conditions. Moreover, P4-induced iTreg cells highly express latency-associated peptide TGF-β1 and are efficient in regulating inflammation in multiple tissues, whereas control iTreg cells induced with TGF-β1 alone are less stable and ineffective in suppressing inflammation. The function of progesterone in inducing iTreg cells with improved regulatory activity is associated with the function of P4 in suppressing the mTOR pathway. Moreover, the function of progesterone in inducing FoxP3(+) T cells is decreased but not completely abolished on nuclear progesterone receptor-deficient T cells, suggesting that both nuclear and nonnuclear progesterone receptors are involved in mediating the function. We conclude that P4 can be utilized to generate iTreg cells with a high therapeutic potential in treatment of tissue inflammation.

The non-genomic rapid acidification in peripheral T cells by progesterone depends on intracellular calcium increase and not on Na+/H+-exchange inhibition

Progesterone is an endogenous immunomodulator that is able to suppress T cell activation during pregnancy. An increased intracellular free calcium concentration ([Ca(2+)](i)), acidification, and an inhibition of Na(+)/H(+)-exchange 1 (NHE1) are associated with this progesterone rapid non-genomic response that involves plasma membrane sites. Such acidification, when induced by phytohemagglutinin, is calcium dependent in PKC down-regulated T cells. We investigated the relationship between this rapid response involving the [Ca(2+)](i) increase and various membrane progesterone receptors (mPRs). In addition, we explored whether the induction of acidification in T cells by progesterone is a direct result of the [Ca(2+)](i) increase. The results show that the intracellular calcium elevation caused by progesterone is inhibited by SKF96365, U73122, and 2-APB, but not by pertussis toxin or U73343. The elevation is enhanced by the protein tyrosine kinase inhibitor staurosporine and the protein kinase C inhibitors Ro318220 and Go6983. These findings suggest that progesterone does not stimulate the [Ca(2+)](i) increase via the Gi coupled mPR(α). Furthermore, progesterone-induced acidification was found to be dependent on Ca(2+) entry and blocked by the inorganic channel blocker, Ni(2+). However, BAPTA, an intracellular calcium chelator, was found to prevent progesterone-induced acidification but not the inhibition of NHE1. This implies that acidification by progesterone is a direct result of the [Ca(2+)](i) increase and does not directly involve NHE1. Taken together, further investigations are needed to explore whether one or more mPRs or PGRMC1 are involved in bringing about the T cell rapid response that results in the [Ca(2+)](i) increase and inhibition of NHE1.

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

Progesterone receptor membrane component 1 (PGRMC1) is highly expressed in the granulosa and luteal cells of rodent and primate ovaries. Interestingly, its molecular weight as assessed by Western blot is dependent on its cellular localization with a ≈27kDa form being detected in the cytoplasm and higher molecular weight forms being detected in the nucleus. The higher molecular weight forms of PGRMC1 are sumoylated suggesting that they are involved in regulating gene transcription, since sumoylation of nuclear proteins often is associated with regulation of transcriptional activity of the sumoylated protein. In order to identify a set of candidate genes that are regulated by PGRMC1, a human granulosa/luteal cell line (hGL5 cells) was treated with PGRMC1 siRNA and changes in gene expression monitored by microarray analysis. The microarray analysis revealed that PGRMC1 generally functioned as a repressor of transcription, since depletion of PGRMC1 resulted in a disproportionate increase in the number of transcripts. Moreover, a pathway analysis implicated PGRMC1 in the regulation of apoptosis, which is consistent with PGRMC1's known biological action. More importantly these results support the concept that PGRMC1 influences gene transcription. Additional studies reveal that progesterone (P4) acting through a PGRMC1-dependent mechanism suppresses the activity of the transcription factor, Tcf/Lef, thereby identifying one molecular pathway through which P4-PGRMC1 can regulate gene transcription and ultimately apoptosis.

Therapeutic targeting of pancreatic cancer utilizing sigma-2 ligands

One major barrier in the development of pancreas cancer therapeutics is the selective delivery of the drugs to their cellular targets. We have previously developed several sigma-2 ligands and reported the discovery of a component of the receptor for these ligands. Several sigma-2 ligands have been shown to trigger apoptosis in pancreas cancer cells. More importantly, sigma-2 ligands are internalized rapidly by the cancer cells and are capable of delivering other small-molecule therapeutics. Here we review sigma-2 ligands and conjugates as a potential novel therapy suitable for investigation in patients with pancreatic cancer.

E3-independent ubiquitination of AtMAPR/MSBP1

AtMAPR5/MSBP1 and its homologs can be ubiquitinated in the absence of E3 ligase in in vitro ubiquitination assays. Ubiquitinated AtMAPR3, AtMAPR5/MSBP1, and AtMAPR2 were identified using LC-MS/MS. Analysis of trypsin-released signature peptides showed that this E3-independent ubiquitination of AtMAPR3, AtMAPR5/MSBP1, and AtMAPR2 was dominated by mono-ubiquitination at multiple sites. Unlike AtUBC8-type E2s, AtUBC36 was not able to transfer ubiquitin to AtMAPR2. The truncated mutants AtMAPR2Δ1-10, AtMAPR2Δ1-30, and AtMAPR2_1-73 could also be ubiquitinated. The presence of a ubiquitin-binding domain (UBD) allows proteins to be ubiquitinated independently of E3 ligases. However, AtMAPRs do not contain any known UBD. In vitro ubiquitination of AtMAPR2 observed in this study will be further studied in biochemical and physiological aspects.

Progestogens and membrane-initiated effects on the proliferation of human breast cancer cells

OBJECTIVES

Evidence is accumulating that progestogens may play a crucial role in the development of breast cancer under contraception and hormone therapy in reproductive and menopausal women. Progesterone receptor membrane component 1 (PGRMC1) expressed in breast cancer may be important in tumorigenesis and thus may increase breast cancer risk. The aim of this project was to investigate the influence of progesterone and nine synthetic progestins on MCF-7 breast cancer cells overexpressing PGRMC1.

METHODS

MCF-7 cells were stably transfected with PGRMC1 expression plasmid (WT-12). To test the effects of progestogerone (P) and the synthetic progestins chlormadinone acetate (CMA), desogestrel (DSG), drospirenone (DRSP), dydrogesterone (DYD), levonorgestrel (LNG), medroxyprogesterone acetate (MPA), nomegestrol (NOM) and norethisterone (NET) on cell proliferation, MCF-7 and WT-12 cells were stimulated with different concentrations (0.01-1 µmol/l).

RESULTS

In MCF-7 cells, DRSP, DSG, DYD, LNG and NET increased the proliferation at 1 µmol/l, the effect being highest for NET with about 20%. In WT-12 cells, the same progestins, but additionally MPA, showed a significant increase, which was much higher (30-245%) than in MCF-7 cells. Here again, NET showed the highest proliferative effect. No effect was found for CMA, NOM and P.

CONCLUSION

Some synthetic progestins trigger a proliferative response of PGRMC1-overexpressed MCF-7 cancer cells. The effect of progestogens on breast cancer tumorigenesis may clearly depend on the specific pharmacology of the various synthetic progestins.

Alterations in progesterone receptor membrane component 2 (PGRMC2) in the endometrium of macaques afflicted with advanced endometriosis

The hormonally driven expression and cell-specific localization patterns of the progesterone receptor membrane components (PGRMC1 and PGRMC2) in the macaque endometrium during the menstrual cycle are unknown. Additionally, the expression and localization patterns of PGRMC1 and PGRMC2 in the secretory eutopic endometrium of primates afflicted with endometriosis are also unknown. Therefore, we used real-time PCR to quantify transcript expression levels of the PGRMCs in well-defined samples of endometrium collected from artificially cycled macaques during the menstrual cycle, and in the secretory phase endometrium of naturally cycling macaques afflicted with endometriosis. In situ hybridization and immunocytochemistry were used to localize PGRMC1 and PGRMC2 mRNA and protein, respectively. We compared the patterns of expression and localization of the PGRMCs with the expression and localization patterns of nuclear progesterone receptor (PGR). PGRMC1 and PGR were elevated during the proliferative phases of the cycle, and then declined to nearly undetectable levels during the late secretory phase of the cycle. Levels of PGRMC2 were lowest during the proliferative phases of the cycle and then increased markedly during the secretory phases. Strong staining for PGRMC2 was localized to the luminal and glandular epithelia during the secretory phases. When compared with artificially cycled disease-free animals, macaques with endometriosis exhibited no changes in the expression or localization patterns for PGR and PGRMC1 but exhibited strikingly reduced levels of PGRMC2 transcript and altered intracellular staining patterns for the PGRMC2 protein. Collectively, these results suggest that membrane-bound PGRMC2 may provide a pathway of action that could potentially mediate the non-genomic effects of progesterone on the glandular epithelia during the secretory phase of the cycle. Further, reduced levels of membrane-bound PGRMC2 may be associated with the progesterone insensitivity often observed in the endometrium of primates afflicted with endometriosis.

Differential responses of progesterone receptor membrane component-1 (Pgrmc1) and the classical progesterone receptor (Pgr) to 17β-estradiol and progesterone in hippocampal subregions that support synaptic remodeling and neurogenesis

Progesterone (P4) and estradiol (E2) modulate neurogenesis and synaptic remodeling in the hippocampus during the rat estrous cycle and in response to deafferenting lesions, but little is known about the steroidal regulation of hippocampal progesterone receptors associated with these processes. We examined the neuronal expression of progesterone receptor membrane component-1 (Pgrmc1) and the classical progesterone receptor (Pgr), by in situ hybridization and immunohistochemistry. Pgr, a transcription factor, has been associated with synaptic remodeling and other major actions of P4, whereas Pgrmc1 is implicated in P4-dependent proliferation of adult neuroprogenitor cells and with rapid P4 effects on membranes. Ovariectomized adult rats were given E2, P4, or E2+P4 on two schedules: a 4-d model of the rodent estrous cycle and a 30-d model of postmenopausal hormone therapy. Pgr was hormonally responsive only in CA1 pyramidal neurons, and the induction of Pgr by E2 was partly antagonized by P4 only on the 30-d schedule. In CA3 pyramidal and dentate gyrus (DG) neurons, Pgr was largely unresponsive to all hormone treatments. In contrast to Pgr, Pgrmc1 was generally induced by E2 and/or P4 throughout the hippocampus in CA1, CA3, and DG neurons. In neuroprogenitor cells of the DG (immunopositive for bromodeoxyuridine and doublecortin), both Pgrmc1 and Pgr were detected. The differential regulation of hippocampal Pgrmc1 and Pgr by E2 and P4 may guide drug development in hormonal therapy for support of neurogenesis and synaptic regeneration.

Rapid steroid hormone actions initiated at the cell surface and the receptors that mediate them with an emphasis on recent progress in fish models

In addition to the classic genomic mechanism of steroid action mediated by activation of intracellular nuclear receptors, there is now extensive evidence that steroids also activate receptors on the cell surface to initiate rapid intracellular signaling and biological responses that are often nongenomic. Recent progress in our understanding of rapid, cell surface-initiated actions of estrogens, progestins, androgens and corticosteroids and the identities of the membrane receptors that act as their intermediaries is briefly reviewed with a special emphasis on studies in teleost fish. Two recently discovered novel proteins with seven-transmembrane domains, G protein-coupled receptor 30 (GPR30), and membrane progestin receptors (mPRs) have the ligand binding and signaling characteristics of estrogen and progestin membrane receptors, respectively, but their functional significance is disputed by some researchers. GPR30 is expressed on the cell surface of fish oocytes and mediates estrogen inhibition of oocyte maturation. mPRα is also expressed on the oocyte cell surface and is the intermediary in progestin induction of oocyte maturation in fish. Recent results suggest there is cross-talk between these two hormonal pathways and that there is reciprocal down-regulation of GPR30 and mPRα expression by estrogens and progestins at different phases of oocyte development to regulate the onset of oocyte maturation. There is also evidence in fish that mPRs are involved in progestin induction of sperm hypermotility and anti-apoptotic actions in ovarian follicle cells. Nonclassical androgen and corticosteroid actions have also been described in fish models but the membrane receptors mediating these actions have not been identified.

Membrane progesterone receptors: evidence for neuroprotective, neurosteroid signaling and neuroendocrine functions in neuronal cells

Membrane progesterone receptors (mPRs) are novel G protein-coupled receptors belonging to the progestin and adipoQ receptor family (PAQR) that mediate a variety of rapid cell surface-initiated progesterone actions in the reproductive system involving activation of intracellular signaling pathways (i.e. nonclassical actions). The mPRs are highly expressed in the brain, but research on their neural functions has only been conducted in a single neuronal cell line, GT1-7 cells, which have negligible nuclear progesterone receptor (PR) expression. GT1-7 cells express mPRα and mPRβ on their plasma membranes which is associated with the presence of high-affinity, specific [(3)H]-progesterone receptor binding. The neurosteroid, allopregnanolone, is an effective ligand for recombinant mPRα with a relative binding affinity of 7.6% that of progesterone. Allopregnanolone acts as a potent mPR agonist on GT1-7 cells, mimicking the progesterone-induced decrease in cAMP accumulation and its antiapoptotic actions at low nanomolar concentrations. The decrease in cAMP levels is associated with rapid progesterone-induced downregulation of GnRH pulsatile secretion from perifused GT1-7 cells. The recent suggestion that mPRs are alkaline ceramidases and mediate sphingolipid signaling is not supported by empirical evidence that TNFα does not bind to mPRs overexpressed in human cells and that exogenous sphingomyelinase is ineffective in mimicking progestin actions through mPRs to induce meiotic maturation of fish oocytes. Taken together, these recent studies indicate that mPRs mediate neuroprotective effects of progesterone and allopregnanolone and are also the likely intermediaries in progesterone-induced inhibition of pulsatile GnRH secretion in GT1-7 cells.

The presence of a membrane-bound progesterone receptor sensitizes the estradiol-induced effect on the proliferation of human breast cancer cells

OBJECTIVE

Breast cancer risk is still an important topic regarding hormone therapy as well as oral contraception. Evidence that progestogens may play a crucial role is accumulating. Progesterone receptor membrane component 1 (PGRMC1) expressed in breast cancer may be important in tumorigenesis and thus may increase breast cancer risk. The aim of this project was to investigate the influence of different estradiol (E2) concentrations and the addition of two progestogens on MCF-7 breast cancer cells overexpressing PGRMC1.

METHODS

MCF-7 cells were stably transfected with PGRMC1 expression plasmid (MCF-7/PGRMC1-3HA [WT-12]). To test the effects of E2 and progestogens on cell proliferation, MCF-7 and WT-12 cells were stimulated with different concentrations of E2 (10 and 10 M) alone and in combination with progesterone and medroxyprogesterone acetate (each 10 M).

RESULTS

E2 elicited a concentration-dependent proliferative effect on both cell lines, which was much more pronounced in WT-12 cells (50% vs 200%). This effect could be completely abrogated by the addition of the E2 antagonist fulvestrant. Addition of progesterone had no influence on the E2-induced effect, whereas medroxy-progesterone acetate enhanced the E2-induced effect at a low E2 concentration, which was, again, more pronounced in the WT-12 cells. The figures were between 20% and 40% in MCF-7 and between 60% and 250% in WT-12 cells.

CONCLUSIONS

Overexpression of PGRMC1 sensitizes the proliferative response of the MCF-7 breast cancer cell line to estradiol. The effect of progestogens on breast cancer tumorigenesis may depend on the specific progestogen used for hormone therapy or oral contraception.

Elevated progesterone receptor membrane component 1/sigma-2 receptor levels in lung tumors and plasma from lung cancer patients

Cancer is one of the leading causes of death, and there is an urgent need for new biomarkers and therapeutic targets. The progesterone receptor membrane component 1 (Pgrmc1) protein is upregulated in multiple types of cancer, and Pgrmc1 is required for tumor cell proliferation, motility and tumor formation in vivo. Furthermore, a small molecule inhibitor of Pgrmc1 suppressed the growth of lung, breast and cervical cancer cell lines. Recently, Pgrmc1 was identified as the sigma-2 receptor, a putative type of opioid receptor, and sigma-2 receptors are induced in cancers. However, Pgrmc1 shares no homology with known opioid or hormone receptors but is related to cytochrome b(5), and Pgrmc1 binds to heme and has reducing activity. In this study, we have analyzed Pgrmc1 levels in clinical tumor samples from squamous cell lung cancers (SCLC) and lung adenocarcinomas compared to corresponding nonmalignant tissue. Pgrmc1 levels increased significantly (p ≤ 0.05) in 12/15 SCLC samples and was elevated in poorly differentiated tumors. Pgrmc1 was highly expressed in SCLC cell lines, and SCLC cell survival was inhibited by siRNA knockdown of Pgrmc1 or the Pgrmc1 inhibitor AG-205. In adenocarcinomas, 6/15 tumors significantly had elevated Pgrmc1 levels, which correlated with patient survival. Pgrmc1 localizes to secretory vesicles in cancer cells, and Pgrmc1 was secreted by lung cancer cells. Furthermore, Pgrmc1 was significantly elevated in the plasma of lung cancer patients compared to noncancer patients. Together, the results demonstrate that Pgrmc1 is a potential tumor and serum biomarker, as well as a therapeutic target, for lung cancer.

Differential and interactive effects of ligand-bound progesterone receptor A and B isoforms on tyrosine hydroxylase promoter activity

The classical progesterone receptors (PRs) are expressed in some hypothalamic dopaminergic and brainstem noradrenergic neurones. Progesterone influences prolactin and luteinising hormone release from the anterior pituitary gland, in part by regulating the activity of these catecholaminergic neurones. The present study aimed to determine the effects of PRs on tyrosine hydroxylase (TH) promoter activity. When CAD, SK-N-SH and CV-1 cells were transfected with TH promoter constructs and PR-A or PR-B expression vectors, progesterone treatment caused three- to six-fold increases in TH-9.0 kb promoter activity in PR-B expressing cells, although only a modest increase or no change in PR-A expressing cells. Using CAD cells, deletional analysis mapped the site of PR action to the -1403 to -1304 bp region of the TH promoter. Mutational analysis of putative regulatory sequences in this region indicated that multiple DNA elements are required for complete PR-B transactivation. Electrophoretic mobility shift assays were unable to demonstrate direct PR-B binding to TH promoter DNA sequences. However, chromatin immunoprecipitation analysis indicated PR-B was recruited to the TH promoter. Two different PR-B DNA binding domain mutants had opposing effects on PR-B-mediated TH promoter activation. A GS to AA mutation located in the p-box of the first zinc finger of PR-B inhibited progesterone transactivation of the TH promoter, whereas a C to A mutation in the zinc finger increased transactivation. PR-A was able to inhibit PR-B transactivation in a dose-dependent manner, although the degree of PR-A inhibition was dependent on the TH promoter deletion construct. These data indicate that ligand-bound PR-B is recruited to DNA elements in the TH promoter and acts as a transcriptional activator of the TH gene, and also that changes in the ratio of PR-A to PR-B may affect the ability of progesterone to increase TH expression.

Expression of progesterone receptor membrane component-1 in bovine reproductive system during estrous cycle

Several reports suggest the participation of progesterone receptor membrane component 1 (PGRMC1) in progesterone signaling in the reproductive system. This study aimed at investigating the presence and localization of PGRMC1 in bovine ovary, oviduct and uterus, during the follicular and luteal phases of the estrous cycle. In the ovary, PGRMC1 has been detected in surface germinal epithelium, granulosa cells, theca cells and in the germinal vesicle of the oocytes at all stages of folliculogenesis. In the corpus luteum the expression of PGRMC1 was influenced by the stage of the estrous cycle. In the oviducts and in the uterus horns, PGRMC1 was immunolocalized in the luminal epithelium, in the muscle layer cells and in the endothelial cells. In the uterus, PGRMC1 was intensely localized also in the glandular endometrium. However, in the oviducts and in the uterus horns, the localization of PGRMC1 was independent on the stage of the estrous cycle and on whether evaluating the ipsilateral or the contralateral organ. In conclusion, the present immunohistochemical study showed that PGRMC1 is located in various compartments of the bovine female reproductive organs. With the exception of the corpora lutea, PGRMC1 localization showed similar pattern during different stages of the estrous cycle.

Progesterone signaling mediated through progesterone receptor membrane component-1 in ovarian cells with special emphasis on ovarian cancer

Various ovarian cell types including granulosa cells and ovarian surface epithelial cells express the progesterone (P4) binding protein, progesterone receptor membrane component-1 (PGRMC1). PGRMC1 is also expressed in ovarian tumors. PGRMC1 plays an essential role in promoting the survival of both normal and cancerous ovarian cell in vitro. Given the clinical significance of factors that regulate the viability of ovarian cancer, this review will focus on the role of PGRMC1 in ovarian cancer, while drawing insights into the mechanism of PGRMC1's action from cell lines derived from healthy ovaries as well as ovarian tumors. Studies using PGRMC1siRNA demonstrated that P4's ability to inhibit ovarian cells from undergoing apoptosis in vitro is dependent on PGRMC1. To confirm the importance of PGRMC1, the ability of PGRMC1-deplete ovarian cancer cell lines to form tumors in intact nude mice was assessed. Compared to PGRMC1-expressing ovarian cancer cells, PGRMC1-deplete ovarian cancer cells formed tumors in fewer mice (80% compared to 100% for controls). Moreover, the number of tumors derived from PGRMC1-deplete ovarian cancer cells was 50% of that observed in controls. Finally, the tumors that formed from PGRMC1-deplete ovarian cancer cells were about a fourth the size of tumors derived from ovarian cancer cells with normal levels of PGRMC1. One reason for PGRMC1-deplete tumors being smaller is that they had a poorly developed microvasculature system. How PGRMC1 regulates cell viability and in turn tumor growth is not known but part of the mechanism likely involves the regulation of genes that promote cell survival and inhibit apoptosis.

Progesterone promotes differentiation of human cord blood fetal T cells into T regulatory cells but suppresses their differentiation into Th17 cells

Progesterone, a key female sex hormone with pleiotropic functions in maintenance of pregnancy, has profound effects on regulation of immune responses. We report in this work a novel function of progesterone in regulation of naive cord blood (CB) fetal T cell differentiation into key T regulatory cell (Treg) subsets. Progesterone drives allogeneic activation-induced differentiation of CB naive, but not adult peripheral blood, T cells into immune-suppressive Tregs, many of which express FoxP3. Compared with those induced in the absence of progesterone, the FoxP3(+) T cells induced in the presence of progesterone highly expressed memory T cell markers. In this regard, the Treg compartment in progesterone-rich CB is enriched with memory-type FoxP3(+) T cells. Moreover, CB APCs were more efficient than their peripheral blood counterparts in inducing FoxP3(+) T cells. Another related function of progesterone that we discovered was to suppress the differentiation of CB CD4(+) T cells into inflammation-associated Th17 cells. Progesterone enhanced activation of STAT5 in response to IL-2, whereas it decreased STAT3 activation in response to IL-6, which is in line with the selective activity of progesterone in generation of Tregs versus Th17 cells. Additionally, progesterone has a suppressive function on the expression of the IL-6 receptor by T cells. The results identified a novel role of progesterone in regulation of fetal T cell differentiation for promotion of immune tolerance.

Identification of the PGRMC1 protein complex as the putative sigma-2 receptor binding site

The sigma-2 receptor, whose gene remains to be cloned, has been validated as a biomarker for tumor cell proliferation. Here we report the use of a novel photoaffinity probe, WC-21, to identify the sigma-2 receptor binding site. WC-21, a sigma-2 ligand containing both a photoactive moiety azide and a fluorescein isothiocyanate group, irreversibly labels sigma-2 receptors in rat liver; the membrane-bound protein was then identified as PGRMC1 (progesterone receptor membrane component-1). Immunocytochemistry reveals that both PGRMC1 and SW120, a fluorescent sigma-2 receptor ligand, colocalizes with molecular markers of the endoplasmic reticulum and mitochondria in HeLa cells. Overexpression and knockdown of the PGRMC1 protein results in an increase and a decrease in binding of a sigma-2 selective radioligand, respectively. The identification of the putative sigma-2 receptor binding site as PGRMC1 should stimulate the development of unique imaging agents and cancer therapeutics that target the sigma-2 receptor/PGRMC1 complex.

Biosynthesis, mode of action, and functional significance of neurosteroids in the purkinje cell

The brain has traditionally been considered to be a target site of peripheral steroid hormones. In addition to this classical concept, we now know that the brain has the capacity to synthesize steroids de novo from cholesterol, the so-called "neurosteroids." In the middle 1990s, the Purkinje cell, an important cerebellar neuron, was identified as a major site for neurosteroid formation in the brain of mammals and other vertebrates. This discovery has provided the opportunity to understand neuronal neurosteroidogenesis in the brain. In addition, biological actions of neurosteroids are becoming clear by the studies using the Purkinje cell, an excellent cellular model, which is known to play an important role in memory and learning processes. Based on the studies on mammals over the past decade, it is considered that the Purkinje cell actively synthesizes progesterone and estradiol from cholesterol during neonatal life, when cerebellar neuronal circuit formation occurs. Both progesterone and estradiol promote dendritic growth, spinogenesis, and synaptogenesis via each cognate nuclear receptor in the developing Purkinje cell. Such neurosteroid actions mediated by neurotrophic factors may contribute to the formation of cerebellar neuronal circuit during neonatal life. 3α,5α-Tetrahydroprogesterone (allopregnanolone), a progesterone metabolite, is also synthesized in the cerebellum and considered to act as a survival factor of Purkinje cells in the neonate. This review summarizes the current knowledge regarding the biosynthesis, mode of action, and functional significance of neurosteroids in the Purkinje cell during development in terms of synaptic formation of cerebellar neuronal networks.

17β-estradiol and progesterone regulate multiple progestin signaling molecules in the anteroventral periventricular nucleus, ventromedial nucleus and sexually dimorphic nucleus of the preoptic area in female rats

Recent work identified novel progestin signaling molecules, including progesterone receptor membrane component 1 (Pgrmc1), Pgrmc2, serpine mRNA binding protein 1 (Serbp1), progestin and adiponectin receptors 7 (Paqr7) and Paqr8. These molecules mediate rapid progesterone (P(4)) effects in non-neural tissue and we recently mapped their expression in the brain. Many rapid effects of P(4) require 17β-estradiol (E(2)) and P(4) priming; therefore, we examined the effects of ovarian hormones on the expression of these non-classical progestin signaling molecules. We focused specifically on the anteroventral periventricular nucleus (AVPV), the sexually dimorphic nucleus of the preoptic area (SDN-POA) and the ventrolateral portion of the ventromedial nucleus (VMNvl). These brain nuclei are important for female reproduction. Ovariectomized adult female rats were implanted with capsules containing sesame oil or E(2), and injected 48 h later with sesame oil or P(4). Brains were collected 8 h later and RNA was isolated from the AVPV, SDN-POA and VMNvl. We assessed the effects of ovarian hormones on mRNA levels using quantitative polymerase chain reaction (QPCR). In the AVPV, Serbp1 mRNA levels were increased by P(4) in the presence of E(2), and Paqr8 was downregulated by P(4) alone. In the SDN-POA, combined E(2) and P(4) increased Pgrmc1 and Serbp1 mRNA levels, and E(2) alone increased Paqr8 mRNA levels. Finally, in the VMNvl, P(4) increased mRNA levels encoding Pgrmc1, Pgrmc2 and Serbp1, and the combination of E(2) and P(4) increased Pgrmc1 and Serbp1 mRNA levels. Paqr7 was not regulated by E(2) or P(4) in any brain region examined. In summary, we showed that ovarian hormones regulate novel progestin signaling molecules in brain regions important for the neuroendocrine control of reproduction.

Progestin signaling through mPRα in Atlantic croaker granulosa/theca cell cocultures and its involvement in progestin inhibition of apoptosis

Although there is substantial evidence that membrane progestin receptors (mPRs) perform a critical physiological role in meiotic maturation of fish oocytes, it is unknown whether they are also intermediaries in progestin signaling in the surrounding follicular cells. Here, we show that mPRα protein is located on the plasma membranes of both granulosa and theca cells (G/T cells) isolated from Atlantic croaker ovaries and is associated with the presence of a single high affinity, limited capacity, pertussis toxin-sensitive, specific progestin [17,20β,21-trihydroxy-4-pregnen-3-one (20β-S)] membrane binding site with the characteristics of mPRα. Treatment of G/T cells with 20β-S caused rapid G protein activation and a transient, pertussis toxin-sensitive, decrease in cAMP levels, whereas the selective nuclear progesterone receptor agonist, R5020, did not cause G protein activation, consistent with previous reports on mPRα signaling. 20β-S treatment decreased serum starvation-induced cell death in both G/T cells and in seatrout mPRα-transfected MDA-MB-231 cells, whereas R5020 was ineffective. Moreover, a selective mPRα agonist, 10-ethenyl-19-norprogesterone, mimicked the protective action of 20β-S against cell death, which was lost upon knockdown of mPRα protein but not after progesterone receptor knockdown, further demonstrating an involvement of mPRα. Signaling molecules involved in inhibition of apoptosis, Erk and serine-threonine kinase, were activated in G/T cells by 20β-S, which suggests a potential mechanism for mPRα inhibition of apoptosis. This is the first study to demonstrate endogenous mPR signaling in the ovarian follicle and to suggest a novel physiological role for mPRα in mediating the antiapoptotic actions of progestins in ovarian follicle cells.

Progesterone receptor membrane component 1 inhibits the activity of drug-metabolizing cytochromes P450 and binds to cytochrome P450 reductase

Progesterone receptor membrane component 1 (PGRMC1) has been shown to interact with several cytochromes P450 (P450s) and to activate enzymatic activity of P450s involved in sterol biosynthesis. We analyzed the interactions of PGRMC1 with the drug-metabolizing P450s, CYP2C2, CYP2C8, and CYP3A4, in transfected cells. Based on coimmunoprecipitation assays, PGRMC1 bound efficiently to all three P450s, and binding to the catalytic cytoplasmic domain of CYP2C2 was much more efficient than to a chimera containing only the N-terminal transmembrane domain. Down-regulation of PGRMC1 expression levels in human embryonic kidney 293 and HepG2 cell lines stably expressing PGRMC1-specific small interfering RNA had no effect on the endoplasmic reticulum localization and expression levels of P450s, whereas enzymatic activities of CYP2C2, CYP2C8, and CYP3A4 were slightly higher in PGRMC1-deficient cells. Cotransfection of cells with P450s and PGRMC1 resulted in PGRMC1 concentration-dependent inhibition of the P450 activities, and this inhibition was partially reversed by increased expression of the P450 reductase (CPR). In contrast, CYP51 activity was decreased by down-regulation of PGRMC1 and expression of PGRMC1 in the PGRMC1-deficient cells increased CYP51 activity. In cells cotransfected with CPR and PGRMC1, strong binding of CPR to PGRMC1 was observed; however, in the presence of CYP2C2, interaction of PGRMC1 with CPR was significantly reduced, suggesting that CYP2C2 competes with CPR for binding to PGRMC1. These data show that in contrast to sterol synthesizing P450, PGRMC1 is not required for the activities of several drug-metabolizing P450s, and its overexpression inhibits those P450 activities. Furthermore, PGRMC1 binds to CPR, which may influence P450 activity.

Urinary collagen fragments are significantly altered in diabetes: a link to pathophysiology

Background

The pathogenesis of diabetes mellitus (DM) is variable, comprising different inflammatory and immune responses. Proteome analysis holds the promise of delivering insight into the pathophysiological changes associated with diabetes. Recently, we identified and validated urinary proteomics biomarkers for diabetes. Based on these initial findings, we aimed to further validate urinary proteomics biomarkers specific for diabetes in general, and particularity associated with either type 1 (T1D) or type 2 diabetes (T2D).

Methodology/Principal Findings

Therefore, the low-molecular-weight urinary proteome of 902 subjects from 10 different centers, 315 controls and 587 patients with T1D (n = 299) or T2D (n = 288), was analyzed using capillary-electrophoresis mass-spectrometry. The 261 urinary biomarkers (100 were sequenced) previously discovered in 205 subjects were validated in an additional 697 subjects to distinguish DM subjects (n = 382) from control subjects (n = 315) with 94% (95% CI: 92–95) accuracy in this study. To identify biomarkers that differentiate T1D from T2D, a subset of normoalbuminuric patients with T1D (n = 68) and T2D (n = 42) was employed, enabling identification of 131 biomarker candidates (40 were sequenced) differentially regulated between T1D and T2D. These biomarkers distinguished T1D from T2D in an independent validation set of normoalbuminuric patients (n = 108) with 88% (95% CI: 81–94%) accuracy, and in patients with impaired renal function (n = 369) with 85% (95% CI: 81–88%) accuracy. Specific collagen fragments were associated with diabetes and type of diabetes indicating changes in collagen turnover and extracellular matrix as one hallmark of the molecular pathophysiology of diabetes. Additional biomarkers including inflammatory processes and pro-thrombotic alterations were observed.

Conclusions/Significance

These findings, based on the largest proteomic study performed to date on subjects with DM, validate the previously described biomarkers for DM, and pinpoint differences in the urinary proteome of T1D and T2D, indicating significant differences in extracellular matrix remodeling.

Molecular cloning and expression of progestin membrane receptor component 1 (Pgmrc1) of the giant tiger shrimp Penaeus monodon

Knowledge on molecular mechanisms of steroid hormonal induction on oocyte development may lead to the possible ways to effectively induce ovarian maturation in shrimp. In this study, progestin membrane receptor component 1 (Pgmrc1) of the giant tiger shrimp (Penaeus monodon) initially identified by EST analysis was further characterized. The full-length cDNA of Pgmrc1 was 2015bp in length containing an ORF of 573bp corresponding to a polypeptide of 190 amino acids. Northern blot analysis revealed a single form of Pgmrc1 in ovaries of P. monodon. Quantitative real-time PCR indicated that the expression level of Pgmrc1 mRNA in ovaries of both intact and eyestalk-ablated broodstock was greater than that of juveniles (P<0.05). Pgmrc1 was up-regulated in mature (stage IV) ovaries of intact broodstock (P<0.05). Unilateral eyestalk ablation resulted in an earlier up-regulation of Pgmrc1 since the vitellogenic (II) ovarian stage. Moreover, the expression level of Pgmrc1 in vitellogenic, early cortical rod and mature (II-IV) ovaries of eyestalk-ablated broodstock was greater than that of the same ovarian stages in intact broodstock (P<0.05). Pgmrc1 mRNA was clearly localized in the cytoplasm of follicular cells, previtellogenic and early vitellogenic oocytes. Immunohistochemistry revealed the positive signals of the Pgmrc1 protein in the follicular layers and cell membrane of follicular cells and various stages of oocytes. Taken the information together, Pgmrc1 gene products seem to play the important role on ovarian development and may be used as the bioindicator for monitoring progression of oocyte maturation of P. monodon.

Progesterone receptor membrane component 1 expression and putative function in bovine oocyte maturation, fertilization, and early embryonic development

Although the mRNA that encodes progesterone receptor membrane component 1 (PGRMC1) is present in mammalian oocytes, nothing is known about either PGRMC1's expression pattern or function in oocytes during maturation, fertilization, and subsequent embryonic development. As PGRMC1 associates with the mitotic spindle in somatic cells, we hypothesized that PGRMC1 is involved in oocyte maturation (meiosis). Western blot analysis confirmed the presence of PGRMC1 in bovine oocytes. This study also shows that PGRMC1 is present at the germinal vesicle (GV)- and MII-stage oocytes and is associated with male and female pronucleus formation of the zygote and is highly expressed in blastocysts. A more detailed examination of PGRMC1 localization using confocal imaging demonstrated that in GV-stage oocytes, PGRMC1 was concentrated throughout the GV but did not localize to the chromatin. With the resumption of meiosis in vitro, PGRMC1 concentrated in the centromeric region of metaphase I chromosomes, while in the anaphase I/telophase I stages the majority of PGRMC1 concentrated between the separating chromosomes. At the metaphase II stage, PGRMC1 re-associated with the centromeric region of the chromosomes. A colocalization study demonstrated that PGRMC1 associated with the phosphorylated form of aurora kinase B, which localizes to the centromeres at metaphase. Finally, PGRMC1 antibody injection significantly lowered the percentage of oocytes that matured and reached the metaphase II stage after 24 h of culture. The majority of the PGRMC1 antibody-injected oocytes arrested in the prometaphase I stage of meiosis. Furthermore, in most of the PGRMC1 antibody-injected oocytes, the chromosomes were disorganized and scattered. Taken together, these data demonstrate that PGRMC1 is expressed in bovine oocytes and its localization changes at specific stages of oocyte maturation. These observations suggest an important role for PGRMC1 in oocyte maturation, which may be specifically related to the mechanism by which chromosomes segregate.

Pgrmc1 (progesterone receptor membrane component 1) associates with epidermal growth factor receptor and regulates erlotinib sensitivity

Tumorigenesis requires the concerted action of multiple pathways, including pathways that stimulate proliferation and metabolism. Epidermal growth factor receptor (EGFR) is a transmembrane receptor-tyrosine kinase that is associated with cancer progression, and the EGFR inhibitors erlotinib/tarceva and tyrphostin/AG-1478 are potent anti-cancer therapeutics. Pgrmc1 (progesterone receptor membrane component 1) is a cytochrome b(5)-related protein that is up-regulated in tumors and promotes cancer growth. Pgrmc1 and its homologues have been implicated in cell signaling, and we show here that Pgrmc1 increases susceptibility to AG-1478 and erlotinib, increases plasma membrane EGFR levels, and co-precipitates with EGFR. Pgrmc1 co-localizes with EGFR in cytoplasmic vesicles and co-fractionates with EGFR in high density microsomes. The findings have therapeutic potential because a Pgrmc1 small molecule ligand, which inhibits growth in a variety of cancer cell types, de-stabilized EGFR in multiple tumor cell lines. EGFR is one of the most potent receptor-tyrosine kinases driving tumorigenesis, and our data support a role for Pgrmc1 in promoting several cancer phenotypes at least in part by binding EGFR and stabilizing plasma membrane pools of the receptor.

Down-regulation of progesterone receptor membrane component 1 (PGRMC1) in peripheral nucleated blood cells associated with premature ovarian failure (POF) and polycystic ovary syndrome (PCOS)

BACKGROUND

Progesterone receptor membrane component 1 (PGRMC1) is a member of a progesterone-binding complex implicated in female reproduction. We aimed i) to determine the natural expression of PGRMC1 in peripheral nucleated blood cells throughout the menstrual cycle and ii) to investigate any association between PGRMC1 levels in leukocytes and conditions characterized by reduced fertility.

METHODS

We analyzed PGRMC1 expression in peripheral leukocytes from 15 healthy cycling women over four weeks. Additionally, we determined PGRMC1 levels in samples from patients with premature ovarian failure (POF) and polycystic ovary syndrome (PCOS) as well as in healthy postmenopausal women and male controls. The levels of PGRMC1 protein in nucleated peripheral blood cells were quantified by Western blot analysis.

RESULTS

PGRMC1 levels did not vary significantly throughout the menstrual cycle. We observed a significant down-regulation of PGRMC1 in postmenopausal women and in patients with premature ovarian failure (POF) and polycystic ovary syndrome (PCOS) when compared to early follicular phase of healthy women.

CONCLUSION

This study suggests that reduced levels of PGRMC1 in peripheral leukocytes are associated with perturbed ovulatory function.

Transcriptional analysis of novel hormone receptors PGRMC1 and PGRMC2 as potential biomarkers of breast adenocarcinoma staging

BACKGROUND

The expression of progesterone receptor membrane component 1 (PGRMC1) in breast cancer has generated interest in this recently discovered protein because of its role in tumorigenesis. However, correlations between patient age, PGRMC1 gene expression, breast cancer morphology, and breast cancer stage have not been adequately studied. Furthermore, very little is known about possible roles for other PGRMC isoforms in breast cancer, like PGRMC2. Thus, we examined the expression of PGRMC1 and PGRMC2 mRNA by relative quantitative PCR (RelqPCR) and determined whether transcript levels correlate with age, breast cancer staging, estrogen receptor alpha (ERα) status, and other morphometric features routinely used during the pathological examination of breast ductal adenocarcinomas.

METHODS

Twenty-eight frozen or paraffin embedded breast cancer samples (ductal carcinoma in situ and stages I thru IV invasive ductal adenocarcinoma) and 10 control benign breast tissue samples were randomly selected and interrogated by RelqPCR to determine PGRMC1, 2, and ERα mRNA transcript levels. To control for slight variations in sample preparation, receptor transcript was normalized to the housekeeping gene phosphoglycerate kinase 1 (PGK1). Descriptive statistics and ANOVA of multiparametric datasets were used to correlate transcript levels with pathological staging parameters.

RESULTS

PGRMC1 mRNA levels decreased significantly with patient age (Pearson's correlation -0.369; P=0.035), whereas PGRMC2 levels did not. Although the mean relative expression of PGRMC1 significantly decreased in stage II breast cancer compared with controls (P=0.050), it was no longer significant when age was considered a covariance (P=0.371). On the other hand, PGRMC2 mRNA transcript was significantly decreased in stage II breast cancer when compared to stage III cancer (P=0.028) in a manner independent of age (corrected model Bonferroni pair wise comparison, P=0.036). Furthermore, PGRMC2 levels positively correlated with ERα mRNA transcripts in patients with ER positive tumors (Pearson's correlation 0.503, P=0.096).

CONCLUSIONS

Decreases in PGRMC1 mRNA are partially explained by increasing patient age. On the other hand, compared to stage III, PCRMC2 mRNA was significantly decreased in stage II adenocarcinoma of the breast in an age-independent manner. Additionally, PGRMC2 mRNA levels displayed a positive correlation with ERα transcripts. Thus, in addition to morphometric pathologic staging criteria, measurements of PGRMC2 mRNA may be useful for distinguishing low stage tumors from higher stages that require more aggressive clinical management, and may be a useful test when tumor ER IHC results are equivocal.

Progesterone inhibits apoptosis in part by PGRMC1-regulated gene expression

Progesterone receptor membrane component-1 (PGRMC1) is present in both the cytoplasm and nucleus of spontaneously immortalized granulosa cells (SIGCs). PGRMC1 is detected as a monomer in the cytoplasm and a DTT-resistant PGRMC1 dimer in the nucleus. Transfected PGRMC1-GFP localizes mainly to the cytoplasm and does not form a DTT-resistant dimer. Moreover, forced expression of PGRMC1-GFP increases the sensitivity of the SIGCs to progesterone (P4)'s anti-apoptotic action, indicating that the PGRMC1 monomer is functional. However, when endogenous PGRMC1 is depleted by siRNA treatment and replaced with PGRMC1-GFP, P4 responsiveness is not enhanced, although overall levels of PGRMC1 are increased. P4's anti-apoptotic action is also attenuated by actinomycin D, an inhibitor of RNA synthesis, and P4 activation of PGRMC1 suppresses Bad and increases Bcl2a1d expression. Taken together, the present studies suggest a genomic component to PGRMC1's anti-apoptotic mechanism of action, which requires the presence of the PGRMC1 dimer.

Progesterone receptor membrane component 1 (Pgrmc1): a heme-1 domain protein that promotes tumorigenesis and is inhibited by a small molecule

Tumorigenesis requires the concerted action of multiple pathways, including pathways that stimulate proliferation and increase metabolism. Progesterone receptor membrane component 1 (Pgrmc1) is related to cytochrome b5, binds to heme, and is associated with DNA damage resistance and apoptotic suppression. Pgrmc1 is induced by carcinogens, including dioxin, and is up-regulated in multiple types of cancer. In the present study, we found that Pgrmc1 increased in vivo tumor growth, anchorage-independent growth, and migration. Pgrmc1 also promoted proliferation in the absence of serum in A549 non-small cell lung cancer cells but enhanced proliferation regardless of serum concentration in MDA-MB-468 breast cancer cells. Pgrmc1 promotes cholesterol synthesis and binds to Insig (insulin-induced gene), Scap (sterol regulatory element binding protein cleavage activating protein), and P450 proteins, but Pgrmc1 did not affect cholesterol synthesis in lung cancer cells. Pgrmc1 is also associated with progesterone signaling and plasminogen activator inhibitor (PAI1) RNA binding protein, but neither progesterone activity nor PAI1 transcript levels were altered in Pgrmc1-knockdown lung cancer cells. Pgrmc1 homologues bind to aryl ligands identified in an in silico screen, and we have found that a Pgrmc1 ligand induced cell death in a Pgrmc1-specific manner in multiple breast and lung tumor cell lines. Our data support a role for Pgrmc1 in promoting cancer-associated phenotypes and provide a therapeutic approach for targeting Pgrmc1 with a small molecule in lung and breast cancer.

Constitutively overexpressed 21 kDa protein in Hodgkin lymphoma and aggressive non-Hodgkin lymphomas identified as cytochrome B5b (CYB5B)

BACKGROUND

We have previously reported a novel constitutively overexpressed 21 kDa protein in Hodgkin Lymphoma (HL) and aggressive Non-Hodgkin Lymphomas (NHL). The objective of the current study was to 1) identify this protein using two independent methods, 2) study the expression of the protein and its encoding mRNA in reactive lymph nodes, normal lymphocytes and CD34+ bone marrow precursor cells, 3) analyse patterns of expression of the protein in tissue microarrays assembled from a large number of diagnostic clinical biopsies from patients with HL, and 4) determine the copy number variation and mutation status of the encoding gene in HL cell lines.

RESULTS

Peptide sequencing by LC-MS/MS and protein identification by protein array screening identified a single protein, CYB5B. No mutations were detected in the CYB5B gene in HL cell lines. Quantitative PCR showed CYB5B gene expression was increased in HL and NHL cell lines. Array CGH using a submegabase resolution tiling array revealed gains in the CYB5B locus in HL cell lines KMH2 and L428. Membrane expression was seen in Reed-Sternberg cells in clinical biopsies from patients with HL but not in reactive lymph nodes. Bone marrow CD34+ precursor cells were CYB5B negative on the cell surface. RT-PCR assays of RNA extracted from T and B cell enriched fractions obtained from normal peripheral blood mononuclear cells, reactive lymph nodes, tonsils and normal bone marrow samples showed no evidence of increased mRNA levels of CYB5B in comparison to housekeeping gene GAPDH.

CONCLUSIONS

The 21 kDa protein overexpressed in HL and aggressive NHL is identical to CYB5B. CYB5B gene expression is increased in a subset of HL and NHL cell lines tested. This is associated with CYB5B gene amplification in HL cell lines KMH2 and L428. CYB5B may be a potential target for antibody-based therapy of HL and aggressive NHL as although cytoplasmic expression is present in reactive lymphocytes, it is not expressed on the cell surface of non-neoplastic lymphocytes or bone marrow precursor cells.

Transcript profiling of candidate genes in testis of pigs exhibiting large differences in androstenone levels

BACKGROUND

Boar taint is an unpleasant odor and flavor of the meat and occurs in a high proportion of uncastrated male pigs. Androstenone, a steroid produced in testis and acting as a sex pheromone regulating reproductive function in female pigs, is one of the main compounds responsible for boar taint. The primary goal of the present investigation was to determine the differential gene expression of selected candidate genes related to levels of androstenone in pigs.

RESULTS

Altogether 2560 boars from the Norwegian Landrace and Duroc populations were included in this study. Testicle samples from the 192 boars with most extreme high or low levels of androstenone in fat were used for RNA extraction, and 15 candidate genes were selected and analyzed by real-competitive PCR analysis. The genes Cytochrome P450 c17 (CYP17A1), Steroidogenic acute regulatory protein (STAR), Aldo-keto reductase family 1 member C4 (AKR1C4), Short-chain dehydrogenase/reductase family member 4 (DHRS4), Ferritin light polypeptide (FTL), Sulfotransferase family 2A, dehydroepiandrosterone-preferring member 1 (SULT2A1), Cytochrome P450 subfamily XIA polypeptide 1 (CYP11A1), Cytochrome b5 (CYB5A), and 17-beta-Hydroxysteroid dehydrogenase IV (HSD17B4) were all found to be significantly (P < 0.05) up-regulated in high androstenone boars in both Duroc and Landrace. Furthermore, Cytochrome P450 c19A2 (CYP19A2) was down-regulated and progesterone receptor membrane component 1 (PGRMC1) was up-regulated in high-androstenone Duroc boars only, while CYP21 was significantly down-regulated (2.5) in high-androstenone Landrace only. The genes Nuclear Receptor co-activator 4 (NCOA4), Sphingomyrlin phosphodiesterase 1 (SMPD1) and 3beta-hydroxysteroid dehydrogenase (HSD3B) were not significantly differentially expressed in any breeds. Additionally, association studies were performed for the genes with one or more detected SNPs. Association between SNP and androstenone level was observed in CYB5A only, suggesting cis-regulation of the differential transcription in this gene.

CONCLUSION

A large pig material of highly extreme androstenone levels is investigated. The current study contributes to the knowledge about which genes that is differentially expressed regard to the levels of androstenone in pigs. Results in this paper suggest that several genes are important in the regulation of androstenone level in boars and warrant further evaluation of the above mentioned candidate genes, including analyses in different breeds, identification of causal mutations and possible gene interactions.

Quantitative proteome and phosphoproteome analyses of cultured cells based on SILAC labeling without requirement of serum dialysis

The use of dialyzed serum is essential in the application of the conventional stable isotope labeling by amino acids in cell culture (SILAC) approach to achieve complete labeling of proteins for quantitative proteomics. Here, we first evaluated the impact of dialyzed serum on the proteome and phosphoproteome of hormone-sensitive breast cancer MCF-7 cells and found that dialyzed serum influenced the expression of proteins related to signaling systems via hormone receptors, inducing a marked change of the phosphoproteome compared with the use of non-dialyzed serum. We also evaluated 9 other cell lines, including HeLa, HEK293 and Panc1, and found that the influence of serum dialysis on the expression profiles of the proteome and phosphoproteome varied, depending on the cell type. To avoid these problems, we established a SILAC-based quantification approach without the requirement of serum dialysis. Our simple approach is based on dual labeling of two populations of cells with two kinds of heavy amino acids of different mass, using non-dialyzed serum. Using our SILAC approach with non-dialyzed serum, we successfully quantified the phosphoproteome of MCF-7 cells induced by lapatinib, an EGFR1/Her2 dual kinase inhibitor. Because of the dual labeling approach, our method is widely applicable to cultured cells in which protein labeling is incomplete for any reason, e.g., owing to the use of non-dialyzed serum or a low growth rate.