Progesterone receptor membrane component 1/Sigma-2 receptor associates with MAP1LC3B and promotes autophagy

PGRMC1 promotes NSCLC stemness phenotypes by disrupting TRIM56-mediated ubiquitination of AHR

Cancer stem cells (CSCs) are responsible for tumor chemoresistance, and the aryl hydrocarbon receptor (AHR) is indispensable for maintaining CSC characteristics. Here, we aimed to investigate how the interaction between progesterone receptor membrane component 1 (PGRMC1) and AHR contributes to the maintenance of CSC phenotypes in non-small cell lung cancer (NSCLC). Clinical data and tissue microarray analyses indicated that patients with elevated PGRMC1 expression had poorer prognoses. Moreover, PGRMC1 overexpression enhanced CSC phenotypes and chemotherapy resistance in vitro and in vivo by modulating AHR ubiquitination. We then determined the specific interaction sites between PGRMC1 and AHR. Mass spectrometry screening identified tripartite motif containing 56 (TRIM56) as the E3 ligase targeting AHR. Notably, PGRMC1 overexpression inhibited the interaction between TRIM56 and AHR. Overall, our study revealed a regulatory mechanism that involves PGRMC1, AHR, and TRIM56, providing insights for developing CSC-targeting strategies in NSCLC treatment.

International consensus guidelines for the definition, detection, and interpretation of autophagy-dependent ferroptosis

Macroautophagy/autophagy is a complex degradation process with a dual role in cell death that is influenced by the cell types that are involved and the stressors they are exposed to. Ferroptosis is an iron-dependent oxidative form of cell death characterized by unrestricted lipid peroxidation in the context of heterogeneous and plastic mechanisms. Recent studies have shed light on the involvement of specific types of autophagy (e.g. ferritinophagy, lipophagy, and clockophagy) in initiating or executing ferroptotic cell death through the selective degradation of anti-injury proteins or organelles. Conversely, other forms of selective autophagy (e.g. reticulophagy and lysophagy) enhance the cellular defense against ferroptotic damage. Dysregulated autophagy-dependent ferroptosis has implications for a diverse range of pathological conditions. This review aims to present an updated definition of autophagy-dependent ferroptosis, discuss influential substrates and receptors, outline experimental methods, and propose guidelines for interpreting the results.Abbreviation: 3-MA:3-methyladenine; 4HNE: 4-hydroxynonenal; ACD: accidentalcell death; ADF: autophagy-dependentferroptosis; ARE: antioxidant response element; BH2:dihydrobiopterin; BH4: tetrahydrobiopterin; BMDMs: bonemarrow-derived macrophages; CMA: chaperone-mediated autophagy; CQ:chloroquine; DAMPs: danger/damage-associated molecular patterns; EMT,epithelial-mesenchymal transition; EPR: electronparamagnetic resonance; ER, endoplasmic reticulum; FRET: Försterresonance energy transfer; GFP: green fluorescent protein;GSH: glutathione;IF: immunofluorescence; IHC: immunohistochemistry; IOP, intraocularpressure; IRI: ischemia-reperfusion injury; LAA: linoleamide alkyne;MDA: malondialdehyde; PGSK: Phen Green™ SK;RCD: regulatedcell death; PUFAs: polyunsaturated fatty acids; RFP: red fluorescentprotein;ROS: reactive oxygen species; TBA: thiobarbituricacid; TBARS: thiobarbituric acid reactive substances; TEM:transmission electron microscopy.

Pleiotropy of Progesterone Receptor Membrane Component 1 in Modulation of Cytochrome P450 Activity

Progesterone receptor membrane component 1 (PGRMC1) is one of few proteins that have been recently described as direct modulators of the activity of human cytochrome P450 enzymes (CYP)s. These enzymes form a superfamily of membrane-bound hemoproteins that metabolize a wide variety of physiological, dietary, environmental, and pharmacological compounds. Modulation of CYP activity impacts the detoxification of xenobiotics as well as endogenous pathways such as steroid and fatty acid metabolism, thus playing a central role in homeostasis. This review is focused on nine main topics that include the most relevant aspects of past and current PGRMC1 research, focusing on its role in CYP-mediated drug metabolism. Firstly, a general overview of the main aspects of xenobiotic metabolism is presented (I), followed by an overview of the role of the CYP enzymatic complex (IIa), a section on human disorders associated with defects in CYP enzyme complex activity (IIb), and a brief account of cytochrome b5 (cyt b5)'s effect on CYP activity (IIc). Subsequently, we present a background overview of the history of the molecular characterization of PGRMC1 (III), regarding its structure, expression, and intracellular location (IIIa), and its heme-binding capability and dimerization (IIIb). The next section reflects the different effects PGRMC1 may have on CYP activity (IV), presenting a description of studies on the direct effects on CYP activity (IVa), and a summary of pathways in which PGRMC1's involvement may indirectly affect CYP activity (IVb). The last section of the review is focused on the current challenges of research on the effect of PGRMC1 on CYP activity (V), presenting some future perspectives of research in the field (VI).

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.

Olanzapine-induced nonalcoholic fatty liver disease: The effects of differential food pattern and the involvement of PGRMC1 signaling

Detrimental dietary habits with high-fat food are common in the psychiatric population, leading to higher obesity rate. Olanzapine (OLZ), as one of the mainstream antipsychotic drugs, shows superior efficacy in treating schizophrenia but limited by adverse effects such as obesity, dyslipidemia and liver injury, which are risk factors for the development of nonalcoholic fatty liver disease (NAFLD). Progesterone receptor component 1 (PGRMC1) is a key regulator associated with antipsychotic drug-induced metabolic disorders. Our study aims to investigate whether high-fat supplementation worsens OLZ-induced NAFLD and to validate the potential role of PGRMC1 pathway. In vivo, eight-week OLZ treatment successfully induced hepatic steatosis in female C57BL/6 mice fed with either a high-fat or normal diet, which is independent of body weight gain. Likewise, in vitro, OLZ markedly led to hepatocyte steatosis along with enhanced oxidative stress, which was aggravated by free fatty acids. Moreover, in vivo and in vitro, high-fat supplementation aggravated OLZ-induced hepatic lipid accumulation and oxidative stress via inhibition of hepatic PGRMC1-AMPK-mTORC1/Nrf2 pathways. Inspiringly, PGRMC1 overexpression effectively reversed OLZ-induced hepatocyte steatosis in vitro. Hence, hepatic PGRMC1 is attributable to OLZ-induced NAFLD especially with high-fat supplementation and potentially serves as a novel therapeutic target.

Sigma-2 Receptors—From Basic Biology to Therapeutic Target: A Focus on Age-Related Degenerative Diseases

There is a large unmet medical need to develop disease-modifying treatment options for individuals with age-related degenerative diseases of the central nervous system. The sigma-2 receptor (S2R), encoded by TMEM97, is expressed in brain and retinal cells, and regulates cell functions via its co-receptor progesterone receptor membrane component 1 (PGRMC1), and through other protein–protein interactions. Studies describing functions of S2R involve the manipulation of expression or pharmacological modulation using exogenous small-molecule ligands. These studies demonstrate that S2R modulates key pathways involved in age-related diseases including autophagy, trafficking, oxidative stress, and amyloid-β and α-synuclein toxicity. Furthermore, S2R modulation can ameliorate functional deficits in cell-based and animal models of disease. This review summarizes the current evidence-based understanding of S2R biology and function, and its potential as a therapeutic target for age-related degenerative diseases of the central nervous system, including Alzheimer’s disease, α-synucleinopathies, and dry age-related macular degeneration.

Recent insight into autophagy and immunity at the maternal-fetal interface

Autophagy is a lysosomal degradation pathway that supports metabolic adaptation and energy cycling. It is essential for cell homeostasis, differentiation, development, and survival. Recent studies have shown that autophagy could influence immune responses by regulating immune cell functions. Reciprocally, immune cells strongly influence autophagy. Immune cells at the maternal-fetal interface are thought to play essential roles in pregnancy. Here, we review the induction of autophagy at the maternal-fetal interface and its role in decidualization and placental development. Additionally, we emphasize the role of autophagy in the immune microenvironment at the maternal-fetal interface, including innate immunity, adaptive immunity, and immune tolerance molecules. It also suggests new research directions and prospects.

The role of progesterone and the progesterone receptor in cancer: progress in the last 5 years

INTRODUCTION

Patients with various advanced cancers devoid of nuclear progesterone receptors (nPR) have demonstrated increased quality and length of life when treated with the PR modulator mifepristone, which likely works by interacting with membrane PRs (mPR).

AREAS COVERED

Two immunomodulatory proteins are discussed that seem to play a role in cancers that proliferate whether the malignant tumor is positive or negative for the nPR. These two proteins are the progesterone receptor membrane component-1 (PGRMC-1) and the progesterone-induced blocking factor (PIBF). Both PGRMC-1 and the parent form of PIBF foster increased tumor aggressiveness, whereas splice variants of the 90 kDa form of PIBF inhibit immune response against cancer cells.

EXPERT OPINION

The marked clinical improvement following 200-300 mg of mifepristone is likely related to blocking PIBF. In the low dosage used, mifepristone likely acts as an agonist for PGRMC-1 protein. Mifepristone may be less effective for cancers positive for the nPR because the nPR may be protective and blocking it may have detrimental effects. Based on this hypothetical model, the development of other potential treatment options to provide even greater efficacy for treating cancer are discussed.

The role of progesterone receptor membrane component (PGRMC) in the endometrium

PGRMC is a non-classical receptor that mediates the non-genomic responses to progesterone and is distributed in different subcellular compartments. PGRMC belongs to the membrane-associated progesterone receptor (MAPR) family. Two PGRMC subtypes (PGRMC1 and PGRMC2) have been characterized, and both are expressed in the human endometrium. PGRMC expression is differentially regulated during the menstrual cycle in the human endometrium. Although PGRMC1 is predominantly expressed in the proliferative phase and PGRMC2 in the secretory phase, this expression changes in pathologies such as endometriosis, in which PGRMC2 expression considerably decreases, promoting progesterone resistance. In endometrial cancer, PGRMC1 is overexpressed, its activation induces tumors growth, and confers chemoresistance in the presence of progesterone. Thus, PGRMCs play a key role in progesterone actions in the endometrium.

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.

Ultrasound-triggered microbubble destruction enhances the radiosensitivity of glioblastoma by inhibiting PGRMC1-mediated autophagy in vitro and in vivo

BACKGROUND

Ultrasound-triggered microbubble destruction (UTMD) is a widely used noninvasive technology in both military and civilian medicine, which could enhance radiosensitivity of various tumors. However, little information is available regarding the effects of UTMD on radiotherapy for glioblastoma or the underlying mechanism. This study aimed to delineate the effect of UTMD on the radiosensitivity of glioblastoma and the potential involvement of autophagy.

METHODS

GL261, U251 cells and orthotopic glioblastoma-bearing mice were treated with ionizing radiation (IR) or IR plus UTMD. Autophagy was observed by confocal microscopy and transmission electron microscopy. Western blotting and immunofluorescence analysis were used to detect progesterone receptor membrane component 1 (PGRMC1), light chain 3 beta 2 (LC3B2) and sequestosome 1 (SQSTM1/p62) levels. Lentiviral vectors or siRNAs transfection, and fluorescent probes staining were used to explore the underlying mechanism.

RESULTS

UTMD enhanced the radiosensitivity of glioblastoma in vitro and in vivo (P < 0.01). UTMD inhibited autophagic flux by disrupting autophagosome-lysosome fusion without impairing lysosomal function or autophagosome synthesis in IR-treated glioblastoma cells. Suppression of autophagy by 3-methyladenine, bafilomycin A1 or ATG5 siRNA had no significant effect on UTMD-induced radiosensitization in glioblastoma cells (P < 0.05). Similar results were found when autophagy was induced by rapamycin or ATG5 overexpression (P > 0.05). Furthermore, UTMD inhibited PGRMC1 expression and binding with LC3B2 in IR-exposed glioblastoma cells (P < 0.01). PGRMC1 inhibitor AG-205 or PGRMC1 siRNA pretreatment enhanced UTMD-induced LC3B2 and p62 accumulation in IR-exposed glioblastoma cells, thereby promoting UTMD-mediated radiosensitization (P < 0.05). Moreover, PGRMC1 overexpression abolished UTMD-caused blockade of autophagic degradation, subsequently inhibiting UTMD-induced radiosensitization of glioblastoma cells. Finally, compared with IR plus UTMD group, PGRMC1 overexpression significantly increased tumor size [(3.8 ± 1.1) mm² vs. (8.0 ± 1.9) mm², P < 0.05] and decreased survival time [(67.2 ± 2.6) d vs. (40.0 ± 1.2) d, P = 0.0026] in glioblastoma-bearing mice.

CONCLUSION

UTMD enhanced the radiosensitivity of glioblastoma partially by disrupting PGRMC1-mediated autophagy.

Progesterone Receptor Membrane Component 1 and Its Accomplice: Emerging Therapeutic Targets in Lung Cancer

Progesterone receptor membrane component 1 (PGRMC1) is a trans-membrane evolutionarily conserved protein with a cytochrome b5 like heme/steroid binding domain. PGRMC1 clinical levels are strongly suggested to correlate with poor patient survival and lung cancer prognosis. PGRMC1 has been reported to possess pleiotropic functions, such as participating in cellular and membrane trafficking, steroid hormone signaling, cholesterol metabolism and steroidogenesis, glycolysis and mitochondrial energy metabolism, heme transport and homeostasis, neuronal movement and synaptic function, autophagy, anti-apoptosis, stem cell survival and the list is still expanding. PGRMC1 mediates its pleiotropic functions through its ability to interact with multiple binding partners, such as epidermal growth factor receptor (EGFR), sterol regulatory element binding protein cleavage activating protein (SCAP), insulin induced gene-1 protein (Insig-1), heme binding proteins (hepcidin, ferrochelatase and cyp450 members), plasminogen activator inhibitor 1 RNA binding protein (PAIR-BP1). In this review, we provide a comprehensive overview of PGRMC1 and its associated pleiotropic functions that are indispensable for lung cancer promotion and progression, suggesting it as a prospective therapeutic target for intervention. Notably, we have compiled and reported various preclinical studies wherein prospective agonists and antagonists had been tested against PGRMC1 expressing cancer cell lines, suggesting it as a prospective therapeutic target for cancer intervention.

PGRMC1-dependent lipophagy promotes ferroptosis in paclitaxel-tolerant persister cancer cells

Background

Progesterone receptor membrane component 1 (PGRMC1) is a heme-binding protein inducing dimerization with cytochrome P450, which mediates chemoresistance. Increased PGRMC1 expression is found in multiple types of resistant cancers, but the role of PGRMC1 in the ferroptosis of cancer cells remains unrevealed. Therefore, we examined the role of PGRMC1 in promoting ferroptosis in paclitaxel-tolerant persister cancer cells (PCC).

Methods

The effects of ferroptosis inducers and PGRMC1 gene silencing/overexpression were tested on head and neck cancer (HNC) cell lines and mouse tumor xenograft models. The results were analyzed about cell viability, death, lipid ROS and iron production, mRNA/protein expression and interaction, and lipid assays.

Results

PCC had more free fatty acids, lipid droplets, and fatty acid oxidation (FAO) than their parental cells. PCC was highly sensitive to inhibitors of system xc⁻ cystine/glutamate antiporter (xCT), such as erastin, sulfasalazine, and cyst(e)ine deprivation, but less sensitive to (1S,3R)-RSL3. PGRMC1 silencing in PCC reduced ferroptosis sensitivity by xCT inhibitors, and PGRMC1 overexpression in parental cells increased ferroptosis by xCT inhibitors. Lipid droplets were degraded along with autophagy induction and autophagosome formation by erastin treatment in PCC. Lipophagy was accompanied by increased tubulin detyrosination, which was increased by SIRT1 activation but decreased by SIRT1 inhibition. FAO and lipophagy were also promoted by the interaction between lipid droplets and mitochondria.

Conclusion

PGRMC1 expression increased FAO and ferroptosis sensitivity from in vivo mice experiments. Our data suggest that PGRMC1 promotes ferroptosis by xCT inhibition in PCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02168-2.

Paclitaxel-tolerant persister cancer cells (PCC) had PGRMC1 upregulation related to increased free fatty acids, lipid droplets, and fatty acid oxidation. PGRMC1 expression substantially increased ferroptosis by xCT inhibition via lipophagy and tubulin detyrosination, whereas PGRMC1 silencing decreased ferroptosis: this suggests that PGRMC1 expression promotes ferroptosis in PCC.

Progesterone receptor membrane component 1 (PGRMC1) binds and stabilizes cytochromes P450 through a heme-independent mechanism

Progesterone receptor membrane component 1 (PGRMC1) is a heme-binding protein implicated in a wide range of cellular functions. We previously showed that PGRMC1 binds to cytochromes P450 in yeast and mammalian cells and supports their activity. Recently, the paralog PGRMC2 was shown to function as a heme chaperone. The extent of PGRMC1 function in cytochrome P450 biology and whether PGRMC1 is also a heme chaperone are unknown. Here, we examined the function of Pgrmc1 in mouse liver using a knockout model and found that Pgrmc1 binds and stabilizes a broad range of cytochromes P450 in a heme-independent manner. Proteomic and transcriptomic studies demonstrated that Pgrmc1 binds more than 13 cytochromes P450 and supports maintenance of cytochrome P450 protein levels posttranscriptionally. In vitro assays confirmed that Pgrmc1 KO livers exhibit reduced cytochrome P450 activity consistent with reduced enzyme levels. Mechanistic studies in cultured cells demonstrated that PGRMC1 stabilizes cytochromes P450 and that binding and stabilization do not require PGRMC1 binding to heme. Importantly, Pgrmc1-dependent stabilization of cytochromes P450 is physiologically relevant, as Pgrmc1 deletion protected mice from acetaminophen-induced liver injury. Finally, evaluation of Y113F mutant Pgrmc1, which lacks the axial heme iron-coordinating hydroxyl group, revealed that proper iron coordination is not required for heme binding, but is required for binding to ferrochelatase, the final enzyme in heme biosynthesis. PGRMC1 was recently identified as the causative mutation in X-linked isolated pediatric cataract formation. Together, these results demonstrate a heme-independent function for PGRMC1 in cytochrome P450 stability that may underlie clinical phenotypes.

PGRMC1 acts as a size-selective cargo receptor to drive ER-phagic clearance of mutant prohormones

The reticulon-3 (RTN3)-driven targeting complex promotes clearance of misfolded prohormones from the endoplasmic reticulum (ER) for lysosomal destruction by ER-phagy. Because RTN3 resides in the cytosolic leaflet of the ER bilayer, the mechanism of selecting misfolded prohormones as ER-phagy cargo on the luminal side of the ER membrane remains unknown. Here we identify the ER transmembrane protein PGRMC1 as an RTN3-binding partner. Via its luminal domain, PGRMC1 captures misfolded prohormones, targeting them for RTN3-dependent ER-phagy. PGRMC1 selects cargos that are smaller than the large size of other reported ER-phagy substrates. Cargos for PGRMC1 include mutant proinsulins that block secretion of wildtype proinsulin through dominant-negative interactions within the ER, causing insulin-deficiency. Chemical perturbation of PGRMC1 partially restores WT insulin storage by preventing ER-phagic degradation of WT and mutant proinsulin. Thus, PGRMC1 acts as a size-selective cargo receptor during RTN3-dependent ER-phagy, and is a potential therapeutic target for diabetes.

The oestrous cycle and skeletal muscle atrophy: Investigations in rodent models of muscle loss

NEW FINDINGS

What is the central question of this study? Is the oestrous cycle affected during disuse atrophies and, if so, how are oestrous cycle changes related to musculoskeletal outcomes? What is the main finding and its importance? Rodent oestrous cycles were altered during disuse atrophy, which was correlated with musculoskeletal outcomes. However, the oestrous cycle did not appear to be changed by Lewis lung carcinoma, which resulted in no differences in muscle size in comparison to healthy control animals. These findings suggest a relationship between the oestrous cycle and muscle size during atrophic pathologies.

ABSTRACT

Recent efforts have focused on improving our understanding of female muscle physiology during exposure to muscle atrophic stimuli. A key feature of female rodent physiology is the oestrous cycle. However, it is not known how such stimuli interact with the oestrous cycle to influence muscle health. In this study, we investigated the impact of muscle atrophic stimuli on the oestrous cycle and how these alterations are correlated with musculoskeletal outcomes. A series of experiments were performed in female rodents, including hindlimb unloading (HU), HU followed by 24 h of reloading, HU combined with dexamethasone treatment, and Lewis lung carcinoma. The oestrous cycle phase was assessed throughout each intervention and correlated with musculoskeletal outcomes. Seven or 14 days of HU increased the duration in dioestrus or metoestrus (D/M; low hormones) and was negatively correlated with gastrocnemius mass. Time spent in D/M was also negatively correlated with changes in grip strength and bone density after HU, and with muscle recovery 24 h after the cessation of HU. The addition of dexamethasone strengthened these relationships between time in D/M and reduced musculoskeletal outcomes. However, in animals with Lewis lung carcinoma, oestrous cyclicity did not differ from that of control animals, and time spent in D/M was not correlated with either gastrocnemius mass or tumour burden. In vitro experiments suggested that enhanced protein synthesis induced by estrogen might protect against muscle atrophy. In conclusion, muscle atrophic insults are correlated with changes in the oestrous cycle, which are associated with deterioration in musculoskeletal outcomes. The magnitude of oestrous cycle alterations depends on the atrophic stimuli.

Lipin1 Alleviates Autophagy Disorder in Sciatic Nerve and Improves Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is a chronic complication of diabetes, and its neural mechanisms underlying the pathogenesis remain unclear. Autophagy plays an important role in neurodegenerative diseases and nerve tissue injury. Lipin1 is a phosphatidic acid phosphatase enzyme that converts phosphatidic acid (PA) into diacylglycerol (DAG), a precursor of triacylglycerol and phospholipids which plays an important role in maintaining normal peripheral nerve conduction function. However, whether Lipin1 involved in the pathogenesis of DPN via regulation of autophagy is not elucidated. Here, we show that the Lipin1 expression was downregulated in streptozotocin (STZ)-induced DPN rat model. Interestingly, STZ prevented DAG synthesis, and resulted in autophagic hyperactivity, effects which may increase the apoptosis of Schwann cells and lead to demyelination in sciatic nerve in DPN rats. More importantly, upregulation of lipin1 in the DPN rats ameliorated autophagy disorders and pathological changes of the sciatic nerve, which associated with the increase of the motor nerve conductive velocity (MNCV) in DPN rats. In contrast, knockdown of lipin1 exacerbates neuronal abnormalities and facilitates the genesis of DPN phenotypes in rats. In addition, overexpression of lipin1 in RSC96 cells also significantly decreased the autophagic hyperactivity and apoptosis induced by hyperglycemia. These results suggest that lipin1 may exert neuroprotection within the sciatic nerve anomalies and may serve as a potential therapeutic target for the treatment of DPN.

Deciphering the Role of PGRMC1 During Human Decidualization Using an In Vitro Approach

CONTEXT

Non-classical membrane progesterone receptor (mPRs) and progesterone receptor membrane component 1 (PGRMC1) expression have been detected in endometrium, but their role in decidualization had not yet been investigated. We previously demonstrated PGRMC1 downregulation in receptive endometrium and that its overexpression inhibits decidualization. Furthermore, during decidualization, PGRMC1 mainly interacts with proteins involved in biosynthesis, intracellular transport, and mitochondrial activity.

OBJECTIVE

To determine PGRMC1 and mPRs signaling role during decidualization.

METHODS

Isolated primary endometrial stromal cells (EnSC) were decidualized in vitro in the presence of classic stimuli (E2 + P4), PGRMC1 inhibitor (AG205), or membrane-impermeable P4 (P4-BSA). Endometrial biopsies were obtained from 19 fertile oocyte donors attending the IVI-Valencia in vitro fertilization (IVF) clinic. EnSC decidualization was evaluated by prolactin ELISA and F-actin immunostaining. Progesterone receptor localization was evaluated by immunofluorescence. EnSC transcriptomic profiles were analyzed by microarray technology.

RESULTS

PGRMC1 inhibition during EnSC decidualization (AG205dEnSC) does not interfere with EnSC cytoskeletal rearrangements and prolactin secretion. However, global transcriptional profiling revealed more differentially expressed genes in AG205dEnSC than in dEnSC, compared with nondecidualized EnSC (ndEnSC). In silico analysis showed that PGRMC1 inhibition upregulated more genes related to metabolism, molecular transport, and hormonal biosynthesis compared with control dEnSC. EnSC decidualized in the presence of P4-BSA showed a similar behavior as ndEnSC in terms of morphological features, absence of prolactin secretion, and transcriptomic pattern.

CONCLUSION

Our findings associate PGRMC1 to hormonal biosynthesis, metabolism, and vesicular transport-important cellular functions for dEnSC supporting pregnancy. Activation of membrane P4 receptor signaling alone was unable to induce downstream effects needed for proper decidualization.

1,2,3,4-Tetrahydroisoquinoline (THIQ) as privileged scaffold for anticancer de novo drug design

Introduction: Cancer is a dreadful disorder that is emerging as one of the leading causes of mortality across the globe. The complex tumor environment, supplemented with drawbacks of the existing drugs, has made it a global health concern. The Tetrahydroisoquinoline (THIQ) ring holds an important position in medicinal chemistry due to its wide range of pharmacological properties. Several THIQ based natural products have been previously explored for their antitumor properties, making it a vital scaffold for anticancer drug design.Areas covered: This review article addresses the potential of THIQ as anticancer agents. Various medicinal chemistry strategies employed for the design and development of THIQ analogs as inhibitors or modulators of relevant anticancer targets have been discussed in detail. Moreover, the common strategies employed for the synthesis of the core scaffold are also highlighted.Expert opinion: Evidently, THIQs have tremendous potential in anticancer drug design. Some of these analogs exhibited potent activity against various cancer molecular targets. However, there are some drawbacks, such as selectivity that need addressing. The synthetic ease for constructing the core scaffold complimented with its reactivity makes it ideal for further structure-activity relationship studies. For these reasons, THIQ is a privileged scaffold for the design and development of novel anticancer agents.

ATI1 (ATG8-interacting protein 1) and ATI2 define a plant starvation-induced reticulophagy pathway and serve as MSBP1/MAPR5 cargo receptors

Reticulophagy, the selective autophagy of endoplasmic reticulum (ER) components, is known to operate in eukaryotes from yeast and unicellular algae to animals and plants. Thus far, only ER-stress induced reticulophagy was reported and analyzed in plants. In this study we characterize a reticulophagy pathway in Arabidopsis thaliana that is triggered by dark-induced starvation but not by ER stress. This pathway is defined by the previously reported ATG8-interacting proteins, ATI1 and ATI2. We further identified the ER-localized MSBP1 (Membrane Steroid Binding Protein 1) as an ATI1- and ATI2-interacting protein and an autophagy cargo, and show that ATI1 and ATI2 serve as its cargo receptors. Together, these findings expand our knowledge on plant responses during energy deprivation and highlight the role of this special type of reticulophagy in this process.Abbreviations: AGO1: ARGONAUTE 1; ATI: ATG8-Interacting Protein; BiFC: Bimolecular Fluorescence Complementation; BR: brassinosteroid; conA: concanamycin A; DMSO: dimethyl sulfoxid; DTT: dithiothreitol; ER: endoplasmic reticulum; GFP: green fluorescent protein; MAPR: Membrane-Associated Progesterone Binding Protein; MSBP: Membrane Steroid Binding Protein; SD: standard deviation; SE: standard error; TM: tunicamycin; TOR: target of rapamycin; Y2H: yeast two-hybrid.

Sigma-2 receptor antagonists rescue neuronal dysfunction induced by Parkinson's patient brain-derived α-synuclein

α‐Synuclein oligomers are thought to have a pivotal role in sporadic and familial Parkinson's disease (PD) and related α‐synucleinopathies, causing dysregulation of protein trafficking, autophagy/lysosomal function, and protein clearance, as well as synaptic function impairment underlying motor and cognitive symptoms of PD. Moreover, trans‐synaptic spread of α‐synuclein oligomers is hypothesized to mediate disease progression. Therapeutic approaches that effectively block α‐synuclein oligomer‐induced pathogenesis are urgently needed. Here, we show for the first time that α‐synuclein species isolated from human PD patient brain and recombinant α‐synuclein oligomers caused similar deficits in lipid vesicle trafficking rates in cultured rat neurons and glia, while α‐synuclein species isolated from non‐PD human control brain samples did not. Recombinant α‐synuclein oligomers also increased neuronal expression of lysosomal‐associated membrane protein‐2A (LAMP‐2A), the lysosomal receptor that has a critical role in chaperone‐mediated autophagy. Unbiased screening of several small molecule libraries (including the NIH Clinical Collection) identified sigma‐2 receptor antagonists as the most effective at blocking α‐synuclein oligomer‐induced trafficking deficits and LAMP‐2A upregulation in a dose‐dependent manner. These results indicate that antagonists of the sigma‐2 receptor complex may alleviate α‐synuclein oligomer‐induced neurotoxicity and are a novel therapeutic approach for disease modification in PD and related α‐synucleinopathies.

Ovarian hormones-autophagy-immunity axis in menstruation and endometriosis

Menstruation occurs in few species and involves a cyclic process of proliferation, breakdown and regeneration under the control of ovarian hormones. Knowledge of normal endometrial physiology, as it pertains to the regulation of menstruation, is essential to understand disorders of menstruation. Accumulating evidence indicates that autophagy in the endometrium, under the regulation of ovarian hormones, can result in the infiltration of immune cells, which plays an indispensable role in the endometrium shedding, tissue repair and prevention of infections during menstruation. In addition, abnormal autophagy levels, together with resulting dysregulated immune system function, are associated with the pathogenesis and progression of endometriosis. Considering its potential value of autophagy as a target for the treatment of menstrual-related and endometrium-related disorders, we review the activity and function of autophagy during menstrual cycles. The role of the estrogen/progesterone-autophagy-immunity axis in endometriosis are also discussed.

Sigma-2 Receptor-A Potential Target for Cancer/Alzheimer's Disease Treatment via Its Regulation of Cholesterol Homeostasis

The sigma receptors were classified into sigma-1 and sigma-2 receptor based on their different pharmacological profiles. In the past two decades, our understanding of the biological and pharmacological properties of the sigma-1 receptor is increasing; however, little is known about the sigma-2 receptor. Recently, the molecular identity of the sigma-2 receptor has been identified as TMEM97. Although more and more evidence has showed that sigma-2 ligands have the ability to treat cancer and Alzheimer’s disease (AD), the mechanisms connecting these two diseases are unknown. Data obtained over the past few years from human and animal models indicate that cholesterol homeostasis is altered in AD and cancer, underscoring the importance of cholesterol homeostasis in AD and cancer. In this review, based on accumulated evidence, we proposed that the beneficial roles of sigma-2 ligands in cancer and AD might be mediated by their regulation of cholesterol homeostasis.

Mitophagy Receptors and Mediators: Therapeutic Targets in the Management of Cardiovascular Ageing

Mitophagy serves as a cardinal regulator in the maintenance of mitochondrial integrity, function, and cardiovascular homeostasis, through the fine control and governance of cellular metabolism, ATP production, redox balance, and mitochondrial quality and quantity control. As a unique form of selective autophagy, mitophagy specifically recognizes and engulfs long-lived or damaged (depolarized) mitochondria through formation of the double-membraned intracellular organelles - mitophagosomes, ultimately resulting in lysosomal degradation. Levels of mitophagy are reported to be altered in pathological settings including cardiovascular diseases and biological ageing although the precise nature of mitophagy change in ageing and ageing-associated cardiovascular deterioration remains poorly defined. Ample clinical and experimental evidence has depicted a convincing tie between cardiovascular ageing and altered mitophagy. In particular, ageing perturbs multiple enigmatic various signal machineries governing mitophagy, mitochondrial quality, and mitochondrial function, contributing to ageing-elicited anomalies in the cardiovascular system. This review will update novel regulatory mechanisms of mitophagy especially in the perspective of advanced ageing, and discuss how mitophagy dysregulation may be linked to cardiovascular abnormalities in ageing. We hope to pave the way for development of new therapeutic strategies against the growing health and socieconomical issue of cardiovascular ageing through targeting mitophagy.

Autophagy up-regulation by ulipristal acetate as a novel target mechanism in the treatment of uterine leiomyoma: an in vitro study

OBJECTIVE

To assess the effect of ulipristal acetate (UPA) on the autophagic process of uterine leiomyoma cells.

DESIGN

In vitro study in primary cultures of leiomyoma and myometrial cells isolated from biopsy specimen, and gene expression evaluation in biopsy material.

SETTING

Cellular pathology laboratory.

PATIENT(S)

Premenopausal women (without hormonal treatment) undergoing myomectomy or hysterectomy for symptomatic leiomyomas.

INTERVENTION(S)

Surgical specimens collected from uterine leiomyomas and matched normal myometria.

MAIN OUTCOME MEASURE(S)

After treatment of myometrial and leiomyoma cells with UPA, autophagy was evaluated by Western blot analysis of the typical biochemical markers, LC3-II, LC3-II:LC3-I ratio, and p62/SQSTM1. The expression level of Atg7 and Atg4D proteins was also assessed by Western blot.

RESULT(S)

The increase of LC3-II protein, LC3-II:LC3-I ratio, and p62/SQSTM1 protein indicates that UPA treatment up-regulates the autophagic response in leiomyoma cells, whereas these markers were almost unchanged in myometrial cells. Consistently, an increased level of Atg7 and Atg4D proteins was observed only in UPA-treated leiomyoma cells. The autophagic machinery is put into motion selectively in these cells, despite that the basal messenger RNA levels of LC3, SQSTM1, and ATG7 in leiomyoma biopsy specimen were not significantly different from those found in normal myometrial biopsy material.

CONCLUSION(S)

In vitro UPA treatment stimulates the autophagic response selectively in leiomyoma cells, which adds a novel indication for the clinical use of this selective P receptor (PR) modulator. Autophagy up-regulation may potentially contribute to the leiomyoma shrinkage occurring in UPA-treated patients and warrants further study.

Progesterone Attenuates Stress-Induced NLRP3 Inflammasome Activation and Enhances Autophagy following Ischemic Brain Injury

NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome inhibition and autophagy induction attenuate inflammation and improve outcome in rodent models of cerebral ischemia. However, the impact of chronic stress on NLRP3 inflammasome and autophagic response to ischemia remains unknown. Progesterone (PROG), a neuroprotective steroid, shows promise in reducing excessive inflammation associated with poor outcome in ischemic brain injury patients with comorbid conditions, including elevated stress. Stress primes microglia, mainly by the release of alarmins such as high-mobility group box-1 (HMGB1). HMGB1 activates the NLRP3 inflammasome, resulting in pro-inflammatory interleukin (IL)-1β production. In experiment 1, adult male Sprague-Dawley rats were exposed to social defeat stress for 8 days and then subjected to global ischemia by the 4-vessel occlusion model, a clinically relevant brain injury associated with cardiac arrest. PROG was administered 2 and 6 h after occlusion and then daily for 7 days. Animals were killed at 7 or 14 days post-ischemia. Here, we show that stress and global ischemia exert a synergistic effect in HMGB1 release, resulting in exacerbation of NLRP3 inflammasome activation and autophagy impairment in the hippocampus of ischemic animals. In experiment 2, an in vitro inflammasome assay, primary microglia isolated from neonatal brain tissue, were primed with lipopolysaccharide (LPS) and stimulated with adenosine triphosphate (ATP), displaying impaired autophagy and increased IL-1β production. In experiment 3, hippocampal microglia isolated from stressed and unstressed animals, were stimulated ex vivo with LPS, exhibiting similar changes than primary microglia. Treatment with PROG reduced HMGB1 release and NLRP3 inflammasome activation, and enhanced autophagy in stressed and unstressed ischemic animals. Pre-treatment with an autophagy inhibitor blocked Progesterone's (PROG's) beneficial effects in microglia. Our data suggest that modulation of microglial priming is one of the molecular mechanisms by which PROG ameliorates ischemic brain injury under stressful conditions.

Progesterone receptor-mediated actions and the treatment of central nervous system disorders: An up-date of the known and the challenge of the unknown

Progesterone has been shown to exert a wide range of remarkable protective actions in experimental models of central nervous system injury or disease. However, the intimate mechanisms involved in each of these beneficial effects are not fully depicted. In this review, we intend to give the readers a thorough revision on what is known about the participation of diverse receptors and signaling pathways in progesterone-mediated neuroprotective, pro-myelinating and anti-inflammatory outcomes, as well as point out to novel regulatory mechanisms that could open new perspectives in steroid-based therapies.

Functional validation of metabolic genes that distinguish Gleason 3 from Gleason 4 prostate cancer foci

BACKGROUND

Gleason grade is among the most powerful clinicopathological classification systems used to assess risk of lethal potential in prostate cancer, yet its biologic basis is poorly understood. Notably, pure low-grade cancers, comprised predominantly of Gleason pattern 3 (G3) are typically indolent, with lethal potential emerging with the progression of higher-grade Gleason patterns 4 (G4) or 5. One of the hallmarks of more aggressive cancer phenotypes is the stereotyped set of metabolic characteristics that transformed cells acquire to facilitate unregulated growth. In the present study, we profiled expression signatures of metabolic genes that are differentially expressed between G3 and G4 cancer foci and investigated the functional role of two of the profiled genes, PGRMC1 and HSD17B4, in prostate cancer cells.

METHODS

Gene expression profiling was conducted using 32 G3 and 32 G4 cancer foci from patients with 3+3 and ≥4+3 tumors, respectively. A 95-gene Nanostring probe set was used to probe genes associated with energy metabolism. Two out of five genes (PGRMC1 and HSD17B4) that significantly distinguish between G3 and G4 were functionally validated in vitro using established prostate cancer cells (PC3, DU145). Expression of PGRMC1 and HSD17B4 was knocked down and subsequent studies were performed to analyze cell proliferation, migration, invasion, and apoptosis. Mechanistic studies that explored the epidermal growth factor receptor (EGFR) pathway were performed by Western blot.

RESULTS

Multivariate analysis identified five metabolic genes that were differentially expressed between G3 and G4 stroma (P < .05). Functional validation studies revealed that knockdown of PGRMC1 and HSD17B4 significantly decreased cell proliferation, migration, and invasion, and increased apoptosis in PC3 and DU145 cells. Mechanistic studies showed that these effects, after PGRMC1 knockdown, were possibly mediated through alterations in downstream components of the EGFR, protein kinase B, and nuclear factor kappa-light-chain-enhancer of activated B cells pathways.

CONCLUSION

The following study provides evidence supporting the use of metabolic genes PGRMC1 and HSD17B4 as a prognostic biomarker for the distinction between G3 and G4 prostate cancers.

The mitochondrial heme metabolon: Insights into the complex(ity) of heme synthesis and distribution

Heme is an essential cofactor in metazoans that is also toxic in its free state. Heme is synthesized by most metazoans and must be delivered to all cellular compartments for incorporation into a variety of hemoproteins. The heme biosynthesis enzymes have been proposed to exist in a metabolon, a protein complex consisting of interacting enzymes in a metabolic pathway. Metabolons enhance the function of enzymatic pathways by creating favorable microenvironments for pathway enzymes and intermediates, facilitating substrate transport, and providing a scaffold for interactions with other pathways, signaling molecules, or organelles. Herein we detail growing evidence for a mitochondrial heme metabolon and discuss its implications for the study of heme biosynthesis and cellular heme homeostasis.

Development of Tetrahydroindazole-Based Potent and Selective Sigma-2 Receptor Ligands

The sigma-2 receptor has been shown to play important roles in a number of important diseases, including central nervous system (CNS) disorders and cancer. However, mechanisms by which sigma-2 contributes to these diseases remain unclear. The development of new sigma-2 ligands that can be used to probe the function of this protein and potentially as drug discovery leads is therefore of great importance. Herein we report the development of a series of tetrahydroindazole compounds that are highly potent and selective for sigma-2. Structure-activity relationship data were used to generate a pharmacophore model that summarizes the common features present in the potent ligands. Assays for solubility and microsomal stability showed that several members of this compound series possess promising characteristics for further development of useful chemical probes or drug discovery leads.

Progesterone induced Warburg effect in HEK293 cells is associated with post-translational modifications and proteasomal degradation of progesterone receptor membrane component 1

Progesterone (P4) is a major steroid hormone that has important effects on metabolism. The progesterone receptor membrane component 1 (PGRMC1) is a non-canonical P4 binding protein. The biological functions affected by PGRMC1 include cholesterol/steroid biosynthesis and metabolism, iron homeostasis and heme trafficking, autophagy, regulation of cell cycle and proliferation, cell migration and invasion. PGRMC1 has been an attractive target for therapeutic intervention in cancer and neurodegenerative disorders due to its biological role in promoting cell survival. P4 has been used in a number of clinical applications and is considered neuroprotective. The involvement of PGRMC1 in P4-mediated regulation of cellular glucose metabolism is not well studied. PGRMC1 is a 21 kDa protein but complex post-translational modifications (PTMs) lead to the existence of several high molecular mass proteins whose molecular function, intracellular distribution, and physiological relevancies are not fully known. Therefore, in this study, P4-PGRMC1-mediated cellular glucose metabolism and PTMs of PGRMC1 were studied using wild-type and CRISPR/Cas9 mediated PGRMC1 knockout (KO) human embryonic kidney-derived (HEK293) cell lines. A 70 kDa (p70) and 100 kDa (p100) PGRMC1 proteins were identified that are predominantly associated with endoplasmic reticulum/mitochondria and nuclear fractions in the cells, respectively. Phosphorylation, acetylation, ubiquitination, and sumoylation of native PGRMC1 under serum starvation were identified which provided an explanation for the higher molecular masses. This study indicates that P4-PGRMC1 signaling caused a rapid increase in glycolysis in the presence of oxygen (aerobic glycolysis) and a corresponding decrease in cellular respiration, known as the Warburg effect. Further, it was demonstrated that the P4-induced increase in glycolysis is associated with rapid proteasomal degradation of the p70 and reduction of the nuclear p100 protein level. P4 treatment also caused significant alteration in the dynamics of PGRMC1 PTMs and its association with potential interacting proteins. Overall, this study provides a hitherto unknown aspect of P4-PGRMC1 mediated signaling that changes basic cellular metabolism in HEK293 cells.

Anti-tumor Efficacy Assessment of the Sigma Receptor Pan Modulator RC-106. A Promising Therapeutic Tool for Pancreatic Cancer

Introduction: Pancreatic cancer (PC) is one of the most lethal tumor worldwide, with no prognosis improvement over the past 20-years. The silent progressive nature of this neoplasia hampers the early diagnosis, and the surgical resection of the tumor, thus chemotherapy remains the only available therapeutic option. Sigma receptors (SRs) are a class of receptors proposed as new cancer therapeutic targets due to their over-expression in tumor cells and their involvement in cancer biology. The main localization of these receptors strongly suggests their potential role in ER unfolded protein response (ER-UPR), a condition frequently occurring in several pathological settings, including cancer. Our group has recently identified RC-106, a novel pan-SR modulator with good in vitro antiproliferative activities toward a panel of different cancer cell lines. In the present study, we investigated the in vitro properties and pharmacological profile of RC-106 in PC cell lines with the aim to identify a potential lead candidate for the treatment of this tumor.

Methods: Pancreatic cancer cell lines Panc-1, Capan-1, and Capan-2 have been used in all experiments. S1R and TMEM97/S2R expression in PC cell lines was quantified by Real-Time qRT-PCR and Western Blot experiments. MTS assay was used to assess the antiproliferative effect of RC-106. The apoptotic properties of RC-106 was evaluated by TUNEL and caspase activation assays. GRP78/BiP, ATF4, and CHOP was quantified to evaluate ER-UPR. Proteasome activity was investigated by a specific fluorescent-based assay. Scratch wound healing assay was used to asses RC-106 effect on cell migration. In addition, we delineated the in vivo pharmacokinetic profile and pancreas distribution of RC-106 in male CD-1 mice.

Results: Panc-1, Capan-1, and Capan-2 express both SRs. RC-106 exerts an antiproliferative and pro-apoptotic effect in all examined cell lines. Cells exposure to RC-106 induces the increase of the expression of ER-UPR related proteins, and the inhibition of proteasome activity. Moreover, RC-106 is able to decrease PC cell lines motility. The in vivo results show that RC-106 is more concentrated in pancreas than plasma.

Conclusion: Overall, our data evidenced that the pan-SR modulator RC-106 is an optimal candidate for in vivo studies in animal models of PC.

Epitope mapping of anti-PGRMC1 antibodies reveals the non-conventional membrane topology of PGRMC1 on the cell surface

Progesterone receptor membrane component1 (PGRMC1) is a heme-binding protein involved in cancers and Alzheimer's disease. PGRMC1 consists of a short N-terminal extracellular or luminal domain, a single membrane-spanning domain, and a long cytoplasmic domain. Previously, we generated two monoclonal antibodies (MAbs) 108-B6 and 4A68 that recognize cell surface-expressed PGRMC1 (csPGRMC1) on human pluripotent stem cells and some cancer cells. In this study, flow cytometric analysis found that an anti-PGRMC1 antibody recognizing the N-terminus of PGRMC1 could not bind to csPGRMC1 on cancer cells, and 108-B6 and 4A68 binding to csPGRMC1 was inhibited by trypsin treatment, suggesting that the epitopes of 108-B6 and 4A68 are trypsin-sensitive. To examine the epitope specificity of 108-B6 and 4A68, glutathione-S-transferase (GST)-fused PGRMC1 mutants were screened to identify the epitopes targeted by the antibodies. The result showed that 108-B6 and 4A68 recognized C-terminal residues 183-195 and 171-182, respectively, of PGRMC1, where trypsin-sensitive sites are located. A polyclonal anti-PGRMC1 antibody raised against the C-terminus of PGRMC1 could also recognized csPGRMC1 in a trypsin-sensitive manner, suggesting that the C-terminus of csPGRMC1 is exposed on the cell surface. This finding reveals that csPGRMC1 has a non-conventional plasma membrane topology, which is different from that of intracellular PGRMC1.

Sigma-2 receptor: past, present and perspectives on multiple therapeutic exploitations

Identification of sigma-2 receptor (sig-2R) has been controversial. Nevertheless, interest in sig-2R is high for its overexpression in tumors and potentials in oncology. Additionally, sig-2R antagonists inhibit Aβ binding at neurons, blocking the cognitive impairments of Alzheimer's disease. The most representative classes of sig-2R ligands are herein treated with focus on compounds that served to study sig-2R biology and to produce sig-2R: fluorescent ligands; multifunctional anticancer agents; and targeting nanoparticles. Although fluorescent ligands serve as ‘green’ pharmacological tools, sig-2R-multifunctional conjugates and sig-2R-targeted nanoparticles show how sig-2R targeting increases the activity of anticancer drugs in tumors with reduced toxicity. Altogether, this review draws a picture of the multiple approaches of sig-2R ligands in cancer therapy and as Alzheimer's disease modifying disease agents.

Sigma Receptors as Endoplasmic Reticulum Stress "Gatekeepers" and their Modulators as Emerging New Weapons in the Fight Against Cancer

Despite the interest aroused by sigma receptors (SRs) in the area of oncology, their role in tumor biology remains enigmatic. The predominant subcellular localization and main site of activity of SRs are the endoplasmic reticulum (ER). Current literature data, including recent findings on the sigma 2 receptor subtype (S2R) identity, suggest that SRs may play a role as ER stress gatekeepers. Although SR endogenous ligands are still unknown, a wide series of structurally unrelated compounds able to bind SRs have been identified. Currently, the identification of novel antiproliferative molecules acting via SR interaction is a challenging task for both academia and industry, as shown by the fact that novel anticancer drugs targeting SRs are in the preclinical-stage pipeline of pharmaceutical companies (i.e., Anavex Corp. and Accuronix). So far, no clinically available anticancer drugs targeting SRs are still available. The present review focuses literature advancements and provides a state-of-the-art overview of SRs, with emphasis on their involvement in cancer biology and on the role of SR modulators as anticancer agents. Findings from preclinical studies on novel anticancer drugs targeting SRs are presented in brief.

Function and structural regulation of the carbon monoxide (CO)-responsive membrane protein PGRMC1

Progesterone receptor membrane associated component 1 is a multifunctional heme-binding protein that plays a role in several biological processes such as tumor progression, metabolic regulation, and viability control of nerve cells. Notably, progesterone receptor membrane associated component 1 is highly expressed in various types of cancer cells, and facilitates cancer proliferation and chemoresistance. Recently, progesterone receptor membrane associated component 1 structure has been explored by X-ray crystallographic analysis. Interestingly, whereas apo- progesterone receptor membrane associated component 1 exists as a monomer, the heme-bound progesterone receptor membrane associated component 1 converts into a stable dimer by forming a unique heme-heme stacking structure, leading to activation of epidermal growth factor receptor signaling and chemoresistance in cancer cells. Furthermore, the gas mediator carbon monoxide inhibits progesterone receptor membrane associated component 1-mediated activation in cancer cells by dissociating the heme-stacking dimer of progesterone receptor membrane associated component 1. The dynamic structural regulation of progesterone receptor membrane associated component 1 will provide new insights for understanding the mechanisms underlying its various functions.

PGRMC1 localization and putative function in the nucleolus of bovine granulosa cells and oocytes

Progesterone receptor membrane component-1 (PGRMC1) is a highly conserved multifunctional protein that is found in numerous systems, including reproductive system. Interestingly, PGRMC1 is expressed at several intracellular locations, including the nucleolus. The aim of this study is to investigate the functional relationship between PGRMC1 and nucleolus. Immunofluorescence experiments confirmed PGRMC1's nucleolar localization in cultured bovine granulosa cells (bGC) and oocytes. Additional experiments conducted on bGC revealed that PGRMC1 co-localizes with nucleolin (NCL), a major nucleolar protein. Furthermore, small interfering RNA (RNAi)-mediated gene silencing experiments showed that when PGRMC1 expression was depleted, NCL translocated from the nucleolus to the nucleoplasm. Similarly, oxidative stress induced by hydrogen peroxide (H2O2) treatment, reduced PGRMC1 immunofluorescent signal in the nucleolus and increased NCL nucleoplasmic signal, when compared to non-treated cells. Although PGRMC1 influenced NCL localization, a direct interaction between these two proteins was not detected using in situ proximity ligation assay. This suggests the involvement of additional molecules in mediating the co-localization of PGRMC1 and nucleolin. Since nucleolin translocates into the nucleoplasm in response to various cellular stressors, PGRMC1's ability to regulate its localization within the nucleolus is likely an important component of mechanism by which cells response to stress. This concept is consistent with PGRMC1's well-described ability to promote ovarian cell survival and provides a rationale for future studies on PGRMC1, NCL and the molecular mechanism by which these two proteins protect against the adverse effect of cellular stressors, including oxidative stress.

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.

Multifunctional thiosemicarbazones and deconstructed analogues as a strategy to study the involvement of metal chelation, Sigma-2 (σ2) receptor and P-gp protein in the cytotoxic action: In vitro and in vivo activity in pancreatic tumors

The aggressiveness of pancreatic cancer urgently requires more efficient treatment options. Because the sigma-2 (σ2) receptor was recently proposed as a promising target for pancreatic cancer therapy, we explored our previously developed multifunctional thiosemicarbazones, designed to synergistically impair cell energy levels, by targeting σ2 and P-gp proteins and chelating Iron. A deconstruction approach was herein applied by removing one function at a time from the potent multifunctional thiosemicarbazones 1 and 2, to investigate the contribution to cytotoxicity of each target involved. The results from in vitro (panel of pancreatic tumor cells) and in vivo experiments (C57BL/6 bearing KP02 tumor), suggest that while the multifunctional activity was not required for the antitumor activity of these thiosemicarbazones, σ2-targeting appeared to allow alternative tumor cell death mechanisms, leading to potent and less toxic off-targets toxicities compared to other thiosemicarbazones devoid of σ2-targeting.

Sigma Receptor (σR) Ligands with Antiproliferative and Anticancer Activity

Sigma receptor (σR) ligands have proven to be useful as cancer diagnostics and anticancer therapeutics and their ligands have been developed as molecular probes in oncology. Moreover, various σR ligands generate cancer cell death in vitro and in vivo. These σR ligands have exhibited promising results against numerous human and rodent cancers and are investigated under preclinical and clinical study trials, indicating a new category of drugs in cancer therapy.

Membrane Associated Progesterone Receptors: Promiscuous Proteins with Pleiotropic Functions - Focus on Interactions with Cytochromes P450

Membrane-associated progesterone receptors (MAPR) are a group of four rather small, partially homologous proteins, which share a similar non-covalent heme-binding domain that is related to cytochrome b5, a well-known functional interaction partner of microsomal cytochrome P450 (CYP) monooxygenase systems. Apart from their structural similarities the four proteins progesterone membrane component 1 (PGRMC1, also referred to as IZA, sigma-2 receptor, Dap1), PGRMC2, neudesin (NENF) and neuferricin (CYB5D2) display surprisingly divergent and multifunctional physiological properties related to cholesterol/steroid biosynthesis, drug metabolism and response, iron homeostasis, heme trafficking, energy metabolism, autophagy, apoptosis, cell cycle regulation, cell migration, neural functions, and tumorigenesis and cancer progression. The purpose of this mini-review is to briefly summarize the structural and functional properties of MAPRs with particular focus on their interactions with the CYP system. For PGRMC1, originally identified as a non-canonical progesterone-binding protein that mediates some immediate non-genomic actions of progesterone, available evidence indicates mainly activating interactions with steroidogenic CYPs including CYP11A1, CYP21A2, CYP17, CYP19, CYP51A1, and CYP61A1, while interactions with drug metabolizing CYPs including CYP2C2, CYP2C8, CYP2C9, CYP2E1, and CYP3A4 were either ineffective or slightly inhibitory. For the other MAPRs the evidence is so far less conclusive. We also point out that experimental limitations question some of the previous conclusions. Use of appropriate model systems should help to further clarify the true impact of these proteins on CYP-mediated metabolic pathways.

Conditional Ablation of Progesterone Receptor Membrane Component 2 Causes Female Premature Reproductive Senescence

The nonclassical progesterone receptors progesterone receptor membrane component (PGRMC) 1 and PGRMC2 have been implicated in regulating cell survival of endometrial and ovarian cells in vitro and are abundantly expressed in these cell types. The objective of this study was to determine if Pgrmc1 and Pgrmc2 are essential for normal female reproduction. To accomplish this objective, Pgrmc1 and/or Pgrmc2 floxed mice (Pgrmc2fl/fl and Pgrmc1/2fl/fl) were crossed with Pgr-cre mice, which resulted in the conditional ablation of Pgrmc1 and/or Pgrmc2 from female reproductive tissues (i.e.,Pgrmc2d/d and Pgrmc1/2d/d mice). A breeding trial revealed that conditional ablation of Pgrmc2 initially led to subfertility, with Pgrmc2d/d female mice producing 47% fewer pups/litter than Pgrmc2fl/fl mice (P = 0.001). Pgrmc2d/d mice subsequently underwent premature reproductive senescence by parities 2 to 5, producing 37.8% fewer litters overall during the trial compared with Pgrmc2fl/fl mice (P = 0.020). Similar results were observed with Pgrmc1/2d/d mice. Based on ovarian morphology and serum P4, the subfertility/infertility was not due to faulty ovulation or luteal insufficiency. Rather an analysis of midgestation implantation sites revealed that postimplantation embryonic death was the major cause of the subfertility/infertility. As with our previous report of Pgrmc1d/d mice, Pgrmc2d/d and Pgrmc1/2d/d mice developed endometrial cysts consistent with accelerated aging of this tissue. Given the timing of postimplantation embryonic demise, uterine decidualization may be disrupted in mice deficient in PGRMC2 or PGRMC1/2. Overall, this study revealed that Pgrmc1 and/or Pgrmc2 are required for the maintenance of uterine histoarchitecture and normal female reproductive lifespan.

PGRMC1-dependent autophagy by hyperoside induces apoptosis and sensitizes ovarian cancer cells to cisplatin treatment

Cisplatin treatment some times leads to chemoresistance, which is now acknowledged partially due to the inductive expression of progesterone receptor membrane component (PGRMC)1 in ovarian cancer cells. PGRMC1 enhances autophagy, activates cytochrome p450, and inveigles signaling pathways to promote cell survival and reduce the effect of drug treatments. In this study, we give first line evidence that hyperoside inhibits cell viability, triggers autophagy and apoptosis in ovarian cancer cell lines. Mechanistically, PGRMC1-dependent autophagy was utilized by hyperoside to induce apoptotic cell death. Hyperoside induced the conversion of LC3B-I to LC3B-II and the formation of autophagosomes in ovarian cancer cells. Notably, PGRMC1 colocolized with LC3B‑II, and PGRMC1 overexpression enhanced hyperoside-induced autophagy and apoptosis, while PGRMC1 knockdown abrogated the action. Additionally, AKT signaling and Bcl-2 family were also involved in the hyperoside-induced autophagy and apoptosis. Importantly, in cisplatin-resistant ovarian cancer cells where PGRMC1 was overexpressed, hyperoside sensitized the cells to cisplatin treatment. Together these findings indicate hyperoside functions as a complementary therapy for ovarian cancer patients receiving platinum-based therapy.

Sigma-2 receptor agonist derivatives of 1-Cyclohexyl-4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]piperazine (PB28) induce cell death via mitochondrial superoxide production and caspase activation in pancreatic cancer

Background

Despite considerable efforts by scientific research, pancreatic cancer is the fourth leading cause of cancer related mortalities. Sigma-2 receptors, which are overexpressed in several tumors, represent promising targets for triggering selective pancreatic cancer cells death.

Methods

We selected five differently structured high-affinity sigma-2 ligands (PB28, PB183, PB221, F281 and PB282) to study how they affect the viability of diverse pancreatic cancer cells (human cell lines BxPC3, AsPC1, Mia PaCa-2, and Panc1 and mouse Panc-02, KCKO and KP-02) and how this is reflected in vivo in a tumor model.

Results

Important cytotoxicity was shown by the compounds in the aggressive Panc02 cells, where cytotoxic activity was caspase-3 independent for four of the five compounds. However, both cytotoxicity and caspase-3 activation involved generation of Reactive Oxygen Species (ROS), which could be partially reverted by the lipid antioxidant α-tocopherol, but not by the hydrophilic N-acetylcysteine (NAC) indicating crucial differences in the intracellular sites exposed to oxidative stress induced by sigma-2 receptor ligands. Importantly, all the compounds strongly increased the production of mitochondrial superoxide radicals except for PB282. Despite a poor match between in vitro and the in vivo efficacy, daily treatment of C57BL/6 mice bearing Panc02 tumors resulted in promising effects with PB28 and PB282 which were similar compared to the current standard-of-care chemotherapeutic gemcitabine without showing signs of systemic toxicities.

Conclusions

Overall, this study identified differential sensitivities of pancreatic cancer cells to structurally diverse sigma-2 receptor ligands. Of note, we identified the mitochondrial superoxide pathway as a previously unrecognized sigma-2 receptor-activated process, which encourages further studies on sigma-2 ligand-mediated cancer cell death for the targeted treatment of pancreatic tumors.

Sigma-2 receptor and progesterone receptor membrane component 1 (PGRMC1) are two different proteins: Proofs by fluorescent labeling and binding of sigma-2 receptor ligands to PGRMC1

A controversial relationship between sigma-2 and progesterone receptor membrane component 1 (PGRMC1) proteins, both representing promising targets for the therapy and diagnosis of tumors, exists since 2011, when the sigma-2 receptor was reported to be identical to PGRMC1. Because a misidentification of these proteins will lead to biased future research hampering the possible diagnostic and therapeutic exploitation of the two targets, there is the need to solve the debate on their identity. With this aim, we have herein investigated uptake and distribution of structurally different fluorescent sigma-2 receptor ligands by flow cytometry and confocal microscopy in MCF7 cells, where together with intrinsic sigma-2 receptors, PGRMC1 was constitutively present or alternatively silenced or overexpressed. HCT116 cells, with constitutive or silenced PGRMC1, were also studied. These experiments showed that the fluorescent sigma-2 ligands bind to their receptor irrespective of PGRMC1 expression. Furthermore, isothermal titration calorimetry was conducted to examine if DTG and PB28, two structurally distinct nanomolar affinity sigma-2 ligands, bind to purified PGRMC1 proteins that have recently been revealed to form both apo-monomeric and heme-mediated dimeric forms. While no binding to apo-PGRMC1 monomer was detected, a micromolar affinity to heme-mediated dimerized PGRMC1 was demonstrated in DTG but not in PB28. The current data provide evidence that sigma-2 receptor and PGRMC1 are not identical, paving the pathway for future unbiased research in which these two attractive targets are treated as different proteins while the identification of the true sigma-2 protein further needs to be pursued.

A Novel Role for Progesterone Receptor Membrane Component 1 (PGRMC1): A Partner and Regulator of Ferrochelatase

Heme is an iron-containing cofactor essential for multiple cellular processes and fundamental activities such as oxygen transport. To better understand the means by which heme synthesis is regulated during erythropoiesis, affinity purification coupled with mass spectrometry (MS) was performed to identify putative protein partners interacting with ferrochelatase (FECH), the terminal enzyme in the heme biosynthetic pathway. Both progesterone receptor membrane component 1 (PGRMC1) and progesterone receptor membrane component 2 (PGRMC2) were identified in these experiments. These interactions were validated by reciprocal affinity purification followed by MS analysis and immunoblotting. The interaction between PGRMC1 and FECH was confirmed in vitro and in HEK 293T cells, a non-erythroid cell line. When cells that are recognized models for erythroid differentiation were treated with a small molecule inhibitor of PGRMC1, AG-205, there was an observed decrease in the level of hemoglobinization relative to that of untreated cells. In vitro heme transfer experiments showed that purified PGRMC1 was able to donate heme to apo-cytochrome b5. In the presence of PGRMC1, in vitro measured FECH activity decreased in a dose-dependent manner. Interactions between FECH and PGRMC1 were strongest for the conformation of FECH associated with product release, suggesting that PGRMC1 may regulate FECH activity by controlling heme release. Overall, the data illustrate a role for PGRMC1 in regulating heme synthesis via interactions with FECH and suggest that PGRMC1 may be a heme chaperone or sensor.

Synthesis and biological evaluation of new aryl-alkyl(alkenyl)-4-benzylpiperidines, novel Sigma Receptor (SR) modulators, as potential anticancer-agents

In the early 2000s, the Sigma Receptor (SR) family was identified as potential "druggable" target in cancer treatment. Indeed, high density of SRs was found in breast, lung, and prostate cancer cells, supporting the idea that SRs could play a role in tumor growth and progression. Moreover, a link between the degree of SR expression and tumor aggressiveness has been postulated, justified by the presence of SRs in high metastatic-potential cancer cells. As a consequence, considerable efforts have been devoted to the development of small molecules endowed with good affinity towards the two SR subtypes (S1R and S2R) with potential anticancer activity. Herein, we report the synthesis and biological profile of aryl-alkyl(alkenyl)-4-benzylpiperidine derivatives - as novel potential anticancer drugs targeting SR. Among them, 3 (RC-106) exhibited a preclinical profile of antitumor efficacy on a panel of cell lines representative of different cancer types (i.e. Paca3, MDA-MB 231) expressing both SRs, and emerged as a hit compound of a new class of SR modulators potentially useful for the treatment of cancer disease.