Nutrigenomic underpinnings of intestinal stem cells in inflammatory bowel disease and colorectal cancer development.

Food-gene interaction has been identified as a leading risk factor for inflammatory bowel disease (IBD) and colorectal cancer (CRC). Accordingly, nutrigenomics emerges as a new approach to identify biomarkers and therapeutic targets for these two strongly associated gastrointestinal diseases. Recent studies in stem cell biology have further shown that diet and nutrition signal to intestinal stem cells (ISC) by altering nutrient-sensing transcriptional activities, thereby influencing barrier integrity and susceptibility to inflammation and tumorigenesis. This review recognizes the dietary factors related to both CRC and IBD and investigates their impact on the overlapping transcription factors governing stem cell activities in homeostasis and post-injury responses. Our objective is to provide a framework to study the food-gene regulatory network of disease-contributing cells and inspire new nutrigenomic approaches for detecting and treating diet-related IBD and CRC.

Constitutive internalisation of EP2 differentially regulates G protein signalling.

The prostanoid G protein-coupled receptor (GPCR) EP2 is widely expressed and implicated in endometriosis, osteoporosis, obesity, pre-term labour and cancer. Internalisation and intracellular trafficking are critical for shaping GPCR activity, yet little is known regarding the spatial programming of EP2 signalling and whether this can be exploited pharmacologically. Using three EP2-selective ligands that favour activation of different EP2 pathways, we show that EP2 undergoes limited agonist-driven internalisation but is constitutively internalised via dynamin-dependent, ß-arrestin-independent pathways. EP2 was constitutively trafficked to early and very early endosomes (VEE), which was not altered by ligand activation. APPL1, a key adaptor and regulatory protein of the VEE, did not impact EP2 agonist-mediated cAMP. Internalisation was required for ~70% of the acute butaprost- and AH13205-mediated cAMP signalling, yet PGN9856i, a Gαs-biased agonist, was less dependent on receptor internalisation for its cAMP signalling, particularly in human term pregnant myometrial cells that endogenously express EP2. Inhibition of EP2 internalisation partially reduced calcium signalling activated by butaprost or AH13205 and had no effect on PGE2 secretion. This indicates an agonist-dependent differential spatial requirement for Gαs and Gαq/11 signalling and a role for plasma membrane-initiated Gαq/11-Ca2+-mediated PGE2 secretion. These findings reveal a key role for EP2 constitutive internalisation in its signalling and potential spatial bias in mediating its downstream functions. This, in turn, could highlight important considerations for future selective targeting of EP2 signalling pathways.

Pharmacological Characterization of Low Molecular Weight Biased Agonists at the Follicle Stimulating Hormone Receptor.

Follicle-stimulating hormone receptor (FSHR) plays a key role in reproduction through the activation of multiple signaling pathways. Low molecular weight (LMW) ligands composed of biased agonist properties are highly valuable tools to decipher complex signaling mechanisms as they allow selective activation of discrete signaling cascades. However, available LMW FSHR ligands have not been fully characterized yet. In this context, we explored the pharmacological diversity of three benzamide and two thiazolidinone derivatives compared to FSH. Concentration/activity curves were generated for Gαs, Gαq, Gαi, ß-arrestin 2 recruitment, and cAMP production, using BRET assays in living cells. ERK phosphorylation was analyzed by Western blotting, and CRE-dependent transcription was assessed using a luciferase reporter assay. All assays were done in either wild-type, Gαs or ß-arrestin 1/2 CRISPR knockout HEK293 cells. Bias factors were calculated for each pair of read-outs by using the operational model. Our results show that each ligand presented a discrete pharmacological efficacy compared to FSH, ranging from super-agonist for ß-arrestin 2 recruitment to pure Gαs bias. Interestingly, LMW ligands generated kinetic profiles distinct from FSH (i.e., faster, slower or transient, depending on the ligand) and correlated with CRE-dependent transcription. In addition, clear system biases were observed in cells depleted of either Gαs or ß-arrestin genes. Such LMW properties are useful pharmacological tools to better dissect the multiple signaling pathways activated by FSHR and assess their relative contributions at the cellular and physio-pathological levels.

Follicle-Stimulating Hormone Induces Lipid Droplets via Gαi/o and ß-Arrestin in an Endometrial Cancer Cell Line.

Follicle-stimulating hormone (FSH) and its G protein-coupled receptor, FSHR, represents a paradigm for receptor signaling systems that activate multiple and complex pathways. Classically, FSHR activates Gαs to increase intracellular levels of cAMP, but its ability to activate other G proteins, and ß-arrestin-mediated signaling is well documented in many different cell systems. The pleiotropic signal capacity of FSHR offers a mechanism for how FSH drives multiple and dynamic downstream functions in both gonadal and non-gonadal cell types, including distinct diseases, and how signal bias may be achieved at a pharmacological and cell system-specific manner. In this study, we identify an additional mechanism of FSH-mediated signaling and downstream function in the endometrial adenocarcinoma Ishikawa cell line. While FSH did not induce increases in cAMP levels, this hormone potently activated pertussis toxin sensitive Gαi/o signaling. A selective allosteric FSHR ligand, B3, also activated Gαi/o signaling in these cells, supporting a role for receptor-mediated activation despite the low levels of FSHR mRNA. The low expression levels may attribute to the lack of Gαs/cAMP signaling as increasing FSHR expression resulted in FSH-mediated activation of the Gαs pathway. Unlike prior reports for FSH-mediated Gαs/cAMP signaling, FSH-mediated Gαi/o signaling was not affected by inhibition of dynamin-dependent receptor internalization. While chronic FSH did not alter cell viability, FSH was able to increase lipid droplet size. The ß-arrestins are key adaptor proteins known to regulate FSHR signaling. Indeed, a rapid, FSH-dependent increase in interactions between ß-arrestin1 and Gαi1 was observed via NanoBiT complementation in Ishikawa cells. Furthermore, both inhibition of Gαi/o signaling and siRNA knockdown of ß-arrestin 1/2 significantly reduced FSH-induced lipid droplet accumulation, implying a role for a Gαi/o/ß-arrestin complex in FSH functions in this cell type. As FSH/FSHR has been implicated in distinct hormone-dependent cancers, including endometrial cancer, analysis of the cancer genome database from 575 human endometrial adenocarcinoma tumors revealed that a subpopulation of samples expressed FSHR. Overall, this study highlights a novel mechanism for FSHR signal pleiotropy that may be exploited for future personalized therapeutic approaches.

Membrane Estrogen Receptor (GPER) and Follicle-Stimulating Hormone Receptor (FSHR) Heteromeric Complexes Promote Human Ovarian Follicle Survival.

Classically, follicle-stimulating hormone receptor (FSHR)-driven cAMP-mediated signaling boosts human ovarian follicle growth and oocyte maturation. However, contradicting in vitro data suggest a different view on physiological significance of FSHR-mediated cAMP signaling. We found that the G-protein-coupled estrogen receptor (GPER) heteromerizes with FSHR, reprogramming cAMP/death signals into proliferative stimuli fundamental for sustaining oocyte survival. In human granulosa cells, survival signals are missing at high FSHR:GPER ratio, which negatively impacts follicle maturation and strongly correlates with preferential Gαs protein/cAMP-pathway coupling and FSH responsiveness of patients undergoing controlled ovarian stimulation. In contrast, FSHR/GPER heteromers triggered anti-apoptotic/proliferative FSH signaling delivered via the Gßγ dimer, whereas impairment of heteromer formation or GPER knockdown enhanced the FSH-dependent cell death and steroidogenesis. Therefore, our findings indicate how oocyte maturation depends on the capability of GPER to shape FSHR selective signals, indicating hormone receptor heteromers may be a marker of cell proliferation.

Gene Expression in Granulosa Cells From Small Antral Follicles From Women With or Without Polycystic Ovaries.

CONTEXT: Polycystic ovary syndrome (PCOS) is the most common cause of anovulation. A key feature of PCOS is arrest of follicles at the small- to medium-sized antral stage. OBJECTIVE AND DESIGN: To provide further insight into the mechanism of follicle arrest in PCOS, we profiled (i) gonadotropin receptors; (ii) characteristics of aberrant steroidogenesis; and (iii) expression of anti-Müllerian hormone (AMH) and its receptor in granulosa cells (GCs) from unstimulated, human small antral follicles (hSAFs) and from granulosa lutein cells (GLCs). SETTING: GCs from hSAFs were collected at the time of cryopreservation of ovarian tissue for fertility preservation and GLCs collected during oocyte aspiration before in vitro fertilization/intracytoplasmic sperm injection. PARTICIPANTS: We collected hSAF GCs from 31 women (98 follicles): 10 with polycystic ovaries (PCO) and 21 without. GLCs were collected from 6 women with PCOS and 6 controls undergoing IVF. MAIN OUTCOME MEASURES: Expression of the following genes: LHCGR, FSHR, AR, INSR, HSD3B2, CYP11A1, CYP19, STAR, AMH, AMHR2, FST, INHBA, INHBB in GCs and GLCs were compared between women with PCO and controls. RESULTS: GCs in hSAFs from women with PCO showed higher expression of LHCGR in a subset (20%) of follicles. Expression of FSHR (P < 0.05), AR (P < 0.05), and CYP11A1 (P < 0.05) was lower, and expression of CYP19A1 (P < 0.05), STAR (P < 0.05), HSD3B2 (P = NS), and INHBA (P < 0.05) was higher in PCO GCs. Gene expression in GL cells differed between women with and without PCOS but also differed from that in GCs. CONCLUSIONS: Follicle arrest in PCO is characterized in GCs by differential regulation of key genes involved in follicle growth and function.

Integration of GPCR Signaling and Sorting from Very Early Endosomes via Opposing APPL1 Mechanisms.

Endocytic trafficking is a critical mechanism for cells to decode complex signaling pathways, including those activated by G-protein-coupled receptors (GPCRs). Heterogeneity in the endosomal network enables GPCR activity to be spatially restricted between early endosomes (EEs) and the recently discovered endosomal compartment, the very early endosome (VEE). However, the molecular machinery driving GPCR activity from the VEE is unknown. Using luteinizing hormone receptor (LHR) as a prototype GPCR for this compartment, along with additional VEE-localized GPCRs, we identify a role for the adaptor protein APPL1 in rapid recycling and endosomal cAMP signaling without impacting the EE-localized ß2-adrenergic receptor. LHR recycling is driven by receptor-mediated Gαs/cAMP signaling from the VEE and PKA-dependent phosphorylation of APPL1 at serine 410. Receptor/Gαs endosomal signaling is localized to microdomains of heterogeneous VEE populations and regulated by APPL1 phosphorylation. Our study uncovers a highly integrated inter-endosomal communication system enabling cells to tightly regulate spatially encoded signaling.

Allosteric Modulation of the Calcium-sensing Receptor Rectifies Signaling Abnormalities Associated with G-protein α-11 Mutations Causing Hypercalcemic and Hypocalcemic Disorders.

Germline loss- and gain-of-function mutations of G-protein α-11 (Gα11), which couples the calcium-sensing receptor (CaSR) to intracellular calcium (Ca(2+) i) signaling, lead to familial hypocalciuric hypercalcemia type 2 (FHH2) and autosomal dominant hypocalcemia type 2 (ADH2), respectively, whereas somatic Gα11 mutations mediate uveal melanoma development by constitutively up-regulating MAPK signaling. Cinacalcet and NPS-2143 are allosteric CaSR activators and inactivators, respectively, that ameliorate signaling disturbances associated with CaSR mutations, but their potential to modulate abnormalities of the downstream Gα11 protein is unknown. This study investigated whether cinacalcet and NPS-2143 may rectify Ca(2+) i alterations associated with FHH2- and ADH2-causing Gα11 mutations, and evaluated the influence of germline gain-of-function Gα11 mutations on MAPK signaling by measuring ERK phosphorylation, and assessed the effect of NPS-2143 on a uveal melanoma Gα11 mutant. WT and mutant Gα11 proteins causing FHH2, ADH2 or uveal melanoma were transfected in CaSR-expressing HEK293 cells, and Ca(2+) i and ERK phosphorylation responses measured by flow-cytometry and Alphascreen immunoassay following exposure to extracellular Ca(2+) (Ca(2+) o) and allosteric modulators. Cinacalcet and NPS-2143 rectified the Ca(2+) i responses of FHH2- and ADH2-associated Gα11 loss- and gain-of-function mutations, respectively. ADH2-causing Gα11 mutations were demonstrated not to be constitutively activating and induced ERK phosphorylation following Ca(2+) o stimulation only. The increased ERK phosphorylation associated with ADH2 and uveal melanoma mutants was rectified by NPS-2143. These findings demonstrate that CaSR-targeted compounds can rectify signaling disturbances caused by germline and somatic Gα11 mutations, which respectively lead to calcium disorders and tumorigenesis; and that ADH2-causing Gα11 mutations induce non-constitutive alterations in MAPK signaling.

Arachidonic acid-dependent gene regulation during preadipocyte differentiation controls adipocyte potential.

Arachidonic acid (AA) is a major PUFA that has been implicated in the regulation of adipogenesis. We examined the effect of a short exposure to AA at different stages of 3T3-L1 adipocyte differentiation. AA caused the upregulation of fatty acid binding protein 4 (FABP4/aP2) following 24 h of differentiation. This was mediated by the prostaglandin F(2α) (PGF(2α)), as inhibition of cyclooxygenases or PGF(2α) receptor signaling counteracted the AA-mediated aP2 induction. In addition, calcium, protein kinase C, and ERK are all key elements of the pathway through which AA induces the expression of aP2. We also show that treatment with AA during the first 24 h of differentiation upregulates the expression of the transcription factor Fos-related antigen 1 (Fra-1) via the same pathway. Finally, treatment with AA for 24 h at the beginning of the adipocyte differentiation is sufficient to inhibit the late stages of adipogenesis through a Fra-1-dependent pathway, as Fra-1 knockdown rescued adipogenesis. Our data show that AA is able to program the differentiation potential of preadipocytes by regulating gene expression at the early stages of adipogenesis.

Spatially restricted G protein-coupled receptor activity via divergent endocytic compartments.

Postendocytic sorting of G protein-coupled receptors (GPCRs) is driven by their interactions between highly diverse receptor sequence motifs with their interacting proteins, such as postsynaptic density protein (PSD95), Drosophila disc large tumor suppressor (Dlg1), zonula occludens-1 protein (zo-1) (PDZ) domain proteins. However, whether these diverse interactions provide an underlying functional specificity, in addition to driving sorting, is unknown. Here we identify GPCRs that recycle via distinct PDZ ligand/PDZ protein pairs that exploit their recycling machinery primarily for targeted endosomal localization and signaling specificity. The luteinizing hormone receptor (LHR) and ß2-adrenergic receptor (B2AR), two GPCRs sorted to the regulated recycling pathway, underwent divergent trafficking to distinct endosomal compartments. Unlike B2AR, which traffics to early endosomes (EE), LHR internalizes to distinct pre-early endosomes (pre-EEs) for its recycling. Pre-EE localization required interactions of the LHR C-terminal tail with the PDZ protein GAIP-interacting protein C terminus, inhibiting its traffic to EEs. Rerouting the LHR to EEs, or EE-localized GPCRs to pre-EEs, spatially reprograms MAPK signaling. Furthermore, LHR-mediated activation of MAPK signaling requires internalization and is maintained upon loss of the EE compartment. We propose that combinatorial specificity between GPCR sorting sequences and interacting proteins dictates an unprecedented spatiotemporal control in GPCR signal activity.

The roles of prostaglandin EP 1 and 3 receptors in the control of human myometrial contractility.

CONTEXT: Prostaglandins are central to the processes of human labor. Prostaglandin E(2) (PGE(2)) synthesized within the uterus mediates cervical ripening and uterine contractions. PGE receptors, EP1 and EP3, may each mediate contractions, and represent potential therapeutic targets in the management of preterm labor. Studies of the expression and function of EP1 and EP3 in pregnant myometrium are inconsistent. OBJECTIVE: The objective of the study was to determine the relative importance of EP1 and EP3 in human myometrial contractility. DESIGN: We studied the expression of EP1 and EP3 in upper- and lower-segment myometrium at term in vivo and the effects of specific inhibitors on contractions in vitro. PATIENTS: Myometrial biopsies for both in vivo and in vitro studies were taken at cesarean section at term before or in labor in uncomplicated pregnancies. RESULTS: We found no differences in the expression of EP1 or EP3 at mRNA or protein level between the upper and lower segment myometrium and no overall changes associated with the onset of labor. Upon labor, EP1, but not EP3, was found to relocalize to the nucleus. In studies of contractility, we found no differences in spontaneous or PGE(2)-induced contractility between the upper- and lower-segment samples. Spontaneous contractions were inhibited by acetylsalicylic acid and were rescued by PGE(2). Although an EP1 antagonist, ZD6416, had no effect, an EP3 antagonist, L798106, inhibited both spontaneous and PGE(2)-induced contractions. CONCLUSIONS: EP3 is the primary receptor subtype that mediates PGE(2) induced contractility in human pregnant myometrium at term and represents a possible therapeutic target.

NADPH oxidase-derived reactive oxygen species mediate decidualization of human endometrial stromal cells in response to cyclic AMP signaling.

Differentiation of human endometrial stromal cells into specialized decidual cells is critical for embryo implantation and survival of the conceptus. Initiation of this differentiation process is strictly dependent on elevated cAMP levels, but the signal intermediates that control the expression of decidual marker genes, such as prolactin (PRL) and IGFBP1, remain poorly characterized. Here we show that cAMP-dependent decidualization can be attenuated or enhanced upon treatment of primary cultures with a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor (diphenylen iodonium) or activator (apocynin), respectively. Time-course analysis demonstrated that cAMP enhances endogenous reactive oxygen species production, apparent after 12 h of stimulation, which coincides with a dramatic increase in decidual PRL and IGFBP1 expression. Knockdown of the Rho GTPase RAC1, which disables activation of the NADPH oxidase homologs NADPH oxidase (NOX)-1, NOX-2, and NOX-3, had no effect on PRL or IGFBP1 expression. In contrast, silencing of NOX-4, or its cofactor p22(PHOX), inhibited the expression of both decidual markers. Finally, we show that the NOX-4/p22(PHOX) complex regulates the DNA-binding activity of CCAAT/enhancer binding protein-ß, a key regulator of human endometrial stromal cell differentiation. Thus, NOX-4 activation and reactive oxygen species signaling play an integral role in initiating the endometrial decidual response in preparation of pregnancy.

Essential role of Hrs in a recycling mechanism mediating functional resensitization of cell signaling.

Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is well known to terminate cell signaling by sorting activated receptors to the MVB/lysosomal pathway. Here we identify a distinct role of Hrs in promoting rapid recycling of endocytosed signaling receptors to the plasma membrane. This function of Hrs is specific for receptors that recycle in a sequence-directed manner, in contrast to default recycling by bulk membrane flow, and is distinguishable in several ways from previously identified membrane-trafficking functions of Hrs/Vps27p. In particular, Hrs function in sequence-directed recycling does not require other mammalian Class E gene products involved in MVB/lysosomal sorting, nor is receptor ubiquitination required. Mutational studies suggest that the VHS domain of Hrs plays an important role in sequence-directed recycling. Disrupting Hrs-dependent recycling prevented functional resensitization of the beta(2)-adrenergic receptor, converting the temporal profile of cell signaling by this prototypic G protein-coupled receptor from sustained to transient. These studies identify a novel function of Hrs in a cargo-specific recycling mechanism, which is critical to controlling functional activity of the largest known family of signaling receptors.

Gonadotropin-releasing hormone receptor-mediated growth suppression of immortalized LbetaT2 gonadotrope and stable HEK293 cell lines.

Continuous administration of GnRH analogs results in an inhibition of tumor growth that may be mediated in part by direct activation of GnRH receptors (GnRHRs) expressed on tumor cells. However, it is not fully understood how the GnRHR mediates these growth effects. This study aimed to determine how the presence or absence of this receptor in different cell types might affect the ability of GnRH to directly mediate growth effects. We demonstrate that continuous treatment with GnRH or a GnRH agonist (GnRHA) induces an antiproliferative effect in a gonadotrope-derived cell line (LbetaT2) and also in HEK293 cells stably expressing either the rat or human GnRHR. The antiproliferative effect was time and dose dependent and was verified using [3H]thymidine incorporation, light microscopy, and analysis of cell number. Inhibition was specifically mediated via the GnRHR, as cotreatment of the GnRHR-expressing cell lines with a GnRH antagonist blocked the growth-suppressive effect induced by GnRHA treatment. Cell cycle analysis revealed that GnRHA-treated HEK/GnRHR cell lines induced an accumulation of cells in the G2/M phase, whereas a G0/G1 arrest was observed in LbetaT2 cells. GnRHA treatment also caused a small, but significant, increase in apoptotic cells. This study provides evidence for a direct role for the GnRHR in mediating antiproliferative events in two cell systems, neither of which was derived from extrapituitary reproductive tumors. The ability to induce these effects, regardless of the cell system involved, has implications regarding the use of GnRH analogs for the treatment of endocrine-related disorders and tumors.