Cell-surface receptors transactivation mediated by g protein-coupled receptors

α-Ketoglutarate stimulates pendrin-dependent Cl- absorption in the mouse CCD through protein kinase C

α-Ketoglutarate (α-KG) is a citric acid cycle intermediate and a glutamine catabolism product. It is also the natural ligand of 2-oxoglutarate receptor 1 (OXGR1), a G_q protein-coupled receptor expressed on the apical membrane of intercalated cells. In the cortical collecting duct (CCD), Cl^-/[Formula: see text] exchange increases upon α-KG binding to the OXGR1. To determine the signaling pathway(s) by which α-KG stimulates Cl^- absorption, we examined α-KG-stimulated Cl^- absorption in isolated perfused mouse CCDs. α-KG increased electroneutral Cl^- absorption in CCDs from wild-type mice but had no effect on Cl^- absorption in pendrin knockout mice. Because G_q protein-coupled receptors activate PKC, we hypothesized that α-KG stimulates Cl^- absorption through PKC. If so, PKC agonists should mimic, whereas PKC inhibitors should abolish, α-KG-stimulated Cl^- absorption. Like α-KG, PKC agonist (phorbol-12,13-dibutyrate, 500 nM) application increased Cl^- absorption in wild-type but not in pendrin null CCDs. Moreover, PKC inhibitors (2.5 mM GF109203X and 20 nM calphostin C), Ca²⁺ chelators (BAPTA, 10-20 μM), or PKC-α or -δ gene ablation eliminated α-KG-stimulated Cl^- absorption. We have shown that STE20/SPS-1-related proline-alanine-rich protein kinase (SPAK) gene ablation increases urinary α-KG excretion, renal pendrin abundance, and CCD Cl^- absorption. However, in SPAK null CCDs, Cl^- absorption was not activated further by luminal α-KG application nor was Cl^- absorption reduced with the PKC inhibitor GF109203 . Thus SPAK gene ablation likely acts through a PKC-independent pathway to produce a chronic adaptive increase in pendrin function. In conclusion, α-KG stimulates pendrin-dependent Cl^-/[Formula: see text] exchange through a mechanism dependent on PKC and Ca²⁺ that involves PKC-α and PKC-δ.

Control of insulin secretion by GLP-1

Stimulation of insulin secretion by glucagon-like peptide-1 (GLP-1) and other gut-derived peptides is central to the incretin response to ingesting nutriments. Analogues of GLP-1, and inhibitors of its breakdown, have found widespread clinical use for the treatment of type 2 diabetes (T2D) and obesity. The release of these peptides underlies the improvements in glycaemic control and disease remission after bariatric surgery. Given therapeutically, GLP-1 analogues can lead to side effects including nausea, which limit dosage. Greater understanding of the interactions between the GLP-1 receptor (GLP-1R) and both the endogenous and artificial ligands therefore holds promise to provide more efficacious compounds. Here, we discuss recent findings concerning the signalling and trafficking of the GLP-1R in pancreatic beta cells. Leveraging "bias" at the receptor towards cAMP generation versus the recruitment of β-arrestins and extracellular signal-regulated kinases (ERK1/2) activation may allow the development of new analogues with significantly improved clinical efficacy. We describe how, unexpectedly, relatively low-affinity agonists, which prompt less receptor internalisation than the parent compound, provoke greater insulin secretion and consequent improvements in glycaemia.

EGFR activation triggers cellular hypertrophy and lysosomal disease in NAGLU-depleted cardiomyoblasts, mimicking the hallmarks of mucopolysaccharidosis IIIB

Mucopolysaccharidosis (MPS) IIIB is an inherited lysosomal storage disease caused by the deficiency of the enzyme α-N-acetylglucosaminidase (NAGLU) required for heparan sulfate (HS) degradation. The defective lysosomal clearance of undigested HS results in dysfunction of multiple tissues and organs. We recently demonstrated that the murine model of MPS IIIB develops cardiac disease, valvular abnormalities, and ultimately heart failure. To address the molecular mechanisms governing cardiac dysfunctions in MPS IIIB, we generated a model of the disease by silencing NAGLU gene expression in H9C2 rat cardiomyoblasts. NAGLU-depleted H9C2 exhibited accumulation of abnormal lysosomes and a hypertrophic phenotype. Furthermore, we found the specific activation of the epidermal growth factor receptor (EGFR), and increased phosphorylation levels of extracellular signal-regulated kinases (ERKs) in NAGLU-depleted H9C2. The inhibition of either EGFR or ERKs, using the selective inhibitors AG1478 and PD98059, resulted in the reduction of both lysosomal aberration and hypertrophy in NAGLU-depleted H9C2. We also found increased phosphorylation of c-Src and a reduction of the hypertrophic response in NAGLU-depleted H9C2 transfected with a dominant-negative c-Src. However, c-Src phosphorylation remained unaffected by AG1478 treatment, posing c-Src upstream EGFR activation. Finally, heparin-binding EGF-like growth factor (HB-EGF) protein was found overexpressed in our MPS IIIB cellular model, and its silencing reduced the hypertrophic response. These results indicate that both c-Src and HB-EGF contribute to the hypertrophic phenotype of NAGLU-depleted cardiomyoblasts by synergistically activating EGFR and subsequent signaling, thus suggesting that EGFR pathway inhibition could represent an effective therapeutic approach for MPS IIIB cardiac disease.

Tissue-specific transcriptome analyses provide new insights into GPCR signalling in adult Schistosoma mansoni

Schistosomes are blood-dwelling trematodes with global impact on human and animal health. Because medical treatment is currently based on a single drug, praziquantel, there is urgent need for the development of alternative control strategies. The Schistosoma mansoni genome project provides a platform to study and connect the genetic repertoire of schistosomes to specific biological functions essential for successful parasitism. G protein-coupled receptors (GPCRs) form the largest superfamily of transmembrane receptors throughout the Eumetazoan phyla, including platyhelminths. Due to their involvement in diverse biological processes, their pharmacological importance, and proven druggability, GPCRs are promising targets for new anthelmintics. However, to identify candidate receptors, a more detailed understanding of the roles of GPCR signalling in schistosome biology is essential. An updated phylogenetic analysis of the S. mansoni GPCR genome (GPCRome) is presented, facilitated by updated genome data that allowed a more precise annotation of GPCRs. Additionally, we review the current knowledge on GPCR signalling in this parasite and provide new insights into the potential roles of GPCRs in schistosome reproduction based on the findings of a recent tissue-specific transcriptomic study in paired and unpaired S. mansoni. According to the current analysis, GPCRs contribute to gonad-specific functions but also to nongonad, pairing-dependent processes. The latter may regulate gonad-unrelated functions during the multifaceted male-female interaction. Finally, we compare the schistosome GPCRome to that of another parasitic trematode, Fasciola, and discuss the importance of GPCRs to basic and applied research. Phylogenetic analyses display GPCR diversity in free-living and parasitic platyhelminths and suggest diverse functions in schistosomes. Although their roles need to be substantiated by functional studies in the future, the data support the selection of GPCR candidates for basic and applied studies, invigorating the exploitation of this important receptor class for drug discovery against schistosomes but also other trematodes.

Role of G protein-coupled receptors-microRNA interactions in gastrointestinal pathophysiology

G protein-coupled receptors (GPCRs) make up the largest transmembrane receptor superfamily in the human genome and are expressed in nearly all gastrointestinal cell types. Coupling of GPCRs and their respective ligands activates various phosphotransferases in the cytoplasm, and, thus, activation of GPCR signaling in intestine regulates many cellular and physiological processes. Studies in microRNAs (miRNAs) demonstrate that they represent critical epigenetic regulators of different pathophysiological responses in different organs and cell types in humans and animals. Here, we reviewed recent research on GPCR-miRNA interactions related to gastrointestinal pathophysiology, such as inflammatory bowel diseases, irritable bowel syndrome, and gastrointestinal cancers. Given that the presence of different types of cells in the gastrointestinal tract suggests the importance of cell-cell interactions in maintaining gastrointestinal homeostasis, we also discuss how GPCR-miRNA interactions regulate gene expression at the cellular level and subsequently modulate gastrointestinal pathophysiology through molecular regulatory circuits and cell-cell interactions. These studies helped identify novel molecular pathways leading to the discovery of potential biomarkers for gastrointestinal diseases.

Neurotensin receptor type 2 protects B-cell chronic lymphocytic leukemia cells from apoptosis

B-cell chronic lymphocytic leukemia (B-CLL) cells are resistant to apoptosis, and consequently accumulate to the detriment of normal B cells and patient immunity. Because current therapies fail to eradicate these apoptosis-resistant cells, it is essential to identify alternative survival pathways as novel targets for anticancer therapies. Overexpression of cell-surface G protein-coupled receptors drives cell transformation, and thus plays a critical role in malignancies. In this study, we identified neurotensin receptor 2 (NTSR2) as an essential driver of apoptosis resistance in B-CLL. NTSR2 was highly expressed in B-CLL cells, whereas expression of its natural ligand, neurotensin (NTS), was minimal in both B-CLL cells and patient plasma. Surprisingly, NTSR2 remained in a constitutively active phosphorylated state, caused not by a mutation-induced gain-of-function but rather by an interaction with the oncogenic tyrosine kinase receptor TrkB. Functional and biochemical characterization revealed that the NTSR2-TrkB interaction acts as a conditional oncogenic driver requiring the TrkB ligand brain-derived neurotrophic factor (BDNF), which unlike NTS is highly expressed in B-CLL cells. Together, NTSR2, TrkB and BDNF induce autocrine and/or paracrine survival pathways that are independent of mutation status and indolent or progressive disease course. The NTSR2-TrkB interaction activates survival signaling pathways, including the Src and AKT kinase pathways, as well as expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL. When NTSR2 was downregulated, TrkB failed to protect B-CLL cells from a drastic decrease in viability via typical apoptotic cell death, reflected by DNA fragmentation and Annexin V presentation. Together, our findings demonstrate that the NTSR2-TrkB interaction plays a crucial role in B-CLL cell survival, suggesting that inhibition of NTSR2 represents a promising targeted strategy for treating B-CLL malignancy.

GPCRs: Emerging anti-cancer drug targets

G protein-coupled receptors (GPCRs) constitute the largest and most diverse protein family in the human genome with over 800 members identified to date. They play critical roles in numerous cellular and physiological processes, including cell proliferation, differentiation, neurotransmission, development and apoptosis. Consequently, aberrant receptor activity has been demonstrated in numerous disorders/diseases, and as a result GPCRs have become the most successful drug target class in pharmaceuticals treating a wide variety of indications such as pain, inflammation, neurobiological and metabolic disorders. Many independent studies have also demonstrated a key role for GPCRs in tumourigenesis, establishing their involvement in cancer initiation, progression, and metastasis. Given the growing appreciation of the role(s) that GPCRs play in cancer pathogenesis, it is surprising to note that very few GPCRs have been effectively exploited in pursuit of anti-cancer therapies. The present review provides a broad overview of the roles that various GPCRs play in cancer growth and development, highlighting the potential of pharmacologically modulating these receptors for the development of novel anti-cancer therapeutics.

Receptor tyrosine kinases play a significant role in human oligodendrocyte inflammation and cell death associated with the Lyme disease bacterium Borrelia burgdorferi

Background

In previous studies, human oligodendrocytes were demonstrated to undergo apoptosis in the presence of Borrelia burgdorferi under an inflammatory milieu. Subsequently, we determined that the MEK/ERK pathway played a significant role in triggering downstream inflammation as well as apoptosis. However, the identity of receptors triggered by exposure to B. burgdorferi and initiating signaling events was unknown.

Methods

In this study, we explored the role of several TLR and EGFR/FGFR/PDGFR tyrosine kinase pathways in inducing inflammation in the presence of B. burgdorferi, using siRNA and/or inhibitors, in MO3.13 human oligodendrocytes. Cell death and apoptosis assays were also carried out in the presence or absence of specific receptor inhibitors along with the bacteria to determine the role of these receptors in apoptosis induction. The expression pattern of specific receptors with or without B. burgdorferi was also determined.

Results

TLRs 2 and 5 had a minimal role in inducing inflammation, particularly IL-6 production. Rather, their effect was mostly inhibitory, with TLR2 downregulation significantly upregulating CXCL8, and CXCL (1,2,3) levels, and TLR5 likely having a similar role in CXCL8, CXCL(1,2,3), and CCL5 levels. TLR4 contributed mostly towards CCL5 production. On the other hand, inhibition of all three EGF/FGF/PDGF receptors significantly downregulated all five of the inflammatory mediators tested even in the presence of B. burgdorferi. Their inhibition also downregulated overall cell death and apoptosis levels. The expression pattern of these receptors, as assessed by immunohistochemistry indicated that the PDGFRβ receptor was the most predominantly expressed receptor, followed by FGFR, although no significant differences were discernible between presence and absence of bacteria. Interestingly, inhibition of individual EGFR, FGFR, or PDGFR receptors did not indicate an individual role for any of these receptors in the overall downregulation of pathogenesis. Contrarily, suppression of FGFR signaling alone in the presence of bacteria significantly upregulated inflammatory mediator levels indicating that it might control an inhibitory pathway when triggered individually.

Conclusions

Unlike TLRs, EGF/FGF/PDGF receptors collectively play a significant role in the inflammation and apoptosis of human oligodendrocytes as mediated by B. burgdorferi. It is likely that these three receptors need to be triggered simultaneously to achieve this effect.

Anaplastic lymphoma kinase regulates binge-like drinking and dopamine receptor sensitivity in the ventral tegmental area

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase associated with alcohol dependence in humans and behavioral responses to ethanol in mice. To characterize the ability of ALK to control ethanol consumption, we treated mice with the ALK inhibitors TAE684 or alectinib before testing them for binge-like drinking using the drinking in the dark protocol. Mice treated with ALK inhibitors drank less ethanol than controls. In addition, TAE684 treatment abolished ethanol conditioned place preference, indicating that ALK regulates the rewarding properties of ethanol. Because the ventral tegmental area (VTA) is a key brain region involved in the rewarding effects of ethanol, we determined if Alk expression in the VTA is important for binge-like ethanol consumption. Mice expressing a short hairpin ribonucleic acid targeting Alk in the VTA drank less ethanol compared with controls. ALK is expressed on dopamine (DA) neurons in the VTA, suggesting that ALK might regulate their firing properties. Extracellular recordings of putative DA neurons in VTA slices demonstrated that ALK inhibition did not affect the ability of ethanol to stimulate, or DA to inhibit, the firing of DA neurons. However, inhibiting ALK attenuated the time-dependent reversal of inhibition produced by moderate concentrations of DA, suggesting that ALK affects DA D2 autoreceptor (D2R) desensitization. Altered desensitization of the D2R changes the firing of DA neurons and is predicted to affect DA levels and alcohol drinking. These data support the possibility that ALK might be a novel target of pharmacotherapy for reducing excessive alcohol consumption.

GABABR-Induced EGFR Transactivation Promotes Migration of Human Prostate Cancer Cells

G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) act in concert to regulate cell growth, proliferation, survival, and migration. Metabotropic GABA_B receptor (GABA_BR) is the GPCR for the main inhibitory neurotransmitter GABA in the central nervous system. Increased expression of GABA_BR has been detected in human cancer tissues and cancer cell lines, but the role of GABA_BR in these cells is controversial and the underlying mechanism remains poorly understood. Here, we investigated whether GABA_BR hijacks RTK signaling to modulate the fates of human prostate cancer cells. RTK array analysis revealed that the GABA_BR-specific agonist baclofen selectively induced the transactivation of EGFR in PC-3 cells. EGFR transactivation resulted in the activation of ERK1/2 by a mechanism that is dependent on G_i/o protein and that requires matrix metalloproteinase-mediated proligand shedding. Positive allosteric modulators (PAMs) of GABA_BR, such as CGP7930, rac-BHFF, and GS39783, can function as PAM agonists to induce EGFR transactivation and subsequent ERK1/2 activation. Moreover, both baclofen and CGP7930 promoted cell migration and invasion through EGFR signaling. In summary, our observations demonstrated that GABA_BR transactivated EGFR in a ligand-dependent mechanism to promote prostate cancer cell migration and invasion, thus providing new insights into developing a novel strategy for prostate cancer treatment by targeting neurotransmitter signaling.

Activation of muscarinic receptors prevents TNF-α-mediated intestinal epithelial barrier disruption through p38 MAPK

Intestinal epithelial cells form a tight barrier to act as selective physical barriers, repelling hostile substances. Tumor necrosis factor-α (TNF-α) is a well characterized pro-inflammatory cytokine which can compromise intestinal barrier function and the suppression of TNF-α function is important for treatment of inflammatory bowel disease (IBD). In this study, we investigated the contribution of G-protein-coupled receptor (GPCR)-induced signalling pathways to the maintenance of epithelial barrier function. We first demonstrated the existence of functional muscarinic M3 and histamine H1 receptors in colonic epithelial cell HT-29/B6. As we previously reported, muscarinic M3 receptor prevented TNF-α-induced barrier disruption through acceleration of TNF receptor (TNFR) shedding which is carried out by TNF-α converting enzyme (TACE). M3 receptor-mediated suppression of TNF-α function depends on Gα_q/11 protein, however, histamine H1 receptor could not ameliorate TNF-α function, while which could induce Gα_q/11 dependent intracellular Ca²⁺ mobilization. We found that p38 MAPK was predominantly phosphorylated by M3 receptor through Gα_q/11 protein, whereas H1 receptor barely upregulated the phosphorylation. Inhibition of p38 MAPK abolished M3 receptor-mediated TNFR shedding and suppression of TNF-α-induced NF-κB signalling. The p38 MAPK was also involved in TACE- mediated EGFR transactivation followed by ERK1/2 phosphorylation. These results indicate that not H1 but M3 receptor-induced activation of p38 MAPK might contribute to the maintenance of epithelial barrier function through down-regulation of TNF-α signalling and activation of EGFR.

Potential of GPCRs to modulate MAPK and mTOR pathways in Alzheimer's disease

Despite efforts to understand the mechanism of neuronal cell death, finding effective therapies for neurodegenerative diseases is still a challenge. Cognitive deficits are often associated with neurodegenerative diseases. Remarkably, in the absence of consensus biomarkers, diagnosis of diseases such as Alzheimer's still relies on cognitive tests. Unfortunately, all efforts to translate findings in animal models to the patients have been unsuccessful. Alzheimer's disease may be addressed from two different points of view, neuroprotection or cognitive enhancement. Based on recent data, the mammalian target of rapamycin (mTOR) pathway arises as a versatile player whose modulation may impact on mechanisms of both neuroprotection and cognition. Whereas direct targeting of mTOR does not seem to constitute a convenient approach in drug discovery, its indirect modulation by other signaling pathways seems promising. In fact, G-protein-coupled receptors (GPCRs) remain the most common 'druggable' targets and as such pharmacological manipulation of GPCRs with selective ligands may modulate phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), mitogen-activated protein (MAP) kinase and mTOR signaling pathways. Thus, GPCRs become important targets for potential drug treatments in different neurodegenerative disorders including, but not limited to, Alzheimer's disease. GPCR-mediated modulation of mTOR may take advantage of different GPCRs coupled to different G-dependent and G-independent signal transduction routes, of functional selectivity and/or of biased agonism. Signals mediated by GPCRs may act as coincidence detectors to achieve different benefits in different stages of the neurodegenerative disease.

ErbB Receptors and Cancer

The ErbB receptor family, also known as the EGF receptor family or type I receptor family, includes the epidermal growth factor (EGF) receptor (EGFR) or ErbB1/Her1, ErbB2/Her2, ErbB3/Her3, and ErbB4/Her4. Among all RTKs, EGFR was the first RTK identified and the first one linked to cancer. Thus, EGFR has also been the most intensively studied among all RTKs. ErbB receptors are activated after homodimerization or heterodimerization. The ErbB family is unique among the various groups of receptor tyrosine kinases (RTKs) in that ErbB3 has impaired kinase activity, while ErbB2 does not have a direct ligand. Therefore, heterodimerization is an important mechanism that allows the activation of all ErbB receptors in response to ligand stimulation. The activated ErbB receptors bind to many signaling proteins and stimulate the activation of many signaling pathways. The specificity and potency of intracellular signaling pathways are determined by positive and negative regulators, the specific composition of activating ligand(s), receptor dimer components, and the diverse range of proteins that associate with the tyrosine phosphorylated C-terminal domain of the ErbB receptors. ErbB receptors are overexpressed or mutated in many cancers, especially in breast cancer, ovarian cancer, and non-small cell lung cancer. The overexpression and overactivation of ErbB receptors are correlated with poor prognosis, drug resistance, cancer metastasis, and lower survival rate. ErbB receptors, especially EGFR and ErbB2 have been the primary choices as targets for developing cancer therapies.

Growth hormone-releasing hormone induced transactivation of epidermal growth factor receptor in human triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is a subset of breast cancers which is negative for expression of estrogen and progesterone receptors and human epidermal growth factor receptor-2 (HER2). Chemotherapy is currently the only form of treatment for women with TNBC. Growth hormone-releasing hormone (GHRH) and epidermal growth factor (EGF) are autocrine/paracrine growth factors in breast cancer and a substantial proportion of TNBC expresses receptors for GHRH and EGF. The aim of this study was to evaluate the interrelationship between both these signaling pathways in MDA-MB-468 human TNBC cells. We evaluated by Western blot assays the effect of GHRH on transactivation of EGF receptor (EGFR) as well as the elements implicated. We assessed the effect of GHRH on migration capability of MDA-MB-468 cells as well as the involvement of EGFR in this process by means of wound-healing assays. Our findings demonstrate that in MDA-MB-468 cells the stimulatory activity of GHRH on tyrosine phosphorylation of EGFR is exerted by two different molecular mechanisms: i) through GHRH receptors, GHRH stimulates a ligand-independent activation of EGFR involving at least cAMP/PKA and Src family signaling pathways; ii) GHRH also stimulates a ligand-dependent activation of EGFR implicating an extracellular pathway with an important role for metalloproteinases. The cross-talk between EGFR and GHRHR may be impeded by combining drugs acting upon GHRH receptors and EGFR family members. This combination of GHRH receptors antagonists with inhibitors of EGFR signalling could enhance the efficacy of both types of agents as well as reduce their doses increasing therapeutic benefits in management of human breast cancer.

Descending necrotizing mediastinitis in the elderly patients

Descending Necrotizing Mediastinitis (DNM) is a polymicrobic, dangerous and often fatal process, arising from head or neck infections and spreading along the deep fascial cervical planes, descending into the mediastinum. It can rapidly progress to sepsis and can frequently lead to death. It has a high mortality rate, up to 40% in the different series, as described in the literature. Surgical and therapeutic management has been discussed for long time especially in an elderly patient population. The literature has been reviewed in order to evaluate different pathogenesis and evolution and to recognise a correct therapeutic management.

Preoperative high-intensity training in frail old patients undergoing pulmonary resection for NSCLC

Thoracic surgery remains the better therapeutic option for non-small cell lung cancer patients that are diagnosed in early stage disease. Preoperative lung function assessment includes respiratory function tests (RFT) and cardio-pulmonary exercise testing (CPET). Vo2 peak, FEV1 and DLCO as well as recognition of performance status, presence of co-morbidities, frailty indexes, and age predict the potential impact of surgical resection on patient health status and survival risk. In this study we have retrospectively assessed the benefit of a high-intensity preoperative pulmonary rehabilitation program (PRP) in 14 patients with underlying lung function impairment prior to surgery. Amongst these, three patients candidate to surgical resection exhibited severe functional impairment associated with high score of frailty according CHS and SOF index, resulting in a substantial mortality risk. Our observations indicate that PRP appear to reduce the mortality and morbidity risk in frail patients with concurrent lung function impairment undergoing thoracic surgery. PRP produced improvement of VO2 peak degree and pulmonary function resulting in reduced postoperative complications in high-risk patients from our cases. Our results indicate that a preoperative training program may improve postoperative clinical outcomes in fraillung cancer patients with impaired lung function prior to surgical resection.

Positive and Negative Cross-Talk between Lysophosphatidic Acid Receptor 1, Free Fatty Acid Receptor 4, and Epidermal Growth Factor Receptor in Human Prostate Cancer Cells

Lysophosphatidic acid (LPA) is a lipid mediator that mediates cellular effects via G protein-coupled receptors (GPCRs). Epidermal growth factor (EGF) is a peptide that acts via a receptor tyrosine kinase. LPA and EGF both induce proliferation of prostate cancer cells and can transactivate each other's receptors. The LPA receptor LPA1 is particularly important for LPA response in human prostate cancer cells. Previous work in our laboratory has demonstrated that free fatty acid 4 (FFA4), a GPCR activated by ω-3 fatty acids, inhibits responses to both LPA and EGF in these cells. One potential mechanism for the inhibition involves negative interactions between FFA4 and LPA1, thereby suppressing responses to EGF that require LPA1 In the current study, we examined the role of LPA1 in mediating EGF and FFA4 agonist responses in two human prostate cancer cell lines, DU145 and PC-3. The results show that an LPA1-selective antagonist inhibits proliferation and migration to both LPA and EGF. Knockdown of LPA1 expression, using silencing RNA, blocks responses to LPA and significantly inhibits responses to EGF. The partial response to EGF that is observed after LPA1 knockdown is not inhibited by FFA4 agonists. Finally, the role of arrestin-3, a GPCR-binding protein that mediates many actions of activated GPCRs, was tested. Knockdown of arrestin-3 completely inhibits responses to both LPA and EGF in prostate cancer cells. Taken together, these results suggest that LPA1 plays a critical role in EGF responses and that FFA4 agonists inhibit proliferation by suppressing positive cross-talk between LPA1 and the EGF receptor.

Protease-activated receptor-1 deficiency protects against streptozotocin-induced diabetic nephropathy in mice

Endogenously administered activated protein C ameliorates diabetic nephropathy (DN) in a protease-activated receptor-1 (PAR-1)-dependent manner, suggesting that PAR-1 activation limits the progression of DN. Activation of PAR-1 in fibroblast-like cells, however, induces proliferation and extracellular matrix production, thereby driving fibrotic disease. Considering the key role of mesangial proliferation and extracellular matrix production during DN, PAR-1 may in fact potentiate diabetes-induced kidney injury. To determine the net effect of PAR-1 in DN, streptozotocin-induced DN was studied in wild type and PAR-1 deficient mice. Subsequent mechanistic insight was obtained by assessing profibrotic responses of mesangial and tubular epithelial cells in vitro, following PAR-1 stimulation and inhibition. Despite having similar glucose levels, PAR-1 deficient mice developed less kidney damage after induction of diabetes, as evidenced by diminished proteinuria, plasma cystatin C levels, expansion of the mesangial area, and tubular atrophy. In vitro, PAR-1 signaling in mesangial cells led to increased proliferation and expression of matrix proteins fibronectin and collagen IV. Conversely, a reduction in both proliferation and fibronectin deposition was observed in diabetic PAR-1 deficient mice. Overall, we show that PAR-1 plays an important role in the development of DN and PAR-1 might therefore be an attractive therapeutic target to pursue in DN.

The transition from a rural to an urban environment in Africa alters G protein-coupled receptor signaling

Urbanization in Africa is associated with an increased incidence of non-communicable diseases, yet the cause and the mechanism remain poorly understood. Here, we propose a role for G protein-coupled receptor (GPCR) signaling in the biological changes that occur with urbanization and suggest a critical area of convergence in GPCR signaling might provide a molecular signature for exposure to environmental factors. As a first step in investing this hypothesis, we examined the expression of the G protein α, β and γ subunit, G protein related kinase, and β-arrestin genes in a rural and urban population living in Morocco (NCBI GSE8847). Three genes associated with the phosphatidylinositol signaling pathway (GNAQ, GNA11 and GNA15), and one gene controlling the cyclic adenosine monophosphate pathway (GNAI2) was altered by urbanization. Of note, the expression of ARRB1 gene, which encodes the β-arrestin 1 protein and dampens the cellular responses to extracellular signals, was greater in the rural compared to the urban population (P<0.00002). These preliminary findings support our hypothesis that urbanization fundamentally alters GPCR signaling, resulting in both a qualitative and quantitative change in the signaling process. Because GPCR signaling is involved in a broad spectrum of cellular functions, further research is needed confirm these preliminary findings and to investigate what role GPCRs might have in the biological changes that occur with urbanization.

Integrated therapeutic approach to giant solitary fibrous tumor of the pleura: report of a case and review of the literature

The fibrous tumors of the pleura are rare primary tumors, accounting for 5% of malignant pleural neoplasms, which generally originate from sub-mesothelial mesenchymal tissue of the visceral pleura. These tumours generally exhibit clinical benign behavior although 12% of solitary fibrous tumors can be malignant and have worse outcomes. These tumors are considered “giant” when the lesion > 15 cm. Surgical treatment is the best choice for both benign and malignant neoplasms. We retrospectively analyzed the main case series of giant fibrous tumors of the pleura. In addition we report our experience of a 76-year-old woman treated by pre-surgical embolization involving implantation of vascular plugs. Surgery was successfully carried out without complications; imaging and functional assessment 6 months post intervention demonstrated both the absence of recurrence and improvement of lung function parameters.

Hypoxia induced CCL28 promotes angiogenesis in lung adenocarcinoma by targeting CCR3 on endothelial cells

Tumor hypoxia is one of the important features of lung adenocarcinoma. Chemokines might mediate the effects caused by tumor hypoxia. As confirmed in tumor tissue and serum of patients, CC chemokine 28 (CCL28) was the only hypoxia induced chemokine in lung adenocarcinoma cells. CCL28 could promote tube formation, migration and proliferation of endothelial cells. In addition, angiogenesis was promoted by CCL28 in the chick chorioallantoic membrane and matrigel implanted in dorsal back of athymic nude mice (CByJ.Cg-Foxn1^nu/J). Tumors formed by lung adenocarcinoma cells with high expression of CCL28 grew faster and had a higher vascular density, whereas tumor formation rate of lung adenocarcinoma cells with CCL28 expression knockdown was quite low and had a lower vascular density. CCR3, receptor of CCL28, was highly expressed in vascular endothelial cells in lung adenocarcinoma when examining by immunohistochemistry. Further signaling pathways in endothelial cells, modulated by CCL28, were analyzed by Phosphorylation Antibody Array. CCL28/CCR3 signaling pathway could bypass that of VEGF/VEGFR on the levels of PI3K-Akt, p38 MAPK and PLC gamma. The effects could be neutralized by antibody against CCR3. In conclusion, CCL28, as a chemokine induced by tumor hypoxia, could promote angiogenesis in lung adenocarcinoma through targeting CCR3 on microvascular endothelial cells.

Spirometry in elderly laryngectomized patients: A feasibility study

BACKGROUND

Laryngeal cancer is the second most common respiratory neoplasm after lung cancer. Laryngectomy is a well established treatment for larynx cancers which involve relevant anatomic alterations. Spirometry is an essential investigation tool for diagnosis and severity of respiratory diseases, difficult to perform in laryngectomees.

METHODS

43 consecutive laryngectomized patients were enrolled from July 2014 to March 2015. Patients fulfilling inclusion criteria underwent spirometry at baseline assessment and after two days. During the examination, the spirometer was placed directly on the stoma of the patient, through mouthpiece "Spirometry Filter 74".

RESULTS

At baseline, 26 eligible laryngectomees correctly performed the spirometry test with mouthpiece adhering to the stoma; 4 patients refused to perform the second spirometry after 2 days. The feasibility of spirometry examination in these patients was 100% despite difficulties in the execution of the test. The Pearson coefficient of reproducibility for FEV1, FVC and Tiffeneau Index was, respectively, 0.98, 0.94 and 0.77.

DISCUSSION

Spirometry in laryngectomee patients is a feasible procedure for assessment of respiratory function; despite technical difficulties in the execution of the test, our results underline the reproducibility and repeatability of the spirometry. In conclusion, when performed within dedicated respiratory pathophysiology unit, spirometry is a reliable tool in the assessment and follow up of laryngectomees.

Nuclear localization of Formyl-Peptide Receptor 2 in human cancer cells

Current models of G protein-coupled receptors (GPCRs) signaling describe binding of external agonists to cell surface receptors which, in turn, trigger several biological responses. New paradigms indicate that GPCRs localize to and signal at the nucleus, thus regulating distinct signaling cascades. The formyl-peptide receptor FPR2 belongs to the GPCR super-family and is coupled to PTX-sensitive Gi proteins. We show by western blot analysis, immunofluorescence experiments and radioligand binding assays that FPR2 is expressed at nuclear level in CaLu-6 and AGS cells. Nuclear FPR2 is a functional receptor, since it participates in intra-nuclear signaling, as assessed by decreased G protein-FPR2 association and enhanced ERK2, c-Jun and c-Myc phosphorylation upon stimulation of intact nuclei with the FPR2 agonist, WKYMVm. We analyzed FPR2 sequence for the search of a nuclear localization sequence (NLS) and we found a stretch of basic aminoacids (227-KIHKK-231) in the third cytoplasmic loop of the receptor. We performed single (K230A) and multiple (H229A/K230A/K231A) mutagenesis of NLS. The constructs were individually overexpressed in HEK293 cells and immunofluorescence and western blot analysis showed that nuclear localization or translocation of FPR2 depends on the integrity of the H(229) and K(231) residues within the NLS.

Delineating biased ligand efficacy at 7TM receptors from an experimental perspective

During the last 10 years, the concept of "biased agonism" also called "functional selectivity" swamped the pharmacology of 7 transmembrane receptors and paved the way for developing signaling pathway-selective drugs with increased efficacy and less adverse effects. Initially thought to select the activation of only a subset of the signaling pathways by the reference agonist, bias ligands revealed higher complexity as they have been shown to stabilize variable receptor conformations that associate with distinct signaling events from the reference. Today, one major challenge relies on the in vitro determination of the bias and classification of these ligands, as a prerequisite for future in vivo and clinical translation. In this review, current experimental considerations for the bias evaluation related to choice of the cellular model, of the signaling pathway as well as of the assays are presented and discussed.

Pigment epithelium-derived factor regulation by human chorionic gonadotropin in granulosa cells

Human chorionic gonadotropin (hCG) is a known trigger of ovarian hyperstimulation syndrome (OHSS), a potentially life-threatening complication of assisted reproduction. Administration of hCG results in the release of vascular endothelial growth factor (VEGF) from the ovary. We have previously shown that expression of pigment epithelium-derived factor (PEDF) in granulosa cell line is regulated by hCG, reciprocally to VEGF, and that the PEDF–VEGF balance is impaired in OHSS. Our aim was to explore the signaling network by which hCG downregulates the expression of PEDF mRNA and protein in granulosa cells. We applied specific chemical inhibitors and stimuli to human primary granulosa cells and rat granulosa cell line. We found that PKA and protein kinase C, as well as EGFR, ERK1/2 and PI3K, participate in the signaling network. The finding that hCG-induced PEDF downregulation and VEGF upregulation are mediated by similar signaling cascades emphasizes the delicate regulation of ovarian angiogenesis.

Transactivation of Epidermal Growth Factor Receptor by G Protein-Coupled Receptors: Recent Progress, Challenges and Future Research

Both G protein-coupled receptors (GPCRs) and receptor-tyrosine kinases (RTKs) regulate large signaling networks, control multiple cell functions and are implicated in many diseases including various cancers. Both of them are also the top therapeutic targets for disease treatment. The discovery of the cross-talk between GPCRs and RTKs connects these two vast signaling networks and complicates the already complicated signaling networks that regulate cell signaling and function. In this review, we focus on the transactivation of epidermal growth factor receptor (EGFR), a subfamily of RTKs, by GPCRs. Since the first report of EGFR transactivation by GPCR, significant progress has been made including the elucidation of the mechanisms underlying the transactivation. Here, we first provide a basic picture for GPCR, EGFR and EGFR transactivation by GPCR. We then discuss the progress made in the last five years and finally provided our view of the future challenge and future researches needed to overcome these challenges.

A case of Multiple Unilateral Pulmonary arteriovenous Malformation Relapse: Efficacy of embolization treatment

Pulmonary arteriovenous Malformations (PAVMs) are a rare vascular alteration characterized by abnormal communications between the pulmonary arteries and veins resulting in an extracardiac right-to-left (R-L) shunt. The majority of PAVMs are associated with an autosomal dominant vascular disorder also known as Osler-Weber-Rendu Syndrome. PAVMs appearance can be both single and multiple. Clinical manifestations include hypoxemia, dyspnea cyanosis, hemoptysis and cerebrovascular ischemic events or abscesses. We report a case of an 18 year old female with severe respiratory failure caused by a relapse of multiple unilateral pulmonary arterovenous fistula. Symptoms at admission include dyspnea, cyanosis and clubbing. The patient underwent pulmonary angio-TC scan, brain CT and echocardiography. The thoracic angio-CT scan showed the presence of PAVMs of RUL and RLL; a marked increase of right bronchial artery caliber and its branches with an aneurismatic dilatation was also observed. The patient underwent percutaneous transcatheter embolization using Amplatzer Vascular Plug IV; a relevant clinical and functional improvement was subsequently recorded. Embolization is effective in the treatment of relapsing PAVMS.

Cross-talk between lysophosphatidic acid receptor 1 and tropomyosin receptor kinase A promotes lung epithelial cell migration

Lysophosphatidic acid (LPA) is a bioactive lysophospholipid, which plays a crucial role in the regulation of cell proliferation, migration, and differentiation. LPA exerts its biological effects mainly through binding to cell-surface LPA receptors (LPA1-6), which belong to the G protein-coupled receptor (GPCR) family. Recent studies suggest that cross-talk between receptor tyrosine kinases (RTKs) and GPCRs modulates GPCRs-mediated signaling. Tropomyosin receptor kinase A (TrkA) is a RTK, which mediates nerve growth factor (NGF)-induced biological functions including cell migration in neuronal and non-neuronal cells. Here, we show LPA1 transactivation of TrkA in murine lung epithelial cells (MLE12). LPA induced tyrosine phosphorylation of TrkA in both time- and dose-dependent manners. Down-regulation of LPA1 by siRNA transfection attenuated LPA-induced phosphorylation of TrkA, suggesting a cross-talk between LPA1 and TrkA. To investigate the molecular regulation of the cross-talk, we focused on the interaction between LPA1 and TrkA. We found that LPA induced interaction between LPA1 and TrkA. The LPA1/TrkA complex was localized on the plasma membrane and in the cytoplasm. The C-terminus of LPA1 was identified as the binding site for TrkA. Inhibition of TrkA attenuated LPA-induced phosphorylation of TrkA and LPA1 internalization, as well as lung epithelial cell migration. These studies provide a molecular mechanism for the transactivation of TrkA by LPA, and suggest that the cross-talk between LPA1 and TrkA regulates LPA-induced receptor internalization and lung epithelial cell migration.

Comparative analyses of downstream signal transduction targets modulated after activation of the AT1 receptor by two β-arrestin-biased agonists

G protein-coupled receptors (GPCRs) are involved in essentially all physiological processes in mammals. The classical GPCR signal transduction mechanism occurs by coupling to G protein, but it has recently been demonstrated that interaction with β-arrestins leads to activation of pathways that are independent of the G protein pathway. Also, it has been reported that some ligands can preferentially activate one of these signaling pathways; being therefore called biased agonists for G protein or β-arrestin pathways. The angiotensin II (AngII) AT1 receptor is a prototype GPCR in the study of biased agonism due to the existence of well-known β-arrestin-biased agonists, such as [Sar(1), Ile(4), Ile(8)]-AngII (SII), and [Sar(1), D-Ala(8)]-AngII (TRV027). The aim of this study was to comparatively analyze the two above mentioned β-arrestin-biased agonists on downstream phosphorylation events and gene expression profiles. Our data reveal that activation of AT1 receptor by each ligand led to a diversity of activation profiles that is far broader than that expected from a simple dichotomy between "G protein-dependent" and "β-arrestin-dependent" signaling. We observed clusters of activation profiles common to AngII, SII, and TRV027, as well as downstream effector activation that are unique to AngII, SII, or TRV027. Analyses of β-arrestin conformational changes after AT1 receptor stimulation with SII or TRV027 suggests that the observed differences could account, at least partially, for the diversity of modulated targets observed. Our data reveal that, although the categorization "G protein-dependent" vs. "β-arrestin-dependent" signaling can be of pharmacological relevance, broader analyses of signaling pathways and downstream targets are necessary to generate an accurate activation profile for a given ligand. This may bring relevant information for drug development, as it may allow more refined comparison of drugs with similar mechanism of action and effects, but with distinct side effects.

Loss of the insulin receptor in murine megakaryocytes/platelets causes thrombocytosis and alterations in IGF signalling

Aims

Patients with conditions that are associated with insulin resistance such as obesity, type 2 diabetes mellitus, and polycystic ovary syndrome have an increased risk of thrombosis and a concurrent hyperactive platelet phenotype. Our aim was to determine whether insulin resistance of megakaryocytes/platelets promotes platelet hyperactivation.

Methods and results

We generated a conditional mouse model where the insulin receptor (IR) was specifically knocked out in megakaryocytes/platelets and performed ex vivo platelet activation studies in wild-type (WT) and IR-deficient platelets by measuring aggregation, integrin α_IIbβ₃ activation, and dense and α-granule secretion. Deletion of IR resulted in an increase in platelet count and volume, and blocked the action of insulin on platelet signalling and function. Platelet aggregation, granule secretion, and integrin α_IIbβ₃ activation in response to the glycoprotein VI (GPVI) agonist collagen-related peptide (CRP) were significantly reduced in platelets lacking IR. This was accompanied by a reduction in the phosphorylation of effectors downstream of GPVI. Interestingly, loss of IR also resulted in a reduction in insulin-like growth factor-1 (IGF-1)- and insulin-like growth factor-2 (IGF-2)-mediated phosphorylation of IRS-1, Akt, and GSK3β and priming of CRP-mediated platelet activation. Pharmacological inhibition of IR and the IGF-1 receptor in WT platelets recapitulated the platelet phenotype of IR-deficient platelets.

Conclusions

Deletion of IR (i) increases platelet count and volume, (ii) does not cause platelet hyperactivity, and (iii) reduces GPVI-mediated platelet function and platelet priming by IGF-1 and IGF-2.

Novel Molecular Approaches in Heart Failure: Seven Trans-Membrane Receptors Signaling in the Heart and Circulating Blood Leukocytes

Heart failure (HF) is the result of molecular, cellular, and structural changes induced by cardiac load or injury. A complex network of signaling pathways have been involved in the development and progression of cardiac dysfunction. In this review, we summarize the pivotal role of seven trans-membrane receptors (7TMRs), also called G-protein-coupled receptors (GPCRs), in HF. Moreover, we will discuss the current knowledge on the potential mirroring of 7TMR signaling between circulating blood leukocytes and the heart, and the related future possibilities in the management of HF patients.