Transmembrane Guanylyl Cyclase Research Articles

The role of cGMP signalling in auditory processing in health and disease.

cGMP is generated by the cGMP-forming guanylyl cyclases (GCs), the intracellular nitric oxide (NO)-sensitive (soluble) guanylyl cyclase (sGC) and transmembrane GC (e.g. GC-A and GC-B). In summarizing the particular role of cGMP signalling for hearing, we show that GC generally do not interfere significantly with basic hearing function but rather sustain a healthy state for proper temporal coding, fast discrimination and adjustments during injury. sGC is critical for the integrity of the first synapse in the ascending auditory pathway, the inner hair cell synapse. GC-A promotes hair cell stability under stressful conditions such as acoustic trauma or ageing. GC-B plays a role in the development of efferent feed-back and gain control. Regarding the crucial role hearing has for language development, speech discrimination and cognitive brain functions, differential pharmaceutical targeting of GCs offers therapeutic promise for the restoration of hearing. LINKED ARTICLES: This article is part of a themed issue on cGMP Signalling in Cell Growth and Survival. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.11/issuetoc.

Targets of cGMP/cGKI in Cardiac Myocytes.

The 3',5'-cyclic guanosine monophosphate (cGMP)-dependent protein kinase type I (cGKI aka PKGI) is a major cardiac effector acting downstream of nitric oxide (NO)-sensitive soluble guanylyl cyclase and natriuretic peptides (NPs), which signal through transmembrane guanylyl cyclases. Consistent with the wide distribution of the cGMP-generating guanylyl cyclases, cGKI, which usually elicits its cellular effects by direct phosphorylation of its targets, is present in multiple cardiac cell types including cardiomyocytes (CMs). Although numerous targets of cGMP/cGKI in heart were identified in the past, neither their exact patho-/physiological functions nor cell-type specific roles are clear. Herein, we inform about the current knowledge on the signal transduction downstream of CM cGKI. We believe that better insights into the specific actions of cGMP and cGKI in these cells will help to guide future studies in the search for predictive biomarkers for the response to pharmacological cGMP pathway modulation. In addition, targets downstream of cGMP/cGKI may be exploited for refined and optimized diagnostic and therapeutic strategies in different types of heart disease and their causes. Importantly, key functions of these proteins and particularly sites of regulatory phosphorylation by cGKI should, at least in principle, remain intact, although upstream signaling through the second messenger cGMP is impaired or dysregulated in a stressed or diseased heart state.

Regulation of the Natriuretic Peptide Receptor 2 (Npr2) by Phosphorylation of Juxtamembrane Serine and Threonine Residues Is Essential for Bifurcation of Sensory Axons.

cGMP signaling elicited by activation of the transmembrane receptor guanylyl cyclase Npr2 (also known as guanylyl cyclase B) by the ligand CNP controls sensory axon bifurcation of DRG and cranial sensory ganglion (CSG) neurons entering the spinal cord or hindbrain, respectively. Previous studies have shown that Npr2 is phosphorylated on serine and threonine residues in its kinase homology domain (KHD). However, it is unknown whether phosphorylation of Npr2 is essential for axon bifurcation. Here, we generated a knock-in mouse line in which the seven regulatory serine and threonine residues in the KHD of Npr2 were substituted by alanine (Npr2-7A), resulting in a nonphosphorylatable enzyme. Real-time imaging of cGMP in DRG neurons with a genetically encoded fluorescent cGMP sensor or biochemical analysis of guanylyl cyclase activity in brain or lung tissue revealed the absence of CNP-induced cGMP generation in the Npr27A/7A mutant. Consequently, bifurcation of axons, but not collateral formation, from DRG or CSG in this mouse mutant was perturbed at embryonic and mature stages. In contrast, axon branching was normal in a mouse mutant in which constitutive phosphorylation of Npr2 is mimicked by a replacement of all of the seven serine and threonine sites by glutamic acid (Npr2-7E). Furthermore, we demonstrate that the Npr27A/7A mutation causes dwarfism as described for global Npr2 mutants. In conclusion, our in vivo studies provide strong evidence that phosphorylation of the seven serine and threonine residues in the KHD of Npr2 is an important regulatory element of Npr2-mediated cGMP signaling which affects physiological processes, such as axon bifurcation and bone growth.SIGNIFICANCE STATEMENT The branching of axons is a morphological hallmark of virtually all neurons. It allows an individual neuron to innervate different targets and to communicate with neurons located in different regions of the nervous system. The natriuretic peptide receptor 2 (Npr2), a transmembrane guanylyl cyclase, is essential for the initiation of bifurcation of sensory axons when entering the spinal cord or the hindbrain. By using two genetically engineered mouse lines, we show that phosphorylation of specific serine and threonine residues in juxtamembrane regions of Npr2 are required for its enzymatic activity and for axon bifurcation. These investigations might help to understand the regulation of Npr2 and its integration in intracellular signaling systems.

Guanylyl cyclase‐G is an alarm pheromone receptor in mice

Many animals respond to threats by releasing alarm pheromones (APs) that warn conspecifics. In mice, detection of the AP 2-sec-butyl-4,5-dihydrothiazole (SBT) is mediated by chemosensory neurons residing in the Grueneberg ganglion (GG) of the anterior nasal region. Although the molecular mechanisms underlying activation of GG neurons by SBT and other substances are still unclear, recent studies have reported an involvement of the transmembrane guanylyl cyclase (GC) subtype GC-G in chemosensory signaling in the GG Here, we show that SBT directly binds with high affinity to the extracellular domain of GC-G and elicits an enhanced enzymatic activity of this protein. In line with this finding, heterologous expression of GC-G renders cells responsive to SBT while activation by SBT was strongly attenuated in GG neurons from GC-G-deficient mice. Consistently, SBT-induced fear-associated behaviors, SBT-evoked elevated blood pressure, and increased serum levels of the stress hormone corticosterone were clearly reduced in GC-G-knockout animals compared to wild-type mice. These observations suggest that GC-G serves as an unusual receptor in GG neurons mediating the detection of the volatile AP substance SBT.

Molecular Physiology of Membrane Guanylyl Cyclase Receptors.

cGMP controls many cellular functions ranging from growth, viability, and differentiation to contractility, secretion, and ion transport. The mammalian genome encodes seven transmembrane guanylyl cyclases (GCs), GC-A to GC-G, which mainly modulate submembrane cGMP microdomains. These GCs share a unique topology comprising an extracellular domain, a short transmembrane region, and an intracellular COOH-terminal catalytic (cGMP synthesizing) region. GC-A mediates the endocrine effects of atrial and B-type natriuretic peptides regulating arterial blood pressure/volume and energy balance. GC-B is activated by C-type natriuretic peptide, stimulating endochondral ossification in autocrine way. GC-C mediates the paracrine effects of guanylins on intestinal ion transport and epithelial turnover. GC-E and GC-F are expressed in photoreceptor cells of the retina, and their activation by intracellular Ca(2+)-regulated proteins is essential for vision. Finally, in the rodent system two olfactorial GCs, GC-D and GC-G, are activated by low concentrations of CO2and by peptidergic (guanylins) and nonpeptidergic odorants as well as by coolness, which has implications for social behaviors. In the past years advances in human and mouse genetics as well as the development of sensitive biosensors monitoring the spatiotemporal dynamics of cGMP in living cells have provided novel relevant information about this receptor family. This increased our understanding of the mechanisms of signal transduction, regulation, and (dys)function of the membrane GCs, clarified their relevance for genetic and acquired diseases and, importantly, has revealed novel targets for therapies. The present review aims to illustrate these different features of membrane GCs and the main open questions in this field.

C-type natriuretic peptide ameliorates pulmonary fibrosis by acting on lung fibroblasts in mice.

BackgroundPulmonary fibrosis has high rates of mortality and morbidity; however, no effective pharmacological therapy has been established. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, selectively binds to the transmembrane guanylyl cyclase (GC)-B receptor and exerts anti-inflammatory and anti-fibrotic effects in various organs through vascular endothelial cells and fibroblasts that have a cell-surface GC-B receptor. Given the pathophysiological importance of fibroblast activation in pulmonary fibrosis, we hypothesized that the anti-fibrotic and anti-inflammatory effects of exogenous CNP against bleomycin (BLM)-induced pulmonary fibrosis were exerted in part by the effect of CNP on pulmonary fibroblasts.MethodsC57BL/6 mice were divided into two groups, CNP-treated (2.5 μg/kg/min) and vehicle, to evaluate BLM-induced (1 mg/kg) pulmonary fibrosis and inflammation. A periostin-CNP transgenic mouse model exhibiting CNP overexpression in fibroblasts was generated and examined for the anti-inflammatory and anti-fibrotic effects of CNP via fibroblasts in vivo. Additionally, we assessed CNP attenuation of TGF-β-induced differentiation into myofibroblasts by using immortalized human lung fibroblasts stably expressing GC-B receptors. Furthermore, to investigate whether CNP acts on human lung fibroblasts in a clinical setting, we obtained primary-cultured fibroblasts from surgically resected lungs of patients with lung cancer and analyzed levels of GC-B mRNA transcription.ResultsCNP reduced mRNA levels of the profibrotic cytokines interleukin (IL)-1β and IL-6, as well as collagen deposition and the fibrotic area in lungs of mice with bleomycin-induced pulmonary fibrosis. Furthermore, similar CNP effects were observed in transgenic mice exhibiting fibroblast-specific CNP overexpression. In cultured-lung fibroblasts, CNP treatment attenuated TGF-β–induced phosphorylation of Smad2 and increased mRNA and protein expression of α-smooth muscle actin and SM22α, indicating that CNP suppresses fibroblast differentiation into myofibroblasts. Furthermore, human lung fibroblasts from patients with or without interstitial lung disease substantially expressed GC-B receptor mRNA.ConclusionsThese data suggest that CNP ameliorates bleomycin-induced pulmonary fibrosis by suppressing TGF-β signaling and myofibroblastic differentiation in lung fibroblasts. Therefore, we propose consideration of CNP for clinical application to pulmonary fibrosis treatment.

Abstract 16716: Intravascular Injection of Sendai Virus Vector Carrying Continuously cGMP Producing Mutant of Type B Natriuretic Peptide Receptor Can Ameliorate Pulmonary Arterial Hypertension

Introduction: Type B natriuretic peptide receptor (NPR-B) is one of the transmembrane guanylyl cyclases and synthesizes cGMP on C-type natriuretic peptide binding. We have found a novel constitutively active mutation in the NPR-B gene in a family case showing overgrowth and bone anomalies. Previously, we constructed adenovirus vectors carrying this mutant NPR-B and administered to Sugen PAH rats intratracheally to investigate its therapeutic effect. However, the use of adenovirus vectors actually caused inflammatory host response in the lung. Objective: Sendai virus vector (SeV) is well known for its high transduction efficiency as well as the low toxicity. Recently, the results of a Phase I/IIa clinical study of SeV in human peripheral arterial disease have been reported. The objective of this study was to investigate the therapeutic effect of SeV carrying constitutively active mutant of NPR-B for PAH in rats. Methods and Results: We constructed SeV carrying wild-type (WT), and mutant (Mut) NPR-B. Control SeV carrying Azami-Green was purchased from MBL (Medical & Biological laboratories, Nagoya, Japan). The overexpression of the mutant in human pulmonary artery smooth muscle cells by SeV induced significant increase in cGMP levels (control, 0.193±0.115 pmol/mL; WT-NPR-B, 38.3±29.6 pmol/mL; Mut-NPR-B, 2460±577 pmol/mL; n=3; p<0.01), and suppressed proliferation as assessed by 5-ethynyl-2′-deoxyuridine (EdU) incorporation (EdU positive ratio: control, 0.18±0.017; WT, 0.12±0.023; Mut, 0.085±0.010; n=6; P < 0.05). In Sugen PAH rats, intravascular administration of SeV carrying Mut-NPR-B significantly decreased right ventricular systolic pressure (Control, 61.4±8.4 mmHg; WT, 61.5±5.4 mmHg; Mut, 46.9±4.9mmHg; n=6; p<0.01) and the ratio of right ventricular/left ventricular pressure (Control, 0.67±0.05; WT, 0.70±0.03; Mut, 0.53±0.09; n=6; p<0.01). Furthermore, the proportion of occluded arteries was lower in Mut transduced rats than in control or WT transduced rats histologically. Conclusions: The CNP/NPR-B signaling pathway is an additional therapeutic target for the treatment of PAH. The enhancement of CNP/NPR-B pathway could ameliorate both intimal and medial remodeling of pulmonary artery in PAH.

Dephosphorylation of juxtamembrane serines and threonines of the NPR2 guanylyl cyclase is required for rapid resumption of oocyte meiosis in response to luteinizing hormone

The meiotic cell cycle of mammalian oocytes starts during embryogenesis and then pauses until luteinizing hormone (LH) acts on the granulosa cells of the follicle surrounding the oocyte to restart the cell cycle. An essential event in this process is a decrease in cyclic GMP in the granulosa cells, and part of the cGMP decrease results from dephosphorylation and inactivation of the natriuretic peptide receptor 2 (NPR2) guanylyl cyclase, also known as guanylyl cyclase B. However, it is unknown whether NPR2 dephosphorylation is essential for LH-induced meiotic resumption. Here, we prevented NPR2 dephosphorylation by generating a mouse line in which the seven regulatory serines and threonines of NPR2 were changed to the phosphomimetic amino acid glutamate (Npr2–7E). Npr2–7E/7E follicles failed to show a decrease in enzyme activity in response to LH, and the cGMP decrease was attenuated; correspondingly, LH-induced meiotic resumption was delayed. Meiotic resumption in response to EGF receptor activation was likewise delayed, indicating that NPR2 dephosphorylation is a component of the pathway by which EGF receptor activation mediates LH signaling. We also found that most of the NPR2 protein in the follicle was present in the mural granulosa cells. These findings indicate that NPR2 dephosphorylation in the mural granulosa cells is essential for the normal progression of meiosis in response to LH and EGF receptor activation. In addition, these studies provide the first demonstration that a change in phosphorylation of a transmembrane guanylyl cyclase regulates a physiological process, a mechanism that may also control other developmental events.

Receptor guanylyl cyclase-G is a novel thermosensory protein activated by cool temperatures.

Transmembrane guanylyl cyclases (GCs), with activity regulated by peptide ligands and/or calcium-binding proteins, are essential for various physiological and sensory processes. The mode of activation of the GC subtype GC-G, which is expressed in neurons of the Grueneberg ganglion that respond to cool temperatures, has been elusive. In searching for appropriate stimuli to activate GC-G, we found that its enzymatic activity is directly stimulated by cool temperatures. In this context, it was observed that dimerization/oligomerization of GC-G, a process generally considered as critical for enzymatic activity of GCs, is strongly enhanced by coolness. Moreover, heterologous expression of GC-G in cultured cells rendered these cells responsive to coolness; thus, the protein might be a sensor for cool temperatures. This concept is supported by the observation of substantially reduced coolness-induced response of Grueneberg ganglion neurons and coolness-evoked ultrasonic vocalization in GC-G-deficient mouse pups. GC-G may be a novel thermosensory protein with functional implications for the Grueneberg ganglion, a sensory organ responding to cool temperatures.

The c-type natriuretic peptide and its transmembrane guanylyl cyclase receptor natriuretic peptide receptor b are not critical regulators of meiosis inhibition in rhesus macaques

C-type natriuretic peptide (CNP) and its transmembrane guanylyl cyclase receptor, natriuretic peptide receptor B (NPR2), have been established as critical regulators of cGMP induced meiosis arrest in mouse oocytes. CNP produced by mural granulosa cells binds NPR2 in cumulus cells to poroduce cGMP that diffuses into the oocyte to inhibit meiosis. As this pathway represents a potential target for contraceptive development, the study objective was to determine if this mechanism is also functional in primates.

Decision making in C. elegans chemotaxis to alkaline pH (612.1)

Monitoring of environmental and tissue pH is crucial for animal’s survival behavior. The nematode C. elegans is an excellent model organism for analysis of neural circuits that regulate animal behavior. The animal is attracted to mildly alkaline pH, but avoids strongly alkaline pH. Here we analyzed the chemotactic behavior at molecular and cellular levels. Genetic dissection and Ca2+ imaging demonstrated that ASEL and ASH are the major sensory neurons responsible for attraction to mildly alkaline pH and repulsion from strongly alkaline pH, respectively. In ASEL, A transmembrane guanylyl cyclase, GCY‐14, is activated by mildly alkaline pH, and in turn opens a cGMP‐gated cation channels consisting of TAX‐2 and TAX‐4. It has also been shown that a specific histidine residue plays an essential role in the extracellular alkaline pH. In ASH, TRPV channels consisting of OSM‐9 and OCR‐2 are activated by strongly alkaline pH for Ca2+ influx into the neuron. A G‐protein α subunit, GOA‐1, is also required for its avoidance behavior perhaps through regulating synaptic vesicle exocytosis in ASH. By analyzing chemotactic behavior of various mutants, we also found that activities of ASEL and ASH compete each other for decision making or behavior switching in C. elegans chemotaxis to alkaline pH. While mildly alkaline pH preferentially activates ASEL, strongly alkaline pH activates both ASEL and ASH, and ASH activity overrides the activity of ASEL. Neural circuits responsible for this decision making will be discussed.

Environmental Alkalinity Sensing Mediated by the Transmembrane Guanylyl Cyclase GCY-14 in C. elegans

Survival requires that living organisms continuously monitor environmental and tissue pH. Animals sense acidic pH using ion channels and G-protein-coupled receptors (GPCRs), but monitoring of alkaline pH is not well understood. We report here that in the nematode Caenorhabditis elegans, a transmembrane receptor-type guanylyl cyclase (RGC), GCY-14, of the ASEL gustatory neuron, plays an essential role in the sensing of extracellular alkalinity. Activation of GCY-14 opens a cGMP-gated cation channel encoded by tax-2 and tax-4, resulting in Ca(2+) entry into ASEL. Ectopic expression of GCY-14 in other neurons indicates that it accounts for the alkalinity sensing capability. Domain-swapping and site-directed mutagenesis of GCY-14 reveal that GCY-14 functions as a homodimer, in which histidine of the extracellular domains plays a crucial role in alkalinity detection. These results argue that in addition to ion channels and GPCRs, RGCs also play a role in pH sensation in neurons.

Odorant-evoked electrical responses in Grueneberg ganglion neurons rely on cGMP-associated signaling proteins

The Grueneberg ganglion (GG) in the anterior nasal region of mice is considered as an olfactory compartment since its neurons were recently observed to be activated by chemical stimuli, in particular by the odorant 2,3-dimethylpyrazine (2,3-DMP). However, it is unclear whether the GG indeed serves an olfactory function since these findings are solely based on the expression of the activity-dependent gene c-Fos. Consequently, it is yet uncertain whether chemical compounds, such as given odorants, elicit electrical responses in GG neurons which are required to convey the chemosensory information to the brain. Therefore, in the present study, electrical recording experiments on tissue sections through the anterior nasal region of mice were conducted which revealed that 2,3-DMP induces electrical signals in the GG. These responses were restricted to sites harboring GG neurons, indicating that 2,3-DMP elicits an electrical signal only in these but not in other cells of the anterior nasal region.2,3-DMP-sensitive GG neurons express signaling proteins associated with the second messenger substance cyclic guanosine monophosphate (cGMP); most notably the cyclic nucleotide-gated ion channel CNGA3 and the transmembrane guanylyl cyclase GC-G. Using mice deficient for CNGA3 or GC-G demonstrated that the 2,3-DMP-evoked electrical signals in the GG of these knockout mice were substantially lower than in the GG of wildtype conspecifics, indicating that cGMP signaling plays a crucial role for odorant-induced electrical responses in the GG.

Luteinizing hormone reduces the activity of the NPR2 guanylyl cyclase in mouse ovarian follicles, contributing to the cyclic GMP decrease that promotes resumption of meiosis in oocytes

In preovulatory ovarian follicles of mice, meiotic prophase arrest in the oocyte is maintained by cyclic GMP from the surrounding granulosa cells that diffuses into the oocyte through gap junctions. The cGMP is synthesized in the granulosa cells by the transmembrane guanylyl cyclase natriuretic peptide receptor 2 (NPR2) in response to the agonist C-type natriuretic peptide (CNP). In response to luteinizing hormone (LH), cGMP in the granulosa cells decreases, and as a consequence, oocyte cGMP decreases and meiosis resumes. Here we report that within 20min, LH treatment results in decreased guanylyl cyclase activity of NPR2, as determined in the presence of a maximally activating concentration of CNP. This occurs by a process that does not reduce the amount of NPR2 protein. We also show that by a slower process, first detected at 2h, LH decreases the amount of CNP available to bind to the receptor. Both of these LH actions contribute to decreasing cGMP in the follicle, thus signaling meiotic resumption in the oocyte.

A cardiac pathway of cyclic GMP-independent signaling of guanylyl cyclase A, the receptor for atrial natriuretic peptide

Cardiac atrial natriuretic peptide (ANP) regulates arterial blood pressure, moderates cardiomyocyte growth, and stimulates angiogenesis and metabolism. ANP binds to the transmembrane guanylyl cyclase (GC) receptor, GC-A, to exert its diverse functions. This process involves a cGMP-dependent signaling pathway preventing pathological [Ca(2+)](i) increases in myocytes. In chronic cardiac hypertrophy, however, ANP levels are markedly increased and GC-A/cGMP responses to ANP are blunted due to receptor desensitization. Here we show that, in this situation, ANP binding to GC-A stimulates a unique cGMP-independent signaling pathway in cardiac myocytes, resulting in pathologically elevated intracellular Ca(2+) levels. This pathway involves the activation of Ca(2+)-permeable transient receptor potential canonical 3/6 (TRPC3/C6) cation channels by GC-A, which forms a stable complex with TRPC3/C6 channels. Our results indicate that the resulting cation influx activates voltage-dependent L-type Ca(2+) channels and ultimately increases myocyte Ca(2)(+)(i) levels. These observations reveal a dual role of the ANP/GC-A-signaling pathway in the regulation of cardiac myocyte Ca(2+)(i) homeostasis. Under physiological conditions, activation of a cGMP-dependent pathway moderates the Ca(2+)(i)-enhancing action of hypertrophic factors such as angiotensin II. By contrast, a cGMP-independent pathway predominates under pathophysiological conditions when GC-A is desensitized by high ANP levels. The concomitant rise in [Ca(2+)](i) might increase the propensity to cardiac hypertrophy and arrhythmias.

The indolocarbazole, Gö6976, inhibits guanylyl cyclase‐A and ‐B

Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) decrease vascular volume and pressure by activating guanylyl cyclase-A (GC-A). C-type natriuretic peptide (CNP) activation of guanylyl cyclase-B (GC-B) stimulates long bone growth. This study investigated the effects of the indolocarbazole, Gö6976, on the guanylyl cyclase activity of GC-A and GC-B as a first step towards developing small molecule regulators of these enzymes. Whole cell cGMP concentrations or ³²P-cGMP accumulation in membrane preparations measured the effects of indolocarbazoles on the enzymatic activity GC-A and GC-B from transfected 293T or endogenously expressing 3T3-L1 cells. Gö6976 blocked cellular CNP-dependent cGMP elevations in 293T-GC-B cells. The t(½) for Gö6976 inhibition was 7 s and IC₅₀ was 380 nM. Gö6976 increased the EC₅₀ for CNP 4.5-fold, but increasing the CNP concentration did not overcome the inhibition. Half of the inhibition was lost 1 h after removal of Gö6976 from the medium. Cellular exposure to Gö6976 reduced basal and natriuretic peptide-dependent, but not detergent-dependent, GC-A and GC-B activity. Inhibition was also observed when Gö6976 was added directly to the cyclase assay. A constitutively phosphorylated form of GC-B was similarly inhibited. These data demonstrate that Gö6976 potently, rapidly and reversibly inhibited GC-A and GC-B via a process that did not require intact cells, known phosphorylation sites or inactivation of all catalytic sites. This is the first report of an intracellular inhibitor of a transmembrane guanylyl cyclase and the first report of a non-kinase target for Gö6976.

A novel pathway of cGMP

Background Cardiac atrial natriuretic peptide (ANP) regulates arterial blood pressure, moderates cardiomyocyte growth, and stimulates angiogenesis and metabolism. ANP binds to the transmembrane guanylyl cyclase (GC) receptor, GCA to exert its diverse functions. This involves a cGMPdependent signaling pathway preventing pathological [Ca]i raises in myocytes. In chronic cardiac hypertrophy, however, ANP levels are markedly increased and GC-A/cGMP responses to ANP are blunted due to receptor desensitization.

Natriuretic peptide metabolism, clearance and degradation

Atrial natriuretic peptide, B-type natriuretic peptide and C-type natriuretic peptide constitute a family of three structurally related, but genetically distinct, signaling molecules that regulate the cardiovascular, skeletal, nervous, reproductive and other systems by activating transmembrane guanylyl cyclases and elevating intracellular cGMP concentrations. This review broadly discusses the general characteristics of natriuretic peptides and their cognate signaling receptors, and then specifically discusses the tissue-specific metabolism of natriuretic peptides and their degradation by neprilysin, insulin-degrading enzyme, and natriuretic peptide receptor-C.

756 DIFFERENTIAL ANGIOGENIC GENE EXPRESSION IN DIABETIC ERECTILE TISSUE – RESULTS FROM A MICROARRAY ANALYSIS

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Basic Research1 Apr 2011756 DIFFERENTIAL ANGIOGENIC GENE EXPRESSION IN DIABETIC ERECTILE TISSUE – RESULTS FROM A MICROARRAY ANALYSIS Angela Castela, Raquel Soares, Rui Medeiros, Ricardo Ribeiro, Cátia Monteiro, Pedro Gomes, Pedro Vendeira, Ronald Virag, and Carla Costa Angela CastelaAngela Castela Porto, Portugal More articles by this author , Raquel SoaresRaquel Soares Porto, Portugal More articles by this author , Rui MedeirosRui Medeiros Porto, Portugal More articles by this author , Ricardo RibeiroRicardo Ribeiro Porto, Portugal More articles by this author , Cátia MonteiroCátia Monteiro Porto, Portugal More articles by this author , Pedro GomesPedro Gomes Porto, Portugal More articles by this author , Pedro VendeiraPedro Vendeira Porto, Portugal More articles by this author , Ronald ViragRonald Virag Paris, France More articles by this author , and Carla CostaCarla Costa Porto, Portugal More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.1781AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Diabetes induces metabolic derangements promoting endothelial malfunction and erectile dysfunction (ED). However, it remains unclear the angiogenic molecular mechanisms deregulated in diabetic corpus cavernosum (CC) contributing to vascular impairment. We investigated alterations in cavernosal angiogenic gene expression in a diabetes experimental model. METHODS The range of angiogenic molecular changes associated with ED in diabetes type 1, was assessed in CC of streptozotocin-induced Wistar rats (n=5/group), in early (2-week) and established (8-week) diabetes. Differentially expressed genes were identified using the Rat Angiogenesis OligoGEArray System (SuperArray, USA). Expression data was validated by quantitative real-time PCR and at protein level by immunohistochemistry and western blotting (WB). The most significant expression alterations were also evaluated in human non-diabetic and diabetic cavernosal samples by immunolabeling and quantified using ImageJ color deconvolution. RESULTS We demonstrated that in early diabetes there was no significant differential gene expression. However, in the 8-week diabetic group there was a downregulation in the expression of 10 genes, which were involved in the regulation of important mechanisms including, G-protein signalling, apoptosis, response to oxidative stress, cell proliferation/adhesion. The most differentially expressed genes were the insulin-like growth factor-1 (Igf-1, stimulator of cell proliferation and indirect angiogenesis promoter), and the natriuretic peptide receptor-1 (Npr-1, transmembrane guanylyl cyclase involved in the synthesis of cyclic guanosine monophosphate; cGMP). These results were confirmed by real-time PCR, immunostaining and WB. Corroborating the animal studies, we have also detected a reduction in both IGF-1 and NPR-1 protein expression in human diabetic erectile tissue, when compared to non-diabetic CC. CONCLUSIONS Microarray analysis provided evidence of several angiogenic molecules deregulated in cavernosal tissue in established diabetes. Amongst them, IGF-1 and NPR-1 differential expression were the most significant, and due to their relevant functions in penile vascular homeostasis and vasorelaxation activation, respectively, they might be a potential target for diabetic ED treatment. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e304 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Angela Castela Porto, Portugal More articles by this author Raquel Soares Porto, Portugal More articles by this author Rui Medeiros Porto, Portugal More articles by this author Ricardo Ribeiro Porto, Portugal More articles by this author Cátia Monteiro Porto, Portugal More articles by this author Pedro Gomes Porto, Portugal More articles by this author Pedro Vendeira Porto, Portugal More articles by this author Ronald Virag Paris, France More articles by this author Carla Costa Porto, Portugal More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Chemo- and Thermosensory Responsiveness of Grueneberg Ganglion Neurons Relies on Cyclic Guanosine Monophosphate Signaling Elements

Neurons of the Grueneberg ganglion (GG) in the anterior nasal region of mouse pups respond to cool temperatures and to a small set of odorants. While the thermosensory reactivity appears to be mediated by elements of a cyclic guanosine monophosphate (cGMP) cascade, the molecular mechanisms underlying the odor-induced responses are unclear. Since odor-responsive GG cells are endowed with elements of a cGMP pathway, specifically the transmembrane guanylyl cyclase subtype GC-G and the cyclic nucleotide-gated ion channel CNGA3, the possibility was explored whether these cGMP signaling elements may also be involved in chemosensory GG responses. Experiments with transgenic mice deficient for GC-G or CNGA3 revealed that GG responsiveness to given odorants was significantly diminished in these knockout animals. These findings suggest that a cGMP cascade may be important for both olfactory and thermosensory signaling in the GG. However, in contrast to the thermosensory reactivity, which did not decline over time, the chemosensory response underwent adaptation upon extended stimulation, suggesting that the two transduction processes only partially overlap.