Stimulation Of Adenylyl Cyclase Research Articles

Long-term upregulation of cortical glutamatergic AMPA receptors in a mouse model of chronic visceral pain.

BackgroundIrritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders and it causes long-lasting visceral pain and discomfort. AMPA receptor mediated long-term potentiation (LTP) has been shown to play a critical role in animal models of neuropathic and inflammatory pain. No report is available for central changes in the ACC of mice with chronic visceral pain.ResultsIn this study, we used integrative methods to investigate potential central plastic changes in the anterior cingulate cortex (ACC) of a visceral pain mouse model induced by intracolonic injection of zymosan. We found that visceral pain induced an increased expression of AMPA receptors (at the post synapses) in the ACC via an enhanced trafficking of the AMPA receptors to the membrane. Both GluA1 and GluA2/3 subunits were significantly increased. Supporting biochemical changes, excitatory synaptic transmission in the ACC were also significantly enhanced. Microinjection of AMPA receptor inhibitor IEM1460 into the ACC inhibited visceral and spontaneous pain behaviors. Furthermore, we found that the phosphorylation of GluA1 at the Ser845 site was increased, suggesting that GluA1 phosphorylation may contribute to AMPA receptor trafficking. Using genetically knockout mice lacking calcium-calmodulin stimulated adenylyl cyclase subtype 1 (AC1), we found that AMPA receptor phosphorylation and its membrane trafficking induced by zymosan injection were completely blocked.ConclusionsOur results provide direct evidence for cortical AMPA receptors to contribute to zymosan-induced visceral and spontaneous pain and inhibition of AC1 activity may help to reduce chronic visceral pain.

OX2 orexin/hypocretin receptor signal transduction in recombinant Chinese hamster ovary cells

There are two subtypes of orexin receptors, OX1 and OX2. Signalling pathways have been mapped in much higher detail for OX1 receptors than OX2 receptors. Almost all the detailed studies have been performed in Chinese hamster ovary cells, and we thus chose the same cell background for the studies on human OX2 receptors to allow comparison to human OX1 receptors. Adenylyl cyclase, phospholipase A2, C and D and diacylglycerol lipase activities were assessed by precursor radiolabelling and chromatographic separation (ion exchange, affinity or thin layer), calcium by a fluorescent method, and receptor binding with [125I]-orexin-A. Upon activation with orexin-A, OX2 receptors stimulated phospholipase A2, C and D, diacylglycerol lipase and calcium elevation, and both inhibited and stimulated adenylyl cyclase; i.e., the responses to OX2 activation by orexin-A were principally like those of OX1, in contrast to some previous suggestions. The responses occurred mostly in the same concentration range as those for OX1 activation and via the same signal cascades. However, some responses were weaker, suggesting a partially differential coupling to some cascades. In summary, OX2 receptor signalling is principally similar to OX1 receptor signalling suggesting also a physiologically similar coupling, though this needs to be verified in physiological contexts. Some (relatively weak) differences between the receptors may be investigated in further studies.

Abstract 11569: Activation of cAMP/CREB/PGC-1α Pathway Plays a Key Role for a Novel Adenosine-like Angiogenic Agent COA-Cl to Induce Production of Vascular Endothelial Growth Factor (VEGF) in Cultured Human Fibroblasts

COA-Cl is a recently developed pro-angiogenic agent (Figure) that promotes tube forming activity of human umbilical vein endothelial cells that are co-cultured with fibroblasts. Recently, a metabolic stress-related co-transcription factor termed PGC-1α was identified as a novel activator of VEGF gene, a key regulator of angiogenesis. In skeletal muscle, the cAMP/CREB signaling pathway plays a central role in inducing PGC-1α expression. We therefore hypothesized that COA-Cl induces PGC-1α to promote VEGF production by elevating cAMP and activating CREB in fibroblasts. COA-Cl (100 μM for 48 h) augmented VEGF secretion into culture medium of normal human dermal fibroblasts from below the level of detection to 54±4 pg/mL (ELISA, p<0.01 vs. basal). This enhancement of VEGF secretion was associated with up-regulation of mRNA encoding VEGF and PGC-1α (RT-PCR, 2.1±0.3 and 9.9±0.8 fold, p<0.05, respectively). Induction of PGC-1α expression by COA-Cl was attenuated by 49±4% (p<0.01 vs. COA-Cl alone) by H-89 (100 μM), an inhibitor of PKA. Conversely, forskolin (25 μM), a direct stimulator of adenylyl cyclase that increases cAMP, increased VEGF production (423±20 pg/mL, p<0.01 vs. basal) and expression of mRNA encoding both VEGF and PGC-1α. COA-Cl induced an increase in cAMP content (ELISA) and phosphorylation of CREB at Ser133 (immunoblot), a PKA site associated with an increased transcriptional activity of CREB, in a time- and dose-dependent manner (4.4±0.3 and 2.3±0.2 fold at 100 μM COA-Cl for 20 min, p<0.05, respectively). In COS-7 fibroblast-like cells, COA-Cl elevated luciferase activity of transfected reporter construct driven by CRE, which is regulated by cAMP/CREB (2.4±0.1 fold at 200 μM COA-Cl for 24 h). Collectively, our results demonstrate that COA-Cl elevates cAMP and activates CREB in human fibroblasts to induce PGC-1α expression, thereby promoting VEGF transcription and secretion, potentially identifying a novel way to induce therapeutic angiogenesis.

The physiological role of glucagon-like peptide-1 in the regulation of renal function.

Glucagon like peptide-1 (GLP-1) is an incretin hormone constantly secreted from the intestine at low basal levels in the fasted state; plasma concentrations rise rapidly after nutrient ingestion. Upon release, GLP-1 exerts insulinotropic effects via a G protein-coupled receptor, stimulation of adenylyl cyclase, and cAMP generation. Although primarily involved in glucose homeostasis, GLP-1 can induce diuresis and natriuresis when administered in pharmacological doses in humans and rodents. However, whether endogenous GLP-1 plays a role in regulating renal function remains an open question. This study aimed to test the hypothesis that blockade of GLP-1 receptor (GLP-1R) signaling at baseline influences renal salt and water handling. To this end, the GLP-1R antagonist exendin-9 (100 μg·kg(-1)·min(-1)) or vehicle was administered intravenously to overnight-fasted male Wistar rats for 30 min. This treatment reduced urinary cAMP excretion and renal cortical PKA activity, demonstrating blockade of renal GLP-1R signaling. Exendin-9-infused-rats exhibited reduced glomerular filtration rate, lithium clearance, urinary volume flow, and sodium excretion compared with vehicle-infused controls. Exendin-9 infusion also reduced renal cortical Na(+)/H(+) exchanger isotope 3 (NHE3) phosphorylation at serine 552 (NHE3pS552), a PKA consensus site that correlates with reduced transport activity. Collectively, these results provide novel evidence that GLP-1 is a physiologically relevant natriuretic factor that contributes to sodium balance, in part via tonic modulation of NHE3 activity in the proximal tubule.

Modulation of cGMP/cAMP crosstalk on the level of PDE3 in animals lacking NO-sensitive guanylyl cyclase

NO-sensitive guanylyl cyclase (NO-GC) is accepted to be the major receptor for the signaling molecule NO. Deletion of NO-GC in mice leads to disturbed NO/cGMP signaling. As a result, these mice show abolished NO-dependent relaxation of smooth muscle-containing tissues in the cardiovascular and gastrointestinal systems. Mice with general deletion (GCKO) suffer from increased blood pressure, reduced bleeding time, erectile dysfunction and die prematurely due to gastrointestinal dysmotility. Mice lacking NO-GC specifically in smooth muscle cells (SMC) show an elevated blood pressure similar to that seen in GCKO animals. Crosstalk between cGMP and cAMP signaling has been reported to occur in many different cells. Phosphodiesterase 3 (PDE3) is thought to be one of the prominent mediators of this crosstalk. Through its inhibitory action on PDE3, cGMP may regulate cAMP levels and cAMP-mediated signaling. Here, we reasoned that, in animals deficient in NO-GC, lack of NO-induced cGMP synthesis might affect cGMP/cAMP crosstalk on the level of PDE3. Smooth muscle relaxation induced by forskolin to stimulate adenylyl cyclase was similar in WT, GCKO and SMC-GCKO aortae. RIA-based detection of basal cAMP levels in aortic tissue from these mice did not reveal differences. Similarly, FRET measurements showed that PGE1-induced cAMP synthesis in isolated smooth muscle cells was unaffected by NO-GC deletion. However, aortae from GCKO and SMC-GCKO animals were more sensitive to milrinone, a specific inhibitor of PDE3, as the concentration curve for relaxation was shifted to the left. Analysis of PDE3 expression in aorta showed an approximately 50% reduction in PDE3 protein and specific enzyme activity. Similar reduction was detected in platelets but not in heart tissue of GCKO animals. Induction of SMC-specific NO-GC deletion by tamoxifen led to a parallel decline of NO-GC and PDE3 expression. Both proteins were strongly reduced already 5 days after the last tamoxifen injection. In contrast, systolic blood pressure in these animals started to rise only after 10 days and was maximal after 50 days. These data indicate that cGMP, not the increase in blood pressure, is responsible for the expression regulation of PDE3. We conclude that cGMP modulates PDE3 expression in SMC in order to keep up functional cAMP signaling.

The effect of 2-month bromocriptine treatment on the activity of the adenylyl cyclase signaling system in the myocardium and testes of rats with type 2 diabetes

Cardiovascular diseases and dysfunctions of the reproductive system are common complications of type 2 diabetes (T2D), and, therefore, development of new approaches for the alleviation of these pathologies is highly important. Bromocriptine (BC), an agonist of type 2 dopamine receptors, recently became widely used for the treatment of type 2 diabetes; this drug both restores energy metabolism and prevents the development of cardiovascular disease. However, the targets of BC and mechanisms underlying its action are still poorly characterized. The aim of the present work was to investigate the effect of BC treatment on the functional activity of the adenylyl cyclase signaling system (ACSS) in the myocardium and testes of male rats suffering from type 2 diabetes induced by high-fat diet and administration of streptozotocin (25 mg/kg). Oral BC administration (0.6 mg/kg every other day for 60 days) started 90 days after the commencement of highfat diet. Body weight and triglyceride levels were elevated in diabetic rats. Glucose tolerance of the animals was impaired, and they developed insulin resistance. BC treatment enabled the recovery of glucose metabolism parameters and increased the sensitivity of tissues to insulin. Adenylyl cyclase (AC) stimulation by guanylyl imidodiphosphate (GppNHp), relaxin, and the β-adrenergic receptor (β-AR) agonists isoproterenol and norepinephrine in the myocardium of diabetic rats was impaired, while the stimulatory effects of the β3-agonists BRL-37344 and CL-316243 persisted. The inhibitory effect of somatostatin on forskolin-stimulated AC activity was attenuated, while the inhibitory effect of norepinephrine mediated by α2-AR was enhanced. BC treatment normalized adrenergic signaling in the myocardium and partially restored the effects of relaxin and somatostatin on AC. AC activity, both basal and stimulated by GppNHp, forskolin, human chorionic gonadotropin, and pituitary AC-activating polypeptide, decreased in the testis of diabetic rats, and the inhibitory effect of somatostatin was attenuated. BC treatment induced only slight changes in the testicular ACSS. Thus, prolonged BC treatment restored the functional activity of ACSS in the myocardium and testes of diabetic rats; this accounts for the therapeutic effect of BC on the impaired functioning of the cardiovascular and reproductive systems in T2D and should be taken into account upon the selection of treatment strategies for T2D and its complications.

Prunetin signals via G-protein-coupled receptor, GPR30(GPER1): Stimulation of adenylyl cyclase and cAMP-mediated activation of MAPK signaling induces Runx2 expression in osteoblasts to promote bone regeneration

Prunetin is found in red clover and fruit of Prunus avium (red cherry). The effect of prunetin on osteoblast function, its mode of action and bone regeneration in vivo were investigated. Cultures of primary osteoblasts, osteoblastic cell line and HEK293T cells were used for various in vitro studies. Adult female rats received drill-hole injury at the femur diaphysis to assess the bone regenerative effect of prunetin. Prunetin at 10nM significantly (a) increased proliferation and differentiation of primary cultures of osteoblasts harvested from rats and (b) promoted formation of mineralized nodules by bone marrow stromal/osteoprogenitor cells. At this concentration, prunetin did not activate any of the two nuclear estrogen receptors (α and β). However, prunetin triggered signaling via a G-protein-coupled receptor, GPR30/GPER1, and enhanced cAMP levels in osteoblasts. G15, a selective GPR30 antagonist, abolished prunetin-induced increases in osteoblast proliferation, differentiation and intracellular cAMP. In osteoblasts, prunetin up-regulated runt-related transcription factor 2 (Runx2) protein through cAMP-dependent Erk/MAP kinase activation that ultimately resulted in the up-regulation of GPR30. Administration of prunetin at 0.25mg/kg given to rats stimulated bone regeneration at the site of drill hole and up-regulated Runx2 expression in the fractured callus and the effect was comparable to human parathyroid hormone, the only clinically used osteogenic therapy. We conclude that prunetin promotes osteoinduction in vivo and the mechanism is defined by signaling through GPR30 resulting in the up-regulation of the key osteogenic gene Runx2 that in turn up-regulates GPR30.

Functional importance of two conserved residues in intracellular loop 1 and transmembrane region 2 of Family A GPCRs: Insights from ligand binding and signal transduction responses of D1 and D5 dopaminergic receptor mutants

For many G protein-coupled receptors (GPCRs), the role of the first intracellular loop (IL1) and its connections with adjacent transmembrane (TM) regions have not been investigated. Notably, these regions harbor several polar residues such as Ser and Thr. To begin uncovering how these polar residues may contribute to the structural basis for GPCR functionality, we have designed human D1-class receptor mutants (hD1-ST1 and hD5-ST1) whereby all Ser and Thr of IL1 and IL1/TM2 juncture have been replaced by Ala and Val, respectively. Both ST1 mutants exhibited a loss of dopamine affinity but similar binding properties for inverse agonists compared to their parent receptors. As well, these mutations diminished receptor activation for both subtypes, as indicated by an ablated constitutive activity and a pronounced decrease in dopamine potency. Interestingly, both mutants exhibited enhanced dopamine-mediated maximal stimulation (Emax) of adenylyl cyclase that was at least two-fold higher than wild-type. Point mutations for hD1R revealed that the loss in dopamine affinity and potency was attributed to Thr59, while the enhanced Emax of adenylyl cyclase was directly influenced by Ser65. These two residues are conserved among many Family A GPCRs and have recurring molecular interactions among crystallized structures. As such, their functional roles for IL1 and its transition into TM2 reported herein may also be applicable to other GPCRs. Our work thus potentially highlights a structural role of Thr59 and Ser65 in the formation of critical intramolecular interactions for ligand binding and signal transduction of D1-class dopaminergic receptors.

Role of intracellular signaling systems in regulation of erythrocyte microrheology

Erythrocyte deformability and thus the efficiency of the oxygen delivery to tissues depends on three main factors: elasticity of cell membrane, viscosity of cytoplasm, and the erythrocyte surface/volume ratio. The membrane elasticity and stability most considerably contribute to the whole cell deformability. There are experimental data suggesting that erythrocyte deformability is regulated by intracellular signaling pathways. The aim of this work was to study the role of the adenylyl cyclase–cAMP systems and intracellular calcium signaling mechanism in the regulation of erythrocyte deformability. We found that stimulator of adenylyl cyclase (AC) forskolin (10–5 M) and cell-penetrating cAMP analog dB-cAMP (5 × 10–5 M) increased erythrocyte deformability. Inhibitors of the phosphodiesterase (PDE) activity, such as isobutyl methylxanthine, vinpocetine, and cilostazol (10–5 M), also increased the erythrocyte deformability, which provides another line of evidence of the cAMP involvement in the regulation of erythrocyte deformability. On the other hand, stimulation of Ca2+ entry into erythrocytes induced by Ca2+ ionophore A23187 (3 × 10–6 M), sodium fluoride, or sodium vanadate considerably decreased the cell deformability, while blockade of the Ca2+ entry into erythrocytes by verapamil (10–5 M) increased their deformability. Mechanical stress of the erythrocyte membrane in the absence of extracellular Ca2+ did not change the deformability, while the mechanical stress applied in the presence of Ca2+ (50–200 µM) decreased deformability by 4–18%. On the whole, the obtained results suggest that for the increase in the erythrocyte deformability the AC–cAMP–PKA cascade has to be activated, while the pathway triggered by the Ca2+ entry into the cells is required to lower the erythrocyte deformability (elasticity) and hence, to increase the whole cell membrane stability. It is possible that these pathways are coordinated at the PDE level.

Annexin A4 is a novel direct regulator of adenylyl cyclase type 5.

Annexin A4 (AnxA4), a Ca(2+)- and phospholipid-binding protein, is up-regulated in the human failing heart. In this study, we examined the impact of AnxA4 on β-adrenoceptor (β-AR)/cAMP-dependent signal transduction. Expression of murine AnxA4 in human embryonic kidney (HEK)293 cells dose-dependently inhibited cAMP levels after direct stimulation of adenylyl cyclases (ACs) with forskolin (FSK), as determined with an exchange protein activated by cAMP-Förster resonance energy transfer (EPAC-FRET) sensor and an ELISA (control vs. +AnxA4: 1956 ± 162 vs. 1304 ± 185 fmol/µg protein; n = 8). Disruption of the anxA4 gene led to a consistent increase in intracellular cAMP levels in isolated adult mouse cardiomyocytes, with heart-directed expression of the EPAC-FRET sensor, stimulated with FSK, and as determined by ELISA, also in mouse cardiomyocytes stimulated with the β-AR agonist isoproterenol (ISO) (anxA4a(+/+) vs. anxA4a(-/-): 5.1 ± 0.3 vs. 6.7 ± 0.6 fmol/µg protein) or FSK (anxA4a(+/+) vs. anxA4a(-/-): 1891 ± 238 vs. 2796 ± 343 fmol/µg protein; n = 9-10). Coimmunoprecipitation experiments in HEK293 cells revealed a direct interaction of murine AnxA4 with human membrane-bound AC type 5 (AC5). As a functional consequence of AnxA4-mediated AC inhibition, AnxA4 inhibited the FSK-induced transcriptional activation mediated by the cAMP response element (CRE) in reporter gene studies (10-fold vs. control; n = 4 transfections) and reduced the FSK-induced phosphorylation of the CRE-binding protein (CREB) measured on Western blots (control vs. +AnxA4: 150 ± 17% vs. 105 ± 10%; n = 6) and by the use of the indicator of CREB activation caused by phosphorylation (ICAP)-FRET sensor, indicating CREB phosphorylation. Inactivation of AnxA4 in anxA4a(-/-) mice was associated with an increased cardiac response to β-AR stimulation. Together, these results suggest that AnxA4 is a novel direct negative regulator of AC5, adding a new facet to the functions of annexins.

Alterations in adenylyl cyclase sensitivity to hormones in the brain, myocardium, and testes of rats immunized with BSA-conjugated peptide 269–280 of type 3 melanocortin receptor

Binding of the type 3 melanocortin receptors (M3R) functionally coupled to Gs proteins with α-melanocyte-stimulating hormone (α-MSH) or M3R agonist γ-MSH results in the activation of adenylyl cyclase (AC) in the brain, which is responsible for the M3R-mediated regulation of physiological and biochemical processes in the central and peripheral nervous systems. A decrease in the M3R activity leads to energy metabolism disorders, metabolic syndrome, and functional disturbances of the nervous and cardiovascular systems. However, molecular mechanisms of these alterations and the role of the adenylyl cyclase signaling system (ACSS) are yet poorly understood. The aim of this work was to study the effects of a long-term (13 months, 8 injections) immunization of male rats with BSA-conjugated peptide A-[PTNPYCICTTAH269–280]-A (A-[269–280]-A), corresponding to the third extracellular loop of rat M3R, on the functional activity of ACSS and its regulation by neurotransmitters and hormones in rat brain, testes, and myocardium. At the end of the experiment, the body weight of animals decreased, the specific mass of adipose tissue increased, dyslipidemia was observed, and the sensitivity to insulin was reduced in spite of the increase in its secretion in response to a glycemic load. In the brain of immunized rats, the AC-stimulating effects of γ-MSH, noradrenaline, serotonin and PACAP-38 decreased, the stimulating effect of dopamine and AC-inhibiting effects of serotonin and 5-nonyloxytryptamine (an agonist of 5-hydroxytryptamine receptor (5-HTR) of the 1B/1D subtype) increased, while the effects of the M3R/M4R agonist α-MSH and the M4R agonist THIQ remained unchanged. In myocardial membranes, stimulation of AC by the agonists of β3-adrenergic receptors (β3-AR) was enhanced, while the AC-stimulating effects of β1- and β2-agonists were attenuated and the AC effect of relaxin weakened. In testicular membranes, the AC-stimulating effects of chorionic gonadotropin and PACAP-38 decreased, as well as the effect of GppNHp (non-hydrolysable GTP analog). These data indicate that the attenuation of the M3R signaling leads to considerable alterations in the ACSS sensitivity to the hormones playing a key role in the functioning of the nervous, cardiovascular and reproductive systems. The alterations in the ACSS sensitivity observed in brain, myocardium and testes are characterized by hormonal and receptor specificity. Identification of ACSS disorders is one of the approaches to studying etiology and pathogenesis of diseases associated with inhibition of M3R-melanocortin signaling system of the brain.

In vitro metacyclogenesis of Trypanosoma cruzi induced by starvation correlates with a transient adenylyl cyclase stimulation as well as with a constitutive upregulation of adenylyl cyclase expression

The Trypanosoma cruzi adenylyl cyclase (AC) multigene family encodes different isoforms (around 15) sharing a variable large N-terminal domain, which is extracellular and receptor-like, followed by a transmembrane helix and a conserved C-terminal catalytic domain. It was proposed that these key enzymes in the cAMP signalling pathway allow the parasite to sense its changing extracellular milieu in order to rapidly adapt to its new environment, which is generally achieved through a differentiation process. One of the critical differentiation events the parasitic protozoan T. cruzi undergoes during its life cycle, known as metacyclogenesis, occurs in the digestive tract of the insect and corresponds to the differentiation from noninfective epimastigotes to infective metacyclic trypomastigote forms. By in vitro monitoring the activity of AC during metacyclogenesis, we showed that both the activity of AC and the intracellular cAMP content follow a similar pattern of transient stimulation in a two-step process, with a first activation peak occurring during the first hours of nutritional stress and a second peak between 6 and 48h, corresponding to the cellular adhesion. During this differentiation process, a general mechanism of upregulation of AC expression of both mRNA and protein is triggered and in particular for a major subclass of these enzymes that are present in various gene copies commonly associated to the THT gene clusters. Although the scattered genome distribution of these gene copies is rather unusual in trypanosomatids and seems to be a recent acquisition in the evolution of the T. cruzi clade, their encoded product redistributed on the flagellum of the parasite upon differentiation could be important to sense the extracellular milieu.

The Effect of Long-Term Intranasal Serotonin Treatment on Metabolic Parameters and Hormonal Signaling in Rats with High-Fat Diet/Low-Dose Streptozotocin-Induced Type 2 Diabetes.

In the last years the treatment of type 2 diabetes mellitus (DM2) was carried out using regulators of the brain signaling systems. In DM2 the level of the brain serotonin is reduced. So far, the effect of the increase of the brain serotonin level on DM2-induced metabolic and hormonal abnormalities has been studied scarcely. The present work was undertaken with the aim of filling this gap. DM2 was induced in male rats by 150-day high-fat diet and the treatment with low dose of streptozotocin (25 mg/kg) on the 70th day of experiment. From the 90th day, diabetic rats received for two months intranasal serotonin (IS) at a daily dose of 20 μg/rat. The IS treatment of diabetic rats decreased the body weight, and improved glucose tolerance, insulin-induced glucose utilization, and lipid metabolism. Besides, it restored hormonal regulation of adenylyl cyclase (AC) activity in the hypothalamus and normalized AC stimulation by β-adrenergic agonists in the myocardium. In nondiabetic rats the same treatment induced metabolic and hormonal alterations, some of which were similar to those in DM2 but expressed to a lesser extent. In conclusion, the elevation of the brain serotonin level may be regarded as an effective approach to treat DM2 and its complications.

CAMP modulation during sheep in vitro oocyte maturation delays progression of meiosis without affecting oocyte parthenogenetic developmental competence

Removal of oocytes from their natural inhibitory follicular environment results in spontaneous resumption of meiosis independent of normal signaling events that occur in vivo. Controlling the onset of meiotic resumption via maintenance of elevated oocyte cAMP levels with adenylyl cyclase (AC) activation and phosphodiesterase (PDE) inhibition, and subsequent hormone stimulation with follicle FSH has been shown to dramatically improve developmental competence of bovine and murine IVM oocytes. This study evaluated the effect of cAMP modulation during IVM of sheep oocytes on meiotic progression and development to blastocyst after parthenogenetic activation. Changes in oocyte cAMP levels were quantified during the first 2h of in vitro maturation in control or cAMP-modulating medium. No significant changes in intra-oocyte cAMP were observed under control conditions, though a slight and transient drop was noticed at 15min of maturation. Addition of the AC stimulator Forskolin and the PDE inhibitors IBMX altered the cAMP profile, resulting in 10-fold elevation of cAMP by 15min and sustained >3-fold elevated levels from 30 to 120min. The effect of cAMP elevation on meiotic resumption was measured by completion of germinal vesicle breakdown. Modulated oocytes were significantly delayed when compared to control media oocytes. Also, progression to MII was significantly delayed in modulated versus control oocytes at 20 and 24h, though no differences persisted to 28h. Lastly, when control and modulated oocytes were parthenogenetically activated, no differences in blastocyst formation were observed. Thus, while cAMP modulation delayed meiotic progression, it did not improve developmental competence of sheep IVM oocytes.

Peptide 612–627 of thyrotropin receptor and its modified analogs as regulators of adenylyl cyclase in rat thyroid gland

The specific activity of the thyroid gland is regulated by thyroid-stimulating hormone (TSH) via TSH receptor (TSHR). This receptor is coupled with various types of G proteins, including Gs proteins, through which TSH stimulates activity of enzyme adenylyl cyclase (AC). Since the use of TSH in medicine is restricted, selective regulators of TSHR with activity of agonists and antagonists are being developed. One approach to their creation is development of peptides corresponding to the functionally important TSHR regions that are located in its cytoplasmic loops and are involved in binding and activation of G proteins. We synthesized peptide corresponding to the C-terminal region 612–627 of the third cytoplasmic loop of TSHR and its derivatives modified by residues of palmitic acid (from the N- or C-termini) or by polylysine dendrimer (from the N-terminus) and we studied their effect on the basal and TSH-stimulated AC activity in membrane fractions isolated from the rat thyroid gland. The most active was peptide 612–627-K(Pal)A modified by palmitate from the C-terminus, where the hydrophobic transmembrane region is located in TSHR. At the micromolar concentrations, it increased AC activity and reduced the AC-stimulating TSH effect. The action of 612–627-K(Pal)A was directed to its homologous TSHR, which is indicated by the following facts: the ingibition of Gs proteins, the transductory component of the AC system, by treatment of the membranes with cholera toxin blocked the AC effect of peptide and this effect was not revealed in the tissues where TSHR are absent, the peptide did not influence the stimulating AC effects of hormones acting via other receptors. The unmodified peptide and the peptide with N-terminal dendrimer had a much lower ability to activate AC in the thyroid gland than 612–627-K(Pal)A, whereas the peptide modified by palmitate from the N-terminus was inactive. At the same time, the peptide modified by dendrimer was comparable with 612–627-K(Pal)A by the ability to inhibit the AC action of TSH, but it also decreased (although to the lesser degree) the AC effects of other hormones, which indicates its low receptor specificity. Thereby, the obtained data indicate the high efficiency of the peptide 612–627-K(Pal)A as a regulator of TSHR and the possibilities of creation of drugs on its basis for regulation of thyroid-gland functions in the case of pathology.

Attenuation of inhibitory influence of hormones on adenylyl cyclase systems in the myocardium and brain of obese and type 2 diabetic rats as affected by the intranasal insulin treatment

The functional state of adenylyl cyclase signaling system (ACSS) and its regulation by the hormones and the inhibitor of adenylyl cyclase (AC), somatostatine (SST), in the brain and myocardium and by 5-nonyloxytryptamine (5-NOT) in the brain of rats of different ages (2- and 7-month-old) with experimental obesity and combination of obesity and type 2 diabetes mellitus (DM2), as well as the effect of the long-term treatment with intranasally administered insulin (II) on ACSS were studied. It was shown that the basal AC activity in obese and DM2 rats increases in the myocardium and, to a lesser extent, in the brain and decreases under the II treatment. The AC stimulating effect of forskolin decreases in the myocardium, but not in the brain of obese and DM2 rats. The II treatment recovers the AC stimulating effect of forskolin in 7-month-old animals, but has little effect in 5-month-old rats. In obesity as well as under the II treatment, the basal AC activity and its stimulation by forskolin change insignificantly. The AC inhibitory effects of 5-NOT and, particularly, SST are strongly attenuated in the investigated pathology, supposedly due to a reduction in the functional activity of Gi-proteins. The treatment of obesity and its combination with DM2 recovers, completely or partially, the AC inhibitory effects of hormones, most of all in the brain. Since the ACSS dysfunctions are causal to metabolic syndrome and DM2, their elimination by the II treatment promises an effective approach to combat these pathologies and their CNS and cardiovascular complications.

Evidence for aggregation of protein kinase CK2 in the cell: a novel strategy for studying CK2 holoenzyme interaction by BRET(2).

Protein kinase CK2 is a ubiquitous pro-survival kinase whose substrate targets are involved in various cellular processes. Crystal structure analysis confirmed constitutive activity of the kinase, yet CK2 activity regulation in the cell is still obscure. In-vitro studies suggest autoinhibitory aggregation of the hetero-tetrameric CK2 holoenzyme as a basis for CK2 regulation. In this study, we applied bioluminescent resonance energy transfer (BRET) technology to investigate CK2 holoenzyme aggregation in living cells. We designed a BRET(2) pair consisting of the fusion proteins CK2α-Rluc8 and CK2α-GFP(2). This BRET(2) sensor reported specific interaction of CK2 holoenzyme complexes. Furthermore, the BRET(2) sensor was applied to study modulators of CK2 aggregation. We found that CK2 aggregation is not static and can be influenced by the CK2-binding protein alpha subunit of the heterotrimeric G-protein that stimulates adenylyl cyclase (Gαs) and the polycationic compound polylysine. Gαs, but not the CK2 substrate β-arrestin2, decreased the BRET(2) signal by up to 50%. Likewise polylysine, but not the CK2 inhibitor DRB, decreased the signal in a dose-dependent manner up to 50%. For the first time, we present direct experimental evidence for CK2 holoenzyme aggregates in the cell. Our data suggest that CK2 activity may be controlled by holoenzyme aggregation, to our knowledge a novel mechanism for protein kinase regulation. Moreover, the BRET(2) sensor used in our study is a novel tool for studying CK2 regulation by aggregation and pharmacological screening for novel allosteric CK2 effectors.

Estradiol increases cAMP in the oviductal secretory cells through a nongenomic mechanism.

In the rat oviduct, estradiol (E2) accelerates egg transport by a nongenomic action that requires previous conversion of E2 to methoxyestrogens via catechol-O-methyltranferase (COMT) and activation of estrogen receptor (ER) with subsequent production of cAMP and inositol triphosphate (IP3). However, the role of the different oviductal cellular phenotypes on this E2 nongenomic pathway remains undetermined. The aim of this study was to investigate the effect of E2 on the levels of cAMP and IP3 in primary cultures of secretory and smooth muscle cells from rat oviducts and determine the mechanism by which E2 increases cAMP in the secretory cells. In the secretory cells, E2 increased cAMP but not IP3, while in the smooth muscle cells E2 decreased cAMP and increased IP3. Suppression of protein synthesis by actinomycin D did not prevent the E2-induced cAMP increase, but this was blocked by the ER antagonist ICI 182 780 and the inhibitors of COMT OR 486, G protein-α inhibitory (Gαi) protein pertussis toxin and adenylyl cyclase (AC) SQ 22536. Expression of the mRNA for the enzymes that metabolizes estrogens, Comt, Cyp1a1, and Cyp1b1 was found in the secretory cells, but this was not affected by E2. Finally, confocal immunofluorescence analysis showed that E2 induced colocalization between ESR1 (ERα) and Gαi in extranuclear regions of the secretory cells. We conclude that E2 differentially regulates cAMP and IP3 in the secretory and smooth muscle cells of the rat oviduct. In the secretory cells, E2 increases cAMP via a nongenomic action that requires activation of COMT and ER, coupling between ESR1 and Gαi, and stimulation of AC.

Differential dopamine receptor subtype regulation of adenylyl cyclases in lipid rafts in human embryonic kidney and renal proximal tubule cells

Dopamine D1-like receptors (D1R and D5R) stimulate adenylyl cyclase (AC) activity, whereas the D2-like receptors (D2, D3 and D4) inhibit AC activity. D1R, but not the D5R, has been reported to regulate AC activity in lipid rafts (LRs). We tested the hypothesis that D1R and D5R differentially regulate AC activity in LRs using human embryonic kidney (HEK) 293 cells heterologously expressing human D1 or D5 receptor (HEK-hD1R or HEK-hD5R) and human renal proximal tubule (hRPT) cells that endogenously express D1R and D5R. Of the AC isoforms expressed in HEK and hRPT cells (AC3, AC5, AC6, AC7, and AC9), AC5/6 was distributed to a greater extent in LRs than non-LRs in HEK-hD1R (84.5±2.3% of total), HEK-hD5R (68.9±3.1% of total), and hRPT cells (66.6±2.2% of total) (P<0.05, n=4/group). In HEK-hD1R cells, the D1-like receptor agonist fenoldopam (1μM/15min) increased AC5/6 protein (+17.2±3.9% of control) in LRs but decreased it in non-LRs (−47.3±5.3% of control) (P<0.05, vs. control, n=4/group). By contrast, in HEK-hD5R cells, fenoldopam increased AC5/6 protein in non-LRs (+67.1±5.3% of control, P<0.006, vs. control, n=4) but had no effect in LRs. In hRPT cells, fenoldopam increased AC5/6 in LRs but had little effect in non-LRs. Disruption of LRs with methyl-β-cyclodextrin decreased basal AC activity in HEK-D1R (−94.5±2.0% of control) and HEK-D5R cells (−87.1±4.6% of control) but increased it in hRPT cells (6.8±0.5-fold). AC6 activity was stimulated to a greater extent by D1R than D5R, in agreement with the greater colocalization of AC5/6 with D1R than D5R in LRs. We conclude that LRs are essential not only for the proper membrane distribution and maintenance of AC5/6 activity but also for the regulation of D1R- and D5R-mediated AC signaling.

Increased striatal adenosine A2A receptor levels is an early event in Parkinson’s disease-related pathology and it is potentially regulated by miR-34b

Adenosine A2A receptor (A2AR) is a G-protein coupled receptor that stimulates adenylyl cyclase activity. In the brain, A2ARs are found highly enriched in striatal GABAergic medium spiny neurons, related to the control of voluntary movement. Pharmacological modulation of A2ARs is particularly useful in Parkinson’s disease (PD) due to their property of antagonizing dopamine D2 receptor activity. Increases in A2AR levels have been described in PD patients showing an important loss of dopaminergic denervation markers, but no data have been reported about A2AR levels in incidental PD brains. In the present report, we show that increased A2ARs protein levels were also detected in the putamen of incidental PD cases (Braak PD stages 1–2) with respect to age-matched controls. By contrast, A2ARs mRNA levels remained unchanged, suggesting that posttranslational mechanisms could be involved in the regulation of A2ARs. It has been described how miR-34b/c downregulation is an early event in PD cases. We found that miR-34b levels are also significantly reduced in the putamen of incidental PD cases and along disease progression. Given that 3′UTR of A2AR contains a predicted target site for miR-34b, the potential role of this miRNA in protein A2AR levels was assessed. In vitro studies revealed that endogenous A2AR protein levels increased when miR-34b function was blocked using a specific anti-miR-34b. Moreover, using a luciferase reporter assay with point mutations in a miR-34b predicted binding site within the 3'UTR region of A2AR mRNA abolished the effect of the miRNA using a miR-34b mimic. In addition, we showed a reduced percentage of DNA methylation in the 5'UTR region of ADORA2A in advanced PD cases. Overall, these findings reveal that increased A2AR protein levels occur in asymptomatic PD patients and provide new insights into the molecular mechanisms underlying A2AR expression levels along the progression of this neurodegenerative disease.