Spatial bias in cAMP generation determines biological responses to PTH type 1 receptor activation

A stable Chinese hamster ovary fibroblast line expressing the rat vascular type 1a angiotensin II (ANG II) receptor was used to study the lipid-derived signal transduction pathways elicited by type 1a ANG II receptor activation. ANG II caused a biphasic and dose-dependent increase in diacylglycerol (DAG) accumulation with an initial peak at 15 s (181 +/- 11% of control, P < 0.02) and a second sustained peak at 5-10 min (214 +/- 10% of control, P < 0.02). The late DAG peak was derived from phosphatidylcholine (PC), and the formation was blocked by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. ANG II also increased phosphatidic acid (PA) production nearly fourfold by 7.5 min. In the presence of ethanol, ANG II markedly increased phosphatidylethanol (PEt) formation, indicating activation of phospholipase D (PLD). ANG II was shown to increase the mass of three separate PA species, one of which apparently originated from DAG kinase action on PC-phospholipase C (PLC)-produced DAG, providing evidence for PC-PLC activity. ANG II also formed a third PA species, which originated neither from PLD nor from DAG kinase. These results demonstrate that multiple lipid signals propagated via collateral stimulation of PLC and PLD are generated by specific activation of the vascular type 1a ANG II receptor.

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First Report ofEurycoma longifoliaJack Root Extract Causing Relaxation of Aortic Rings in Rats

BioMed Research International ◽

10.1155/2016/1361508 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Bae Huey Tee ◽

See Ziau Hoe ◽

Swee Hung Cheah ◽

Sau Kuen Lam

Keyword(s):

Erectile Function ◽

Receptor Activation ◽

Root Extract ◽

Ang Ii ◽

Angiotensin I ◽

Eurycoma Longifolia ◽

Vasodilatory Effect

AlthoughEurycoma longifoliahas been studied for erectile function, the blood pressure- (BP-) lowering effect has yet to be verified. Hence, this study aims at investigating the BP-lowering properties of the plant with a view to develop an antihypertensive agent that could also preserve erectile function. Ethanolic root extract was partitioned by hexane, dichloromethane (DCM), ethyl acetate, butanol, and water. The DCM fraction, found to be potent in relaxing phenylephrine- (PE-) precontracted rat aortic rings, was further purified by column chromatography. Subfraction DCM-II, being the most active in relaxing aortae, was studied for effects on the renin-angiotensin and kallikrein-kinin systems in aortic rings. The effect of DCM-II on angiotensin-converting enzyme (ACE) activity was also evaluatedin vitro. Results showed that DCM-II reduced (p<0.05) the contractions evoked by angiotensin I and angiotensin II (Ang II). In PE-precontracted rings treated with DCM-II, the Ang II-induced contraction was attenuated (p<0.05) while bradykinin- (BK-) induced relaxation enhanced (p<0.001).In vitro, DCM-II inhibited (p<0.001) the activity of ACE. These data demonstrate that the vasodilatory effect of DCM-II appears to be mediatedviainhibition of Ang II type 1 receptor and ACE as well as enhancement of Ang II type 2 receptor activation and BK activity.

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Residues within the Transmembrane Domain of the Glucagon-Like Peptide-1 Receptor Involved in Ligand Binding and Receptor Activation: Modelling the Ligand-Bound Receptor

Molecular Endocrinology ◽

10.1210/me.2011-1160 ◽

2011 ◽

Vol 25 (10) ◽

pp. 1804-1818 ◽

Cited By ~ 37

Author(s):

K. Coopman ◽

R. Wallis ◽

G. Robb ◽

A. J. H. Brown ◽

G. F. Wilkinson ◽

...

Keyword(s):

Ligand Binding ◽

Structural Model ◽

Transmembrane Domain ◽

Transmembrane Helix ◽

Receptor Activation ◽

Agonist Affinity ◽

Camp Generation ◽

N Terminus ◽

Glucagon Like Peptide ◽

Glucagon Like Peptide 1

The C-terminal regions of glucagon-like peptide-1 (GLP-1) bind to the N terminus of the GLP-1 receptor (GLP-1R), facilitating interaction of the ligand N terminus with the receptor transmembrane domain. In contrast, the agonist exendin-4 relies less on the transmembrane domain, and truncated antagonist analogs (e.g. exendin 9–39) may interact solely with the receptor N terminus. Here we used mutagenesis to explore the role of residues highly conserved in the predicted transmembrane helices of mammalian GLP-1Rs and conserved in family B G protein coupled receptors in ligand binding and GLP-1R activation. By iteration using information from the mutagenesis, along with the available crystal structure of the receptor N terminus and a model of the active opsin transmembrane domain, we developed a structural receptor model with GLP-1 bound and used this to better understand consequences of mutations. Mutation at Y152 [transmembrane helix (TM) 1], R190 (TM2), Y235 (TM3), H363 (TM6), and E364 (TM6) produced similar reductions in affinity for GLP-1 and exendin 9–39. In contrast, other mutations either preferentially [K197 (TM2), Q234 (TM3), and W284 (extracellular loop 2)] or solely [D198 (TM2) and R310 (TM5)] reduced GLP-1 affinity. Reduced agonist affinity was always associated with reduced potency. However, reductions in potency exceeded reductions in agonist affinity for K197A, W284A, and R310A, while H363A was uncoupled from cAMP generation, highlighting critical roles of these residues in translating binding to activation. Data show important roles in ligand binding and receptor activation of conserved residues within the transmembrane domain of the GLP-1R. The receptor structural model provides insight into the roles of these residues.

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878 CHRONIC OXIDATIVE-NITROSATIVE STRESS VIA ANGIOTENSIN II TYPE 1 RECEPTOR ACTIVATION INVOLVES IN DYSFUNCTION OF CORONARY VASODILATION IN METABOLIC SYNDROME RATS, SHRSP.Z-Leprf1/IzmDmcr RATS (SHRSP.ZF)

Journal of Hypertension ◽

10.1097/01.hjh.0000420444.56629.5b ◽

2012 ◽

Vol 30 ◽

pp. e257

Author(s):

Satomi Kagota ◽

Kana Maruyama ◽

Yukari Tada ◽

Kazuhito Fukushima ◽

Keiji Umetani ◽

...

Keyword(s):

Metabolic Syndrome ◽

Angiotensin Ii ◽

Nitrosative Stress ◽

Receptor Activation ◽

Coronary Vasodilation

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ANG II AT2 receptor modulates AT1receptor-mediated descending vasa recta endothelial Ca2+ signaling

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00317.2002 ◽

2003 ◽

Vol 284 (3) ◽

pp. H779-H789 ◽

Cited By ~ 23

Author(s):

Kristie Rhinehart ◽

Corey A. Handelsman ◽

Erik P. Silldorff ◽

Thomas L. Pallone

Keyword(s):

Receptor Agonist ◽

Calcium Concentration ◽

Cyclopiazonic Acid ◽

Receptor Activation ◽

Receptor Subtype ◽

Ang Ii ◽

Receptor Stimulation ◽

Vasa Recta ◽

Stimulation Of

We tested whether the respective angiotensin type 1 (AT1) and 2 (AT2) receptor subtype antagonists losartan and PD-123319 could block the descending vasa recta (DVR) endothelial intracellular calcium concentration ([Ca2+]i) suppression induced by ANG II. ANG II partially reversed the increase in [Ca2+]igenerated by cyclopiazonic acid (CPA; 10−5 M), acetylcholine (ACh; 10−5 M), or bradykinin (BK; 10−7 M). Losartan (10−5 M) blocked that effect. When vessels were treated with ANG II before stimulation with BK and ACh, concomitant AT2 receptor blockade with PD-123319 (10−8 M) augmented the suppression of endothelial [Ca2+]i responses. Similarly, preactivation with the AT2 receptor agonist CGP-42112A (10−8 M) prevented AT1 receptor stimulation with ANG II + PD-123319 from suppressing endothelial [Ca2+]i. In contrast to endothelial [Ca2+]i suppression by ANG II, pericyte [Ca2+]i exhibited typical peak and plateau [Ca2+]i responses that were blocked by losartan but not PD-123319. DVR vasoconstriction by ANG II was augmented when AT2 receptors were blocked with PD-123319. Similarly, AT2 receptor stimulation with CGP-42112A delayed the onset of ANG II-induced constriction. PD-123319 alone (10−5 M) showed no AT1-like action to constrict microperfused DVR or increase pericyte [Ca2+]i. We conclude that ANG II suppression of endothelial [Ca2+]i and stimulation of pericyte [Ca2+]i is mediated by AT1 or AT1-like receptors. Furthermore, AT2 receptor activation opposes ANG II-induced endothelial [Ca2+]i suppression and abrogates ANG II-induced DVR vasoconstriction.

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ErbB-1 and ErbB-2 Acquire Distinct Signaling Properties Dependent upon Their Dimerization Partner

Molecular and Cellular Biology ◽

10.1128/mcb.18.9.5042 ◽

1998 ◽

Vol 18 (9) ◽

pp. 5042-5051 ◽

Cited By ~ 161

Author(s):

Monilola A. Olayioye ◽

Diana Graus-Porta ◽

Roger R. Beerli ◽

Jack Rohrer ◽

Brigitte Gay ◽

...

Keyword(s):

Intracellular Signaling ◽

Adaptor Protein ◽

Receptor Activation ◽

Erbb Receptors ◽

Antibody Treatment ◽

Receptor Phosphorylation ◽

Biological Responses ◽

Monoclonal Antibody Treatment ◽

Src Homology 2 Domain ◽

Phosphopeptide Mapping

ABSTRACT The different epidermal growth factor (EGF)-related peptides elicit a diverse array of biological responses as the result of their ability to activate distinct subsets of ErbB receptor dimers, leading to the recruitment of different intracellular signaling networks. To specifically examine dimerization-dependent modulation of receptor signaling, we constructed NIH 3T3 cell lines expressing ErbB-1 and ErbB-2 singly and in pairwise combinations with each other ErbB family member. This model system allowed the comparison of EGF-activated ErbB-1 with ErbB-1 activated by Neu differentiation factor (NDF)-induced heterodimerization with ErbB-4. In both cases, ErbB-1 coupled to the adaptor protein Shc, but only when activated by EGF was it able to interact with Grb2. Compared to the rapid internalization of EGF-activated ErbB-1, NDF-activated ErbB-1 showed delayed internalization characteristics. Furthermore, the p85 subunit of phosphatidylinositol kinase (PI3-K) associated with EGF-activated ErbB-1 in a biphasic manner, whereas association with ErbB-1 transactivated by ErbB-4 was monophasic. The signaling properties of ErbB-2 following heterodimerization with the other ErbB receptors or homodimerization induced by point mutation or monoclonal antibody treatment were also analyzed. ErbB-2 binding to peptides containing the Src homology 2 domain of Grb2 or p85 and the phosphotyrosine binding domain of Shc varied according to the mode of receptor activation. Finally, tryptic phosphopeptide mapping of both ErbB-1 and ErbB-2 revealed that receptor phosphorylation is dependent on the dimerization partner. Differential receptor phosphorylation may, therefore, be the basis for the differences in the signaling properties observed.

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Capsaicin Inhibits Activation of Voltage-Gated Sodium Currents in Capsaicin-Sensitive Trigeminal Ganglion Neurons

Journal of Neurophysiology ◽

10.1152/jn.2001.85.2.745 ◽

2001 ◽

Vol 85 (2) ◽

pp. 745-758 ◽

Cited By ~ 85

Author(s):

L. Liu ◽

M. Oortgiesen ◽

L. Li ◽

S. A. Simon

Keyword(s):

Trigeminal Ganglion ◽

Second Messengers ◽

Receptor Activation ◽

Hot Pepper ◽

Capsaicin Receptor ◽

Voltage Gated ◽

Analgesic Effects ◽

Voltage Gated Sodium Channels ◽

Camp Generation ◽

Ganglion Neurons

Capsaicin, the pungent ingredient in hot pepper, activates nociceptors to produce pain and inflammation. However, repeated exposures of capsaicin will cause desensitization to nociceptive stimuli. In cultured trigeminal ganglion (TG) neurons, we investigated mechanisms underlying capsaicin-mediated inhibition of action potentials (APs) and modulation of voltage-gated sodium channels (VGSCs). Capsaicin (1 μM) inhibited APs and VGSCs only in capsaicin-sensitive neurons. Repeated applications of capsaicin produced depolarizing potentials but failed to evoke APs. The capsaicin-induced inhibition of VGSCs was prevented by preexposing the capsaicin receptor antagonist, capsazepine (CPZ). The magnitude of the capsaicin-induced inhibition of VGSCs was dose dependent, having a K 1/2 = 0.45 μM. The magnitude of the inhibition of VGSCs was proportional to the capsaicin induced current (for – I CAP < 0.2 nA). Capsaicin inhibited activation of VGSCs without changing the voltage dependence of activation or markedly changing channel inactivation and use-dependent block. To explore the changes leading to this inhibition, it was found that capsaicin increased cAMP with a K 1/2 = 0.18 μM. At 1 μM capsaicin, this cAMP generation was inhibited 64% by10 μM CPZ, suggesting that activation of capsaicin receptors increased cAMP. The addition of 100 μM CPT-cAMP increased the capsaicin-activated currents but inhibited the VGSCs in both capsaicin-sensitive and -insensitive neurons. In summary, the inhibitory effects of capsaicin on VGSCs and the generation of APs are mediated by activation of capsaicin receptors. The capsaicin-induced activation of second messengers, such as cAMP, play a part in this modulation. These data distinguish two pathways by which neuronal sensitivity can be diminished by capsaicin: by modulation of the capsaicin receptor sensitivity, since the block of VGSCs is proportional to the magnitude of the capsaicin-evoked currents, and by modulation of VGSCs through second messengers elevated by capsaicin receptor activation. These mechanisms are likely to be important in understanding the analgesic effects of capsaicin.

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The Dynamics of the Neuropeptide Y Receptor Type 1 Investigated by Solid-State NMR and Molecular Dynamics Simulation

Molecules ◽

10.3390/molecules25235489 ◽

2020 ◽

Vol 25 (23) ◽

pp. 5489

Author(s):

Alexander Vogel ◽

Mathias Bosse ◽

Marcel Gauglitz ◽

Sarah Wistuba ◽

Peter Schmidt ◽

...

Keyword(s):

Molecular Dynamics ◽

Solid State ◽

Neuropeptide Y ◽

Solid State Nmr ◽

Bound State ◽

Receptor Activation ◽

Order Parameters ◽

Dynamics Simulation ◽

15N Nmr

We report data on the structural dynamics of the neuropeptide Y (NPY) G-protein-coupled receptor (GPCR) type 1 (Y1R), a typical representative of class A peptide ligand GPCRs, using a combination of solid-state NMR and molecular dynamics (MD) simulation. First, the equilibrium dynamics of Y1R were studied using 15N-NMR and quantitative determination of 1H-13C order parameters through the measurement of dipolar couplings in separated-local-field NMR experiments. Order parameters reporting the amplitudes of the molecular motions of the C-H bond vectors of Y1R in DMPC membranes are 0.57 for the Cα sites and lower in the side chains (0.37 for the CH2 and 0.18 for the CH3 groups). Different NMR excitation schemes identify relatively rigid and also dynamic segments of the molecule. In monounsaturated membranes composed of longer lipid chains, Y1R is more rigid, attributed to a higher hydrophobic thickness of the lipid membrane. The presence of an antagonist or NPY has little influence on the amplitude of motions, whereas the addition of agonist and arrestin led to a pronounced rigidization. To investigate Y1R dynamics with site resolution, we conducted extensive all-atom MD simulations of the apo and antagonist-bound state. In each state, three replicas with a length of 20 μs (with one exception, where the trajectory length was 10 μs) were conducted. In these simulations, order parameters of each residue were determined and showed high values in the transmembrane helices, whereas the loops and termini exhibit much lower order. The extracellular helix segments undergo larger amplitude motions than their intracellular counterparts, whereas the opposite is observed for the loops, Helix 8, and termini. Only minor differences in order were observed between the apo and antagonist-bound state, whereas the time scale of the motions is shorter for the apo state. Although these relatively fast motions occurring with correlation times of ns up to a few µs have no direct relevance for receptor activation, it is believed that they represent the prerequisite for larger conformational transitions in proteins.

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