Nanotechnology and Membrane Receptors: Focus on Angiotensin II Receptors (original) (raw)
Related papers
The AT2 receptor: fact, fancy and fantasy
Regulatory peptides, 1999
The angiotensin AT receptor subtype was recently cloned and pharmacologically characterized but its function still remains elusive 2 and controversial. It is a member of the G-protein coupled receptor superfamily with a minimal sequence homology with the AT 1 receptor, responsible for the known effect of angiotensin II. The AT receptor displays a totally different signaling mechanisms from the 2 AT receptor and involves various phosphatases. It is expressed at low density in adult tissues but up-regulated in pathological 1 circumstances. Clearly, the AT receptor has antiproliferative properties and therefore opposes the growth promoting effect linked to the 2 AT receptor stimulation. It is also reported that the AT receptor regulates ionic fluxes, affects differentiation and nerve regeneration, has 1 2 anti-angiogenic and anti-fibrotic properties and stimulates apoptosis. However, the results, although suggestive, are sometimes equivocal. Obviously, the AT receptor plays a role in the pathogenesis and remodeling of cardiovascular and renal diseases. A more extensive 2 knowledge of the AT receptor could therefore contribute to the understanding of the clincial beneficial effects of the AT receptor
Physiological and pharmacological implications of AT1 versus AT2 receptors
Kidney International, 1998
Physiological and pharmacological implications of AT 1 versus AT 2 receptors. Angiotensin II (Ang II) has diverse physiological actions that lead, for instance, to increases in extracellular volume and peripheral vascular resistance and blood pressure, and it has also been implicated in the regulation of cell growth and differentiation. Molecular cloning and pharmacological studies have defined two major classes of Ang II receptors, designated AT 1 and AT 2. Most effects of Ang II are mediated by AT 1 receptors. Much less is known about the physiological role of AT 2 receptors. Recent evidence suggests involvement of AT 2 receptors in development, cell differentiation, apoptosis, and regeneration in various tissues. AT 1 and AT 2 receptors have been shown to exert counteracting effects on cellular growth and differentiation, vascular tone, and the release of arginine vasopressin. In each condition, the AT 2 receptor appears to down-modulate actions mediated by the AT 1 receptor, resulting in decreased cellular proliferation, decreased levels of serum arginine vasopressin levels, or decreased vasoconstrictor responses. In addition, in neuronal cell lines, the AT 2 receptor exerts antiproliferative actions and promotes neurite outgrowth, an effect accompanied by significant changes in the expression pattern of growth/differentiation-related genes.
Functional Reconstitution of the Angiotensin II Type 2 Receptor and Gi Activation
Circulation Research, 2000
On the basis of the patterns of conserved amino acid sequence, the angiotensin II type 2 (AT(2)) receptor belongs to the family of serpentine receptors, which relay signals from extracellular stimuli to heterotrimeric G proteins. However, the AT(2) receptor signal transduction mechanisms are poorly understood. We have measured AT(2)-triggered activation of purified heterotrimeric proteins in urea-extracted membranes from cultured COS-7 cells expressing the recombinant receptor. This procedure removes contaminating GTP-binding proteins without inactivating the serpentine receptor. Binding studies using [(125)I] angiotensin (Ang) II revealed a single binding site with a K(d)=0.45 and a capacity of 627 fmol/mg protein in the extracted membranes. The AT(2) receptor caused a rapid activation of alpha(i) and alpha(o) but not of alpha(q) and alpha(s), as measured by radioactive guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) binding. Activation required the presence of activated receptors, betagamma, and alpha subunits. As a first step aimed at developing an in vitro assay to examine AT(2) receptor pharmacology, we tested a battery of Ang II-related ligands for their ability to promote AT(1) or AT(2) receptor-catalyzed G(i) activation. Two proteolytic fragments of Ang II, Ang III and Ang1-7, also promoted activation of alpha(i) through the AT(2) receptor. Furthermore, we found that [Sar(1),Ala(8)]Ang II is an antagonist for both AT(1) and AT(2) receptors and that CPG42112 behaves as a partial agonist for the AT(2) receptor. In combination with previous observations, these results show that the AT(2) receptor is fully capable of activating G(i) and provides a new tool for exploring AT(2) receptor pharmacology and interactions with G-protein trimers.
Hypertension, 2011
Novel AT(2)R ligands were designed by substituting individual β-amino acid in the sequence of the native ligand angiotensin II (Ang II). Relative ATR selectivity and functional vascular assays (in vitro AT(2)R-mediated vasorelaxation and in vivo vasodepressor action) were determined. In competition binding experiments using either AT(1)R- or AT(2)R- transfected HEK-293 cells, only β-Asp(1)-Ang II and Ang II fully displaced [(125)I]-Ang II from AT(1)R. In contrast, β-substitutions at each position of Ang II exhibited AT(2)R affinity, with β-Tyr(4)-Ang II and β-Ile(5)-Ang II exhibiting ≈ 1000-fold AT(2)R selectivity. In mouse aortic rings, β-Tyr(4)-Ang II and β-Ile(5)-Ang II evoked vasorelaxation that was sensitive to blockade by the AT(2)R antagonist PD123319 and the nitric oxide synthase inhibitor L-NAME. When tested with a low level of AT(1)R blockade, β-Ile(5)-Ang II (15 pmol/kg per minute IV for 4 hours) reduced blood pressure (BP) in conscious spontaneously hypertensive rats (β-...
PLoS ONE, 2013
The renin-angiotensin system is involved in multiple conditions ranging from cardiovascular disorders to cancer. Components of the pathway, including ACE, renin and angiotensin receptors are targets for disease treatment. This study addresses three receptors of the pathway: AT1, AT2, and MAS and how the receptors are similar and differ in activation by angiotensin peptides. Combining biochemical and amino acid variation data with multiple species sequence alignments, structural models, and docking site predictions allows for visualization of how angiotensin peptides may bind and activate the receptors; allowing identification of conserved and variant mechanisms in the receptors. MAS differs from AT1 favoring Ang-(1-7) and not Ang II binding, while AT2 recently has been suggested to preferentially bind Ang III. A new model of Ang peptide binding to AT1 and AT2 is proposed that correlates data from site directed mutagenesis and photolabled experiments that were previously considered conflicting. Ang II binds AT1 and AT2 through a conserved initial binding mode involving amino acids 111 (consensus 325) of AT1 (Asn) interacting with Tyr (4) of Ang II and 199 and 256 (consensus 512 and 621, a Lys and His respectively) interacting with Phe (8) of Ang II. In MAS these sites are not conserved, leading to differential binding and activation by Ang-(1-7). In both AT1 and AT2, the Ang II peptide may internalize through Phe (8) of Ang II propagating through the receptors' conserved aromatic amino acids to the final photolabled positioning relative to either AT1 (amino acid 294, Asn, consensus 725) or AT2 (138, Leu, consensus 336). Understanding receptor activation provides valuable information for drug design and identification of other receptors that can potentially bind Ang peptides.
Journal of Biological Chemistry, 1997
To identify binding domains between angiotensin II (AngII) and its type 2 receptor (AT 2), two different radiolabeled photoreactive analogs were prepared by replacing either the first or the last amino acid in the peptide with p-benzoyl-L-phenylalanine (Bpa). Digestion of photolabeled receptors with kallikrein revealed that the two photoreactive analogs label the amino-terminal part of the receptor within the first 182 amino acids. Digestion of 125 I-[Bpa 1 ]AngII⅐AT 2 receptor complex with endoproteinase Lys-C produced a glycoprotein of 80 kDa. Deglycosylation of this 80-kDa product decreased its apparent molecular mass to 4.6 kDa and further cleavage of this 4.6-kDa product with V8 protease decreased its molecular mass to 3.6 kDa, circumscribing the labeling site of 125 I-[Bpa 1 ]AngII within amino acids 3-30 of AT 2 receptor. Treatment of 125 I-[Bpa 8 ]AngII⅐AT 2 receptor complex with cyanogen bromide produced two major receptor fragments of 3.6 and 2.6 kDa. Cyanogen bromide hydrolysis of a mutant AT 2 receptor produced two major fragments of 12.6 kDa and 2.6 kDa defining the labeling site of 125 I-[Bpa 8 ]AngII within residues 129-138 of AT 2 receptor. Our results indicate that the aminoterminal tail of the AT 2 receptor interacts with the amino-terminal end of AngII, whereas the inner half of the third transmembrane domain of AT 2 receptor interacts with the carboxyl-terminal end of AngII.
Characterization and development of angiotensin II receptor subtypes (AT1 and AT2) in rat brain
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 1991
Characterization and development of angiotensin II receptor subtypes (AT1 and AT,) in rat brain. Am. J. Physiol. 261 (Regulatory Integrative Comp. Physiol. 30): R209-R216, 1991.-Angiotensin II receptor subtypes (AT1 and AT,) were characterized in rat brain by displacement with the specific angiotensin antagonists Du Pont 753 and CGP 42112A, respectively, and quantitative autoradiography. Young (2-wk-old) rats expressed AT1 receptors in selected limbic system areas, structures involved in cardiovascular and fluid regulation, parts of the hippocampal formation, and the choroid plexus. In young rats, AT, receptors were concentrated in areas involved in control and learning of motor activity, sensory areas, and selected limbic system structures. The cingulate cortex, the molecular layer of the cerebellar cortex, and the superior colliculus contained both ATI and AT, receptors. The number of ATI receptors in most areas of adult (&wk-old) rats was similar to or even higher than that present in young rats. Conversely, AT, receptors were always much lower in number in adult animals, and in some areas they were undetectable in adults. Their differential localization and development suggest different functions for the specific angiotensin II receptor subtypes. angiotensin receptor subtypes; Du Pont 753; CGP 42112A; renin-angiotensin system; receptor development IN ADULT RATS, the brain angiotensin II (ANG II) system, including specific ANG II receptors located in very select areas, is involved in the central regulation of cardiovascular function, drinking and fluid metabolism, salt appetite, vasopressin release, and stress (4, 5, 13, 14, 21, 23, 24). Peripherally formed ANG II, present in the has been proposed on the basis of the response of smooth muscle to ANG II synthetic analogues (19). More recently, terized two subtypes in peripheral of ANG II receptors were charactissues on the basis of their sensitivity to reducing agents (7, 10-12) and their displacement with newly developed specific ANG II antagonists (6, 8, 9, 30). AT, receptors are sensitive to the reducing agent dithiothreitol (DTT) (7,9-12) and to displacement by the selective ANG II antagonist Du Pont 753 (8, 9). ANG II binding to the AT, receptors is resistant to DTT and selectively displaced by the ANG II-receptor antagonist CGP 42112A (30). Q uantitative autoradiography and displacement with the selective ANG II-receptor antagonists revealed that the rat brain contains AT1 receptors lot ular nucleus ated in the s , nucleus of ubfornical organ, pa the solitary tract, raven and tricarea postrema and AT, receptors localized in the inferior olive (27). The characteristics of the brain AT1 and AT2 receptors was similar to those described in peripheral organs (27). We have in the inferior recently shown by autoradiography that, olive, parasolitary and hypoglossal nuclei, and cerebellar cortex, the brain of young rats expresses more ANG II receptors than that of adult animals (28) and that, in the inferior olive of young and adult rats, the binding is insensitive to DTT (29). These observations suggested that young rats may express more AT, receptors than their adult controls. To determine the detailed developmental pattern of the receptor subtypes throughout the brain, we studied all areas containing significant numbers of ANG II receptors and compared their distribution and sensitivity to selected ANG II general circulation, binds to brain ANG II receptors antagonists in young (2-wk-o located in circumventricular organs outside the blood-rats. brain barrier (16, 21, 22) and contributes to the central regulation of cardiovascular function and fluid homeo-MATERIALS AND METHODS