Author : Stephanie Clement
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (973 download)
Book Synopsis Biased Signaling and Allosteric Modulation of the Angiotensin II Type 1 Receptor by : Stephanie Clement
Download or read book Biased Signaling and Allosteric Modulation of the Angiotensin II Type 1 Receptor written by Stephanie Clement and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "G protein coupled receptors (GPCR) represent over 30% of drug targets and are involved in nearly all physiological and cellular responses. The angiotensin II (AngII) type I receptor (AT1R) is an important member of this receptor family. Its main endogenous ligand is the hormone angiotensin II (AngII), which regulates blood volume and vascular resistance, through the renin-angiotensin system (RAS). This hormone is involved in hypertension and other cardiovascular diseases. A way to improve today's therapeutic approach is to aim for the activation of the beneficial cellular responses without activating the ones responsible for undesirable effects. This type of response can be achieved using ligands that show functional selectivity, also known as biased signaling. This type of ligand imposes distinct conformations to the receptor, therefore promoting selective downstream effector activation. Moreover, our lab has recently shown that functional selectivity was possible using an allosteric modulator (a ligand binding to any site on a GPCR that is topographically distinct from the endogenous binding site). Our group has shown that a peptide mimic of a sequence derived from the second extracellular loop (ECL2) domains of the prostaglandin F2[alpha] (PGF2[alpha]) receptor (FP) acted as a biased-allosteric modulator of FP. We hypothesized that the ECL2 of other GPCRs can be used as putative biased-allosteric modulators. To test this, we used the angiotensin II (AngII) type I receptor (AT1R). We have examined the effects of peptides (SC0023/SC0024) derived from AT1R's ECL2 in vascular smooth muscle cells (VSMC). This was done using techniques including western blots, Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) and [3H]-Thymidine incorporation. We show in VSMCs that the SC0023 peptide decreases angiotensin II-induced ERK1/2 activation and inositol monophosphate (IP1) production, thus acting as a negative allosteric modulator (NAM) on these signaling pathways. Conversely, SC0024 has no effect on ERK1/2 while acting as a positive allosteric modulator (PAM) on IP1 production. Interestingly, the SC0023 peptide showed no modulatory effect on proliferation in response to angiotensin II, whereas the SC0024 peptide inhibited almost completely this response, hence acting as a NAM on AngII-mediated proliferation. In addition, structure-function studies underscored the importance of three residues (Phe-His-Tyr) of peptide SC0024 for its NAM effect on proliferation. More importantly, these peptides alone showed no effect on any of the pathways studied, thus only working in the presence of agonist, which is characteristic of most allosteric modulators. These data imply that these two peptides derived from the ECL of AT1R are allosteric modulators with biased signaling properties. Indeed, SC0023 acts as a NAM of ERK1/2 activation and IP1 production, while SC0024 acts as a PAM of IP1 production and a NAM of proliferation. Ultimately, understanding how the ECL2 is allosterically biasing its receptor will allow us to design new and more efficient therapeutics." --