Biology subjects

Strachan, R. T.

Publications and source records attributed to Strachan, R. T..

4 recordsLinked to original sources

bioRxiv2026

Conformational Basis of Functionally Selective Allosteric Modulation of the Angiotensin II type 1 Receptor by Small Molecules

Blockade of signaling through the angiotensin II type 1 receptor (AT1R), a prototypical G protein-coupled receptor (GPCR), by angiotensin receptor blockers (ARBs) is a major therapeutic approach to treating a wide variety of cardiovascular and renal diseases1. Like most GPCRs, the AT1R signals through two transducers, G proteins and {beta}-arrestins2,3. Previous reports have described {beta}-arrestin-biased peptide orthosteric agonists for the AT1R with potential therapeutic advantages over currently available unbiased ARBs4-6. Here we report the DNA- encoded library screening-guided isolation and pharmacological characterization of the first small molecule AT1R allosteric ligands. We use cryo-electron microscopy, double electron- electron resonance spectroscopy, molecular dynamics simulations, and targeted mutagenesis to determine their binding sites, binding modes and conformational mechanisms driving their unique and divergent modulatory effects on G protein and {beta}-arrestin pathways. Our findings uncover new mechanisms for precisely controlling the dynamic behavior of the AT1R with implications for drug development targeting this pathophysiologically important receptor family.

biochemistry↗

bioRxiv2022

Neurotensin receptor allosterism revealed in complex with a biased allosteric modulator

The NTSR1 neurotensin receptor (NTSR1) is a G protein coupled receptor (GPCR) found in the brain and peripheral tissues with neurotensin (NTS) being its endogenous peptide ligand. In the brain, NTS modulates dopamine neuronal activity, induces opioid-independent analgesia, and regulates food intake. Recent studies indicate that biasing NTSR1 toward {beta}-Arrestin signaling can attenuate the actions of psychostimulants and other drugs of abuse. Here we provide the cryoEM structures of NTSR1 ternary complexes with heterotrimeric Gq and Go with and without the brain penetrant small molecule SBI-553. In functional studies, we discovered that SBI-553 displays complex allosteric actions exemplified by negative allosteric modulation for G proteins that are G subunit selective and positive allosteric modulation and agonism for {beta}-Arrestin translocation at NTSR1. Detailed structural analysis of the allosteric binding site illuminated the structural determinants for biased allosteric modulation of SBI-553 on NTSR1. These insights promise to both accelerate the structure-guided design of more effective NTSR1 therapeutics and provide insights into the complexities of GPCR allosteric modulation.

biophysics↗

bioRxiv2021

Structure-based design of a chemical probe set for the 5-HT5A serotonin receptor

The 5-HT5A receptor (5-HT5AR), for which no selective agonists and only a few antagonists exist, remains the least understood serotonin (5-HT) receptor. A single commercial antagonist (SB-699551) has been widely used to investigate central nervous system (CNS) 5-HT5AR function in neurological disorders, including pain. However, because SB-699551 has affinity for many 5-HTRs, lacks inactive property-matched controls, and has assay interference concerns, it has liabilities as a chemical probe. To better illuminate 5-HT5AR function, we developed a probe set through iterative rounds of molecular docking, pharmacological testing, and optimization. Docking over six million lead-like molecules against a 5-HT5AR homology model identified five mid-M ligand starting points with unique scaffolds. Over multiple rounds of structure-based design and testing, a new quinoline scaffold with high affinity and enhanced selectivity for the 5-HT5AR was developed, leading to UCSF678, a 42 nM arrestin-biased partial agonist at the 5-HT5AR with a much more restricted off-target profile and decreased assay liabilities vs. SB-699551. Site-directed mutagenesis supported the docked pose of UCSF678, which was also consistent with recent published 5-HTR structures. Surprisingly, property-matched analogs of UCSF678 that were either inactive across 5-HTRs or retained affinity for UCSF678s off-targets revealed that 5-HT5AR engagement is nonessential for alleviating pain in a mouse model, contrary to previous studies using less-selective ligands. Relative to SB-699551, these molecules constitute a well-characterized and more selective probe set with which to study the function of the 5-HT5A receptor. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/471449v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@8fb24dorg.highwire.dtl.DTLVardef@2dd84org.highwire.dtl.DTLVardef@1d3346org.highwire.dtl.DTLVardef@1117331_HPS_FORMAT_FIGEXP M_FIG Table of Contents Graphic C_FIG

biophysics↗

bioRxiv2017

Cell-type selective deletion of RSK2 reveals insights into altered signaling in Coffin-Lowry Syndrome

Coffin-Lowry syndrome (CLS) is an X-linked syndromic form of mental retardation characterized by various skeletal dysmorphisms, moderate to severe mental retardation, and in some cases, psychosis. CLS is caused by loss-of-function mutations of the p90 ribosomal S6 kinase 2 (RPS6KA3) gene encoding a growth factor-regulated serine/threonine kinase, ribosomal S6 kinase 2 (RSK2). We previously identified RSK2 as a novel interacting protein that tonically inhibits 5-HT2A receptor signaling by phosphorylating Ser-314 within the third intracellular loop. To determine if RSK2 inhibits 5-HT2A receptor signaling in vivo and whether disruption of RSK2 could lead to schizophrenia-like behaviors - as is seen in some CLS patients - we genetically disrupted the function of RSK2 either globally or selectively in forebrain pyramidal neurons in mice. Both global and forebrain-selective RSK2 deletion augmented the locomotor responses to the psychotomimetic drugs phencyclidine (PCP) and amphetamine (AMPH). Significantly, forebrain-selective deletion of RSK2 augmented 5-HT2A receptor signaling as exemplified by enhanced 5-HT2A-mediated c-fos activation and head-twitch response without altering the levels or distribution of 5-HT2A receptor protein. Thus, RSK2 modulates 5HT2A receptor function in vivo, and disruption of RSK2 leads to augmented psychostimulant-induced responses reminiscent of those seen in many animal models of schizophrenia. These findings strengthen the association between 5-HT2A receptor dysfunction and psychosis, and provide a potential mechanism underlying the schizophrenia-like symptoms present in some CLS patients.\n\nHighlightsO_LIGlobal and cell-type-specific RSK2 knock-out mice were assessed behaviorally and pharmacologically\nC_LIO_LIAugmentation of amphetamine and PCP locomotor responses were seen in both global and forebrain-specific RSK2 KO mice\nC_LIO_LIAugmentation of 5-HT2A serotonin receptor function but not number was also observed\nC_LIO_LIThese alterations reveal insights into mechanisms potentially responsible for behavioral sequlae of Coffin-Lowry Syndrome\nC_LI

neuroscience↗