5 research outputs found
Identification of the GPR55 Antagonist Binding Site Using a Novel Set of High-Potency GPR55 Selective Ligands
GPR55 is a class A G protein-coupled
receptor (GPCR) that has been
implicated in inflammatory pain, neuropathic pain, metabolic disorder,
bone development, and cancer. Initially deorphanized as a cannabinoid
receptor, GPR55 has been shown to be activated by non-cannabinoid
ligands such as l-α-lysophosphatidylinositol (LPI).
While there is a growing body of evidence of physiological and pathophysiological
roles for GPR55, the paucity of specific antagonists has limited its
study. In collaboration with the Molecular Libraries Probe Production
Centers Network initiative, we identified a series of GPR55 antagonists
using a β-arrestin, high-throughput, high-content screen of
∼300000 compounds. This screen yielded novel, GPR55 antagonist
chemotypes with IC<sub>50</sub> values in the range of 0.16–2.72
μM [Heynen-Genel, S., et al. (2010) Screening for Selective
Ligands for GPR55: Antagonists (ML191, ML192, ML193) (Bookshelf ID
NBK66153; PMID entry 22091481)]. Importantly, many of the GPR55 antagonists
were completely selective, with no agonism or antagonism against GPR35,
CB1, or CB2 up to 20 μM. Using a model of the GPR55 inactive
state, we studied the binding of an antagonist series that emerged
from this screen. These studies suggest that GPR55 antagonists possess
a head region that occupies a horizontal binding pocket extending
into the extracellular loop region, a central ligand portion that
fits vertically in the receptor binding pocket and terminates with
a pendant aromatic or heterocyclic ring that juts out. Both the region
that extends extracellularly and the pendant ring are features associated
with antagonism. Taken together, our results provide a set of design
rules for the development of second-generation GPR55 selective antagonists
Inhibition of Hematopoietic Protein Tyrosine Phosphatase Augments and Prolongs ERK1/2 and p38 Activation
The hematopoietic protein tyrosine phosphatase (HePTP)
is implicated
in the development of blood cancers through its ability to negatively
regulate the mitogen-activated protein kinases (MAPKs) ERK1/2 and
p38. Small-molecule modulators of HePTP activity may become valuable
in treating hematopoietic malignancies such as T cell acute lymphoblastic
leukemia (T-ALL) and acute myelogenous leukemia (AML). Moreover, such
compounds will further elucidate the regulation of MAPKs in hematopoietic
cells. Although transient activation of MAPKs is crucial for growth
and proliferation, prolonged activation of these important signaling
molecules induces differentiation, cell cycle arrest, cell senescence,
and apoptosis. Specific HePTP inhibitors may promote the latter and
thereby may halt the growth of cancer cells. Here, we report the development
of a small molecule that augments ERK1/2 and p38 activation in human
T cells, specifically by inhibiting HePTP. Structure–activity
relationship analysis, <i>in silico</i> docking studies,
and mutagenesis experiments reveal how the inhibitor achieves selectivity
for HePTP over related phosphatases by interacting with unique amino
acid residues in the periphery of the highly conserved catalytic pocket.
Importantly, we utilize this compound to show that pharmacological
inhibition of HePTP not only augments but also prolongs activation
of ERK1/2 and, especially, p38. Moreover, we present similar effects
in leukocytes from mice intraperitoneally injected with the inhibitor
at doses as low as 3 mg/kg. Our results warrant future studies with
this probe compound that may establish HePTP as a new drug target
for acute leukemic conditions
Discovery of Sulfonamidebenzamides as Selective Apoptotic CHOP Pathway Activators of the Unfolded Protein Response
Cellular proteins that fail to fold
properly result in inactive
or disfunctional proteins that can have toxic functions. The unfolded
protein response (UPR) is a two-tiered cellular mechanism initiated
by eukaryotic cells that have accumulated misfolded proteins within
the endoplasmic reticulum (ER). An adaptive pathway facilitates the
clearance of the undesired proteins; however, if overwhelmed, cells
trigger apoptosis by upregulating transcription factors such as C/EBP-homologous
protein (CHOP). A high throughput screen was performed directed at
identifying compounds that selectively upregulate the apoptotic CHOP
pathway while avoiding adaptive signaling cascades, resulting in a
sulfonamidebenzamide chemotype that was optimized. These efforts produced
a potent and selective CHOP inducer (AC<sub>50</sub> = 0.8 μM;
XBP1 > 80 μM), which was efficacious in both mouse embryonic
fibroblast cells and a human oral squamous cell cancer cell line,
and demonstrated antiproliferative effects for multiple cancer cell
lines in the NCI-60 panel
Discovery of Small Molecule Kappa Opioid Receptor Agonist and Antagonist Chemotypes through a HTS and Hit Refinement Strategy
Herein we present the outcome of a high throughput screening
(HTS)
campaign-based strategy for the rapid identification and optimization
of selective and general chemotypes for both kappa (κ) opioid
receptor (KOR) activation and inhibition. In this program, we have
developed potent antagonists (IC<sub>50</sub> < 120 nM) or agonists
of high binding affinity (<i>K</i><sub>i</sub> < 3 nM).
In contrast to many important KOR ligands, the compounds presented
here are highly modular, readily synthesized, and, in most cases,
achiral. The four new chemotypes hold promise for further development
into chemical tools for studying the KOR or as potential therapeutic
lead candidates
Discovery of ML314, a Brain Penetrant Nonpeptidic β‑Arrestin Biased Agonist of the Neurotensin NTR1 Receptor
The neurotensin 1 receptor (NTR1) is an important therapeutic target
for a range of disease states including addiction. A high-throughput
screening campaign, followed by medicinal chemistry optimization,
led to the discovery of a nonpeptidic β-arrestin biased agonist
for NTR1. The lead compound, 2-cyclopropyl-6,7-dimethoxy-4-(4-(2-methoxyphenyl)-piperazin-1-yl)quinazoline, <b>32</b> (ML314), exhibits full agonist behavior against NTR1 (EC<sub>50</sub> = 2.0 μM) in the primary assay and selectivity against
NTR2. The effect of <b>32</b> is blocked by the NTR1 antagonist
SR142948A in a dose-dependent manner. Unlike peptide-based NTR1 agonists,
compound <b>32</b> has no significant response in a Ca<sup>2+</sup> mobilization assay and is thus a biased agonist that activates the
β-arrestin pathway rather than the traditional G<sub><i>q</i></sub> coupled pathway. This bias has distinct biochemical
and functional consequences that may lead to physiological advantages.
Compound <b>32</b> displays good brain penetration in rodents,
and studies examining its in vivo properties are underway