Discovery of Novel Allosteric Modulators of the Muscarinic Receptor M5: SAR with Acetylcholine
Screening Center Name & PI: Vanderbilt Screening Center for GPCRs, Ion Channels and Transporters, C. David Weaver ..more
BioActive Compounds: 72
Assigned Assay Grant Number: MH077606-1
Screening Center Name & PI: Vanderbilt Screening Center for GPCRs, Ion Channels and Transporters, C. David Weaver
Chemistry Center Name & PI: Vanderbilt Specialized Chemistry Center for Accelerated Probe Development, Craig W. Lindsley
Assay Submitter & Institution: P. Jeffrey Conn, Vanderbilt University
Muscarinic acetylcholine receptors are family A GPCRs comprised of five distinct mammalian subtypes (mAChR1-5 or M1-M5), which are expressed differentially throughout the body and play an important role in a variety of physiological processes. Among the mAChRs, M1 and M4 have been historically considered attractive targets for small molecule treatments of numerous CNS disorders such as Alzheimer's disease and schizophrenia due to their respective localization and involvement in regulation of certain aspects of learning, memory, sleep, motor control, reward, and pain, among others. However, discovery of subtype-selective small molecules has proven highly difficult due to the conservation of the orthosteric binding-site across the mAChRs. This has contributed to the failure of muscarinic agonists in clinical trials and has also hampered pharmacological investigation into the role(s) of each mAChR in basic neurobiology.
Among the mAChRs, M5 has remained perhaps the most challenging to investigate pharmacologically due in part to its extremely low expression level and a complete lack of M5-selective ligands. Interestingly, studies using M5-KO mice suggest that M5 is the sole mediator of acetylcholine-induced cerebrovasodilation, which has led to the hypothesis that an M5 activator would have therapeutic efficacy in treatment of cerebrovascular dementias and ischemic stroke. Furthermore, M5-KO mice show dramatically reduced reward responses to drugs of abuse, consistent with its putative localization on midbrain dopaminergic neurons of the nigrostriatal and mesolimbic pathways. This suggests that M5 antagonism or negative modulation may have utility in treatment of illicit drug addiction and withdrawal. Despite these and other related findings from M5-KO mice, there remains a strong need for small molecule tools to probe M5 function and test M5-related hypotheses in order to advance the state of the mAChR research field and provide critical proof-of-concept studies for drug discovery aims.
Compounds were tested at 30uM (fixed) in the presence of a submaximal concentration of acetylcholine (ACh) (~EC10) and evaluated for their ability to elevate the response to ACh in rM1- or hM5-expressing CHO cells using the primary calcium assay.
Compounds eliciting a response less than approximately 40 %ACh Max in either or both cell line were scored as inactive (0). Compounds eliciting a response between approximately 40 and 60 %ACh Max in either or both cell lines were scored as partially active (50). Compounds eliciting a response greater than approximately 60 %ACh Max in either or both cell lines were considered fully active (100).
** Test Concentration.
Data Table (Concise)