Chemical Genetics Reveals an RGS/G-Protein Role in the Action of a Compound

Abstract

We report here on a chemical genetic screen designed to address the mechanism of action of a small molecule. Small molecules that were active in models of urinary incontinence were tested on the nematode Caenorhabditis elegans, and the resulting phenotypes were used as readouts in a genetic screen to identify possible molecular targets. The mutations giving resistance to compound were found to affect members of the RGS protein/G-protein complex. Studies in mammalian systems confirmed that the small molecules inhibit muscarinic G-protein coupled receptor (GPCR) signaling involving G-αq (G-protein alpha subunit). Our studies suggest that the small molecules act at the level of the RGS/G-αq signaling complex, and define new mutations in both RGS and G-αq, including a unique hypo-adapation allele of G-αq. These findings suggest that therapeutics targeted to downstream components of GPCR signaling may be effective for treatment of diseases involving inappropriate receptor activation.

CCG-1423: a small-molecule inhibitor of RhoA transcriptional signaling

“…However, there is a strong body of evidence supporting efforts to disrupt signaling by oncogenic GTPases, such as ras and Rho family members. These include blockade of critical lipid modifications by farnesyltransferase and geranylgeranyltransferase inhibitors, statins, and bisphosphonates (34). Inhibitors of Rho kinase have also been evaluated in cancer models (35,37).…”

“…This lipid modification is necessary for membrane localization and function of the activated Rho proteins. The most widely used inhibitors of this modification include farnesyltransferase and geranylgeranyltransferase inhibitors and the cholesterol-lowering statin drugs (34). However, these compounds are not specific for the Rho family of small GTPases so their effects are difficult to interpret mechanistically.…”

Evolutionary conservation of drug action on lipoprotein metabolism-related targets

“…All of these mechanisms could also be relevant in C. elegans and thus are potential CHGN005 targets. The multiplicity of mechanisms that are involved in controlling the levels of secreted apoB suggests that a reasonable way to identify the mechanism underlying the action of CHGN005 or any other compound that is active in C. elegans might be the use of C. elegans molecular genetics, an approach that has been successful in the past (2,28,(48)(49)(50)(51)(52).…”

Chemical genetics: Reshaping biology through chemistry

“…Mutant TOR protein unable to bind rapamycin-FKBP12, however, is dominant in conferring resistance against rapamycin. fication already two decades ago, e.g., with the identification of tubulin as a target of nematocides (Driscoll et al, 1989) and was also useful for the characterization of the target proteins of drug candidates (Fitzgerald et al, 2006) and drugs like Fluoxetine ͑Prozac ® ͒ (Choy and Thomas, 1999). A recent example of the powerful combination of phenotypic screen and genetics possible in this system is provided by the group of Peter Roy who set up a phenotype-based screen to identify calcium channel inhibitors in the nematode Caenorhabditis elegans (Kwok et al, 2006).…”