Cdc42 protein is an essential GTPase that belongs to the Rho/Rac subfamily of Ras-like GTPases. These proteins act as molecular switches to activate downstream components of a biological pathway. CDC42 plays an important role in cytoskeleton organization, cell cycle progression, signal transduction, and vesicle trafficking. Particularly, Overactive Cdc42 implicates in the pathology of cancers, immune diseases, and neuronal disorders. Therefore, Cdc42 inhibitors would be useful in probing molecular pathways and could have therapeutic potential. In particular, ML141 is a potent inhibitor of filopodia formation, a process that is well known to be directly regulated by Cdc42. Crucially, ML141 (CID2950007) and its analog are the first small molecules that show specific inhibition of nucleotide-binding toward Cdc42 GTPase.

ML141 is a non-competitive and allosteric inhibitor of Cdc42

ML141 binds to an allosteric site of Cdc42 and inhibits Cdc42-related filopodia formation and cell migration. Moreover, ML141 binds to guanine nucleotide-bound Cdc42, induces the dissociation of the ligand, and locks the protein in an inactive conformation. Especially, ML141 inhibits filopodia formation in 3T3 cells after bradykinin treatment. ML141 clearly inhibits the migration of human ovarian carcinoma cell lines OVCA429 and SKOV3ip in a dose-dependent manner. Furthermore, ML141 inhibits Cdc42-regulated virus infection. Finally, the effect of ML141 is specific toward Cdc42 with no activity toward Ras and Rac1.

In vivo, researchers intracerebroventricularly injected C57Bl/6J mice with increasing doses of ML141. The result exhibits a sufficient dose causing a 40% decrease in its GTPase activity and mimicking the outcome in minor allele carriers. As a result, parallel suppression of the conserved brain CDC42 activity by ML141 causes acute anxiety.

To summarise, ML141 is a potent, selective and reversible non-competitive inhibitor of Cdc42 GTPase suitable for in vitro assays, with low micromolar potency and selectivity against other members of the Rho family of GTPases (Rac1, Rab2, Rab7).

Hong L, et al Characterization of a Cdc42 protein inhibitor and its use as a molecular probe. J Biol Chem. 2013 Mar 22;288(12):8531-43.