Small-Molecule Protein-Protein Interaction Inhibitor of Oncogenic Rho Signaling

Abstract

Uncontrolled activation of Rho signaling by RhoGEFs, in particular AKAP13 (Lbc) and its close homologs, is implicated in a number of human tumors with poor prognosis and resistance to therapy. Structure predictions and alanine scanning mutagenesis of Lbc identified a circumscribed hot region for RhoA recognition and activation. Virtual screening targeting that region led to the discovery of an inhibitor of Lbc-RhoA interaction inside cells. By interacting with the DH domain, the compound inhibits the catalytic activity of Lbc, halts cellular responses to activation of oncogenic Lbc pathways, and reverses a number of prostate cancer cell phenotypes such as proliferation, migration, and invasiveness. This study provides insights into the structural determinants of Lbc-RhoA recognition. This is a successful example of structure-based discovery of a small protein-protein interaction inhibitor able to halt oncogenic Rho signaling in cancer cells with therapeutic implications.

The Role of Cyclic AMP Signaling in Cardiac Fibrosis

“…Such protein interfaces could be targeted by peptides or small molecule compounds to inhibit cardiac fibrosis. In this respect, two studies recently identified small molecules inhibiting the ability of AKAP13 to bind and activate RhoA [155,174]. It will be crucial to determine whether such molecules can efficiently inhibit the pro-fibrotic function of the AKAP-Lbc/RhoA pathway both in vitro and in vivo.…”

“…This anchoring protein coordinates multiple signaling enzymes, such as PKA, protein kinase Cη (PKCη), protein kinase D1 (PKD1), PDE4D, phosphatases, and various MAPKs involved in the cardiac adaptation to stress and damage [148][149][150][151][152][153][154]. Unlike other AKAPs, AKAP13 also contains tandem Dbl homology (DH) and pleckstrin homology (PH) domains, which confer to the protein GEF activity towards RhoA and RhoC [146,155]. AKAP13 RhoGEF activity can be regulated bidirectionally by activating or inhibitory signals.…”

RhoGEFs as therapeutic targets

“…Immune related disorders, Alzheimer's disease (Nishikimi et al, 2012) LARG Y16 Cell-free assay, Cell culture Accute myeloid Leykemia (Shang et al, 2013) Lbc A13 Cell-free assay, Cell culture Various cancers (Diviani et al, 2016) (a) The inhibitor of Dock5 (CAS 54129-15-6) should not be mistaken for the inhibitor of the protein arginine methyltransferase PRMT1 (CAS 1229236-78) and for the non-peptide selective AT2 receptor agonist M24 (CAS 477775-14-7), which were also named C21.…”

“…Y16 does not bind to Lbc, another RGS-RhoGEFs closely related to LARG. A model for the RhoA-Lbc complex was built by structural analogy after the RhoA-LARG complex and the aminoacids involved in the interaction between the RhoA and Lbc were deduced (Diviani et al, 2016). A virtual screening on the ZINC database highlighted 30 compounds likely to interfere with the formation of the RhoA-Lbc complex.…”

A structural study of the complex between neuroepithelial cell transforming gene 1 (Net1) and RhoA reveals a potential anticancer drug hot spot

“…approaches have led to molecules with severe selectivity issues (24). From the purely molecular point of view, a few key studies have described the relationship between RhoA and GEF11 or GEF12 (25)(26)(27)(28), but little is known regarding the interface between RhoA and Net1.…”