Y16 is an inhibitor of G-protein-coupled Rho GEFs; works synergistically with Rhosin/G04 in inhibiting LARG-RhoA interaction, RhoA activation, and RhoA-mediated signaling functions.IC50 value: Target: RhoA inhibitorY16 binds to this catalytic fragment of LARG with a Kd of ～76 ± 8 nM. Y16 was able to inhibit the GDP dissociation from RhoA catalyzed by LARG dose dependently without affecting the GEF reactions of Rac1 and Cdc42 catalyzed by TrioN and Intersectin, respectively. The N983A mutant lost the binding ability to Y16 with a Kd >500 μM, whereas the K979A and E982A mutants showed a reduced affinity with Kd values of 0.47 and 2.1 μM, respectively. At 2.5 μM each, Rhosin and Y16 inhibited ～50% RhoA-GTP content, and at 5 μM each ～80% RhoA-GTP stimulated by serum, which were much more potent than the effect of Rhosin/G04 or Y16 acting alone (～80% inhibition at 30 μM). Even under a higher concentration of Y16 and Rhosin/G04 combination (50 μM each) when endogenous RhoA-GTP content was effectively suppressed, no effect on Rac1-GTP or Cdc42-GTP content in cells was observed. Although Rhosin/G04 or Y16 administration alone caused ～50% inhibition of RhoA activity at 10 μM, combined Rhosin/G04 and Y16 reached 70% inhibition of RhoA-GTP or the downstream p-MLC when each was at 2.5 μM.

[1]. Shang X, et al. Small-molecule inhibitors targeting G-protein-coupled Rho guanine nucleotide exchange factors. Proc Natl Acad Sci U S A. 2013 Feb 19;110(8):3155-60.