Novel Two-face Bim Mimics Created By The Hybridization Of Drug-Divided Building Blocks And A Fragment Deconstructed From A Known Two-Face BH3Mimetic

Bcl-2family proteins are a class of central arbiters of apoptosis. A balance between anti-apoptotic, pro-apoptotic members and BH3-only proteins dictates a cell’s fate. BH3domain of the BH3-only proteins mediate the PPIs between anti-apoptotic and pro-apoptotic members by the inserting into a hydrophobic groove on the surface of anti-apoptotic proteins. As a member of BH3-only proteins, Bim is a nonselective BH3-only protein that can neutralize both arms of the anti-apoptotic Bcl-2family, Bcl-2and Mcl-1proteins. It has been demonstrated that small molecules, which designed to mimic Bim to inhibit protein-protein interactions (PPIs) between anti-apoptotic and pro-apoptotic members, are practicable to promote apoptosis in cancer cells by antagonizing two classes of anti-apoptotic members.Researchers has demonstrated that the hotspot residues of Bim distribute on two faces of the a-helix by alanine scanning mutagenesis. Several Bim BH3mimics which can target Bcl-2family proteins to induce apoptosis such as ABT-737and a-helix mimicry terphenyl scaffolds have been reported. But none of them can mimic D67, the only key hydrophilic residue in Bim located on the opposite of the other four hydrophobic residues. In other words, each of them can not mimic the key binding residues located on two faces of the Bim BH3a-helix. Besides, the reported binding modes of R-(-)-Gossypol are inconsistent. So far, design of two-face Bim BH3mimetics to target PPIs is still considered one of the most challenge tasks in modern biochemistry and chemical biology.Most recently, our group has reported a small molecule two-face Bim BH3mimetic, compound14, which exhibits good affinities toward Mcl-1(Ki=13nM) and Bcl-2(Ki=24nM). The2D1H-15N HSQC NMR results demonstrated that polyphenols of compound14mimics D67forms hydrogen bonds with R263, the sulfur atom occupies the opposite p3pocket and the isopropyl can mimic L62in Bim.Besides, to design some new drugs, the hybridization of a successful fragment with the drug-derived building blocks has been put forward by some researchers. Recently, the first picomolar-range Qo site inhibitor of the cytochrome bcl complex has been yielded by linking a drug-derived building block, MOA pharmacophore, with a trifluoromethyl-quinoline fragment. And now, the want to use this method to design the new series of small molecule two-face Bim BH3mimetics.In this article, we use the inverse process of FBDD and deconstruct the known two-face Bim BH3a-helix mimetic, compound14. The D67mimicking polyphenols group of14was yielded as the starting points for the design of new two-face a-helix mimetics. Besides, as illustrated by the crystal structure of the Bim/Mcl-1complex, the carboxy of D67is attached to a sp3-hybridized carbon atom, and it can rotate freely around the central carbon-carbon single bond in room-temperature solution. To get a better simulation of Bim, and to develop new scaffold for two-face Bim BH3mimetics, we got a series of new scaffolds by linking the polyphenols fragment, which was deconstructed from14, with a small library of building blocks extracted from known drugs by a rotatable. single bond. The docking methods, which have been demonstrated to be ideally suitable for analyzing the binding model of small, inflexible fragments with target protein, were performed to determine the candidates for our experiments.6a was finally determined for our future study.Compound6a was obtained, which can bind to Bcl-2and Mcl-1in our FPA and mimic the key binding residues,165and L62. Based on it, compound6d was obtained, which can bind to Bcl-2and Mcl-1with Kivalues of0.607μM and0.127μM respectively and mimic the key binding residues located on two faces of Bim BH3a-helix in the interaction with Bcl-2and Mcl-1. Besides, compound6d can effectively induce apoptosis in a dose-dependent manner in the U937cells (IC50=7.3μM), K562cells (IC50=13.5μM) and KU812cells (IC50=14.1μM). Taken together, our data indicate that compound6d is a potent, cell-permeable, two-face Bim BH3a-Helix mimic. We expect these results could provide some fundamental insights into the future design and development of Bim BH3a-helix mimetics.