Selective Covalent Targeting of Anti‐apoptotic BFL‐1 by a Sulfonium‐Tethered Peptide

Abstract

Anti-apoptotic B cell lymphoma 2 (BCL-2) family proteins are proven targets for human cancers. Targeting the BH3-binding pockets of these anti-apoptotic proteins could reactivate apoptosis in BCL-2-depedent cancers. BFL-1 is a BCL-2 family protein overexpressed in various chemoresistant cancers. A unique cysteine at the binding interface of the BH3 and BFL-1 was previously proven to be an intriguing targeting site to irreversibly inhibit BFL-1 functions with stabilized cyclic peptide bearing a covalent warhead. Recently, we developed a sulfonium-tethered peptide cyclization strategy to construct peptide ligands that could selectively and efficiently react with the cysteine(s) of target proteins near the interacting interface. Using this method, we constructed a BFL-1 peptide inhibitor, B4-MC, that could selectively conjugate with BFL-1 both in vitro and in cell. B4-MC showed good cellular uptake, colocalized with BFL-1 on mitochondria, and showed obvious growth inhibition of BFL-1 over-expressed cancer cell lines.

The role of BCL-2 family proteins in regulating apoptosis and cancer therapy

“…BFL-1 includes highly conserved BH1 and BH2 domains and conserved BH3 and BH4 and can bond to proapoptotic proteins like NOXA and BID ( 44 ). It locates in mitochondria and performs anti-apoptotic functions ( 45 ). In addition, the proliferation of macrophages and mast cells in the allergic reaction ( 46 ) was promoted by BFL-1 binding to the Beclin-1 protein.…”

Design and Evaluation of a Novel Peptide–Drug Conjugate Covalently Targeting SARS-CoV-2 Papain-like Protease

“… 35 When such a peptide recognizes its target and if the protein has a Cys in the vicinity of the interacting interface, the peptide would bind to the protein with high selectivity and efficiency. 36 Based on this method, we first designed a series of sulfonium-tethered peptides to target SARS-CoV-2 PLpro, in which the main catalytic amino acid is the C111 residue. The PLpro recognized a conserved sequence with different substrates including the tetrapeptide LXGG motif found in between viral proteins nsp1 and nsp2, nsp2 and nsp3, and nsp3 and nsp4 for cleavage of the viral polypeptide.…”

“…In our previous study, we reported a unique bio-orthogonal reaction in which we tethered a peptide between Cys and Met with a newly formed sulfonium center . When such a peptide recognizes its target and if the protein has a Cys in the vicinity of the interacting interface, the peptide would bind to the protein with high selectivity and efficiency . Based on this method, we first designed a series of sulfonium-tethered peptides to target SARS-CoV-2 PLpro, in which the main catalytic amino acid is the C111 residue.…”

Chemical modification of proteins – challenges and trends at the start of the 2020s

“…The peptide did not conjugate to other Cys-containing proteins like PDZ, Bcl-2, MgrA, and sortase A. 104…”