ABSTRACT
S-acylation is a reversible posttranslational protein modification consisting of attachment of a fatty acid to a cysteine via a thioester bond. Research over the last few years has shown that a variety of different fatty acids, such as palmitic acid (C16:0), stearate (C18:0), or oleate (C18:1), are used in cells to S-acylate proteins. We recently showed that GNAI proteins can be acylated on a single residue, Cys3, with either C16:0 or C18:1, and that the relative proportion of acylation with these fatty acids depends on the level of the respective fatty acid in the cell's environment. This has functional consequences for GNAI proteins, with the identity of the acylating fatty acid affecting the subcellular localization of GNAIs. Unclear is whether this competitive acylation is specific to GNAI proteins or a more general phenomenon in the proteome. We perform here a proteome screen to identify proteins acylated with different fatty acids. We identify 218 proteins acylated with C16:0 and 308 proteins acylated with C18-lipids, thereby uncovering novel targets of acylation. We find that most proteins that can be acylated by C16:0 can also be acylated with C18-fatty acids. For proteins with more than one acylation site, we find that this competitive acylation occurs on each individual cysteine residue. This raises the possibility that the function of many different proteins can be regulated by the lipid environment via differential S-acylation.
Subject(s)
Cysteine , Palmitic Acid , Proteome , Stearic Acids , Acylation , Cysteine/metabolism , Palmitic Acid/metabolism , Proteome/metabolism , HEK293 Cells , HeLa Cells , Humans , Stearic Acids/metabolismABSTRACT
Scalable asymmetric syntheses of two kallikrein-related protease 6 (KLK6) inhibitors are reported. The inhibitors are assembled by linking enantiomerically enriched fragments via amide bond formation, followed by conversion of a cyano group to an amidine. One fragment, an amine, was prepared using the Ellman auxiliary, and a lack of clarity in the literature regarding the stereochemical outcome of this reaction was solved via X-ray crystallographic analysis of two derivatives. Complexes of the inhibitors bound to human KLK6 were solved by X-ray crystallography, revealing the binding poses.
ABSTRACT
[This corrects the article DOI: 10.1039/D2RA04670A.].
ABSTRACT
Kallikrein-related peptidase 6 (KLK6) is a secreted serine protease that belongs to the family of tissue kallikreins (KLKs). Many KLKs are investigated as potential biomarkers for cancer as well as therapeutic drug targets for a number of pathologies. KLK6, in particular, has been implicated in neurodegenerative diseases and cancer, but target validation has been hampered by a lack of selective inhibitors. This work introduces a class of depsipeptidic KLK6 inhibitors, discovered via high-throughput screening, which were found to function as substrate mimics that transiently acylate the catalytic serine of KLK6. Detailed structure-activity relationship studies, aided by in silico modeling, uncovered strict structural requirements for potency, stability, and acyl-enzyme complex half-life. An optimized scaffold, DKFZ-251, demonstrated good selectivity for KLK6 compared to other KLKs, and on-target activity in a cellular assay. Moreover, DKFZ-633, an inhibitor-derived activity-based probe, could be used to pull down active endogenous KLK6.
Subject(s)
Cell Proliferation/drug effects , Depsipeptides/pharmacology , Enzyme Inhibitors/pharmacology , Kallikreins/antagonists & inhibitors , Neoplasms/drug therapy , Depsipeptides/chemistry , Enzyme Inhibitors/chemistry , High-Throughput Screening Assays , Humans , Models, Molecular , Neoplasms/enzymology , Neoplasms/pathology , Protein Conformation , Structure-Activity Relationship , Tumor Cells, CulturedABSTRACT
The use of small molecules to regulate cellular levels of specific proteins is poised to become a powerful technique in the coming years. Critical to the success of any project utilizing such an approach will be the ability to synthesize libraries of candidate small molecules for testing in cellular systems. Herein, we describe a practical synthesis of a phthalimide-based scaffold, which can be easily diversified to make Cereblon-targeting PROTACs. We demonstrate the effectiveness of this approach by synthesizing a 'PROTAC toolbox' of four amines which can be coupled to inhibitors in a straightforward manner.
