TGR5 agonists are potential therapeutics for a variety of conditions including type 2 diabetes, obesity, and inflammatory bowel disease. After screening a library of chenodeoxycholic acid (CDCA) derivatives, it was determined that a range of modifications could be made to the acid moiety of CDCA which significantly increased TGR5 agonist potency. Surprisingly, methylation of the 7-hydroxyl of CDCA led to a further dramatic increase in potency, allowing the identification of 5.6 nM TGR5 agonist 17.
Summary
The mechanisms by which cancer cell-intrinsic CYP monooxygenases promote tumor progression are largely unknown. CYP3A4 was unexpectedly associated with breast cancer mitochondria and synthesized arachidonic acid (AA)-derived epoxyeicosatrienoic acids (EETs), which promoted the electron transport chain/respiration and inhibited AMPKα. CYP3A4 knockdown activated AMPKα, promoted autophagy, and prevented mammary tumor formation. The diabetes drug metformin inhibited CYP3A4-mediated EET biosynthesis and depleted cancer cell-intrinsic EETs. Metformin bound to the active site heme of CYP3A4 in a co-crystal structure, establishing CYP3A4 as a biguanide target. Structure-based design led to discovery of N1-hexyl-N5-benzyl-biguanide (HBB), which bound to the CYP3A4 heme with higher affinity than metformin. HBB potently and specifically inhibited CYP3A4 AA epoxygenase activity. HBB also inhibited growth of established ER+ mammary tumors and suppressed intratumoral mTOR. CYP3A4 AA epoxygenase inhibition by biguanides thus demonstrates convergence between eicosanoid activity in mitochondria and biguanide action in cancer, opening a new avenue for cancer drug discovery.
β-Lactam antibiotics comprise one of the most widely
used
therapeutic classes to combat bacterial infections. This general scaffold
has long been known to inhibit bacterial cell wall biosynthesis by
inactivating penicillin-binding proteins (PBPs); however, bacterial
resistance to β-lactams is now widespread, and new strategies
are urgently needed to target PBPs and other proteins involved in
bacterial cell wall formation. A key requirement in the identification
of strategies to overcome resistance is a deeper understanding of
the roles of the PBPs and their associated proteins during cell growth
and division, such as can be obtained with the use of selective chemical
probes. Probe development has typically depended upon known PBP inhibitors,
which have historically been thought to require a negatively charged
moiety that mimics the C-terminus of the PBP natural peptidoglycan
substrate, d-Ala-d-Ala. However, we have identified
a new class of β-lactone-containing molecules that interact
with PBPs, often in an isoform-specific manner, and do not incorporate
this C-terminal mimetic. Here, we report a series of structural biology
experiments and molecular dynamics simulations that we utilized to
evaluate specific binding modes of this novel PBP inhibitor class.
In this work, we obtained <2 Å resolution X-ray structures
of four β-lactone probes bound to PBP1b from Streptococcus
pneumoniae. Despite their diverging recognition modes beyond
the site of covalent modification, these four probes all efficiently
labeled PBP1b, as well as other PBPs from S. pneumoniae. From these structures, we analyzed protein–ligand
interactions and characterized the β-lactone-bound active sites
using in silico mutagenesis and molecular dynamics.
Our approach has clarified the dynamic interaction profile in this
series of ligands, expanding the understanding of PBP inhibitor binding.
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