Targeting protein self-association in drug design

Protein self-association is a universal phenomenon essential for stability and molecular recognition. Disrupting constitutive homomers constitutes an original and emerging strategy in drug design. Inhibition of homomeric proteins can be achieved through direct complex disruption, subunit intercalation, or by promoting inactive oligomeric states. Targeting self-interaction grants several advantages over active site inhibition because of the stimulation of protein degradation, the enhancement of selectivity, substoichiometric inhibition, and by-pass of compensatory mechanisms. This new landscape in protein inhibition is driven by the development of biophysical and biochemical tools suited for the study of homomeric proteins, such as differential scanning fluorimetry (DSF), native mass spectrometry (MS), Förster resonance energy transfer (FRET) spectroscopy, 2D nuclear magnetic resonance (NMR), and X-ray crystallography. In this review, we discuss the different aspects of this new paradigm in drug design.

Ligand-based pharmacophore modeling of TNF-α to design novel inhibitors using virtual screening and molecular dynamics

Tumor necrosis factor-α (TNF-α) is one of the promising targets for treating inflammatory (Crohn disease, psoriasis, psoriatic arthritis, rheumatoid arthritis) and various other diseases. Commercially available TNF-α inhibitors are associated with several risks and limitations. In the present study, we have identified small TNF-α inhibitors using in silico approaches, namely pharmacophore modeling, virtual screening, molecular docking, molecular dynamics simulation and free binding energy calculations. The study yielded better and potent hits that bind to TNF-α with significant affinity. The best pharmacophore model generated using LigandScout has an efficient hit rate and Area Under the operating Curve. High throughput virtual screening of SPECS database molecules against crystal structure of TNF-α protein, coupled with physicochemical filtration, PAINS test. Virtual hit compounds used for molecular docking enabled the identification of 20 compounds with better binding energies when compared with previously known TNF-α inhibitors. MD simulation analysis on 20 virtual identified hits showed that ligand binding with TNF-α protein is stable and protein-ligand conformation remains unchanged. Further, 16 compounds passed ADMET analysis suggesting these identified hit compounds are suitable for designing a future class of potent TNF-α inhibitors.Communicated by Ramaswamy H. Sarma.

Tumor Necrosis Factor-α Trimer Disassembly and Inactivation via Peptide-Small Molecule Synergy

Aberrant signaling by tumor necrosis factor-α (TNFα) is associated with inflammatory diseases that can be treated with engineered proteins that inhibit binding of this cytokine to cell-surface receptors. Despite these clinical successes, there is considerable interest in the development of smaller antagonists of TNFα-receptor interactions. We describe a new 29-residue α/β-peptide, a molecule that contains three β-amino acid residues and three α-aminoisobutryic acid (Aib) residues, that displays potent inhibition of TNFα binding to TNFα receptor 1 (TNFR1) and rescues cells from TNFα-induced death. The complement of nonproteinogenic residues renders this α/β-peptide highly resistant to proteolysis, relative to all-α analogues. The mechanism of inhibitory action of the new 29-mer involves disruption of the trimeric TNFα quaternary structure, which prevents productive binding to TNFα receptors. Unexpectedly, we discovered that peptide-induced trimer disruption can be promoted by structurally diverse small molecules, including a detergent commonly used during selection procedures. The discovery of this synergistic effect provides a new context for understanding previous reports on peptidic antagonists of TNFα-receptor interactions and suggests new avenues for future efforts to block signaling via proteins with an active form that is oligomeric, including other members of the TNFα family.