Identification of alcohol-binding site(s) in proteins using diazirine-based photoaffinity labeling and mass spectrometry

Identification of potential targets against SARS-CoV-2 of antiviral drugs based on photoaffinity probes

Facing the sudden outbreak of coronavirus disease 2019 (COVID-19), it is extremely urgent to develop effective antiviral drugs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Drug repurposing is a promising strategy for the treatment of COVID-19. To identify the precise target protein of marketed medicines, we initiate a chemical biological program to identify precise target of potential antivirus drugs. In this study, two types of recombinant human coronavirus SARS-CoV-2 RdRp protein capturing probes with various photoaffinity labeling units were designed and synthesized based on the structure of FDA-approved drugs stavudine, remdesivir, acyclovir, and aladenosine. Fortunately, it was found that one novel photoaffinity probe, RD-1, could diaplayed good affinity with SARS-CoV-2 RdRp around the residue ARG_553. In addition, RD-1 probe also exhibited potent inhibitory activity against 3CLpro protease. Taken together, our findings will elucidate the structural basis for the efficacy of marketed drugs, and explore a rapid and efficient strategy of drug repurposing based on the identification of new targets. Moreover, these results could also provide a scientific basis for the clinical application of marketed drugs.

Utilization of Photoaffinity Labeling to Investigate Binding of Microtubule Stabilizing Agents to P-Glycoprotein and β-Tubulin

Photoaffinity labeling approaches have historically been used in pharmacology to identify molecular targets. This methodology has played a pivotal role in identifying drug-binding domains and searching for novel compounds that may interact at these domains. In this review we focus on studies of microtubule stabilizing agents of natural product origin, specifically taxol (paclitaxel). Taxol and other microtubule interacting agents bind to both P-glycoprotein (ABCB1), a drug efflux pump that reduces intracellular drug accumulation, and the tubulin/microtubule system. Both binding relationships modulate drug efficacy and are of immense interest to basic and translational scientists, primarily because of their association with drug resistance for this class of molecules. We present this body of work and acknowledge its value as fundamental to understanding the mechanisms of taxol and elucidation of the taxol pharmacophore. Furthermore, we highlight the ability to multiplex photoaffinity approaches with other technologies to further enhance our understanding of pharmacologic interactions at an atomic level. Thus, photoaffinity approaches offer a relatively inexpensive and robust technique that will continue to play an important role in drug discovery for the foreseeable future.

How Physiologic Targets Can Be Distinguished from Drug-Binding Proteins

In clinical trials, some drugs owe their effectiveness to off-target activity. This and other observations raise a possibility that many studies identifying targets of drugs are incomplete. If off-target proteins are pharmacologically important, it will be worthwhile to identify them early in the development process to gain a better understanding of the molecular basis of drug action. Herein, we outline a multidisciplinary strategy for systematic identification of physiologic targets of drugs in cells. A drug-binding protein whose genetic disruption yields very similar molecular effects as treatment of cells with the drug may be defined as a physiologic target of the drug. For a drug developed with a rational approach, it is desirable to verify experimentally that a protein used for hit optimization in vitro remains the sole polypeptide recognized by the drug in a cell. SIGNIFICANCE STATEMENT: A body of evidence indicates that inactivation of many drug-binding proteins may not cause the pharmacological effects triggered by the drugs. A multidisciplinary cell-based approach can be of great value in identifying the physiologic targets of drugs, including those developed with target-based strategies.