"Analysis of Cell Type–Dependent Inhibition of Histone Deacetylases In Situ Using Photoreactive Probes: Discovery of Novel Potential Targets to Treat Acute Myeloid Leukemia"
The current design of histone deacetylase inhibitors (HDAC(i)) in medicinal chemistry is typically driven by biochemical methods using recombinant HDAC isoforms or analyzing substrates thought to be specific for a particular HDAC isoform in cell lysates, which often do not correlate with phenotypic changes in cells. Our recent publications show that HDAC target engagement determined using these methods does not directly translate to intact live cells in culture and tissues and, hence is unlikely to translate to in vivo settings. The substrate specificity and enzymatic activity of HDACs in vivo are modulated by forming protein–protein deacetylase complexes and post-translation modifications, whereas HDAC biological function may switch between enzymatic and scaffolding. We demonstrated phosphorylation of HDAC3 not only affects its enzymatic activity, it also increases binding of a photoreactive HDAC(i) TH1143 to HDAC3 in a cell type–dependent manner.For instance, engagement of HDACs can range from nonexistent to very high despite comparable abundance of HDAC proteins. We and others found that the HDAC deacetylase complex binding partners can affect HDAC catalytic activity by limiting access of small molecule HDAC(i)s and are often dysregulated in cancer. Understanding of protein–protein interaction between HDAC8 and its putative binding partners remains limited, making development of HDAC8(i)s an even more challenging task. To address this, we developed a set of novel photoreactive probes and extensively validated their ability to report HDAC isoform target engagement in intact live cells and tissues.
Password for this Zoom event: seminar