Identification and characterization of a potent and biologically-active PDE4/7 inhibitor via fission yeast-based assays

We previously constructed a collection of fission yeast strains that express various mammalian cyclic nucleotide phosphodiesterases (PDEs) and developed a cell-based high throughput screen (HTS) for small molecule PDE inhibitors. Here we describe a compound, BC54, that is a selective inhibitor of enzymes from the cAMP-specific PDE4 and PDE7 families. Consistent with the biological effect of other PDE4 and PDE7 inhibitors, BC54 displays potent anti-inflammatory properties and is superior to a combination of rolipram (a PDE4 inhibitor) and BRL50481 (a PDE7A inhibitor) for inducing apoptosis in chronic lymphocytic leukemia (CLL) cells. We further exploited PKA-regulated growth phenotypes in fission yeast to isolate two mutant alleles of the human PDE4B2 gene that encode enzymes possessing single amino acid changes that confer partial resistance to BC54. We confirm this resistance to both BC54 and rolipram via yeast-based assays and, for PDE4B2T407A, in vitro enzyme assays. Thus, we are able to use this system for both chemical screens to identify biologically-active PDE inhibitors and molecular genetic studies to characterize the interaction of these molecules with their target enzymes. Based on its potency, selectivity, and effectiveness in cell culture, BC54 should be a useful tool to study biological processes regulated by PDE4 and PDE7 enzymes. [Display omitted] •Compound BC54 was identified in parallel cell-based PDE4 and PDE7 inhibitor HTSs.•BC54 shows potent activity in TNFα and IL-2 anti-inflammatory assays.•BC54 outperforms rolipram (PDE4) plus BRL50481 (PDE7A) in a CLL apoptosis assay.•A plasmid-based screen identified BC54-resistant allele of PDE4B2.•The PDE4B2T407A protein is partially resistant to both BC54 and rolipram.