Small molecule phenotypic screen using a MEF2/ HDAC5 mammalian two-hybrid assay

Abstract

MEF2 is a member of a family of transcription factors necessary for myogenesis. MEF2 appears to be a nodal point in the regulation of myocardial hypertrophy, which is characterized by the expression of many MEF2-dependent genes. In the normal adult heart MEF2 signaling is repressed due to its interaction with class II histone deacetylases 4 and 5 (HDAC4 and HDAC5). Prohypertrophic agents such as CaMKI or CaMKIV cause the dissociation of HDAC4 or HDAC5 from MEF2, a process linked to phosphorylation of HDAC4 or HDAC5 and their nuclear export. Dissociation of HDAC4 or HDAC5 from MEF2 is therefore a potential switch regulating the myocardial hypertrophic response and a potential novel drug discovery target for cardiac hypertrophy and failure. We developed a two-hybrid assay that reports the level of interaction between MEF2 and HDAC5. We used this assay, in a chemical genetic approach, to screen a diverse library of small molecules for compounds that potentially could enhance the interaction between MEF2 and HDAC5. We identified structurally diverse small molecules that cause elevation of the 2-hybrid signal. Some of these molecules are potent inhibitors of in vitro hypertrophic markers in neonatal rat ventricular cardiac myocytes (NRVM). In addition, such molecules inhibited nuclear export of HDAC5 in NRVM, reduced MEF2-dependent gene expression, and inhibited myogenic fusion of C2 myoblasts. Further characterization of these compounds and understanding their mechanism of action, along with additional screening could help elucidate the signaling events leading to cardiac hypertrophy and could serve as starting points in novel drug discovery efforts for compounds with antihypertrophic activity.