T-448, a specific inhibitor of LSD1 enzyme activity, improves learning function without causing thrombocytopenia in mice.

Dysregulation of histone H3 lysine 4 (H3K4) methylation has been implicated in the pathogenesis of several neurodevelopmental disorders. Targeting lysine-specific demethylase 1 (LSD1), an H3K4 demethylase, is therefore a promising approach to treat these disorders. However, LSD1 forms complexes with cofactors including growth factor independent 1B (GFI1B), a critical regulator of hematopoietic differentiation. Known tranylcypromine-based irreversible LSD1 inhibitors bind to coenzyme flavin adenine dinucleotide (FAD) and disrupt the LSD1-GFI1B complex, which is associated with hematotoxicity such as thrombocytopenia, representing a major hurdle in the development of LSD1 inhibitors as therapeutic agents. To discover LSD1 inhibitors with potent epigenetic modulation and lower risk of hematotoxicity, we screened small molecules that enhance H3K4 methylation by the inhibition of LSD1 enzyme activity in primary cultured rat neurons but have little impact on LSD1-GFI1B complex in human TF-1a erythroblasts. Here we report the discovery of a specific inhibitor of LSD1 enzyme activity, T-448 (3-((1S,2R)-2-(cyclobutylamino)cyclopropyl)-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzamide fumarate). T-448 has minimal impact on the LSD1-GFI1B complex and a superior hematological safety profile in mice via the generation of a compact formyl-FAD adduct. T-448 increased brain H3K4 methylation and partially restored learning function in mice with NMDA receptor hypofunction. T-448-type LSD1 inhibitors with improved safety profiles may provide unique therapeutic approaches for central nervous system disorders associated with epigenetic dysregulation.

Proteasomal degradation of BRAHMA promotes Boron tolerance in Arabidopsis.

High levels of boron (B) induce DNA double-strand breaks (DSBs) in eukaryotes, including plants. Here we show a molecular pathway of high B-induced DSBs by characterizing Arabidopsis thaliana hypersensitive to excess boron mutants. Molecular analysis of the mutants revealed that degradation of a SWItch/Sucrose Non-Fermentable subunit, BRAHMA (BRM), by a 26S proteasome (26SP) with specific subunits is a key process for ameliorating high-B-induced DSBs. We also found that high-B treatment induces histone hyperacetylation, which increases susceptibility to DSBs. BRM binds to acetylated histone residues and opens chromatin. Accordingly, we propose that the 26SP limits chromatin opening by BRM in conjunction with histone hyperacetylation to maintain chromatin stability and avoid DSB formation under high-B conditions. Interestingly, a positive correlation between the extent of histone acetylation and DSB formation is evident in human cultured cells, suggesting that the mechanism of DSB induction is also valid in animals.

Novel anticancer agent, SQAP, binds to focal adhesion kinase and modulates its activity.

SQAP is a novel and promising anticancer agent that was obtained by structural modifications from a natural compound. SQAP inhibits angiogenesis in vivo resulting in increased hypoxia and reduced tumor volume. In this study, the mechanism by which SQAP modifies the tumor microenvironment was revealed through the application of a T7 phage display screening. This approach identified five SQAP-binding proteins including sterol carrier protein 2, multifunctional enzyme type 2, proteasomal ubiquitin receptor, UV excision repair protein and focal adhesion kinase (FAK). All the interactions were confirmed by surface plasmon resonance analysis. Since FAK plays an important role in cell turnover and angiogenesis, the influence of SQAP on FAK was the principal goal of this study. SQAP decreased FAK phosphorylation and cell migration in human umbilical vein endothelial cells and A549 cancer cells. These findings suggest that inhibition of FAK phosphorylation works as the mechanism for the anti-angiogenesis activity of SQAP.