The Notch inhibitor cowanin accelerates nicastrin degradation

Abstract Aberrant activation of Notch signaling contributes to the pathogenesis of several different types of cancer, and Notch pathway inhibitors may have significant therapeutic potential. Using a unique cell-based assay system, we isolated twelve compounds, including one new natural product from Garcinia speciosa, that inhibit the Notch signaling pathway. HES1 and HES5 are target genes of the Notch cascade, and compound 2, referred to as cowanin, decreased the protein levels of HES1 and HES5 in assay cells. Furthermore, cowanin (2) showed potent cytotoxicity against human leukemic HPB-ALL cells. The Notch signaling inhibitory activity of cowanin (2) is linked to the increased degradation of nicastrin, which is one of the components of the γ-secretase complex. To the best of our knowledge, this is the first example of a compound with Notch pathway inhibitory activity mediated by nicastrin degradation

The Notch Inhibitors Isolated from <i>Nerium indicum</i>

Notch signaling plays a crucial role in differentiation and cell maintenance, but once aberrantly activated, it contributes to cancer progression. Notch inhibitors were isolated from plant extracts and tested using an originally constructed cell-based assay system. We isolated eight compounds from <i>Nerium indicum</i> that showed inhibition of the Notch signaling pathway. <i>HES1</i> and <i>HES5</i> are target genes of the Notch signaling pathway, and oleandrin (<b>1</b>) decreased the protein levels of HES1 and HES5 in assay cells. Oleandrin (<b>1</b>) showed potent cytotoxicity against HPB-ALL cells and decreased HES1 and the Notch intracellular domain in these cells. The main mechanism of action of <b>1</b> appears to be inhibition of Notch signaling by acceleration of Notch intracellular domain degradation

Notch Inhibitors from <i>Calotropis gigantea</i> That Induce Neuronal Differentiation of Neural Stem Cells

Neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease occur due to loss of the structure and function of neurons. For the potential treatment of neurodegenerative diseases, accelerators of neuronal differentiation of neural stem cells (NSCs) have been focused on and a cell-based assay system for measuring Notch signaling pathway activity was constructed. Using this assay system, eight compounds isolated from <i>Calotropis gigantea</i> were identified as inhibitors of the Notch signaling pathway. <i>Hes1</i> and <i>Hes5</i> are target genes of the Notch signaling pathway, and compound <b>1</b>, called uscharin, decreased the protein levels of Hes1 and Hes5 in assay cells and MEB5 cells (mouse NSCs). Furthermore, uscharin (<b>1</b>) enhanced the differentiation of MEB5 cells into neurons. The mechanism of uscharin (<b>1</b>) for the Notch signaling inhibitory activity would be acceleration of the degradation of the Notch intracellular domain (NICD) in the MEB5 cells