Characterization of Calmodulin and CHK2 inhibitors for the treatment of Diamond B

Boston Children'S Hospital, Boston MA

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Abstract

DESCRIPTION (provided by applicant): Ribosomal protein mutations are found in many diseases, including Diamond Blackfan anemia (DBA), where defective erythropoiesis, craniofacial abnormalities and increased cancer risk are major complications. Ribosomal protein mutations cause p53 activation through accumulation of free ribosomal proteins that bind and sequester MDM2, the negative regulator of p53. Current DBA treatments are ineffective and associated with toxicity. To find effective therapies, we performed an in vivo chemical screen in a zebrafish DBA model and found that inhibitors of calmodulin (CaM), and CaM-dependent kinase CHK2, block p53 activity and rescue red blood cell development. Many CaM inhibitors are FDA approved antipsychotics, but cross the blood brain barrier (BBB), and have irreversible, negative side effects. Our goals are to elucidate the mechanism by which CaM and CHK2 inhibitors block p53 nuclear activation, and to find CaM or CHK2 inhibitors that do not cross the BBB, and can therefore be used in clinical trials for DBA patients. DBA cell culture models will be used do mutational analysis to determine the mechanism of CaM inhibition on p53 nuclear accumulation. Additionally, a zebrafish DBA model will be used to study the effects of ribosomal protein deficiency and the role of p53 on translation, in vivo. To find compounds that will not cross the BBB, we will use a novel chemical scaffold approach to generate 400 new CaM inhibitors to be tested for BBB permeability using a fluorescence confocal microscopy screening approach. Select chemicals will then be tested for erythroid rescue in zebrafish and in human/mammalian DBA models. This work will identify potential compounds to further our understanding of ribosome-p53 biology and develop for clinical trials for ribosomal protein disorders.