Mutant Huntingtin‐Calmodulin Interaction: Potential Therapeutic Target for Huntington's Disease

Abstract

Huntington's disease (HD) is a neurodegenerative disorder caused by an autosomal dominant mutation in the huntingtin (htt) gene. Previous studies in our lab demonstrated that disrupting the binding of mutant huntingtin (mhtt) to calmodulin (CaM) had beneficial effects in cell culture and the R6/2 transgenic animal model. The goal of the current study is to identify and develop small chemical compounds that are non‐toxic and can selectively disrupt the binding of mhtt to CaM. To this end, we employed a high throughput AlphaScreen assay along with counter‐screening assays and identified 481 hit compounds that disrupt the interaction between (His)htt‐CaM(GST). The structures of the hits obtained were analyzed and structurally diverse representative scaffolds were chosen for further development. Analogs of these compounds synthesized from the selected scaffolds were re‐screened in the primary AlphaScreen assay and tested for cytotoxicity. Next, assays were employed to determine if the hits identified in the primary screen can selectively disrupt the mhtt‐CaM interaction without affecting other functions of CaM. The compound selectivity is being determined using two CaM dependent enzymes which are abundantly expressed in neuronal cells and play an important role in neuronal function; Ca+2/CaM dependent death associated protein kinase 1 (DAPK1) and Ca+2/CaM dependent protein kinase 2 gamma (CAMK2ϒ). We have identified numerous compounds that have shown preferential activity in disrupting the (His)htt‐CaM(GST) interaction. Compounds that were non‐toxic and selectively disrupted the binding of mhtt to CaM are tested in cell‐based screening assays to determine if the compounds are protective against deleterious effects of mhtt expression. So far, we have identified two scaffolds that selectively disrupt the binding of mhtt to calmodulin and show protection against mhtt‐induced toxicity. Studies are ongoing to determine if these scaffolds will reduce accumulation of aggregated htt protein and normalize mitochondrial deficits associated with mhtt expression. In the future, these compounds will be tested for their protective effects in animal models of HD. Overall, these studies will aid in identifying compounds that will serve as novel and promising biological probes for drug development in HD.Support or Funding Information1RO1NSO88059This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.