Utah Neuroscientists Use Gene Editing Technology to Identify Drugs that May Improve Treatment for Individuals with Parkinson’s Disease
Sep 20, 2021 12:30 PM
Scientists in the Neurodegenerative Disease Laboratory of the Department of Neurology, University of Utah, have discovered compounds that could represent the beginnings of development of a novel therapy for Parkinson’s disease (PD). The study focused on a compound designated A-443654 among others discovered following a robotic high throughput compound screen of over 150,000 compounds for their ability to reduce the expression of the alpha synuclein protein. In the neurons of Parkinson’s disease patients, alpha synuclein becomes highly overabundant, leading to the formation of toxic oligomers and pathogenic protein aggregations. Following Alzheimer’s disease, Parkinson’s disease is the second most common of all the neurodegenerative diseases, and nearly all cases are characterized by the overabundance of alpha synuclein. But Parkinson’s disease is not the only disease characterized in this way; dementia with Lewy bodies (DLB), diffuse Lewy body disease (DLBD), and glial cytoplasmic inclusions (GCIs) in multiple system atrophy (MSA) have a similar overabundance of alpha synuclein. Collectively, these diseases are therefore referred to as the synucleinopathies, and, potentially, therapeutics that follow the discovery of A-443654 may benefit each of these disorders.
The discovery of A-443654 had its beginnings in the ingenuity of Dr. Duong Huynh of the Department of Neurology, University of Utah. He envisioned a cellular model for reporting the expression of alpha synuclein. In this model, Dr. Huynh used a technique called “zinc finger nuclease gene editing” to insert the gene from the firefly, which produces the enzyme that generates firefly luminescence, downstream of the alpha synuclein gene in cultured human cells. Thus, under the right conditions, when cells are treated with the chemical substrate for the firefly enzyme, a small quantity of light is produced—which can be quantified by a sensitive light detector. Compounds that are added to the cell cultures that lower alpha synuclein expression reduce the light that the cells produce. In 2011, Dr. Huynh was funded by the Michael J. Fox Foundation (MJFF) for Parkinson’s Research to produce this cell-based screening model for identifying compounds lowering alpha synuclein expression. The production of the model was completed, leaving the inevitable next step to be performed: the high throughput screening of compounds.
This model for identifying compounds was a great achievement; however, Dr. Huynh did not have the funding nor resources available to perform the compound screen. Even small screening compound libraries are costly and take considerable time to perform with rigor and reliability. However, a perfect storm was brewing. Drs. Stefan Pulst and Daniel Scoles in the Neurodegenerative Disorders Lab had previously been awarded a large grant from the National Institutes of Health (NIH) to perform robotic compound screens for compounds relevant to the treatment of spinocerebellar ataxia. Their study was performed in collaboration with investigators inside the National Center for Advancing Translational Sciences (NCATS) laboratory of the NIH, who maintain libraries of hundreds of thousands of compounds. NCATS agreed to support the study—which was led by Anton Simeonov, the scientific director at NCATS and Mark Henderson—by performing the high throughput compound screen provided that the Utah lab could obtain funding for the downstream validation studies that would be necessary to prove that the compounds specifically lowered alpha synuclein expression. Therefore, Dr. Scoles with Dr. Huynh presented a grant to the MJFF, proposing to perform the screen with the sweetened deal that our NIH government laboratory would donate the screening library and effort. The second study for the compound screen was funded by MJFF in 2015, resulting in the robotic screening of 155,885 compounds.
The compound screens are an immense effort made possible by Stäubli’s computer-controlled robotic arms, which were originally designed for the assembly of automobiles. Each assay was done in 1536-well plates and were performed in multiple doses, meaning that about 1,000 plates or 1.5 million individual assays were required to screen the 155,885 compounds. Screens performed in doses are known as quantitative high-throughput screens (qHTS) and are ideal for ranking all compounds for efficacy by dose.
In 2018, a major setback struck the laboratory, threatening to delay progress on the study. Unfortunately, Dr. Huynh passed away during his vacation to visit family in Vietnam. He led an amazing life that is highlighted here. With Dr. Huynh’s untimely passing, Dr. Mandi Gandelman, a postdoctoral researcher in the lab, stepped up to complete the characterization of A-443654. Dr. Gandelman was able to independently validate A-443654 as an inhibitor of alpha synuclein expression in multiple cellular models, heightening the rigorous nature of the study. Furthermore, she demonstrated that other diseases’ model cells used in the laboratory that had elevated alpha synuclein also abnormally express other disease-related proteins considered markers of abnormal autophagy and endoplasmic reticulum stress and that all of these could be normalized by treatment with A-443654. Then, Dr. Gandelman successfully produced and cultured dopaminergic neurons from pluripotent stem cells derived from a Parkinson’s disease patient with overabundant alpha synuclein and proved that A-443654 could reduce the levels of alpha synuclein in these cells.
The study reporting the discovery of A-443654 has been published in the Journal of Biological Chemistry and is titled “The AKT modulator A-443654 reduces α-synuclein expression and normalizes ER stress and autophagy.”