Identification of therapeutic targets for stimulation of the ubiquitin-proteasome system in neurodegenerative diseases

• Applicant: Maria Elka Gierisch, Ph.D.
• Subject Area: Experimental Models for the Understanding of Nervous System Diseases ; Molecular Biology and Physiology of Neurons and Glial Cells ; Cell Biology
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 396329917

Neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease or genetic disorders that are caused by polyglutamine expansions such as Huntington’s disease and Kennedy’s disease are becoming more and more frequent in developed countries due to an increased life expectancy. Most of the disorders are characterized by an accumulation of aberrant or misfolded proteins in intracellular inclusion bodies in the central nervous system. Misfolded proteins are normally eliminated by an intracellular proteolytic machinery called the ubiquitin-proteasome system. They are labelled posttranslationally with (poly-) ubiquitins by various involved proteins. Aberrant proteins are then destined for proteolytic destruction by the proteasome. The age-dependent accumulation of mutant or polyglutamine expanded proteins in neuronal cells has been thought to be a result of a dysfunctional ubiquitin-proteasome system. However, the Dantuma laboratory and also others have found that by using reporter mice for the ubiquitin system that the activity of the system is well-preserved even in late stages of the pathology. They have shown that an accelerated proteasomal degradation of polyglutamine expanded proteins reduces the steady-state levels of the protein, prevents the formation of intracellular inclusions and increases cell viability. In the proposed project, I aim first to develop a novel cell-based reporter assay in which stimulators of the ubiquitin-proteasome system can be identified. In the second part, I will use this new assay in a high-content, microscopy-based screen on a platform present within the departmental microscope facility to identify potential molecular targets that upon inhibition will result in accelerated degradation of aberrant proteins. For this purpose, transcripts of around 200-500 directly or indirectly involved proteins of the ubiquitin-proteasome system will be targeted by a custom designed siRNA library. In a third step, I will further characterize the mechanism on how depletion of these molecular targets stimulates proteasomal degradation. Finally, I will investigate the specificity of target knockdown and knockout for degradation of various aberrant proteins involved in neurodegenerative diseases and characterize how the stimulation acts on inclusion body formation. With this proposed strategy, I aim to identify molecular targeting possibilities in neurodegenerative disorders and anticipate that characterizing the ubiquitin-proteasome system stimulation leads to novel treatment strategies.

• DFG Programme: Research Fellowships
• International Connection: Sweden
• Host: Professor Dr. Nico P. Dantuma