Calpain mediated ataxin-3 cleavage in the molecular pathogenesis of SCA3

• Applicant: Dr. Jeannette Hübener
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2013 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 246346398

aggregates which contain ataxin-3, the mutated protein in SCA3, in a specific subtype of neurons. The mechanism leading to the formation of aggregates is unknown, but may involve cleavage of ataxin-3 by proteolytic enzymes. In 2011, Koch et al. demonstrated the ability of calpains to cleave ataxin-3 in patient-specific induced pluripotent stell cell (iPSC)-derived neurons followed by the formation of SDS-insoluble aggregates. In our project we will analyze the question which calpains can cleave ataxin-3 at which amino acid position using different in vitro and in vivo techniques. To clarify which amino acid are putative cleavage sites in the ataxin-3 protein we are using calpain cleavage assay in cell culture as well asmass spectroscopy analyzes. Additionally, we focused on the question if calpain-1 or calpain-2 can cleave ataxin-3 in vivo. Therefore, we crossbreed calpain-1 or calpain-2 knockout mice with a SCA3 transgenic mouse line (overexpressing the human ataxin-3 with 70 glutamines) and analyze the formation of toxic fragments and aggregates as well as the age at onset and progression of neurological symptoms using different behavior tests.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Olaf Riess