CHARACTERIZATION OF THE INTERACTION BETWEEN THE UBIQUITINATION PATHWAY PROTEINS, UBE2A AND UCHL-1, ASSOCIATED WITH NEUROLOGICAL DISORDERS

The ubiquitin conjugating enzyme 2 A (UBE2A) is a key component in ubiquitination pathway, important not only for targeting protein degradation via proteasome but also regulating other cellular processes such as DNA repair, ensuring genomic integrity, removing defective mitochondria and regulating gene expression. Mutations that disturb UBE2A activity have been associated with X-linked intellectual disability (XLID) type Nascimento. The pathogenic Q93E missense mutation, situated near the catalytic site, was identified in two Brazilian brothers with mild intellectual disability and impaired speech. This mutation affects the enzyme's ability to perform aminolysis, thereby inhibiting product formation. On the other hand, the G23R mutation, located on the opposite side known for its relevance in ubiquitin binding, was also identified in XLID patients who presented similar symptoms. Studies of global proteome of ubiquitination with brain tissue from UBE2A Q93E knocking murine model indicate differential ubiquitination of ubiquitin C-terminal hydrolase L1 (UCHL1), a highly expressed protein in neurons and also related to neurological diseases. However, the association between UCHL1 and UBE2A remains poorly understood. Here, we propose a functional and structural approach to understand how both proteins are related and what are the effects of UBE2A Q93E and G23R mutations on recognizing and regulating UCHL1 activity. In vitro ubiquitination assay with E1, UBE2A, ubiquitin, ATP and UCHL1 WT or C90S mutant confirmed UCHL1 as a target of modification of UBE2A. This study, besides elucidating important aspects of ubiquitination pathway role in neurological disease, may also contribute to identifying new pharmacological targets and therapies for XLID Nascimento type.