Ubiquitin-conjugating enzymes (E2) are key components in the protein ubiquitination pathway which, in addition to signaling substrates for degradation, can also regulate other cellular processes. UBE2A is an E2 of this pathway and has been reported to act in several processes, such as DNA repair, maintenance of genomic integrity, regulation of p53 expression, removal of dysfunctional mitochondria and regulation of proteasome activity. Mutations in the UBE2A gene can directly interfere with the capacity for interaction and ubiquitination of its substrates, and have been associated with the X-linked Intellectual Disability type Nascimento (ID) syndrome. Among the mutations described in the literature, Q93E, located close to the catalytic site of the enzyme and identified in Brazilian patients, and G23R, present on the non-covalent interaction surface with ubiquitin (backside), both characterized by impacting the catalytic activity of UBE2A. The global ubiquitination proteome (ubiquitinome - GlyGly(K) sites) was previously performed with brain from control animals (WT) and UBE2A knockin Q93E, and revealed candidate proteins for ubiquitination targets of UBE2A activity. Among the proteins identified with reduced levels of ubiquitination in the Q93E mutant of UBE2A, some proteins that modulate the ubiquitination pathway were identified, including UCH-L1, which is also associated with neurological diseases. UCH-L1 is highly expressed in neurons and acts not only as a deubiquitinase enzyme, but also has ubiquitin ligase activity, indicating a central role in the regulation of the neuronal ubiquitination pathway. This project proposes a functional and structural approach to elucidate the effect of UBE2A mutations Q93E and G23R, associated with ID, in the interaction with UCH-L1 and regulation of its activity. The elucidation of these processes may contribute to the identification of potential therapeutic targets and a better understanding of the involvement and regulation of the ubiquitination pathway in neurological diseases.
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