Browsing by Author "Akhmadi, Aizhan"

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    CHARACTERIZATION OF A MOLECULAR FUNCTION OF DJ-1 AS CPGA HYDROLASE
    (Nazarbayev University School of Sciences and Humanities, 2024) Akhmadi, Aizhan
    Parkinson’s disease (PD) is a neurodegenerative disorder marked by a steady decrease in motor function due to the death of dopaminergic neurons in the substantia nigra, resulting in the reduced levels of dopamine in the striatum. Most cases of PD are sporadic, though 10- 15% of individuals have hereditary Parkinsonism linked to mutations affecting various proteins. Studying the molecular function of proteins linked to hereditary PD helps in understanding the mechanisms underlying the development and progression of this disease even in individuals with sporadic PD. Therefore, is of utmost biomedical significance. This thesis paper focuses on DJ-1 - a small protein mutated in rare cases of early-onset autosomal recessive Parkinson's disease. While the neuroprotective function of DJ-1 in humans is clearly established, there is no universally accepted mechanism clearly explaining how DJ-1 prevents the premature death of dopaminergic neurons. This uncertainty manifests itself in a very large number of functions that have been suggested for DJ-1 in different systems none of which definitively clarified its role in the genesis and advancement of Parkinson's disease. Our results describe in detail a novel function of DJ-1 as a hydrolase of cyclic 3-phosphoglyceric anhydride (cPGA). Formation of cPGA in glycolysis and cPGA hydrolase activity have been recently suggested based on indirect evidence however neither could be demonstrated in a direct experiment because of instability of cPGA. We synthesized cPGA from 3- phosphoglycerate using a standard dehydrating agent (EDC) in acidic conditions and, for the first time, demonstrated the existence of cPGA in solution by NMR. We established simple procedures for quantitative assessment of cPGA spectrophotometrically after converting it into a thioester. These methods allowed a comprehensive characterization of cPGA as an unstable electrophile with a high propensity to acylate biological nucleophiles. Further, we demonstrate that human DJ-1 and its E. coli homolog YajL are highly efficient cPGA hydrolases and provide evidence that the endogenous cPGA hydrolase activity of DJ-1 is both necessary and sufficient for the protection of proteins from acylation by cPGA. This work establishes cPGA as a novel reactive metabolite that can irreversibly acylate proteins and presents strong evidence that DJ-1 possesses a unique function that inactivates cPGA by hydrolysis. This new and unique function of DJ-1 provides the best explanation of neuroprotection by DJ-1 so far and opens a new and exciting chapter in research of reactive metabolites and their role in neurodegeneration.