Presenting Author Rowan University Glassboro, New Jersey
Polyamines are vital for cellular life. Polyamines such as putrescine, spermidine, and spermine regulate the essential cellular process, including gene expression and cell proliferation. Given its cellular role, polyamine concentration in cells is tightly controlled. However, aberrant polyamine metabolism is associated with numerous diseases, including cancer. Growing evidence suggests that elevated polyamine levels are the absolute requirement for tumor growth and progression. The concentrations of cellular polyamines are controlled by the polyamine regulatory circuit comprising three different proteins: Ornithine Decarboxylase (ODC), Ornithine Decarboxylase Antizyme (OAZ), and Antizyme Inhibitor (AZIN). While ODC is directly involved in polyamine biosynthesis, OAZ and AZIN regulate the ODC activity via protein-protein interactions. The dysregulation of ODC, OAZ, and AZIN leads to elevated polyamines in numerous pathologies, making them attractive targets to control polyamine levels. Besides regulating polyamine synthesis, OAZ is believed to modulate polyamine transport via multiple pathways. However, the precise mechanism of OAZ-mediated polyamine regulation outside of the polyamine biosynthetic pathway remains elusive. We hypothesize that OAZ sequestration results in increased polyamine uptake. To provide evidence to our hypothesis, we generated covalent OAZ-mimetic inactivators targeting both ODC and AZIN. Using biochemical experiments, we demonstrate that these OAZ-mimetics inhibit the activity of ODC and prevent the sequestration of OAZ by AZIN. Using Mass spectrometric experiments, we determine the covalent binding of OAZ-mimetics to both ODC and AZIN. We employ a novel gel assay to assess the rate of covalent modification of ODC and AZIN. Finally, using computational modeling, we determine the mode of binding of OAZ-mimetics to both ODC and AZIN to provide insights into inhibition mechanisms.
