Analysing the effects of lactacystin on membrane lipidomics and neuroexocytosis using TOF-SIMS imaging and electrochemical methods

The relationship between UPS and neurodegenerative diseases is of interest, yet underlying changes in cellular metabolism are unclear. Herein, a proteasomal inhibitor, lactacystin, has been used in a dose dependent manner on a para-neuron model cell line and membrane lipid changes have been measured by using mass spectrometry imaging. In the meantime, single cell amperometry (SCA) and intracellular vesicle impact electrochemical cytometry have been employed as novel electrochemical methods to measure the events of neuroexocytosis. According to the measurements, lipids with negative head groups such as phosphatidylserines (PS), phosphatidylinositols (PI) and phosphatidic acid (PA) showed similar trends. Abundance levels of ether-linked phosphatidylethanolamines (PE-O) and number of released catecholamines monitored by SCA significantly decreased with 1 µM-4h lactacystin treatment. Unlike other doses, 10 µM-4h changed the dynamics of exocytotic pre-spike events and elevated phosphatidylethanolamine (PE) levels. Besides; PE, PE-O, PI and PS levels upon 10 µM-8h treatment showed a decreasing trend. Thus, lactacystin at certain doses promotes transient fusion pore stabilization and neurotransmitter leakage at the very beginning of neuroexocytosis which may be concurrently related with the abundance levels of lipids with negative head groups. Consequently, proteasomal inhibition can have double-edged activity in the cell by changing neuroexocytotic dynamics and altering different membrane lipid classes.