Inhibition of phosphatidylcholine synthesis is associated with excitotoxic cell death in cerebellar granule cell cultures

Abstract

Glucose deprivation (GD) enhances the sensitivity of cerebellar granule cells to die by excitotoxicity. Neither 70 min of GD, a treatment that depletes cell energy resources, nor exposure to 20 microM glutamate (GLU) for 30 min, induce significant cell death in cultures of cerebellar granule cells. However, the combined treatment with GLU and GD induces choline (Cho) release before excitotoxic cell death. We investigated whether the neurotoxic effect of this treatment is related with inhibition of phosphatidylcholine (PC) synthesis. We found that exposure to GLU for 30 min, to GD for 70 min, and to the combination of both, inhibited PC synthesis at the end of treatment by 71%, 92% and 91%, respectively. The inhibition of PC synthesis was accompanied by a decrease in the incorporation of [(3)H]Cho into phosphocholine and by an increase of the intracellular content of free [(3)H]Cho, indicating that these treatments inhibit the synthesis of PC by inhibiting choline kinase activity. However, only the combined treatment with GLU and GD induced a prolonged inhibition of PC synthesis that extended after the end of treatment. These results show that excitotoxic death is associated with sustained inhibition of PC synthesis and suggest that this effect of the combined treatment with GLU and GD on PC synthesis is produced by an action on an enzymatic step downstream of choline kinase activity.

NMDA Receptor Overactivation Inhibits Phospholipid Synthesis by Decreasing Choline–Ethanolamine Phosphotransferase Activity

“…Choline kinase and CTP:phosphocholine cytidylyltransferase, the enzymes that catalyze the sequential conversion of Cho into phosphocholine and CDP-choline require ATP and CTP, respectively. Indeed, treatments that deplete cell energy resources, e.g., glucose deprivation, elicit a marked decrease in choline kinase activity (Gasull et al, 2002). In cortical cells, neurotoxic concentrations of NMDA produce a timedependent reduction of cell energy resources that may reach a 20% decrease of cell energy charge 30 min after treatment (Ankarcrona et al, 1995).…”

Chemical genetic interactions of New Zealand bee products in Saccharomyces cerevisiae

“…Previous studies demonstrated that inactivation of PC increased apoptosis and the cause of apoptosis linked with accumulation of the PC precursor, CDP-choline (Cui et al, 1996;Gasull et al, 2002;Williams et al, 1998). This is in line with our observation of pct1∆ being less hypersensitive to bee venom treatment compared to cpt1∆ and ept1∆ (Figure 4.2B) as Pct1p catalyses the reaction of choline phosphate and CDP to form CDP-choline (Ejsing et al, 2009).…”

Neurochemical Aspects of Excitotoxicity

“…The inhibition of PtdCho synthesis is accompanied by a decrease in the incorporation of [ 3 H]choline ([ 3 H]Cho) into phosphocholine and by an increase of the intracellular content of free [ 3 H]Cho, indicating that these treatments inhibit the synthesis of PtdCho by inhibiting choline kinase activity (Gasull et al, 2002). The inhibition of PtdCho synthesis is accompanied by a decrease in the incorporation of [ 3 H]choline ([ 3 H]Cho) into phosphocholine and by an increase of the intracellular content of free [ 3 H]Cho, indicating that these treatments inhibit the synthesis of PtdCho by inhibiting choline kinase activity (Gasull et al, 2002).…”