A mechanism for suppression of the CDP-choline pathway during apoptosis

Abstract

Phosphatidylcholine (PtdCho), a zwitterionic glycerophospholipid that comprises 40-60% of eukaryotic membrane mass, is an essential component of lung surfactant, bile, and lipoproteins, and a source for signaling molecules such as diacylglycerol (DAG) and phosphatidic acid

CTP:phosphocholine cytidylyltransferase: Function, regulation, and structure of an amphitropic enzyme required for membrane biogenesis

“…Cleavage at this site in response to farnesol-induced apoptosis in CHO cells excluded CCTa from the nucleus but did not affect in vitro activity [185,218]. In contrast, caspase cleavage of CCTa in P. aeruginosa-infected murine lung epithelial cells was linked to decreased PC synthesis and apoptosis [219].…”

“…Notably, many apoptotic insults also activate caspase 3 processing of CCTa and removal of the NLS (Section 3.4). Caspase 3 processing of CCTa was a relatively late event that caused cytosolic retention of the enzyme and increased in vitro activity but did not strongly influence the apoptotic program [185,186,218]. Thus caspase processing of CCTa may only affect enzyme function in specific developmental contexts, or the enzyme might simply be an innocent bystander that is proteolyzed during disassembly of the cell.…”

“…In rat CCTa, the N-termini contains a site for caspase 3 cleavage at D28, precisely at the end of the predicted NLS [185,218]. Cleavage at this site in response to farnesol-induced apoptosis in CHO cells excluded CCTa from the nucleus but did not affect in vitro activity [185,218].…”

“…A more extensive analysis of inhibition of the CDP-choline pathway in apoptotic cells revealed that caspase 3 cleavage of CCTa is not required for inhibition of PC synthesis [218]. Rather uptake of choline by intermediate affinity transporters [218] and/or inhibition of the terminal steps in the pathway [220,221] are responsible for cessation of PC synthesis.…”

Lipid-associated PML domains regulate CCTα, Lipin1 and lipid homeostasis

“…Lysates were separated by SDS-PAGE, transferred to nitrocellulose membranes and incubated in TBS (20 mM Tris-HCl [pH 7.4] and 500 mM NaCl):Odyssey blocking (5:1, v/v) for 1h. Nitrocellulose was blotted using primary antibodies against human CCTα (Morton et al, 2013), PML (rabbit polyclonal A301-167A, Bethyl Laboratories), V5 monoclonal (MCA-1360, BioRad), or β-actin (mouse monoclonal AC15, Sigma-Aldrich). Proteins were visualized with goat anti-mouse or goat anti-rabbit IRDye-800 or -680 secondary antibodies (LI-COR Biosciences) using an Odyssey Imaging System and application software (v3.0).…”