| Pcyt2 is a regulatory enzyme in phosphatidylethanolamine and plasmalogen biosynthesis through the Kennedy pathway. Phospholipid profiles are extensively altered in cancers, and this enzyme in particular is located in a chromosomal region frequently modified in breast cancers. Regulational mechanisms were revealed in both non-cancerous and cancerous breast cells. For transcription initiation, gel-shifts revealed NF-Y binds to the CAAT box in both cell types, but EGR1 uniquely interacts with Sp proteins within the GC box region in non-cancerous cells. Breast cancer cells expressed ~10% the Pcyt2 protein of non-cancerous cells, yet possessed equal catalytic activity. This abnormality was attributed to an increased proportion of highly phosphorylated Pcyt2alpha in cancer cells. Phorbol ester stimulation decreased promoter activity; potentially through differential Sp3 and C/EBP binding about the CAAT box in non-cancerous and cancerous cells respectively. In stimulated cancer cells, Pcyt2 transcript and protein expression were decreased and increased respectively, while enzymatic activity was unchanged. |
