Courtney Holdaway | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Courtney Holdaway. This seminar is open to the general public to attend.

MSc with Dr. Rene Jacobs.

Thesis Topic: Alterations in Phosphatidylethanolamine Metabolism Impacts Lipid Storage and Metabolism in Hepatocytes.

Abstract:  

Phosphatidylethanolamine (PE) is the second most abundant glycerophospholipid in eukaryotic membranes and is involved in several cellular processes. An important pathway for de novo PE synthesis is the Kennedy Pathway. The rate limiting enzyme in the pathway, CTP:phosphoethanolamine cytidyltransferase, catalyzes the synthesis of CDP-ethanolamine from phosphoethanolamine (pEtn) and CTP. Ethanolamine phosphate phospholyase (ETNPPL) has the potential to breakdown pEtn by catabolizing it to form acetaldehyde, ammonium, and inorganic phosphate. Research on this enzyme is limited and it is unclear how its activity affects PE synthesis; therefore, an investigation into ETNPPL’s biological effects is required.

ETNPPL was expressed in human hepatoma cell line (Huh7) by stable transfection, allowing for long-term expression in cells without ETNPPL. Factors of hepatocellular function were assessed including mitochondrial respiration, cell proliferation, lipid synthesis, lipolysis, and lipid secretion.

Induction of ETNPPL expression increased lipid storage in Huh7 cells, and reduced cell proliferation. Huh7 cells expressing ETNPPL proliferate at a slower rate than control and have increased mRNA expression of p53 and tumor suppressor genes (CDKN1A, BBC3, BAX, BRCA1), implicating ETNPPL in cell proliferation, cancer development and/or tumor progression. We show that ETNPPL reduces cellular pEtn synthesized from ethanolamine, which decreased synthesis of PE and an increased PC:PE ratio, which has been shown to be associated with metabolic dysfunction-associated steatotic liver disease (MASLD) and impaired mitochondrial function. Experiments conducted show increased neutral lipid storage accompanied by decreased ATP production and oxygen consumption; however, no differences in triglyceride secretion were seen, although ApoB100 secretion was reduced.

In conclusion, ETNPPL rewires hepatic lipid metabolism, altering several processes including increasing lipid storage and decreasing proliferation. The impacts observed in this study may create a link between hepatic ETNPPL expression and MASLD/HCC pathophysiology