Occurrence of the Crabtree effect in HeLa cells

Area of Science:

• Biochemistry
• Cell Biology
• Metabolic Regulation

Background:

• The Crabtree effect describes the phenomenon where high glucose concentrations lead to fermentation even in the presence of oxygen.
• HeLa cells are a widely used human cancer cell line in biological research.
• Pyruvate kinase (PK) is a key enzyme in glycolysis, catalyzing the final step.

Purpose of the Study:

• To investigate the occurrence and characteristics of the Crabtree effect in HeLa cells.
• To evaluate the properties and regulatory mechanisms of pyruvate kinase (PK) in HeLa cells.

Main Methods:

• Utilized digitonin-permeabilized HeLa cells for metabolic assays.
• Measured oxygen consumption in response to various substrates and effectors.
• Assessed pyruvate kinase activity in the presence of different metabolites and amino acids.

Main Results:

• A Crabtree effect was observed in HeLa cells, evidenced by decreased oxygen consumption with specific metabolites.
• Phosphoenolpyruvate (PEP) promoted the Crabtree effect in a concentration-dependent manner, influenced by ADP levels.
• HeLa cell PK activity showed dependence on fructose-1,6-bisphosphate (FDP) and was differentially regulated by amino acids (L-alanine, L-histidine, L-leucine, L-serine, L-cysteine, L-phenylalanine).
• Sigmoidal kinetics with respect to substrate concentration suggest the presence of K-type PK.

Conclusions:

• HeLa cells exhibit the Crabtree effect, linked to pyruvate kinase activity.
• Pyruvate kinase in HeLa cells displays complex regulation by metabolites and amino acids, characteristic of the K-type isoenzyme.
• These findings contribute to understanding metabolic dysregulation in cancer cells.