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Occurrence of the Crabtree effect in HeLa cells
R F Melo1, F R Stevan, A P Campello
1Departamento do Bioquímica da Universidade Federal do Paraná Curitiba, Brasil.
Insights
HeLa cells exhibit the Crabtree effect, a metabolic phenomenon impacting cellular respiration. Pyruvate kinase activity in these cells is modulated by various metabolites, indicating its role in regulating this effect.
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.
Abstract:
The occurrence of a Crabtree effect in HeLa cells was detected. Some properties of pyruvate kinase (PK) were also evaluated. Hexose phosphate, triose-phosphate and phosphoenolpyruvate (PEP) significantly decreased the oxygen consumption of digitonin-permeabilized HeLa cells, which were oxidizing succinate. The Crabtree effect promoted by PEP was concentration-dependent and was lowered by an increase of ADP concentration, suggesting a participation of PK. The dependence of fructose-1,6-bisphosphate (FDP) by HeLa cell PK was observed. The PK of HeLa cells was inhibited by L-alanine only in the absence of FDP, while in the presence of the metabolite, an increase in the activity was observed. PK was also inhibited in the presence of L-histidine and L-leucine, while L-serine promoted activation. L-Cysteine and L-phenylalanine also inhibited the PK of HeLa cells. This, together with the sigmoidal character in relation to substrate concentration, suggests the presence of the K-type of PK in HeLa cells.
