Mitochondrial energy metabolism and signalling in human glioblastoma cell lines with different PTEN gene status

Abstract

Glioblastomas epidemiology and aggressiveness demand for a well characterization of biochemical mechanisms of the cells. The discovery of oxidative tumours related to chemoresistance is changing the prevalent view of dysfunctional mitochondria in cancer cells. Thus, glioblastomas metabolism is now an area of intense research, wherein was documented a high heterogeneity in energy metabolism and in particular in mitochondrial OxPhos. We report results gained by investigating mitochondrial OxPhos and bioenergetics, in a model of three human glioblastoma cell lines characterized by a different PTEN gene status. Functional data are analysed in relation to the expression levels of some main transcription factors and signalling proteins, which can be involved in the regulation of mitochondrial biogenesis and activity. Collectively, our observations indicate for the three cell lines a similar bioenergetic phenotype maintaining a certain degree of mitochondrial oxidative activity, with some difference for PTEN-wild type SF767 cells respect to PTEN-deleted A172 and U87MG characterized by a loss-of-function point mutation of PTEN. SF767 has lower ATP content and higher ADP/ATP ratio, higher AMPK activating-phosphorylation evoking energy impairment, higher OxPhos complexes and PGC1α-Sirt3-p53 protein abundance, in line with a higher respiration. Finally, SF767 shows a similar mitochondrial energy supply, but higher non-phosphorylating respiration linked to dissipation of protonmotive force. Intriguingly, it is now widely accepted that a regulated mitochondrial proton leak attenuate ROS generation and in tumours may be at the base of pro-survival advantage and chemoresistance.

Diet-regulated behavior: FVB/N mice fed a lean diet exhibit increased nocturnal bouts of aggression between littermates

“…In contrast, when the ratio of ADP/ATP was assessed in tissue, the lean-diet-fed mice demonstrated a significant decrease in comparison to high-fat-diet-fed mice (Figure 5(b)). This suggests that energy status and metabolism are the crux of the enhanced nocturnal activity, 16–18 which is consistent with this strain. Immunoblotting of the tissues from the animals showed no apparent differences in the expression of the androgen receptor between groups (Figure 5(c)).…”

“…8 Previous studies with crosses of inbred CBA and outbred CFLP mouse strains determined that lean mice exhibit more nocturnal wheel running and higher food intake, compared to fat mice, with lean mice expending substantially more energy towards activity. 18…”

Mitochondrial enzyme GLUD2 plays a critical role in glioblastoma progression

“…GLUD1 gene is located on 10q and is expressed widely, whereas GLUD2 is an intronless gene located on the X chromosome with expression specificity for nervous and testicular tissues [ 23 , 24 ]. In the brain, GLUD2 expression is mainly associated with astrocytes [ 24 , 25 ] with a substantial mitochondrial localization, representing up to 10% of the matrix protein [ 10 , 25 , 26 ]. GLUD2 contributes to important cellular processes, such as the Krebs cycle, ammonia homeostasis and energy production [ 10 , 15 , 24 , 26 , 27 ]; however, its role in cell biology is still incompletely understood [ 26 ].…”

“…In the brain, GLUD2 expression is mainly associated with astrocytes [ 24 , 25 ] with a substantial mitochondrial localization, representing up to 10% of the matrix protein [ 10 , 25 , 26 ]. GLUD2 contributes to important cellular processes, such as the Krebs cycle, ammonia homeostasis and energy production [ 10 , 15 , 24 , 26 , 27 ]; however, its role in cell biology is still incompletely understood [ 26 ]. GLUD2 has the ability to act on both directions of the reaction depending on the availability of the substrate, but in the cancer it is thought that it works mainly in the direction of the oxidative deamination of glutamate and α-KG production [ 28 ].…”

“…One of the emerging hallmarks of cancer is the deregulation of cellular energetics and the most significant reprogramming occurs in the metabolic machinery in GBM [ 1 , 10 , 11 ]. Thus, cancer cell metabolism is now a field of intensive investigation to discover new valuable therapeutic targets and biomarkers [ 10 ]. In particular, it is well known that glutamine metabolism plays key roles in cellular growth and invasion, supporting tumor progression and poor patient outcomes [ 12 ].…”