Fructose-1,6-bisphosphatase 1, a rate-limiting
enzyme in gluconeogenesis, was recently shown to be a
tumor suppressor. However, the functions of
fructose-1,6-bisphosphatase 1 in the regulation of mitophagy and apoptosis remain unknown. Here, we investigated the effects of
fructose-1,6-bisphosphatase 1 on mitophagy and apoptosis as well as their underlying mechanisms in
breast cancer cells. In this work, the
messenger RNA and
protein expression of various molecules were determined by quantitative realtime polymerase chain reaction and western blot, respectively. Gene-expression correlations were obtained from The
Cancer Genome Atlas
Breast Cancer database and analyzed using cBioPortal. The levels of cellular
reactive oxygen species and apoptotic index were detected by flow cytometry. The mitochondrial membrane potentials were assessed with a
JC-1 fluorescent sensor. Subcellular structures were observed under a transmission electron microscope. The intracellular distribution of translocase of outer membrane 20 was detected by immunofluorescence staining.
Protein-
protein interactions were analyzed by immunoprecipitation. Our results indicated that
fructose-1,6-bisphosphatase 1 expression was negatively correlated with autophagy level in
breast cancer.
Fructose-1,6-bisphosphatase 1 restrained autophagy activity by increasing the level of p62 and decreasing the levels of LC3 and
Beclin 1. Additionally,
fructose-1,6-bisphosphatase 1 promoted cell apoptosis by upregulating the levels of intracellular ROS and expression of
pro-apoptotic proteins such as cleaved PARP, cleaved
Caspase 3, and Bax and downregulating the levels of
anti-apoptotic proteins such as PARP,
Caspase 3, and Bcl-2. Finally,
fructose-1,6-bisphosphatase 1 limited the efficient removal of diseased mitochondria and reduced the
messenger RNA and
protein expressions of HIF-1α, BNIP3L/NIX, and BNIP3. More importantly,
fructose-1,6-bisphosphatase 1 facilitated co-action between Bcl-2 and
Beclin 1, which may be important in the mechanism of
fructose-1,6-bisphosphatase 1-mediated mitophagy inhibition. In summary, loss of mitophagy by
fructose-1,6-bisphosphatase 1-mediated repression promotes apoptosis in
breast cancer.