ABSTRACT
Parkin, an E3 ubiquitin ligase, plays a role in maintaining mitochondrial homeostasis through targeting damaged mitochondria for mitophagy. Accumulating evidence suggests that the acetylation modification of the key mitophagy machinery influences mitophagy level, but the underlying mechanism is poorly understood. Here, our study demonstrated that inhibition of histone deacetylase (HDAC) by treatment of HDACis activates mitophagy through mediating Parkin acetylation, leading to inhibition of cervical cancer cell proliferation. Bioinformatics analysis shows that Parkin expression is inversely correlated with HDAC2 expression in human cervical cancer, indicating the low acetylation level of Parkin. Using mass spectrometry, Parkin is identified to interact with two upstream molecules, acetylase acetyl-CoA acetyltransferase 1 (ACAT1) and deacetylase HDAC2. Under treatment of suberoylanilide hydroxamic acid (SAHA), Parkin is acetylated at lysine residues 129, 220 and 349, located in different domains of Parkin protein. In in vitro experiments, combined mutation of Parkin largely attenuate the interaction of Parkin with PTEN induced putative kinase 1 (PINK1) and the function of Parkin in mitophagy induction and tumor suppression. In tumor xenografts, the expression of mutant Parkin impairs the tumor suppressive effect of Parkin and decreases the anticancer activity of SAHA. Our results reveal an acetylation-dependent regulatory mechanism governing Parkin in mitophagy and cervical carcinogenesis, which offers a new mitophagy modulation strategy for cancer therapy.
ABSTRACT
Objective To investigate the effects of human leukocyte-associated antigen-G (HLA-G) expression in silencing trophoblast cell line JEG-3 under normal and hypoxic conditions on invasion and proliferation of JEG-3 cells. Methods Inhibition of HLA-G expression in JEG-3 cells by transfection of small interfering RNA (siRNA),the transfected JEG-3 cells were divided into 4 groups: normoxia control group, hypoxia control group, normoxia inhibition group and hypoxia inhibition group. The levels of HLA-G mRNA and protein in 4 groups of cells were detected by real-time quantitive PCR and western blot. The proliferation activity and invasion ability of 4 groups of cells were determined by methylthiazolyl tetrazolium (MTT) assay and invasion assay.Results (1) Real-time quantitive PCR technology showed: the level of HLA-G mRNA in the hypoxic inhibition group (0.220±0.050) was significantly different (P<0.05), when compared with that in the hypoxic control group (0.630±0.030) and normoxic inhibition group (0.400± 0.020). (2) Western blot analysis showed: the expression level of HLA-G protein in the hypoxic inhibition group was 0.260±0.010, statistically different from that in the hypoxic control group (0.850±0.100) and the normoxic inhibition group (0.560±0.020; P<0.05).(3) MTT showed: proliferative activity of JEG-3 cells in the normoxic inhibition group was 0.490 ± 0.070, the ability of cell proliferation was reduced. When compared with that in the normoxic control group (0.850±0.050), the differences was statistically significant (P<0.05). The proliferative activity of JEG-3 cells in the hypoxic inhibition group (0.330±0.070) was lower than that in the normoxic inhibition group (0.490±0.070), and there was a significant difference (P<0.05). (4) Invasion assay showed: compared with the normoxic control group (98±7), the invasive ability of JEG-3 cells in the normoxic inhibition group (73 ± 7) was weakened, and the difference was statistically significant (P<0.05). The number of transmembrane cells (52±11) of JEG-3 cells in the hypoxic inhibition group was lower than that in the hypoxic control group (72±7), and the difference was statistically significant (P<0.05). Compared with the normoxic inhibition group, the invasion ability of JEG-3 cells in the hypoxic inhibition group decreased, and the difference was statistically significant (P<0.05). Conclusion Under hypoxia, using siRNA technology to down-regulate the expression of HLA-G may affect the proliferation and invasion ability of trophoblast cells, which may be involved in the occurrence of hypertensive disorder of pregnancy.