ABSTRACT
Objective To construct a eukaryotic expression plasmid carrying the PKCI-1/HINT1 gene,to investigate its expression in A375 melanoma cells after transfection,and to evaluate its effects on apoptosis and autophagy of A375 cells.Methods The PKCI-1/HINT1 gene sequence was amplified by reverse transcription PCR (RT-PCR) with total RNA extracted from A375 cells as the template,then inserted into the eukaryotic expression plasmid PCDNA3.1 (+) to construct a recombinant plasmid,PCDNA3.1 (+)-PKCI-1/HINT1.Some A375 cells were classified into two groups to be transiently transfected with the recombinant plasmid (PCDNA3.1 (+)-PKCI-1/HINT1 group) or the empty plasmid PCDNA3.1 (+) (control group).After additional 48-hour culture,RT-PCR and Western blot analysis were performed to quantify the mRNA and protein expressions of PKCI-1/HINT1 respectively,Hoechst 33342 staining was conducted to detect apoptosis of A375 cells,Western blot analysis to detect the expressions of intracellular caspase-3 and autophagy-associated protein beclin1,and cell autophagy was observed by using the green fluorescent protein (GFP)-microtubule-associated protein 1 light chain 3 (LC3) labelling method combined with confocal laser scanning microscopy.Methyl thiazolyl tetrazolium (MTT) assay was performed to evaluate the proliferative activity of A375 cells at 24,48,72 and 96 hours after transfection.Results Enzyme digestion and sequencing analysis confirmed that the eukaryotic expression plasmid PCDNA3.1 (+)-PKCI-1/HINT1 was successfully constructed and effectively expressed in the transfected A375 cells.MTT assay showed that PKCI-1/HINT1 could obviously inhibit the proliferation of A375 cells,and the number of live cells was decreased by 17.0％,25.6％ and 29.4％ in the PCDNA3.1 (+)-PKCI-1/HINT1 group at 48,72 and 96 hours,respectively,compared with the control group (all P ＜ 0.05).Hoechest 33258 staining revealed that PKCI-1/HINT1 could promote the formation of apoptotic bodies in A375 cells.Confocal laser scanning microscopy demonstrated that the overexpression of PKCI-1/HINT1 increased GFP-LC3 puncta formation in A375 cells.In addition,Western blot analysis indicated that PKCI-1/HINT1 up-regulated the protein expressions of caspase-3 and beelin1 in A375 cells.Conclusions The eukaryotic expression plasmid PCDNA3.1 (+)-PKCI-1/HINT1 was successfully constructed,and PKCI-1/HINT1 could be effectively expressed in A375 cells.High-level expression of PKCI-1/HINT1 could suppress cellular proliferation,promote apoptosis,and induce autophagy,of A375 cells.
ABSTRACT
PURPOSE: The human genetic disorder ataxia-telangiectasia (AT) is a multisystem disease characterized by extreme radiosensitivity. The recent identification of the gene mutated in AT, ATM, and the demonstration that it encodes a homologous domain of phosphatidylinositol 3-kinase (PI3-K), the catalytic subunit of an enzyme involved in transmitting signals from the cell surface to the nucleus, provide support for a role of this gene in signal transduction. Although ionizing radiation was known to induce c-fos transcription, nothing is known about how ATM or PKCI mediated signal transduction pathway modulates the c-fos gene transcription and gene expression. Here we have studied the effect of PKCI on radiation sensitivity and c-fos transcription in normal and AT cells. MATERIALS AND METHODS: Normal (LM217) and AT (AT5BIVA) cells were transfected with PKCI expression plasmid and the overexpression and integration of PKCI was evaluated by northern blotting and polymerase chain reaction, respectively. 5 Gy of radiation was exposed to LM and AT cells transfected with PKCI expression plasmid and cells were harvested 48 hours after radiation and investigated apoptosis with TUNEL method. The c-fos transcription activity was studied by performing CAT assay of reporter gene after transfection of c-fos CAT plasmid into AT and LM cells. RESULTS: Our results demonstrate for the first time a role of PKCI on the radiation sensitivity and c-fos expression in LM and AT cells. PKCI increased radiation induced apoptosis in LM cells but reduced apoptosis in AT cells. The basal c-fos transcription activity is 70 times lower in AT cells than that in LM cells. The c-fos transcription activity was repressed by overexpression of PKCI in LM cells but not in AT cells. After induction of c-fos by Ras protein, overexpression of PKCI repressed c-fos transcription in LM cells but not in AT cells CONCLUSION: Overexpression of PKCI increased radiation sensitivity and repressed c-fos transcription in LM cells but not in AT cells. The results may be a reason of increased radiation sensitivity of AT cells. PKCI may be involved in an ionizing radiation induced signal transduction pathway responsible for radiation sensitivity and c-fos transcription. The data also provided evidence for novel transcriptional difference between LM and AT cells.