Curcumin Downregulates Human GM3 Synthase (hST3Gal V) Gene Expression with Autophagy Induction in Human Colon Carcinoma HCT116 Cells

Our recent report showed that curcumin, polyphenolic compound isolated from the herb Curcuma longa, upregulated the gene expression of human GD3 synthase (hST8Sia I) responsible for ganglioside GD3 synthesis with autophagy induction in human lung adenocarcinoma A549 cells. In this study, on the contrary to this finding, we demonstrated that curcumin downregulated the gene expression of human GM3 synthase (hST3Gal V) catalyzing ganglioside GM3 synthesis with autophagy induction in human colon carcinoma HCT116 cells. To clarify the mechanism leading to the downregulation of hST3Gal V gene expression in curcumin-treated HCT116 cells, we analyzed the curcumin-inducible promoter of the hST3Gal V gene by luciferase reporter assays. Promoter deletion analysis demonstrated that the -177 to -83 region, which includes putative binding sites for transcription factors NFY, CREB/ATF, SP1, EGR3, and MZF1, acts as the curcumin-responsive promoter of the hST3Gal V gene. Site-directed mutagenesis and chromatin immunoprecipitation analysis demonstrated that the CREB/ATF binding site at -143 is pivotal for curcumin-induced downregulation of hST3Gal V gene in HCT116 cells. The transcriptional activation of hST3Gal V in HCT116 cells was significantly repressed by an inhibitor of AMP-activated protein kinase (AMPK). These results suggest that AMPK signal pathway mediates hST3Gal V gene expression in HCT116 cells.