Regulation of plasma-membrane-associated sialidase NEU3 gene by Sp1/Sp3 transcription factors

Abstract

Gene expression of the human plasma membrane-associated sialidase (NEU3), a key enzyme for ganglioside degradation, is relatively high in brain and is modulated in response to many cellular processes, including neuronal cell differentiation and tumorigenesis. We demonstrated previously that NEU3 is markedly up-regulated in various human cancers and showed that NEU3 transgenic mice developed a diabetic phenotype and were susceptible to azoxymethane-induced aberrant crypt foci in their colon tissues. These results suggest that appropriate control of NEU3 gene expression is required for homoeostasis of cellular functions. To gain insights into regulation mechanisms, we determined the gene structure and assessed transcription factor involvement. Oligo-capping analysis indicated the existence of alternative promoters for the NEU3 gene. Transcription started from two clusters of multiple TSSs (transcription start sites); one cluster is preferentially utilized in brain and another in other tissues and cells. Luciferase reporter assays showed further that the region neighbouring the two clusters has promoter activity in the human cell lines analysed. The promoter lacks TATA, but contains CCAAT and CAAC, elements, whose deletions led to a decrease in promoter activity. Electrophoretic mobility-shift assays and chromatin immunoprecipitation demonstrated binding of transcription factors Sp (specificity protein) 1 and Sp3 to the promoter region. Down-regulation of the factors by siRNAs (short interfering RNAs) increased transcription from brain-type TSSs and decreased transcription from other TSSs, suggesting a role for Sp1 and Sp3 in selection of the TSSs. These results indicate that NEU3 expression is diversely regulated by Sp1/Sp3 transcription factors binding to alternative promoters, which might account for multiple modulation of gene expression.

Molecular subtyping of metastatic melanoma based on cell ganglioside metabolism profiles

“…The increase of the expression of these two enzymes was reasonably induced by the enhanced expression of the transcriptional factors Sp1 (average increase: 100%, melanoma cells versus adult melanocytes; P < 0.001) (Figure 6C), as it was reported that both NEU3 [42] and GD3 synthase gene promoters [43] are regulated by them. NEU 3 was the unique sialidase to be over-expressed by melanoma cells; lysosomal sialidase NEU1 expression varied inconsistently among melanoma cell lines and melanocytes; cytosolic sialidase NEU2 was not expressed in both melanocytes and melanoma cells; sialidase NEU4 appeared to be down-regulated in all melanoma cells except L1, L34, L39, L40, in comparison to melanocytes.…”

Plasma membrane-associated sialidase (NEU3) regulates progression of prostate cancer to androgen-independent growth through modulation of androgen receptor signaling

“…NEU3 upregulation may trigger off activation of AR pathway probably via EGFR family followed by ERK activation, leading to transcriptional activation of NEU3 itself by SP1 transcription factor in positive feedback loop, as Sp1 is phosphorylated by ERK and NEU3 is an SP1 target gene. 29 NEU3 gene silencing with siRNA suppresses prostate cancer growth. To investigate the effects of siRNAmediated NEU3 silencing on prostate cancer growth and survival, NEU3 siRNA was introduced into the cells and xenografts.…”

“…We do not know the detailed mechanism of the NEU3-mediated upregulation at present. However, our recent studies suggest the possibility that NEU3 undergoes transcriptional activation by SP1 transcription factor, 29 which is positively regulated by several kinases including ERK 32 and involved in transcriptional regulation of genes implicated in cell growth and tumorigenesis including EGFR. 33 As proposed in Figure 5d, NEU3 upregulation may give rise to the increased expression of NEU3 itself and EGFR family by activating ERK and then SP1 in positive feedback loop.…”

Neuraminidase-1: A novel therapeutic target in multistage tumorigenesis

“…Neu3 could be involved in melanoma malignancy by decreasing the levels of Neu5Ac-GM3. Indeed, Yamaguchi et al have reported evidence to support plasma-membrane-associated NEU3 gene regulated by Sp1/Sp3 transcription factors [142]. …”