Mechanism for Decreased Gene Expression of β4-Galactosyltransferase 5 upon Differentiation of 3T3-L1 Mouse Preadipocytes to Adipocytes

Transcriptional Mechanism of the Mouse β4-Galactosyltransferase 6 Gene in Mouse Neuroblastoma Cell Line Neuro-2a

Lactosylceramide (Lac-Cer) constitutes the backbone structure of various gangliosides whose abnormal expression is associated with malignancy of neuroblastoma. The understanding of the regulatory mechanism of Lac-Cer contributes to the development of neuroblastoma therapy. In this study, the transcriptional mechanism of mouse β4-galactosyltransferase (β4GalT) 6, which is one of Lac-Cer synthase, was analyzed using mouse neuroblastoma cell line Neuro-2a. The -226 to -13 region relative to the most downstream transcriptional start site was determined to be the promoter region by luciferase assay using the 5'-deletion constructs. The mutation into the activating protein (AP) 4-binding site -110/-101 drastically decreased the promoter activity, indicating that this site is mainly implicated in the transcription. Furthermore, the mutation into the GATA-binding site -210/-201 or another AP4-binding site -202/-193 partially decreased the promoter activity. The study suggests that the mouse β4GalT6 gene is transcriptionally regulated by AP4 in cooperation with GATA family transcription factor in neuroblastoma.

An embeddable molecular code for Lewis X modification through interaction with fucosyltransferase 9

N-glycans are diversified by a panel of glycosyltransferases in the Golgi, which are supposed to modify various glycoproteins in promiscuous manners, resulting in unpredictable glycosylation profiles in general. In contrast, our previous study showed that fucosyltransferase 9 (FUT9) generates Lewis X glycotopes primarily on lysosome-associated membrane protein 1 (LAMP-1) in neural stem cells. Here, we demonstrate that a contiguous 29-amino acid sequence in the N-terminal domain of LAMP-1 is responsible for promotion of the FUT9-catalyzed Lewis X modification. Interestingly, Lewis X modification was induced on erythropoietin as a model glycoprotein both in vitro and in cells, just by attaching this sequence to its C-terminus. Based on these results, we conclude that the amino acid sequence from LAMP-1 functions as a “Lewis X code”, which is deciphered by FUT9, and can be embedded into other glycoproteins to evoke a Lewis X modification, opening up new possibilities for protein engineering and cell engineering.

A 29-amino acid sequence in the N-terminal domain of LAMP-1 promotes its Lewis X glycosylation and is embeddable to other proteins for Lewis X glycoengineering.

Heat Shock Cognate Protein 70 Enhanced Integrin β1 Mediated Invasion in Cancer Cells

Purpose

Glioblastoma is one of the most common malignant cancers worldwide. In our previous work, we have shown that heat shock cognate protein 70 (Hsc70) functions as a positive growth regulator in glioma. We investigated the role of Hsc70 in integrin β1 mediated invasion of glioma cells.

Methods

In order to investigate whether the down-regulation of Hsc70 would affect the expression of integrin β1 subunit, HeLa cells were transiently transfected with Hsc70-AS or pcDNA3.0 vectors and the down-regulation of Hsc70 was confirmed by Western blotting. Human brain glioma U87 cells were stably transfected with Hsc70-AS or pcDNA3.0 vectors to further elucidate the relationship between Hsc70 and integrin β1 in human glioma cells. Cellular localization of integrin β1 was detected using immunofluorescence confocal microscopy analysis.

Results

Here we reported that down-regulation of the expression of Hsc70 in U87 cells by transfection with antisense cDNA specifically increased the expression of cell surface integrin β1 without changing its mRNA. Meanwhile, the integrin β1 125-kD mature form increased while 105-kD precursor form decreased when Hsc70 was down-regulated. Mechanically, the U87 cells transfected with antisense cDNA of Hsc70 decreased the Golgi localization of integrin β1, strengthened its interaction with integrin α5 subunit, and enhanced the adhesion ability to fibronectin (FN) and the phosphorylation level of focal adhesion kinase (FAK).

Conclusion

Overall, these results suggested that the down-regulation of Hsc70 expression could promote the expression of cell surface integrin β1 and subsequently inhibit glioma invasion phenotype.