β1,4-Galactosyltransferase V Functions as a Positive Growth Regulator in Glioma

Abstract

␤1,4-galactosyltransferase V (GalT V; EC 2.4.1.38) can effectively galactosylate the GlcNAc␤13 6Man arm of the highly branched N-glycans that are characteristic of glioma. Previously, we have reported that the expression of GalT V is increased in the process of glioma. However, currently little is known about the role of GalT V in this process. In this study, the ectopic expression of GalT V could promote the invasion and survival of glioma cells and transformed astrocytes. Furthermore, decreasing the expression of GalT V in glioma cells promoted apoptosis, inhibited the invasion and migration and the ability of tumor formation in vivo, and reduced the activation of AKT. In addition, the activity of GalT V promoter could be induced by epidermal growth factor, dominant active Ras, ERK1, JNK1, and constitutively active AKT. Taken together, our results suggest that GalT V functioned as a novel glioma growth activator and might represent a novel target in glioma therapy.The carbohydrate moieties of cell surface glycoconjugates play an important role in cell adhesion and metastasis (1). One of the most prominent transformation-associated changes in the sugar chains of glycoproteins is an increase in the large N-glycans of cell surface glycoprotein (2). ␤1,4-galactosyltransferase (GalT) 2 family are the enzymes responsible for the biosynthesis of N-acetyllactosamine on N-glycans by transferring UDP-galactose to the terminal N-acetylglusamine (N-GlcNAc) residues, and this family consist of seven members, from GalT I to GalT VII (3,4).GalT V, a member of ␤1,4-galactosyltransferase (GalT) family, could effectively galactosylate the GlcNAc␤136 branch (5), which is a marker of glioma (6). The expression change of GalT V has been investigated using NIH3T3 and the highly malignant transformed cell line MTAg. Northern blot analysis has revealed that the transcript of GalT V gene increases by 2-3-fold in the transformed cells (7). Similar results have been obtained in several human cancer cell lines (8). Consistently, our previous study has shown that the expression of GalT V is increased in the process of glioma development, with the highest level in grade IV glioma (9). Despite this knowledge, currently little is known about the role of GalT V in the process of glioma formation.The experiments reported here were undertaken to further study the role of GalT V in glioma malignancy, including cell migration, invasion, growth, and survival. Our results indicate that GalT V functioned as a novel glioma growth activator and could represent a novel target in glioma therapy. EXPERIMENTAL PROCEDURESMaterials-Restriction enzymes, bovine calf serum, fetal bovine serum (FBS), DMEM, RPMI 1640 medium, and TRIzol reagent were from Invitrogen. G418, phenylmethylsulfonyl fluoride, aprotinin, pepstatin, epidermal growth factor (EGF), etoposide (VP16), and toluidine blue O were from Sigma. [␥-32 P]dATP and the ECL assay kit were from Amersham Biosciences. Sialidase was from Roche Applied Science. The following antibodies were purchased from Sa...

regulation of the invasion and metastasis of human glioma cells by polypeptide N-acetylgalactosaminyltransferase 2

“…For example, Jiang and Gu present evidence that β1,4GalT V functions as a positive growth regulator in glioma. β1,4GalT V regulates the invasion, and growth in vivo and in vitro of glioma cells (22). Yamamoto et al confirmed that the overexpression of GnT-V in gliomas led to an increased invasiveness of these tumor cells in vitro (23).…”

“…Yamamoto et al confirmed that the overexpression of GnT-V in gliomas led to an increased invasiveness of these tumor cells in vitro (23). In addition, the knockdown of GalTase V produced enhanced expression of cell surface integrin β1 resulting in increased adhesion to fibronectin and suppression of tumor development and metastatic potential in experimental animals (24,25). Therefore, to investigate the roles of such glycosyltransferases may provide insight into our understanding of tumor biology.…”

Functional Interaction of E1AF and Sp1 in Glioma Invasion

“…Expression constructs for HA-pcDNA3.0, pcDNA3.1-myc, pcDNA3.0-E1AF, pGL3-Basic, pRL-CMV, GalT V promoter construct GalT V-Luc, and M(Sp1) have been described previously (20,49,50). The Sp1-Luc, mSp1-Luc, CDK2-Luc, mCDK2-Luc, hSR-Luc, mhSR-Luc, Ap2␥-Luc, and mAp2␥-Luc vectors were constructed as previously described (27,31,40,44).…”

“…Human glioma cell lines U251 and SHG44 have been described previously (20). Cell transfection was performed with Lipofectamine 2000 (Invitrogen) according to the manufacturer's instructions.…”

“…It binds to GC box motifs in promoters of numerous genes involved in cell growth regulation and cancer (7), including p21 (14), caspase-8 (28), cyclin D1, and GalT V (35, 47), which effectively galactosylates the GlcNAc␤1,6 branch of N-glycans and functions as a positive regulator in glioma invasion (9,16,20). Biologically, Sp1 plays important roles in a wide variety of physiological processes, including the cell cycle, hormonal activation, apoptosis, angiogenesis, oncogenesis, etc.…”