Reduced contact-inhibition and substratum adhesion in epithelial cells expressing GlcNAc-transferase V.

Abstract

Abstract. Malignant transformation of fibroblast and epithelial cells is accompanied by increased 131-6 N-acetylglucosaminyltransferase V (GIcNAc-TV) activity, a Golgi N-linked oligosaccharide processing enzyme. Herein, we report that expression of GIcNAc-TV in MvlLu cells, an immortalized lung epithelial cell line results in loss of contact-inhibition of cell growth, an effect that was blocked by swainsonine, an inhibitor of Golgi processing enzyme et-mannosidase II. In serumdeprived and high density monolayer cultures, the GlcNAc-TV transfectants formed loci, maintained microfilaments characteristic of proliferating cells, and also experienced accelerated cell death by apoptosis. Injection of the GIcNAc-TV transfectants into nude mice produced a 50% incidence of benign tumors, and progressively growing tumors in 2:12 mice with a latency of 6 mo, while no growth was observed in mice injected with control cells. In short term adhesion assays, the GIcNAc-TV expressing cells were less adhesive on surfaces coated with fibronectin and collagen type IV, but no changes were observed in levels of cell surface a5131 or otv133 integrins. The larger apparent molecular weights of the LAMP-2 glycoprotein and integrin glycoproteins o~5, O~v and 131 in the transfected cells indicates that their oligosaccharide chains are substrates for GlcNAc-TV. The results suggest that 131--6GIcNAc branching of N-linked oligosaccharides contributes directly to relaxed growth controls and reduce substratum adhesion in premalignant epithelial cells. NLINI~D glycosylation of proteins begins in the lumen of the rough endoplasmic reticulum where a subset of Asn-X-Ser/Thr residues on newly synthesized proteins are subjected to substitution with Glc3-MangGlcNAc2. The oligosaccharides are then remodeled or processed as the newly synthesized glycoproteins are transported through the Golgi compartments en route to the cell surface (Kornfeld and Kornfeld, 1985;Schachter, 1986). Many of the glycosyltransferases and glycosidases that constitute the Golgi oligosaccharide processing pathways are regulated in a tissue-specific manner (Paulson et al., 1989). Their patterns of expression and acceptor specificity appear to be the basis for the plethora of oligosaccharide structures observed in secreted and membrane glycoproteins. For the complex-type N-linked oligosaccharides, structural diversity begins with GlcNAc-branching of the trimannosyl core and continues with a variety of glycosyltransferases that complete these antennae. The [31-6GlcNAc-linked antenna which is initiated by the action of 131--6 N-acetylglucosaminyltransferase V (GlcNAc-TV) 1

Variation in Carbohydrates between Cancer and Normal Cell Membranes Revealed by Super‐Resolution Fluorescence Imaging

“…Polyvalent interactions generally occur throughout biology, with the following functional advantages:27 it can provide a strong binding of ligands with modest or low surface area; it provides a graduated (graded) response to a biological signal via generating a broad range of signal strengths; it is able to obtain a great strength and specificity by heteromeric polyvalency of a mixture of ligand–receptor pairs; it can also induce macroscopic reorganizations of molecules or conformation of one or both of the interacting species; it has an ability to multiply an existing interaction or constructe a new one for biological evolution; it also serves as natural polyvalent inhibitors to prevent undesired interaction. Thus, according to the detailed functions of changed glycosylations in various cancer processes, including decreasing contact inhibition and substratum adhesion,28 increasing immigration,7 promoting the homotypic aggregation of cancer cells and the docking of tumor cells to endothelial cells,11 as well as the functional advantages of polyvalent interactions, we infer that the carbohydrates on cancer cell membranes could be reorganized to form larger clusters or more new clusters via polyvalent interactions with endogenetic lectins (i.e., galectins). In this way, carbohydrate ligands concentrate into large cluster to increase the regional density, which makes themselves easier to participate in interactions with extracellular matrix, homologous or heterogeneous cells, with higher affinity and specificity for CBPs.…”

“…Although alterations in complex O‐glycosylation, N‐glycosylation, and terminal carbohydrate structures were reported to most likely impact the survival and progression of neoplastic cells in some studies,28, 36, 37 no studies have investigated the detailed variations in the distribution of carbohydrates accompanied with tumorigenesis. Herein, based on the core structures of N‐linked and O‐linked oligosaccharides, we selected six common monosaccharides as the investigated targets.…”

N-acetylgalactosaminyl transferase-3 is a potential new marker for non-small cell lung cancers

“…Therefore, the biological importance of GalNAc-T3 expression depends on the function of target substrate glycoproteins. The importance of GalNAc-T3 expression for the development and progression of cancer as well as for maintaining physiologic properties of normal cells also remains to be determined, although certain cancer-associated decreases or increases in glycosylation has been shown to directly contribute to cellular transformation (Vavasseur et al, 1994;Demetriou et al, 1995). Collectively, decreased expression of GalNAc-T3 may directly contribute to altered biological properties of NSCLCs.…”

Differential expression of β mannosidase in human esophageal cancer

“…7,8 Expression of N-acetylglucosamine transferase (Glc NAc) in epithelial cells promotes loss of contact inhibition and metastasis. 9 To confirm the overexpression of ␤-mannosidase in ESCCs and to determine stage of esophageal cancer development at which upregulation of this enzyme occurs, its expression was analyzed in clinical specimens of ESCCs, dysplastic lesions and nonmalignant esophageal tissues by Reverse-Transcription Polymerase Chain Reaction (RT-PCR). To our knowledge, this is the first study showing overexpression of ␤-mannosidase in ESCCs.…”