Overexpression of DPAGT1 Leads to Aberrant N-Glycosylation of E-Cadherin and Cellular Discohesion in Oral Cancer

Abstract

Cancer cells are frequently characterized by aberrant increases in protein N-glycosylation and by disruption of E-cadherin-mediated adherens junctions. The relationship between altered N-glycosylation and loss of E-cadherin adhesion in cancer, however, remains unclear. Previously, we reported that complex N-glycans on the extracellular domains of E-cadherin inhibited the formation of mature adherens junctions. Here, we examined whether dysregulated N-glycosylation was one of the underlying causes for cellular discohesion in oral cancer. We show that dense cultures of human salivary epidermoid carcinoma A253 cells exhibited elevated expression of DPAGT1, the gene that initiates protein N-glycosylation. Overexpression of DPAGT1 correlated with the production of E-cadherin-bearing complex N-glycans in nascent adherens junctions. Partial inhibition of DPAGT1 with small interfering RNA reduced the complex N-glycans of E-cadherin and increased the abundance of A-catenin and stabilizing proteins in adherens junctions. This was associated with the assembly of functional tight junctions. The inverse relationship between DPAGT1 expression and intercellular adhesion was a feature of oral squamous cell carcinoma. Oral squamous cell carcinomas displayed overexpression of DPAGT1 that correlated with diminished localization of E-cadherin and A-catenin at the sites of adherens junctions. Our studies show for the first time that DPAGT1 is an upstream regulator of E-cadherin N-glycosylation status and adherens junction composition and suggest that dysregulation of DPAGT1 causes disturbances in intercellular adhesion in oral cancer.

N-Glycosylation Induces the CTHRC1 Protein and Drives Oral Cancer Cell Migration

“…Associated with Up-regulation of CTHRC1 Expression-Previously, we reported that aberrantly amplified DPAGT1 leads to hyperglycosylation of E-cadherin and consequently reduced intercellular adhesion (6,20). Recent studies have identified an N-glycoprotein, CTHRC1, as a key regulator of cell motility in cancer (25,26).…”

Coordinate regulation of N-glycosylation gene DPAGT1, canonical Wnt signaling and E-cadherin adhesion

“…The Nglycosylation status of E-cadherin has been shown to regulate the molecular organization and cytoskeletal association of Ecadherin protein complexes, known as adherens junctions (AJs) (Jamal et al, 2009;Liwosz et al, 2006;Nita-Lazar et al, 2009;Nita-Lazar et al, 2010). Increased DPAGT1 expression is associated with extensive N-glycosylation of E-cadherin, which precludes its interaction with stabilizing proteins and with the cytoskeleton and promotes the formation of nascent AJs in proliferating and cancer cells (Liwosz et al, 2006;Nita-Lazar et al, 2009;Nita-Lazar et al, 2010). In contrast, downregulation of DPAGT1 expression leads to reduced N-glycosylation of Ecadherin, which is required for the formation of mature AJs in dense cultures and differentiated cells (Nita-Lazar et al, 2010;Vagin et al, 2008).…”

“…Accordingly, partial inhibition of DPAGT1 with siRNA results in the production of hypoglycosylated Ecadherin, which organizes mature AJs. In cancer cells, downregulation of DPAGT1 has been shown to reverse their mesenchymal phenotype to an epithelial morphology (Jamal et al, 2012;Nita-Lazar et al, 2009). Likewise, the hypoglycosylated E-cadherin mutant, V13, generated by the deletion of the major complex and high mannose/hybrid Nglycan addition sites, has been shown to form mature AJs in Chinese Hamster Ovary (CHO) cells lacking endogenous Ecadherin (Liwosz et al, 2006).…”

N-Glycosylation Regulates ADAM8 Processing and Activation

“…Altered N-glycosylation of proteins has been linked to cancer progression (24,25). Notably, N-glycosylation participates in the adherence of circulating tumor cells to the microvascular bed essential for extravasation and facilitates metastasis from the blood or lymph to other organs (26).…”