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

Gangli Liu,Pritam K Sengupta,Basem Jamal,Hsiao-Ying Yang,Meghan P Bouchie,Volkhard Lindner,Xaralabos Varelas,Maria A Kukuruzinska

doi:10.1074/jbc.m113.473785

Abstract

Oral squamous cell carcinoma (OSCC) is one of the most pernicious malignancies, but the mechanisms underlying its development and progression are poorly understood. One of the key pathways implicated in OSCC is the canonical Wnt/β-catenin signaling pathway. Previously, we reported that canonical Wnt signaling functions in a positive feedback loop with the DPAGT1 gene, a principal regulator of the metabolic pathway of protein N-glycosylation, to hyperglycosylate E-cadherin and reduce intercellular adhesion. Here, we show that in OSCC, DPAGT1 and canonical Wnt signaling converge to up-regulate CTHRC1 (collagen triple helix repeat containing 1), an N-glycoprotein implicated in tumor invasion and metastasis. We found that in human OSCC specimens, amplification of the levels of CTHRC1 was associated with its hyperglycosylation. Partial inhibition of DPAGT1 expression in OSCC CAL27 cells reduced CTHRC1 abundance by increasing protein turnover, indicating that N-glycosylation stabilizes CTHRC1. Additionally, canonical Wnt signaling promoted β-catenin/T-cell factor transcriptional activity at the CTHRC1 promoter to further elevate CTHRC1 levels. We demonstrate that DPAGT1 promotes cell migration and drives the localization of CTHRC1 to cells at the leading edge of a wound front coincident with drastic changes in cell morphology. We propose that in OSCC, dysregulation of canonical Wnt signaling and DPAGT1-dependent N-glycosylation induces CTHRC1, thereby driving OSCC cell migration and tumor spread.

Highlights

Increased protein N-glycosylation and aberrant Wnt signaling are features of oral cancer
Augmented DPAGT1 Levels in Human Oral squamous cell carcinoma (OSCC) Specimens Are Associated with Up-regulation of CTHRC1 Expression—Previously, we reported that aberrantly amplified DPAGT1 leads to hyperglycosylation of E-cadherin and reduced intercellular adhesion [6, 20]
We examined the expression and localization of the protein encoded by the DPAGT1 gene (GPT), a canonical Wnt effector (␤-catenin), and a pro-migratory N-glycoprotein (CTHRC1) in nine moderately to poorly differentiated human OSCC tongue tumor specimens and corresponding cytologically normal adjacent epithelia (AE)

Summary

Background

Increased protein N-glycosylation and aberrant Wnt signaling are features of oral cancer. Whole-exome sequencing studies have identified components of signaling pathways whose aberrant expression and/or activity has been linked to head and neck squamous cell carcinoma pathogenesis [4, 5], there is a critical need for a better understanding of the molecular events that drive early stages of its development and progression. We reported that OSCC specimens display an aberrantly amplified DPAGT1/canonical Wnt feedback loop [6], where overexpression of DPAGT1 is due to increased occupancy of ␤-catenin at the DPAGT1 promoter This leads to hyperglycosylation of E-cadherin and reduced intercellular adhesion, resulting in a continuous activation of N-glycosylation and canonical Wnt signaling. Our studies show that in OSCC, CTHRC1 is up-regulated by the amplified DPAGT1/canonical Wnt feedback loop We propose that this aberrant up-regulation of CTHRC1 drives OSCC tumor cell migration and the subsequent invasion and metastasis

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION