Death receptor O-glycosylation controls tumor-cell sensitivity to the proapoptotic ligand Apo2L/TRAIL

Apo2L/TRAIL stimulates cancer-cell death through the proapoptotic receptors DR4 and DR5, but the determinants of tumor susceptibility to this ligand are not fully defined. mRNA expression of the peptidyl O-glycosyl transferase GALNT14 correlated with Apo2L/TRAIL sensitivity in pancreatic carcinoma, non-small cell lung carcinoma and melanoma cell lines (P < 0.00009; n=83), and up to 30% of samples from various human malignancies displayed GALNT14 overexpression. RNA interference of GALNT14 reduced cellular Apo2L/TRAIL sensitivity, whereas overexpression increased responsiveness. Biochemical analysis of DR5 identified several ectodomain O-GalNAc-Gal-Sialic acid structures. Sequence comparison predicted conserved extracellular DR4 and DR5 O-glycosylation sites; progressive mutation of the DR5 sites attenuated apoptosis signaling. O-glycosylation promoted ligand-stimulated clustering of DR4 and DR5, which mediated recruitment and activation of the apoptosis-initiating protease caspase-8. These results uncover a novel link between death receptor O-glycosylation and apoptosis signaling, providing potential predictive biomarkers for Apo2L/TRAIL-based cancer therapy.

119

Wagner KW, Punnoose EA, Januario T, Lawrence DA, Pitti RM, Lancaster K, Lee D, von Goetz M, Yee SF, Totpal K, Huw L, Katta V, Cavet G, Hymowitz SG, Amler L, Ashkenazi A