Background/aim: Hypoxia down-regulates the expression of cell surface major histocompatibility class I-related chain molecule A (MICA) without increasing its shedding. Recently, the inhibition of N-linked glycosylation was also shown to reduce the cell-surface expression of MICA. We investigated the participation of asparagine (Asn)-linked glycosylation in hypoxia-induced down-regulation of cell-surface MICA using osteosarcoma cells.
Materials and methods: The cell-surface expression and Asn-N-glycosylation of MICA were estimated by flow cytometry, and western blot analyses, respectively.
Results: Hypoxia reduced the expression of N-linked glycosylated MICA, as well as the ratio of N-linked glycosylated to non-glycosylated MICA. 2-Deoxy-D-glucose, which inhibits N-linked glycosylation, reduced the cell-surface expression of MICA under normoxia, while D-Mannose increased N-glycosylated MICA, increasing cell-surface MICA under hypoxia. Cells transfected with wild-type MICA expression vector expressed cell surface MICA more than those transfected with mutant MICA expression vectors designed for abrogation of N-linked glycosylation.
Conclusion: The inhibition of Asn-N-linked glycosylation participates in hypoxia-induced down-regulation of cell-surface expression of MICA.
Keywords: Hypoxia; MICA; NKG2D ligand; glycosylation; osteosarcoma.
Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.