Inhibition of Asparagine-linked Glycosylation Participates in Hypoxia-induced Down-regulation of Cell-surface MICA Expression.

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.