N- and O-linked Glycosylation of TSR6 Promotes Efficient Secretion of ADAMTSL2

Abstract

Mutations in ADAMTSL2 (a disintegrin and metalloproteinase with thrombospondin repeats-like 2) are known to cause secretion defects, leading to geleophysic dysplasia. One mutation, G811R, is within the consensus sequence for O-fucosylation of TSR6. Interestingly, this site also contains an N-glycosylation site. It is not known whether TSR6 is modified with O-fucose or N-glycans. We hypothesized that the secretion defect of the G811R mutation is caused by an alteration in glycosylation of TSR6. Using site directed mutagenesis and secretion assays, we demonstrated that mutations in the predicted N-linked glycosylation site or O-fucosylation site resulted in a significant decrease in protein secretion. Interestingly, when both glycosylation sites were eliminated, secretion levels were similar to N807Q or T809V. Together these findings suggest that amino acid substitutions in the N-linked glycosylation site or N-fucoyslation site, predicted to interfere with glycosylation in TSR6, could contribute to the Geleophysic dysplasia phenotype.