Glycosylation of tetraspanin Tspan-1 at four distinct sites promotes its transition through the endoplasmic reticulum.

We showed that Tspan-1, a tetraspanin overexpressed in many human cancers, harbours oligosaccharides at all four potential N-glycosylation sites. Its most abundant form contained only mannose-rich sugar chains but two distinct glycosylation sites could also contain complex carbohydrates. Glycosylation seemed to be required for correct folding and subsequent transition through the endoplasmic reticulum.