Modulation of CD147-induced matrix metalloproteinase activity: role of CD147 N-glycosylation

Abstract

Degradation of the basement membrane by MMPs (matrix metalloproteinases) is one of the most critical steps in tumour progression. CD147 is a tumour-associated antigen that plays a key regulatory role for MMP activities. In the present study, mass spectrum analysis demonstrated that the purified native CD147 from human lung cancer tissue was N-glycosylated and contained a series of high-mannose and complex-type N-linked glycan structures. Moreover, native glycosylated CD147 existed exclusively as oligomers in solution and directly stimulated MMP production more efficiently than non-glycosylated prokaryotic CD147. The glycosylation site mutation results indicated that, among three N-glycan attachment sites, the N152Q mutants were retained in the endoplasmic reticulum and unfolded protein response signalling was activated. This improper intracellular accumulation impaired its MMP-inducing activity. Increased β1,6-branching of N-glycans as a result of overexpression of GnT-V (N-acetylglucosaminyltransferase V) plays an important role in tumour metastasis. In the present study, we identified CD147 as a target protein of GnT-V and found that overexpression of GnT-V resulted in an elevated level of CD147 at the plasma membrane and in cell-conditioned medium, thereby increasing the induction of MMPs. The present study reveals the important role of N-glycosylation of CD147 in its biological function and implied that targeting aberrant β1,6-branching of N-glycans on CD147 would be valuable for the development of novel therapeutic modalities against carcinoma.