Identification of N-glycoproteins of hip cartilage in patients with osteonecrosis of femoral head using quantitative glycoproteomics.

N-glycosylation is a major post-translational modification of proteins and involved in many diseases, however, the state and role of N-glycosylation in cartilage degeneration of osteonecrosis of femoral head (ONFH) remain unclear. The aim of this study is to identify the glycoproteins of ONFH hip cartilage. Cartilage tissues were collected from nine patients with ONFH and nine individuals with traumatic femoral neck fracture. Cartilage glycoproteins were identified by glycoproteomics based on LC-MS/MS. The differentially N-glycoproteins including glycosites were identified in ONFH and controls. A total of 408 N-glycoproteins with 444 N-glycosites were identified in ONFH and control cartilage. Among them, 104 N-glycoproteins with 130 N-glycosites were significantly differential in ONFH and control cartilage, which including matrix-remodeling-associated protein 5, prolow-density lipoprotein receptor-related protein 1, clusterin and lysosome-associated membrane glycoprotein 2. Gene Ontology analysis revealed the significantly differential glycoproteins mainly belonged to protein metabolic process, single-multicellular organism process, proteolysis, biological adhesion and cell adhesion. KEGG pathway and protein-protein interaction analysis suggested that the significantly differential glycoproteins were associated with PI3K-Akt signalling pathway, ECM-receptor interaction, protein processing in the endoplasmic reticulum and N-glycan biosynthesis. This information provides substantial insight into the role of protein glycosylation in the development of cartilage degeneration of ONFH patients.