Tendinopathy is a disease with surging prevalence. Lacking understanding of molecular mechanisms impedes the development of therapeutic approaches and agents. Lysine lactylation (Kla) is a newly discovered post-translational modification related to glycolysis. It has long been noted that manipulation of glycolysis metabolism could affect tendon cell function, tendon homeostasis, and healing process of tendon. However, protein lactylation sites in tendinopathy remain unexplored. Here, we conducted the first proteome-wide Kla analysis in tendon samples harvested from patients with rotator cuff tendinopathy (RCT), which identified 872 Kla sites across 284 proteins. Compared with normal counterparts, 136 Kla sites on 77 proteins were identified as upregulated in the pathological tendon, while 56 sites on 32 proteins were downregulated. Function enrichment analysis demonstrated that the majority of proteins with upregulated Kla levels functioned in organization of the tendon matrix and cholesterol metabolism, accompanied by lower expression levels which meant impaired cholesterol metabolism and degeneration of the tendon matrix, indicating potential cross-talk between protein lactylation and expression levels. At last, by western blotting and immunofluorescence, we verified the correlation between high lactylation and the downregulation of matrix and cholesterol-related proteins including BGN, MYL3, TPM3, and APOC3. ProteomeXchange: PXD033146.
Keywords: cholesterol metabolism; lactylation; matrix; proteomics; tendinopathy.