Fig. 2
From: Understanding the matrix: collagen modifications in tumors and their implications for immunotherapy
Schematic overview of collagen post-translational modifications. Hydroxylation of proline and lysine takes place in the endoplasmic reticulum while N-linked glycosylation and O-linked glycosylation of hydroxylysine take place in the endoplasmic Reticulum and golgi apparatus, respectively. The collagen triple helix is formed intracellularly and in most subtypes of collagen N- and C-propeptides are cleaved off after secretion before the collagen can be crosslinked to form collagen fibers. Collagen can also be modified by citrullination or phosphorylation. During collagen remodeling, collagen is normally degraded while in cancer also fragmentation can take place leaving collagen fragments in the circulation [2]