Human Fibroblasts with Mutations in COL5A1 and COL3A1 Genes Do Not Organize Collagens and Fibronectin in the Extracellular Matrix, Down-regulate

Dermal fibroblasts derived from types I and IV EhlersDanlos syndrome (EDS) patients, carrying mutations in COL5A1 and COL3A1 genes, respectively, synthesize aberrant types V and III collagen (COLL) and show defective organization of these proteins into the extracellular matrix (ECM) and high reduction of their functional receptor, the 2 1 integrin, compared with control fibroblasts. EDS cells also show reduced levels of fibronectin (FN) in the culture medium and lack an FN fibrillar network. Finally, EDS cells prevalently organize v 3 integrin instead of 5 1 integrin. The v 3 integrin, distributed on the whole EDS cell surface, shows FN binding and assembly properties when the cells are treated with purified FN. Treatment of EDS cells with purified COLLV or COLLIII, but not with FN, restores the control phenotype (COLL , FN , v 3 , 5 1 , 2 1 ). Functionblocking antibodies to COLLV, COLLIII, or 2 1 integrin induce in control fibroblasts an EDS-like phenotype (COLL , FN , v 3 , 5 1 , 2 1 ). These results show that in human fibroblasts 2 1 integrin organization and function are controlled by its ligand, and that the 2 1-COLL interaction, in turn, regulates FN integrin receptor recruitment: high 2 1 integrin levels induce 5 1 integrin organization, while low 2 1 integrin levels lead to v 3 integrin organization.