FibronectinTyp

FibronectinTyp refers to the fibronectin protein family and, in particular, the modular arrangement of fibronectin that comprises three general types of repeating domains: type I (FNI), type II (FNII), and type III (FNIII). Fibronectin is a high‑molecular‑weight glycoprotein found in plasma and the extracellular matrix, where it supports cell adhesion, migration, and tissue organization.

The fibronectin molecule is built from multiple repeats of FNI, FNII, and FNIII domains. Type I repeats contribute to self‑assembly and interactions with collagen, type II repeats participate in collagen association, and type III repeats form a large, versatile surface. A key feature is the RGD sequence located in FNIII domain 10, which, together with the adjacent PHSRN synergy sequence in FNIII9, enables binding to integrin receptors such as α5β1, facilitating cell attachment. The domains are encoded by the FN1 gene and can be included or skipped via alternative splicing to generate different isoforms.

Isoforms include plasma fibronectin, produced mainly by the liver and circulating in blood, and cellular (tissue) fibronectin, produced by fibroblasts and other cells. In cellular fibronectin, exons encoding the extra type III domains EDA and EDB may be included or excluded, altering adhesion properties, growth factor interactions, and matrix assembly.

Functionally, fibronectin participates in extracellular matrix assembly by polymerizing into fibrils, mediating cell attachment, and coordinating interactions with collagen, heparin, and fibrin. It plays essential roles in development, wound healing, angiogenesis, and tissue remodeling. Dysregulation of fibronectin expression or splicing is associated with cancer progression and fibrotic diseases, highlighting the importance of FibronectinTyp in cell–matrix biology.