FN1

FN1 Full Name

fibronectin 1

FN1 Introduction

FN1 (Fibronectin 1) encodes a high-molecular weight glycoprotein that exists in multiple forms, including a soluble dimeric form in plasma and dimeric or multimeric forms deposited in the extracellular matrix. The FN1 monomer is composed of three types of repeating modules: type I, type II, and type III fibronectin domains, which are organized into functional regions including an N-terminal 70-kDa domain, a central 120-kDa binding domain, and a C-terminal heparin-binding domain. Two cysteine residues at the C-terminus form disulfide bonds with another monomer to create the functional dimeric protein. The protein contains multiple functional domains that mediate interactions with diverse binding partners including collagen, fibrin, heparin, integrins, and cell surface receptors.

Figure 1. Strcuture of FN1.

Tissue Distribution and Physiological Functions
FN1 is widely expressed across multiple tissues, with highest levels detected in liver, lung, placenta, and kidney. Plasma fibronectin, the soluble dimeric form, is primarily secreted by hepatocytes, while cellular fibronectin is produced by fibroblasts, epithelial cells, and other cell types for deposition as fibrils in the extracellular matrix. The protein plays essential roles in numerous physiological processes including cell adhesion and migration, embryogenesis, wound healing, blood coagulation, host defense, and maintenance of cell shape. In bone development, FN1 expression is enhanced via Wnt-dependent signaling and directly regulated by RUNX2, contributing to osteoblast differentiation and proper bone formation. FN1 also participates in osteoblast compaction through cell-mediated matrix assembly, essential for mineralization.

Oncogenic Mechanisms and Metastasis Regulation
FN1 plays complex and context-dependent roles in cancer biology, functioning as both tumor suppressor and oncogene depending on cellular context and isoform expression. In papillary thyroid carcinoma, FN1 is the most highly enriched gene and shows distinctive intracellular and extracellular expression patterns, with strong correlation to p53 signaling pathway activation. Knockdown of FN1 severely compromises p53 signaling and cyclin protein expression, increasing cell growth while inhibiting invasion. In HPV-negative head and neck squamous cell carcinoma, FN1 is overexpressed in malignant cells of metastatic patients and serves as a direct target of miR-27b, which reduces metastatic potential by negatively regulating FN1 at the translational level. FN1 contributes to pre-metastatic niche formation by serving as a key ligand for integrins such as VLA-4, creating an extracellular matrix architecture that facilitates tumor cell invasion and organ-specific metastasis. The protein is also involved in angiogenesis, platelet degranulation, and leukocyte migration, processes frequently hijacked during cancer progression.

Alternate Names for FN1

FN1; fibronectin 1; Fn; Fn-1; E330027I09; fibronectin;

• Immunohistochemistry Antibodies for Pathology