Multiple Cryptic Binding Sites are Necessary for Robust Fibronectin Assembly: An In Silico Study.

Area of Science:

• Biophysics
• Extracellular Matrix Biology
• Computational Biology

Background:

• Fibronectin (FN) assembly into insoluble fibrils is essential for tissue structure and mechanics.
• Cell-generated forces expose cryptic binding sites within FN domains, driving fibril formation.
• The precise number and location of these FN-FN binding sites remain debated.

Purpose of the Study:

• To investigate the role of cryptic binding site number and location in fibronectin fibrillogenesis.
• To test competing hypotheses regarding FN-FN interactions using a biophysical model.
• To quantify the impact of molecular alterations on assembled FN fibril properties.

Main Methods:

• Development and application of a novel biophysical model for fibronectin fibrillogenesis.
• Simulation of FN assembly under varying numbers and locations of FN-FN binding sites.
• Analysis of predicted FN fibril properties, including robustness and viscoelasticity.

Main Results:

• Models with a single FN-FN binding site predicted negligible or non-physiological fibrillogenesis.
• Inclusion of multiple FN-FN binding sites robustly predicted fibrillogenesis, with minimal dependence on individual domain properties.
• Multiple binding site models generated heterogeneous fibril populations with two distinct viscoelastic phenotypes.

Conclusions:

• Multiple cryptic FN-FN binding sites are essential for robust fibronectin fibril formation.
• The heterogeneity in predicted fibril phenotypes suggests a mechanism for generating diverse mechanical signals in the extracellular matrix.
• These findings have implications for understanding tissue development and regeneration.