Historically, an important strategy for disrupting the adhesion of integrins to their ligands is by using a synthetic peptide that mimics the binding site on the ECM molecule to which the integrin attaches. In the case of fibronectin, the amino acid sequence is arginine-glycine-aspartate (when written using the single letter designation for each amino acid, this sequence becomes RGD). Explain why addition of such synthetic peptides would disrupt binding of cells to their normal substratum?

a. When the integrins are bound to RGD peptides, their receptors will be unavailable for binding to FN (or LN), and thus cells will be inhibited from binding to the ECM.
b. When the ECM molecules are bound to RGD peptides, their receptors will be unavailable for binding to FN (or LN), and thus cells will be inhibited from binding to the integrin.
c. When the integrins are bound to RGD peptides, their receptors will be available for binding to FN (or LN), and thus cells will be inhibited from binding to the ECM.
d. When the ECM molecules are bound to RGD peptides, their receptors will be available for binding to FN (or LN), and thus cells will be inhibited from binding to the integrin.

An array of transmembrane receptors that are big and play an essential role in combining cell with its adjacent cells or with its surrounding extracellular matrix are termed as integrins. They perform an essential function of transmitting the signal from the extracellular matrix to the cell, that is, they help in the process of signal transduction.

In the phenomenon of signal transduction, the integrins in the company of the receptor tyrosine kinases or RTKs help in monitoring the cell signaling pathways. This association between the integrins and RTKs are supportive and takes place in one direction only, that is, it is unidirectional. In case, when the combination between RGD peptides and integrins takes place, the receptors of integrins lose the tendency to combine with LN or FN, which eventually prevents the cells from binding with the extracellular matrix.