Phorbol ester modulation of integrin-mediated cell adhesion: a postreceptor event

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Chinese hamster ovary (CHO) cells in suspension culture adhere to extracellular matrix proteins like fibronectin.
• This adhesion is mediated by cell surface fibronectin receptors (FnR), a type of integrin.

Purpose of the Study:

• To investigate the effect of phorbol ester on CHO cell adhesion to fibronectin.
• To determine the mechanism by which phorbol ester modulates integrin-mediated adhesion.

Main Methods:

• Treatment of CHO cells with phorbol ester.
• Assessing cell adhesion rates and efficiency to fibronectin-coated substrata.
• Measuring cell binding to polylysine and concanavalin A to assess nonspecific adhesion.
• Quantifying cell surface fibronectin receptor number and affinity.
• Analyzing protein phosphorylation patterns in control and treated cells.

Main Results:

• Phorbol ester treatment increased fibronectin-mediated cell adhesion rate and efficiency by four- to fivefold.
• Phorbol ester treatment reduced sensitivity to adhesion inhibitors but did not affect nonspecific adhesion.
• No changes were observed in fibronectin receptor number or affinity.
• Phorbol ester did not stimulate phosphorylation of FnR or talin.

Conclusions:

• Phorbol esters modulate integrin-mediated adhesion in CHO cells.
• The effect is downstream of ligand-receptor binding and not due to direct FnR phosphorylation.
• Post-receptor events, potentially involving cytoskeletal protein phosphorylation, are implicated in phorbol ester's action.