Interactions between the juxtamembrane domain of the EGFR and calmodulin measured by surface plasmon resonance

Abstract

One early response to epidermal growth factor receptor (EGFR) activation is an increase in intracellular calcium. We have used surface plasmon resonance (SPR) to study real-time interactions between the intracellular juxtamembrane (JM) region of EGFR and calmodulin. The EGFR-JM (Met 644–Phe 688) was expressed as a GST fusion protein and immobilised on a sensor chip surface. Calmodulin specifically interacts with EGFR-JM in a calcium-dependent manner with a high on and high off rate. Chemical modification of EGFR-JM by using arginine-selective phenylglyoxal or deletion of the basic segment Arg 645–Arg 657 inhibits the interaction. Phosphorylation of EGFR-JM by protein kinase C (PKC) or glutamate substitution of Thr 654 inhibits the interaction, suggesting that PKC phosphorylation electrostatically interferes with calmodulin binding to basic arginine residues. Calmodulin binding was also inhibited by suramin. Our results suggest that EGFR-JM is essential for epidermal growth factor (EGF)-mediated calcium–calmodulin signalling and for signal integration between other signalling pathways.