Friend of Echinoid (Fred) and Echinoid (Ed) regulate EGFR trafficking. Qian Nie, Susan Spencer. Department of Biology, Saint Louis, MO.

   The Epidermal Growth Factor Receptor (EGFR) is a receptor tyrosine kinase that regulates signaling pathways critical for cell proliferation and differentiation in epithelial tissues. The amount of EGFR available for signaling is regulated by a balance of receptor recycling to the plasma membrane and degradation in the lysosome. We have found that the immunoglobulin cell adhesion molecules Echinoid (Ed) and Friend of Echinoid (Fred) can regulate the level of EGFR on the plasma membrane. Ed and Fred amino acid sequences are closely related, but Fred lacks the PDZ binding domain found at Eds C-terminus. Here, using truncated and chimaeric forms of Ed and Fred, we examine the importance of Eds PDZ-binding domain in regulating internalization from the plasma membrane. We also examine whether Freds effects on EGFR internalization require Ed. A possible model of how Fred and Ed regulate EGFR internalization will be discussed.