Fig. 8. Model of Echinoid-Neuroglian homophilic and heterophilic interactions. Echinoid and Neuroglian are both homophilic CAMs. They also trans-interact with each other via a heterophilic mechanism. Whether they are also able to cis-interact in the same plasma membrane is currently unknown. Most significantly, L1-type proteins are cell-autonomous, positive regulators of EGFR signaling, whereas Ed negatively influences EGFR function via its cytoplasmic domain. By interacting with Ed that is expressed on neighboring cells Neuroglian can act as an autonomous activator and as a non-autonomous inhibitor of EGFR signaling.