Erbin: sorting out ErbB2 receptors or giving Ras a break?

Erbin is a member of the leucine-rich repeat and PDZ domain (LAP) family. Originally cloned as an epidermal growth factor receptor (EGFR)-associated protein involved in receptor sorting and cell polarization, erbin has now been shown to inhibit EGF signaling by preventing the activation of the Raf-1 kinase by Ras. This discovery provides new insights into the rapidly expanding roles of adaptor and scaffolding proteins in the regulation of receptor signaling. It also highlights the complexity of cellular signaling networks in which the tasks of individual components are determined by the specific functional context.