Ubiquitination within the membrane-proximal ezrin-radixin-moesin (ERM)-binding region of the L1 cell adhesion molecule

Abstract

The dynamic turnover of the L1 cell adhesion molecule to and from the plasma membrane that is mediated through exoand endocytic trafficking is central to axon outgrowth. Although the ubiquitination of L1 in response to incubation with an L1 antibody that mimics L1-L1 homophilic binding has been previously shown, the endocytic trafficking pathway of the ubiquitinated L1 destined for degradation is yet unclear. I have recently shown that the ubiquitinated L1 is endocytosed by Rabex-5, which is an ubiquitin-binding protein and guanine nucleotide exchange factor for Rab5, into early endosomes from the plasma membrane. Here, I speculate on the putative ubiquitination site within the membrane-proximal ezrinbinding motif in the cytoplasmic domain of L1 and discuss the regulatory role of this motif in the competition between ubiquitination and the binding of ezrin prior to L1 internalization. © 2013 Landes Bioscience.