The MRH protein Erlectin is member of the endoplasmic reticulum synexpression group and functions in N-glycan recognition

Kremen1 and 2 (Krm1/2) are coreceptors for Dickkopf1 (Dkk1), an antagonist of Wnt/beta-catenin signaling and play a role in head induction during early Xenopus development. In a proteomic approach we identified Erlectin, a novel protein that interacts with Krm2. Erlectin (XTP3-B) is member of a protein family containing mannose-6-phosphate receptor homology (MRH-, or PRKCSH-) domains implicated in N-glycan binding. Like other members of the MRH family, Erlectin is a luminal resident protein of the endoplasmic reticulum (ER). It contains two MRH domains, of which one is essential for Krm2 binding, and this interaction is abolished by Krm2 deglycosylation. Overexpression of Erlectin inhibits transport of Krm2 to the cell surface. Analysis of its embryonic expression pattern in Xenopus reveals that Erlectin is member of the ER synexpression group. Erlectin Morpholino antisense injection leads to head and axial defects during organogenesis stages in Xenopus embryos. The results indicate that Erlectin functions in N-glycan recognition in the ER, suggesting that it may regulate glycoprotein traffic.