Palmitoylation of ERBIN is required for its plasma membrane localization

LAP (leucine-rich repeats (LRR) and PSD-95/Dlg/ZO-1 (PDZ)) family proteins, including Scribble, LET-413, ERBIN, Densin-180 and Lano, are involved in the regulation of cell polarity. The LRR domains of LAP proteins were reported to mediate their basolateral membrane localization and to be essential for their function. To further dissect the mechanism of the plasma membrane localization of ERBIN, we introduced various mutants of ERBIN into cultured cells and observed the intracellular localization. When an LRR domain mutant lacking amino acid residues 1-32 at the amino (N) terminal region was over-expressed in cells, the mutant did not localize at the plasma membrane, but localized in the cytoplasm. We found that cysteines 14 and 16 at the N-terminal region of ERBIN are in vivo palmitoylated. Over-expressed mutants in which cysteine 14 and/or cysteine 16 were changed to serines did not localize at the plasma membrane, indicating that the palmitoylation of ERBIN is necessary for its plasma membrane localization. The over-expressed 1-196 amino acids fragment of ERBIN, which lacked the latter half of LRR, was palmitoylated but did not localize at the plasma membrane. These results suggest that both palmitoylation and LRR are required for the plasma membrane localization of ERBIN.