Membrane palmitoylated proteins regulate trafficking and processing of nectins.

Nectins are cell-cell adhesion molecules involved in the formation of various intercellular junctions and the establishment of apical-basal polarity at cell-cell adhesion sites. To have a better understanding of the roles of nectins in the formation of cell-cell junctions, we searched for new cytoplasmic binding partners for nectin. We report that nectin-1α associates with membrane palmitoylated protein 3 (MPP3), one of the human homologues of a Drosophila tumor suppressor gene, Disc large. Two major forms of MPP3 at 66 and 98 kDa were detected, in conjunction with nectin-1α, suggesting that an association between the two may occur in various cell types. Nectin-1α recruits MPP3 to cell-cell contact sites, mediated by a PDZ-binding motif at the carboxyl terminus of nectin-1α. Association with MPP3 increases cell surface expression of nectin-1α and enhances nectin-1α ectodomain shedding, indicating that MPP3 regulates trafficking and processing of nectin-1α. Further study showed that MPP3 interacts with nectin-3α, but not with nectin-2α, showing that the association of nectins with MPP3 is isoform-specific. MPP5, another MPP family member, interacts with nectins with varying affinity and facilitates surface expression of nectin-1α, nectin-2α, and nectin-3α. These data suggest that wide interactions between nectins and MPP family members may occur in various cell-cell junctions and that these associations may regulate trafficking and processing of nectins.