The cell adhesion receptor carcinoembryonic antigen-related cell adhesion molecule 1 regulates nucleocytoplasmic trafficking of DNA polymerase delta-interacting protein 38.

The homophilic cell-cell adhesion receptor CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1, CD66a) acts as a regulator of contact-dependent cell survival, differentiation, and growth. It is involved in the control of proliferation in hematopoietic and epithelial cells and can act as a tumor suppressor. In this study, we identify DNA polymerase delta-interacting protein 38 (PDIP38) as a novel binding partner for CEACAM1-L and CEACAM1-S. We show that PDIP38 can occur in the nucleus, in the cytoplasm and at the plasma membrane in NBT-II, IEC18, RBE, and HeLa cells and that the distribution in NBT-II cells is influenced by the confluency of the cells. We also demonstrate that the interaction of CEACAM1 and PDIP38 is of functional importance in NBT-II cells, which co-express the long and the short CEACAM1 isoform. In subconfluent, proliferating NBT-II cells, perturbation of CEACAM1 by antibody clustering induces increased binding to PDIP38 and results in rapid recruitment of PDIP38 to the plasma membrane. The same treatment of confluent, quiescent NBT-II cells leads to a different response, i.e. translocation of PDIP38 to the nucleus. Together, our data show that PDIP38 can shuttle between the cytoplasmic and the nuclear compartments and that its subcellular localization is regulated by CEACAM1, implicating that PDIP38 may constitute a novel downstream target of CEACAM1 signaling.