CEACAM2-L on Spermatids Interacts with Poliovirus Receptor on Sertoli Cells in Mouse Seminiferous Epithelium

The removal of excess cytoplasm from elongated spermatids by Sertoli cells is the last essential step in spermatogenesis. It requires cell-to-cell recognition between a Sertoli cell and an elongating spermatid through protein-protein interactions. CEACAM2-L, an adhesion molecule of the immunoglobulin superfamily (IgSF), is present at the plasma membrane covering the excess cytoplasm of elongated spermatids, and is possibly involved in the cell-to-cell recognition. In this study, we investigated the interaction between CEACAM2-L and Poliovirus receptor (PVR), which is also from the IgSF and is expressed by Sertoli cells. Immunohistochemical analysis showed that CEACAM2-L expressed on elongated spermatids was in close contact with PVR-positive cell processes of Sertoli cells. Immunoprecipitation experiments both in vivo and in vitro demonstrated a direct heterophilic interaction between CEACAM2-L and PVR. We show that the N-terminal Ig domain of CEACAM2-L was critical for its interaction with PVR. In addition, we found that CEACAM2-L formed heterophilic trans-tetramers with PVR in transfected COS-7 cells. From these data, we propose that Sertoli cells recognize the excess cytoplasm of elongated spermatids through the PVR-CEACAM2-L interaction in mouse testis.