Expression and localization of CHODLDeltaE/CHODLfDeltaE, the soluble isoform of chondrolectin.

The C-type lectin family is a group of animal proteins which can be distinguished from other lectins by the presence of a Ca2+-dependent carbohydrate recognition domain (CRD) in their protein sequence. They are classified into 17 groups according to their domain architecture and have a wide variety of functions. The human chondrolectin gene encodes transmembrane (CHODL, CHODLf) and soluble proteins (CHODLDeltaE, CHODLfDeltaE) belonging to the family of C-type lectins because of the presence of one CRD domain in their N-terminal region. The CHODL splice variants (CHODLf, CHODLDeltaE and CHODLfDeltaE) are differentially expressed in T lymphocytes. The transmembrane-containing isoform CHODLf is localized in the ER-Golgi apparatus. CHODLDeltaE and CHODLfDeltaE are devoid of the transmembrane domain and terminate in QDEL, an ER retention signal. In this paper we have investigated the expression of the CHODLDeltaE/CHODLfDeltaE protein. This variant localizes in the late endoplasmic reticulum. We detected the protein in spleen and tonsils in a small population of lymphocytes. Moreover, the isoform seems to be differentially expressed in thymocytes and lymphocytes suggesting an important biological function during T cell development.