Dendritic cells express possible ligand(s) for CD38 (45.13)

Abstract

CD38 is expressed in cells of the immune system, it has been implicated in several biological functions such as; chemotaxis, cell activation, cell proliferation, rescue or induction of apoptosis. It also has enzymatic activity converting NAD to ADPR and cADPR. It is not known how this molecule can perform different functions in different cells. It has been suggested that such biological functions could be mediated by different ligands, which would explain the pleiotropy attributed to CD38. CD31, present on endothelial cells, has been identified as a possible ligand for CD38; however, these results have not been confirmed in mouse. On the other hand, two molecules were identified in mouse dendritic cells as potential ligands but without further characterization. The aim of this work was to identify new possible ligands in a murine model using chimeric proteins of CD38. We designed three soluble chimeric proteins of the extracellular domain of CD38. One fused with CD8α, a second one fused with the Fc from the IgG1 immunoglobulin, both from human, and a third one containing only a V5 epitope and a histidine tag. The proteins were characterized by WB and enzymatic activity assays. All proteins formed soluble dimers and exhibited enzymatic activity. Using these proteins we were able to identify potential ligand(s) present on DCs but not on T and B lymphocytes from WT or CD38 KO immunized mice. This data suggest that DCs may play a role in CD38 function on B and T cells.