| Research Abstract |
Langerin is a C-type lectin that expresses in epidermal dendritic cells, called Langerhans cells. In this study, we cloned mouse Langerin (mLangerin) to investigate its expression pattern and function precisely using mouse system.
Based on human Langerin (hLangerin) sequence, cDNA clone that encoded a polypeptid with 65% similarity with hLangerin was cloned. In the result of FISH analysis, the gene was mapped on a syntenic region with that of hLangerin. Additionally, exon-intron structures of h- and mLangerin were conserved well.
In skin, expression of mLangerin mRNA was not restricted in epidermis unexpectedly, although protein expression of mLangerin was only observed in epidermal MHC class II^+ cells. mLangerin mRNA as well as protein was also detected in various organs including subcutaneous lymph nodes, spleen, thymus and liver. In suspension cells of spleen, CD11c^+ cells exclusively expressed mLangerin mRNA. Furthermore, CD8α^<high>CD11b^<low> fractions in liver, spleen and subcutaneous lymph nodes expressed predominantly.
On the other hand, we found heptad repeats of hydrophobic amino acids in mLangerin neck domain. So intermolecular multimer formation was checked using protein cross-linker. In the result, dimmer and tetramer formation of mLangerin protein was observed and this multimer formation possibly increases avidity of mLangerin for its ligand(s). We next checked binding activity of mLangerin with several sugars. In the result, mLangerin could bind mannan that often exists in microbe cell wall. Using mLangerin transfectant, it was confirmed that mLangerin was involved in capturing of dextran, ovalbumin and zymosan.
These results suggest that mLangerin might work as microbe and antigen receptors of CD8α^<high>CD11b^<low> subset of mouse dendritic cells.
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