The assembly of CD1e is controlled by an N-terminal propeptide which is processed in endosomal compartments: Double endosomal processing of CD1e

International audienceCD1e displays unique features in comparison to other CD1 proteins. CD1e accumulates in Golgi compartments of immature dendritic cells and is directly transported to lysosomes, where it is cleaved in a soluble form. In these latter compartments, CD1e participates in the processing of glycolipid antigens. Here we show that the N-terminal end of the membrane-associated molecule begins at aminoacid 20, while the soluble molecule consists of aminoacids 32 to 333. Thus, immature CD1e includes an N-terminal propeptide which is cleaved in acidic compartment and so, absent on the mature endosomal form. Mutagenesis experiments demonstrated that the propeptide controls the assembly of the CD1e α chain with β2-microglobulin while propeptide-deleted CD1e molecules are immunologically active. Comparison of CD1e cDNAs from different mammalian species indicates that the CD1e propeptide is conserved during evolution, suggesting that it may also optimize the generation of CD1e molecules in other species