RECEPTOR EXTRACELLULAR DOMAINS MAY CONTAIN TRAFFICKING INFORMATION - STUDIES OF THE 300-KDA MANNOSE 6-PHOSPHATE RECEPTOR

The 300-kDa mannose 6-phosphate receptor cycles between the trans Golg i network and late endosomes, and between the plasma membrane and earl y endosomes, to deliver lysosomal enzymes to prelysosomes. Mannose 6-p hosphate receptor trafficking requires structural determinants present in the cytoplasmic domain. However, when this domain was joined with the extracellular and transmembrane domains of the epidermal growth fa ctor receptor, it was not sufficient to direct this chimera to late en dosomes and the trans Golgi network (Dintzis, S. M., and Pfeffer, S. R . (1990) EMBO J. 9, 77-84). These findings suggested a role for extrac ellular and/or transmembrane domains in mannose 6-phosphate receptor t rafficking. We describe here the construction and expression of chimer ic receptors comprised of mannose 6-phosphate receptor extracellular a nd transmembrane sequences joined with cytoplasmic domain sequences de rived from the human epidermal growth factor receptor or the human low density lipoprotein receptor. The chimeras were stable proteins which were efficiently endocytosed and competent to bind a mannose 6-phosph ate-containing ligand. Antibody binding assays and indirect immunofluo rescence showed that the chimeras containing the mannose 6-phosphate r eceptor extracellular domain colocalized with mannose 6-phosphate rece ptors in intracellular compartments, These experiments suggest that th e presence of the mannose 6-phosphate receptor extracellular domain ma y interfere with the rapid recycling of receptors from early endosomes to the cell surface and detain receptors within endosomes.