The recycling itinerary of the 46 kDa mannose 6-phosphate receptor--Golgi to late endosomes--coincides with that of the 215 kDa M6PR.

The intracellular distribution and trafficking of the 46 kDa mannose 6-phosphate (M6PR) receptor has been investigated in rat Clone 9 hepatocytes and NRK cells and compared to that of the 215 kDa M6PR. Antibodies were generated to a synthetic peptide corresponding to the last 15 amino acids of the C-terminal cytoplasmic domain of the 46 kDa M6PR and used to localize it by immunofluorescence and immunoperoxidase labeling. At steady state the 46 kDa M6PR was concentrated at its presumptive sorting site in the Golgi complex, mainly in middle and trans cisternae. In cells treated with chloroquine or NH4Cl, the receptor was found in swollen multivesicular endosomes as well as in Golgi cisternae. When chloroquine-treated cells were double labeled with antibodies to both the 215 and 46 kDa M6PR, all of the endosomes which contained detectable 46 kDa also contained 215 kDa receptor. Thus, after weak base treatment, the 46 kDa receptor is located in a compartment which corresponds to the delivery site of the 215 kDa receptor, previously identified as a late endosome (Woods, J. W., J. Goodhouse, M. G. Farquhar, Eur. J. Cell Biol. 50, 132-143 (1989]. We conclude that the intracellular itinerary of the 46 kDa M6PR is similar to that of the 215 kDa M6PR in that both receptors cycle between the Golgi complex and the same population of late endosomes (prelysosomes). However, the distribution of the two receptors along the recycling route varies under identical conditions in these two cell types.(ABSTRACT TRUNCATED AT 250 WORDS)