Cycling of an 85-kDa lysosomal membrane glycoprotein between the cell surface and lysosomes in cultured XXXX hepatocytes.

@entity1880 @entity535 @entity55983 @entity50461 @entity35 @entity20350
We studied the endocytic transport of an 85-kDa lysosomal membrane glycoprotein ( @entity55983 ) from the cell surface to lysosomes in cultured @entity35 hepatocytes. Fab' fragments of a monoclonal antibody against @entity55983 (YA30 mAb) were conjugated with horseradish peroxidase (HRP) and then used as probes to monitor the endocytic transport of @entity55983 from the plasma membrane to lysosomes. Continuous internalization and lysosomal transport of HRP-YA30 mAb Fab' occurred in the hepatic cells, resulting in its accumulation in the dense lysosomal fraction obtained from the cells on Percoll density centrifugation. The endocytic transport of HRP-YA30 mAb continued in the presence of the protein synthesis inhibitor, @entity1880 , indicating that @entity55983 is cycled between the cell surface and lysosomes or endosomes, like other lysosomal membrane glycoproteins, @entity20350 and @entity50461 , as reported previously [Akasaki et al. (1993) J. Biochem. 114, 598-604]. The half times (t1/2) of internalization and lysosomal transport of @entity55983 were 32 min and 2.0 h, respectively. The kinetics of endocytic transport for @entity55983 are very similar to those of @entity20350 and @entity50461 . @entity55983 possesses a short cytoplasmic tail whose @entity535 sequence is quite different from those of @entity20350 and @entity50461 . Therefore, these results suggested that continuous internalization from the cell surface and lysosomal transport of of endogenous @entity55983 occur through a mechanism that can recognize this novel @entity535 sequence, probably a Leu-Ile-containing motif, in normal hepatic cells of @entity35 .
