title: Biosynthesis and intracellular transport of a membrane glycoprotein (plgp57) of the prelysosome compartment.
abstract: We have characterized the biosynthesis and intracellular transport of a membrane glycoprotein, designated plgp57, which is found predominantly in the prelysosome compartment (PLC) of Madin-Darby bovine kidney cells. In pulse-chase experiments, plgp57 was found to be initially synthesized as a 35 kDa precursor which was modified to yield a diffuse approximately 57 kDa mature form. Digestion with endoglycosidase H (endo H) demonstrated that the 35 kDa precursor contained three endo H-sensitive, high mannose-type oligosaccharides which became modified to endo H-resistant, complex-type sugars on the approximately 57 kDa mature form. Labelling cells in the presence of tunicamycin and treatment of the 35 kDa precursor with endo H revealed that plgp57 has a core protein of 24 kDa to which three N-asparagine-liked oligosaccharides are attached. Other experiments indicated that plgp57 could be differentially glycosylated on a common 24 kDa core protein in different cell types. The half-lives of the glycosylated and non-glycosylated forms of plgp57 were approximately 18 and approximately 13 h, respectively. Glycosylated and non-glycosylated plgp57 exhibited similar steady-state intracellular distributions, indicating that targeting of plgp57 to the PLC does not require carbohydrate address markers. Pulse-labeling of cells followed by organelle fractionation at various chase times revealed a t1/2 = approximately 1 h for the transit of newly synthesized plgp57 to the PLC. Finally, amino terminal sequencing of plgp57 revealed the similarity of this protein to the CD63/ME491 family of membrane glycoproteins.
authors.affiliation: Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, NY 14853.
authors.forename: L
authors.initials: L
authors.lastname: Heller
authors.forename: J E
authors.initials: JE
authors.lastname: Park
authors.forename: W J
authors.initials: WJ
authors.lastname: Brown
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002451:Cell Compartmentation; D002460:Cell Line; D004285:Dogs; D006031:Glycosylation; D007424:Intracellular Fluid / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011499:Protein Processing, Post-Translational
chemical_list: D008562:Membrane Glycoproteins