Two lysosomal membrane proteins, LGP85 and LGP107, are delivered to late endosomes/lysosomes through different intracellular routes after exiting from the trans-Golgi network.
Lysosomal membrane proteins are delivered from their synthesis site, the endoplasmic reticulum (ER) to late endosomes/lysosomes through the Golgi complex. It has been proposed that after leaving the Golgi they are transported either directly or indirectly (via the cell surface) to late endosomes/lysosomes. In the present study, we examined the transport routes taken by two structurally different lysosomal membrane proteins, LGP85 and LGP107, in rat 3Y1-B cells. Here we show that newly synthesized LGP85 and LGP107 are delivered to late endosomes/lysosomes via a direct route without passing through the cell surface. Interestingly, although LGP107 is delivered from the Golgi to early endosomes containing internalized horseradish peroxidase-conjugated transferrin (HRP-Tfn) en route to lysosomes, LGP85 does not pass through the HRP-Tfn-positive early endosomes. These results suggest, therefore, that LGP85 and LGP107 are sorted into distinct transport vesicles at the post-Golgi, presumably the trans-Golgi network (TGN), after which LGP85 is delivered directly to late endosomes/lysosomes, but significant fractions of LGP107 are targeted to early endosomes before transport to late endosomes/lysosomes. This study provides the first evidence that after exiting from the Golgi, LGP85 and LGP107 are targeted to late endosomes/lysosomes via a different pathway.
Niwa
Kazuo
K
Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, 812-8582, Fukuoka, Japan.
Tanaka
Rie
R
Murase
Hiroshi
H
Ishikawa
Toyoko
T
Fujita
Hideaki
H
Himeno
Masaru
M
Tanaka
Yoshitaka
Y
D000818:Animals; D001693:Biological Transport, Active; D018955:CD36 Antigens / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D007700:Kinetics; D051907:Lysosomal Membrane Proteins; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism; D051381:Rats; D012795:Sialoglycoproteins / Q000378:metabolism*
D018955:CD36 Antigens; C084447:Lgp107 protein, rat; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D012795:Sialoglycoproteins; C070693:Scarb2 protein, rat