p23, a major COPI-vesicle membrane protein, constitutively cycles through the early secretory pathway.
A novel type I transmembrane protein of COPI-coated vesicles, p23, has been demonstrated to be localized mainly to the Golgi complex. This protein and p24, another member of the p24 family, have been shown to bind coatomer via their short cytoplasmic tails. Here we demonstrate that p23 continuously cycles through the early secretory pathway. The cytoplasmic tail of p23 is shown to act as a functional retrieval signal as it confers endoplasmic reticulum (ER) residence to a CD8-p23 fusion protein. This ER localization is, at least in part, a result of retrieval from post-ER compartments because CD8-p23 fusion proteins receive post-ER modifications. In contrast, the cytoplasmic tail of p24 has been shown not to retrieve a CD8-p24 fusion protein. The coatomer binding motifs FF and KK in the cytoplasmic tail of p23 are reported to influence the steady-state localization of the CD8-p23 fusion protein within the ER-Golgi recycling pathway. It appears that the steady-state Golgi localization of endogenous p23 is maintained by its lumenal domain, as a fusion protein with the lumenal domain of CD8, and the membrane span as well as the cytoplasmic tail of p23 is no longer detected in the Golgi.
Nickel
W
W
Biochemie-Zentrum Heidelberg, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany. walter.nickel@urz.uni-heidelberg.de
Sohn
K
K
Bünning
C
C
Wieland
F T
FT
D000818:Animals; D000906:Antibodies; D001665:Binding Sites; D016827:CD8 Antigens / Q000096:biosynthesis; D019556:COS Cells; D002460:Cell Line; D020756:Coatomer Protein; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis / Q000096:biosynthesis*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000096:biosynthesis; D014162:Transfection
D000906:Antibodies; D016827:CD8 Antigens; D020756:Coatomer Protein; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins