p23, a major COPI-vesicle membrane protein, constitutively cycles through the early secretory pathway

摘要

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 demon- strate 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 local- ization is, at least in part, a result of retrieval from post-ER compartments because CD8-p23 fusion proteins receive post-ER modifications.