期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：49
页码：E6752-E6761
DOI：10.1073/pnas.1520957112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceUsing a rapamycin-based, endoplasmic reticulum (ER) trapping scheme, modified to avoid the problem of an endogenous ER-localized FKBP-binding protein, we demonstrate that Golgi enzymes constitutively recycle back to the ER and that such recycling plays a central role in the maintenance, biogenesis, and inheritance of the Golgi apparatus in mammalian cells. We describe morphological characteristics of the retrograde carriers that ferry Golgi enzymes back to the ER and identify key molecular machinery regulating carrier formation. The study helps resolve the long-standing debate regarding the extent of Golgi enzyme trafficking back to the ER, paving the way for further investigations into the mechanistic details and functional implications of the Golgi's steady-state existence and relationship to the ER. Whether Golgi enzymes remain localized within the Golgi or constitutively cycle through the endoplasmic reticulum (ER) is unclear, yet is important for understanding Golgi dependence on the ER. Here, we demonstrate that the previously reported inefficient ER trapping of Golgi enzymes in a rapamycin-based assay results from an artifact involving an endogenous ER-localized 13-kD FK506 binding protein (FKBP13) competing with the FKBP12-tagged Golgi enzyme for binding to an FKBP-rapamycin binding domain (FRB)-tagged ER trap. When we express an FKBP12-tagged ER trap and FRB-tagged Golgi enzymes, conditions precluding such competition, the Golgi enzymes completely redistribute to the ER upon rapamycin treatment. A photoactivatable FRB-Golgi enzyme, highlighted only in the Golgi, likewise redistributes to the ER. These data establish Golgi enzymes constitutively cycle through the ER. Using our trapping scheme, we identify roles of rab6a and calcium-independent phospholipase A2 (iPLA2) in Golgi enzyme recycling, and show that retrograde transport of Golgi membrane underlies Golgi dispersal during microtubule depolymerization and mitosis.
