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Reconstitution of sterol-regulated endoplasmic reticulum-to-Golgi transport of SREBP-2 in insect cells by co-expression of mammalian SCAP and Insigs



Reconstitution of sterol-regulated endoplasmic reticulum-to-Golgi transport of SREBP-2 in insect cells by co-expression of mammalian SCAP and Insigs



Journal of Biological Chemistry 278(37): 35837-35843



In mammalian cells, membrane-bound sterol regulatory element-binding proteins (SREBPs) are transported from ER to Golgi where they are processed proteolytically to generate soluble transcription factors that activate lipid synthesis. ER-to-Golgi transport requires SCAP, a sterol-regulated escort protein. In sterol-treated cells, the SCAP/SREBP complex binds to Insig-1 or Insig-2, which retains the complex in the ER, blocking SREBP processing and decreasing lipid synthesis. In Drosophila cells, the endogenous SCAP/SREBP complex is transported to Golgi, but transport is blocked by phosphatidylethanolamine instead of sterols. Here, we show that mammalian SREBP-2 is not transported to Golgi when expressed in Drosophila cells. Transport requires co-expression of mammalian SCAP. Sterols block transport of the mammalian SCAP/SREBP-2 complex, but only when mammalian Insig-1 or -2 is co-expressed. These reconstitution studies define SCAP and Insig as the minimal requirements for sterol-regulated transport of SREBPs from ER to Golgi. They indicate that insect cells can respond to sterols when proper regulatory proteins are expressed.

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Accession: 011255664

Download citation: RISBibTeXText

PMID: 12842885

DOI: 10.1074/jbc.M306476200


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