TY - JOUR
T1 - Sterols regulate processing of carbohydrate chains of wild-type SREBP cleavage-activating protein (SCAP), but not sterol-resistant mutants Y298C or D443N
AU - Nohturfft, Axel
AU - Brown, Michael S.
AU - Goldstein, Joseph L.
PY - 1998/10/27
Y1 - 1998/10/27
N2 - SREBP cleavage activating protein (SCAP), a membrane-bound glycoprotein, regulates the proteolytic activation of sterol regulatory element binding proteins (SREBPs), which are membrane-bound transcription factors that control lipid synthesis in animal cells. SCAP-stimulated proteolysis releases active fragments of SREBPs from membranes of the endoplasmic reticulum and allows them to enter the nucleus where they activate transcription. SteroIs such as 25-hydroxycholesterol inactivate SCAP, suppressing SREBP proteolysis and turning off cholesterol synthesis. We here report the isolation of Chinese hamster ovary cells with a point mutation in SCAP (Y298c) that renders the protein resistant to inhibition by 25-hydroxycholesterol. Like the previously described D443N mutation, the Y298C mutation occurs within the putative sterol-sensing domain, which is part of the polytopic membrane attachment region of SCAP. Cells that express SCAP(Y298C) continued to process SREBPs in the presence of 25-hydroxycholesterol and hence they resisted killing by this sterol. In wild-type Chinese hamster ovary cells the N-linked carbohydrate chains of SCAP were mostly in the endoglycosidase H- sensitive form when cells were grown in medium containing 25- hydroxycholesterol. In contrast, when cells were grown in sterol-depleted medium, these chains were converted to an endoglycosidase H-resistant form. 25-Hydroxycholesterol had virtually no effect in cells expressing SCAP(D443N) or SCAP(Y298C). The relation between this regulated carbohydrate processing to the SCAP-regulated proteolysis of SREBP remains to be explored.
AB - SREBP cleavage activating protein (SCAP), a membrane-bound glycoprotein, regulates the proteolytic activation of sterol regulatory element binding proteins (SREBPs), which are membrane-bound transcription factors that control lipid synthesis in animal cells. SCAP-stimulated proteolysis releases active fragments of SREBPs from membranes of the endoplasmic reticulum and allows them to enter the nucleus where they activate transcription. SteroIs such as 25-hydroxycholesterol inactivate SCAP, suppressing SREBP proteolysis and turning off cholesterol synthesis. We here report the isolation of Chinese hamster ovary cells with a point mutation in SCAP (Y298c) that renders the protein resistant to inhibition by 25-hydroxycholesterol. Like the previously described D443N mutation, the Y298C mutation occurs within the putative sterol-sensing domain, which is part of the polytopic membrane attachment region of SCAP. Cells that express SCAP(Y298C) continued to process SREBPs in the presence of 25-hydroxycholesterol and hence they resisted killing by this sterol. In wild-type Chinese hamster ovary cells the N-linked carbohydrate chains of SCAP were mostly in the endoglycosidase H- sensitive form when cells were grown in medium containing 25- hydroxycholesterol. In contrast, when cells were grown in sterol-depleted medium, these chains were converted to an endoglycosidase H-resistant form. 25-Hydroxycholesterol had virtually no effect in cells expressing SCAP(D443N) or SCAP(Y298C). The relation between this regulated carbohydrate processing to the SCAP-regulated proteolysis of SREBP remains to be explored.
KW - Cholesterol
KW - Endoplasmic reticulum
KW - Golgi apparatus
KW - Sterol regulatory element binding protein
KW - Sterol-sensing domain
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U2 - 10.1073/pnas.95.22.12848
DO - 10.1073/pnas.95.22.12848
M3 - Article
C2 - 9789003
AN - SCOPUS:0032573056
SN - 0027-8424
VL - 95
SP - 12848
EP - 12853
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 22
ER -