Protein: Sterol regulatory element-binding protein cleavage-activating protein (SCAP) (SREBP cleavage-activating protein) (A2RRU4)
Organism: Rattus norvegicus (Rat)
Function: Escort protein required for cholesterol as well as lipid homeostasis. Regulates export of the SCAP-SREBP complex from the endoplasmic reticulum to the Golgi upon low cholesterol, thereby regulating the processing of sterol regulatory element-binding proteins (SREBPs) SREBF1/SREBP1 and SREBF2/SREBP2. At high sterol concentrations, formation of a ternary complex with INSIG (INSIG1 or INSIG2) leads to mask the ER export signal in SCAP, promoting retention of the complex in the endoplasmic reticulum. Low sterol concentrations trigger release of INSIG, a conformational change in the SSD domain of SCAP, unmasking of the ER export signal, promoting recruitment into COPII-coated vesicles and transport of the SCAP-SREBP to the Golgi: in the Golgi, SREBPs are then processed, releasing the transcription factor fragment of SREBPs from the membrane, its import into the nucleus and up-regulation of LDLR, INSIG1 and the mevalonate pathway. Binds cholesterol via its SSD domain.
Subcellular location: Endoplasmic reticulum membrane {ECO:0000250|UniProtKB:Q12770}; Multi-pass membrane protein {ECO:0000255}. Golgi apparatus membrane {ECO:0000250|UniProtKB:Q12770}; Multi-pass membrane protein {ECO:0000255}. Cytoplasmic vesicle, COPII-coated vesicle membrane {ECO:0000250|UniProtKB:P97260}; Multi-pass membrane protein {ECO:0000255}. Note=Moves from the endoplasmic reticulum to the Golgi in the absence of sterols. Requires the presence of SPRING1 for proper localization to endoplasmic reticulum. {ECO:0000250|UniProtKB:P97260, ECO:0000250|UniProtKB:Q12770}.
Interaction partners:
- Sterol regulatory element-binding protein 2
- Insulin-induced gene 2 protein
- Insulin-induced gene 1 protein
- Sterol regulatory element-binding protein 1
- Insulin-induced gene protein
- Membrane-bound transcription factor site-1 protease
- NPC intracellular cholesterol transporter 2
- E3 ubiquitin-protein ligase RNF139
Sequence:
MTLTERLREKISQAFYNHGLLCASYPIPIILFTGLCILACCYPLLKLPLPGTGPVEFSTPVKGYSPPPADSDHKQGEPSEQPEWYVGAPVAYIQQIFVKSSVSPWHRNLLAVDVFRSPLSRAFQLVEEIRNHVLRDSSGTKSLEEVCLQVTDLLPGLRKLRSLLPEHGCLLLSPGNFWQNDWERFHADPDIIGTIHQHEPKTLQTSATLKDLLFGVPGKYSGVSLYTRKRMVSYTITLVFQRYHAKFLSSLRARLMLLHPSPNCSLRAENLVHVHFKEEIGIAELIPLVTTYIILFAYIYFSTRKIDMVKSKWGLALAAVVTVLSSLLMSVGLCTLFGLTPTLNGGEIFPYLVVVIGLENVLVLTKSVVSTPVDLEVKLRIAQGLSSESWSIMKNVATELGIILIGYFTLVPAIQEFCLFAVVGLVSDFFLQMLFFTTVLSIDIRRMELADLNKRLPPESCLPSAKPVGRPARYERQLAVRPSTPHTITLQPSSFRNLRLPKRLRVIYFLARTRLAQRLIMAGTVVWIGILVYTDPAGLRTYLAAQVTEQSPLGEGSLGPMPVPSGVLPASHPDPAFSIFPPDAPKLPENQTLPGELPEHAVPAEGVQDSRAPEVTWGPEDEELWRKLSFRHWPTLFNYYNITLAKRYISLLPVIPVTLHLNPREALEGRHPQDGRTAWAPPEPLPAGLWETGPKGPGGTQTHGDITLYKVAALGLAAGIVLVLLLLCLYRVLCPRNYGQPGGGAGRRRRGELPCDDYGYAPPETEIVPLVLRGHLMDIECLASDGMLLVSCCLAGQVCVWDAQTGDCLTRIPRPGPRRDSCGGGAFEAQENWERLSDGGKASPEEPGDSPPLRRRPRGPPPPSLFGDQPDLTCLIDTNFSVQLPPEPTQPEPRHRAGCGRSRDSGYDFSRLVQRVYQEEGLAAVHMSALRPPSPGPPLPQASQEEGTAPEKGSPPLAWAPSTAGSIWSLELQGSLIVVGRSSGRLEVWDAIEGVLCCSNEEISSGITALVFLDRRIVAARLNGSLDFFSLETHTSLSPLQFRGTPGRGSSPSSPVYSSSNTVACHLTHTVPCAHQKPITALRAAAGRLVTGSQDHTLRVFRLEDSCCLFTLQGHSGAITTVYIDQTMVLASGGQDGAICLWDVLTGSRVSHTFAHRGDVTSLTCTTSCVISSGLDDFINIWDRSTGIKLYSIQQDLGCGASLGVISDNLLVTGGQGCVSFWDLNYGDLLQTVYLGKNSEAQPARQILVLDNAAIVCNFGSELSLVYVPSVLEKLD