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Insulin induced gene 1, also known as INSIG1, is a protein which in humans is encoded by the ''INSIG1'' gene.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3638 )〕 INSIG1 is short for insulin-induced gene 1; it is located on chromosome 7 (7q36). This human gene encodes for a 277 AA long transmembrane protein with probably 6 transmembrane domains. It is localized in the ER and seems to be expressed in all tissues, especially in liver. == Function == #INSIG1 plays an important role in the SREBP-mediated regulation of cholesterol biosynthesis: by binding to the sterol-sensing domain of SCAP (SREBP cleavage activating protein) it makes the SCAP/SREBP complex stay longer in the ER, thus prohibiting SCAP from carrying activated SREBP to the golgi complex. This ultimately blocks SREBP from acting as a transcription factor for the SRE in the promoter region of the HMG-CoA-reductase gene and results in a decreased expression of HMG-CoA-reductase. #INSIG1 also binds to the sterol-sensing domain of HMG-Co-A-reductase, resulting in the enzyme's increased degradation. Both functions require the binding of INSIG1 protein via the same site. There are two other proteins whose sterol-binding sites show a great similarity to the ones of SCAP and HMG-CoA-reductase and who might thus be regulated by INSIG1 as well: *Niemann-Pick disease type C1 protein, which participates in the intracellular movement of cholesterol *Patched, the receptor for Hedgehog, a protein that contains covalently bound cholesterol Oxysterols regulate cholesterol homeostasis through liver X receptor (LXR) and sterol regulatory element-binding protein (SREBP) mediated signaling pathway. This gene is an insulin-induced gene. It encodes an endoplasmic reticulum (ER) membrane protein that plays a critical role in regulating cholesterol concentrations in cells. This protein binds to the sterol-sensing domains of SREBP cleavage-activating protein (SCAP) and HMG CoA reductase, and is essential for the sterol-mediated trafficking of the two proteins. Alternatively spliced transcript variants encoding distinct isoforms have been observed.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Insulin-induced gene 1 protein」の詳細全文を読む スポンサード リンク
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