Insulin-induced gene 1 protein

Last updated
INSIG1
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases INSIG1 , CL-6, CL6, insulin induced gene 1
External IDs OMIM: 602055; MGI: 1916289; HomoloGene: 4047; GeneCards: INSIG1; OMA:INSIG1 - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_153526

RefSeq (protein)

NP_705746

Location (UCSC) Chr 7: 155.3 – 155.31 Mb Chr 5: 28.28 – 28.28 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Insulin induced gene 1, also known as INSIG1, is a protein which in humans is encoded by the INSIG1 gene. [5] [6]

Contents

INSIG1 is short for insulin-induced gene 1; it is located on chromosome 7 (7q36). This human gene encodes for a transmembrane protein of 277 amino acids with probably 6 transmembrane domains. It is localized in the endoplasmic reticulum (ER) and seems to be expressed in all tissues, especially in liver. This gene is called an insulin-induced gene because the molecule insulin can regulate it. Importantly, the protein encoded by this gene plays a critical role in regulating cholesterol concentrations in cells.

Function

  1. 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.
  2. INSIG1 also binds to the sterol-sensing domain of HMG-CoA-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:

Oxysterols regulate cholesterol homeostasis through liver X receptor (LXR) and sterol regulatory element-binding protein (SREBP) mediated signaling pathway. 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. [6]

Regulation

INSIG1 is regulated by insulin and highly expressed in liver.

Sequence (277 AA)

MPRLHDHFWS CSCAHSARRR GPPRASTAGL PPKVGEMINV SVSGPSLLAA HGAPDADPAP RGRSAAMSGP EPGSPYPNTW HHRLLQRSLV LFSVGVVLAL VLNLLQIQRN VTLFPEEVIA TIFSSAWWVP PCCGTAAAVV GLLYPCIDSH LGEPHKFKRE WASVMRCIAV FVGINHASAK LDFANNVQLS LTLAALSLGL WWTFDRSRSG LGLGITIAFL ATLITQFLVY NGVYQYTSPD FLYIRSWLPC IFFSGGVTVG NIGRQLAMGV PEKPHSD

Synonyms

CL-6, INSIG-1, Insulin-induced gene 1 protein, MGC1405 (source: iHOP)

Interactions

INSIG1 has been shown to interact with SREBF2. [7] [8]

Related Research Articles

<span class="mw-page-title-main">Cholesterol</span> Sterol biosynthesized by all animal cells

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<span class="mw-page-title-main">HMG-CoA reductase</span> Mammalian protein found in Homo sapiens

HMG-CoA reductase is the rate-controlling enzyme of the mevalonate pathway, the metabolic pathway that produces cholesterol and other isoprenoids. HMGCR catalyzes the conversion of HMG-CoA to mevalonic acid, a necessary step in the biosynthesis of cholesterol. Normally in mammalian cells this enzyme is competitively suppressed so that its effect is controlled. This enzyme is the target of the widely available cholesterol-lowering drugs known collectively as the statins, which help treat dyslipidemia.

<span class="mw-page-title-main">Joseph L. Goldstein</span> American biochemist

Joseph Leonard Goldstein ForMemRS is an American biochemist. He received the Nobel Prize in Physiology or Medicine in 1985, along with fellow University of Texas Southwestern researcher, Michael Brown, for their studies regarding cholesterol. They discovered that human cells have low-density lipoprotein (LDL) receptors that remove cholesterol from the blood and that when LDL receptors are not present in sufficient numbers, individuals develop hypercholesterolemia and become at risk for cholesterol related diseases, notably coronary heart disease. Their studies led to the development of statin drugs.

<span class="mw-page-title-main">Michael Stuart Brown</span> American geneticist and Nobel laureate (born 1941)

Michael Stuart Brown ForMemRS NAS AAA&S APS is an American geneticist and Nobel laureate. He was awarded the Nobel Prize in Physiology or Medicine with Joseph L. Goldstein in 1985 for describing the regulation of cholesterol metabolism.

In biochemistry, lipogenesis is the conversion of fatty acids and glycerol into fats, or a metabolic process through which acetyl-CoA is converted to triglyceride for storage in fat. Lipogenesis encompasses both fatty acid and triglyceride synthesis, with the latter being the process by which fatty acids are esterified to glycerol before being packaged into very-low-density lipoprotein (VLDL). Fatty acids are produced in the cytoplasm of cells by repeatedly adding two-carbon units to acetyl-CoA. Triacylglycerol synthesis, on the other hand, occurs in the endoplasmic reticulum membrane of cells by bonding three fatty acid molecules to a glycerol molecule. Both processes take place mainly in liver and adipose tissue. Nevertheless, it also occurs to some extent in other tissues such as the gut and kidney. A review on lipogenesis in the brain was published in 2008 by Lopez and Vidal-Puig. After being packaged into VLDL in the liver, the resulting lipoprotein is then secreted directly into the blood for delivery to peripheral tissues.

<span class="mw-page-title-main">Sterol regulatory element-binding protein</span> Protein family

Sterol regulatory element-binding proteins (SREBPs) are transcription factors that bind to the sterol regulatory element DNA sequence TCACNCCAC. Mammalian SREBPs are encoded by the genes SREBF1 and SREBF2. SREBPs belong to the basic-helix-loop-helix leucine zipper class of transcription factors. Unactivated SREBPs are attached to the nuclear envelope and endoplasmic reticulum membranes. In cells with low levels of sterols, SREBPs are cleaved to a water-soluble N-terminal domain that is translocated to the nucleus. These activated SREBPs then bind to specific sterol regulatory element DNA sequences, thus upregulating the synthesis of enzymes involved in sterol biosynthesis. Sterols in turn inhibit the cleavage of SREBPs and therefore synthesis of additional sterols is reduced through a negative feed back loop.

<span class="mw-page-title-main">Liver X receptor</span> Nuclear receptor

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<span class="mw-page-title-main">SREBP cleavage-activating protein</span> Protein-coding gene in the species Homo sapiens

Sterol regulatory element-binding protein cleavage-activating protein, also known as SREBP cleavage-activating protein or SCAP, is a protein that in humans is encoded by the SCAP gene.

<span class="mw-page-title-main">Sterol regulatory element-binding protein 1</span> Protein-coding gene in the species Homo sapiens

Sterol regulatory element-binding transcription factor 1 (SREBF1) also known as sterol regulatory element-binding protein 1 (SREBP-1) is a protein that in humans is encoded by the SREBF1 gene.

<span class="mw-page-title-main">Sterol regulatory element-binding protein 2</span> Protein-coding gene in the species Homo sapiens

Sterol regulatory element-binding protein 2 (SREBP-2) also known as sterol regulatory element binding transcription factor 2 (SREBF2) is a protein that in humans is encoded by the SREBF2 gene.

<span class="mw-page-title-main">Membrane-bound transcription factor site-1 protease</span> Mammalian protein found in Homo sapiens

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Membrane-bound transcription factor site-2 protease, also known as S2P endopeptidase or site-2 protease (S2P), is an enzyme encoded by the MBTPS2 gene which liberates the N-terminal fragment of sterol regulatory element-binding protein (SREBP) transcription factors from membranes. S2P cleaves the transmembrane domain of SREPB, making it a member of the class of intramembrane proteases.

<span class="mw-page-title-main">PGRMC1</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">ABCA7</span> Protein-coding gene in the species Homo sapiens

ATP-binding cassette sub-family A member 7 is a protein that in humans is encoded by the ABCA7 gene.

<span class="mw-page-title-main">OSBP</span> Protein-coding gene in the species Homo sapiens

Oxysterol-binding protein 1 is a protein that in humans is encoded by the OSBP gene.

<span class="mw-page-title-main">INSIG2</span> Protein-coding gene in the species Homo sapiens

Insulin induced gene 2, also known as INSIG2, is a protein which in humans is encoded by the INSIG2 gene.

miR-33 Non-coding RNA in the species Homo sapiens

miR-33 is a family of microRNA precursors, which are processed by the Dicer enzyme to give mature microRNAs. miR-33 is found in several animal species, including humans. In some species there is a single member of this family which gives the mature product mir-33. In humans there are two members of this family called mir-33a and mir-33b, which are located in intronic regions within two protein-coding genes for Sterol regulatory element-binding proteins respectively.

<span class="mw-page-title-main">STARD4</span> Protein-coding gene in the species Homo sapiens

StAR-related lipid transfer protein 4 (STARD4) is a soluble protein involved in cholesterol transport. It can transfer up to 7 sterol molecules per minute between artificial membranes.

A sterol-sensing domain (SSD) is a protein domain which consists of 180 amino acids forming five transmembrane segments capable of binding sterol groups. This type of domain is present in proteins involved in cholesterol metabolism and signalling.

References

  1. 1 2 3 GRCh38: Ensembl release 89: ENSG00000186480 Ensembl, May 2017
  2. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000045294 Ensembl, May 2017
  3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. Peng Y, Schwarz EJ, Lazar MA, Genin A, Spinner NB, Taub R (Aug 1997). "Cloning, human chromosomal assignment, and adipose and hepatic expression of the CL-6/INSIG1 gene". Genomics. 43 (3): 278–84. doi: 10.1006/geno.1997.4821 . PMID   9268630.
  6. 1 2 "Entrez Gene: INSIG1 insulin induced gene 1".
  7. Dobrosotskaya IY, Goldstein JL, Brown MS, Rawson RB (Sep 2003). "Reconstitution of sterol-regulated endoplasmic reticulum-to-Golgi transport of SREBP-2 in insect cells by co-expression of mammalian SCAP and Insigs". The Journal of Biological Chemistry. 278 (37): 35837–43. doi: 10.1074/jbc.M306476200 . PMID   12842885.
  8. Yang T, Espenshade PJ, Wright ME, Yabe D, Gong Y, Aebersold R, Goldstein JL, Brown MS (Aug 2002). "Crucial step in cholesterol homeostasis: sterols promote binding of SCAP to INSIG-1, a membrane protein that facilitates retention of SREBPs in ER". Cell. 110 (4): 489–500. doi: 10.1016/S0092-8674(02)00872-3 . PMID   12202038. S2CID   15052132.

Further reading