Cited by 108Cholesterol and Lipid MetabolismPlant biochemistry and biosynthesisSteroid Chemistry and Biochemistry

Supernatant protein factor, which stimulates the conversion of squalene to lanosterol, is a cytosolic squalene transfer protein and enhances cholesterol biosynthesis

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Shibata, Norihito, Arita, Makoto, Misaki, Yuko, Dohmae, Naoshi, Takio, Koji, Ono, Teruo, Inoue, Keizo, Arai, Hiroyuki·2001·Proceedings of the National Academy of Sciences

Abstract

Squalene epoxidase, a membrane-associated enzyme that converts squalene to squalene 2,3-oxide, plays an important role in the maintenance of cholesterol homeostasis. In 1957, Bloch and colleagues identified a factor from rat liver cytosol termed “supernatant protein factor (SPF),” which promotes the squalene epoxidation catalyzed by rat liver microsomes with oxygen, NADPH, FAD, and phospholipid [Tchen, T. T. & Bloch, K. (1957) J. Biol. Chem. 226, 921–930]. Although purification of SPF by 11,000-fold was reported, no information is so far available on the primary structure or biological function of SPF. Here we report the cDNA cloning and expression of SPF from rat and human. The encoded protein of 403 amino acids belongs to a family of cytosolic lipid-binding/transfer proteins such as α-tocopherol transfer protein, cellular retinal binding protein, yeast phosphatidylinositol transfer protein (Sec14p), and squid retinal binding protein. Recombinant SPF produced in Escherichia coli enhances microsomal squalene epoxidase activity and promotes intermembrane transfer of squalene in vitro . SPF mRNA is expressed abundantly in the liver and small intestine, both of which are important sites of cholesterol biosynthesis. SPF is expressed significantly in isolated hepatocytes, but the expression level was markedly decreased after 48 h of in vitro culture. Moreover, SPF was not detectable in most of the cell lines tested, including HepG2 and McARH7777 hepatomas. Transfection of SPF cDNA in McARH7777 significantly stimulated de novo cholesterol biosynthesis. These data suggest that SPF is a cytosolic squalene transfer protein capable of regulating cholesterol biosynthesis.

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Crossref · 10.1073/pnas.041620398

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  • SQLE's enzymatic reaction requires a mitochondrial electron donor to produce 2,3-oxidosqualene, which is cyclized to lanosterol by lanosterol synthase (LSS).

    “SQLE’s enzymatic reaction requires a mitochondrial electron donor to produce 2,3-oxidosqualene, a transient intermediate that is cyclized to lanosterol by lanosterol synthase (LSS)23.”

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Authors
Shibata, N., Arita, M., Misaki, Y., Dohmae, N., Takio, K., Ono, T., Inoue, K., & Arai, H.
Affiliations
RIKEN (JP)
Venue
Proceedings of the National Academy of Sciences
Published
2001-02-27
Volume
98
Issue
5
Pages
2244-2249
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
OpenAlex
W2092465087
Cited by
108
References
24
Citations by year
2026: 2 · 2025: 2 · 2024: 2 · 2023: 1 · 2022: 3 · 2021: 4 · 2020: 5 · 2019: 2 · 2018: 1 · 2017: 1 · 2016: 3 · 2015: 1 · 2014: 3 · 2013: 4
FWCI
10.26
Type
journal article
Language
en
Open access
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Institutional Repositories DataBase (IRDB) (submittedVersion)
Topics
  • Health Sciences › Medicine › Surgery › Cholesterol and Lipid Metabolism
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Plant biochemistry and biosynthesis
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Steroid Chemistry and Biochemistry
Keywords
squalene epoxidase, cholesterol biosynthesis, cDNA cloning, hepatocytes, liver, small intestine, hepatoma cell lines, cholesterol homeostasis
MeSH terms
Amino Acid Sequence, Animals, Base Sequence, Carrier Proteins, Cholesterol, Cytosol, Female, Lanosterol, Lipoproteins, Male, Molecular Sequence Data, Recombinant Proteins, RNA, Messenger, Squalene, Tumor Cells, Cultured, Trans-Activators, Up-Regulation, Rats, Sprague-Dawley, Rats, Wistar, Sequence Homology, Amino Acid, DNA Primers, Rats

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