دورية أكاديمية
Hypoxia truncates and constitutively activates the key cholesterol synthesis enzyme squalene monooxygenase.
العنوان: | Hypoxia truncates and constitutively activates the key cholesterol synthesis enzyme squalene monooxygenase. |
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المؤلفون: | Coates HW; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia., Capell-Hattam IM; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia., Olzomer EM; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia., Du X; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia., Farrell R; Prince of Wales Private Hospital, Randwick, Australia.; Chris O'Brien Lifehouse, Camperdown, Australia., Yang H; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia., Byrne FL; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia., Brown AJ; School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, Australia. |
المصدر: | ELife [Elife] 2023 Jan 19; Vol. 12. Date of Electronic Publication: 2023 Jan 19. |
نوع المنشور: | Journal Article; Research Support, Non-U.S. Gov't |
اللغة: | English |
بيانات الدورية: | Publisher: eLife Sciences Publications, Ltd Country of Publication: England NLM ID: 101579614 Publication Model: Electronic Cited Medium: Internet ISSN: 2050-084X (Electronic) Linking ISSN: 2050084X NLM ISO Abbreviation: Elife Subsets: MEDLINE |
أسماء مطبوعة: | Original Publication: Cambridge, UK : eLife Sciences Publications, Ltd., 2012- |
مواضيع طبية MeSH: | Squalene Monooxygenase*/genetics , Squalene Monooxygenase*/chemistry , Squalene Monooxygenase*/metabolism , Cholesterol*/metabolism, Humans ; Squalene ; Hypoxia ; Oxygen |
مستخلص: | Cholesterol synthesis is both energy- and oxygen-intensive, yet relatively little is known of the regulatory effects of hypoxia on pathway enzymes. We previously showed that the rate-limiting and first oxygen-dependent enzyme of the committed cholesterol synthesis pathway, squalene monooxygenase (SM), can undergo partial proteasomal degradation that renders it constitutively active. Here, we show hypoxia is a physiological trigger for this truncation, which occurs through a two-part mechanism: (1) increased targeting of SM to the proteasome via stabilization of the E3 ubiquitin ligase MARCHF6 and (2) accumulation of the SM substrate, squalene, which impedes the complete degradation of SM and liberates its truncated form. This preserves SM activity and downstream pathway flux during hypoxia. These results uncover a feedforward mechanism that allows SM to accommodate fluctuating substrate levels and may contribute to its widely reported oncogenic properties. Competing Interests: HC, IC, EO, XD, RF, HY, FB, AB No competing interests declared (© 2023, Coates et al.) |
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فهرسة مساهمة: | Keywords: Cholesterol; Hypoxia; Squalene monooxygenase; biochemistry; chemical biology; human; proteasome; protein degradation Local Abstract: [plain-language-summary] Cells need cholesterol to work properly but too much cholesterol is harmful and can contribute to atherosclerosis (narrowing of blood vessels), cancer and other diseases. Cells therefore carefully control the activity of the enzymes that are involved in making cholesterol, including an enzyme known as squalene monooxygenase. When the level of cholesterol in a cell rises, a protein called MARCHF6 adds molecules of ubiquitin to squalene monooxygenase. These molecules act as tags that direct the enzyme to be destroyed by a machine inside cells, known as the proteasome, thereby preventing further (unnecessary) production of cholesterol. Previous studies found that squalene monooxygenase is sometimes only partially broken down to make a shorter (truncated) form of the enzyme that is permanently active, even when the level of cholesterol in the cell is high. However, it was unclear what triggers this partial breakdown. The process of making cholesterol uses a lot of oxygen, yet many cancer cells thrive in tumours with low levels of oxygen. Here, Coates et al. used biochemical and cell biology approaches to study the effect of low oxygen levels on the activity of squalene monooxygenase in human cells. The experiments revealed that low oxygen levels trigger squalene monooxygenase to be partially degraded to make the truncated form of the enzyme. Firstly, MARCHF6 accumulates and adds ubiquitin to the enzyme to accelerate its delivery to the proteasome. Secondly, as the proteasome starts to degrade the enzyme, a build-up of squalene molecules impedes further breakdown of the enzyme. This mechanism preserves squalene monooxygenase activity when oxygen levels drop in cells, which may compensate for temporary oxygen shortfalls and allow cells to continue to make cholesterol. Squalene monooxygenase is overactive in individuals with a wide variety of diseases including fatty liver and prostate cancer. Drugs that block squalene monooxygenase activity have been shown to stop cancer cells from growing, but unfortunately these drugs are also toxic to mammals. These findings suggest that reducing the activity of squalene monooxygenase in more subtle ways, such as stopping it from being partially degraded, may be a more viable treatment strategy for cancer and other diseases associated with high levels of cholesterol. |
المشرفين على المادة: | EC 1.14.14.17 (Squalene Monooxygenase) 97C5T2UQ7J (Cholesterol) 7QWM220FJH (Squalene) S88TT14065 (Oxygen) |
تواريخ الأحداث: | Date Created: 20230119 Date Completed: 20230123 Latest Revision: 20230322 |
رمز التحديث: | 20230322 |
مُعرف محوري في PubMed: | PMC9851614 |
DOI: | 10.7554/eLife.82843 |
PMID: | 36655986 |
قاعدة البيانات: | MEDLINE |
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