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Saito H, Tachiura W, Nishimura M, Shimizu M, Sato R, Yamauchi Y. Hydroxylation site-specific and production-dependent effects of endogenous oxysterols on cholesterol homeostasis: Implications for SREBP-2 and LXR. J Biol Chem 2022; 299:102733. [PMID: 36423680 PMCID: PMC9792893 DOI: 10.1016/j.jbc.2022.102733] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 10/26/2022] [Accepted: 11/14/2022] [Indexed: 11/23/2022] Open
Abstract
The cholesterol metabolites, oxysterols, play central roles in cholesterol feedback control. They modulate the activity of two master transcription factors that control cholesterol homeostatic responses, sterol regulatory element-binding protein-2 (SREBP-2) and liver X receptor (LXR). Although the role of exogenous oxysterols in regulating these transcription factors has been well established, whether endogenously synthesized oxysterols similarly control both SREBP-2 and LXR remains poorly explored. Here, we carefully validate the role of oxysterols enzymatically synthesized within cells in cholesterol homeostatic responses. We first show that SREBP-2 responds more sensitively to exogenous oxysterols than LXR in Chinese hamster ovary cells and rat primary hepatocytes. We then show that 25-hydroxycholesterol (25-HC), 27-hydroxycholesterol, and 24S-hydroxycholesterol endogenously synthesized by CH25H, CYP27A1, and CYP46A1, respectively, suppress SREBP-2 activity at different degrees by stabilizing Insig (insulin-induced gene) proteins, whereas 7α-hydroxycholesterol has little impact on SREBP-2. These results demonstrate the role of site-specific hydroxylation of endogenous oxysterols. In contrast, the expression of CH25H, CYP46A1, CYP27A1, or CYP7A1 fails to induce LXR target gene expression. We also show the 25-HC production-dependent suppression of SREBP-2 using a tetracycline-inducible CH25H expression system. To induce 25-HC production physiologically, murine macrophages are stimulated with a Toll-like receptor 4 ligand, and its effect on SREBP-2 and LXR is examined. The results also suggest that de novo synthesis of 25-HC preferentially regulates SREBP-2 activity. Finally, we quantitatively determine the specificity of the four cholesterol hydroxylases in living cells. Based on our current findings, we conclude that endogenous side-chain oxysterols primarily regulate the activity of SREBP-2, not LXR.
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Affiliation(s)
- Hodaka Saito
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Wakana Tachiura
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Mizuki Nishimura
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Makoto Shimizu
- Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Ryuichiro Sato
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan
| | - Yoshio Yamauchi
- Laboratory of Food Biochemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan,AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan,For correspondence: Yoshio Yamauchi
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2
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Wilfahrt D, Philips RL, Lama J, Kizerwetter M, Shapiro MJ, McCue SA, Kennedy MM, Rajcula MJ, Zeng H, Shapiro VS. Histone deacetylase 3 represses cholesterol efflux during CD4 + T-cell activation. eLife 2021; 10:e70978. [PMID: 34854376 PMCID: PMC8639145 DOI: 10.7554/elife.70978] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 11/15/2021] [Indexed: 12/14/2022] Open
Abstract
After antigenic activation, quiescent naive CD4+ T cells alter their metabolism to proliferate. This metabolic shift increases production of nucleotides, amino acids, fatty acids, and sterols. Here, we show that histone deacetylase 3 (HDAC3) is critical for activation of murine peripheral CD4+ T cells. HDAC3-deficient CD4+ T cells failed to proliferate and blast after in vitro TCR/CD28 stimulation. Upon T-cell activation, genes involved in cholesterol biosynthesis are upregulated while genes that promote cholesterol efflux are repressed. HDAC3-deficient CD4+ T cells had reduced levels of cellular cholesterol both before and after activation. HDAC3-deficient cells upregulate cholesterol synthesis appropriately after activation, but fail to repress cholesterol efflux; notably, they overexpress cholesterol efflux transporters ABCA1 and ABCG1. Repression of these genes is the primary function for HDAC3 in peripheral CD4+ T cells, as addition of exogenous cholesterol restored proliferative capacity. Collectively, these findings demonstrate HDAC3 is essential during CD4+ T-cell activation to repress cholesterol efflux.
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Affiliation(s)
- Drew Wilfahrt
- Department of Immunology, Mayo ClinicRochesterUnited States
| | | | - Jyoti Lama
- Department of Immunology, Mayo ClinicRochesterUnited States
| | | | | | | | | | | | - Hu Zeng
- Department of Immunology, Mayo ClinicRochesterUnited States
- Division of Rheumatology, Department of Medicine, Mayo ClinicRochesterUnited States
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3
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Lawrence GD. Perspective: The Saturated Fat-Unsaturated Oil Dilemma: Relations of Dietary Fatty Acids and Serum Cholesterol, Atherosclerosis, Inflammation, Cancer, and All-Cause Mortality. Adv Nutr 2021; 12:647-656. [PMID: 33693484 PMCID: PMC8166560 DOI: 10.1093/advances/nmab013] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/23/2020] [Accepted: 01/21/2021] [Indexed: 12/27/2022] Open
Abstract
PUFAs are known to regulate cholesterol synthesis and cellular uptake by multiple mechanisms that do not involve SFAs. Polymorphisms in any of the numerous proteins involved in cholesterol homeostasis, as a result of genetic variation, could lead to higher or lower serum cholesterol. PUFAs are susceptible to lipid peroxidation, which can lead to oxidative stress, inflammation, atherosclerosis, cancer, and disorders associated with inflammation, such as insulin resistance, arthritis, and numerous inflammatory syndromes. Eicosanoids from arachidonic acid are among the most powerful mediators that initiate an immune response, and a wide range of PUFA metabolites regulate numerous physiological processes. There is a misconception that dietary SFAs can cause inflammation, although endogenous palmitic acid is converted to ceramides and other cell constituents involved in an inflammatory response after it is initiated by lipid mediators derived from PUFAs. This article will discuss the many misconceptions regarding how dietary lipids regulate serum cholesterol, the fact that all-cause death rate is higher in humans with low compared with normal or moderately elevated serum total cholesterol, the numerous adverse effects of increasing dietary PUFAs or carbohydrate relative to SFAs, as well as metabolic conversion of PUFAs to SFAs and MUFAs as a protective mechanism. Consequently, dietary saturated fats seem to be less harmful than the proposed alternatives.
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Affiliation(s)
- Glen D Lawrence
- Department of Chemistry and Biochemistry, Long Island University, Brooklyn, NY, USA
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4
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Grunkemeyer TJ, Ghosh S, Patel AM, Sajja K, Windak J, Basrur V, Kim Y, Nesvizhskii AI, Kennedy RT, Marsh ENG. The antiviral enzyme viperin inhibits cholesterol biosynthesis. J Biol Chem 2021; 297:100824. [PMID: 34029588 PMCID: PMC8254119 DOI: 10.1016/j.jbc.2021.100824] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 04/26/2021] [Accepted: 05/20/2021] [Indexed: 01/02/2023] Open
Abstract
Many enveloped viruses bud from cholesterol-rich lipid rafts on the cell membrane. Depleting cellular cholesterol impedes this process and results in viral particles with reduced viability. Viperin (Virus Inhibitory Protein, Endoplasmic Reticulum-associated, Interferon iNducible) is an endoplasmic reticulum membrane-associated enzyme that exerts broad-ranging antiviral effects, including inhibiting the budding of some enveloped viruses. However, the relationship between viperin expression and the retarded budding of virus particles from lipid rafts on the cell membrane is unclear. Here, we investigated the effect of viperin expression on cholesterol biosynthesis using transiently expressed genes in the human cell line human embryonic kidney 293T (HEK293T). We found that viperin expression reduces cholesterol levels by 20% to 30% in these cells. Following this observation, a proteomic screen of the viperin interactome identified several cholesterol biosynthetic enzymes among the top hits, including lanosterol synthase (LS) and squalene monooxygenase (SM), which are enzymes that catalyze key steps in establishing the sterol carbon skeleton. Coimmunoprecipitation experiments confirmed that viperin, LS, and SM form a complex at the endoplasmic reticulum membrane. While coexpression of viperin was found to significantly inhibit the specific activity of LS in HEK293T cell lysates, coexpression of viperin had no effect on the specific activity of SM, although did reduce SM protein levels by approximately 30%. Despite these inhibitory effects, the coexpression of neither LS nor SM was able to reverse the viperin-induced depletion of cellular cholesterol levels, possibly because viperin is highly expressed in transfected HEK293T cells. Our results establish a link between viperin expression and downregulation of cholesterol biosynthesis that helps explain viperin's antiviral effects against enveloped viruses.
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Affiliation(s)
| | - Soumi Ghosh
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Ayesha M Patel
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Keerthi Sajja
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - James Windak
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Venkatesha Basrur
- Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA
| | - Youngsoo Kim
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Alexey I Nesvizhskii
- Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA; Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan, USA
| | - Robert T Kennedy
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - E Neil G Marsh
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA; Department of Biological Chemisrty, University of Michigan, Ann Arbor, Michigan, USA.
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5
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Sharpe LJ, Coates HW, Brown AJ. Post-translational control of the long and winding road to cholesterol. J Biol Chem 2021; 295:17549-17559. [PMID: 33453997 DOI: 10.1074/jbc.rev120.010723] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/12/2020] [Indexed: 01/19/2023] Open
Abstract
The synthesis of cholesterol requires more than 20 enzymes, many of which are intricately regulated. Post-translational control of these enzymes provides a rapid means for modifying flux through the pathway. So far, several enzymes have been shown to be rapidly degraded through the ubiquitin-proteasome pathway in response to cholesterol and other sterol intermediates. Additionally, several enzymes have their activity altered through phosphorylation mechanisms. Most work has focused on the two rate-limiting enzymes: 3-hydroxy-3-methylglutaryl CoA reductase and squalene monooxygenase. Here, we review current literature in the area to define some common themes in the regulation of the entire cholesterol synthesis pathway. We highlight the rich variety of inputs controlling each enzyme, discuss the interplay that exists between regulatory mechanisms, and summarize findings that reveal an intricately coordinated network of regulation along the cholesterol synthesis pathway. We provide a roadmap for future research into the post-translational control of cholesterol synthesis, and no doubt the road ahead will reveal further twists and turns for this fascinating pathway crucial for human health and disease.
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Affiliation(s)
- Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Hudson W Coates
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
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6
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Wangeline MA, Hampton RY. An autonomous, but INSIG-modulated, role for the sterol sensing domain in mallostery-regulated ERAD of yeast HMG-CoA reductase. J Biol Chem 2020; 296:100063. [PMID: 33184059 PMCID: PMC7948459 DOI: 10.1074/jbc.ra120.015910] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/01/2020] [Accepted: 11/12/2020] [Indexed: 01/23/2023] Open
Abstract
HMG-CoA reductase (HMGR) undergoes feedback-regulated degradation as part of sterol pathway control. Degradation of the yeast HMGR isozyme Hmg2 is controlled by the sterol pathway intermediate GGPP, which causes misfolding of Hmg2, leading to degradation by the HRD pathway; we call this process mallostery. We evaluated the role of the Hmg2 sterol sensing domain (SSD) in mallostery, as well as the involvement of the highly conserved INSIG proteins. We show that the Hmg2 SSD is critical for regulated degradation of Hmg2 and required for mallosteric misfolding of GGPP as studied by in vitro limited proteolysis. The Hmg2 SSD functions independently of conserved yeast INSIG proteins, but its function was modulated by INSIG, thus imposing a second layer of control on Hmg2 regulation. Mutant analyses indicated that SSD-mediated mallostery occurred prior to and independent of HRD-dependent ubiquitination. GGPP-dependent misfolding was still extant but occurred at a much slower rate in the absence of a functional SSD, indicating that the SSD facilitates a physiologically useful rate of GGPP response and implying that the SSD is not a binding site for GGPP. Nonfunctional SSD mutants allowed us to test the importance of Hmg2 quaternary structure in mallostery: a nonresponsive Hmg2 SSD mutant strongly suppressed regulation of a coexpressed, normal Hmg2. Finally, we have found that GGPP-regulated misfolding occurred in detergent-solubilized Hmg2, a feature that will allow next-level analysis of the mechanism of this novel tactic of ligand-regulated misfolding.
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Affiliation(s)
- Margaret A Wangeline
- Division of Biological Sciences, the Section of Cell and Developmental Biology, UCSD, La Jolla, California, USA
| | - Randolph Y Hampton
- Division of Biological Sciences, the Section of Cell and Developmental Biology, UCSD, La Jolla, California, USA.
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7
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El-Zeftawy M, Ali SAEM, Salah S, Hafez HS. The functional nutritional and regulatory activities of calcium supplementation from eggshell for obesity disorders management. J Food Biochem 2020; 44:e13313. [PMID: 32497284 DOI: 10.1111/jfbc.13313] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 05/08/2020] [Accepted: 05/11/2020] [Indexed: 12/15/2022]
Abstract
The present study was to investigate the effective role of renewable sources of Ca+2 from eggshell (ES) with different doses to restrict obesity disorders. Rats were classified as follows, G1 : normal diet for 26 weeks; G2 : high-fat diet (HFD) for 26 weeks; G3 , G4 , and G5 were supplemented with HFD for 16 weeks and treated with 7.2 g Ca+2 ES/Kg rat chow, 18 g Ca+2 ES/Kg rat chow, and 2% diet containing fat (DCF), respectively, for the remaining 10 weeks. Results revealed a significant effect of the low dose of Ca+2 supplement in form of ES than high dose and 2% DCF; on basis of anthropometric parameters, lipid, leptin, adiponectin, thyroid hormones, Ca+2 , 25-hydroxyl vitamin-D, and oxidative and inflammatory parameters were regulated. Results were confirmed with the histopathological study. Therefore, it was concluded that Ca+2 supplementation can be used as a beneficial source for obesity management with anticholesterol actions. PRACTICAL APPLICATIONS: Obesity represented public health hazards. The eggshell is one of the waste products that contain a high percentage of Ca+2 . The current data exposed using a low dose of ES as a new source of Ca+2 supplement for treatment of HFD rats leads to significant enhancement of lipid profiles, liver enzymes, kidney functions, leptin, adiponectin, Ca+2 , 25(OH)-D, TSH, fT4, and PTH levels. Also, there was a reduction in weight gain, Bwt, BMI, BG, insulin, and HOMA-IR. Moreover, the oxidant-pro-oxidant system was improved in both hepatic and adipose tissues where NO and TBARS concentrations were diminished, and SOD specific activity was elevated. Additionally, TNF-α and ADAM17 expression were downregulated. Hence, it was concluded that there was good evidence that diets supplemented with ES were associated with the reduction of obesity complications especially regulating fat processing and storage in the body.
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Affiliation(s)
- Marwa El-Zeftawy
- Biochemistry Department, Faculty of Veterinary Medicine, New Valley University, New Valley, Egypt.,Biological Screening and Preclinical Trial Lab, Biochemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Samar Abd-El Mohsen Ali
- Nutrition Department, High Institute of Public Health, Alexandria University, Alexandria, Egypt
| | - Sally Salah
- Nutrition Department, Allied Medical Sciences, Pharos University, Alexandria, Egypt
| | - Hani S Hafez
- Faculty of Science, Zoology Department, Suez University, Suez, Egypt
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8
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Capell-Hattam IM, Sharpe LJ, Qian L, Hart-Smith G, Prabhu AV, Brown AJ. Twin enzymes, divergent control: The cholesterogenic enzymes DHCR14 and LBR are differentially regulated transcriptionally and post-translationally. J Biol Chem 2020; 295:2850-2865. [PMID: 31911440 PMCID: PMC7049974 DOI: 10.1074/jbc.ra119.011323] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/13/2019] [Indexed: 01/07/2023] Open
Abstract
Cholesterol synthesis is a tightly regulated process, both transcriptionally and post-translationally. Transcriptional control of cholesterol synthesis is relatively well-understood. However, of the ∼20 enzymes in cholesterol biosynthesis, post-translational regulation has only been examined for a small number. Three of the four sterol reductases in cholesterol production, 7-dehydrocholesterol reductase (DHCR7), 14-dehydrocholesterol reductase (DHCR14), and lamin-B receptor (LBR), share evolutionary ties with a high level of sequence homology and predicted structural homology. DHCR14 and LBR uniquely share the same Δ-14 reductase activity in cholesterol biosynthesis, yet little is known about their post-translational regulation. We have previously identified specific modes of post-translational control of DHCR7, but it is unknown whether these regulatory mechanisms are shared by DHCR14 and LBR. Using CHO-7 cells stably expressing epitope-tagged DHCR14 or LBR, we investigated the post-translational regulation of these enzymes. We found that DHCR14 and LBR undergo differential post-translational regulation, with DHCR14 being rapidly turned over, triggered by cholesterol and other sterol intermediates, whereas LBR remained stable. DHCR14 is degraded via the ubiquitin-proteasome system, and we identified several DHCR14 and DHCR7 putative interaction partners, including a number of E3 ligases that modulate DHCR14 levels. Interestingly, we found that gene expression across an array of human tissues showed a negative relationship between the C14-sterol reductases; one enzyme or the other tends to be predominantly expressed in each tissue. Overall, our findings indicate that whereas LBR tends to be the constitutively active C14-sterol reductase, DHCR14 levels are tunable, responding to the local cellular demands for cholesterol.
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Affiliation(s)
- Isabelle M Capell-Hattam
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Lydia Qian
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Gene Hart-Smith
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia; Department of Molecular Sciences, Macquarie University, Macquarie Park, New South Wales 2109, Australia
| | - Anika V Prabhu
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia.
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9
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Sarkar SK, Foo ACY, Matyas A, Asikhia I, Kosenko T, Goto NK, Vergara-Jaque A, Lagace TA. A transient amphipathic helix in the prodomain of PCSK9 facilitates binding to low-density lipoprotein particles. J Biol Chem 2020; 295:2285-2298. [PMID: 31949048 PMCID: PMC7039556 DOI: 10.1074/jbc.ra119.010221] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 01/13/2020] [Indexed: 01/07/2023] Open
Abstract
Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a ligand of low-density lipoprotein (LDL) receptor (LDLR) that promotes LDLR degradation in late endosomes/lysosomes. In human plasma, 30–40% of PCSK9 is bound to LDL particles; however, the physiological significance of this interaction remains unknown. LDL binding in vitro requires a disordered N-terminal region in PCSK9's prodomain. Here, we report that peptides corresponding to a predicted amphipathic α-helix in the prodomain N terminus adopt helical structure in a membrane-mimetic environment. This effect was greatly enhanced by an R46L substitution representing an atheroprotective PCSK9 loss-of-function mutation. A helix-disrupting proline substitution within the putative α-helical motif in full-length PCSK9 lowered LDL binding affinity >5-fold. Modeling studies suggested that the transient α-helix aligns multiple polar residues to interact with positively charged residues in the C-terminal domain. Gain-of-function PCSK9 mutations associated with familial hypercholesterolemia (FH) and clustered at the predicted interdomain interface (R469W, R496W, and F515L) inhibited LDL binding, which was completely abolished in the case of the R496W variant. These findings shed light on allosteric conformational changes in PCSK9 required for high-affinity binding to LDL particles. Moreover, the initial identification of FH-associated mutations that diminish PCSK9's ability to bind LDL reported here supports the notion that PCSK9-LDL association in the circulation inhibits PCSK9 activity.
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Affiliation(s)
- Samantha K Sarkar
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Alexander C Y Foo
- Department of Chemistry and Biomolecular Sciences, Faculty of Science, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Angela Matyas
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Ikhuosho Asikhia
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Tanja Kosenko
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
| | - Natalie K Goto
- Department of Chemistry and Biomolecular Sciences, Faculty of Science, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Ariela Vergara-Jaque
- Center for Bioinformatics and Molecular Simulation, Universidad de Talca, Talca, Chile; Millennium Nucleus of Ion Channels-associated Diseases (MiNICAD), 3460000 Talca, Chile
| | - Thomas A Lagace
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada.
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10
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Johnson KA, Endapally S, Vazquez DC, Infante RE, Radhakrishnan A. Ostreolysin A and anthrolysin O use different mechanisms to control movement of cholesterol from the plasma membrane to the endoplasmic reticulum. J Biol Chem 2019; 294:17289-17300. [PMID: 31597703 DOI: 10.1074/jbc.ra119.010393] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 10/08/2019] [Indexed: 01/30/2023] Open
Abstract
Recent studies using two cholesterol-binding bacterial toxin proteins, perfringolysin O (PFO) and domain 4 of anthrolysin O (ALOD4), have shown that cholesterol in the plasma membranes (PMs) of animal cells resides in three distinct pools. The first pool comprises mobile cholesterol, accessible to both PFO and ALOD4, that is rapidly transported to the endoplasmic reticulum (ER) to signal cholesterol excess and maintain cholesterol homeostasis. The second is a sphingomyelin (SM)-sequestered pool inaccessible to PFO and ALOD4 but that becomes accessible by treatment with SM-degrading sphingomyelinase (SMase). The third is an essential pool also inaccessible to PFO and ALOD4 that cannot be liberated by SMase treatment. The accessible cholesterol pool can be trapped on PMs of live cells by nonlytic ALOD4, blocking its transport to the ER. However, studies of the two other pools have been hampered by a lack of available tools. Here, we used ostreolysin A (OlyA), which specifically binds SM/cholesterol complexes in membranes, to study the SM-sequestered cholesterol pool. Binding of nonlytic OlyA to SM/cholesterol complexes in PMs of live cells depleted the accessible PM cholesterol pool detectable by ALOD4. Consequently, transport of accessible cholesterol from PM to ER ceased, thereby activating SREBP transcription factors and increasing cholesterol synthesis. Thus, OlyA and ALOD4 both control movement of PM cholesterol, but through different lipid-binding mechanisms. We also found that PM-bound OlyA was rapidly internalized into cells, whereas PM-bound ALOD4 remained on the cell surface. Our findings establish OlyA and ALOD4 as complementary tools to investigate cellular cholesterol transport.
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Affiliation(s)
- Kristen A Johnson
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Shreya Endapally
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Danya C Vazquez
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Rodney E Infante
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390 .,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, Texas 75390.,Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Arun Radhakrishnan
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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11
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Byun S, Jung H, Chen J, Kim YC, Kim DH, Kong B, Guo G, Kemper B, Kemper JK. Phosphorylation of hepatic farnesoid X receptor by FGF19 signaling-activated Src maintains cholesterol levels and protects from atherosclerosis. J Biol Chem 2019; 294:8732-8744. [PMID: 30996006 DOI: 10.1074/jbc.ra119.008360] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/12/2019] [Indexed: 12/13/2022] Open
Abstract
The bile acid (BA) nuclear receptor, farnesoid X receptor (FXR/NR1H4), maintains metabolic homeostasis by transcriptional control of numerous genes, including an intestinal hormone, fibroblast growth factor-19 (FGF19; FGF15 in mice). Besides activation by BAs, the gene-regulatory function of FXR is also modulated by hormone or nutrient signaling-induced post-translational modifications. Recently, phosphorylation at Tyr-67 by the FGF15/19 signaling-activated nonreceptor tyrosine kinase Src was shown to be important for FXR function in BA homeostasis. Here, we examined the role of this FXR phosphorylation in cholesterol regulation. In both hepatic FXR-knockout and FXR-knockdown mice, reconstitution of FXR expression up-regulated cholesterol transport genes for its biliary excretion, including scavenger receptor class B member 1 (Scarb1) and ABC subfamily G member 8 (Abcg5/8), decreased hepatic and plasma cholesterol levels, and increased biliary and fecal cholesterol levels. Of note, these sterol-lowering effects were blunted by substitution of Phe for Tyr-67 in FXR. Moreover, consistent with Src's role in phosphorylating FXR, Src knockdown impaired cholesterol regulation in mice. In hypercholesterolemic apolipoprotein E-deficient mice, expression of FXR, but not Y67F-FXR, ameliorated atherosclerosis, whereas Src down-regulation exacerbated it. Feeding or treatment with an FXR agonist induced Abcg5/8 and Scarb1 expression in WT, but not FGF15-knockout, mice. Furthermore, FGF19 treatment increased occupancy of FXR at Abcg5/8 and Scarb1, expression of these genes, and cholesterol efflux from hepatocytes. These FGF19-mediated effects were blunted by the Y67F-FXR substitution or Src down-regulation or inhibition. We conclude that phosphorylation of hepatic FXR by FGF15/19-induced Src maintains cholesterol homeostasis and protects against atherosclerosis.
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Affiliation(s)
- Sangwon Byun
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
| | - Hyunkyung Jung
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
| | - Jinjing Chen
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
| | - Young-Chae Kim
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
| | - Dong-Hyun Kim
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
| | - Bo Kong
- the Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey 08854
| | - Grace Guo
- the Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey 08854
| | - Byron Kemper
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
| | - Jongsook Kim Kemper
- From the Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801 and
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12
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Chua NK, Hart-Smith G, Brown AJ. Non-canonical ubiquitination of the cholesterol-regulated degron of squalene monooxygenase. J Biol Chem 2019; 294:8134-8147. [PMID: 30940729 DOI: 10.1074/jbc.ra119.007798] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 03/11/2019] [Indexed: 12/21/2022] Open
Abstract
Squalene monooxygenase (SM) is a rate-limiting enzyme in cholesterol synthesis. The region comprising the first 100 amino acids, termed SM N100, represents the shortest cholesterol-responsive degron and enables SM to sense excess cholesterol in the endoplasmic reticulum (ER) membrane. Cholesterol accelerates the ubiquitination of SM by membrane-associated ring-CH type finger 6 (MARCH6), a key E3 ubiquitin ligase involved in ER-associated degradation. However, the ubiquitination site required for cholesterol regulation of SM N100 is unknown. Here, we used SM N100 fused to GFP as a model degron to recapitulate cholesterol-mediated SM degradation and show that neither SM lysine residues nor the N terminus impart instability. Instead, we discovered four serines (Ser-59, Ser-61, Ser-83, and Ser-87) that are critical for cholesterol-accelerated degradation, with MS analysis confirming Ser-83 as a ubiquitination site. Notably, these two clusters of closely spaced serine residues are located in disordered domains flanking a 12-amino acid-long amphipathic helix (residues Gln-62-Leu-73) that together confer cholesterol responsiveness. In summary, our findings reveal the degron architecture of SM N100, introducing the role of non-canonical ubiquitination sites and deepening our molecular understanding of how SM is degraded in response to cholesterol.
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Affiliation(s)
- Ngee Kiat Chua
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, New South Wales 2052, Australia
| | - Gene Hart-Smith
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, New South Wales 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, UNSW Sydney, New South Wales 2052, Australia.
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13
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Kong Y, Cheng L, Mao F, Zhang Z, Zhang Y, Farah E, Bosler J, Bai Y, Ahmad N, Kuang S, Li L, Liu X. Inhibition of cholesterol biosynthesis overcomes enzalutamide resistance in castration-resistant prostate cancer (CRPC). J Biol Chem 2018; 293:14328-14341. [PMID: 30089652 DOI: 10.1074/jbc.ra118.004442] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/02/2018] [Indexed: 01/01/2023] Open
Abstract
Enzalutamide, a nonsteroidal second-generation antiandrogen, has been recently approved for the management of castration-resistant prostate cancer (CRPC). Although patients can benefit from enzalutamide at the beginning of this therapy, acquired enzalutamide resistance usually occurs within a short period. This motivated us to investigate the mechanism involved and possible approaches for overcoming enzalutamide resistance in CRPC. In the present study, we found that 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), a crucial enzyme in the mevalonate pathway for sterol biosynthesis, is elevated in enzalutamide-resistant prostate cancer cell lines. HMGCR knockdown could resensitize these cells to the drug, and HMGCR overexpression conferred resistance to it, suggesting that aberrant HMGCR expression is an important enzalutamide-resistance mechanism in prostate cancer cells. Furthermore, enzalutamide-resistant prostate cancer cells were more sensitive to statins, which are HMGCR inhibitors. Of note, a combination of simvastatin and enzalutamide significantly inhibited the growth of enzalutamide-resistant prostate cancer cells in vitro and tumors in vivo Mechanistically, simvastatin decreased protein levels of the androgen receptor (AR), which was further reduced in combination with enzalutamide. We observed that the decrease in AR may occur through simvastatin-mediated inhibition of the mTOR pathway, whose activation was associated with increased HMGCR and AR expression. These results indicate that simvastatin enhances the efficacy of enzalutamide-based therapy, highlighting the therapeutic potential of statins to overcome enzalutamide resistance in CRPC.
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Affiliation(s)
- Yifan Kong
- From the Departments of Biochemistry and.,Animal Sciences and
| | - Lijun Cheng
- the Department of Biomedical Informatics, Ohio State University, Columbus, Ohio 43210, and
| | - Fengyi Mao
- From the Departments of Biochemistry and.,Animal Sciences and
| | | | | | - Elia Farah
- From the Departments of Biochemistry and
| | | | | | - Nihal Ahmad
- the Department of Dermatology, University of Wisconsin, Madison, Wisconsin 53715
| | - Shihuan Kuang
- Animal Sciences and.,the Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
| | - Lang Li
- the Department of Biomedical Informatics, Ohio State University, Columbus, Ohio 43210, and
| | - Xiaoqi Liu
- From the Departments of Biochemistry and .,the Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
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14
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Wangeline MA, Hampton RY. "Mallostery"-ligand-dependent protein misfolding enables physiological regulation by ERAD. J Biol Chem 2018; 293:14937-14950. [PMID: 30018140 DOI: 10.1074/jbc.ra118.001808] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 06/06/2018] [Indexed: 12/19/2022] Open
Abstract
HMG-CoA reductase (HMGR) undergoes regulated degradation as part of feedback control of the sterol pathway. In yeast, the stability of the HMGR isozyme Hmg2 is controlled by the 20-carbon isoprenoid geranylgeranyl pyrophosphate (GGPP). Increasing GGPP levels cause more efficient degradation by the HMG-CoA reductase degradation (HRD) pathway, allowing for feedback regulation of HMGR. The HRD pathway is critical for the endoplasmic reticulum (ER)-associated degradation (ERAD) of misfolded ER proteins. Here, we have explored GGPP's role in HRD-dependent Hmg2 degradation. We found that GGPP potently regulates Hmg2 levels in vivo and causes reversible Hmg2 misfolding at nanomolar concentrations in vitro These GGPP-mediated effects were absent in several stabilized or nonregulated Hmg2 mutants. Consistent with its high potency, GGPP's effects were highly specific such that other structurally related molecules were ineffective in altering Hmg2 structure. For instance, two closely related GGPP analogues, 2F-GGPP and GGSPP, were completely inactive at all concentrations tested. Furthermore, GGSPP antagonized GGPP's effects in vivo and in vitro Chemical chaperones reversed GGPP's effects on Hmg2 structure and degradation, suggesting that GGPP causes selective Hmg2 misfolding. These results indicate that GGPP functions in a manner similar to an allosteric ligand, causing Hmg2 misfolding through interaction with a reversible, specific binding site. Consistent with this, the Hmg2 protein formed multimers, typical of allosteric proteins. We propose that this "allosteric misfolding," or mallostery, observed here for Hmg2 may be a widely used tactic of biological regulation with potential for development of therapeutic small molecules that induce selective misfolding.
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Affiliation(s)
- Margaret A Wangeline
- From the Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093
| | - Randolph Y Hampton
- From the Division of Biological Sciences, the Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093
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15
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Carroll RG, Zasłona Z, Galván-Peña S, Koppe EL, Sévin DC, Angiari S, Triantafilou M, Triantafilou K, Modis LK, O'Neill LA. An unexpected link between fatty acid synthase and cholesterol synthesis in proinflammatory macrophage activation. J Biol Chem 2018; 293:5509-5521. [PMID: 29463677 PMCID: PMC5900750 DOI: 10.1074/jbc.ra118.001921] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 02/08/2018] [Indexed: 11/11/2022] Open
Abstract
Different immune activation states require distinct metabolic features and activities in immune cells. For instance, inhibition of fatty acid synthase (FASN), which catalyzes the synthesis of long-chain fatty acids, prevents the proinflammatory response in macrophages; however, the precise role of this enzyme in this response remains poorly defined. Consistent with previous studies, we found here that FASN is essential for lipopolysaccharide-induced, Toll-like receptor (TLR)-mediated macrophage activation. Interestingly, only agents that block FASN upstream of acetoacetyl-CoA synthesis, including the well-characterized FASN inhibitor C75, inhibited TLR4 signaling, while those acting downstream had no effect. We found that acetoacetyl-CoA could overcome C75's inhibitory effect, whereas other FASN metabolites, including palmitate, did not prevent C75-mediated inhibition. This suggested an unexpected role for acetoacetyl-CoA in inflammation that is independent of its role in palmitate synthesis. Our evidence further suggested that acetoacetyl-CoA arising from FASN activity promotes cholesterol production, indicating a surprising link between fatty acid synthesis and cholesterol synthesis. We further demonstrate that this process is required for TLR4 to enter lipid rafts and facilitate TLR4 signaling. In conclusion, we have uncovered an unexpected link between FASN and cholesterol synthesis that appears to be required for TLR signal transduction and proinflammatory macrophage activation.
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Affiliation(s)
- Richard G Carroll
- From the School of Biochemistry and Immunology, Trinity Biomedical Science Institute, Trinity College, Dublin 2, Ireland.,the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Zbigniew Zasłona
- From the School of Biochemistry and Immunology, Trinity Biomedical Science Institute, Trinity College, Dublin 2, Ireland
| | - Silvia Galván-Peña
- From the School of Biochemistry and Immunology, Trinity Biomedical Science Institute, Trinity College, Dublin 2, Ireland.,the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Emma L Koppe
- the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Daniel C Sévin
- Cellzome, GlaxoSmithKline, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Stefano Angiari
- From the School of Biochemistry and Immunology, Trinity Biomedical Science Institute, Trinity College, Dublin 2, Ireland
| | - Martha Triantafilou
- the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom.,the Institute of Infection and Immunity, School of Medicine, University Hospital of Wales, Cardiff University, Cardiff CF14 4XW, Wales, United Kingdom, and
| | - Kathy Triantafilou
- the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom.,the Institute of Infection and Immunity, School of Medicine, University Hospital of Wales, Cardiff University, Cardiff CF14 4XW, Wales, United Kingdom, and
| | - Louise K Modis
- the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Luke A O'Neill
- From the School of Biochemistry and Immunology, Trinity Biomedical Science Institute, Trinity College, Dublin 2, Ireland, .,the Immunology Catalyst, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
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16
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Chua NK, Howe V, Jatana N, Thukral L, Brown AJ. A conserved degron containing an amphipathic helix regulates the cholesterol-mediated turnover of human squalene monooxygenase, a rate-limiting enzyme in cholesterol synthesis. J Biol Chem 2017; 292:19959-19973. [PMID: 28972164 DOI: 10.1074/jbc.m117.794230] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 09/13/2017] [Indexed: 12/22/2022] Open
Abstract
Cholesterol biosynthesis in the endoplasmic reticulum (ER) is tightly controlled by multiple mechanisms to regulate cellular cholesterol levels. Squalene monooxygenase (SM) is the second rate-limiting enzyme in cholesterol biosynthesis and is regulated both transcriptionally and post-translationally. SM undergoes cholesterol-dependent proteasomal degradation when cholesterol is in excess. The first 100 amino acids of SM (designated SM N100) are necessary for this degradative process and represent the shortest cholesterol-regulated degron identified to date. However, the fundamental intrinsic characteristics of this degron remain unknown. In this study, we performed a series of deletions, point mutations, and domain swaps to identify a 12-residue region (residues Gln-62-Leu-73), required for SM cholesterol-mediated turnover. Molecular dynamics and circular dichroism revealed an amphipathic helix within this 12-residue region. Moreover, 70% of the variation in cholesterol regulation was dependent on the hydrophobicity of this region. Of note, the earliest known Doa10 yeast degron, Deg1, also contains an amphipathic helix and exhibits 42% amino acid similarity with SM N100. Mutating SM residues Phe-35/Ser-37/Leu-65/Ile-69 into alanine, based on the key residues in Deg1, blunted SM cholesterol-mediated turnover. Taken together, our results support a model whereby the amphipathic helix in SM N100 attaches reversibly to the ER membrane depending on cholesterol levels; with excess, the helix is ejected and unravels, exposing a hydrophobic patch, which then serves as a degradation signal. Our findings shed new light on the regulation of a key cholesterol synthesis enzyme, highlighting the conservation of critical degron features from yeast to humans.
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Affiliation(s)
- Ngee Kiat Chua
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Vicky Howe
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Nidhi Jatana
- Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology, Mathura Road, Sukhdev Vihar, New Delhi 110 020, India
| | - Lipi Thukral
- Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology, Mathura Road, Sukhdev Vihar, New Delhi 110 020, India
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia.
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17
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Abstract
The σ2 receptor is an enigmatic protein that has attracted significant attention because of its involvement in diseases as diverse as cancer and neurological disorders. Unlike virtually all other receptors of medical interest, it has eluded molecular cloning since its discovery, and the gene that codes for the receptor remains unknown, precluding the use of modern biological methods to study its function. Using a chemical biology approach, we purified the σ2 receptor from tissue, revealing its identity as TMEM97, an endoplasmic reticulum-resident transmembrane protein that regulates the sterol transporter NPC1. We show that TMEM97 possesses the full suite of molecular properties that define the σ2 receptor, and we identify Asp29 and Asp56 as essential for ligand recognition. Cloning the σ2 receptor resolves a longstanding mystery and will enable therapeutic targeting of this potential drug target.
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Affiliation(s)
- Assaf Alon
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Hayden R Schmidt
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Michael D Wood
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712
| | - James J Sahn
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712
| | - Stephen F Martin
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712
| | - Andrew C Kruse
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115;
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18
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Chernov KG, Neuvonen M, Brock I, Ikonen E, Verkhusha VV. Introducing inducible fluorescent split cholesterol oxidase to mammalian cells. J Biol Chem 2017; 292:8811-8822. [PMID: 28391244 DOI: 10.1074/jbc.m116.761718] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 04/05/2017] [Indexed: 11/06/2022] Open
Abstract
Cholesterol oxidase (COase) is a bacterial enzyme catalyzing the first step in the biodegradation of cholesterol. COase is an important biotechnological tool for clinical diagnostics and production of steroid drugs and insecticides. It is also used for tracking intracellular cholesterol; however, its utility is limited by the lack of an efficient temporal control of its activity. To overcome this we have developed a regulatable fragment complementation system for COase cloned from Chromobacterium sp. The enzyme was split into two moieties that were fused to FKBP (FK506-binding protein) and FRB (rapamycin-binding domain) pair and split GFP fragments. The addition of rapamycin reconstituted a fluorescent enzyme, termed split GFP-COase, the fluorescence level of which correlated with its oxidation activity. A rapid decrease of cellular cholesterol induced by intracellular expression of the split GFP-COase promoted the dissociation of a cholesterol biosensor D4H from the plasma membrane. The process was reversible as upon rapamycin removal, the split GFP-COase fluorescence was lost, and cellular cholesterol levels returned to normal. These data demonstrate that the split GFP-COase provides a novel tool to manipulate cholesterol in mammalian cells.
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Affiliation(s)
| | - Maarit Neuvonen
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland.,Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland, and
| | - Ivonne Brock
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland.,Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland, and
| | - Elina Ikonen
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland, .,Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland, and
| | - Vladislav V Verkhusha
- From the Department of Biochemistry and Developmental Biology and .,Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
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19
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Gao Y, Zhou Y, Goldstein JL, Brown MS, Radhakrishnan A. Cholesterol-induced conformational changes in the sterol-sensing domain of the Scap protein suggest feedback mechanism to control cholesterol synthesis. J Biol Chem 2017; 292:8729-8737. [PMID: 28377508 DOI: 10.1074/jbc.m117.783894] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/03/2017] [Indexed: 01/28/2023] Open
Abstract
Scap is a polytopic protein of endoplasmic reticulum (ER) membranes that transports sterol regulatory element-binding proteins to the Golgi complex for proteolytic activation. Cholesterol accumulation in ER membranes prevents Scap transport and decreases cholesterol synthesis. Previously, we provided evidence that cholesterol inhibition is initiated when cholesterol binds to loop 1 of Scap, which projects into the ER lumen. Within cells, this binding causes loop 1 to dissociate from loop 7, another luminal Scap loop. However, we have been unable to demonstrate this dissociation when we added cholesterol to isolated complexes of loops 1 and 7. We therefore speculated that the dissociation requires a conformational change in the intervening polytopic sequence separating loops 1 and 7. Here we demonstrate such a change using a protease protection assay in sealed membrane vesicles. In the absence of cholesterol, trypsin or proteinase K cleaved cytosolic loop 4, generating a protected fragment that we visualized with a monoclonal antibody against loop 1. When cholesterol was added to these membranes, cleavage in loop 4 was abolished. Because loop 4 is part of the so-called sterol-sensing domain separating loops 1 and 7, these results support the hypothesis that cholesterol binding to loop 1 alters the conformation of the sterol-sensing domain. They also suggest that this conformational change helps transmit the cholesterol signal from loop 1 to loop 7, thereby allowing separation of the loops and facilitating the feedback inhibition of cholesterol synthesis. These insights suggest a new structural model for cholesterol-mediated regulation of Scap activity.
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Affiliation(s)
- Yansong Gao
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Yulian Zhou
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Joseph L Goldstein
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Michael S Brown
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Arun Radhakrishnan
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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20
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Mast N, Anderson KW, Lin JB, Li Y, Turko IV, Tatsuoka C, Bjorkhem I, Pikuleva IA. Cytochrome P450 27A1 Deficiency and Regional Differences in Brain Sterol Metabolism Cause Preferential Cholestanol Accumulation in the Cerebellum. J Biol Chem 2017; 292:4913-4924. [PMID: 28190002 DOI: 10.1074/jbc.m116.774760] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/10/2017] [Indexed: 01/04/2023] Open
Abstract
Cytochrome P450 27A1 (CYP27A1 or sterol 27-hydroxylase) is a ubiquitous, multifunctional enzyme catalyzing regio- and stereospecific hydroxylation of different sterols. In humans, complete CYP27A1 deficiency leads to cerebrotendinous xanthomatosis or nodule formation in tendons and brain (preferentially in the cerebellum) rich in cholesterol and cholestanol, the 5α-saturated analog of cholesterol. In Cyp27a1-/- mice, xanthomas are not formed, despite a significant cholestanol increase in the brain and cerebellum. The mechanism behind cholestanol production has been clarified, yet little is known about its metabolism, except that CYP27A1 might metabolize cholestanol. It also is unclear why CYP27A1 deficiency results in preferential cholestanol accumulation in the cerebellum. We hypothesized that cholestanol might be metabolized by CYP46A1, the principal cholesterol 24-hydroxylase in the brain. We quantified sterols along with CYP27A1 and CYP46A1 in mouse models (Cyp27a1-/-, Cyp46a1-/-, Cyp27a1-/-Cyp46a1-/-, and two wild type strains) and human brain specimens. In vitro experiments with purified P450s were conducted as well. We demonstrate that CYP46A1 is involved in cholestanol removal from the brain and that several factors contribute to the preferential increase in cholestanol in the cerebellum arising from CYP27A1 deficiency. These factors include (i) low cerebellar abundance of CYP46A1 and high cerebellar abundance of CYP27A1, the lack of which probably selectively increases the cerebellar cholestanol production; (ii) spatial separation in the cerebellum of cholesterol/cholestanol-metabolizing P450s from a pool of metabolically available cholestanol; and (iii) weak cerebellar regulation of cholesterol biosynthesis. We identified a new physiological role of CYP46A1, an important brain enzyme and cytochrome P450 that could be activated pharmacologically.
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Affiliation(s)
- Natalia Mast
- From the Departments of Ophthalmology and Visual Sciences and
| | - Kyle W Anderson
- the Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.,the Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, and
| | - Joseph B Lin
- From the Departments of Ophthalmology and Visual Sciences and
| | - Yong Li
- From the Departments of Ophthalmology and Visual Sciences and
| | - Illarion V Turko
- the Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.,the Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, and
| | - Curtis Tatsuoka
- Neurology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Ingemar Bjorkhem
- the Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institute, 141 86 Huddinge, Sweden
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21
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Munkacsi AB, Hammond N, Schneider RT, Senanayake DS, Higaki K, Lagutin K, Bloor SJ, Ory DS, Maue RA, Chen FW, Hernandez-Ono A, Dahlson N, Repa JJ, Ginsberg HN, Ioannou YA, Sturley SL. Normalization of Hepatic Homeostasis in the Npc1nmf164 Mouse Model of Niemann-Pick Type C Disease Treated with the Histone Deacetylase Inhibitor Vorinostat. J Biol Chem 2016; 292:4395-4410. [PMID: 28031458 DOI: 10.1074/jbc.m116.770578] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 12/21/2016] [Indexed: 12/31/2022] Open
Abstract
Niemann-Pick type C (NP-C) disease is a fatal genetic lipidosis for which there is no Food and Drug Administration (FDA)-approved therapy. Vorinostat, an FDA-approved inhibitor of histone deacetylases, ameliorates lysosomal lipid accumulation in cultured NP-C patient fibroblasts. To assess the therapeutic potential of histone deacetylase inhibition, we pursued these in vitro observations in two murine models of NP-C disease. Npc1nmf164 mice, which express a missense mutation in the Npc1 gene, were treated intraperitoneally, from weaning, with the maximum tolerated dose of vorinostat (150 mg/kg, 5 days/week). Disease progression was measured via gene expression, liver function and pathology, serum and tissue lipid levels, body weight, and life span. Transcriptome analyses of treated livers indicated multiple changes consistent with reversal of liver dysfunction that typifies NP-C disease. Significant improvements in liver pathology and function were achieved by this treatment regimen; however, NPC1 protein maturation and levels, disease progression, weight loss, and animal morbidity were not detectably altered. Vorinostat concentrations were >200 μm in the plasma compartment of treated animals but were almost 100-fold lower in brain tissue. Apolipoprotein B metabolism and the expression of key components of lipid homeostasis in primary hepatocytes from null (Npc1-/-) and missense (Npc1nmf164 ) mutant mice were altered by vorinostat treatment, consistent with a response by these cells independent of the status of the Npc1 locus. These results suggest that HDAC inhibitors have utility to treat visceral NP-C disease. However, it is clear that improved blood-brain barrier penetration will be required to alleviate the neurological symptoms of human NP-C disease.
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Affiliation(s)
- Andrew B Munkacsi
- From the School of Biological Sciences and .,Centre for Biodiscovery, Victoria University of Wellington, Wellington 6012, New Zealand
| | | | | | | | - Katsumi Higaki
- the Division of Functional Genomics, Research Center for Bioscience and Technology, Tottori University, Yonago 683-8503, Japan
| | | | | | - Daniel S Ory
- the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Robert A Maue
- the Department of Physiology and Neurobiology and the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | - Fannie W Chen
- the Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York 10029
| | | | - Nicole Dahlson
- the Departments of Physiology and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - Joyce J Repa
- the Departments of Physiology and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | | | - Yiannis A Ioannou
- the Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York 10029
| | - Stephen L Sturley
- the Department of Genetics and Development, Columbia University Medical Center, New York, New York 10032
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22
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Yin QH, Zhang R, Li L, Wang YT, Liu JP, Zhang J, Bai L, Cheng JQ, Fu P, Liu F. Exendin-4 Ameliorates Lipotoxicity-induced Glomerular Endothelial Cell Injury by Improving ABC Transporter A1-mediated Cholesterol Efflux in Diabetic apoE Knockout Mice. J Biol Chem 2016; 291:26487-26501. [PMID: 27784780 DOI: 10.1074/jbc.m116.730564] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 10/22/2016] [Indexed: 02/05/2023] Open
Abstract
ATP-binding cassette transporter A1 (ABCA1), which promotes cholesterol efflux from cells and inhibits inflammatory responses, is highly expressed in the kidney. Research has shown that exendin-4, a glucagon-like peptide-1 receptor (GLP-1R) agonist, promotes ABCA1 expression in multiple tissues and organs; however, the mechanisms underlying exendin-4 induction of ABCA1 expression in glomerular endothelial cells are not fully understood. In this study we investigated the effect of exendin-4 on ABCA1 in glomerular endothelial cells of diabetic kidney disease (DKD) and the possible mechanism. We observed a marked increase in glomerular lipid deposits in tissues of patients with DKD and diabetic apolipoprotein E knock-out (apoE-/-) mice by Oil Red O staining and biochemical analysis of cholesterol. We found significantly decreased ABCA1 expression in glomerular endothelial cells of diabetic apoE-/- mice and increased renal lipid, cholesterol, and inflammatory cytokine levels. Exendin-4 decreased renal cholesterol accumulation and inflammation and increased cholesterol efflux by up-regulating ABCA1. In human glomerular endothelial cells, GLP-1R-mediated signaling pathways (e.g. Ca2+/calmodulin-dependent protein kinase, cAMP/PKA, PI3K/AKT, and ERK1/2) were involved in cholesterol efflux and inflammatory responses by regulating ABCA1 expression. We propose that exendin-4 increases ABCA1 expression in glomerular endothelial cells, which plays an important role in alleviating renal lipid accumulation, inflammation, and proteinuria in mice with type 2 diabetes.
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Affiliation(s)
- Qing-Hua Yin
- From the Division of Nephrology, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China and
| | - Rui Zhang
- From the Division of Nephrology, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China and
| | - Li Li
- From the Division of Nephrology, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China and
| | - Yi-Ting Wang
- From the Division of Nephrology, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China and
| | - Jing-Ping Liu
- the Key Laboratory of Transplant Engineering and Immunology, Ministry of Health, Regenerative Medicine Research Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China
| | - Jie Zhang
- the Key Laboratory of Transplant Engineering and Immunology, Ministry of Health, Regenerative Medicine Research Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China
| | - Lin Bai
- the Key Laboratory of Transplant Engineering and Immunology, Ministry of Health, Regenerative Medicine Research Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China
| | - Jing-Qiu Cheng
- the Key Laboratory of Transplant Engineering and Immunology, Ministry of Health, Regenerative Medicine Research Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China
| | - Ping Fu
- From the Division of Nephrology, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China and
| | - Fang Liu
- From the Division of Nephrology, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China and
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23
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Park SH, Kim J, Yu M, Park JH, Kim YS, Moon Y. Epithelial Cholesterol Deficiency Attenuates Human Antigen R-linked Pro-inflammatory Stimulation via an SREBP2-linked Circuit. J Biol Chem 2016; 291:24641-24656. [PMID: 27703009 DOI: 10.1074/jbc.m116.723973] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 09/16/2016] [Indexed: 01/03/2023] Open
Abstract
Patients with chronic intestinal ulcerative diseases, such as inflammatory bowel disease, tend to exhibit abnormal lipid profiles, which may affect the gut epithelial integrity. We hypothesized that epithelial cholesterol depletion may trigger inflammation-checking machinery via cholesterol sentinel signaling molecules whose disruption in patients may aggravate inflammation and disease progression. In the present study, sterol regulatory element-binding protein 2 (SREBP2) as the cholesterol sentinel was assessed for its involvement in the epithelial inflammatory responses in cholesterol-depleted enterocytes. Patients and experimental animals with intestinal ulcerative injuries showed suppression in epithelial SREBP2. Moreover, SREBP2-deficient enterocytes showed enhanced pro-inflammatory signals in response to inflammatory insults, indicating regulatory roles of SREBP2 in gut epithelial inflammation. However, epithelial cholesterol depletion transiently induced pro-inflammatory chemokine expression regardless of the well known pro-inflammatory nuclear factor-κB signals. In contrast, cholesterol depletion also exerts regulatory actions to maintain epithelial homeostasis against excessive inflammation via SREBP2-associated signals in a negative feedback loop. Mechanistically, SREBP2 and its induced target EGR-1 were positively involved in induction of peroxisome proliferator-activated receptor γ (PPARγ), a representative anti-inflammatory transcription factor. As a crucial target of the SREBP2-EGR-1-PPARγ-associated signaling pathways, the mRNA stabilizer, human antigen R (HuR) was retained in nuclei, leading to reduced stability of pro-inflammatory chemokine transcripts. This mechanistic investigation provides clinical insights into protective roles of the epithelial cholesterol deficiency against excessive inflammatory responses via the SREBP2-HuR circuit, although the deficiency triggers transient pro-inflammatory signals.
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Affiliation(s)
- Seong-Hwan Park
- From the Laboratory of Mucosal Exposome and Biomodulation, Department of Biomedical Sciences and Medical Research Institute, Pusan National University School of Medicine, Yangsan 50612
| | - Juil Kim
- From the Laboratory of Mucosal Exposome and Biomodulation, Department of Biomedical Sciences and Medical Research Institute, Pusan National University School of Medicine, Yangsan 50612
| | - Mira Yu
- From the Laboratory of Mucosal Exposome and Biomodulation, Department of Biomedical Sciences and Medical Research Institute, Pusan National University School of Medicine, Yangsan 50612
| | - Jae-Hong Park
- the Department of Pediatrics, Pusan National University, Yangsan 50612
| | - Yong Sik Kim
- the Department of Pharmacology, College of Medicine, Seoul National University, Seoul 03080, and
| | - Yuseok Moon
- From the Laboratory of Mucosal Exposome and Biomodulation, Department of Biomedical Sciences and Medical Research Institute, Pusan National University School of Medicine, Yangsan 50612,; the Immunoregulatory Therapeutics Group in Brain Busan 21 Project, Busan 46241, Korea.
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24
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Weider E, Susan-Resiga D, Essalmani R, Hamelin J, Asselin MC, Nimesh S, Ashraf Y, Wycoff KL, Zhang J, Prat A, Seidah NG. Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Single Domain Antibodies Are Potent Inhibitors of Low Density Lipoprotein Receptor Degradation. J Biol Chem 2016; 291:16659-71. [PMID: 27284008 DOI: 10.1074/jbc.m116.717736] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 01/14/2023] Open
Abstract
Single domain antibodies (sdAbs) correspond to the antigen-binding domains of camelid antibodies. They have the same antigen-binding properties and specificity as monoclonal antibodies (mAbs) but are easier and cheaper to produce. We report here the development of sdAbs targeting human PCSK9 (proprotein convertase subtilisin/kexin type 9) as an alternative to anti-PCSK9 mAbs. After immunizing a llama with human PCSK9, we selected four sdAbs that bind PCSK9 with a high affinity and produced them as fusion proteins with a mouse Fc. All four sdAb-Fcs recognize the C-terminal Cys-His-rich domain of PCSK9. We performed multiple cellular assays and demonstrated that the selected sdAbs efficiently blocked PCSK9-mediated low density lipoprotein receptor (LDLR) degradation in cell lines, in human hepatocytes, and in mouse primary hepatocytes. We further showed that the sdAb-Fcs do not affect binding of PCSK9 to the LDLR but rather block its induced cellular LDLR degradation. Pcsk9 knock-out mice expressing a human bacterial artificial chromosome (BAC) transgene were generated, resulting in plasma levels of ∼300 ng/ml human PCSK9. Mice were singly or doubly injected with the best sdAb-Fc and analyzed at day 4 or 11, respectively. After 4 days, mice exhibited a 32 and 44% decrease in the levels of total cholesterol and apolipoprotein B and ∼1.8-fold higher liver LDLR protein levels. At 11 days, the equivalent values were 24 and 46% and ∼2.3-fold higher LDLR proteins. These data constitute a proof-of-principle for the future usage of sdAbs as PCSK9-targeting drugs that can efficiently reduce LDL-cholesterol, and as tools to study the Cys-His-rich domain-dependent sorting the PCSK9-LDLR complex to lysosomes.
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Affiliation(s)
- Elodie Weider
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Delia Susan-Resiga
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Rachid Essalmani
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Josée Hamelin
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Marie-Claude Asselin
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Surendra Nimesh
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Yahya Ashraf
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Keith L Wycoff
- Planet Biotechnology Inc., Hayward, California 94545-2740, and
| | - Jianbing Zhang
- the Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Annik Prat
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada
| | - Nabil G Seidah
- From the Laboratory of Biochemical Neuroendocrinology, Institut de Recherches Cliniques de Montréal, University of Montreal, Montreal, Quebec H2W 1R7, Canada,
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25
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Lei D, Rames M, Zhang X, Zhang L, Zhang S, Ren G. Insights into the Tunnel Mechanism of Cholesteryl Ester Transfer Protein through All-atom Molecular Dynamics Simulations. J Biol Chem 2016; 291:14034-14044. [PMID: 27143480 PMCID: PMC4933163 DOI: 10.1074/jbc.m116.715565] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Indexed: 12/31/2022] Open
Abstract
Cholesteryl ester transfer protein (CETP) mediates cholesteryl ester (CE) transfer from the atheroprotective high density lipoprotein (HDL) cholesterol to the atherogenic low density lipoprotein cholesterol. In the past decade, this property has driven the development of CETP inhibitors, which have been evaluated in large scale clinical trials for treating cardiovascular diseases. Despite the pharmacological interest, little is known about the fundamental mechanism of CETP in CE transfer. Recent electron microscopy (EM) experiments have suggested a tunnel mechanism, and molecular dynamics simulations have shown that the flexible N-terminal distal end of CETP penetrates into the HDL surface and takes up a CE molecule through an open pore. However, it is not known whether a CE molecule can completely transfer through an entire CETP molecule. Here, we used all-atom molecular dynamics simulations to evaluate this possibility. The results showed that a hydrophobic tunnel inside CETP is sufficient to allow a CE molecule to completely transfer through the entire CETP within a predicted transfer time and at a rate comparable with those obtained through physiological measurements. Analyses of the detailed interactions revealed several residues that might be critical for CETP function, which may provide important clues for the effective development of CETP inhibitors and treatment of cardiovascular diseases.
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Affiliation(s)
- Dongsheng Lei
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Matthew Rames
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Xing Zhang
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Lei Zhang
- Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Shengli Zhang
- Department of Applied Physics, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
| | - Gang Ren
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
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26
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Zhang Y, Lee KM, Kinch LN, Clark L, Grishin NV, Rosenbaum DM, Brown MS, Goldstein JL, Radhakrishnan A. Direct Demonstration That Loop1 of Scap Binds to Loop7: A CRUCIAL EVENT IN CHOLESTEROL HOMEOSTASIS. J Biol Chem 2016; 291:12888-12896. [PMID: 27068746 DOI: 10.1074/jbc.m116.729798] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Indexed: 11/06/2022] Open
Abstract
Cholesterol homeostasis is mediated by Scap, a polytopic endoplasmic reticulum (ER) protein that transports sterol regulatory element-binding proteins from the ER to Golgi, where they are processed to forms that activate cholesterol synthesis. Scap has eight transmembrane helices and two large luminal loops, designated Loop1 and Loop7. We earlier provided indirect evidence that Loop1 binds to Loop7, allowing Scap to bind COPII proteins for transport in coated vesicles. When ER cholesterol rises, it binds to Loop1. We hypothesized that this causes dissociation from Loop7, abrogating COPII binding. Here we demonstrate direct binding of the two loops when expressed as isolated fragments or as a fusion protein. Expressed alone, Loop1 remained intracellular and membrane-bound. When Loop7 was co-expressed, it bound to Loop1, and the soluble complex was secreted. A Loop1-Loop7 fusion protein was also secreted, and the two loops remained bound when the linker between them was cleaved by a protease. Point mutations that disrupt the Loop1-Loop7 interaction prevented secretion of the Loop1-Loop7 fusion protein. These data provide direct documentation of intramolecular Loop1-Loop7 binding, a central event in cholesterol homeostasis.
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Affiliation(s)
| | | | - Lisa N Kinch
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | | | - Nick V Grishin
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390; Biophysics, and; Biochemistry and
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27
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Shrestha E, Hussein MA, Savas JN, Ouimet M, Barrett TJ, Leone S, Yates JR, Moore KJ, Fisher EA, Garabedian MJ. Poly(ADP-ribose) Polymerase 1 Represses Liver X Receptor-mediated ABCA1 Expression and Cholesterol Efflux in Macrophages. J Biol Chem 2016; 291:11172-84. [PMID: 27026705 DOI: 10.1074/jbc.m116.726729] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Indexed: 11/06/2022] Open
Abstract
Liver X receptors (LXR) are oxysterol-activated nuclear receptors that play a central role in reverse cholesterol transport through up-regulation of ATP-binding cassette transporters (ABCA1 and ABCG1) that mediate cellular cholesterol efflux. Mouse models of atherosclerosis exhibit reduced atherosclerosis and enhanced regression of established plaques upon LXR activation. However, the coregulatory factors that affect LXR-dependent gene activation in macrophages remain to be elucidated. To identify novel regulators of LXR that modulate its activity, we used affinity purification and mass spectrometry to analyze nuclear LXRα complexes and identified poly(ADP-ribose) polymerase-1 (PARP-1) as an LXR-associated factor. In fact, PARP-1 interacted with both LXRα and LXRβ. Both depletion of PARP-1 and inhibition of PARP-1 activity augmented LXR ligand-induced ABCA1 expression in the RAW 264.7 macrophage line and primary bone marrow-derived macrophages but did not affect LXR-dependent expression of other target genes, ABCG1 and SREBP-1c. Chromatin immunoprecipitation experiments confirmed PARP-1 recruitment at the LXR response element in the promoter of the ABCA1 gene. Further, we demonstrated that LXR is poly(ADP-ribosyl)ated by PARP-1, a potential mechanism by which PARP-1 influences LXR function. Importantly, the PARP inhibitor 3-aminobenzamide enhanced macrophage ABCA1-mediated cholesterol efflux to the lipid-poor apolipoprotein AI. These findings shed light on the important role of PARP-1 on LXR-regulated lipid homeostasis. Understanding the interplay between PARP-1 and LXR may provide insights into developing novel therapeutics for treating atherosclerosis.
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Affiliation(s)
- Elina Shrestha
- From the Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - Maryem A Hussein
- From the Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - Jeffery N Savas
- the Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois 60611
| | - Mireille Ouimet
- the Department of Medicine, Division of Cardiology, Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York 10016, and
| | - Tessa J Barrett
- the Department of Medicine, Division of Cardiology, Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York 10016, and
| | - Sarah Leone
- From the Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - John R Yates
- the Department of Chemical Physiology, Scripps Research Institute, La Jolla, California 92037
| | - Kathryn J Moore
- the Department of Medicine, Division of Cardiology, Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York 10016, and
| | - Edward A Fisher
- the Department of Medicine, Division of Cardiology, Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York 10016, and
| | - Michael J Garabedian
- From the Department of Microbiology, New York University School of Medicine, New York, New York 10016,
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28
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Prabhu AV, Luu W, Sharpe LJ, Brown AJ. Cholesterol-mediated Degradation of 7-Dehydrocholesterol Reductase Switches the Balance from Cholesterol to Vitamin D Synthesis. J Biol Chem 2016; 291:8363-73. [PMID: 26887953 DOI: 10.1074/jbc.m115.699546] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Indexed: 01/08/2023] Open
Abstract
Cholesterol is detrimental to human health in excess but is also essential for normal embryogenesis. Hence, enzymes involved in its synthesis possess many layers of regulation to achieve balanced cholesterol levels. 7-Dehydrocholesterol reductase (DHCR7) is the terminal enzyme of cholesterol synthesis in the Kandutsch-Russell pathway, converting 7-dehydrocholesterol (7DHC) to cholesterol. In the absence of functional DHCR7, accumulation of 7DHC and a lack of cholesterol production leads to the devastating developmental disorder, Smith-Lemli-Opitz syndrome. This study identifies that statin treatment can ameliorate the low DHCR7 expression seen with common Smith-Lemli-Opitz syndrome mutations. Furthermore, we show that wild-type DHCR7 is also relatively labile. In an example of end-product inhibition, cholesterol accelerates the proteasomal degradation of DHCR7, resulting in decreased protein levels and activity. The loss of enzymatic activity results in the accumulation of the substrate 7DHC, which leads to an increased production of vitamin D. Thus, these findings highlight DHCR7 as an important regulatory switch between cholesterol and vitamin D synthesis.
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Affiliation(s)
- Anika V Prabhu
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Winnie Luu
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Laura J Sharpe
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrew J Brown
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
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29
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El Asmar Z, Terrand J, Jenty M, Host L, Mlih M, Zerr A, Justiniano H, Matz RL, Boudier C, Scholler E, Garnier JM, Bertaccini D, Thiersé D, Schaeffer C, Van Dorsselaer A, Herz J, Bruban V, Boucher P. Convergent Signaling Pathways Controlled by LRP1 (Receptor-related Protein 1) Cytoplasmic and Extracellular Domains Limit Cellular Cholesterol Accumulation. J Biol Chem 2016; 291:5116-27. [PMID: 26792864 DOI: 10.1074/jbc.m116.714485] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Indexed: 11/06/2022] Open
Abstract
The low density lipoprotein receptor-related protein 1 (LRP1) is a ubiquitously expressed cell surface receptor that protects from intracellular cholesterol accumulation. However, the underlying mechanisms are unknown. Here we show that the extracellular (α) chain of LRP1 mediates TGFβ-induced enhancement of Wnt5a, which limits intracellular cholesterol accumulation by inhibiting cholesterol biosynthesis and by promoting cholesterol export. Moreover, we demonstrate that the cytoplasmic (β) chain of LRP1 suffices to limit cholesterol accumulation in LRP1(-/-) cells. Through binding of Erk2 to the second of its carboxyl-terminal NPXY motifs, LRP1 β-chain positively regulates the expression of ATP binding cassette transporter A1 (ABCA1) and of neutral cholesterol ester hydrolase (NCEH1). These results highlight the unexpected functions of LRP1 and the canonical Wnt5a pathway and new therapeutic potential in cholesterol-associated disorders including cardiovascular diseases.
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Affiliation(s)
- Zeina El Asmar
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Jérome Terrand
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Marion Jenty
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Lionel Host
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Mohamed Mlih
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Aurélie Zerr
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Hélène Justiniano
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Rachel L Matz
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Christian Boudier
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Estelle Scholler
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France
| | - Jean-Marie Garnier
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), INSERM 964/CNRS UMR 7104, University of Strasbourg, 67401 Illkirch, France
| | - Diego Bertaccini
- CNRS, UMR 7178, University of Strasbourg, 67087 Strasbourg, France, and
| | - Danièle Thiersé
- CNRS, UMR 7178, University of Strasbourg, 67087 Strasbourg, France, and
| | | | | | - Joachim Herz
- Department of Molecular Genetics and Center for Translational Neurodegeneration Research, UT Southwestern Medical Center, Dallas, Texas 75390
| | - Véronique Bruban
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France,
| | - Philippe Boucher
- From the CNRS, UMR 7213, University of Strasbourg, 67401 Illkirch, France,
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30
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Ernst WL, Shome K, Wu CC, Gong X, Frizzell RA, Aridor M. VAMP-associated Proteins (VAP) as Receptors That Couple Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Proteostasis with Lipid Homeostasis. J Biol Chem 2016; 291:5206-20. [PMID: 26740627 DOI: 10.1074/jbc.m115.692749] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Indexed: 12/27/2022] Open
Abstract
Unesterified cholesterol accumulates in late endosomes in cells expressing the misfolded cystic fibrosis transmembrane conductance regulator (CFTR). CFTR misfolding in the endoplasmic reticulum (ER) or general activation of ER stress led to dynein-mediated clustering of cholesterol-loaded late endosomes at the Golgi region, a process regulated by ER-localized VAMP-associated proteins (VAPs). We hypothesized that VAPs serve as intracellular receptors that couple lipid homeostasis through interactions with two phenylalanines in an acidic track (FFAT) binding signals (found in lipid sorting and sensing proteins, LSS) with proteostasis regulation. VAPB inhibited the degradation of ΔF508-CFTR. The activity was mapped to the ligand-binding major sperm protein (MSP) domain, which was sufficient in regulating CFTR biogenesis. We identified mutations in an unstructured loop within the MSP that uncoupled VAPB-regulated CFTR biogenesis from basic interactions with FFAT. Using this information, we defined functional and physical interactions between VAPB and proteostasis regulators (ligands), including the unfolded protein response sensor ATF6 and the ER degradation cluster that included FAF1, VCP, BAP31, and Derlin-1. VAPB inhibited the degradation of ΔF508-CFTR in the ER through interactions with the RMA1-Derlin-BAP31-VCP pathway. Analysis of pseudoligands containing tandem FFAT signals supports a competitive model for VAP interactions that direct CFTR biogenesis. The results suggest a model in which VAP-ligand binding couples proteostasis and lipid homeostasis leading to observed phenotypes of lipid abnormalities in protein folding diseases.
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Affiliation(s)
- Wayne L Ernst
- From the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Kuntala Shome
- From the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Christine C Wu
- From the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Xiaoyan Gong
- From the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Raymond A Frizzell
- From the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Meir Aridor
- From the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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31
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Howe V, Chua NK, Stevenson J, Brown AJ. The Regulatory Domain of Squalene Monooxygenase Contains a Re-entrant Loop and Senses Cholesterol via a Conformational Change. J Biol Chem 2015; 290:27533-44. [PMID: 26434806 DOI: 10.1074/jbc.m115.675181] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Indexed: 11/06/2022] Open
Abstract
Squalene monooxygenase (SM) is an important control point in cholesterol synthesis beyond 3-hydroxy-3-methylglutaryl-CoA reductase. Although it is known to associate with the endoplasmic reticulum, its topology has not been determined. We have elucidated the membrane topology of the sterol-responsive domain of SM comprising the first 100 amino acids fused to GFP (SM N100-GFP) by determining the accessibility of 16 introduced cysteines to the cysteine-reactive, membrane-impermeable reagent PEG-maleimide. We have identified a region integrally associated with the endoplasmic reticulum membrane that is likely to interact with cholesterol or respond to cholesterol-induced membrane effects. By comparing cysteine accessibility with and without cholesterol treatment, we further present evidence to suggest that cholesterol induces a conformational change in SM N100-GFP. This change is likely to lead to its targeted degradation by the ubiquitin-proteasome system because degradation is blunted by treatment with the chemical chaperone glycerol, which retains SM N100-GFP in its native conformation. Furthermore, degradation can be disrupted by insertion of two N-terminal myc tags, implicating the N terminus in this process. Together, this information provides new molecular insights into the regulation of this critical control point in cholesterol synthesis.
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Affiliation(s)
- Vicky Howe
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney 2052, Australia and
| | - Ngee Kiat Chua
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney 2052, Australia and
| | - Julian Stevenson
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720
| | - Andrew J Brown
- From the School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney 2052, Australia and
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32
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Lammi C, Zanoni C, Arnoldi A, Vistoli G. Two Peptides from Soy β-Conglycinin Induce a Hypocholesterolemic Effect in HepG2 Cells by a Statin-Like Mechanism: Comparative in Vitro and in Silico Modeling Studies. J Agric Food Chem 2015; 63:7945-7951. [PMID: 26310992 DOI: 10.1021/acs.jafc.5b03497] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Two peptides from soybean β-conglycinin, i.e., YVVNPDNDEN (peptide 2) and YVVNPDNNEN (peptide 3), are known to be absorbed by human enterocytes. The former is a fragment of LRVPAGTTFYVVNPDNDENLRMIA (peptide 1), previously shown to increase the low-density lipoprotein (LDL) uptake and degradation in hepatocytes. Research carried out in silico on their interactions with the catalytic site of 3-hydroxy-3-methylglutaryl CoA reductase (HMGCoAR) demonstrated that they behave as competitive inhibitors of HMGCoAR activity with a statin-like mechanism, confirmed by direct inhibition experiments. Research in HepG2 cells aimed at investigating the effects of these peptides on cholesterol metabolism showed that compared to mock treatment peptide 2 at 350 μM up-regulates the mature SREBP2 protein level by 134.0 ± 10.5%, increases the LDLR protein level by 152.0 ± 20.0%, and enhances the HMGCoAR protein production by 171 ± 29.9%, whereas peptide 3 up-regulates the mature SREBP2 protein level by 158.0 ± 9.2%, increases the LDL level 164.0 ± 17.9%, and induces a HMGCoAR protein increase by 170 ± 50.0%.
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Affiliation(s)
- Carmen Lammi
- Department of Pharmaceutical Sciences, University of Milan , via Mangiagalli 25, Milan 20133, Italy
| | - Chiara Zanoni
- Cardio-toraco-vascular Department, Niguarda Hospital , Milan 20162, Italy
| | - Anna Arnoldi
- Department of Pharmaceutical Sciences, University of Milan , via Mangiagalli 25, Milan 20133, Italy
| | - Giulio Vistoli
- Department of Pharmaceutical Sciences, University of Milan , via Mangiagalli 25, Milan 20133, Italy
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33
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Aleidi SM, Howe V, Sharpe LJ, Yang A, Rao G, Brown AJ, Gelissen IC. The E3 ubiquitin ligases, HUWE1 and NEDD4-1, are involved in the post-translational regulation of the ABCG1 and ABCG4 lipid transporters. J Biol Chem 2015; 290:24604-13. [PMID: 26296893 DOI: 10.1074/jbc.m115.675579] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 11/06/2022] Open
Abstract
The ATP-binding cassette transporter ABCG1 has an essential role in cellular cholesterol homeostasis, and dysregulation has been associated with a number of high burden diseases. Previous studies reported that ABCG1 is ubiquitinated and degraded via the ubiquitin proteasome system. However, so far the molecular mechanism, including the identity of any of the rate-limiting ubiquitination enzymes, or E3 ligases, is unknown. Using liquid chromatography mass spectrometry, we identified two HECT domain E3 ligases associated with ABCG1, named HUWE1 (HECT, UBA, and WWE domain containing 1, E3 ubiquitin protein ligase) and NEDD4-1 (Neural precursor cell-expressed developmentally down regulated gene 4), of which the latter is the founding member of the NEDD4 family of ubiquitin ligases. Silencing both HUWE1 and NEDD4-1 in cells overexpressing human ABCG1 significantly increased levels of the ABCG1 monomeric and dimeric protein forms, however ABCA1 protein expression was unaffected. In addition, ligase silencing increased ABCG1-mediated cholesterol export to HDL in cells overexpressing the transporter as well as in THP-1 macrophages. Reciprocally, overexpression of both ligases resulted in a significant reduction in protein levels of both the ABCG1 monomeric and dimeric forms. Like ABCG1, ABCG4 protein levels and cholesterol export activity were significantly increased after silencing both HUWE1 and NEDD4-1 in cells overexpressing this closely related ABC half-transporter. In summary, we have identified for the first time two E3 ligases that are fundamental enzymes in the post-translational regulation of ABCG1 and ABCG4 protein levels and cellular cholesterol export activity.
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Affiliation(s)
- Shereen M Aleidi
- From the Faculty of Pharmacy, The University of Sydney, Sydney NSW 2006 and
| | - Vicky Howe
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney NSW 2052 Australia
| | - Laura J Sharpe
- From the Faculty of Pharmacy, The University of Sydney, Sydney NSW 2006 and School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney NSW 2052 Australia
| | - Alryel Yang
- From the Faculty of Pharmacy, The University of Sydney, Sydney NSW 2006 and
| | - Geetha Rao
- From the Faculty of Pharmacy, The University of Sydney, Sydney NSW 2006 and
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney NSW 2052 Australia
| | - Ingrid C Gelissen
- From the Faculty of Pharmacy, The University of Sydney, Sydney NSW 2006 and
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34
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Yamauchi Y, Iwamoto N, Rogers MA, Abe-Dohmae S, Fujimoto T, Chang CCY, Ishigami M, Kishimoto T, Kobayashi T, Ueda K, Furukawa K, Chang TY, Yokoyama S. Deficiency in the Lipid Exporter ABCA1 Impairs Retrograde Sterol Movement and Disrupts Sterol Sensing at the Endoplasmic Reticulum. J Biol Chem 2015. [PMID: 26198636 DOI: 10.1074/jbc.m115.662668] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular cholesterol homeostasis involves sterol sensing at the endoplasmic reticulum (ER) and sterol export from the plasma membrane (PM). Sterol sensing at the ER requires efficient sterol delivery from the PM; however, the macromolecules that facilitate retrograde sterol transport at the PM have not been identified. ATP-binding cassette transporter A1 (ABCA1) mediates cholesterol and phospholipid export to apolipoprotein A-I for the assembly of high density lipoprotein (HDL). Mutations in ABCA1 cause Tangier disease, a familial HDL deficiency. Several lines of clinical and experimental evidence suggest a second function of ABCA1 in cellular cholesterol homeostasis in addition to mediating cholesterol efflux. Here, we report the unexpected finding that ABCA1 also plays a key role in facilitating retrograde sterol transport from the PM to the ER for sterol sensing. Deficiency in ABCA1 delays sterol esterification at the ER and activates the SREBP-2 cleavage pathway. The intrinsic ATPase activity in ABCA1 is required to facilitate retrograde sterol transport. ABCA1 deficiency causes alternation of PM composition and hampers a clathrin-independent endocytic activity that is required for ER sterol sensing. Our finding identifies ABCA1 as a key macromolecule facilitating bidirectional sterol movement at the PM and shows that ABCA1 controls retrograde sterol transport by modulating a certain clathrin-independent endocytic process.
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Affiliation(s)
- Yoshio Yamauchi
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan,
| | - Noriyuki Iwamoto
- the Department of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Maximillian A Rogers
- the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | - Sumiko Abe-Dohmae
- the Department of Biochemistry, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Toyoshi Fujimoto
- the Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Catherine C Y Chang
- the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
| | - Masato Ishigami
- the Institute for Integrated Cell-Material Sciences and Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Takuma Kishimoto
- the Lipid Biology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan, and
| | | | - Kazumitsu Ueda
- the Institute for Integrated Cell-Material Sciences and Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Koichi Furukawa
- From the Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Ta-Yuan Chang
- the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755,
| | - Shinji Yokoyama
- the Nutritional Health Science Research Center and Department of Food and Nutritional Sciences, Chubu University, Kasugai 487-8501, Japan
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35
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Hager L, Li L, Pun H, Liu L, Hossain MA, Maguire GF, Naples M, Baker C, Magomedova L, Tam J, Adeli K, Cummins CL, Connelly PW, Ng DS. Lecithin:cholesterol acyltransferase deficiency protects against cholesterol-induced hepatic endoplasmic reticulum stress in mice. J Biol Chem 2012; 287:20755-68. [PMID: 22500017 PMCID: PMC3370258 DOI: 10.1074/jbc.m112.340919] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 04/06/2012] [Indexed: 12/22/2022] Open
Abstract
We recently reported that lecithin:cholesterol acyltransferase (LCAT) knock-out mice, particularly in the LDL receptor knock-out background, are hypersensitive to insulin and resistant to high fat diet-induced insulin resistance (IR) and obesity. We demonstrated that chow-fed Ldlr-/-xLcat+/+ mice have elevated hepatic endoplasmic reticulum (ER) stress, which promotes IR, compared with wild-type controls, and this effect is normalized in Ldlr-/-xLcat-/- mice. In the present study, we tested the hypothesis that hepatic ER cholesterol metabolism differentially regulates ER stress using these models. We observed that the Ldlr-/-xLcat+/+ mice accumulate excess hepatic total and ER cholesterol primarily attributed to increased reuptake of biliary cholesterol as we observed reduced biliary cholesterol in conjunction with decreased hepatic Abcg5/g8 mRNA, increased Npc1l1 mRNA, and decreased Hmgr mRNA and nuclear SREBP2 protein. Intestinal NPC1L1 protein was induced. Expression of these genes was reversed in the Ldlr-/-xLcat-/- mice, accounting for the normalization of total and ER cholesterol and ER stress. Upon feeding a 2% high cholesterol diet (HCD), Ldlr-/-xLcat-/- mice accumulated a similar amount of total hepatic cholesterol compared with the Ldlr-/-xLcat+/+ mice, but the hepatic ER cholesterol levels remained low in conjunction with being protected from HCD-induced ER stress and IR. Hepatic ER stress correlates strongly with hepatic ER free cholesterol but poorly with hepatic tissue free cholesterol. The unexpectedly low ER cholesterol seen in HCD-fed Ldlr-/-xLcat-/- mice was attributable to a coordinated marked up-regulation of ACAT2 and suppressed SREBP2 processing. Thus, factors influencing the accumulation of ER cholesterol may be important for the development of hepatic insulin resistance.
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Affiliation(s)
- Lauren Hager
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
- Department of Physiology, Faculty of Medicine and
| | - Lixin Li
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
| | - Henry Pun
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
| | - Lu Liu
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
| | - Mohammad A. Hossain
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
| | - Graham F. Maguire
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
| | - Mark Naples
- Division of Biochemistry, Hospital for Sick Children, Toronto M5G 1X8, Canada, and
| | - Chris Baker
- Division of Biochemistry, Hospital for Sick Children, Toronto M5G 1X8, Canada, and
| | - Lilia Magomedova
- Faculty of Pharmacy, University of Toronto, Toronto M5S 3M2, Canada
| | - Jonathan Tam
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
| | - Khosrow Adeli
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto M5S 1A8, Canada
- Division of Biochemistry, Hospital for Sick Children, Toronto M5G 1X8, Canada, and
| | | | - Philip W. Connelly
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto M5S 1A8, Canada
| | - Dominic S. Ng
- From the Keenan Research Centre, Li Ka Shing Knowledge Institute, Department of Medicine, St. Michael's Hospital, Toronto M5B 1W8, Canada
- Department of Physiology, Faculty of Medicine and
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto M5S 1A8, Canada
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36
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Leichner GS, Avner R, Harats D, Roitelman J. Metabolically regulated endoplasmic reticulum-associated degradation of 3-hydroxy-3-methylglutaryl-CoA reductase: evidence for requirement of a geranylgeranylated protein. J Biol Chem 2011; 286:32150-61. [PMID: 21778231 PMCID: PMC3173168 DOI: 10.1074/jbc.m111.278036] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 07/18/2011] [Indexed: 11/06/2022] Open
Abstract
In mammalian cells, the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), which catalyzes the rate-limiting step in the mevalonate pathway, is ubiquitylated and degraded by the 26 S proteasome when mevalonate-derived metabolites accumulate, representing a case of metabolically regulated endoplasmic reticulum-associated degradation (ERAD). Here, we studied which mevalonate-derived metabolites signal for HMGR degradation and the ERAD step(s) in which these metabolites are required. In HMGR-deficient UT-2 cells that stably express HMGal, a chimeric protein between β-galactosidase and the membrane region of HMGR, which is necessary and sufficient for the regulated ERAD, we tested inhibitors specific to different steps in the mevalonate pathway. We found that metabolites downstream of farnesyl pyrophosphate but upstream to lanosterol were highly effective in initiating ubiquitylation, dislocation, and degradation of HMGal. Similar results were observed for endogenous HMGR in cells that express this protein. Ubiquitylation, dislocation, and proteasomal degradation of HMGal were severely hampered when production of geranylgeranyl pyrophosphate was inhibited. Importantly, inhibition of protein geranylgeranylation markedly attenuated ubiquitylation and dislocation, implicating for the first time a geranylgeranylated protein(s) in the metabolically regulated ERAD of HMGR.
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Affiliation(s)
- Gil S. Leichner
- From the Department of Human Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978 and
- the Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer 52621, Israel
| | - Rachel Avner
- the Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer 52621, Israel
| | - Dror Harats
- the Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer 52621, Israel
| | - Joseph Roitelman
- From the Department of Human Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978 and
- the Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer 52621, Israel
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37
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Krycer JR, Brown AJ. Cross-talk between the androgen receptor and the liver X receptor: implications for cholesterol homeostasis. J Biol Chem 2011; 286:20637-47. [PMID: 21489984 PMCID: PMC3121513 DOI: 10.1074/jbc.m111.227082] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 04/01/2011] [Indexed: 01/16/2023] Open
Abstract
High cholesterol levels are associated with prostate cancer development. Androgens promote cholesterol accumulation by activating the sterol-regulatory element-binding protein isoform 2 (SREBP-2) transcription factor. However, SREBP-2 is in balance with the liver X receptor (LXR; NR1H2/NR1H3), a transcription factor that prevents cholesterol accumulation. Here, we show that LXR activity is down-regulated by the androgen receptor (AR; NR3C4). In turn, this reduces LXR target gene expression. This antagonism on LXR is also exerted by other steroid hormone receptors, including the estrogen, glucocorticoid, and progesterone receptors. This suggests a generalizable mechanism, but the AR does not affect LXR mRNA levels, protein degradation, or DNA binding. We also found that the AR does not require protein synthesis to influence LXR, suggesting a direct antagonism. However, the AR does not directly bind LXR. The AR N-terminal domain (involved in transactivation), but not its DNA-binding domain, is required to suppress LXR activity, suggesting coactivator competition. Overall, this androgen-mediated antagonism of LXR complements SREBP-2 activation, providing a more complete picture as to how androgens increase cellular cholesterol levels in a prostate cancer setting. Given the cross-talk between other steroid hormone receptors and LXR, hormonal regulation of cholesterol via LXR may occur in a variety of cellular contexts.
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Affiliation(s)
- James Robert Krycer
- From the School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrew John Brown
- From the School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
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