1
|
Kocherlakota S, Swinkels D, Van Veldhoven PP, Baes M. Mouse Models to Study Peroxisomal Functions and Disorders: Overview, Caveats, and Recommendations. Methods Mol Biol 2023; 2643:469-500. [PMID: 36952207 DOI: 10.1007/978-1-0716-3048-8_34] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
During the last three decades many mouse lines were created or identified that are deficient in one or more peroxisomal functions. Different methodologies were applied to obtain global, hypomorph, cell type selective, inducible, and knockin mice. Whereas some models closely mimic pathologies in patients, others strongly deviate or no human counterpart has been reported. Often, mice, apparently endowed with a stronger transcriptional adaptation, have to be challenged with dietary additions or restrictions in order to trigger phenotypic changes. Depending on the inactivated peroxisomal protein, several approaches can be taken to validate the loss-of-function. Here, an overview is given of the available mouse models and their most important characteristics.
Collapse
Affiliation(s)
- Sai Kocherlakota
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Daniëlle Swinkels
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Paul P Van Veldhoven
- Laboratory of Peroxisome Biology and Intracellular Communication, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Myriam Baes
- Laboratory of Cell Metabolism, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium.
| |
Collapse
|
2
|
Xu C, Li H, Tang CK. Sterol carrier protein 2 in lipid metabolism and non-alcoholic fatty liver disease: Pathophysiology, molecular biology, and potential clinical implications. Metabolism 2022; 131:155180. [PMID: 35311663 DOI: 10.1016/j.metabol.2022.155180] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 02/03/2022] [Accepted: 03/13/2022] [Indexed: 11/29/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is considered as the most common chronic liver disease and has become a rapidly global public health problem. Sterol carrier protein 2 (SCP-2), also called non-specific lipid-transfer protein, is predominantly expressed by the liver. SCP-2 plays a key role in intracellular lipid transport and metabolism. SCP-2 has been closely implicated in the development of NAFLD-related metabolic disorders, such as obesity, atherosclerosis, Type 2 diabetes mellitus (T2DM), and gallstones. Recent studies indicate that SCP-2 plays a beneficial role in NAFLD by regulating cholesterol-, endocannabinoid-, and fatty acid-related aspects of lipid metabolism. Hence, in this paper, we summarize the latest findings about the roles of SCP-2 in hepatic steatosis and further describe its molecular function in the pathogenesis of NAFLD.
Collapse
Affiliation(s)
- Can Xu
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, The First Affiliated Hospital of University of South China, Department of Cardiology, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, PR China
| | - Heng Li
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, The First Affiliated Hospital of University of South China, Department of Cardiology, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, PR China.
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, The First Affiliated Hospital of University of South China, Department of Cardiology, Hengyang Medical School, University of South China, Hengyang, Hunan 421001, PR China.
| |
Collapse
|
3
|
Martin GG, Landrock D, McIntosh AL, Milligan S, Landrock KK, Kier AB, Mackie J, Schroeder F. High Glucose and Liver Fatty Acid Binding Protein Gene Ablation Differentially Impact Whole Body and Liver Phenotype in High-Fat Pair-Fed Mice. Lipids 2020; 55:309-327. [PMID: 32314395 DOI: 10.1002/lipd.12238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 03/12/2020] [Accepted: 03/30/2020] [Indexed: 12/14/2022]
Abstract
Ad libitum-fed diets high in fat and carbohydrate (especially fructose) induce weight gain, obesity, and nonalcoholic fatty liver disease (NAFLD) in humans and animal models. However, interpretation is complicated since ad libitum feeding of such diets induces hyperphagia and upregulates expression of liver fatty acid binding protein (L-FABP)-a protein intimately involved in fatty acid and glucose regulation of lipid metabolism. Wild-type (WT) and L-fabp gene ablated (LKO) mice were pair-fed either high-fat diet (HFD) or high-fat/high-glucose diet (HFGD) wherein total carbohydrate was maintained constant but the proportion of glucose was increased at the expense of fructose. In LKO mice, the pair-fed HFD increased body weight and lean tissue mass (LTM) but had no effect on fat tissue mass (FTM) or hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and sterol carrier protein-2), but lower hepatic fatty acid oxidation (decreased serum β-hydroxybutyrate). LKO mice pair-fed HFGD also exhibited increased body weight; however, these mice had increased FTM, not LTM, and increased hepatic fatty vacuolation as compared to pair-fed WT counterparts. These LKO mice also exhibited upregulation of hepatic proteins in fatty acid uptake and cytosolic transport (caveolin and acyl-CoA binding protein, but not sterol carrier protein-2), but there was no change in hepatic fatty acid oxidation (serum β-hydroxybutyrate) as compared to pair-fed WT counterparts.
Collapse
Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Sherrelle Milligan
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - John Mackie
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843, USA
| |
Collapse
|
4
|
Huang H, McIntosh AL, Martin GG, Dangott LJ, Kier AB, Schroeder F. Structural and Functional Interaction of Δ 9-Tetrahydrocannabinol with Liver Fatty Acid Binding Protein (FABP1). Biochemistry 2018; 57:6027-6042. [PMID: 30232874 DOI: 10.1021/acs.biochem.8b00744] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Although serum Δ9-tetrahydrocannabinol (Δ9-THC) undergoes rapid hepatic clearance and metabolism, almost nothing is known regarding the mechanism(s) whereby this highly lipophilic phytocannabinoid is transported for metabolism/excretion. A novel NBD-arachidonoylethanolamide (NBD-AEA) fluorescence displacement assay showed that liver fatty acid binding protein (FABP1), the major hepatic endocannabinoid (EC) binding protein, binds the first major metabolite of Δ9-THC (Δ9-THC-OH) as well as Δ9-THC itself. Circular dichroism (CD) confirmed that not only Δ9-THC and Δ9-THC-OH but also downstream metabolites Δ9-THC-COOH and Δ9-THC-CO-glucuronide directly interact with FABP1. Δ9-THC and metabolite interaction differentially altered the FABP1 secondary structure, increasing total α-helix (all), decreasing total β-sheet (Δ9-THC-COOH, Δ9-THC-CO-glucuronide), increasing turns (Δ9-THC-OH, Δ9-THC-COOH, Δ9-THC-CO-glucuronide), and decreasing unordered structure (Δ9-THC, Δ9-THC-OH). Cultured primary hepatocytes from wild-type (WT) mice took up and converted Δ9-THC to the above metabolites. Fabp1 gene ablation (LKO) dramatically increased hepatocyte accumulation of Δ9-THC and even more so its primary metabolites Δ9-THC-OH and Δ9-THC-COOH. Concomitantly, rtPCR and Western blotting indicated that LKO significantly increased Δ9-THC's ability to regulate downstream nuclear receptor transcription of genes important in both EC ( Napepld > Daglb > Dagla, Naaa, Cnr1) and lipid ( Cpt1A > Fasn, FATP4) metabolism. Taken together, the data indicated that FABP1 may play important roles in Δ9-THC uptake and elimination as well as Δ9-THC induction of genes regulating hepatic EC levels and downstream targets in lipid metabolism.
Collapse
Affiliation(s)
- Huan Huang
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Avery L McIntosh
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Gregory G Martin
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| | - Lawrence J Dangott
- Protein Chemistry Laboratory , Texas A&M University , College Station , Texas 77843-2128 , United States
| | - Ann B Kier
- Department of Pathobiology , Texas A&M University , College Station , Texas 77843-4467 , United States
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843-4466 , United States
| |
Collapse
|
5
|
Burger HM, Abel S, Gelderblom WCA. Modulation of key lipid raft constituents in primary rat hepatocytes by fumonisin B 1 - Implications for cancer promotion in the liver. Food Chem Toxicol 2018; 115:34-41. [PMID: 29510220 DOI: 10.1016/j.fct.2018.03.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 02/07/2018] [Accepted: 03/02/2018] [Indexed: 01/15/2023]
Abstract
Fumonisin B1 (FB1), a group 2B natural occurring carcinogenic mycotoxin, modulated lipid and fatty acid (FA) constituents of lipid rafts isolated from primary hepatocytes following exposure to a cytotoxic concentration of FB1 (250 μM). The major effects observed in rafts, included a significant (p < 0.05) increase in raft cholesterol (CHOL) and glycerophospholipid such as phosphatidylethanolamine (PE), whereas sphingomyelin (SM) decreased (p < 0.05). Changes in lipid constituents resulted in the disruption of important membrane fluidity parameters represented as a decreased (p < 0.05) in the phosphatidylcholine (PC)/PE and PC/(PE+SM) ratios and an increase (p < 0.05) in the CHOL/PL (PL=PC+PE) ratio, suggesting the preservation of lipid raft rigidity and integrity. Observed FA changes in the raft PE fraction included a significant (p < 0.05) increase in C18:2ω-6, C20:3ω-6, C20:4ω-6, C22:4ω-6, C22:5ω-3 and C22:6ω-3, with an increase in total ω-6 and ω-3 polyunsaturated fatty acids (PUFAs). Modulation of the FA content in PE, specifically the C20:4ω-6 PC/PE ratio and PUFA levels, together with changes in CHOL and SM are key determinants regulating the integrity and function of lipid rafts. In primary hepatocytes these changes are associated with the inhibition of cell proliferation and induction of apoptosis. A lipogenic mechanism is proposed whereby FB1 modulates lipid rafts and differentially target cell survival indices of normal and preneoplastic hepatocytes during cancer promotion in the liver.
Collapse
Affiliation(s)
- H-M Burger
- Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, PO Box 1906, Bellville 7535, South Africa.
| | - S Abel
- Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, PO Box 1906, Bellville 7535, South Africa.
| | - W C A Gelderblom
- Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, PO Box 1906, Bellville 7535, South Africa; Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa.
| |
Collapse
|
6
|
Eckstein J, Holzhütter HG, Berndt N. The importance of membrane microdomains for bile salt-dependent biliary lipid secretion. J Cell Sci 2018; 131:jcs211524. [PMID: 29420298 PMCID: PMC5897720 DOI: 10.1242/jcs.211524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/23/2018] [Indexed: 12/13/2022] Open
Abstract
Alternative models explaining the biliary lipid secretion at the canalicular membrane of hepatocytes exist: successive lipid extraction by preformed bile salt micelles, or budding of membrane fragments with formation of mixed micelles. To test the feasibility of the latter mechanism, we developed a mathematical model that describes the formation of lipid microdomains in the canalicular membrane. Bile salt monomers intercalate into the external hemileaflet of the canalicular membrane, to form a rim to liquid disordered domain patches that then pinch off to form nanometer-scale mixed micelles. Model simulations perfectly recapitulate the measured dependence of bile salt-dependent biliary lipid extraction rates upon modulation of the membrane cholesterol (lack or overexpression of the cholesterol transporter Abcg5-Abcg8) and phosphatidylcholine (lack of Mdr2, also known as Abcb4) content. The model reveals a strong dependence of the biliary secretion rate on the protein density of the membrane. Taken together, the proposed model is consistent with crucial experimental findings in the field and provides a consistent explanation of the central molecular processes involved in bile formation.
Collapse
Affiliation(s)
- Johannes Eckstein
- Charité - Universitätsmedizin Berlin, Institute of Biochemistry, Charitéplatz 1, 10117 Berlin, Germany
| | - Hermann-Georg Holzhütter
- Charité - Universitätsmedizin Berlin, Institute of Biochemistry, Charitéplatz 1, 10117 Berlin, Germany
| | - Nikolaus Berndt
- Charité - Universitätsmedizin Berlin, Institute of Biochemistry, Charitéplatz 1, 10117 Berlin, Germany
| |
Collapse
|
7
|
Phillips MC. Is ABCA1 a lipid transfer protein? J Lipid Res 2018; 59:749-763. [PMID: 29305383 DOI: 10.1194/jlr.r082313] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 01/02/2018] [Indexed: 12/16/2022] Open
Abstract
ABCA1 functions as a lipid transporter because it mediates the transfer of cellular phospholipid (PL) and free (unesterified) cholesterol (FC) to apoA-I and related proteins present in the extracellular medium. ABCA1 is a membrane PL translocase and its enzymatic activity leads to transfer of PL molecules from the cytoplasmic leaflet to the exofacial leaflet of a cell plasma membrane (PM). The presence of active ABCA1 in the PM promotes binding of apoA-I to the cell surface. About 10% of this bound apoA-I interacts directly with ABCA1 and stabilizes the transporter. Most of the pool of cell surface-associated apoA-I is bound to lipid domains in the PM that are created by the activity of ABCA1. The amphipathic α-helices in apoA-I confer detergent-like properties on the protein enabling it to solubilize PL and FC in these membrane domains to create a heterogeneous population of discoidal nascent HDL particles. This review focuses on current understanding of the structure-function relationships of human ABCA1 and the molecular mechanisms underlying HDL particle production.
Collapse
Affiliation(s)
- Michael C Phillips
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-5158
| |
Collapse
|
8
|
Milligan S, Martin GG, Landrock D, McIntosh AL, Mackie JT, Schroeder F, Kier AB. Ablating both Fabp1 and Scp2/Scpx (TKO) induces hepatic phospholipid and cholesterol accumulation in high fat-fed mice. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:323-338. [PMID: 29307784 DOI: 10.1016/j.bbalip.2017.12.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 12/13/2017] [Accepted: 12/31/2017] [Indexed: 01/16/2023]
Abstract
Although singly ablating Fabp1 or Scp2/Scpx genes may exacerbate the impact of high fat diet (HFD) on whole body phenotype and non-alcoholic fatty liver disease (NAFLD), concomitant upregulation of the non-ablated gene, preference for ad libitum fed HFD, and sex differences complicate interpretation. Therefore, these issues were addressed in male and female mice ablated in both genes (Fabp1/Scp2/Scpx null or TKO) and pair-fed HFD. Wild-type (WT) males gained more body weight as fat tissue mass (FTM) and exhibited higher hepatic lipid accumulation than WT females. The greater hepatic lipid accumulation in WT males was associated with higher hepatic expression of enzymes in glyceride synthesis, higher hepatic bile acids, and upregulation of transporters involved in hepatic reuptake of serum bile acids. While TKO had little effect on whole body phenotype and hepatic bile acid accumulation in either sex, TKO increased hepatic accumulation of lipids in both, specifically phospholipid and cholesteryl esters in males and females and free cholesterol in females. TKO-induced increases in glycerides were attributed not only to complete loss of FABP1, SCP2 and SCPx, but also in part to sex-dependent upregulation of hepatic lipogenic enzymes. These data with WT and TKO mice pair-fed HFD indicate that: i) Sex significantly impacted the ability of HFD to increase body weight, induce hepatic lipid accumulation and increase hepatic bile acids; and ii) TKO exacerbated the HFD ability to induce hepatic lipid accumulation, regardless of sex, but did not significantly alter whole body phenotype in either sex.
Collapse
Affiliation(s)
- Sherrelle Milligan
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Gregory G Martin
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Avery L McIntosh
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - John T Mackie
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
| |
Collapse
|
9
|
Abstract
Triglyceride molecules represent the major form of storage and transport of fatty acids within cells and in the plasma. The liver is the central organ for fatty acid metabolism. Fatty acids accrue in liver by hepatocellular uptake from the plasma and by de novo biosynthesis. Fatty acids are eliminated by oxidation within the cell or by secretion into the plasma within triglyceride-rich very low-density lipoproteins. Notwithstanding high fluxes through these pathways, under normal circumstances the liver stores only small amounts of fatty acids as triglycerides. In the setting of overnutrition and obesity, hepatic fatty acid metabolism is altered, commonly leading to the accumulation of triglycerides within hepatocytes, and to a clinical condition known as nonalcoholic fatty liver disease (NAFLD). In this review, we describe the current understanding of fatty acid and triglyceride metabolism in the liver and its regulation in health and disease, identifying potential directions for future research. Advances in understanding the molecular mechanisms underlying the hepatic fat accumulation are critical to the development of targeted therapies for NAFLD. © 2018 American Physiological Society. Compr Physiol 8:1-22, 2018.
Collapse
Affiliation(s)
- Michele Alves-Bezerra
- Joan & Sanford I. Weill Department of Medicine, Weill Cornell Medical College, New York, USA
| | - David E Cohen
- Joan & Sanford I. Weill Department of Medicine, Weill Cornell Medical College, New York, USA
| |
Collapse
|
10
|
McIntosh AL, Storey SM, Huang H, Kier AB, Schroeder F. Sex-dependent impact of Scp-2/Scp-x gene ablation on hepatic phytol metabolism. Arch Biochem Biophys 2017; 635:17-26. [PMID: 29051070 DOI: 10.1016/j.abb.2017.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/10/2017] [Accepted: 10/14/2017] [Indexed: 12/19/2022]
Abstract
While prior studies focusing on male mice suggest a role for sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x; DKO) on hepatic phytol metabolism, its role in females is unresolved. This issue was addressed using female and male wild-type (WT) and DKO mice fed a phytoestrogen-free diet without or with 0.5% phytol. GC/MS showed that hepatic: i) phytol was absent and its branched-chain fatty acid (BCFA) metabolites were barely detectable in WT control-fed mice; ii) accumulation of phytol as well as its peroxisomal metabolite BCFAs (phytanic acid » pristanic and 2,3-pristenic acids) was increased by dietary phytol in WT females, but only slightly in WT males; iii) accumulation of phytol and BCFA was further increased by DKO in phytol-fed females, but much more markedly in males. Livers of phytol-fed WT female mice as well as phytol-fed DKO female and male mice also accumulated increased proportion of saturated straight-chain fatty acids (LCFA) at the expense of unsaturated LCFA. Liver phytol accumulation was not due to increased SCP-2 binding/transport of phytol since SCP-2 bound phytanic acid, but not its precursor phytol. Thus, the loss of Scp-2/Scp-x contributed to a sex-dependent hepatic accumulation of dietary phytol and BCFA.
Collapse
Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466, United States
| | - Stephen M Storey
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466, United States
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466, United States
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843-4467, United States
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466, United States.
| |
Collapse
|
11
|
McMahon KM, Scielzo C, Angeloni NL, Deiss-Yehiely E, Scarfo L, Ranghetti P, Ma S, Kaplan J, Barbaglio F, Gordon LI, Giles FJ, Thaxton CS, Ghia P. Synthetic high-density lipoproteins as targeted monotherapy for chronic lymphocytic leukemia. Oncotarget 2017; 8:11219-11227. [PMID: 28061439 PMCID: PMC5355259 DOI: 10.18632/oncotarget.14494] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 12/26/2016] [Indexed: 12/18/2022] Open
Abstract
Chronic lymphocytic leukemia (CLL) remains incurable despite the introduction of new drugs. Therapies targeting receptors and pathways active specifically in malignant B cells might provide better treatment options. For instance, in B cell lymphoma, our group has previously shown that scavenger receptor type B-1 (SR-B1), the high-affinity receptor for cholesterol-rich high-density lipoproteins (HDL), is a therapeutic target. As evidence suggests that targeting cholesterol metabolism in CLL cells may have therapeutic benefit, we examined SR-B1 expression in primary CLL cells from patients. Unlike normal B cells that do not express SR-B1, CLL cells express the receptor. As a result, we evaluated cholesterol-poor synthetic HDL nanoparticles (HDL NP), known for targeting SR-B1, as a therapy for CLL. HDL NPs potently and selectively induce apoptotic cell death in primary CLL cells. HDL NPs had no effect on normal peripheral blood mononuclear cells from healthy individuals or patients with CLL. These data implicate SR-B1 as a target in CLL and HDL NPs as targeted monotherapy for CLL.
Collapse
Affiliation(s)
- Kaylin M McMahon
- Department of Urology, Feinberg School of Medicine, Northwestern University, Tarry, Chicago, IL, USA
| | - Cristina Scielzo
- Università Vita-Salute San Raffaele, Milan, Italy.,Strategic Research Program On CLL and Unit of B cell Neoplasia, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Nicholas L Angeloni
- Department of Urology, Feinberg School of Medicine, Northwestern University, Tarry, Chicago, IL, USA
| | - Elad Deiss-Yehiely
- Department of Urology, Feinberg School of Medicine, Northwestern University, Tarry, Chicago, IL, USA
| | - Lydia Scarfo
- Università Vita-Salute San Raffaele, Milan, Italy.,Strategic Research Program On CLL and Unit of B cell Neoplasia, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Pamela Ranghetti
- Università Vita-Salute San Raffaele, Milan, Italy.,Strategic Research Program On CLL and Unit of B cell Neoplasia, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Shuo Ma
- Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA
| | - Jason Kaplan
- Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA.,Developmental Therapeutics Program of The Division of Hematology Oncology, Feinberg School of Medicine, Chicago, IL, USA
| | - Federica Barbaglio
- Strategic Research Program On CLL and Unit of B cell Neoplasia, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Leo I Gordon
- Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA
| | - Francis J Giles
- Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA.,Developmental Therapeutics Program of The Division of Hematology Oncology, Feinberg School of Medicine, Chicago, IL, USA
| | - C Shad Thaxton
- Department of Urology, Feinberg School of Medicine, Northwestern University, Tarry, Chicago, IL, USA.,Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA.,Simpson Querrey Institute (SQI) for BioNanotechnology, Chicago, IL, USA.,International Institute for Nanotechnology, Evanston, IL, USA
| | - Paolo Ghia
- Università Vita-Salute San Raffaele, Milan, Italy.,Strategic Research Program On CLL and Unit of B cell Neoplasia, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| |
Collapse
|
12
|
Storey SM, Huang H, McIntosh AL, Martin GG, Kier AB, Schroeder F. Impact of Fabp1/Scp-2/Scp-x gene ablation (TKO) on hepatic phytol metabolism in mice. J Lipid Res 2017; 58:1153-1165. [PMID: 28411199 DOI: 10.1194/jlr.m075457] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/07/2017] [Indexed: 01/19/2023] Open
Abstract
Studies in vitro have suggested that both sterol carrier protein-2/sterol carrier protein-x (Scp-2/Scp-x) and liver fatty acid binding protein [Fabp1 (L-FABP)] gene products facilitate hepatic uptake and metabolism of lipotoxic dietary phytol. However, interpretation of physiological function in mice singly gene ablated in the Scp-2/Scp-x has been complicated by concomitant upregulation of FABP1. The work presented herein provides several novel insights: i) An 8-anilino-1-naphthalenesulfonic acid displacement assay showed that neither SCP-2 nor L-FABP bound phytol, but both had high affinity for its metabolite, phytanic acid; ii) GC-MS studies with phytol-fed WT and Fabp1/Scp-2/SCP-x gene ablated [triple KO (TKO)] mice showed that TKO exacerbated hepatic accumulation of phytol metabolites in vivo in females and less so in males. Concomitantly, dietary phytol increased hepatic levels of total long-chain fatty acids (LCFAs) in both male and female WT and TKO mice. Moreover, in both WT and TKO female mice, dietary phytol increased hepatic ratios of saturated/unsaturated and polyunsaturated/monounsaturated LCFAs, while decreasing the peroxidizability index. However, in male mice, dietary phytol selectively increased the saturated/unsaturated ratio only in TKO mice, while decreasing the peroxidizability index in both WT and TKO mice. These findings suggested that: 1) SCP-2 and FABP1 both facilitated phytol metabolism after its conversion to phytanic acid; and 2) SCP-2/SCP-x had a greater impact on hepatic phytol metabolism than FABP1.
Collapse
Affiliation(s)
- Stephen M Storey
- Departments of Physiology and Pharmacology Texas A&M Veterinary Medical Center, Texas A&M University, College Station, TX 77843
| | - Huan Huang
- Departments of Physiology and Pharmacology Texas A&M Veterinary Medical Center, Texas A&M University, College Station, TX 77843
| | - Avery L McIntosh
- Departments of Physiology and Pharmacology Texas A&M Veterinary Medical Center, Texas A&M University, College Station, TX 77843
| | - Gregory G Martin
- Departments of Physiology and Pharmacology Texas A&M Veterinary Medical Center, Texas A&M University, College Station, TX 77843
| | - Ann B Kier
- Pathobiology, Texas A&M Veterinary Medical Center, Texas A&M University, College Station, TX 77843
| | - Friedhelm Schroeder
- Departments of Physiology and Pharmacology Texas A&M Veterinary Medical Center, Texas A&M University, College Station, TX 77843
| |
Collapse
|
13
|
Milligan S, Martin GG, Landrock D, McIntosh AL, Mackie JT, Schroeder F, Kier AB. Impact of dietary phytol on lipid metabolism in SCP2/SCPX/L-FABP null mice. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:291-304. [PMID: 27940000 PMCID: PMC5266609 DOI: 10.1016/j.bbalip.2016.12.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/15/2016] [Accepted: 12/04/2016] [Indexed: 12/20/2022]
Abstract
In vitro studies suggest that liver fatty acid binding protein (L-FABP) and sterol carrier protein-2/sterol carrier protein-x (SCP2/SCPx) gene products facilitate uptake and metabolism and detoxification of dietary-derived phytol in mammals. However, concomitant upregulation of L-FABP in SCP2/SCPx null mice complicates interpretation of their physiological phenotype. Therefore, the impact of ablating both the L-FABP gene and SCP2/SCPx gene (L-FABP/SCP2/SCPx null or TKO) was examined in phytol-fed female wild-type (WT) and TKO mice. TKO increased hepatic total lipid accumulation, primarily phospholipid, by mechanisms involving increased hepatic levels of proteins in the phospholipid synthetic pathway. Concomitantly, TKO reduced expression of proteins in targeting fatty acids towards the triacylglycerol synthetic pathway. Increased hepatic lipid accumulation was not associated with any concomitant upregulation of membrane fatty acid transport/translocase proteins involved in fatty acid uptake (FATP2, FATP4, FATP5 or GOT) or cytosolic proteins involved in fatty acid intracellular targeting (ACBP). In addition, TKO exacerbated dietary phytol-induced whole body weight loss, especially lean tissue mass. Since individually ablating SCPx or SCP2/SCPx elicited concomitant upregulation of L-FABP, these findings with TKO mice help to resolve the contributions of SCP2/SCPx gene ablation on dietary phytol-induced whole body and hepatic lipid phenotype independent of concomitant upregulation of L-FABP.
Collapse
Affiliation(s)
- Sherrelle Milligan
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Gregory G Martin
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Danilo Landrock
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Avery L McIntosh
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - John T Mackie
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology/Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4466, USA
| | - Ann B Kier
- Department of Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
| |
Collapse
|
14
|
Martin GG, Chung S, Landrock D, Landrock KK, Dangott LJ, Peng X, Kaczocha M, Murphy EJ, Kier AB, Schroeder F. Female Mice are Resistant to Fabp1 Gene Ablation-Induced Alterations in Brain Endocannabinoid Levels. Lipids 2016; 51:1007-20. [PMID: 27450559 PMCID: PMC5418128 DOI: 10.1007/s11745-016-4175-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/14/2016] [Indexed: 10/21/2022]
Abstract
Although liver fatty acid binding protein (FABP1, L-FABP) is not detectable in the brain, Fabp1 gene ablation (LKO) markedly increases endocannabinoids (EC) in brains of male mice. Since the brain EC system of females differs significantly from that of males, it was important to determine if LKO differently impacted the brain EC system. LKO did not alter brain levels of arachidonic acid (ARA)-containing EC, i.e. arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG), but decreased non-ARA-containing N-acylethanolamides (OEA, PEA) and 2-oleoylglycerol (2-OG) that potentiate the actions of AEA and 2-AG. These changes in brain potentiating EC levels were not associated with: (1) a net decrease in levels of brain membrane proteins associated with fatty acid uptake and EC synthesis; (2) a net increase in brain protein levels of cytosolic EC chaperones and enzymes in EC degradation; or (3) increased brain protein levels of EC receptors (CB1, TRVP1). Instead, the reduced or opposite responsiveness of female brain EC levels to loss of FABP1 (LKO) correlated with intrinsically lower FABP1 level in livers of WT females than males. These data show that female mouse brain endocannabinoid levels were unchanged (AEA, 2-AG) or decreased (OEA, PEA, 2-OG) by complete loss of FABP1 (LKO).
Collapse
Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX, 77843-4466, USA
| | - Sarah Chung
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX, 77843-4466, USA
| | - Lawrence J Dangott
- Protein Chemistry Laboratory, Texas A&M University, College Station, TX, 77843-2128, USA
| | - Xiaoxue Peng
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Eric J Murphy
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, TX, 77843-4466, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX, 77843-4466, USA.
| |
Collapse
|
15
|
Martin GG, Chung S, Landrock D, Landrock KK, Huang H, Dangott LJ, Peng X, Kaczocha M, Seeger DR, Murphy EJ, Golovko MY, Kier AB, Schroeder F. FABP-1 gene ablation impacts brain endocannabinoid system in male mice. J Neurochem 2016; 138:407-22. [PMID: 27167970 PMCID: PMC4961623 DOI: 10.1111/jnc.13664] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 04/14/2016] [Accepted: 04/26/2016] [Indexed: 12/15/2022]
Abstract
Liver fatty acid-binding protein (FABP1, L-FABP) has high affinity for and enhances uptake of arachidonic acid (ARA, C20:4, n-6) which, when esterified to phospholipids, is the requisite precursor for synthesis of endocannabinoids (EC) such as arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG). The brain derives most of its ARA from plasma, taking up ARA and transporting it intracellularly via cytosolic fatty acid-binding proteins (FABPs 3,5, and 7) localized within the brain. In contrast, the much more prevalent cytosolic FABP1 is not detectable in the brain but is instead highly expressed in the liver. Therefore, the possibility that FABP1 outside the central nervous system may regulate brain AEA and 2-AG was examined in wild-type (WT) and FABP1 null (LKO) male mice. LKO increased brain levels of AA-containing EC (AEA, 2-AG), correlating with increased free and total ARA in brain and serum. LKO also increased brain levels of non-ARA that contain potentiating endocannabinoids (EC*) such as oleoyl ethanolamide (OEA), PEA, 2-OG, and 2-PG. Concomitantly, LKO decreased serum total ARA-containing EC, but not non-ARA endocannabinoids. LKO did not elicit these changes in the brain EC and EC* as a result of compensatory up-regulation of brain protein levels of enzymes in EC synthesis (NAPEPLD, DAGLα) or cytosolic EC chaperone proteins (FABPs 3, 5, 7, SCP-2, HSP70), or cannabinoid receptors (CB1, TRVP1). These data show for the first time that the non-CNS fatty acid-binding protein FABP1 markedly affected brain levels of both ARA-containing endocannabinoids (AEA, 2-AG) as well as their non-ARA potentiating endocannabinoids. Fatty acid-binding protein-1 (FABP-1) is not detectable in brain but instead is highly expressed in liver. The possibility that FABP1 outside the central nervous system may regulate brain endocannabinoids arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) was examined in wild-type (WT) and FABP-1 null (LKO) male mice. LKO increased brain levels of arachidonic acid-containing endocannabinoids (AEA, 2-AG), correlating with increased free and total arachidonic acid in brain and serum. Read the Editorial Highlight for this article on page 371.
Collapse
Affiliation(s)
- Gregory G. Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466
| | - Sarah Chung
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467
| | - Kerstin K. Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466
| | - Lawrence J. Dangott
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128
| | - Xiaoxue Peng
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY 11794
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY 11794
| | - Drew R. Seeger
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037 USA
| | - Eric J. Murphy
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037 USA
| | - Mikhail Y. Golovko
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58202-9037 USA
| | - Ann B. Kier
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466
| |
Collapse
|
16
|
Schroeder F, McIntosh AL, Martin GG, Huang H, Landrock D, Chung S, Landrock KK, Dangott LJ, Li S, Kaczocha M, Murphy EJ, Atshaves BP, Kier AB. Fatty Acid Binding Protein-1 (FABP1) and the Human FABP1 T94A Variant: Roles in the Endocannabinoid System and Dyslipidemias. Lipids 2016; 51:655-76. [PMID: 27117865 PMCID: PMC5408584 DOI: 10.1007/s11745-016-4155-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 01/01/2023]
Abstract
The first discovered member of the mammalian FABP family, liver fatty acid binding protein (FABP1, L-FABP), occurs at high cytosolic concentration in liver, intestine, and in the case of humans also in kidney. While the rat FABP1 is well studied, the extent these findings translate to human FABP1 is not clear-especially in view of recent studies showing that endocannabinoids and cannabinoids represent novel rat FABP1 ligands and FABP1 gene ablation impacts the hepatic endocannabinoid system, known to be involved in non-alcoholic fatty liver (NAFLD) development. Although not detectable in brain, FABP1 ablation nevertheless also impacts brain endocannabinoids. Despite overall tertiary structure similarity, human FABP1 differs significantly from rat FABP1 in secondary structure, much larger ligand binding cavity, and affinities/specificities for some ligands. Moreover, while both mouse and human FABP1 mediate ligand induction of peroxisome proliferator activated receptor-α (PPARα), they differ markedly in pattern of genes induced. This is critically important because a highly prevalent human single nucleotide polymorphism (SNP) (26-38 % minor allele frequency and 8.3 ± 1.9 % homozygous) results in a FABP1 T94A substitution that further accentuates these species differences. The human FABP1 T94A variant is associated with altered body mass index (BMI), clinical dyslipidemias (elevated plasma triglycerides and LDL cholesterol), atherothrombotic cerebral infarction, and non-alcoholic fatty liver disease (NAFLD). Resolving human FABP1 and the T94A variant's impact on the endocannabinoid and cannabinoid system is an exciting challenge due to the importance of this system in hepatic lipid accumulation as well as behavior, pain, inflammation, and satiety.
Collapse
Affiliation(s)
- Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA.
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Sarah Chung
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Kerstin K Landrock
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Lawrence J Dangott
- Department of Biochemistry and Biophysics, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| | - Shengrong Li
- Avanti Polar Lipids, 700 Industrial Park Dr., Alabaster, AL, 35007-9105, USA
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Eric J Murphy
- Department of Pharmacology, Physiology, and Therapeutics and Chemistry, University of North Dakota, Grand Forks, ND, 58202-9037, USA
| | - Barbara P Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX, 77843-4466, USA
| |
Collapse
|
17
|
Jouffe C, Gobet C, Martin E, Métairon S, Morin-Rivron D, Masoodi M, Gachon F. Perturbed rhythmic activation of signaling pathways in mice deficient for Sterol Carrier Protein 2-dependent diurnal lipid transport and metabolism. Sci Rep 2016; 6:24631. [PMID: 27097688 PMCID: PMC4838911 DOI: 10.1038/srep24631] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 03/29/2016] [Indexed: 01/22/2023] Open
Abstract
Through evolution, most of the living species have acquired a time keeping system to anticipate daily changes caused by the rotation of the Earth. In all of the systems this pacemaker is based on a molecular transcriptional/translational negative feedback loop able to generate rhythmic gene expression with a period close to 24 hours. Recent evidences suggest that post-transcriptional regulations activated mostly by systemic cues play a fundamental role in the process, fine tuning the time keeping system and linking it to animal physiology. Among these signals, we consider the role of lipid transport and metabolism regulated by SCP2. Mice harboring a deletion of the Scp2 locus present a modulated diurnal accumulation of lipids in the liver and a perturbed activation of several signaling pathways including PPARα, SREBP, LRH-1, TORC1 and its upstream regulators. This defect in signaling pathways activation feedbacks upon the clock by lengthening the circadian period of animals through post-translational regulation of core clock regulators, showing that rhythmic lipid transport is a major player in the establishment of rhythmic mRNA and protein expression landscape.
Collapse
Affiliation(s)
- Céline Jouffe
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, CH-1011, Switzerland.,Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland
| | - Cédric Gobet
- Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland.,Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Eva Martin
- Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland
| | - Sylviane Métairon
- Functional Genomic, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland
| | - Delphine Morin-Rivron
- Department of Gastro-Intestinal Health &Microbiome, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland
| | - Mojgan Masoodi
- Department of Gastro-Intestinal Health &Microbiome, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland.,Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, M5S 3E2, Canada
| | - Frédéric Gachon
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, CH-1011, Switzerland.,Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, CH-1015 Lausanne, Switzerland.,Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| |
Collapse
|
18
|
Martin GG, Landrock D, Landrock KK, Howles PN, Atshaves BP, Kier AB, Schroeder F. Relative contributions of L-FABP, SCP-2/SCP-x, or both to hepatic biliary phenotype of female mice. Arch Biochem Biophys 2015; 588:25-32. [PMID: 26541319 PMCID: PMC4683591 DOI: 10.1016/j.abb.2015.10.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 10/20/2015] [Accepted: 10/28/2015] [Indexed: 01/01/2023]
Abstract
Both sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x) and liver fatty acid binding protein (L-FABP) have been proposed to function in hepatobiliary bile acid metabolism/accumulation. To begin to address this issue, the impact of ablating L-FABP (LKO) or SCP-2/SCP-x (DKO) individually or both together (TKO) was examined in female mice. Biliary bile acid levels were decreased in LKO, DKO, and TKO mice; however, hepatic bile acid concentration was decreased in LKO mice only. In contrast, biliary phospholipid level was decreased only in TKO mice, while biliary cholesterol levels were unaltered regardless of phenotype. The loss of either or both genes increased hepatic expression of the major bile acid synthetic enzymes (CYP7A1 and/or CYP27A1). Loss of L-FABP and/or SCP-2/SCP-x genes significantly altered the molecular composition of biliary bile acids, but not the proportion of conjugated/unconjugated bile acids or overall bile acid hydrophobicity index. These data suggested that L-FABP was more important in hepatic retention of bile acids, while SCP-2/SCP-x more broadly affected biliary bile acid and phospholipid levels.
Collapse
Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, USA
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA
| | - Philip N Howles
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45219, USA
| | - Barbara P Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, USA.
| |
Collapse
|
19
|
Nanoparticle Targeting and Cholesterol Flux Through Scavenger Receptor Type B-1 Inhibits Cellular Exosome Uptake. Sci Rep 2015; 5:15724. [PMID: 26511855 PMCID: PMC4625174 DOI: 10.1038/srep15724] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 10/01/2015] [Indexed: 12/21/2022] Open
Abstract
Exosomes are nanoscale vesicles that mediate intercellular communication. Cellular exosome uptake mechanisms are not well defined partly due to the lack of specific inhibitors of this complex cellular process. Exosome uptake depends on cholesterol-rich membrane microdomains called lipid rafts, and can be blocked by non-specific depletion of plasma membrane cholesterol. Scavenger receptor type B-1 (SR-B1), found in lipid rafts, is a receptor for cholesterol-rich high-density lipoproteins (HDL). We hypothesized that a synthetic nanoparticle mimic of HDL (HDL NP) that binds SR-B1 and removes cholesterol through this receptor would inhibit cellular exosome uptake. In cell models, our data show that HDL NPs bind SR-B1, activate cholesterol efflux, and attenuate the influx of esterified cholesterol. As a result, HDL NP treatment results in decreased dynamics and clustering of SR-B1 contained in lipid rafts and potently inhibits cellular exosome uptake. Thus, SR-B1 and targeted HDL NPs provide a fundamental advance in studying cholesterol-dependent cellular uptake mechanisms.
Collapse
|
20
|
Klipsic D, Landrock D, Martin GG, McIntosh AL, Landrock KK, Mackie JT, Schroeder F, Kier AB. Impact of SCP-2/SCP-x gene ablation and dietary cholesterol on hepatic lipid accumulation. Am J Physiol Gastrointest Liver Physiol 2015; 309:G387-99. [PMID: 26113298 PMCID: PMC4556946 DOI: 10.1152/ajpgi.00460.2014] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 06/22/2015] [Indexed: 01/31/2023]
Abstract
While a high-cholesterol diet induces hepatic steatosis, the role of intracellular sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x) proteins is unknown. We hypothesized that ablating SCP-2/SCP-x [double knockout (DKO)] would impact hepatic lipids (cholesterol and cholesteryl ester), especially in high-cholesterol-fed mice. DKO did not alter food consumption, and body weight (BW) gain decreased especially in females, concomitant with hepatic steatosis in females and less so in males. DKO-induced steatosis in control-fed wild-type (WT) mice was associated with 1) loss of SCP-2; 2) upregulation of liver fatty acid binding protein (L-FABP); 3) increased mRNA and/or protein levels of sterol regulatory element binding proteins (SREBP1 and SREBP2) as well as increased expression of target genes of cholesterol synthesis (Hmgcs1 and Hmgcr) and fatty acid synthesis (Acc1 and Fas); and 4) cholesteryl ester accumulation was also associated with increased acyl-CoA cholesterol acyltransferase-2 (ACAT2) in males. DKO exacerbated the high-cholesterol diet-induced hepatic cholesterol and glyceride accumulation, without further increasing SREBP1, SREBP2, or target genes. This exacerbation was associated both with loss of SCP-2 and concomitant downregulation of Ceh/Hsl, apolipoprotein B (ApoB), MTP, and/or L-FABP protein expression. DKO diminished the ability to secrete excess cholesterol into bile and oxidize cholesterol to bile acid for biliary excretion, especially in females. This suggested that SCP-2/SCP-x affects cholesterol transport to particular intracellular compartments, with ablation resulting in less to the endoplasmic reticulum for SREBP regulation, making more available for cholesteryl ester synthesis, for cholesteryl-ester storage in lipid droplets, and for bile salt synthesis and/or secretion. These alterations are significant findings, since they affect key processes in regulation of sterol metabolism.
Collapse
Affiliation(s)
- Devon Klipsic
- Department of Pathobiology, Texas A&M University, College Station, Texas; and
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, Texas; and
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas
| | - Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas
| | - John T Mackie
- Department of Pathobiology, Texas A&M University, College Station, Texas; and
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, Texas
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, Texas; and
| |
Collapse
|
21
|
Martin GG, Atshaves BP, Landrock KK, Landrock D, Schroeder F, Kier AB. Loss of L-FABP, SCP-2/SCP-x, or both induces hepatic lipid accumulation in female mice. Arch Biochem Biophys 2015; 580:41-9. [PMID: 26116377 DOI: 10.1016/j.abb.2015.06.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Revised: 06/08/2015] [Accepted: 06/17/2015] [Indexed: 02/06/2023]
Abstract
Although roles for both sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x) and liver fatty acid binding protein (L-FABP) have been proposed in hepatic lipid accumulation, individually ablating these genes has been complicated by concomitant alterations in the other gene product(s). For example, ablating SCP2/SCP-x induces upregulation of L-FABP in female mice. Therefore, the impact of ablating SCP-2/SCP-x (DKO) or L-FABP (LKO) individually or both together (TKO) was examined in female mice. Loss of SCP-2/SCP-x (DKO, TKO) more so than loss of L-FABP alone (LKO) increased hepatic total lipid and total cholesterol content, especially cholesteryl ester. Hepatic accumulation of nonesterified long chain fatty acids (LCFA) and phospholipids occurred only in DKO and TKO mice. Loss of SCP-2/SCP-x (DKO, TKO) increased serum total lipid primarily by increasing triglycerides. Altered hepatic level of proteins involved in cholesterol uptake, efflux, and/or secretion was observed, but did not compensate for the loss of L-FABP, SCP-2/SCP-x or both. However, synergistic responses were not seen with the combinatorial knock out animals-suggesting that inhibiting SCP-2/SCP-x is more correlative with hepatic dysfunction than L-FABP. The DKO- and TKO-induced hepatic accumulation of cholesterol and long chain fatty acids shared significant phenotypic similarities with non-alcoholic fatty liver disease (NAFLD).
Collapse
Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, United States
| | - Barbara P Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, United States
| | - Kerstin K Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, United States
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, United States
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, College Station, TX 77843-4466, United States
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467, United States.
| |
Collapse
|
22
|
Martin GG, Atshaves BP, Landrock KK, Landrock D, Storey SM, Howles PN, Kier AB, Schroeder F. Ablating L-FABP in SCP-2/SCP-x null mice impairs bile acid metabolism and biliary HDL-cholesterol secretion. Am J Physiol Gastrointest Liver Physiol 2014; 307:G1130-43. [PMID: 25277800 PMCID: PMC4254959 DOI: 10.1152/ajpgi.00209.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 09/28/2014] [Indexed: 01/31/2023]
Abstract
On the basis of their abilities to bind bile acids and/or cholesterol, the physiological role(s) of liver fatty acid-binding protein (L-FABP) and sterol carrier protein (SCP) 2/SCP-x (SCP-2/SCP-x) gene products in biliary bile acid and cholesterol formation was examined in gene-ablated male mice. L-FABP (LKO) or L-FABP/SCP-2/SCP-x [triple-knockout (TKO)] ablation markedly decreased hepatic bile acid concentration, while SCP-2/SCP-x [double-knockout (DKO)] ablation alone had no effect. In contrast, LKO increased biliary bile acid, while DKO and TKO had no effect on biliary bile acid levels. LKO and DKO also altered biliary bile acid composition to increase bile acid hydrophobicity. Furthermore, LKO and TKO decreased hepatic uptake and biliary secretion of high-density lipoprotein (HDL)-derived 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol), while DKO alone had no effect. Finally, LKO and, to a lesser extent, DKO decreased most indexes contributing to cholesterol solubility in biliary bile. These results suggest different, but complementary, roles for L-FABP and SCP-2/SCP-x in biliary bile acid and cholesterol formation. L-FABP appears to function more in hepatic retention of bile acids as well as hepatic uptake and biliary secretion of HDL-cholesterol. Conversely, SCP-2/SCP-x may function more in formation and biliary secretion of bile acid, with less impact on hepatic uptake or biliary secretion of HDL-cholesterol.
Collapse
Affiliation(s)
- Gregory G Martin
- Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas
| | - Barbara P Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | - Kerstin K Landrock
- Department of Pathobiology, Texas A & M University, College Station, Texas; and
| | - Danilo Landrock
- Department of Pathobiology, Texas A & M University, College Station, Texas; and
| | - Stephen M Storey
- Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas
| | - Philip N Howles
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Ann B Kier
- Department of Pathobiology, Texas A & M University, College Station, Texas; and
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas;
| |
Collapse
|
23
|
Cerqueira DM, Tran U, Romaker D, Abreu JG, Wessely O. Sterol carrier protein 2 regulates proximal tubule size in the Xenopus pronephric kidney by modulating lipid rafts. Dev Biol 2014; 394:54-64. [PMID: 25127994 DOI: 10.1016/j.ydbio.2014.07.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 05/29/2014] [Accepted: 07/30/2014] [Indexed: 11/29/2022]
Abstract
The kidney is a homeostatic organ required for waste excretion and reabsorption of water, salts and other macromolecules. To this end, a complex series of developmental steps ensures the formation of a correctly patterned and properly proportioned organ. While previous studies have mainly focused on the individual signaling pathways, the formation of higher order receptor complexes in lipid rafts is an equally important aspect. These membrane platforms are characterized by differences in local lipid and protein compositions. Indeed, the cells in the Xenopus pronephric kidney were positive for the lipid raft markers ganglioside GM1 and Caveolin-1. To specifically interfere with lipid raft function in vivo, we focused on the Sterol Carrier Protein 2 (scp2), a multifunctional protein that is an important player in remodeling lipid raft composition. In Xenopus, scp2 mRNA was strongly expressed in differentiated epithelial structures of the pronephric kidney. Knockdown of scp2 did not interfere with the patterning of the kidney along its proximo-distal axis, but dramatically decreased the size of the kidney, in particular the proximal tubules. This phenotype was accompanied by a reduction of lipid rafts, but was independent of the peroxisomal or transcriptional activities of scp2. Finally, disrupting lipid micro-domains by inhibiting cholesterol synthesis using Mevinolin phenocopied the defects seen in scp2 morphants. Together these data underscore the importance for localized signaling platforms in the proper formation of the Xenopus kidney.
Collapse
Affiliation(s)
- Débora M Cerqueira
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA; Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Uyen Tran
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - Daniel Romaker
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - José G Abreu
- Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Oliver Wessely
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA.
| |
Collapse
|
24
|
Storey SM, McIntosh AL, Huang H, Martin GG, Landrock KK, Landrock D, Payne HR, Kier AB, Schroeder F. Loss of intracellular lipid binding proteins differentially impacts saturated fatty acid uptake and nuclear targeting in mouse hepatocytes. Am J Physiol Gastrointest Liver Physiol 2012; 303:G837-50. [PMID: 22859366 PMCID: PMC3469595 DOI: 10.1152/ajpgi.00489.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The liver expresses high levels of two proteins with high affinity for long-chain fatty acids (LCFAs): liver fatty acid binding protein (L-FABP) and sterol carrier protein-2 (SCP-2). Real-time confocal microscopy of cultured primary hepatocytes from gene-ablated (L-FABP, SCP-2/SCP-x, and L-FABP/SCP-2/SCP-x null) mice showed that the loss of L-FABP reduced cellular uptake of 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazo)-aminostearic acid (a fluorescent-saturated LCFA analog) by ∼50%. Importantly, nuclear targeting of the LCFA was enhanced when L-FABP was upregulated (SCP-2/SCP-x null) but was significantly reduced when L-FABP was ablated (L-FABP null), thus impacting LCFA nuclear targeting. These effects were not associated with a net decrease in expression of key membrane proteins involved in LCFA or glucose transport. Since hepatic LCFA uptake and metabolism are closely linked to glucose uptake, the effect of glucose on L-FABP-mediated LCFA uptake and nuclear targeting was examined. Increasing concentrations of glucose decreased cellular LCFA uptake and even more extensively decreased LCFA nuclear targeting. Loss of L-FABP exacerbated the decrease in LCFA nuclear targeting, while loss of SCP-2 reduced the glucose effect, resulting in enhanced LCFA nuclear targeting compared with control. Simply, ablation of L-FABP decreases LCFA uptake and even more extensively decreases its nuclear targeting.
Collapse
Affiliation(s)
- Stephen M. Storey
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Avery L. McIntosh
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Huan Huang
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Gregory G. Martin
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Kerstin K. Landrock
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| | - Danilo Landrock
- 2Department of Pathobiology, Texas A & M University, College Station, Texas
| | - H. Ross Payne
- 2Department of Pathobiology, Texas A & M University, College Station, Texas
| | - Ann B. Kier
- 2Department of Pathobiology, Texas A & M University, College Station, Texas
| | - Friedhelm Schroeder
- 1Department of Physiology and Pharmacology, Texas A & M University, College Station, Texas; and
| |
Collapse
|
25
|
Baes M, Van Veldhoven PP. Mouse models for peroxisome biogenesis defects and β-oxidation enzyme deficiencies. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1489-500. [DOI: 10.1016/j.bbadis.2012.03.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Revised: 02/22/2012] [Accepted: 03/06/2012] [Indexed: 12/26/2022]
|
26
|
Storey SM, McIntosh AL, Huang H, Landrock KK, Martin GG, Landrock D, Payne HR, Atshaves BP, Kier AB, Schroeder F. Intracellular cholesterol-binding proteins enhance HDL-mediated cholesterol uptake in cultured primary mouse hepatocytes. Am J Physiol Gastrointest Liver Physiol 2012; 302:G824-39. [PMID: 22241858 PMCID: PMC3355564 DOI: 10.1152/ajpgi.00195.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 01/07/2012] [Indexed: 01/31/2023]
Abstract
A major gap in our knowledge of rapid hepatic HDL cholesterol clearance is the role of key intracellular factors that influence this process. Although the reverse cholesterol transport pathway targets HDL to the liver for net elimination of free cholesterol from the body, molecular details governing cholesterol uptake into hepatocytes are not completely understood. Therefore, the effects of sterol carrier protein (SCP)-2 and liver fatty acid-binding protein (L-FABP), high-affinity cholesterol-binding proteins present in hepatocyte cytosol, on HDL-mediated free cholesterol uptake were examined using gene-targeted mouse models, cultured primary hepatocytes, and 22-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino]-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol). While SCP-2 overexpression enhanced NBD-cholesterol uptake, counterintuitively, SCP-2/SCP-x gene ablation also 1) enhanced the rapid molecular phase of free sterol uptake detectable in <1 min and initial rate and maximal uptake of HDL free cholesterol and 2) differentially enhanced free cholesterol uptake mediated by the HDL3, rather than the HDL2, subfraction. The increased HDL free cholesterol uptake was not due to increased expression or distribution of the HDL receptor [scavenger receptor B1 (SRB1)], proteins regulating SRB1 [postsynaptic density protein (PSD-95)/Drosophila disk large tumor suppressor (dlg)/tight junction protein (ZO1) and 17-kDa membrane-associated protein], or other intracellular cholesterol trafficking proteins (steroidogenic acute response protein D, Niemann Pick C, and oxysterol-binding protein-related proteins). However, expression of L-FABP, the single most prevalent hepatic cytosolic protein that binds cholesterol, was upregulated twofold in SCP-2/SCP-x null hepatocytes. Double-immunogold electron microscopy detected L-FABP sufficiently close to SRB1 for direct interaction, similar to SCP-2. These data suggest a role for L-FABP in HDL cholesterol uptake, a finding confirmed with SCP-2/SCP-x/L-FABP null mice and hepatocytes. Taken together, these results suggest that L-FABP, particularly in the absence of SCP-2, plays a significant role in HDL-mediated cholesterol uptake in cultured primary hepatocytes.
Collapse
Affiliation(s)
- Stephen M Storey
- Department of Physiology and Pharmacology, Texas Veterinary Medical Center, Texas A & M University, College Station, TX 77843-4466, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
McIntosh AL, Atshaves BP, Storey SM, Landrock KK, Landrock D, Martin GG, Kier AB, Schroeder F. Loss of liver FA binding protein significantly alters hepatocyte plasma membrane microdomains. J Lipid Res 2012; 53:467-480. [PMID: 22223861 PMCID: PMC3276470 DOI: 10.1194/jlr.m019919] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 12/21/2011] [Indexed: 12/13/2022] Open
Abstract
Although lipid-rich microdomains of hepatocyte plasma membranes serve as the major scaffolding regions for cholesterol transport proteins important in cholesterol disposition, little is known regarding intracellular factors regulating cholesterol distribution therein. On the basis of its ability to bind cholesterol and alter hepatic cholesterol accumulation, the cytosolic liver type FA binding protein (L-FABP) was hypothesized to be a candidate protein regulating these microdomains. Compared with wild-type hepatocyte plasma membranes, L-FABP gene ablation significantly increased the proportion of cholesterol-rich microdomains. Lack of L-FABP selectively increased cholesterol, phospholipid (especially phosphatidylcholine), and branched-chain FA accumulation in the cholesterol-rich microdomains. These cholesterol-rich microdomains are important, owing to enrichment therein of significant amounts of key transport proteins involved in uptake of cholesterol [SR-B1, ABCA-1, P-glycoprotein (P-gp), sterol carrier binding protein (SCP-2)], FA transport protein (FATP), and glucose transporters 1 and 2 (GLUT1, GLUT2) insulin receptor. L-FABP gene ablation enhanced the concentration of SCP-2, SR-B1, FATP4, and GLUT1 in the cholesterol-poor microdomains, with functional implications in HDL-mediated uptake and efflux of cholesterol. Thus L-FABP gene ablation significantly impacted the proportion of cholesterol-rich versus -poor microdomains in the hepatocyte plasma membrane and altered the distribution of lipids and proteins involved in cholesterol uptake therein.
Collapse
Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and
| | - Barbara P Atshaves
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Stephen M Storey
- Department of Physiology and Pharmacology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and
| | - Kerstin K Landrock
- Department of Physiology and Pharmacology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and
| | - Danilo Landrock
- Department of Pathobiology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and
| | - Gregory G Martin
- Department of Physiology and Pharmacology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and
| | - Ann B Kier
- Department of Pathobiology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University Texas Veterinary Medical Center, College Station, TX 77843; and.
| |
Collapse
|
28
|
Storey SM, McIntosh AL, Senthivinayagam S, Moon KC, Atshaves BP. The phospholipid monolayer associated with perilipin-enriched lipid droplets is a highly organized rigid membrane structure. Am J Physiol Endocrinol Metab 2011; 301:E991-E1003. [PMID: 21846905 PMCID: PMC3213997 DOI: 10.1152/ajpendo.00109.2011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The significance of lipid droplets (LD) in lipid metabolism, cell signaling, and membrane trafficking is increasingly recognized, yet the role of the LD phospholipid monolayer in LD protein targeting and function remains unknown. To begin to address this issue, two populations of LD were isolated by ConA sepharose affinity chromatography: 1) functionally active LD enriched in perilipin, caveolin-1, and several lipolytic proteins, including ATGL and HSL; and 2) LD enriched in ADRP and TIP47 that contained little to no lipase activity. Coimmunoprecipitation experiments confirmed the close association of caveolin and perilipin and lack of interaction between caveolin and ADRP, in keeping with the separation observed with the ConA procedure. The phospholipid monolayer structure was evaluated to reveal that the perilipin-enriched LD exhibited increased rigidity (less fluidity), as shown by increased cholesterol/phospholipid, Sat/Unsat, and Sat/MUFA ratios. These results were confirmed by DPH-TMA, NBD-cholesterol, and NBD-sphingomyelin fluorescence polarization studies. By structure and organization, the perilipin-enriched LD most closely resembled the adipocyte PM. In contrast, the ADRP/TIP47-enriched LD contained a more fluid monolayer membrane, reflecting decreased polarizations and lipid order based on phospholipid fatty acid analysis. Taken together, results indicate that perilipin and associated lipolytic enzymes target areas in the phospholipid monolayer that are highly organized and rigid, similar in structure to localized areas of the PM where cholesterol and fatty acid uptake and efflux occur.
Collapse
Affiliation(s)
- Stephen M Storey
- Department of Physiology and Pharmacology, Texas A & M University, Texas Veterinary Medical Center, College Station, Texas, USA
| | | | | | | | | |
Collapse
|
29
|
Sommer B, Dingersen T, Gamroth C, Schneider SE, Rubert S, Krüger J, Dietz KJ. CELLmicrocosmos 2.2 MembraneEditor: a modular interactive shape-based software approach to solve heterogeneous membrane packing problems. J Chem Inf Model 2011; 51:1165-82. [PMID: 21504163 DOI: 10.1021/ci1003619] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
New perspectives have been developed to understand the processes of modeling heterogeneous membranes. These are crucial steps prior to applying advanced techniques like molecular dynamic simulations of whole membrane systems. Lipid, protein, and membrane packing problems are addressed based on biochemical properties in combination with computational optimization techniques. The CELLmicrocosmos 2.2 MembraneEditor (CmME) is introduced as an appropriate framework to handle such problems by offering diverse algorithmic approaches. Its algorithm plug-in-interface enables modelers to generate problem-specific algorithms. Good solutions concerning runtime and lipid density are realized by focusing on the outer shapes of the PDB-based molecules. Application cases are presented like the publication-based modeling of inner and outer mitochondrial membrane-fragments, semiautomatic incorporation of proteins, and the assembly of rafts. Concerning geometrical aspects of the lipids, the achieved results are consistent with experimental observations related to lipid densities and distributions. Finally, two membranes simulated with GROMACS are analyzed and compared: the first is generated with conventional scripting techniques, the second with the CmME Distributor algorithm. The examples prove that CmME is a valuable and versatile tool for a broad set of applications in analysis and visualization of biomembranes.
Collapse
Affiliation(s)
- Björn Sommer
- Bio-/Medical Informatics Department, Bielefeld University , D-33615 Bielefeld, Germany
| | | | | | | | | | | | | |
Collapse
|
30
|
Gastaminza P, Dryden KA, Boyd B, Wood MR, Law M, Yeager M, Chisari FV. Ultrastructural and biophysical characterization of hepatitis C virus particles produced in cell culture. J Virol 2010; 84:10999-1009. [PMID: 20686033 PMCID: PMC2953183 DOI: 10.1128/jvi.00526-10] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We analyzed the biochemical and ultrastructural properties of hepatitis C virus (HCV) particles produced in cell culture. Negative-stain electron microscopy revealed that the particles were spherical (∼40- to 75-nm diameter) and pleomorphic and that some of them contain HCV E2 protein and apolipoprotein E on their surfaces. Electron cryomicroscopy revealed two major particle populations of ∼60 and ∼45 nm in diameter. The ∼60-nm particles were characterized by a membrane bilayer (presumably an envelope) that is spatially separated from an internal structure (presumably a capsid), and they were enriched in fractions that displayed a high infectivity-to-HCV RNA ratio. The ∼45-nm particles lacked a membrane bilayer and displayed a higher buoyant density and a lower infectivity-to-HCV RNA ratio. We also observed a minor population of very-low-density, >100-nm-diameter vesicular particles that resemble exosomes. This study provides low-resolution ultrastructural information of particle populations displaying differential biophysical properties and specific infectivity. Correlative analysis of the abundance of the different particle populations with infectivity, HCV RNA, and viral antigens suggests that infectious particles are likely to be present in the large ∼60-nm HCV particle populations displaying a visible bilayer. Our study constitutes an initial approach toward understanding the structural characteristics of infectious HCV particles.
Collapse
Affiliation(s)
- Pablo Gastaminza
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92037, USA.
| | | | | | | | | | | | | |
Collapse
|
31
|
Storey SM, Atshaves BP, McIntosh AL, Landrock KK, Martin GG, Huang H, Ross Payne H, Johnson JD, Macfarlane RD, Kier AB, Schroeder F. Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes. Am J Physiol Gastrointest Liver Physiol 2010; 299:G244-54. [PMID: 20395534 PMCID: PMC2904118 DOI: 10.1152/ajpgi.00446.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Accepted: 04/13/2010] [Indexed: 01/31/2023]
Abstract
Although HDL-mediated cholesterol transport to the liver is well studied, cholesterol efflux from hepatocytes back to HDL is less well understood. Real-time imaging of efflux of 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino)-23,24-bisnor-5-cholen-3beta-ol (NBD-cholesterol), which is poorly esterified, and [(3)H]cholesterol, which is extensively esterified, from cultured primary hepatocytes of wild-type and sterol carrier protein-2 (SCP-2) gene-ablated mice showed that 1) NBD-cholesterol efflux was affected by the type of lipoprotein acceptor, i.e., HDL3 over HDL2; 2) NBD-cholesterol efflux was rapid (detected in 1-2 min) and resolved into fast [half time (t((1/2))) = 2.4 min, 6% of total] and slow (t((1/2)) = 26.5 min, 94% of total) pools, consistent with protein- and vesicle-mediated cholesterol transfer, respectively; 3) SCP-2 gene ablation increased efflux of NBD-cholesterol, as well as [(3)H]cholesterol, albeit less so due to competition by esterification of [(3)H]cholesterol, but not NBD-cholesterol; and 4) SCP-2 gene ablation increased initial rate (2.3-fold) and size (9.7-fold) of rapid effluxing sterol, suggesting an increased contribution of molecular cholesterol transfer. In addition, colocalization, double-immunolabeling fluorescence resonance energy transfer, and electron microscopy, as well as cross-linking coimmunoprecipitation, indicated that SCP-2 directly interacted with the HDL receptor, scavenger receptor class B type 1 (SRB1), in hepatocytes. Other membrane proteins in cholesterol efflux [SRB1 and ATP-binding cassettes (ABC) A-1, ABCG-1, ABCG-5, and ABCG-8] and several soluble/vesicle-associated proteins facilitating intracellular cholesterol trafficking (StARDs, NPCs, ORPs) were not upregulated. However, loss of SCP-2 elicited twofold upregulation of liver fatty acid-binding protein (L-FABP), a protein with lower affinity for cholesterol but higher cytosolic concentration than SCP-2. Ablation of SCP-2 and L-FABP decreased HDL-mediated NBD-cholesterol efflux. These results indicate that SCP-2 expression plays a significant role in HDL-mediated cholesterol efflux by regulating the size of rapid vs. slow cholesterol efflux pools and/or eliciting concomitant upregulation of L-FABP in cultured primary hepatocytes.
Collapse
Affiliation(s)
- Stephen M Storey
- Departmens of Physiology and Pharmacology, Texas Veterinary Medical Center, Texas A & M University, College Station, TX 77843-4466, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Landrock D, Atshaves BP, McIntosh AL, Landrock KK, Schroeder F, Kier AB. Acyl-CoA binding protein gene ablation induces pre-implantation embryonic lethality in mice. Lipids 2010; 45:567-80. [PMID: 20559753 PMCID: PMC2997683 DOI: 10.1007/s11745-010-3437-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 05/29/2010] [Indexed: 11/26/2022]
Abstract
Unique among the intracellular lipid binding proteins, acyl-CoA binding protein (ACBP) exclusively binds long-chain fatty acyl-CoAs (LCFA-CoAs). To test if ACBP is an essential protein in mammals, the ACBP gene was ablated by homologous recombination in mice. While ACBP heterozygotes appeared phenotypically normal, intercrossing of the heterozygotes did not produce any live homozygous deficient (null) ACBP((-/-)) pups. Heterozygous and wild type embryos were detected at all post-implantation stages, but no homozygous ACBP-null embryos were obtained-suggesting that an embryonic lethality occurred at a pre-implantation stage of development, or that embryos never formed. While ACBP-null embryos were not detected at any blastocyst stage, ACBP-null embryos were detected at the morula (8-cell), cleavage (2-cell), and zygote (1-cell) pre-implantation stages. Two other LCFA-CoA binding proteins, sterol carrier protein-2 (SCP-2) and sterol carrier protein-x (SCP-x) were significantly upregulated at these stages. These findings demonstrate for the first time that ACBP is an essential protein required for embryonic development and its loss of function may be initially compensated by concomitant upregulation of two other LCFA-CoA binding proteins, but only at the earliest pre-implantation stages. The fact that ACBP is the first known intracellular lipid binding protein whose deletion results in embryonic lethality suggests its vital importance in mammals.
Collapse
Affiliation(s)
- Danilo Landrock
- Department of Pathobiology, Texas A&M University, TAMU 4467, College Station, TX 77843-4467, USA
| | - Barbara P. Atshaves
- Department of Physiology and Pharmacology, Texas A&M University, TAMU 4466, College Station, TX 77843-4466, USA
| | - Avery L. McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TAMU 4466, College Station, TX 77843-4466, USA
| | - Kerstin K. Landrock
- Department of Physiology and Pharmacology, Texas A&M University, TAMU 4466, College Station, TX 77843-4466, USA
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TAMU 4466, College Station, TX 77843-4466, USA
| | - Ann B. Kier
- Department of Pathobiology, Texas A&M University, TAMU 4467, College Station, TX 77843-4467, USA
| |
Collapse
|
33
|
Huang H, McIntosh AL, Atshaves BP, Ohno-Iwashita Y, Kier AB, Schroeder F. Use of dansyl-cholestanol as a probe of cholesterol behavior in membranes of living cells. J Lipid Res 2010; 51:1157-72. [PMID: 20008119 PMCID: PMC2853442 DOI: 10.1194/jlr.m003244] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Revised: 12/11/2009] [Indexed: 12/21/2022] Open
Abstract
While plasma membrane cholesterol-rich microdomains play a role in cholesterol trafficking, little is known about the appearance and dynamics of cholesterol through these domains in living cells. The fluorescent cholesterol analog 6-dansyl-cholestanol (DChol), its biochemical fractionation, and confocal imaging of L-cell fibroblasts contributed the following new insights: i) fluorescence properties of DChol were sensitive to microenvironment polarity and mobility; (ii) DChol taken up by L-cell fibroblasts was distributed similarly as cholesterol and preferentially into cholesterol-rich vs. -poor microdomains resolved by affinity chromatography of purified plasma membranes; iii) DChol reported similar polarity (dielectric constant near 18) but higher mobility near phospholipid polar head group region for cholesterol in purified cholesterol-rich versus -poor microdomains; and iv) real-time confocal imaging, quantitative colocalization analysis, and fluorescence resonance energy transfer with cholesterol-rich and -poor microdomain markers confirmed that DChol preferentially localized in plasma membrane cholesterol-rich microdomains of living cells. Thus, DChol sensed a unique, relatively more mobile microenvironment for cholesterol in plasma membrane cholesterol-rich microdomains, consistent with the known, more rapid exchange dynamics of cholesterol from cholesterol-rich than -poor microdomains.
Collapse
Affiliation(s)
- Huan Huang
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843
| | - Avery L. McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843
| | - Barbara P. Atshaves
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Yoshiko Ohno-Iwashita
- Biomembrane Research Group, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015, Japan
| | - Ann B. Kier
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843
| |
Collapse
|
34
|
Schroeder F, Huang H, McIntosh AL, Atshaves BP, Martin GG, Kier AB. Caveolin, sterol carrier protein-2, membrane cholesterol-rich microdomains and intracellular cholesterol trafficking. Subcell Biochem 2010; 51:279-318. [PMID: 20213548 DOI: 10.1007/978-90-481-8622-8_10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
While the existence of membrane lateral microdomains has been known for over 30 years, interest in these structures accelerated in the past decade due to the discovery that cholesterol-rich microdomains serve important biological functions. It is increasingly appreciated that cholesterol-rich microdomains in the plasma membranes of eukaryotic cells represent an organizing nexus for multiple cellular proteins involved in transmembrane nutrient uptake (cholesterol, fatty acid, glucose, etc.), cell-signaling, immune recognition, pathogen entry, and many other roles. Despite these advances, however, relatively little is known regarding the organization of cholesterol itself in these plasma membrane microdomains. Although a variety of non-sterol markers indicate the presence of microdomains in the plasma membranes of living cells, none of these studies have demonstrated that cholesterol is enriched in these microdomains in living cells. Further, the role of cholesterol-rich membrane microdomains as targets for intracellular cholesterol trafficking proteins such as sterol carrier protein-2 (SCP-2) that facilitate cholesterol uptake and transcellular transport for targeting storage (cholesterol esters) or efflux is only beginning to be understood. Herein, we summarize the background as well as recent progress in this field that has advanced our understanding of these issues.
Collapse
Affiliation(s)
- Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC College Station, TX, 77843-4466, USA.
| | | | | | | | | | | |
Collapse
|
35
|
Klappe K, Hummel I, Hoekstra D, Kok JW. Lipid dependence of ABC transporter localization and function. Chem Phys Lipids 2009; 161:57-64. [PMID: 19651114 DOI: 10.1016/j.chemphyslip.2009.07.004] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 06/24/2009] [Accepted: 07/24/2009] [Indexed: 02/06/2023]
Abstract
Lipid rafts have been implicated in many cellular functions, including protein and lipid transport and signal transduction. ATP-binding cassette (ABC) transporters have also been localized in these membrane domains. In this review the evidence for this specific localization will be evaluated and discussed in terms of relevance to ABC transporter function. We will focus on three ABC transporters of the A, B and C subfamily, respectively. Two of these transporters are relevant to multidrug resistance in tumor cells (Pgp/ABCB1 and MRP1/ABCC1), while the third (ABCA1) is extensively studied in relation to the reverse cholesterol pathway and cellular cholesterol homeostasis. We will attempt to derive a generalized model of lipid rafts to which they associate based on the use of various different lipid raft isolation procedures. In the context of lipid rafts, modulation of ABC transporter localization and function by two relevant lipid classes, i.e. sphingolipids and cholesterol, will be discussed.
Collapse
Affiliation(s)
- Karin Klappe
- Department of Cell Biology, Section Membrane Cell Biology, University Medical Center Groningen, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | | | | | | |
Collapse
|
36
|
Hostetler HA, McIntosh AL, Atshaves BP, Storey SM, Payne HR, Kier AB, Schroeder F. L-FABP directly interacts with PPARalpha in cultured primary hepatocytes. J Lipid Res 2009; 50:1663-75. [PMID: 19289416 DOI: 10.1194/jlr.m900058-jlr200] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although studies with liver type fatty acid binding protein (L-FABP) gene ablated mice demonstrate a physiological role for L-FABP in hepatic fatty acid metabolism, little is known about the mechanisms whereby L-FABP elicits these effects. Studies indicate that L-FABP may function to shuttle lipids to the nucleus, thereby increasing the availability of ligands of nuclear receptors, such as peroxisome proliferator-activated receptor-alpha (PPARalpha). The data herein suggest that such mechanisms involve direct interaction of L-FABP with PPARalpha. L-FABP was shown to directly interact with PPARalpha in vitro through co-immunoprecipitation (co-IP) of pure proteins, altered circular dichroic (CD) spectra, and altered fluorescence spectra. In vitro fluorescence resonance energy transfer (FRET) between Cy3-labeled PPARalpha and Cy5-labeled L-FABP proteins showed that these proteins bound with high affinity (Kd approximately 156 nM) and in close proximity (intermolecular distance of 52A). This interaction was further substantiated by co-IP of both proteins from liver homogenates of wild-type mice. Moreover, double immunogold electron microscopy and FRET confocal microscopy of cultured primary hepatocytes showed that L-FABP was in close proximity to PPARalpha (intermolecular distance 40-49A) in vivo. Taken together, these studies were consistent with L-FABP regulating PPARalpha transcriptional activity in hepatocytes through direct interaction with PPARalpha. Our in vitro and imaging experiments demonstrate high affinity, structural molecular interaction of L-FABP with PPARalpha and suggest a functional role for L-FABP interaction with PPARalpha in long chain fatty acid (LCFA) metabolism.
Collapse
Affiliation(s)
- Heather A Hostetler
- Department of Physiology and Pharmacology, Texas A&M University, College of Veterinary Medicine and Biomedical Sciences, College Station, TX 77843, USA
| | | | | | | | | | | | | |
Collapse
|
37
|
Atshaves BP, McIntosh AL, Martin GG, Landrock D, Payne HR, Bhuvanendran S, Landrock KK, Lyuksyutova OI, Johnson JD, Macfarlane RD, Kier AB, Schroeder F. Overexpression of sterol carrier protein-2 differentially alters hepatic cholesterol accumulation in cholesterol-fed mice. J Lipid Res 2009; 50:1429-47. [PMID: 19289417 DOI: 10.1194/jlr.m900020-jlr200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Although in vitro studies suggest a role for sterol carrier protein-2 (SCP-2) in cholesterol trafficking and metabolism, the physiological significance of these observations remains unclear. This issue was addressed by examining the response of mice overexpressing physiologically relevant levels of SCP-2 to a cholesterol-rich diet. While neither SCP-2 overexpression nor cholesterol-rich diet altered food consumption, increased weight gain, hepatic lipid, and bile acid accumulation were observed in wild-type mice fed the cholesterol-rich diet. SCP-2 overexpression further exacerbated hepatic lipid accumulation in cholesterol-fed females (cholesterol/cholesteryl esters) and males (cholesterol/cholesteryl esters and triacyglycerol). Primarily in female mice, hepatic cholesterol accumulation induced by SCP-2 overexpression was associated with increased levels of LDL-receptor, HDL-receptor scavenger receptor-B1 (SR-B1) (as well as PDZK1 and/or membrane-associated protein 17 kDa), SCP-2, liver fatty acid binding protein (L-FABP), and 3alpha-hydroxysteroid dehydrogenase, without alteration of other proteins involved in cholesterol uptake (caveolin), esterification (ACAT2), efflux (ATP binding cassette A-1 receptor, ABCG5/8, and apolipoprotein A1), or oxidation/transport of bile salts (cholesterol 7alpha-hydroxylase, sterol 27alpha-hydroxylase, Na(+)/taurocholate cotransporter, Oatp1a1, and Oatp1a4). The effects of SCP-2 overexpression and cholesterol-rich diet was downregulation of proteins involved in cholesterol transport (L-FABP and SR-B1), cholesterol synthesis (related to sterol regulatory element binding protein 2 and HMG-CoA reductase), and bile acid oxidation/transport (via Oapt1a1, Oatp1a4, and SCP-x). Levels of serum and hepatic bile acids were decreased in cholesterol-fed SCP-2 overexpression mice, especially in females, while the total bile acid pool was minimally affected. Taken together, these findings support an important role for SCP-2 in hepatic cholesterol homeostasis.
Collapse
Affiliation(s)
- Barbara P Atshaves
- Department of Physiology and Pharmacology, Texas A&M University, Texas Veterinary Medical Center, College Station, TX 77843-4466, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
McIntosh AL, Atshaves BP, Hostetler HA, Huang H, Davis J, Lyuksyutova OI, Landrock D, Kier AB, Schroeder F. Liver type fatty acid binding protein (L-FABP) gene ablation reduces nuclear ligand distribution and peroxisome proliferator-activated receptor-alpha activity in cultured primary hepatocytes. Arch Biochem Biophys 2009; 485:160-73. [PMID: 19285478 DOI: 10.1016/j.abb.2009.03.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 11/29/2022]
Abstract
The effect of liver type fatty acid binding protein (L-FABP) gene ablation on the uptake and distribution of long chain fatty acids (LCFA) to the nucleus by real-time laser scanning confocal imaging and peroxisome proliferator-activated receptor-alpha (PPARalpha) activity was examined in cultured primary hepatocytes from livers wild-type L-FABP+/+ and gene ablated L-FABP-/- mice. Cultured primary hepatocytes from livers of L-FABP-/- mice exhibited: (i) reduced oxidation of palmitic acid, a common dietary long chain fatty acid (LCFA); (ii) reduced expression of fatty acid oxidative enzymes-proteins transcriptionally regulated by PPARalpha; (iii) reduced palmitic acid-induced PPARalpha co-immunoprecipitation with coactivator SRC-1 concomitant with increased PPARalpha co-immunoprecipitation with coinhibitor N-CoR; (iv) reduced palmitic acid-induced PPARalpha. Diminished PPARalpha activation in L-FABP null hepatocytes was associated with lower uptake of common dietary LCFA (palmitic acid as well as its fluorescent derivative BODIPY FL C(16)), reduced level of total unesterified LCFA, and real-time redistribution of BODIPY FL C(16) from the central nucleoplasm to the nuclear envelope. Taken together, these studies support the hypothesis that L-FABP may facilitate ligand (LCFA)-activated PPARalpha transcriptional activity at least in part by increasing total LCFA ligand available to PPARalpha for inducing PPARalpha-mediated transcription of proteins involved in LCFA metabolism.
Collapse
Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, TVMC College Station, TX 77843-4466, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
39
|
McIntosh AL, Atshaves BP, Huang H, Gallegos AM, Kier AB, Schroeder F. Fluorescence techniques using dehydroergosterol to study cholesterol trafficking. Lipids 2008; 43:1185-208. [PMID: 18536950 PMCID: PMC2606672 DOI: 10.1007/s11745-008-3194-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Accepted: 05/09/2008] [Indexed: 12/22/2022]
Abstract
Cholesterol itself has very few structural/chemical features suitable for real-time imaging in living cells. Thus, the advent of dehydroergosterol [ergosta-5,7,9(11),22-tetraen-3beta-ol, DHE] the fluorescent sterol most structurally and functionally similar to cholesterol to date, has proven to be a major asset for real-time probing/elucidating the sterol environment and intracellular sterol trafficking in living organisms. DHE is a naturally occurring, fluorescent sterol analog that faithfully mimics many of the properties of cholesterol. Because these properties are very sensitive to sterol structure and degradation, such studies require the use of extremely pure (>98%) quantities of fluorescent sterol. DHE is readily bound by cholesterol-binding proteins, is incorporated into lipoproteins (from the diet of animals or by exchange in vitro), and for real-time imaging studies is easily incorporated into cultured cells where it co-distributes with endogenous sterol. Incorporation from an ethanolic stock solution to cell culture media is effective, but this process forms an aqueous dispersion of DHE crystals which can result in endocytic cellular uptake and distribution into lysosomes which is problematic in imaging DHE at the plasma membrane of living cells. In contrast, monomeric DHE can be incorporated from unilamellar vesicles by exchange/fusion with the plasma membrane or from DHE-methyl-beta-cyclodextrin (DHE-MbetaCD) complexes by exchange with the plasma membrane. Both of the latter techniques can deliver large quantities of monomeric DHE with significant distribution into the plasma membrane. The properties and behavior of DHE in protein-binding, lipoproteins, model membranes, biological membranes, lipid rafts/caveolae, and real-time imaging in living cells indicate that this naturally occurring fluorescent sterol is a useful mimic for probing the properties of cholesterol in these systems.
Collapse
Affiliation(s)
- Avery L. McIntosh
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| | - Barbara P. Atshaves
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| | - Huan Huang
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| | - Adalberto M. Gallegos
- Department of Pathobiology Texas A&M University, TVMC College Station, TX 77843-4467
| | - Ann B. Kier
- Department of Pathobiology Texas A&M University, TVMC College Station, TX 77843-4467
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology Texas A&M University, TVMC College Station, TX 77843-4466
| |
Collapse
|
40
|
McIntosh AL, Atshaves BP, Gallegos AM, Storey SM, Reibenspies JH, Kier AB, Meyer E, Schroeder F. Structure of dehydroergosterol monohydrate and interaction with sterol carrier protein-2. Lipids 2008; 43:1165-84. [PMID: 19020914 DOI: 10.1007/s11745-008-3267-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Accepted: 10/31/2008] [Indexed: 10/21/2022]
Abstract
Dehydroergosterol [ergosta-5,7,9(11),22-tetraen-3beta-ol] is a naturally-occurring, fluorescent sterol utilized extensively to probe membrane cholesterol distribution, cholesterol-protein interactions, and intracellular cholesterol transport both in vitro and in vivo. In aqueous solutions, the low solubility of dehydroergosterol results in the formation of monohydrate crystals similar to cholesterol. Low temperature X-ray diffraction analysis reveals that dehydroergosterol monohydrate crystallizes in the space group P2(1) with four molecules in the unit cell and monoclinic crystal parameters a = 9.975(1) A, b = 7.4731(9) A, c = 34.054(4) A, and beta = 92.970(2) degrees somewhat similar to ergosterol monohydrate. The molecular arrangement is in a slightly closer packed bilayer structure resembling cholesterol monohydrate. Since dehydroergosterol fluorescence emission undergoes a quantum yield enhancement and red-shift of its maximum wavelength when crystallized, formation or disruption of microcrystals was monitored with high sensitivity using cuvette-based spectroscopy and multi-photon laser scanning imaging microscopy. This manuscript reports on the dynamical effect of sterol carrier protein-2 (SCP-2) interacting between aqueous dispersions of dehydroergosterol monohydrate microcrystal donors and acceptors consisting not only of model membranes but also vesicles derived from plasma membranes isolated by biochemical fractionation and affinity purification from Madin-Darby canine kidney cells. Furthermore, this study provides real-time measurements of the effect of increased SCP-2 levels on the rate of disappearance of dehydroergosterol microcrystals in living cells.
Collapse
Affiliation(s)
- Avery L McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466, USA
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Martin GG, Hostetler HA, McIntosh AL, Tichy SE, Williams BJ, Russell DH, Berg JM, Spencer TA, Ball J, Kier AB, Schroeder F. Structure and function of the sterol carrier protein-2 N-terminal presequence. Biochemistry 2008; 47:5915-34. [PMID: 18465878 PMCID: PMC2474712 DOI: 10.1021/bi800251e] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Although sterol carrier protein-2 (SCP-2) is encoded as a precursor protein (proSCP-2), little is known regarding the structure and function of the 20-amino acid N-terminal presequence. As shown herein, the presequence contains significant secondary structure and alters SCP-2: (i) secondary structure (CD), (ii) tertiary structure (aqueous exposure of Trp shown by UV absorbance, fluorescence, and fluorescence quenching), (iii) ligand binding site [Trp response to ligands, peptide cross-linked by photoactivatable free cholesterol (FCBP)], (iv) selectivity for interaction with anionic phospholipid-rich membranes, (v) interaction with a peroxisomal import protein [FRET studies of Pex5p(C) binding], the N-terminal presequence increased SCP-2's affinity for Pex5p(C) by 10-fold, and (vi) intracellular targeting in living and fixed cells (confocal microscopy). Nearly 5-fold more SCP-2 than proSCP-2 colocalized with plasma membrane lipid rafts and caveolae (AF488-CTB); 2.8-fold more SCP-2 than proSCP-2 colocalized with a mitochondrial marker (Mitotracker), but nearly 2-fold less SCP-2 than proSCP-2 colocalized with peroxisomes (AF488 antibody to PMP70). These data indicate the importance of the N-terminal presequence in regulating SCP-2 structure, cholesterol localization within the ligand binding site, membrane association, and, potentially, intracellular targeting.
Collapse
Affiliation(s)
- Gregory G. Martin
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466
| | - Heather A. Hostetler
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466
| | - Avery L. McIntosh
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466
| | - Shane E. Tichy
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255
| | - Brad J. Williams
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255
| | - David H. Russell
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255
| | - Jeremy M. Berg
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | | | - Judith Ball
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467
| | - Ann B. Kier
- Department of Pathobiology, Texas A&M University, College Station, TX 77843-4467
| | - Friedhelm Schroeder
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4466
| |
Collapse
|
42
|
Storey SM, Gallegos AM, Atshaves BP, McIntosh AL, Martin GG, Parr RD, Landrock KK, Kier AB, Ball JM, Schroeder F. Selective cholesterol dynamics between lipoproteins and caveolae/lipid rafts. Biochemistry 2007; 46:13891-906. [PMID: 17990854 DOI: 10.1021/bi700690s] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Although low-density lipoprotein (LDL) receptor-mediated cholesterol uptake through clathrin-coated pits is now well understood, the molecular details and organizing principles for selective cholesterol uptake/efflux (reverse cholesterol transport, RCT) from peripheral cells remain to be resolved. It is not yet completely clear whether RCT between serum lipoproteins and the plasma membrane occurs primarily through lipid rafts/caveolae or from non-raft domains. To begin to address these issues, lipid raft/caveolae-, caveolae-, and non-raft-enriched fractions were resolved from purified plasma membranes isolated from L-cell fibroblasts and MDCK cells by detergent-free affinity chromatography and compared with detergent-resistant membranes isolated from the same cells. Fluorescent sterol exchange assays between lipoproteins (VLDL, LDL, HDL, apoA1) and these enriched domains provided new insights into supporting the role of lipid rafts/caveolae and caveolae in plasma membrane/lipoprotein cholesterol dynamics: (i) lipids known to be translocated through caveolae were detected (cholesteryl ester, triacylglycerol) and/or enriched (cholesterol, phospholipid) in lipid raft/caveolae fractions; (ii) lipoprotein-mediated sterol uptake/efflux from lipid rafts/caveolae and caveolae was rapid and lipoprotein specific, whereas that from non-rafts was very slow and independent of lipoprotein class; and (iii) the rate and lipoprotein specificity of sterol efflux from lipid rafts/caveolae or caveolae to lipoprotein acceptors in vitro was slower and differed in specificity from that in intact cells-consistent with intracellular factors contributing significantly to cholesterol dynamics between the plasma membrane and lipoproteins.
Collapse
Affiliation(s)
- Stephen M Storey
- Department of Pathobiology, Texas A&M University, TVMC College Station, Texas 77843-4467, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|