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Ren X, Deng D, Xiang S, Feng J. Promoter hypomethylated PDZK1 acts as a tumorigenic gene in glioma by interacting with AKT1. Aging (Albany NY) 2024; 16:7174-7187. [PMID: 38669103 PMCID: PMC11087087 DOI: 10.18632/aging.205750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 03/25/2024] [Indexed: 04/28/2024]
Abstract
Glioma is the most frequently diagnosed primary brain tumor and typically has a poor prognosis because of malignant proliferation and invasion. It is urgent to elucidate the mechanisms driving glioma tumorigenesis and develop novel treatments to address this deadly disease. Here, we first revealed that PDZK1 is expressed at high levels in gliomas. Promoter hypomethylation may cause high expression of PDZK1 in glioma. Knockdown of PDZK1 inhibits glioma cell proliferation and invasion in vitro. Mechanistically, further investigations revealed that the loss of PDZK1 expression by siRNA inhibited the activation of the AKT/mTOR signaling pathway, leading to cell cycle arrest and apoptosis. Clinically, high expression of PDZK1 predicts a poorer prognosis for glioma patients than low expression of PDZK1. Overall, our study revealed that PDZK1 acts as a novel oncogene in glioma by binding to AKT1 and maintaining the activation of the AKT/mTOR signaling pathway. Thus, PDZK1 may be a potential therapeutic target for glioma.
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Affiliation(s)
- Xing Ren
- Clinical Laboratory Medicine Center, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan, P.R. China
- Cancer Research Institute, The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, Hunan, P.R. China
| | - Dan Deng
- Clinical Laboratory Medicine Center, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan, P.R. China
- Cancer Research Institute, The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, Hunan, P.R. China
| | - Shasha Xiang
- Clinical Laboratory Medicine Center, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan, P.R. China
- Cancer Research Institute, The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, Hunan, P.R. China
| | - Jianbo Feng
- Clinical Laboratory Medicine Center, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan, P.R. China
- Cancer Research Institute, The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang 421001, Hunan, P.R. China
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2
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Mullis DM, Padilla-Lopez A, Wang H, Zhu Y, Elde S, Bonham SA, Yajima S, Kocher ON, Krieger M, Woo YJ. Stromal cell-derived factor-1 alpha improves cardiac function in a novel diet-induced coronary atherosclerosis model, the SR-B1ΔCT/LDLR KO mouse. Atherosclerosis 2024:117518. [PMID: 38627162 DOI: 10.1016/j.atherosclerosis.2024.117518] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 02/28/2024] [Accepted: 03/12/2024] [Indexed: 06/13/2024]
Abstract
BACKGROUND AND AIMS There are a limited number of pharmacologic therapies for coronary artery disease, and few rodent models of occlusive coronary atherosclerosis and consequent myocardial infarction with which one can rapidly test new therapeutic approaches. Here, we characterize a novel, fertile, and easy-to-use HDL receptor (SR-B1)-based model of atherogenic diet-inducible, fatal coronary atherosclerosis, the SR-B1ΔCT/LDLR KO mouse. Additionally, we test intramyocardial injection of Stromal Cell-Derived Factor-1 alpha (SDF-1α), a potent angiogenic cytokine, as a possible therapy to rescue cardiac function in this mouse. METHODS SR-B1ΔCT/LDLR KO mice were fed the Paigen diet or standard chow diet, and we determined the effects of the diets on cardiac function, histology, and survival. After two weeks of feeding either the Paigen diet (n = 24) or standard chow diet (n = 20), the mice received an intramyocardial injection of either SDF-1α or phosphate buffered saline (PBS). Cardiac function and angiogenesis were assessed two weeks later. RESULTS When six-week-old mice were fed the Paigen diet, they began to die as early as 19 days later and 50% had died by 38 days. None of the mice maintained on the standard chow diet died by day 72. Hearts from mice on the Paigen diet showed evidence of cardiomegaly, myocardial infarction, and occlusive coronary artery disease. For the five mice that survived until day 28 that underwent an intramyocardial injection of PBS on day 15, the average ejection fraction (EF) decreased significantly from day 14 (the day before injection, 52.1 ± 4.3%) to day 28 (13 days after the injection, 30.6 ± 6.8%) (paired t-test, n = 5, p = 0.0008). Of the 11 mice fed the Paigen diet and injected with SDF-1α on day 15, 8 (72.7%) survived to day 28. The average EF for these 8 mice increased significantly from 48.2 ± 7.2% on day 14 to63.6 ± 6.9% on day 28 (Paired t-test, n = 8, p = 0.003). CONCLUSIONS This new mouse model and treatment with the promising angiogenic cytokine SDF-1α may lead to new therapeutic approaches for ischemic heart disease.
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Affiliation(s)
- Danielle M Mullis
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | | | - Hanjay Wang
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Yuanjia Zhu
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Stefan Elde
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Spencer A Bonham
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Shin Yajima
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Olivier N Kocher
- Department of Pathology, Beth Israel Hospital, Harvard Medical School, Boston, MA, USA
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, MA, USA
| | - Y Joseph Woo
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA.
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Ho TWW, Henry A, Lee WL. LDL Transcytosis by the Arterial Endothelium-Atherosclerosis by a Thousand Cuts? Curr Atheroscler Rep 2023; 25:457-465. [PMID: 37358804 DOI: 10.1007/s11883-023-01118-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2023] [Indexed: 06/27/2023]
Abstract
PURPOSE OF REVIEW The accumulation of LDL in the arterial intima is an initiating event in atherosclerosis. After decades of controversy, it is now clear that transcytosis of LDL across an intact endothelial monolayer contributes to its intimal deposition. We review recent observations in this field and address the question of whether LDL transcytosis can be manipulated therapeutically. RECENT FINDINGS The development of a live-cell imaging method for studying transcytosis using total internal reflection fluorescence (TIRF) microscopy has catalyzed recent discoveries. LDL transcytosis is mediated by SR-BI and ALK1. Estrogen down-regulates SR-BI and inhibits LDL transcytosis, while the nuclear structural protein HMGB1 promotes LDL transcytosis. LDL transcytosis by ALK1 is independent of the receptor's kinase activity and is antagonized by BMP9, ALK1's canonical ligand. Inflammation stimulates LDL transcytosis. Identifying the function and mechanisms of LDL transcytosis may ultimately permit its therapeutic manipulation.
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Affiliation(s)
- Tse Wing Winnie Ho
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, Toronto, Canada
| | - Andria Henry
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, Toronto, Canada
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Warren L Lee
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, Toronto, Canada.
- Department of Biochemistry, University of Toronto, Toronto, Canada.
- Department of Medicine and the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.
- St. Michael's Hospital, Unity Health Toronto, 30 Bond Street, Toronto, ON, M5B 1W8, Canada.
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Kluck GE, Qian AS, Sakarya EH, Quach H, Deng YD, Trigatti BL. Apolipoprotein A1 Protects Against Necrotic Core Development in Atherosclerotic Plaques: PDZK1-Dependent High-Density Lipoprotein Suppression of Necroptosis in Macrophages. Arterioscler Thromb Vasc Biol 2023; 43:45-63. [PMID: 36353992 PMCID: PMC9762725 DOI: 10.1161/atvbaha.122.318062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Atherosclerosis is a chronic disease affecting artery wall and a major contributor to cardiovascular diseases. Large necrotic cores increase risk of plaque rupture leading to thrombus formation. Necrotic cores are rich in debris from dead macrophages. Programmed necrosis (necroptosis) contributes to necrotic core formation. HDL (high-density lipoprotein) exerts direct atheroprotective effects on different cells within atherosclerotic plaques. Some of these depend on the SR-B1 (scavenger receptor class B type I) and the adapter protein PDZK1 (postsynaptic density protein/Drosophila disc-large protein/Zonula occludens protein containing 1). However, a role for HDL in protecting against necroptosis and necrotic core formation in atherosclerosis is not completely understood. METHODS Low-density lipoprotein receptor-deficient mice engineered to express different amounts of ApoA1 (apolipoprotein A1), or to lack PDZK1 were fed a high fat diet for 10 weeks. Atherosclerotic plaque areas, necrotic cores, and key necroptosis mediators, RIPK3 (receptor interacting protein kinase 3), and MLKL (mixed lineage kinase domain-like protein) were characterized. Cultured macrophages were treated with HDL to determine its effects, as well as the roles of SR-B1, PDZK1, and the PI3K (phosphoinositide 3-kinase) signaling pathway on necroptotic cell death. RESULTS Genetic overexpression reduced, and ApoA1 knockout increased necrotic core formation and RIPK3 and MLKL within atherosclerotic plaques. Macrophages were protected against necroptosis by HDL and this protection required SR-B1, PDZK1, and PI3K/Akt pathway. PDZK1 knockout increased atherosclerosis in LDLRKO mice, increasing necrotic cores and phospho-MLKL; both of which were reversed by restoring PDZK1 in BM-derived cells. CONCLUSIONS Our findings demonstrate that HDL in vitro and ApoA1, in vivo, protect against necroptosis in macrophages and necrotic core formation in atherosclerosis, suggesting a pathway that could be a target for the treatment of atherosclerosis.
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Affiliation(s)
- George E.G. Kluck
- Thrombosis and Atherosclerosis Research Institute, Department of Biochemistry and Biomedical Sciences, McMaster University, and Hamilton Health Sciences, Ontario, Canada
| | - Alexander S. Qian
- Thrombosis and Atherosclerosis Research Institute, Department of Biochemistry and Biomedical Sciences, McMaster University, and Hamilton Health Sciences, Ontario, Canada
| | - Emmanuel H. Sakarya
- Thrombosis and Atherosclerosis Research Institute, Department of Biochemistry and Biomedical Sciences, McMaster University, and Hamilton Health Sciences, Ontario, Canada
| | - Henry Quach
- Thrombosis and Atherosclerosis Research Institute, Department of Biochemistry and Biomedical Sciences, McMaster University, and Hamilton Health Sciences, Ontario, Canada
| | - Yak D. Deng
- Thrombosis and Atherosclerosis Research Institute, Department of Biochemistry and Biomedical Sciences, McMaster University, and Hamilton Health Sciences, Ontario, Canada
| | - Bernardo L. Trigatti
- Thrombosis and Atherosclerosis Research Institute, Department of Biochemistry and Biomedical Sciences, McMaster University, and Hamilton Health Sciences, Ontario, Canada
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Powers HR, Sahoo D. SR-B1's Next Top Model: Structural Perspectives on the Functions of the HDL Receptor. Curr Atheroscler Rep 2022; 24:277-288. [PMID: 35107765 PMCID: PMC8809234 DOI: 10.1007/s11883-022-01001-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2021] [Indexed: 02/04/2023]
Abstract
PURPOSE OF REVIEW The binding of high-density lipoprotein (HDL) to its primary receptor, scavenger receptor class B type 1 (SR-B1), is critical for lowering plasma cholesterol levels and reducing cardiovascular disease risk. This review provides novel insights into how the structural elements of SR-B1 drive efficient function with an emphasis on bidirectional cholesterol transport. RECENT FINDINGS We have generated a new homology model of full-length human SR-B1 based on the recent resolution of the partial structures of other class B scavenger receptors. Interrogating this model against previously published observations allows us to generate structurally informed hypotheses about SR-B1's ability to mediate HDL-cholesterol (HDL-C) transport. Furthermore, we provide a structural perspective as to why human variants of SR-B1 may result in impaired HDL-C clearance. A comprehensive understanding of SR-B1's structure-function relationships is critical to the development of therapeutic agents targeting SR-B1 and modulating cardiovascular disease risk.
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Affiliation(s)
- Hayley R. Powers
- grid.30760.320000 0001 2111 8460Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI USA
| | - Daisy Sahoo
- grid.30760.320000 0001 2111 8460Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI USA ,grid.30760.320000 0001 2111 8460Department of Medicine, Division of Endocrinology & Molecular Medicine, Medical College of Wisconsin, Milwaukee, WI USA ,grid.30760.320000 0001 2111 8460Cardiovascular Center, H4930 Health Research Center, Medical College of Wisconsin, 8701 W. Watertown Plank Road, Milwaukee, WI 53226 USA
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Kluck GEG, Yoo JA, Sakarya EH, Trigatti BL. Good Cholesterol Gone Bad? HDL and COVID-19. Int J Mol Sci 2021; 22:10182. [PMID: 34638523 PMCID: PMC8507803 DOI: 10.3390/ijms221910182] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/15/2021] [Accepted: 09/17/2021] [Indexed: 02/06/2023] Open
Abstract
The transmissible respiratory disease COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected millions of people worldwide since its first reported outbreak in December of 2019 in Wuhan, China. Since then, multiple studies have shown an inverse correlation between the levels of high-density lipoprotein (HDL) particles and the severity of COVID-19, with low HDL levels being associated with an increased risk of severe outcomes. Some studies revealed that HDL binds to SARS-CoV-2 particles via the virus's spike protein and, under certain conditions, such as low HDL particle concentrations, it facilitates SARS-CoV-2 binding to angiotensin-converting enzyme 2 (ACE2) and infection of host cells. Other studies, however, reported that HDL suppressed SARS-CoV-2 infection. In both cases, the ability of HDL to enhance or suppress virus infection appears to be dependent on the expression of the HDL receptor, namely, the Scavenger Receptor Class B type 1 (SR-B1), in the target cells. SR-B1 and HDL represent crucial mediators of cholesterol metabolism. Herein, we review the complex role of HDL and SR-B1 in SARS-CoV-2-induced disease. We also review recent advances in our understanding of HDL structure, properties, and function during SARS-CoV-2 infection and the resulting COVID-19 disease.
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Affiliation(s)
| | | | | | - Bernardo L. Trigatti
- Thrombosis and Atherosclerosis Research Institute and Department of Biochemistry and Biomedical Sciences, McMaster University and Hamilton Health Sciences, Hamilton, ON L8L 2X2, Canada; (G.E.G.K.); (J.-A.Y.); (E.H.S.)
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7
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Li H, Yu XH, Ou X, Ouyang XP, Tang CK. Hepatic cholesterol transport and its role in non-alcoholic fatty liver disease and atherosclerosis. Prog Lipid Res 2021; 83:101109. [PMID: 34097928 DOI: 10.1016/j.plipres.2021.101109] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 12/12/2022]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a quickly emerging global health problem representing the most common chronic liver disease in the world. Atherosclerotic cardiovascular disease represents the leading cause of mortality in NAFLD patients. Cholesterol metabolism has a crucial role in the pathogenesis of both NAFLD and atherosclerosis. The liver is the major organ for cholesterol metabolism. Abnormal hepatic cholesterol metabolism not only leads to NAFLD but also drives the development of atherosclerotic dyslipidemia. The cholesterol level in hepatocytes reflects the dynamic balance between endogenous synthesis, uptake, esterification, and export, a process in which cholesterol is converted to neutral cholesteryl esters either for storage in cytosolic lipid droplets or for secretion as a major constituent of plasma lipoproteins, including very-low-density lipoproteins, chylomicrons, high-density lipoproteins, and low-density lipoproteins. In this review, we describe decades of research aimed at identifying key molecules and cellular players involved in each main aspect of hepatic cholesterol metabolism. Furthermore, we summarize the recent advances regarding the biological processes of hepatic cholesterol transport and its role in NAFLD and atherosclerosis.
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Affiliation(s)
- Heng Li
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan International Scientific and Technological Cooperation Base of Arteriosclerotic Disease, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China
| | - Xiao-Hua Yu
- Institute of Clinical Medicine, The Second Affiliated Hospital of Hainan Medical University, Haikou, Hainan 460106, China
| | - Xiang Ou
- Department of Endocrinology, the First Hospital of Changsha, Changsha, Hunan 410005, China
| | - Xin-Ping Ouyang
- Department of Physiology, Institute of Neuroscience Research, Hengyang Key Laboratory of Neurodegeneration and Cognitive Impairment, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China.
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Hunan International Scientific and Technological Cooperation Base of Arteriosclerotic Disease, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang Medical College, University of South China, Hengyang, Hunan 421001, China.
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8
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Ferreira C, Meyer R, Meyer Zu Schwabedissen HE. The nuclear receptors PXR and LXR are regulators of the scaffold protein PDZK1. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:447-456. [PMID: 30831268 DOI: 10.1016/j.bbagrm.2019.02.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 02/12/2019] [Accepted: 02/13/2019] [Indexed: 02/02/2023]
Abstract
PDZK1 (NHERF3) interacts with membrane proteins whereby modulating their spatial arrangement, membrane stability, and function. One of the membrane proteins shown to be stabilized by interaction with PDZK1 is the HDL-receptor SR-BI (SCARB1). Testing the influence of TO 901317, a known activator of liver X receptor alpha (LXRα, NR1H3) which is a central regulator of the lipid homeostasis, Grefhorst et al. reported in 2012 that administration of TO 901317 did not affect PDZK1 expression and reduced the amount of SR-BI protein in mouse liver. Considering that TO 901317 also activates the xenosensor pregnane X receptor (PXR, NR1I2), it was aim of this study to further investigate the influence of LXRα and PXR activation on transcription of PDZK1. First, we tested the transactivation of PDZK1 by LXRα or PXR in cell-based reporter gene assays comparing the effect of prototypical ligands to that of TO 901317. Ligand mediated activation of LXRα increased, while that of PXR lowered luciferase activity. Further, we located the most likely binding site for LXRα and PXR on the PDZK1 promoter between -85 bp and -54 bp. The transcriptional regulation by LXRα was further supported showing enhanced mRNA expression of PDZK1 in HepG2 cells treated with the selective LXRα-agonist GW3965, while treatment with TO 901317 reduced the protein amount of PDZK1. Taken together, we provide evidence that both LXRα and PXR are transcriptional regulators of PDZK1 supporting the previous notion that the scaffold protein is part of cholesterol homeostasis and drug metabolism.
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Affiliation(s)
- Celio Ferreira
- Biopharmacy, Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland
| | - Ramona Meyer
- Biopharmacy, Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland
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9
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Probing the Architecture of a Multi-PDZ Domain Protein: Structure of PDZK1 in Solution. Structure 2018; 26:1522-1533.e5. [DOI: 10.1016/j.str.2018.07.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 06/12/2018] [Accepted: 07/27/2018] [Indexed: 12/15/2022]
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10
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Yu P, Qian AS, Chathely KM, Trigatti BL. PDZK1 in leukocytes protects against cellular apoptosis and necrotic core development in atherosclerotic plaques in high fat diet fed ldl receptor deficient mice. Atherosclerosis 2018; 276:171-181. [DOI: 10.1016/j.atherosclerosis.2018.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 04/20/2018] [Accepted: 05/02/2018] [Indexed: 02/09/2023]
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Shen WJ, Asthana S, Kraemer FB, Azhar S. Scavenger receptor B type 1: expression, molecular regulation, and cholesterol transport function. J Lipid Res 2018; 59:1114-1131. [PMID: 29720388 DOI: 10.1194/jlr.r083121] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/26/2018] [Indexed: 12/16/2022] Open
Abstract
Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many cellular functions. Cellular cholesterol can be obtained from lipoproteins in a selective pathway of HDL-cholesteryl ester (CE) uptake without parallel apolipoprotein uptake. Scavenger receptor B type 1 (SR-B1) is a cell surface HDL receptor that mediates HDL-CE uptake. It is most abundantly expressed in liver, where it provides cholesterol for bile acid synthesis, and in steroidogenic tissues, where it delivers cholesterol needed for storage or steroidogenesis in rodents. SR-B1 transcription is regulated by trophic hormones in the adrenal gland, ovary, and testis; in the liver and elsewhere, SR-B1 is subject to posttranscriptional and posttranslational regulation. SR-B1 operates in several metabolic processes and contributes to pathogenesis of atherosclerosis, inflammation, hepatitis C virus infection, and other conditions. Here, we summarize characteristics of the selective uptake pathway and involvement of microvillar channels as facilitators of selective HDL-CE uptake. We also present the potential mechanisms of SR-B1-mediated selective cholesterol transport; the transcriptional, posttranscriptional, and posttranslational regulation of SR-B1; and the impact of gene variants on expression and function of human SR-B1. A better understanding of this unique pathway and SR-B1's role may yield improved therapies for a wide variety of conditions.
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Affiliation(s)
- Wen-Jun Shen
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Shailendra Asthana
- Drug Discovery Research Center (DDRC), Translational Health Science and Technology Institute (THSTI), NCR Biotech Science Cluster, Faridabad 121001, Haryana, India
| | - Fredric B Kraemer
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Salman Azhar
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
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12
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Abstract
PURPOSE OF REVIEW To outline the roles of SR-B1 and PDZK1 in hepatic selective HDL cholesterol uptake and reverse cholesterol transport and the consequences for atherosclerosis development. RECENT FINDINGS Much of our understanding of the physiological roles of SR-B1 and PDZK1 in HDL metabolism and atherosclerosis comes from studies of genetically manipulated mice. These show SR-B1 and PDZK1 play key roles in HDL metabolism and protection against atherosclerosis. The recent identification of rare loss of function mutations in the human SCARB1 gene verifies that it plays similar roles in HDL metabolism in humans. Other rare mutations in both the human SCARB1 and PDZK1 genes remain to be characterized but may have potentially devastating consequences to SR-B1 function. SUMMARY Identification of carriers of rare mutations in human SCARB1 and PDZK1 that impair the function of their gene products and characterization of the effects of these mutations on HDL cholesterol levels and atherosclerosis will add to our understanding of the importance of HDL function and cholesterol flux, as opposed to HDL-cholesterol levels, per se, for protection against cardiovascular disease.
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Affiliation(s)
- Bernardo L Trigatti
- aDepartment of Biochemistry and Biomedical Sciences, McMaster University bThrombosis and Atherosclerosis Research Institute, Hamilton Health Sciences and McMaster University, Hamilton, Ontario, Canada
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13
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Gutierrez-Pajares JL, Ben Hassen C, Chevalier S, Frank PG. SR-BI: Linking Cholesterol and Lipoprotein Metabolism with Breast and Prostate Cancer. Front Pharmacol 2016; 7:338. [PMID: 27774064 PMCID: PMC5054001 DOI: 10.3389/fphar.2016.00338] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 09/12/2016] [Indexed: 12/16/2022] Open
Abstract
Studies have demonstrated the significant role of cholesterol and lipoprotein metabolism in the progression of cancer. The SCARB1 gene encodes the scavenger receptor class B type I (SR-BI), which is an 82-kDa glycoprotein with two transmembrane domains separated by a large extracellular loop. SR-BI plays an important role in the regulation of cholesterol exchange between cells and high-density lipoproteins. Accordingly, hepatic SR-BI has been shown to play an essential role in the regulation of the reverse cholesterol transport pathway, which promotes the removal and excretion of excess body cholesterol. In the context of atherosclerosis, SR-BI has been implicated in the regulation of intracellular signaling, lipid accumulation, foam cell formation, and cellular apoptosis. Furthermore, since lipid metabolism is a relevant target for cancer treatment, recent studies have focused on examining the role of SR-BI in this pathology. While signaling pathways have initially been explored in non-tumoral cells, studies with cancer cells have now demonstrated SR-BI's function in tumor progression. In this review, we will discuss the role of SR-BI during tumor development and malignant progression. In addition, we will provide insights into the transcriptional and post-transcriptional regulation of the SCARB1 gene. Overall, studying the role of SR-BI in tumor development and progression should allow us to gain useful information for the development of new therapeutic strategies.
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Affiliation(s)
- Jorge L Gutierrez-Pajares
- Université François Rabelais de Tours, Faculté de Médecine-INSERM UMR1069 "Nutrition, Croissance et Cancer" Tours, France
| | - Céline Ben Hassen
- Université François Rabelais de Tours, Faculté de Médecine-INSERM UMR1069 "Nutrition, Croissance et Cancer" Tours, France
| | - Stéphan Chevalier
- Université François Rabelais de Tours, Faculté de Médecine-INSERM UMR1069 "Nutrition, Croissance et Cancer" Tours, France
| | - Philippe G Frank
- Université François Rabelais de Tours, Faculté de Médecine-INSERM UMR1069 "Nutrition, Croissance et Cancer" Tours, France
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14
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Pal R, Ke Q, Pihan GA, Yesilaltay A, Penman ML, Wang L, Chitraju C, Kang PM, Krieger M, Kocher O. Carboxy-terminal deletion of the HDL receptor reduces receptor levels in liver and steroidogenic tissues, induces hypercholesterolemia, and causes fatal heart disease. Am J Physiol Heart Circ Physiol 2016; 311:H1392-H1408. [PMID: 27694217 DOI: 10.1152/ajpheart.00463.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023]
Abstract
The HDL receptor SR-BI mediates the transfer of cholesteryl esters from HDL to cells and controls HDL abundance and structure. Depending on the genetic background, loss of SR-BI causes hypercholesterolemia, anemia, reticulocytosis, splenomegaly, thrombocytopenia, female infertility, and fatal coronary heart disease (CHD). The carboxy terminus of SR-BI (505QEAKL509) must bind to the cytoplasmic adaptor PDZK1 for normal hepatic-but not steroidogenic cell-expression of SR-BI protein. To determine whether SR-BI's carboxy terminus is also required for normal protein levels in steroidogenic cells, we introduced into SR-BI's gene a 507Ala/STOP mutation that produces a truncated receptor (SR-BIΔCT). As expected, the dramatic reduction of hepatic receptor protein in SR-BIΔCT mice was similar to that in PDZK1 knockout (KO) mice. Unlike SR-BI KO females, SR-BIΔCT females were fertile. The severity of SR-BIΔCT mice's hypercholesterolemia was intermediate between those of SR-BI KO and PDZK1 KO mice. Substantially reduced levels of the receptor in adrenal cortical cells, ovarian cells, and testicular Leydig cells in SR-BIΔCT mice suggested that steroidogenic cells have an adaptor(s) functionally analogous to hepatic PDZK1. When SR-BIΔCT mice were crossed with apolipoprotein E KO mice (SR-BIΔCT/apoE KO), pathologies including hypercholesterolemia, macrocytic anemia, hepatic and splenic extramedullary hematopoiesis, massive splenomegaly, reticulocytosis, thrombocytopenia, and rapid-onset and fatal occlusive coronary arterial atherosclerosis and CHD (median age of death: 9 wk) were observed. These results provide new insights into the control of SR-BI in steroidogenic cells and establish SR-BIΔCT/apoE KO mice as a new animal model for the study of CHD.
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Affiliation(s)
- Rinku Pal
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Qingen Ke
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - German A Pihan
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Ayce Yesilaltay
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Marsha L Penman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Li Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Chandramohan Chitraju
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts
| | - Peter M Kang
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Olivier Kocher
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts;
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15
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Pedersen SW, Moran GE, Sereikaitė V, Haugaard-Kedström LM, Strømgaard K. Importance of a Conserved Lys/Arg Residue for Ligand/PDZ Domain Interactions as Examined by Protein Semisynthesis. Chembiochem 2016; 17:1936-1944. [DOI: 10.1002/cbic.201600322] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Søren W. Pedersen
- Center for Biopharmaceuticals; Department of Drug Design and Pharmacology; University of Copenhagen; Universitetsparken 2 2100 Copenhagen Denmark
| | - Griffin E. Moran
- Center for Biopharmaceuticals; Department of Drug Design and Pharmacology; University of Copenhagen; Universitetsparken 2 2100 Copenhagen Denmark
| | - Vita Sereikaitė
- Center for Biopharmaceuticals; Department of Drug Design and Pharmacology; University of Copenhagen; Universitetsparken 2 2100 Copenhagen Denmark
| | - Linda M. Haugaard-Kedström
- Center for Biopharmaceuticals; Department of Drug Design and Pharmacology; University of Copenhagen; Universitetsparken 2 2100 Copenhagen Denmark
| | - Kristian Strømgaard
- Center for Biopharmaceuticals; Department of Drug Design and Pharmacology; University of Copenhagen; Universitetsparken 2 2100 Copenhagen Denmark
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16
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Sauvanet C, Wayt J, Pelaseyed T, Bretscher A. Structure, Regulation, and Functional Diversity of Microvilli on the Apical Domain of Epithelial Cells. Annu Rev Cell Dev Biol 2015; 31:593-621. [DOI: 10.1146/annurev-cellbio-100814-125234] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Cécile Sauvanet
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
| | - Jessica Wayt
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
| | - Thaher Pelaseyed
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
| | - Anthony Bretscher
- Department of Molecular Biology and Genetics and Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, New York 14853;
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17
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Sarma GN, Moody IS, Ilouz R, Phan RH, Sankaran B, Hall RA, Taylor SS. D-AKAP2:PKA RII:PDZK1 ternary complex structure: insights from the nucleation of a polyvalent scaffold. Protein Sci 2014; 24:105-16. [PMID: 25348485 DOI: 10.1002/pro.2593] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/17/2014] [Accepted: 10/20/2014] [Indexed: 02/02/2023]
Abstract
A-kinase anchoring proteins (AKAPs) regulate cAMP-dependent protein kinase (PKA) signaling in space and time. Dual-specific AKAP2 (D-AKAP2/AKAP10) binds with high affinity to both RI and RII regulatory subunits of PKA and is anchored to transporters through PDZ domain proteins. Here, we describe a structure of D-AKAP2 in complex with two interacting partners and the exact mechanism by which a segment that on its own is disordered presents an α-helix to PKA and a β-strand to PDZK1. These two motifs nucleate a polyvalent scaffold and show how PKA signaling is linked to the regulation of transporters. Formation of the D-AKAP2: PKA binary complex is an important first step for high affinity interaction with PDZK1, and the structure reveals important clues toward understanding this phenomenon. In contrast to many other AKAPs, D-AKAP2 does not interact directly with the membrane protein. Instead, the interaction is facilitated by the C-terminus of D-AKAP2, which contains two binding motifs-the D-AKAP2AKB and the PDZ motif-that are joined by a short linker and only become ordered upon binding to their respective partner signaling proteins. The D-AKAP2AKB binds to the D/D domain of the R-subunit and the C-terminal PDZ motif binds to a PDZ domain (from PDZK1) that serves as a bridging protein to the transporter. This structure also provides insights into the fundamental question of why D-AKAP2 would exhibit a differential mode of binding to the two PKA isoforms.
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Affiliation(s)
- Ganapathy N Sarma
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, 92093-0654; Department of Pharmacology, University of California, San Diego, La Jolla, California, 92093-0654
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18
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Challenges in using cultured primary rodent hepatocytes or cell lines to study hepatic HDL receptor SR-BI regulation by its cytoplasmic adaptor PDZK1. PLoS One 2013; 8:e69725. [PMID: 23936087 PMCID: PMC3720616 DOI: 10.1371/journal.pone.0069725] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 06/12/2013] [Indexed: 12/15/2022] Open
Abstract
Background PDZK1 is a four PDZ-domain containing cytoplasmic protein that binds to a variety of membrane proteins via their C-termini and can influence the abundance, localization and/or function of its target proteins. One of these targets in hepatocytes in vivo is the HDL receptor SR-BI. Normal hepatic expression of SR-BI protein requires PDZK1 - <5% of normal hepatic SR-BI is seen in the livers of PDZK1 knockout mice. Progress has been made in identifying features of PDZK1 required to control hepatic SR-BI in vivo using hepatic expression of wild-type and mutant forms of PDZK1 in wild-type and PDZK1 KO transgenic mice. Such in vivo studies are time consuming and expensive, and cannot readily be used to explore many features of the underlying molecular and cellular mechanisms. Methodology/Principal Findings Here we have explored the potential to use either primary rodent hepatocytes in culture using 2D collagen gels with newly developed optimized conditions or PDZK1/SR-BI co-transfected cultured cell lines (COS, HEK293) for such studies. SR-BI and PDZK1 protein and mRNA expression levels fell rapidly in primary hepatocyte cultures, indicating this system does not adequately mimic hepatocytes in vivo for analysis of the PDZK1 dependence of SR-BI. Although PDZK1 did alter SR-BI protein expression in the cell lines, its influence was independent of SR-BI’s C-terminus, and thus is not likely to occur via the same mechanism as that which occurs in hepatocytes in vivo. Conclusions/Significance Caution must be exercised in using primary hepatocytes or cultured cell lines when studying the mechanism underlying the regulation of hepatic SR-BI by PDZK1. It may be possible to use SR-BI and PDZK1 expression as sensitive markers for the in vivo-like state of hepatocytes to further improve primary hepatocyte cell culture conditions.
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19
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Tsukamoto K, Wales TE, Daniels K, Pal R, Sheng R, Cho W, Stafford W, Engen JR, Krieger M, Kocher O. Noncanonical role of the PDZ4 domain of the adaptor protein PDZK1 in the regulation of the hepatic high density lipoprotein receptor scavenger receptor class B, type I (SR-BI). J Biol Chem 2013; 288:19845-60. [PMID: 23720744 DOI: 10.1074/jbc.m113.460170] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The four PDZ (PDZ1 to PDZ4) domain-containing adaptor protein PDZK1 controls the expression, localization, and function of the HDL receptor scavenger receptor class B, type I (SR-BI), in hepatocytes in vivo. This control depends on both the PDZ4 domain and the binding of SR-BI's cytoplasmic C terminus to the canonical peptide-binding sites of either the PDZ1 or PDZ3 domain (no binding to PDZ2 or PDZ4). Using transgenic mice expressing in the liver domain deletion (ΔPDZ2 or ΔPDZ3), domain replacement (PDZ2→1), or target peptide binding-negative (PDZ4(G389P)) mutants of PDZK1, we found that neither PDZ2 nor PDZ3 nor the canonical target peptide binding activity of PDZ4 were necessary for hepatic SR-BI regulatory activity. Immunohistochemical studies established that the localization of PDZK1 on hepatocyte cell surface membranes in vivo is dependent on its PDZ4 domain and the presence of SR-BI. Analytical ultracentrifugation and hydrogen deuterium exchange mass spectrometry suggested that the requirement of PDZ4 for localization and SR-BI regulation is not due to PDZ4-mediated oligomerization or induction of conformational changes in the PDZ123 portion of PDZK1. However, surface plasmon resonance analysis showed that PDZ4, but not the other PDZ domains, can bind vesicles that mimic the plasma membrane. Thus, PDZ4 may potentiate PDZK1's regulation of SR-BI by promoting its lipid-mediated attachment to the cytoplasmic membrane. Our results show that not all of the PDZ domains of a multi-PDZ domain-containing adaptor protein are required for its biological activities and that both canonical target peptide binding and noncanonical (peptide binding-independent) capacities of PDZ domains may be employed by a single such adaptor for optimal in vivo activity.
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Affiliation(s)
- Kosuke Tsukamoto
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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20
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Birrane G, Mulvaney EP, Pal R, Kinsella BT, Kocher O. Molecular analysis of the prostacyclin receptor's interaction with the PDZ1 domain of its adaptor protein PDZK1. PLoS One 2013; 8:e53819. [PMID: 23457445 PMCID: PMC3566133 DOI: 10.1371/journal.pone.0053819] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 12/03/2012] [Indexed: 01/07/2023] Open
Abstract
The prostanoid prostacyclin, or prostaglandin I2, plays an essential role in many aspects of cardiovascular disease. The actions of prostacyclin are mainly mediated through its activation of the prostacyclin receptor or, in short, the IP. In recent studies, the cytoplasmic carboxy-terminal domain of the IP was shown to bind several PDZ domains of the multi-PDZ adaptor PDZK1. The interaction between the two proteins was found to enhance cell surface expression of the IP and to be functionally important in promoting prostacyclin-induced endothelial cell migration and angiogenesis. To investigate the interaction of the IP with the first PDZ domain (PDZ1) of PDZK1, we generated a nine residue peptide (KK(411)IAACSLC(417)) containing the seven carboxy-terminal amino acids of the IP and measured its binding affinity to a recombinant protein corresponding to PDZ1 by isothermal titration calorimetry. We determined that the IP interacts with PDZ1 with a binding affinity of 8.2 µM. Using the same technique, we also determined that the farnesylated form of carboxy-terminus of the IP does not bind to PDZ1. To understand the molecular basis of these findings, we solved the high resolution crystal structure of PDZ1 bound to a 7-residue peptide derived from the carboxy-terminus of the non-farnesylated form of IP ((411)IAACSLC(417)). Analysis of the structure demonstrates a critical role for the three carboxy-terminal amino acids in establishing a strong interaction with PDZ1 and explains the inability of the farnesylated form of IP to interact with the PDZ1 domain of PDZK1 at least in vitro.
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Affiliation(s)
- Gabriel Birrane
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Eamon P. Mulvaney
- School of Biomolecular and Biomedical Sciences, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland
| | - Rinku Pal
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - B. Therese Kinsella
- School of Biomolecular and Biomedical Sciences, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland
| | - Olivier Kocher
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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21
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Witwer KW. XenomiRs and miRNA homeostasis in health and disease: evidence that diet and dietary miRNAs directly and indirectly influence circulating miRNA profiles. RNA Biol 2012; 9:1147-54. [PMID: 22951590 PMCID: PMC3579881 DOI: 10.4161/rna.21619] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Contributions of dietary miRNAs to circulating small RNA profiles would have profound implications for interpretation of miRNA biomarker studies: presumptive disease-specific markers might instead indicate responses to disease-associated quantitative or qualitative dietary alteration. This examination weighs the evidence for a 2-fold hypothesis: first, that ingested biological matter contributes directly to the miRNA complement of body compartments; and second, that these diet-derived exogenous miRNAs (or "xenomiRs") affect total miRNA profiles as part of a circulating miRNA homeostasis that is altered in many diseases. Homeostasis of high-density lipoprotein (HDL), a known miRNA carrier-provides a model as a proposed component of broader miRNA homeostasis. Further research into the dietary xenomiR hypothesis is needed to ensure rigor in the search for truly disease-specific miRNA biomarkers.
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Affiliation(s)
- Kenneth W Witwer
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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22
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Ardura JA, Friedman PA. Regulation of G protein-coupled receptor function by Na+/H+ exchange regulatory factors. Pharmacol Rev 2011; 63:882-900. [PMID: 21873413 DOI: 10.1124/pr.110.004176] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Many G protein-coupled receptors (GPCR) exert patterns of cell-specific signaling and function. Mounting evidence now supports the view that cytoplasmic adapter proteins contribute critically to this behavior. Adapter proteins recognize highly conserved motifs such as those for Src homology 3 (SH3), phosphotyrosine-binding (PTB), and postsynaptic density 95/discs-large/zona occludens (PDZ) docking sequences in candidate GPCRs. Here we review the behavior of the Na+/H+ exchange regulatory factor (NHERF) family of PDZ adapter proteins on GPCR signalling, trafficking, and function. Structural determinants of NHERF proteins that allow them to recognize targeted GPCRs are considered. NHERF1 and NHERF2 are capable also of modifying the assembled complex of accessory proteins such as β-arrestins, which have been implicated in regulating GPCR signaling. In addition, NHERF1 and NHERF2 modulate GPCR signaling by altering the G protein to which the receptor binds or affect other regulatory proteins that affect GTPase activity, protein kinase A, phospholipase C, or modify downstream signaling events. Small molecules targeting the site of NHERF1-GPCR interaction are being developed and may become important and selective drug candidates.
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Affiliation(s)
- Juan A Ardura
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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23
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Kocher O, Birrane G, Yesilaltay A, Shechter S, Pal R, Daniels K, Krieger M. Identification of the PDZ3 domain of the adaptor protein PDZK1 as a second, physiologically functional binding site for the C terminus of the high density lipoprotein receptor scavenger receptor class B type I. J Biol Chem 2011; 286:25171-86. [PMID: 21602281 PMCID: PMC3137089 DOI: 10.1074/jbc.m111.242362] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/21/2011] [Indexed: 12/11/2022] Open
Abstract
The normal expression, cell surface localization, and function of the murine high density lipoprotein receptor scavenger receptor class B type I (SR-BI) in hepatocytes in vivo, and thus normal lipoprotein metabolism, depend on its four PDZ domain (PDZ1-PDZ4) containing cytoplasmic adaptor protein PDZK1. Previous studies showed that the C terminus of SR-BI ("target peptide") binds directly to PDZ1 and influences hepatic SR-BI protein expression. Unexpectedly an inactivating mutation in PDZ1 (Tyr(20) → Ala) only partially, rather than completely, suppresses the ability of PDZK1 to control hepatic SR-BI. We used isothermal titration calorimetry to show that PDZ3, but not PDZ2 or PDZ4, can also bind the target peptide (K(d) = 37.0 μm), albeit with ∼10-fold lower affinity than PDZ1. This binding is abrogated by a Tyr(253) → Ala substitution. Comparison of the 1.5-Å resolution crystal structure of PDZ3 with its bound target peptide ((505)QEAKL(509)) to that of peptide-bound PDZ1 indicated fewer target peptide stabilizing atomic interactions (hydrogen bonds and hydrophobic interactions) in PDZ3. A double (Tyr(20) → Ala (PDZ1) + Tyr(253) → Ala (PDZ3)) substitution abrogated all target peptide binding to PDZK1. In vivo hepatic expression of a singly substituted (Tyr(253) → Ala (PDZ3)) PDZK1 transgene (Tg) was able to correct all of the SR-BI-related defects in PDZK1 knock-out mice, whereas the doubly substituted [Tyr(20) → Ala (PDZ1) + Tyr(253) → Ala (PDZ3)]Tg was unable to correct these defects. Thus, we conclude that PDZK1-mediated control of hepatic SR-BI requires direct binding of the SR-BI C terminus to either the PDZ1 or PDZ3 domains, and that binding to both domains simultaneously is not required for PDZK1 control of hepatic SR-BI.
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Affiliation(s)
- Olivier Kocher
- Department of Pathology, Harvard Medical School, Boston, Massachusetts 02215, USA.
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