1
|
Morandi V, Petrik J, Lawler J. Endothelial Cell Behavior Is Determined by Receptor Clustering Induced by Thrombospondin-1. Front Cell Dev Biol 2021; 9:664696. [PMID: 33869231 PMCID: PMC8044760 DOI: 10.3389/fcell.2021.664696] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/10/2021] [Indexed: 11/13/2022] Open
Abstract
The thrombospondins (TSPs) are a family of multimeric extracellular matrix proteins that dynamically regulate cellular behavior and response to stimuli. In so doing, the TSPs directly and indirectly affect biological processes such as embryonic development, wound healing, immune response, angiogenesis, and cancer progression. Many of the direct effects of Thrombospondin 1 (TSP-1) result from the engagement of a wide range of cell surface receptors including syndecans, low density lipoprotein receptor-related protein 1 (LRP1), CD36, integrins, and CD47. Different or even opposing outcomes of TSP-1 actions in certain pathologic contexts may occur, depending on the structural/functional domain involved. To expedite response to external stimuli, these receptors, along with vascular endothelial growth factor receptor 2 (VEGFR2) and Src family kinases, are present in specific membrane microdomains, such as lipid rafts or tetraspanin-enriched microdomains. The molecular organization of these membrane microdomains and their constituents is modulated by TSP-1. In this review, we will describe how the presence of TSP-1 at the plasma membrane affects endothelial cell signal transduction and angiogenesis.
Collapse
Affiliation(s)
| | - Jim Petrik
- University of Guelph, Guelph, ON, Canada
| | - Jack Lawler
- Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| |
Collapse
|
2
|
Yusuf B, Mukovozov I, Patel S, Huang YW, Liu GY, Reddy EC, Skrtic M, Glogauer M, Robinson LA. The neurorepellent, Slit2, prevents macrophage lipid loading by inhibiting CD36-dependent binding and internalization of oxidized low-density lipoprotein. Sci Rep 2021; 11:3614. [PMID: 33574432 PMCID: PMC7878733 DOI: 10.1038/s41598-021-83046-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 01/24/2021] [Indexed: 01/03/2023] Open
Abstract
Atherosclerosis is characterized by retention of modified lipoproteins, especially oxidized low density lipoprotein (oxLDL) within the sub-endothelial space of affected blood vessels. Recruited monocyte-derived and tissue-resident macrophages subsequently ingest oxLDL by binding and internalizing oxLDL via scavenger receptors, particularly CD36. The secreted neurorepellent, Slit2, acting through its transmembrane receptor, Roundabout-1 (Robo-1), was previously shown to inhibit recruitment of monocytes into nascent atherosclerotic lesions. The effects of Slit2 on oxLDL uptake by macrophages have not been explored. We report here that Slit2 inhibits uptake of oxLDL by human and murine macrophages, and the resulting formation of foam cells, in a Rac1-dependent and CD36-dependent manner. Exposure of macrophages to Slit2 prevented binding of oxLDL to the surface of cells. Using super-resolution microscopy, we observed that exposure of macrophages to Slit2 induced profound cytoskeletal remodeling with formation of a thick ring of cortical actin within which clusters of CD36 could not aggregate, thereby attenuating binding of oxLDL to the surface of cells. By inhibiting recruitment of monocytes into early atherosclerotic lesions, and the subsequent binding and internalization of oxLDL by macrophages, Slit2 could represent a potent new tool to combat individual steps that collectively result in progression of atherosclerosis.
Collapse
Affiliation(s)
- Bushra Yusuf
- Program in Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, M5S 2Z9, Canada
| | - Ilya Mukovozov
- Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada
| | - Sajedabanu Patel
- Program in Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada
| | - Yi-Wei Huang
- Program in Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada
| | - Guang Ying Liu
- Program in Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada
| | - Emily C Reddy
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada
| | - Marko Skrtic
- Program in Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada
| | - Michael Glogauer
- Faculty of Dentistry, Matrix Dynamics Group, University of Toronto, Toronto, ON, M5G 1G6, Canada
| | - Lisa A Robinson
- Program in Cell Biology, The Hospital for Sick Children Research Institute, Toronto, ON, M5G 1X8, Canada. .,Institute of Medical Science, University of Toronto, Toronto, ON, M5S 2Z9, Canada. .,Department of Paediatrics, University of Toronto, Toronto, ON, M5G 1X8, Canada.
| |
Collapse
|
3
|
Abumrad NA, Cabodevilla AG, Samovski D, Pietka T, Basu D, Goldberg IJ. Endothelial Cell Receptors in Tissue Lipid Uptake and Metabolism. Circ Res 2021; 128:433-450. [PMID: 33539224 DOI: 10.1161/circresaha.120.318003] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Lipid uptake and metabolism are central to the function of organs such as heart, skeletal muscle, and adipose tissue. Although most heart energy derives from fatty acids (FAs), excess lipid accumulation can cause cardiomyopathy. Similarly, high delivery of cholesterol can initiate coronary artery atherosclerosis. Hearts and arteries-unlike liver and adrenals-have nonfenestrated capillaries and lipid accumulation in both health and disease requires lipid movement from the circulation across the endothelial barrier. This review summarizes recent in vitro and in vivo findings on the importance of endothelial cell receptors and uptake pathways in regulating FAs and cholesterol uptake in normal physiology and cardiovascular disease. We highlight clinical and experimental data on the roles of ECs in lipid supply to tissues, heart, and arterial wall in particular, and how this affects organ metabolism and function. Models of FA uptake into ECs suggest that receptor-mediated uptake predominates at low FA concentrations, such as during fasting, whereas FA uptake during lipolysis of chylomicrons may involve paracellular movement. Similarly, in the setting of an intact arterial endothelial layer, recent and historic data support a role for receptor-mediated processes in the movement of lipoproteins into the subarterial space. We conclude with thoughts on the need to better understand endothelial lipid transfer for fuller comprehension of the pathophysiology of hyperlipidemia, and lipotoxic diseases such as some forms of cardiomyopathy and atherosclerosis.
Collapse
Affiliation(s)
- Nada A Abumrad
- Division of Nutritional Sciences, Department of Medicine, Washington University School of Medicine, Saint Louis, MO (N.A.A., D.S., T.P.)
| | - Ainara G Cabodevilla
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, New York University Grossman School of Medicine (A.G.C., D.B., I.J.G.)
| | - Dmitri Samovski
- Division of Nutritional Sciences, Department of Medicine, Washington University School of Medicine, Saint Louis, MO (N.A.A., D.S., T.P.)
| | - Terri Pietka
- Division of Nutritional Sciences, Department of Medicine, Washington University School of Medicine, Saint Louis, MO (N.A.A., D.S., T.P.)
| | - Debapriya Basu
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, New York University Grossman School of Medicine (A.G.C., D.B., I.J.G.)
| | - Ira J Goldberg
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, New York University Grossman School of Medicine (A.G.C., D.B., I.J.G.)
| |
Collapse
|
4
|
Conrad KS, Cheng TW, Ysselstein D, Heybrock S, Hoth LR, Chrunyk BA, Am Ende CW, Krainc D, Schwake M, Saftig P, Liu S, Qiu X, Ehlers MD. Lysosomal integral membrane protein-2 as a phospholipid receptor revealed by biophysical and cellular studies. Nat Commun 2017; 8:1908. [PMID: 29199275 PMCID: PMC5712522 DOI: 10.1038/s41467-017-02044-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 11/03/2017] [Indexed: 12/17/2022] Open
Abstract
Lysosomal integral membrane protein-2 (LIMP-2/SCARB2) contributes to endosomal and lysosomal function. LIMP-2 deficiency is associated with neurological abnormalities and kidney failure and, as an acid glucocerebrosidase receptor, impacts Gaucher and Parkinson's diseases. Here we report a crystal structure of a LIMP-2 luminal domain dimer with bound cholesterol and phosphatidylcholine. Binding of these lipids alters LIMP-2 from functioning as a glucocerebrosidase-binding monomer toward a dimeric state that preferentially binds anionic phosphatidylserine over neutral phosphatidylcholine. In cellular uptake experiments, LIMP-2 facilitates transport of phospholipids into murine fibroblasts, with a strong substrate preference for phosphatidylserine. Taken together, these biophysical and cellular studies define the structural basis and functional importance of a form of LIMP-2 for lipid trafficking. We propose a model whereby switching between monomeric and dimeric forms allows LIMP-2 to engage distinct binding partners, a mechanism that may be shared by SR-BI and CD36, scavenger receptor proteins highly homologous to LIMP-2.
Collapse
Affiliation(s)
- Karen S Conrad
- Medicinal Sciences, Pfizer Worldwide R&D, Eastern Point Road, Groton, CT, 06340, USA
| | - Ting-Wen Cheng
- Neuroscience Research Unit, Pfizer Worldwide R&D, 610 Main Street, Cambridge, MA, 02139, USA
| | - Daniel Ysselstein
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Saskia Heybrock
- Biochemical Institute, Christian-Albrechts University Kiel, Olshausenstrasse 40, D-24098, Kiel, Germany
| | - Lise R Hoth
- Medicinal Sciences, Pfizer Worldwide R&D, Eastern Point Road, Groton, CT, 06340, USA
| | - Boris A Chrunyk
- Medicinal Sciences, Pfizer Worldwide R&D, Eastern Point Road, Groton, CT, 06340, USA
| | - Christopher W Am Ende
- Medicinal Sciences, Pfizer Worldwide R&D, Eastern Point Road, Groton, CT, 06340, USA
| | - Dimitri Krainc
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Michael Schwake
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA
| | - Paul Saftig
- Biochemical Institute, Christian-Albrechts University Kiel, Olshausenstrasse 40, D-24098, Kiel, Germany
| | - Shenping Liu
- Medicinal Sciences, Pfizer Worldwide R&D, Eastern Point Road, Groton, CT, 06340, USA.
| | - Xiayang Qiu
- Medicinal Sciences, Pfizer Worldwide R&D, Eastern Point Road, Groton, CT, 06340, USA.
| | - Michael D Ehlers
- Neuroscience Research Unit, Pfizer Worldwide R&D, 610 Main Street, Cambridge, MA, 02139, USA
- Biogen, 225 Binney St., Cambridge, MA, 02142, USA
| |
Collapse
|
5
|
CD36 in chronic kidney disease: novel insights and therapeutic opportunities. Nat Rev Nephrol 2017; 13:769-781. [DOI: 10.1038/nrneph.2017.126] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
6
|
Okuda K, Tong M, Dempsey B, Moore KJ, Gazzinelli RT, Silverman N. Leishmania amazonensis Engages CD36 to Drive Parasitophorous Vacuole Maturation. PLoS Pathog 2016; 12:e1005669. [PMID: 27280707 PMCID: PMC4900624 DOI: 10.1371/journal.ppat.1005669] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 05/10/2016] [Indexed: 11/19/2022] Open
Abstract
Leishmania amastigotes manipulate the activity of macrophages to favor their own success. However, very little is known about the role of innate recognition and signaling triggered by amastigotes in this host-parasite interaction. In this work we developed a new infection model in adult Drosophila to take advantage of its superior genetic resources to identify novel host factors limiting Leishmania amazonensis infection. The model is based on the capacity of macrophage-like cells, plasmatocytes, to phagocytose and control the proliferation of parasites injected into adult flies. Using this model, we screened a collection of RNAi-expressing flies for anti-Leishmania defense factors. Notably, we found three CD36-like scavenger receptors that were important for defending against Leishmania infection. Mechanistic studies in mouse macrophages showed that CD36 accumulates specifically at sites where the parasite contacts the parasitophorous vacuole membrane. Furthermore, CD36-deficient macrophages were defective in the formation of the large parasitophorous vacuole typical of L. amazonensis infection, a phenotype caused by inefficient fusion with late endosomes and/or lysosomes. These data identify an unprecedented role for CD36 in the biogenesis of the parasitophorous vacuole and further highlight the utility of Drosophila as a model system for dissecting innate immune responses to infection.
Collapse
Affiliation(s)
- Kendi Okuda
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (KO); (NS)
| | - Mei Tong
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Brian Dempsey
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Kathryn J. Moore
- Department of Medicine, New York University School of Medicine, Langone Medical Center, New York, New York, United States of America
| | - Ricardo T. Gazzinelli
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Neal Silverman
- Division of Infectious Diseases & Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (KO); (NS)
| |
Collapse
|
7
|
Lin D, Chun TH, Kang L. Adipose extracellular matrix remodelling in obesity and insulin resistance. Biochem Pharmacol 2016; 119:8-16. [PMID: 27179976 DOI: 10.1016/j.bcp.2016.05.005] [Citation(s) in RCA: 144] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/10/2016] [Indexed: 12/15/2022]
Abstract
The extracellular matrix (ECM) of adipose tissues undergoes constant remodelling to allow adipocytes and their precursor cells to change cell shape and function in adaptation to nutritional cues. Abnormal accumulation of ECM components and their modifiers in adipose tissues has been recently demonstrated to cause obesity-associated insulin resistance, a hallmark of type 2 diabetes. Integrins and other ECM receptors (e.g. CD44) that are expressed in adipose tissues have been shown to regulate insulin sensitivity. It is well understood that a hypoxic response is observed in adipose tissue expansion during obesity progression and that hypoxic response accelerates fibrosis and inflammation in white adipose tissues. The expansion of adipose tissues should require angiogenesis; however, the excess deposition of ECM limits the angiogenic response of white adipose tissues in obesity. While recent studies have focused on the metabolic consequences and the mechanisms of adipose tissue expansion and remodelling, little attention has been paid to the role played by the interaction between peri-adipocyte ECM and their cognate cell surface receptors. This review will address what is currently known about the roles played by adipose ECM, their modifiers, and ECM receptors in obesity and insulin resistance. Understanding how excess ECM deposition in the adipose tissue deteriorates insulin sensitivity would provide us hints to develop a new therapeutic strategy for the treatment of insulin resistance and type 2 diabetes.
Collapse
Affiliation(s)
- De Lin
- Division of Cancer Research, School of Medicine, University of Dundee, Dundee, UK
| | - Tae-Hwa Chun
- Division of Metabolism, Endocrinology & Diabetes (MEND), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
| | - Li Kang
- Division of Molecular and Clinical Medicine, School of Medicine, University of Dundee, Dundee, UK.
| |
Collapse
|
8
|
Fairaq A, Goc A, Artham S, Sabbineni H, Somanath PR. TNFα induces inflammatory stress response in microvascular endothelial cells via Akt- and P38 MAP kinase-mediated thrombospondin-1 expression. Mol Cell Biochem 2015; 406:227-36. [PMID: 25963668 PMCID: PMC4504829 DOI: 10.1007/s11010-015-2440-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 05/06/2015] [Indexed: 12/14/2022]
Abstract
Tumor necrosis factor-α (TNFα) and thrombospondin-1 (TSP-1) are well-known mediators of inflammation. However, a causal relationship between TNFα stimuli and TSP-1 expression in endothelial cell stress, and the underlying mechanisms has not yet been investigated. In our study, human microvascular endothelial cells (hMEC) were treated with TNFα and analyzed for endothelial dysfunction, TSP-1 expression, and associated mechanisms. TNFα treatment induced a dose-dependent increase in TSP-1 expression in hMEC associated with increased endothelial permeability, apoptosis, and reduced proliferation. Whereas TNFα activated Akt, ERK, and P38 mitogen-activated protein kinase (P38 MAPK) simultaneously in hMEC, inhibitors of Akt and P38 MAPK, but not ERK blunted TNFα-induced TSP-1 expression. Silencing of NFκB gene had no significant effect on TNFα-induced TSP-1 expression. Our study demonstrates the novel role of TNFα in inducing inflammatory stress response in hMEC through Akt- and P38 MAPK-mediated expression of TSP-1, independent of NFκB signaling.
Collapse
Affiliation(s)
- Arwa Fairaq
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia and Charlie Norwood VA Medical center, Augusta, GA
| | - Anna Goc
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia and Charlie Norwood VA Medical center, Augusta, GA
| | - Sandeep Artham
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia and Charlie Norwood VA Medical center, Augusta, GA
| | - Harika Sabbineni
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia and Charlie Norwood VA Medical center, Augusta, GA
| | - Payaningal R. Somanath
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia and Charlie Norwood VA Medical center, Augusta, GA
- Department of Medicine, Vascular Biology Center and Cancer Center, Georgia Regents University, Augusta, GA
| |
Collapse
|
9
|
van Oort MM, Drost R, Janβen L, Van Doorn JM, Kerver J, Van der Horst DJ, Luiken JJFP, Rodenburg KCW. Each of the four intracellular cysteines of CD36 is essential for insulin- or AMP-activated protein kinase-induced CD36 translocation. Arch Physiol Biochem 2014; 120:40-9. [PMID: 24377880 DOI: 10.3109/13813455.2013.876049] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Stimulation of cellular fatty acid uptake by induction of insulin signalling or AMP-kinase (AMPK) activation is due to translocation of the fatty acid-transporter CD36 from intracellular stores to the plasma membrane (PM). For investigating the role of the four Cys-residues within CD36's cytoplasmic tails in CD36 translocation, we constructed CHO-cells expressing CD36 mutants in which all four, two, or one of the intracellular Cys were replaced by Ser. Intracellular and PM localization of all mutants was similar to wild-type CD36 (CD36wt). Hence, the four Cys do not regulate sub-cellular CD36 localization. However, in contrast to CD36wt, insulin or AMPK activation failed to induce translocation of any of the mutants, indicating that all four intracellular Cys residues are essential for CD36 translocation. The mechanism of defective translocation of mutant CD36 is unknown, but appears not due to loss of S-palmitoylation of the cytoplasmic tails or to aberrant oligomerization of the mutants.
Collapse
Affiliation(s)
- Masja M van Oort
- Division of Endocrinology and Metabolism, Department of Biology and Institute of Biomembranes, Utrecht University , NL-3584 CH Utrecht , The Netherlands and
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Wilhelmsen P, Kjær J, Thomsen KL, Nielsen CT, Dige A, Maniecki MB, Heegaard N, Grønbæk H, Dahlerup J, Handberg A. Elevated platelet expression of CD36 may contribute to increased risk of thrombo-embolism in active inflammatory bowel disease. Arch Physiol Biochem 2013; 119:202-8. [PMID: 23862574 DOI: 10.3109/13813455.2013.808671] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
CONTEXT Inflammatory bowel disease (IBD) induces increased risk of thrombo-embolism. CD36 is involved in platelet activation, glucose metabolism and inflammation. OBJECTIVE The relationship between CD36 expression on platelets and monocytes, plasma sCD36, and CD36-positive platelet-derived microparticles (PDMPs) and inflammation in both active IBD and after one week of anti-tumour necrosis alpha antibody (anti-TNF) treatment was investigated. MATERIAL AND METHODS Patients with exacerbation of Crohn's disease (n = 8) or ulcerative colitis (n = 5) and 13 healthy controls were enrolled. Seven patients underwent anti-TNF treatment for one week. Platelet, monocyte, and PDMP-CD36 were measured by flow-cytometry. RESULTS Platelet CD36 expression was 34% higher in patients, and correlated with insulin resistance and fasting glucose. sCD36 was 37% lower and restored after anti-TNF treatment. CONCLUSION Elevated platelet CD36 expression may contribute to increased risk of thrombo-embolism in active IBD. This may not entirely be attributed to inflammation and secondary insulin resistance may play a role.
Collapse
Affiliation(s)
- Peter Wilhelmsen
- Department of Clinical Biochemistry, Aarhus University Hospital , Aarhus , Denmark
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Henkin J, Volpert OV. Therapies using anti-angiogenic peptide mimetics of thrombospondin-1. Expert Opin Ther Targets 2011; 15:1369-86. [PMID: 22136063 DOI: 10.1517/14728222.2011.640319] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
INTRODUCTION The role of hrombospondin-1 (TSP1) as a major endogenous angiogenesis inhibitor has been confirmed by numerous studies and subsequent mechanistic discoveries. It has yielded a new class of potential drugs against cancer and other angiogenesis-driven diseases. AREAS COVERED An overview of TSP1 functions and molecular mechanisms, including regulation and signaling. Functions in endothelial and non-endothelial cells, with emphasis on the role of TSP1 in the regulation of angiogenesis and inflammation. The utility of duplicating these activities for drug discovery. Past and current literature on endogenous TSP1 and its role in the progression of cancer and non-cancerous pathological conditions is summarized, as well as the research undertaken to identify and optimize short bioactive peptides derived from the two TSP1 anti-angiogenic domains, which bind CD47 and CD36 cell surface receptors. Lastly, there is an overview of the efficacy of some of these peptides in pre-clinical and clinical models of angiogenesis-dependent disease. EXPERT OPINION It is concluded that TSP1-derived peptides and peptide mimetics hold great promise as future agents for the treatment of cancer and other diseases driven by excessive angiogenesis. They may fulfill unmet medical needs including neovascular ocular disease and the diseases of the female reproductive tract including ovarian cancer.
Collapse
Affiliation(s)
- Jack Henkin
- Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | | |
Collapse
|
12
|
Trujillo G, Zhang J, Habiel DM, Ge L, Ramadass M, Ghebrehiwet B, Kew RR. Cofactor regulation of C5a chemotactic activity in physiological fluids. Requirement for the vitamin D binding protein, thrombospondin-1 and its receptors. Mol Immunol 2011; 49:495-503. [PMID: 22014686 DOI: 10.1016/j.molimm.2011.09.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 09/15/2011] [Accepted: 09/28/2011] [Indexed: 12/15/2022]
Abstract
Factors in physiological fluids that regulate the chemotactic activity of complement activation peptides C5a and C5a des Arg are not well understood. The vitamin D binding protein (DBP) has been shown to significantly enhance chemotaxis to C5a/C5a des Arg. More recently, platelet-derived thrombospondin-1 (TSP-1) has been shown to facilitate the augmentation of C5a-induced chemotaxis by DBP. The objective of this study was to better characterize these chemotactic cofactors and investigate the role that cell surface TSP-1 receptors CD36 and CD47 may play in this process. The chemotactic activity in C-activated normal serum, citrated plasma, DBP-depleted serum or C5 depleted serum was determined for both normal human neutrophils and U937 cell line transfected with the C5a receptor (U937-C5aR). In addition, levels of C5a des Arg, DBP and TSP-1 in these fluids were measured by RIA or ELISA. Results show that there is a clear hierarchy with C5a being the essential primary signal (DBP or TSP-1 will not function in the absence of C5a), DBP the necessary cofactor and TSP-1 a dependent tertiary factor, since it cannot function to enhance chemotaxis to C5a without DBP. Measurement of the C5a-induced intracellular calcium flux confirmed the same hierarchy observed with chemotaxis. Moreover, analysis of bronchoalveolar lavage fluid (BALF) from patients with the adult respiratory distress syndrome (ARDS) demonstrated that C5a-dependent chemotactic activity is significantly decreased after anti-DBP treatment. Finally, results show that TSP-1 utilizes cell surface receptors CD36 and CD47 to augment chemotaxis, but DBP does not bind to TSP-1, CD36 or CD47. The results clearly demonstrate that C5a/C5a des Arg needs both DBP and TSP-1 for maximal chemotactic activity and suggest that the regulation of C5a chemotactic activity in physiological fluids is more complex than previously thought.
Collapse
Affiliation(s)
- Glenda Trujillo
- Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA
| | | | | | | | | | | | | |
Collapse
|
13
|
Jaqaman K, Kuwata H, Touret N, Collins R, Trimble WS, Danuser G, Grinstein S. Cytoskeletal control of CD36 diffusion promotes its receptor and signaling function. Cell 2011; 146:593-606. [PMID: 21854984 DOI: 10.1016/j.cell.2011.06.049] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 04/28/2011] [Accepted: 06/21/2011] [Indexed: 01/21/2023]
Abstract
The mechanisms that govern receptor coalescence into functional clusters--often a critical step in their stimulation by ligand--are poorly understood. We used single-molecule tracking to investigate the dynamics of CD36, a clustering-responsive receptor that mediates oxidized LDL uptake by macrophages. We found that CD36 motion in the membrane was spatially structured by the cortical cytoskeleton. A subpopulation of receptors diffused within linear confinement regions whose unique geometry simultaneously facilitated freedom of movement along one axis while increasing the effective receptor density. Co-confinement within troughs enhanced the probability of collisions between unligated receptors and promoted their clustering. Cytoskeleton perturbations that inhibited diffusion in linear confinement regions reduced receptor clustering in the absence of ligand and, following ligand addition, suppressed CD36-mediated signaling and internalization. These observations demonstrate a role for the cytoskeleton in controlling signal transduction by structuring receptor diffusion within membrane regions that increase their collision frequency.
Collapse
Affiliation(s)
- Khuloud Jaqaman
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | | | | | | | | | | | | |
Collapse
|
14
|
Thrombospondin-1: multiple paths to inflammation. Mediators Inflamm 2011; 2011:296069. [PMID: 21765615 PMCID: PMC3134184 DOI: 10.1155/2011/296069] [Citation(s) in RCA: 188] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 04/06/2011] [Accepted: 05/05/2011] [Indexed: 12/31/2022] Open
Abstract
Inflammation is a defensive process against tissue injury. Once this self-protective strategy is initiated, an effective resolution of the process is crucial to avoid major and unnecessary tissue damage. If the underlying event inducing inflammation is not addressed and homeostasis is not restored, this process can become chronic and lead to angiogenesis and carcinogenesis. Thrombospondin-1 (TSP-1) is a matricellular protein involved in angiogenesis, cancer, and inflammation. The effects of TSP-1 have been studied in many preclinical tumor models, and mimetic peptides are being tested in cancer clinical trials. However, the molecular mechanisms explaining its role in inflammatory processes are not well understood. This paper will discuss the role of TSP-1 in inflammation and its interaction with key receptors that may explain its functions in that process. Recent literature will be reviewed showing novel mechanisms by which this multifaceted protein could modulate the inflammatory process and impact its resolution.
Collapse
|
15
|
Papale GA, Hanson PJ, Sahoo D. Extracellular disulfide bonds support scavenger receptor class B type I-mediated cholesterol transport. Biochemistry 2011; 50:6245-54. [PMID: 21675794 DOI: 10.1021/bi2005625] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Scavenger receptor class B type I (SR-BI) binds high-density lipoprotein (HDL) and mediates the selective uptake of cholesteryl esters (CE). Although the extracellular domain of SR-BI is critical for function, the structural characteristics of this region remain elusive. Using sulfhydryl labeling strategies, we report the novel finding that all six cysteine (Cys) residues in the extracellular domain of SR-BI are involved in disulfide bond formation that is intramolecular by nature. We hypothesized that an SR-BI conformation stabilized by extracellular disulfide bonds is a prerequisite for SR-BI-mediated cholesterol transport. Thus, single-Cys mutant SR-BI receptors (C251S-, C280S-, C321S-, C323S-, C334S-, and C384S-SR-BI), as well as Cys-less SR-BI, a mutant SR-BI receptor void of all Cys residues, were created, and plasma membrane localization was confirmed. Functional assays revealed that C280S-, C321S-, C323S-, and C334S-SR-BI and Cys-less SR-BI mutant receptors displayed weakened HDL binding and subsequent selective uptake of HDL-CE. However, only C323S-SR-BI and Cys-less SR-BI were unable to mediate wild-type levels of efflux of free cholesterol (FC) to HDL. None of the Cys mutations disrupted SR-BI's ability to redistribute plasma membrane FC. Taken together, the intramolecular disulfide bonds in the extracellular domain of SR-BI appear to maintain the receptor in a conformation integral to its cholesterol transport functions.
Collapse
Affiliation(s)
- Gabriella A Papale
- Department of Medicine, Division of Endocrinology, Metabolism and Clinical Nutrition, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States
| | | | | |
Collapse
|
16
|
Truong TQ, Aubin D, Falstrault L, Brodeur MR, Brissette L. SR-BI, CD36, and caveolin-1 contribute positively to cholesterol efflux in hepatic cells. Cell Biochem Funct 2010; 28:480-9. [DOI: 10.1002/cbf.1680] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
17
|
Xu Y, Wang J, Bao Y, Jiang W, Zuo L, Song D, Hong B, Si S. Identification of two antagonists of the scavenger receptor CD36 using a high-throughput screening model. Anal Biochem 2010; 400:207-12. [DOI: 10.1016/j.ab.2010.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 02/04/2010] [Accepted: 02/04/2010] [Indexed: 10/19/2022]
|
18
|
Apostolov EO, Shah SV, Ray D, Basnakian AG. Scavenger receptors of endothelial cells mediate the uptake and cellular proatherogenic effects of carbamylated LDL. Arterioscler Thromb Vasc Biol 2009; 29:1622-30. [PMID: 19696406 DOI: 10.1161/atvbaha.109.189795] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Carbamylated LDL (cLDL) has been recently shown to have robust proatherogenic effects on human endothelial cells in vitro, suggesting cLDL may have a significant role in atherosclerosis in uremia. The current study was designed to determine which receptors are used by cLDL and thus cause the proatherogenic effects. METHODS AND RESULTS In ex vivo or in vitro models as well as in intact animals, administration of cLDL was associated with endothelial internalization of cLDL and subendothelial translocation (transcytosis). In vitro recombinant LOX-1 and SREC-1 receptors showed the greatest cLDL binding. However, pretreatment of the endothelial cells with specific inhibiting antibodies demonstrated that cLDL binds mainly to LOX-1 and CD36 receptors. The transcytosis was dependent on SR-A1, SREC-1, and CD36 receptors whereas LOX-1 receptor was not involved. The cytotoxicity was mediated by several studied scavenger receptors, but cLDL-induced monocyte adhesion depended only on LOX-1. The cLDL-induced synthesis of LOX-1 protein significantly contributed to both cytotoxicity and accelerated monocyte adhesion to endothelial cells. CONCLUSIONS Our data suggest that cLDL uses a unique pattern of scavenger receptors. They show that LOX-1 receptor, and partially CD36, SREC-1, and SR-A1 receptors, are essential for the proatherogenic effects of cLDL on human endothelial cells.
Collapse
Affiliation(s)
- Eugene O Apostolov
- Department of Pharmacology & Toxicology, University of Arkansas for Medical Sciences, 4301 W Markham St, Little Rock, AR 72205, USA
| | | | | | | |
Collapse
|
19
|
Ehehalt R, Sparla R, Kulaksiz H, Herrmann T, Füllekrug J, Stremmel W. Uptake of long chain fatty acids is regulated by dynamic interaction of FAT/CD36 with cholesterol/sphingolipid enriched microdomains (lipid rafts). BMC Cell Biol 2008; 9:45. [PMID: 18700980 PMCID: PMC2533316 DOI: 10.1186/1471-2121-9-45] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Accepted: 08/13/2008] [Indexed: 11/10/2022] Open
Abstract
Background Mechanisms of long chain fatty acid uptake across the plasma membrane are important targets in treatment of many human diseases like obesity or hepatic steatosis. Long chain fatty acid translocation is achieved by a concert of co-existing mechanisms. These lipids can passively diffuse, but certain membrane proteins can also accelerate the transport. However, we now can provide further evidence that not only proteins but also lipid microdomains play an important part in the regulation of the facilitated uptake process. Methods Dynamic association of FAT/CD36 a candidate fatty acid transporter with lipid rafts was analysed by isolation of detergent resistant membranes (DRMs) and by clustering of lipid rafts with antibodies on living cells. Lipid raft integrity was modulated by cholesterol depletion using methyl-β-cyclodextrin and sphingolipid depletion using myriocin and sphingomyelinase. Functional analyses were performed using an [3H]-oleate uptake assay. Results Overexpression of FAT/CD36 and FATP4 increased long chain fatty acid uptake. The uptake of long chain fatty acids was cholesterol and sphingolipid dependent. Floating experiments showed that there are two pools of FAT/CD36, one found in DRMs and another outside of these domains. FAT/CD36 co-localized with the lipid raft marker PLAP in antibody-clustered domains at the plasma membrane and segregated away from the non-raft marker GFP-TMD. Antibody cross-linking increased DRM association of FAT/CD36 and accelerated the overall fatty acid uptake in a cholesterol dependent manner. Another candidate transporter, FATP4, was neither present in DRMs nor co-localized with FAT/CD36 at the plasma membrane. Conclusion Our observations suggest the existence of two pools of FAT/CD36 within cellular membranes. As increased raft association of FAT/CD36 leads to an increased fatty acid uptake, dynamic association of FAT/CD36 with lipid rafts might regulate the process. There is no direct interaction of FATP4 with lipid rafts or raft associated FAT/CD36. Thus, lipid rafts have to be considered as targets for the treatment of lipid disorders.
Collapse
Affiliation(s)
- Robert Ehehalt
- Department of Gastroenterology, University Hospital Heidelberg, INF 410, 69120 Heidelberg, Germany.
| | | | | | | | | | | |
Collapse
|
20
|
Martin CA, Longman E, Wooding C, Hoosdally SJ, Ali S, Aitman TJ, Gutmann DAP, Freemont PS, Byrne B, Linton KJ. Cd36, a class B scavenger receptor, functions as a monomer to bind acetylated and oxidized low-density lipoproteins. Protein Sci 2007; 16:2531-41. [PMID: 17905828 PMCID: PMC2211707 DOI: 10.1110/ps.073007207] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cd36 is a small-molecular-weight integral membrane protein expressed in a diverse, but select, range of cell types. It has an equally diverse range of ligands and physiological functions, which has implicated Cd36 in a number of diseases including insulin resistance, diabetes, and, most notably, atherosclerosis. The protein is reported to reside in detergent-resistant microdomains within the plasma membrane and to form homo- and hetero-intermolecular interactions. These data suggest that this class B scavenger receptor may gain functionality for ligand binding, and/or ligand internalization, by formation of protein complexes at the cell surface. Here, we have overexpressed Cd36 in insect cells, purified the recombinant protein to homogeneity, and analyzed its stability and solubility in a variety of nonionic and zwitterionic detergents. Octylglucoside conferred the greatest degree of stability, and by analytical ultracentrifugation we show that the protein is monomeric. A solid-phase ligand-binding assay demonstrated that the purified monomeric protein retains high affinity for acetylated and oxidized low-density lipoproteins. Therefore, no accessory proteins are required for interaction with ligand, and binding is a property of the monomeric fold of the protein. Thus, the highly purified and functional Cd36 should be suitable for crystallization in octylglucoside, and the in vitro ligand-binding assay represents a promising screen for identification of bioactive molecules targeting atherogenesis at the level of ligand binding.
Collapse
Affiliation(s)
- Catherine A Martin
- MRC Clinical Sciences Centre, Imperial College, Hammersmith Hospital Campus, London, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Ehehalt R, Füllekrug J, Pohl J, Ring A, Herrmann T, Stremmel W. Translocation of long chain fatty acids across the plasma membrane--lipid rafts and fatty acid transport proteins. Mol Cell Biochem 2006; 284:135-40. [PMID: 16477381 DOI: 10.1007/s11010-005-9034-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Accepted: 10/10/2005] [Indexed: 12/20/2022]
Abstract
Translocation of long chain fatty acids across the plasma membrane is achieved by a concert of co-existing mechanisms. These lipids can passively diffuse, but transport can also be accelerated by certain membrane proteins as well as lipid rafts. Lipid rafts are dynamic assemblies of proteins and lipids, that float freely within the two dimensional matrix of the membrane bilayer. They are receiving increasing attention as devices that regulate membrane function in vivo and play an important role in membrane trafficking and signal transduction. In this review we will discuss how lipid rafts might be involved in the uptake process and how the candidate proteins for fatty acid uptake FAT/CD36 and the FATP proteins interact with these domains. We will also discuss the functional role of FATPs in general. To our understanding FATPs are indirectly involved in the translocation process across the plasma membrane by providing long chain fatty acid synthetase activity.
Collapse
Affiliation(s)
- Robert Ehehalt
- Department of Internal Medicine IV, Gastroenterology, University of Heidelberg, Heidelberg, Germany.
| | | | | | | | | | | |
Collapse
|
22
|
Rhainds D, Brissette L. The role of scavenger receptor class B type I (SR-BI) in lipid trafficking. defining the rules for lipid traders. Int J Biochem Cell Biol 2004; 36:39-77. [PMID: 14592533 DOI: 10.1016/s1357-2725(03)00173-0] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The scavenger receptor class B type I (SR-BI) is a 509-amino acid, 82 kDa glycoprotein, with two cytoplasmic C- and N-terminal domains separated by a large extracellular domain. The aim of this review is to define the role of SR-BI as a lipoprotein receptor responsible for selective uptake of cholesteryl esters (CE) from high density lipoprotein (HDL) and low density lipoprotein (LDL) and free cholesterol (FC) efflux to lipoprotein acceptors. These activities depend on lipoprotein binding to its extracellular domain and subsequent lipid exchange at the plasma membrane. CE selective uptake supplies cholesterol to liver and steroidogenic tissues, for biliary cholesterol secretion and steroid hormone synthesis. Genetically modified mice have confirmed SR-BI's major role in tissue cholesterol uptake and in reverse cholesterol transport, i.e. cholesterol turnover. Accordingly, cellular cholesterol level, estrogens and trophic hormones regulate SR-BI expression by both transcriptional and post-transcriptional mechanisms. Importantly, mouse SR-BI overexpression has both corrective and preventive effects on atherosclerosis. Human SR-BI has very similar tissue distribution, binding properties and lipid transfer activities compared to rodent SR-BI. However, human plasma has most of its cholesterol in LDL. Thus, there is considerable interest to develop anti-atherogenic strategies involving human SR-BI-mediated increases in reverse cholesterol transport through HDL and/or LDL.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Biological Transport, Active
- CD36 Antigens
- Cell Membrane/chemistry
- Cell Membrane/genetics
- Cell Membrane/metabolism
- Cell Membrane/physiology
- Humans
- Lipid Metabolism
- Lipoproteins/metabolism
- Models, Biological
- Promoter Regions, Genetic
- Protein Structure, Tertiary
- Receptors, Immunologic/chemistry
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Receptors, Immunologic/physiology
- Receptors, Scavenger
- Scavenger Receptors, Class B
- Tissue Distribution
Collapse
Affiliation(s)
- David Rhainds
- Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montreal, Que., Canada H3C 3P8.
| | | |
Collapse
|
23
|
Gruarin P, Primo L, Ferrandi C, Bussolino F, Tandon NN, Arese P, Ulliers D, Alessio M. Cytoadherence of Plasmodium falciparum-infected erythrocytes is mediated by a redox-dependent conformational fraction of CD36. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:6510-7. [PMID: 11714819 DOI: 10.4049/jimmunol.167.11.6510] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The adherence of Plasmodium falciparum-infected RBC (IRBC) to postcapillary venular endothelium is an important determinant of the pathogenesis of severe malaria complications. Cytoadherence of IRBC to endothelial cells involves specific receptor/ligand interactions. The glycoprotein CD36 expressed on endothelial cells is the major receptor involved in this interaction. Treatment of CD36-expressing cells with reducing agents, such as DTT and N-acetylcysteine, was followed by CD36 conformational change monitorable by the appearance of the Mo91 mAb epitope. Only a fraction of the surface expressed CD36 molecules became Mo91 positive, suggesting the presence of two subpopulations of molecules with different sensitivities to reduction. The Mo91 epitope has been localized on a peptide (residues 260-279) of the C-terminal, cysteine-rich region of CD36. Treatment with reducing agents inhibited the CD36-dependent cytoadherence of IRBC to CD36-expressing cells and dissolved pre-existent CD36-mediated IRBC/CD36-expressing cell aggregates. CD36 reduction did not impair the functionality of CD36, since the reactivity of other anti-CD36 mAbs as well as the binding of oxidized low density lipoprotein, a CD36 ligand, were maintained. The modifications induced by reduction were reversible. After 14 h CD36 was reoxidized, the cells did not express the Mo91 epitope, and cytoadherence to IRBC was restored. The results indicate that IRBCs bind only to a redox-modulated fraction of CD36 molecules expressed on the cell surface. The present data indicate the therapeutic potential of reducing agents, such as the nontoxic drug N-acetylcysteine, to prevent or treat malaria complications due to IRBC cytoadhesion.
Collapse
Affiliation(s)
- P Gruarin
- DIBIT, San Raffaele Scientific Institute, Milan, Italy
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Finnemann SC, Silverstein RL. Differential roles of CD36 and alphavbeta5 integrin in photoreceptor phagocytosis by the retinal pigment epithelium. J Exp Med 2001; 194:1289-98. [PMID: 11696594 PMCID: PMC2195987 DOI: 10.1084/jem.194.9.1289] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Retinal pigment epithelial (RPE) cells employ alphavbeta5 integrin and CD36 receptors to phagocytose photoreceptor outer segment fragments (OS). We explored special properties of RPE phagocytosis to identify the contribution of CD36 to RPE phagocytosis measuring effects of CD36 antibodies on OS binding and internalization kinetics. Early, CD36 antibodies had no effect on OS binding or internalization. Both control and CD36 antibody treated RPE initiated internalization approximately 2 hours after OS challenge. Later, bivalent CD36 IgG accelerated OS engulfment while monovalent Fab fragments inhibited engulfment. Cross-linking Fab fragments restored the accelerating activity of intact IgG. Strikingly, antibodies were effective even if added to OS already bound by RPE. alphavbeta5 blocking antibody reduced OS binding equally well in the presence of CD36 antibodies but CD36 antibodies accelerated internalization of remaining bound OS. Furthermore, CD36 ligation at either apical or basal RPE surface partially substituted for soluble factors that are required for internalization but not for binding of OS at the RPE apical surface. Our results demonstrate that CD36 ligation is necessary and sufficient to activate the OS internalization mechanism of RPE. They suggest that CD36 acts as a signaling molecule in postbinding steps of RPE phagocytosis independently of the OS binding receptor alphavbeta5 integrin.
Collapse
Affiliation(s)
- S C Finnemann
- Margaret M. Dyson Vision Research Institute, Department of Ophthalmology and Department of Cell Biology, Weill Medical College of Cornell University, New York, NY 10021, USA.
| | | |
Collapse
|
25
|
Abstract
Thrombospondin-1 (TSP-1) is a matricellular protein that regulates cellular phenotype during tissue genesis and repair. It acts as a molecular facilitator by bringing together cytokines, growth factors, matrix components, membrane receptors and extracellular proteases. TSP-1 binds to a wide variety of integrin and non-integrin cell surface receptors. The binding sites for these receptors on TSP-1 are dispersed throughout the molecule, with most domains binding multiple receptors. In some cases, TSP-1 binds to multiple receptors concurrently, and recent data indicate that there is cross-talk between the receptor systems. Thus, TSP-1 may function to direct the clustering of receptors to specialized domains for adhesion and signal transduction.
Collapse
Affiliation(s)
- H Chen
- Division of Cancer Biology and Angiogenesis, Department of Pathology, Beth Israel Deaconess Medical Center, Research North, Rm. 270C, 99 Brookline Avenue, Boston, MA 02215, USA
| | | | | |
Collapse
|
26
|
Schultz DR, Arnold PI, Jy W, Valant PA, Gruber J, Ahn YS, Mao FW, Mao WW, Horstman LL. Anti-CD36 autoantibodies in thrombotic thrombocytopenic purpura and other thrombotic disorders: identification of an 85 kD form of CD36 as a target antigen. Br J Haematol 1998; 103:849-57. [PMID: 9858245 DOI: 10.1046/j.1365-2141.1998.01070.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The presence of anti-CD36 antibodies in plasma of patients with thrombotic thrombocytopenic purpura (TTP), idiopathic thrombocytopenic purpura (ITP), and heparin-induced thrombocytopenia without/with thrombosis (HIT/HITT) has been examined by immunoblots, and a monoclonal antibody capture assay, the platelet-associated IgG characterization assay (PAICA). Results with PAICA showed that 73% (8/11) of patients with TTP were positive, and 71% (10/14) by immunoblots. With ITP, 20% (6/30) were positive by PAICA and 19% (3/16) by immunoblots; HIT, 30% (3/10) were positive by PAICA and 60% (6/10) by immunoblot; HITT, 50% (2/4) by PAICA and 100% (4/4) by immunoblot. Purification of CD36 by fast protein liquid chromatography (FPLC) from Triton X-100 extracts of normal platelet membranes resulted in the isolation of two different forms: the classic 88 kD form, and a second, lighter 85 kD form. Our data indicated that the patients' plasma autoantibodies reacted strongly with the 85 kD form. Conventional monoclonal and polyclonal antisera produced to the 88 kD form reacted strongly with the 88 kD form but weakly with the 85 kD form. These results confirm the possible importance of anti-CD36 antibodies in the pathophysiology of TTP and other thrombocytopenias and demonstrate the presence of a previously unrecognized target antigen for these antibodies.
Collapse
Affiliation(s)
- D R Schultz
- Department of Medicine, University of Miami School of Medicine, Florida 33101, USA
| | | | | | | | | | | | | | | | | |
Collapse
|