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Kaynak A, Davis HW, Kogan AB, Lee JH, Narmoneva DA, Qi X. Phosphatidylserine: The Unique Dual-Role Biomarker for Cancer Imaging and Therapy. Cancers (Basel) 2022; 14:2536. [PMID: 35626139 PMCID: PMC9139557 DOI: 10.3390/cancers14102536] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 05/06/2022] [Accepted: 05/17/2022] [Indexed: 01/27/2023] Open
Abstract
Cancer is among the leading causes of death worldwide. In recent years, many cancer-associated biomarkers have been identified that are used for cancer diagnosis, prognosis, screening, and early detection, as well as for predicting and monitoring carcinogenesis and therapeutic effectiveness. Phosphatidylserine (PS) is a negatively charged phospholipid which is predominantly located in the inner leaflet of the cell membrane. In many cancer cells, PS externalizes to the outer cell membrane, a process regulated by calcium-dependent flippases and scramblases. Saposin C coupled with dioleoylphosphatidylserine (SapC-DOPS) nanovesicle (BXQ-350) and bavituximab, (Tarvacin, human-mouse chimeric monoclonal antibodies) are cell surface PS-targeting drugs being tested in clinical trial for treating a variety of cancers. Additionally, a number of other PS-selective agents have been used to trigger cytotoxicity in tumor-associated endothelial cells or cancer cells in pre-clinical studies. Recent studies have demonstrated that upregulation of surface PS exposure by chemodrugs, radiation, and external electric fields can be used as a novel approach to sensitize cancer cells to PS-targeting anticancer drugs. The objectives of this review are to provide an overview of a unique dual-role of PS as a biomarker/target for cancer imaging and therapy, and to discuss PS-based anticancer strategies that are currently under active development.
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Affiliation(s)
- Ahmet Kaynak
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221, USA; (A.K.); (J.-H.L.); (D.A.N.)
| | - Harold W. Davis
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA;
| | - Andrei B. Kogan
- Physics Department, University of Cincinnati, Cincinnati, OH 45221, USA;
| | - Jing-Huei Lee
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221, USA; (A.K.); (J.-H.L.); (D.A.N.)
| | - Daria A. Narmoneva
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221, USA; (A.K.); (J.-H.L.); (D.A.N.)
| | - Xiaoyang Qi
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45221, USA; (A.K.); (J.-H.L.); (D.A.N.)
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA;
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Zhao X, Tian JJ, Yu H, Bryksa BC, Dupuis JH, Ou X, Qian Z, Song C, Wang S, Yada RY. Insights into the mechanism of membrane fusion induced by the plant defense element, plant-specific insert. J Biol Chem 2020; 295:14548-14562. [PMID: 32651232 DOI: 10.1074/jbc.ra120.014311] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 07/01/2020] [Indexed: 11/06/2022] Open
Abstract
In plants, many natural defense mechanisms include cellular membrane fusion as a way to resist infection by external pathogens. Several plant proteins mediate membrane fusion, but the detailed mechanism by which they promote fusion is less clear. Understanding this process could provide valuable insights into these proteins' physiological functions and guide bioengineering applications (i.e. the design of antimicrobial proteins). The plant-specific insert (PSI) from Solanum tuberosum can help reduce certain pathogen attack via membrane fusion. To gain new insights into the process of PSI-induced membrane fusion, a combined approach of NMR, FRET, and in silico studies was used. Our results indicate that (i) under acidic conditions, the PSI experiences a monomer-dimer equilibrium, and the dimeric PSI induces membrane fusion below a certain critical pH; (ii) after fusion, the PSI resides in a highly dehydrated environment with limited solvent accessibility, suggesting its capability in reducing repulsive dehydration forces between liposomes to facilitate fusion; and (iii) as shown by molecular dynamics simulations, the PSI dimer can bind stably to membrane surfaces and can bridge liposomes in close proximity, a critical step for the membrane fusion. In summary, this study provides new and unique insights into the mechanisms by which the PSI and similar proteins induce membrane fusion.
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Affiliation(s)
- Xiaoli Zhao
- College of Chemistry and Molecular Engineering and Beijing NMR Center, Peking University, Beijing, China
| | - Jenny Jingxin Tian
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hua Yu
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Brian C Bryksa
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - John H Dupuis
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Xiuyuan Ou
- MOH Key Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Science, Beijing, China
| | - Zhaohui Qian
- MOH Key Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Science, Beijing, China
| | - Chen Song
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China; Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
| | - Shenlin Wang
- College of Chemistry and Molecular Engineering and Beijing NMR Center, Peking University, Beijing, China; Beijing National Laboratory for Molecular Sciences, Beijing, China.
| | - Rickey Y Yada
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada.
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3
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Sun Y, Liou B, Chu Z, Fannin V, Blackwood R, Peng Y, Grabowski GA, Davis HW, Qi X. Systemic enzyme delivery by blood-brain barrier-penetrating SapC-DOPS nanovesicles for treatment of neuronopathic Gaucher disease. EBioMedicine 2020; 55:102735. [PMID: 32279952 PMCID: PMC7251241 DOI: 10.1016/j.ebiom.2020.102735] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 03/06/2020] [Accepted: 03/10/2020] [Indexed: 12/30/2022] Open
Abstract
Background Enzyme replacement therapy (ERT) can positively affect the visceral manifestations of lysosomal storage diseases (LSDs). However, the exclusion of the intravenous ERT agents from the central nervous system (CNS) prevents direct therapeutic effects. Methods Using a neuronopathic Gaucher disease (nGD) mouse model, CNS-ERT was created using a systemic, non-invasive, and CNS-selective delivery system based on nanovesicles of saposin C (SapC) and dioleoylphosphatidylserine (DOPS) to deliver to CNS cells and tissues the corrective, functional acid β-glucosidase (GCase). Findings Compared to free GCase, human GCase formulated with SapC-DOPS nanovesicles (SapC-DOPS-GCase) was more stable in serum, taken up into cells, mostly by a mannose receptor-independent pathway, and resulted in higher activity in GCase-deficient cells. In contrast to free GCase, SapC-DOPS-GCase nanovesicles penetrated through the blood-brain barrier into the CNS. The CNS targeting was mediated by surface phosphatidylserine (PS) of blood vessel and brain cells. Increased GCase activity and reduced GCase substrate levels were found in the CNS of SapC-DOPS-GCase-treated nGD mice, which showed profound improvement in brain inflammation and neurological phenotypes. Interpretation This first-in-class CNS-ERT approach provides considerable promise of therapeutic benefits for neurodegenerative diseases. Funding This study was supported by the National Institutes of Health grants R21NS 095047 to XQ and YS, R01NS 086134 and UH2NS092981 in part to YS; Cincinnati Children's Hospital Medical Center Research Innovation/Pilot award to YS and XQ; Gardner Neuroscience Institute/Neurobiology Research Center Pilot award to XQ and YS, Hematology-Oncology Programmatic Support from University of Cincinnati and New Drug State Key Project grant 009ZX09102-205 to XQ.
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Affiliation(s)
- Ying Sun
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
| | - Benjamin Liou
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Zhengtao Chu
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, USA
| | - Venette Fannin
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Rachel Blackwood
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Yanyan Peng
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Gregory A Grabowski
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Harold W Davis
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, USA
| | - Xiaoyang Qi
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA; Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati, College of Medicine, Cincinnati, OH, USA.
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4
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N'Guessan KF, Patel PH, Qi X. SapC-DOPS - a Phosphatidylserine-targeted Nanovesicle for selective Cancer therapy. Cell Commun Signal 2020; 18:6. [PMID: 31918715 PMCID: PMC6950924 DOI: 10.1186/s12964-019-0476-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 11/05/2019] [Indexed: 02/07/2023] Open
Affiliation(s)
- Kombo F N'Guessan
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA.,Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Priyankaben H Patel
- Department of Biomedical Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Xiaoyang Qi
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA. .,Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA. .,Department of Biomedical Sciences, University of Cincinnati, Cincinnati, OH, USA. .,Division of Human Genetics, Department of Pediatrics, University of Cincinnati College of Medicine and Cincinnati Children's Hospital and Medical Center, Cincinnati, OH, USA. .,Department of Biomedical Engineering, College of Engineering and Applied Science, University of Cincinnati, Cincinnati, OH, USA.
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5
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Liou B, Zhang W, Fannin V, Quinn B, Ran H, Xu K, Setchell KDR, Witte D, Grabowski GA, Sun Y. Combination of acid β-glucosidase mutation and Saposin C deficiency in mice reveals Gba1 mutation dependent and tissue-specific disease phenotype. Sci Rep 2019; 9:5571. [PMID: 30944381 PMCID: PMC6447580 DOI: 10.1038/s41598-019-41914-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 03/20/2019] [Indexed: 11/09/2022] Open
Abstract
Gaucher disease is caused by mutations in GBA1 encoding acid β-glucosidase (GCase). Saposin C enhances GCase activity and protects GCase from intracellular proteolysis. Structure simulations indicated that the mutant GCases, N370S (0 S), V394L (4L) and D409V(9V)/H(9H), had altered function. To investigate the in vivo function of Gba1 mutants, mouse models were generated by backcrossing the above homozygous mutant GCase mice into Saposin C deficient (C*) mice. Without saposin C, the mutant GCase activities in the resultant mouse tissues were reduced by ~50% compared with those in the presence of Saposin C. In contrast to 9H and 4L mice that have normal histology and life span, the 9H;C* and 4L;C* mice had shorter life spans. 9H;C* mice developed significant visceral glucosylceramide (GC) and glucosylsphingosine (GS) accumulation (GC»GS) and storage macrophages, but lesser GC in the brain, compared to 4L;C* mice that presents with a severe neuronopathic phenotype and accumulated GC and GS primarily in the brain. Unlike 9V mice that developed normally for over a year, 9V;C* pups had a lethal skin defect as did 0S;C* mice resembled that of 0S mice. These variant Gaucher disease mouse models presented a mutation specific phenotype and underscored the in vivo role of Saposin C in the modulation of Gaucher disease.
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Affiliation(s)
- Benjamin Liou
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Wujuan Zhang
- Department of Pathology and Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Venette Fannin
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Brian Quinn
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Huimin Ran
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Kui Xu
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Kenneth D R Setchell
- Department of Pathology and Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - David Witte
- Department of Pathology and Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Gregory A Grabowski
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Ying Sun
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA. .,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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6
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Sharma B, Kanwar SS. Phosphatidylserine: A cancer cell targeting biomarker. Semin Cancer Biol 2018; 52:17-25. [DOI: 10.1016/j.semcancer.2017.08.012] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 08/12/2017] [Accepted: 08/30/2017] [Indexed: 12/11/2022]
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7
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Harris M, Svensson F, Kopanitsa L, Ladds G, Bailey D. Emerging patents in the therapeutic areas of glioma and glioblastoma. Expert Opin Ther Pat 2018; 28:573-590. [DOI: 10.1080/13543776.2018.1494155] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Matthew Harris
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Fredrik Svensson
- IOTA Pharmaceuticals Ltd, St Johns Innovation Centre, Cambridge CB4 0WS, UK
| | - Liliya Kopanitsa
- IOTA Pharmaceuticals Ltd, St Johns Innovation Centre, Cambridge CB4 0WS, UK
| | - Graham Ladds
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - David Bailey
- IOTA Pharmaceuticals Ltd, St Johns Innovation Centre, Cambridge CB4 0WS, UK
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8
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Garrido-Arandia M, Cuevas-Zuviría B, Díaz-Perales A, Pacios LF. A Comparative Study of Human Saposins. Molecules 2018; 23:molecules23020422. [PMID: 29443946 PMCID: PMC6017893 DOI: 10.3390/molecules23020422] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 02/12/2018] [Accepted: 02/13/2018] [Indexed: 12/02/2022] Open
Abstract
Saposins are small proteins implicated in trafficking and loading of lipids onto Cluster of Differentiation 1 (CD1) receptor proteins that in turn present lipid antigens to T cells and a variety of T-cell receptors, thus playing a crucial role in innate and adaptive immune responses in humans. Despite their low sequence identity, the four types of human saposins share a similar folding pattern consisting of four helices linked by three conserved disulfide bridges. However, their lipid-binding abilities as well as their activities in extracting, transporting and loading onto CD1 molecules a variety of sphingo- and phospholipids in biological membranes display two striking characteristics: a strong pH-dependence and a structural change between a compact, closed conformation and an open conformation. In this work, we present a comparative computational study of structural, electrostatic, and dynamic features of human saposins based upon their available experimental structures. By means of structural alignments, surface analyses, calculation of pH-dependent protonation states, Poisson-Boltzmann electrostatic potentials, and molecular dynamics simulations at three pH values representative of biological media where saposins fulfill their function, our results shed light into their intrinsic features. The similarities and differences in this class of proteins depend on tiny variations of local structural details that allow saposins to be key players in triggering responses in the human immune system.
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MESH Headings
- Amino Acid Sequence
- Antigens, CD/chemistry
- Antigens, CD/immunology
- Antigens, CD1/chemistry
- Antigens, CD1/immunology
- Cell Membrane/chemistry
- Cell Membrane/immunology
- Humans
- Immunity, Innate
- Lipids/chemistry
- Lipids/immunology
- Molecular Dynamics Simulation
- Phospholipids/chemistry
- Phospholipids/immunology
- Protein Binding/immunology
- Protein Structure, Secondary
- Receptors, Antigen, T-Cell/chemistry
- Receptors, Antigen, T-Cell/immunology
- Saposins/chemistry
- Saposins/immunology
- T-Lymphocytes/immunology
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Affiliation(s)
- María Garrido-Arandia
- Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Campus de Montegancedo-UPM, 28223 Madrid, Spain.
| | - Bruno Cuevas-Zuviría
- Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Campus de Montegancedo-UPM, 28223 Madrid, Spain.
| | - Araceli Díaz-Perales
- Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Campus de Montegancedo-UPM, 28223 Madrid, Spain.
- Departamento de Biotecnología-Biología Vegetal, ETSIAAB, Universidad Politécnica de Madrid (UPM), Ciudad Universitaria, 28040 Madrid, Spain.
| | - Luis F Pacios
- Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Campus de Montegancedo-UPM, 28223 Madrid, Spain.
- Departamento de Biotecnología-Biología Vegetal, ETSIAAB, Universidad Politécnica de Madrid (UPM), Ciudad Universitaria, 28040 Madrid, Spain.
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9
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Bryksa BC, Yada RY. Protein Structure Insights into the Bilayer Interactions of the Saposin-Like Domain of Solanum tuberosum Aspartic Protease. Sci Rep 2017; 7:16911. [PMID: 29208977 PMCID: PMC5717070 DOI: 10.1038/s41598-017-16734-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 11/16/2017] [Indexed: 12/26/2022] Open
Abstract
Many plant aspartic proteases contain a saposin-like domain whose principal functions are intracellular sorting and host defence. Its structure is characterised by helical segments cross-linked by three highly conserved cystines. The present study on the saposin-like domain of Solanum tuberosum aspartic protease revealed that acidification from inactive to active conditions causes dimerisation and a strand-to-helix secondary structure transition independent of bilayer interaction. Bilayer fusion was shown to occur under reducing conditions yielding a faster shift to larger vesicle sizes relative to native conditions, implying that a lower level structural motif might be bilayer-active. Characterisation of peptide sequences based on the domain’s secondary structural regions showed helix-3 to be active (~4% of the full domain’s activity), and mutation of its sole positively charged residue resulted in loss of activity and disordering of structure. Also, the peptides’ respective circular dichroism spectra suggested that native folding within the full domain is dependent on surrounding structure. Overall, the present study reveals that the aspartic protease saposin-like domain active structure is an open saposin fold dimer whose formation is pH-dependent, and that a bilayer-active motif shared among non-saposin membrane-active proteins including certain plant defence proteins is nested within an overall structure essential for native functionality.
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Affiliation(s)
- Brian C Bryksa
- Ontario Agricultural College, University of Guelph, N1G 2W1, Guelph, Ontario, Canada
| | - Rickey Y Yada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, V6T 1Z4, British Columbia, Canada.
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10
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Krishnamoorthy A, Witkowski A, Tran JJ, Weers PMM, Ryan RO. Characterization of secondary structure and lipid binding behavior of N-terminal saposin like subdomain of human Wnt3a. Arch Biochem Biophys 2017; 630:38-46. [PMID: 28754322 DOI: 10.1016/j.abb.2017.07.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 07/14/2017] [Accepted: 07/24/2017] [Indexed: 02/06/2023]
Abstract
Wnt signaling is essential for embryonic development and adult homeostasis in multicellular organisms. A conserved feature among Wnt family proteins is the presence of two structural domains. Within the N-terminal (NT) domain there exists a motif that is superimposable upon saposin-like protein (SAPLIP) family members. SAPLIPs are found in plants, microbes and animals and possess lipid surface seeking activity. To investigate the function of the Wnt3a saposin-like subdomain (SLD), recombinant SLD was studied in isolation. Bacterial expression of this Wnt fragment was achieved only when the core SLD included 82 NT residues of Wnt3a (NT-SLD). Unlike SAPLIPs, NT-SLD required the presence of detergent to achieve solubility at neutral pH. Deletion of two hairpin loop extensions present in NT-SLD, but not other SAPLIPs, had no effect on the solubility properties of NT-SLD. Far UV circular dichroism spectroscopy of NT-SLD yielded 50-60% α-helix secondary structure. Limited proteolysis of isolated NT-SLD in buffer and detergent micelles showed no differences in cleavage kinetics. Unlike prototypical saposins, NT-SLD exhibited weak membrane-binding affinity and lacked cell lytic activity. In cell-based canonical Wnt signaling assays, NT-SLD was unable to induce stabilization of β-catenin or modulate the extent of β-catenin stabilization induced by full-length Wnt3a. Taken together, the results indicate neighboring structural elements within full-length Wnt3a affect SLD conformational stability. Moreover, SLD function(s) in Wnt proteins appear to have evolved away from those commonly attributed to SAPLIP family members.
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Affiliation(s)
- Aparna Krishnamoorthy
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Andrzej Witkowski
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA
| | - Jesse J Tran
- Department of Chemistry and Biochemistry, California State University, Long Beach, CA 90840, USA
| | - Paul M M Weers
- Department of Chemistry and Biochemistry, California State University, Long Beach, CA 90840, USA
| | - Robert O Ryan
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, CA 94720, USA; Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA.
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11
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Bryksa BC, Grahame DA, Yada RY. Comparative structure-function characterization of the saposin-like domains from potato, barley, cardoon and Arabidopsis aspartic proteases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1008-1018. [DOI: 10.1016/j.bbamem.2017.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 01/16/2017] [Accepted: 02/08/2017] [Indexed: 10/20/2022]
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12
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Davis HW, Hussain N, Qi X. Detection of cancer cells using SapC-DOPS nanovesicles. Mol Cancer 2016; 15:33. [PMID: 27160923 PMCID: PMC4862232 DOI: 10.1186/s12943-016-0519-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 05/03/2016] [Indexed: 12/15/2022] Open
Abstract
Unlike normal cells, cancer cells express high levels of phosphatidylserine on the extracellular leaflet of their cell membrane. Exploiting this characteristic, our lab developed a therapeutic agent that consists of the fusogenic protein, saposin C (SapC) which is embedded in dioleoylphosphatidylserine (DOPS) vesicles. These nanovesicles selectively target cancer cells and induce apoptosis. Here we review the data supporting use of SapC-DOPS to locate tumors for surgical resection or for treatment. In addition, there is important evidence suggesting that SapC-DOPS may also prove to be an effective novel cancer therapeutic reagent. Given that SapC-DOPS is easily labeled with lipophilic dyes, it has been combined with the far-red fluorescent dye, CellVue Maroon (CVM), for tumor targeting studies. We also have used contrast agents incorporated in the SapC-DOPS nanovesicles for computed tomography and magnetic resonance imaging, and review that data here. Administered intravenously, the fluorescently labeled SapC-DOPS traversed the blood–brain tumor barrier enabling identification of brain tumors. SapC-DOPS-CVM also detected a variety of other mouse tumors in vivo, rendering them observable by optical imaging using IVIS and multi-angle rotational optical imaging. Dye is detected within 30 min and remains within tumor for at least 7 days, whereas non-tumor tissues were unstained (some dye observed in the liver was transient, likely representing degradation products). Additionally, labeled SapC-DOPS ex vivo delineated tumors in human histological specimens. SapC-DOPS can also be labeled with contrast reagents for computed tomography or magnetic resonance imaging. In conclusion, labeled SapC-DOPS provides a convenient, specific, and nontoxic method for detecting tumors while concurrently offering a therapeutic benefit.
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Affiliation(s)
- Harold W Davis
- Division of Hematology/Oncology, Translational Medicine Laboratory, Department of Internal Medicine, University of Cincinnati College of Medicine, and Brain Tumor Center at UC Neuroscience Institute, 3512 Eden Avenue, Cincinnati, OH, 45267-0508, USA
| | - Nida Hussain
- Division of Hematology/Oncology, Translational Medicine Laboratory, Department of Internal Medicine, University of Cincinnati College of Medicine, and Brain Tumor Center at UC Neuroscience Institute, 3512 Eden Avenue, Cincinnati, OH, 45267-0508, USA
| | - Xiaoyang Qi
- Division of Hematology/Oncology, Translational Medicine Laboratory, Department of Internal Medicine, University of Cincinnati College of Medicine, and Brain Tumor Center at UC Neuroscience Institute, 3512 Eden Avenue, Cincinnati, OH, 45267-0508, USA. .,Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
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13
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Hill CH, Read RJ, Deane JE. Structure of human saposin A at lysosomal pH. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2015; 71:895-900. [PMID: 26144235 PMCID: PMC4498711 DOI: 10.1107/s2053230x15008584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 05/01/2015] [Indexed: 11/10/2022]
Abstract
The saposins are essential cofactors for the normal lysosomal degradation of complex glycosphingolipids by acid hydrolase enzymes; defects in either saposin or hydrolase function lead to severe metabolic diseases. Saposin A (SapA) activates the enzyme β-galactocerebrosidase (GALC), which catalyzes the breakdown of β-D-galactocerebroside, the principal lipid component of myelin. SapA is known to bind lipids and detergents in a pH-dependent manner; this is accompanied by a striking transition from a `closed' to an `open' conformation. However, previous structures were determined at non-lysosomal pH. This work describes a 1.8 Å resolution X-ray crystal structure determined at the physiologically relevant lysosomal pH 4.8. In the absence of lipid or detergent at pH 4.8, SapA is observeed to adopt a conformation closely resembling the previously determined `closed' conformation, showing that pH alone is not sufficient for the transition to the `open' conformation. Structural alignments reveal small conformational changes, highlighting regions of flexibility.
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Affiliation(s)
- Chris H Hill
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, England
| | - Randy J Read
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, England
| | - Janet E Deane
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, England
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Imaging and Therapy of Pancreatic Cancer with Phosphatidylserine-Targeted Nanovesicles. Transl Oncol 2015; 8:196-203. [PMID: 26055177 PMCID: PMC4486738 DOI: 10.1016/j.tranon.2015.03.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 03/09/2015] [Accepted: 03/17/2015] [Indexed: 12/12/2022] Open
Abstract
Pancreatic cancer remains one of the most intractable cancers, with a dismal prognosis reflected by a 5-year survival of ~6%. Since early disease symptoms are undefined and specific biomarkers are lacking, about 80% of patients present with advanced, inoperable tumors that represent a daunting challenge. Despite many clinical trials, no single chemotherapy agent has been reliably associated with objective response rates above 10% or median survival longer than 5 to 7 months. Although combination chemotherapy regimens have in recent years provided some improvement, overall survival (8-11 months) remains very poor. There is therefore a critical need for novel therapies that can improve outcomes for pancreatic cancer patients. Here, we present a summary of the current therapies used in the management of advanced pancreatic cancer and review novel therapeutic strategies that target tumor biomarkers. We also describe our recent research using phosphatidylserine-targeted saposin C-coupled dioleoylphosphatidylserine nanovesicles for imaging and therapy of pancreatic cancer.
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15
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Michalek M, Leippe M. Mechanistic insights into the lipid interaction of an ancient saposin-like protein. Biochemistry 2015; 54:1778-86. [PMID: 25715682 DOI: 10.1021/acs.biochem.5b00094] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The members of the expanding family of saposin-like proteins (SAPLIPs) have various biological functions in plants, animals, and humans. In addition to a similar protein backbone, these proteins have in common the fact that they interact with lipid membranes. According to their phylogenetic position, it has long been thought that amoeboid protozoans produce archetypes of SAPLIPs and that these are lytic proteins that can perforate membranes of prokaryotic and eukaryotic target cells. Here, we show that an amoebic SAPLIP from Entamoeba invadens does not form lytic pores in membranes but displays several characteristics that are known from human saposins. The protein named invaposin changes the conformation from a closed to an open form in the presence of lipid membranes, acts in a pH-dependent manner, selectively binds anionic lipids, aggregates lipid vesicles of the preferred composition, and dimerizes upon acidification. Our data indicate that the principal features of the lipid-binding saposins evolved long before the appearance of the vertebrate lineage and push the origin of saposins even deeper down the phylogenetic tree to unicellular organisms.
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Affiliation(s)
- Matthias Michalek
- Zoological Institute, Comparative Immunobiology, University of Kiel , Olshausenstrasse 40, 24098 Kiel, Germany
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16
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Blanco VM, Curry R, Qi X. SapC-DOPS nanovesicles: a novel targeted agent for the imaging and treatment of glioblastoma. Oncoscience 2015; 2:102-110. [PMID: 25859553 PMCID: PMC4381703 DOI: 10.18632/oncoscience.122] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/06/2015] [Indexed: 02/06/2023] Open
Abstract
Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor. Classified by the World Health Organization (WHO) as grade IV astrocytoma, GBMs are extremely aggressive, almost always recur, and despite our best efforts, remain incurable. This review describes the traditional treatment approaches that led to moderate successes in GBM patients, discusses standard imaging modalities, and presents data supporting the use of SapC-DOPS, a novel proteoliposomal formulation with tumoricidal activity, as a promising diagnostic imaging tool and an innovative anti-cancer agent against GBM.
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Affiliation(s)
- Víctor M. Blanco
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Richard Curry
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Xiaoyang Qi
- Division of Hematology and Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
- Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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17
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Winter P. Molecular Imaging at Nanoscale with Magnetic Resonance Imaging. Nanomedicine (Lond) 2014. [DOI: 10.1201/b17246-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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18
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Winter PM, Pearce J, Chu Z, McPherson CM, Takigiku R, Lee JH, Qi X. Imaging of brain tumors with paramagnetic vesicles targeted to phosphatidylserine. J Magn Reson Imaging 2014; 41:1079-87. [PMID: 24797437 DOI: 10.1002/jmri.24654] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 04/14/2014] [Accepted: 04/17/2014] [Indexed: 01/06/2023] Open
Abstract
PURPOSE To investigate paramagnetic saposin C and dioleylphosphatidylserine (SapC-DOPS) vesicles as a targeted contrast agent for imaging phosphatidylserine (PS) expressed by glioblastoma multiforme (GBM) tumors. MATERIALS AND METHODS Gd-DTPA-BSA/SapC-DOPS vesicles were formulated, and the vesicle diameter and relaxivity were measured. Targeting of Gd-DTPA-BSA/SapC-DOPS vesicles to tumor cells in vitro and in vivo was compared with nontargeted paramagnetic vesicles (lacking SapC). Mice with GBM brain tumors were imaged at 3, 10, 20, and 24 h postinjection to measure the relaxation rate (R1) in the tumor and the normal brain. RESULTS The mean diameter of vesicles was 175 nm, and the relaxivity at 7 Tesla was 3.32 (s*mM)(-1) relative to the gadolinium concentration. Gd-DTPA-BSA/SapC-DOPS vesicles targeted cultured cancer cells, leading to an increased R1 and gadolinium level in the cells. In vivo, Gd-DTPA-BSA/SapC-DOPS vesicles produced a 9% increase in the R1 of GBM brain tumors in mice 10 h postinjection, but only minimal changes (1.2% increase) in the normal brain. Nontargeted paramagnetic vesicles yielded minimal change in the tumor R1 at 10 h postinjection (1.3%). CONCLUSION These experiments demonstrate that Gd-DTPA-BSA/SapC-DOPS vesicles can selectively target implanted brain tumors in vivo, providing noninvasive mapping of the cancer biomarker PS.
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Affiliation(s)
- Patrick M Winter
- Department of Radiology, Cincinnati Children's Hospital, Cincinnati, Ohio, USA
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Chu Z, Abu-Baker S, Palascak MB, Ahmad SA, Franco RS, Qi X. Targeting and cytotoxicity of SapC-DOPS nanovesicles in pancreatic cancer. PLoS One 2013; 8:e75507. [PMID: 24124494 PMCID: PMC3790873 DOI: 10.1371/journal.pone.0075507] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 08/14/2013] [Indexed: 01/05/2023] Open
Abstract
Only a small number of promising drugs target pancreatic cancer, which is the fourth leading cause of cancer deaths with a 5-year survival of less than 5%. Our goal is to develop a new biotherapeutic agent in which a lysosomal protein (saposin C, SapC) and a phospholipid (dioleoylphosphatidylserine, DOPS) are assembled into nanovesicles (SapC-DOPS) for treating pancreatic cancer. A distinguishing feature of SapC-DOPS nanovesicles is their high affinity for phosphatidylserine (PS) rich microdomains, which are abnormally exposed on the membrane surface of human pancreatic tumor cells. To evaluate the role of external cell PS, in vitro assays were used to correlate PS exposure and the cytotoxic effect of SapC-DOPS in human tumor and nontumorigenic pancreatic cells. Next, pancreatic tumor xenografts (orthotopic and subcutaneous models) were used for tumor targeting and therapeutic efficacy studies with systemic SapC-DOPS treatment. We observed that the nanovesicles selectively killed human pancreatic cancer cells in vitro by inducing apoptotic death, whereas untransformed cells remained unaffected. This in vitro cytotoxic effect correlated to the surface exposure level of PS on the tumor cells. Using xenografts, animals treated with SapC-DOPS showed clear survival benefits and their tumors shrank or disappeared. Furthermore, using a double-tracking method in live mice, we showed that the nanovesicles were specifically targeted to orthotopically-implanted, bioluminescent pancreatic tumors. These data suggest that the acidic phospholipid PS is a biomarker for pancreatic cancer that can be effectively targeted for therapy utilizing cancer-selective SapC-DOPS nanovesicles. This study provides convincing evidence in support of developing a new therapeutic approach to pancreatic cancer.
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Affiliation(s)
- Zhengtao Chu
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Shadi Abu-Baker
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Mary B. Palascak
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Syed A. Ahmad
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Robert S. Franco
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Xiaoyang Qi
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
- Division of Human Genetics, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
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20
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Wojton J, Chu Z, Mathsyaraja H, Meisen WH, Denton N, Kwon CH, Chow LM, Palascak M, Franco R, Bourdeau T, Thornton S, Ostrowski MC, Kaur B, Qi X. Systemic delivery of SapC-DOPS has antiangiogenic and antitumor effects against glioblastoma. Mol Ther 2013; 21:1517-25. [PMID: 23732993 DOI: 10.1038/mt.2013.114] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 04/23/2013] [Indexed: 01/12/2023] Open
Abstract
Saposin C-dioleoylphosphatidylserine (SapC-DOPS) nanovesicles are a nanotherapeutic which effectively target and destroy cancer cells. Here, we explore the systemic use of SapC-DOPS in several models of brain cancer, including glioblastoma multiforme (GBM), and the molecular mechanism behind its tumor-selective targeting specificity. Using two validated spontaneous brain tumor models, we demonstrate the ability of SapC-DOPS to selectively and effectively cross the blood-brain tumor barrier (BBTB) to target brain tumors in vivo and reveal the targeting to be contingent on the exposure of the anionic phospholipid phosphatidylserine (PtdSer). Increased cell surface expression of PtdSer levels was found to correlate with SapC-DOPS-induced killing efficacy, and tumor targeting in vivo was inhibited by blocking PtdSer exposed on cells. Apart from cancer cell killing, SapC-DOPS also exerted a strong antiangiogenic activity in vitro and in vivo. Interestingly, unlike traditional chemotherapy, hypoxic cells were sensitized to SapC-DOPS-mediated killing. This study emphasizes the importance of PtdSer exposure for SapC-DOPS targeting and supports the further development of SapC-DOPS as a novel antitumor and antiangiogenic agent for brain tumors.
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Affiliation(s)
- Jeffrey Wojton
- Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery, The Ohio State University Medical Center, Columbus, Ohio 43210, USA
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Recent trends in multifunctional liposomal nanocarriers for enhanced tumor targeting. JOURNAL OF DRUG DELIVERY 2013; 2013:705265. [PMID: 23533772 PMCID: PMC3606784 DOI: 10.1155/2013/705265] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Accepted: 02/06/2013] [Indexed: 12/30/2022]
Abstract
Liposomes are delivery systems that have been used to formulate a vast variety of therapeutic and imaging agents for the past several decades. They have significant advantages over their free forms in terms of pharmacokinetics, sensitivity for cancer diagnosis and therapeutic efficacy. The multifactorial nature of cancer and the complex physiology of the tumor microenvironment require the development of multifunctional nanocarriers. Multifunctional liposomal nanocarriers should combine long blood circulation to improve pharmacokinetics of the loaded agent and selective distribution to the tumor lesion relative to healthy tissues, remote-controlled or tumor stimuli-sensitive extravasation from blood at the tumor's vicinity, internalization motifs to move from tumor bounds and/or tumor intercellular space to the cytoplasm of cancer cells for effective tumor cell killing. This review will focus on current strategies used for cancer detection and therapy using liposomes with special attention to combination therapies.
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22
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Olmeda B, García-Álvarez B, Pérez-Gil J. Structure–function correlations of pulmonary surfactant protein SP-B and the saposin-like family of proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:209-22. [DOI: 10.1007/s00249-012-0858-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 08/18/2012] [Accepted: 09/03/2012] [Indexed: 02/06/2023]
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Qi X, Flick MJ, Frederick M, Chu Z, Mason R, DeLay M, Thornton S. Saposin C coupled lipid nanovesicles specifically target arthritic mouse joints for optical imaging of disease severity. PLoS One 2012; 7:e33966. [PMID: 22470501 PMCID: PMC3314692 DOI: 10.1371/journal.pone.0033966] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 02/22/2012] [Indexed: 12/15/2022] Open
Abstract
Rheumatoid arthritis is a chronic inflammatory disease affecting approximately 1% of the population and is characterized by cartilage and bone destruction ultimately leading to loss of joint function. Early detection and intervention of disease provides the best hope for successful treatment and preservation of joint mobility and function. Reliable and non-invasive techniques that accurately measure arthritic disease onset and progression are lacking. We recently developed a novel agent, SapC-DOPS, which is composed of the membrane-associated lysosomal protein saposin C (SapC) incorporated into 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) lipid nanovesicles. SapC-DOPS has a high fusogenic affinity for phosphatidylserine-enriched microdomains on surfaces of target cell membranes. Incorporation of a far-red fluorophore, CellVue Maroon (CVM), into the nanovesicles allows for in vivo non-invasive visualization of the agent in targeted tissue. Given that phosphatidylserine is present only on the inner leaflet of healthy plasma membranes but is “flipped” to the outer leaflet upon cell damage, we hypothesized that SapC-DOPS would target tissue damage associated with inflammatory arthritis due to local surface-exposure of phosphatidylserine. Optical imaging with SapC-DOPS-CVM in two distinct models of arthritis, serum-transfer arthritis (e.g., K/BxN) and collagen-induced arthritis (CIA) revealed robust SapC-DOPS-CVM specific localization to arthritic paws and joints in live animals. Importantly, intensity of localized fluorescent signal correlated with macroscopic arthritic disease severity and increased with disease progression. Flow cytometry of cells extracted from arthritic joints demonstrated that SapC-DOPS-CVM localized to an average of 7–8% of total joint cells and primarily to CD11b+Gr-1+ cells. Results from the current studies strongly support the application of SapC-DOPS-CVM for advanced clinical and research applications including: detecting early arthritis onset, assessing disease progression real-time in live subjects, and providing novel information regarding cell types that may mediate arthritis progression within joints.
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Affiliation(s)
- Xiaoyang Qi
- Division of Hematology-Oncology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
- Division of Human Genetics, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Matthew J. Flick
- Division of Experimental Hematology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Malinda Frederick
- Division of Rheumatology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Zhengtao Chu
- Division of Hematology-Oncology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
- Division of Human Genetics, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Rachel Mason
- Division of Rheumatology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Monica DeLay
- Division of Rheumatology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Sherry Thornton
- Division of Rheumatology, Departments of Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States of America
- * E-mail:
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Membrane active antitumor activity of NK-18, a mammalian NK-lysin-derived cationic antimicrobial peptide. Biochimie 2012; 94:184-91. [DOI: 10.1016/j.biochi.2011.10.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/12/2011] [Indexed: 11/19/2022]
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Abu-Baker S, Chu Z, Stevens AM, Li J, Qi X. Cytotoxicity and Selectivity in Skin Cancer by SapC-DOPS Nanovesicles. ACTA ACUST UNITED AC 2012; 3:321-326. [PMID: 25485166 DOI: 10.4236/jct.2012.34041] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Squamous cell carcinoma (SCC) and melanoma are malignant human cancers of the skin with an annual mortality that exceed 10,000 cases every year in the USA alone. In this study, the lysosomal protein saposin C (SapC) and the phospholipid dioloylphosphatidylserine (DOPS) were assembled into cancer-selective nanovesicles (SapC-DOPS) and successfully tested using several in vitro and in vivo skin cancer models. Using MTT assay that measures the percentage of cell death, SapC-DOPS cytotoxic effect on three skin tumor cell lines (squamous cell carcinoma, SK-MEL-28, and MeWo) was compared to two normal nontumorigenic skin cells lines, normal immortalized keratinocyte (NIK) and human fibroblast cell (HFC). We observed that the nanovesicles selectively killed the skin cancer cells by inducing apoptotic cell death whereas untransformed skin cancer cells remained unaffected. Using subcutaneous skin tumor xenografts, animals treated with SapC-DOPS by subcutaneous injection showed a 79.4 % tumor reduced compared to the control after 4 days of treatment. We observed that the nanovesicles killed skin cancer cells by inducing apoptotic cell death compared to the control as revealed by TUNEL staining of xenograft tumor sections.
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Affiliation(s)
- Shadi Abu-Baker
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH
| | - Zhengtao Chu
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH ; Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - Ashley M Stevens
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH ; Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - Jie Li
- Department of Dermatology, University of Miami, Miami, FL
| | - Xiaoyang Qi
- Division of Hematology/Oncology, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH ; Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
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Muñoz F, Palomares-Jerez MF, Daleo G, Villalaín J, Guevara MG. Cholesterol and membrane phospholipid compositions modulate the leakage capacity of the swaposin domain from a potato aspartic protease (StAsp-PSI). Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1811:1038-44. [DOI: 10.1016/j.bbalip.2011.08.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 07/08/2011] [Accepted: 08/03/2011] [Indexed: 12/26/2022]
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Insights into the membrane interactions of the saposin-like proteins Na-SLP-1 and Ac-SLP-1 from human and dog hookworm. PLoS One 2011; 6:e25369. [PMID: 21991310 PMCID: PMC3184995 DOI: 10.1371/journal.pone.0025369] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 09/01/2011] [Indexed: 12/03/2022] Open
Abstract
Saposin-like proteins (SAPLIPs) from soil-transmitted helminths play pivotal roles in host-pathogen interactions and have a high potential as targets for vaccination against parasitic diseases. We have identified two non-orthologous SAPLIPs from human and dog hookworm, Na-SLP-1 and Ac-SLP-1, and solved their three-dimensional crystal structures. Both proteins share the property of membrane binding as monitored by liposome co-pelleting assays and monolayer adsorption. Neither SAPLIP displayed any significant haemolytic or bactericidal activity. Based on the structural information, as well as the results from monolayer adsorption, we propose models of membrane interactions for both SAPLIPs. Initial membrane contact of the monomeric Na-SLP-1 is most likely by electrostatic interactions between the membrane surface and a prominent basic surface patch. In case of the dimeric Ac-SLP-1, membrane interactions are most likely initiated by a unique tryptophan residue that has previously been implicated in membrane interactions in other SAPLIPs.
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28
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Lu K, Zhao G, Lu H, Zhao S, Song Y, Qi X, Hou Y. Toll-like receptor 4 can recognize SapC-DOPS to stimulate macrophages to express several cytokines. Inflamm Res 2010; 60:153-61. [PMID: 20853174 DOI: 10.1007/s00011-010-0249-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 07/20/2010] [Accepted: 09/06/2010] [Indexed: 02/04/2023] Open
Abstract
OBJECTIVE AND DESIGN SapC-DOPS is a newly combined compound consisting of saposin C and dioleoylphosphatidylserine (DOPS). Our recent study showed that SapC-DOPS exhibits anti-tumor activity. However, SapC-DOPS has recognition elements of Toll-like receptor (TLR) 2 and TLR4; therefore, we want to know whether SapC-DOPS can induce abnormal immunoreaction via identification TLRs. METHODS We investigated the capacity of SapC-DOPS to induce cytokines in vivo and in vitro and analyzed the involvement of TLR and NF-kB in these cytokines production. RESULTS SapC-DOPS could activate the cytokine production by peripheral macrophages, enhance the expressions of TLR4 and stimulate the NF-κB nuclear translocation. PDTC, an NF-κB inhibitor, could decrease the SapC-DOPS inducible TNF-α and IL-1β production. CONCLUSIONS SapC-DOPS was similar to LPS in the immune response and may induce the production of cytokines in macrophages via the TLR4 signaling pathway and, at least in part, the alteration of the NF-κB pathway.
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Affiliation(s)
- Kaihua Lu
- Immunology and Reproductive Biology Lab of Medical School and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People's Republic of China
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Mysliwy J, Dingley AJ, Stanisak M, Jung S, Lorenzen I, Roeder T, Leippe M, Grötzinger J. Caenopore-5: the three-dimensional structure of an antimicrobial protein from Caenorhabditis elegans. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2010; 34:323-330. [PMID: 19917307 DOI: 10.1016/j.dci.2009.11.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 05/28/2023]
Abstract
The caenopore-5 protein encoded by the spp-5 gene is one of the 33 caenopores identified in Caenorhabditis elegans and is a pore-forming peptide which plays an important role in the elimination of Escherichia coli ingested by the worm. Thus, caenopore-5 appears to contribute to the nutrition of the worm while simultaneously protecting the organism against pathogens. Here, three-dimensional heteronuclear NMR spectroscopy was used to solve the solution structure of caenopore-5. The NMR data revealed that two conformers of caenopore-5 exist in solution which differ by the isomerization of the peptide bond of Pro-81. The overall structure of the two caenopore-5 conformers consists of five amphiphatic helices connected by three disulfide bonds. The five helices are arranged in a folded leaf which is the characteristic signature of the SAPLIP family. The structure presented here is the first of an effector protein of the defensive system elucidated for the well-known model organism C. elegans.
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Affiliation(s)
- Justyna Mysliwy
- Institute of Biochemistry, Christian-Albrechts-University Kiel, Olshausenstr. 40, 24098 Kiel, Germany
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30
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Qi X, Chu Z, Mahller YY, Stringer KF, Witte DP, Cripe TP. Cancer-selective targeting and cytotoxicity by liposomal-coupled lysosomal saposin C protein. Clin Cancer Res 2009; 15:5840-51. [PMID: 19737950 DOI: 10.1158/1078-0432.ccr-08-3285] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
PURPOSE Saposin C is a multifunctional protein known to activate lysosomal enzymes and induce membrane fusion in an acidic environment. Excessive accumulation of lipid-coupled saposin C in lysosomes is cytotoxic. Because neoplasms generate an acidic microenvironment, caused by leakage of lysosomal enzymes and hypoxia, we hypothesized that saposin C may be an effective anticancer agent. We investigated the antitumor efficacy and systemic biodistribution of nanovesicles comprised of saposin C coupled with dioleoylphosphatidylserine in preclinical cancer models. EXPERIMENTAL DESIGN Neuroblastoma, malignant peripheral nerve sheath tumor and, breast cancer cells were treated with saposin C-dioleoylphosphatidylserine nanovesicles and assessed for cell viability, ceramide elevation, caspase activation, and apoptosis. Fluorescently labeled saposin C-dioleoylphosphatidylserine was i.v. injected to determine in vivo tumor-targeting specificity. Antitumor activity and toxicity profile of saposin C-dioleoylphosphatidylserine were evaluated in xenograft models. RESULTS Saposin C-dioleoylphosphatidylserine nanovesicles, with a mean diameter of approximately 190 nm, showed specific tumor-targeting activity shown through in vivo imaging. Following i.v. administration, saposin C-dioleoylphosphatidylserine nanovesicles preferentially accumulated in tumor vessels and cells in tumor-bearing mice. Saposin C-dioleoylphosphatidylserine induced apoptosis in multiple cancer cell types while sparing normal cells and tissues. The mechanism of saposin C-dioleoylphosphatidylserine induction of apoptosis was determined to be in part through elevation of intracellular ceramides, followed by caspase activation. In in vivo models, saposin C-dioleoylphosphatidylserine nanovesicles significantly inhibited growth of preclinical xenografts of neuroblastoma and malignant peripheral nerve sheath tumor. I.v. dosing of saposin C-dioleoylphosphatidylserine showed no toxic effects in nontumor tissues. CONCLUSIONS Saposin C-dioleoylphosphatidylserine nanovesicles offer promise as a novel, nontoxic, cancer-targeted, antitumor agent for treating a broad range of cancers.
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Affiliation(s)
- Xiaoyang Qi
- Division and Program in HumanGenetics, 3333 Burnet Avenue, Cincinnati, Ohio 45229-3039, USA.
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31
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Beck MR, Dekoster GT, Cistola DP, Goldman WE. NMR structure of a fungal virulence factor reveals structural homology with mammalian saposin B. Mol Microbiol 2009; 72:344-53. [PMID: 19298372 DOI: 10.1111/j.1365-2958.2009.06647.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The fungal protein CBP (calcium binding protein) is a known virulence factor with an unknown virulence mechanism. The protein was identified based on its ability to bind calcium and its prevalence as Histoplasma capsulatum's most abundant secreted protein. However, CBP has no sequence homology with other CBPs and contains no known calcium binding motifs. Here, the NMR structure of CBP reveals a highly intertwined homodimer and represents the first atomic level NMR model of any fungal virulence factor. Each CBP monomer is comprised of four alpha-helices that adopt the saposin fold, characteristic of a protein family that binds to membranes and lipids. This structural homology suggests that CBP functions as a lipid binding protein, potentially interacting with host glycolipids in the phagolysosome of host cells.
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Affiliation(s)
- Moriah R Beck
- Department of Molecular Microbiology, Washington University in St Louis, St Louis, MO, USA
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32
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CHU ZHENGTAO, SUN YING, KUAN CHIAYI, GRABOWSKI GREGORYA, QI XIAOYANG. Saposin C: Neuronal Effect and CNS Delivery by Liposomes. Ann N Y Acad Sci 2008. [DOI: 10.1111/j.1749-6632.2005.tb00031.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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33
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Abu-Baker S, Qi X, Lorigan GA. Investigating the interaction of saposin C with POPS and POPC phospholipids: a solid-state NMR spectroscopic study. Biophys J 2007; 93:3480-90. [PMID: 17704143 PMCID: PMC2072076 DOI: 10.1529/biophysj.107.107789] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The interaction of Saposin C (Sap C) with negatively charged phospholipids such as phosphatidylserine (PS) is essential for its biological function. In this study, Sap C (initially protonated in a weak acid) was inserted into multilamellar vesicles (MLVs) consisting of either 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-L-serine] (negatively charged, POPS) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (neutrally charged, POPC). The MLVs were then investigated using solid-state NMR spectroscopy under neutral pH (7.0) conditions. The (2)H and (31)P solid-state NMR spectroscopic data of Sap C-POPS and Sap C-POPC MLVs (prepared under the same conditions) were compared using the (2)H order parameter profiles of the POPC-d(31) or POPS-d(31) acyl chains as well as the (31)P chemical shift anisotropy width and (31)P T(1) relaxation times of the phospholipids headgroups. All those solid-state NMR spectroscopic approaches indicate that protonated Sap C disturbs the POPS bilayers and not the POPC lipid bilayers. These observations suggest for the first time that protonated Sap C inserts into PS bilayers and forms a stable complex with the lipids even after resuspension under neutral buffer conditions. Additionally, (31)P solid-state NMR spectroscopic studies of mechanically oriented phospholipids on glass plates were conducted and perturbation effect of Sap C on both POPS and POPC bilayers was compared. Unlike POPC bilayers, the data indicates that protonated Sap C (initially protonated in a weak acid) was unable to produce well-oriented POPS bilayers on glass plates at neutral pH. Conversely, unprotonated Sap C (initially dissolved in a neutral buffer) did not interact significantly with POPS phospholipids allowing them to produce well-oriented bilayers at neutral pH.
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Affiliation(s)
- Shadi Abu-Baker
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
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34
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Barman H, Walch M, Latinovic-Golic S, Dumrese C, Dolder M, Groscurth P, Ziegler U. Cholesterol in negatively charged lipid bilayers modulates the effect of the antimicrobial protein granulysin. J Membr Biol 2007; 212:29-39. [PMID: 17206515 DOI: 10.1007/s00232-006-0040-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 09/05/2006] [Indexed: 10/23/2022]
Abstract
The release of granulysin, a 9-kDa cationic protein, from lysosomal granules of cytotoxic T lymphocytes and natural killer cells plays an important role in host defense against microbial pathogens. Granulysin is endocytosed by the infected target cell via lipid rafts and kills subsequently intracellular bacteria. The mechanism by which granulysin binds to eukaryotic and prokaryotic cells but lyses only the latter is not well understood. We have studied the effect of granulysin on large unilamellar vesicles (LUVs) and supported bilayers with prokaryotic and eukaryotic lipid mixtures or model membranes with various lipid compositions and charges. Binding of granulysin to bilayers with negative charges, as typically found in bacteria and lipid rafts of eukaryotic cells, was shown by immunoblotting. Fluorescence release assays using LUV revealed an increase in permeability of prokaryotic, negatively charged and lipid raft-like bilayers devoid of cholesterol. Changes in permeability of these bilayers could be correlated to defects of various sizes penetrating supported bilayers as shown by atomic force microscopy. Based on these results, we conclude that granulysin causes defects in negatively charged cholesterol-free membranes, a membrane composition typically found in bacteria. In contrast, granulysin is able to bind to lipid rafts in eukaryotic cell membranes, where it is taken up by the endocytotic pathway, leaving the cell intact.
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Affiliation(s)
- Hanna Barman
- Division of Cell Biology, Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
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35
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Locatelli-Hoops S, Remmel N, Klingenstein R, Breiden B, Rossocha M, Schoeniger M, Koenigs C, Saenger W, Sandhoff K. Saposin A Mobilizes Lipids from Low Cholesterol and High Bis(monoacylglycerol)phosphate-containing Membranes. J Biol Chem 2006; 281:32451-60. [PMID: 16905746 DOI: 10.1074/jbc.m607281200] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Saposin A (Sap-A) is one of five known sphingolipid activator proteins required for the lysosomal degradation of sphingolipids and for the loading of lipid antigens onto antigen-presenting molecules of the CD1 type. Sap-A assists in the degradation of galactosylceramide by galactosylceramide-beta-galactosidase in vivo, which takes place at the surface of intraendosomal/intralysosomal vesicles. Sap-A is believed to mediate the interaction between the enzyme and its membrane-bound substrate. Its dysfunction causes a variant form of Krabbe disease. In the present study we prepared glycosylated Sap-A free of other Saps, taking advantage of the Pichia pastoris expression system. Using liposomes and surface plasmon resonance spectroscopy, we tested the binding and lipid mobilization capacity of Sap-A under different conditions. Along the endocytic pathway, the pH value decreases, and the lipid composition of intraendosomal and intralysosomal membranes changes drastically. In the inner membranes the cholesterol concentration decreases, and that of the anionic phospholipid bis(monoacylglycero)phosphate increases. Here, we show that Sap-A is able to bind to liposomes and to mobilize lipids out of them at acidic pH values below pH 4.7. Low cholesterol levels and increasing concentrations of bis(monoacylglycero)phosphate favor lipid extraction significantly. Galactosylceramide as a bilayer component is not essential for lipid mobilization by Sap-A, which requires intact disulfide bridges for activity. We also show for the first time that glycosylation of Sap-A is essential for its lipid extraction activity. Variant Sap-A proteins, which cause storage of galactosylceramide in humans (Krabbe disease, Spiegel, R., Bach, G., Sury, V., Mengistu, G., Meidan, B., Shalev, S., Shneor, Y., Mandel, H., and Zeigler, M. (2005) Mol. Genet. Metab. 84, 160-166) and in mutant mice (Matsuda, J., Vanier, M. T., Saito, Y., Tohyama, J., and Suzuki, K. (2001) Hum. Mol. Genet. 10, 1191-1199) are deficient in lipid extraction capacity.
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Affiliation(s)
- Silvia Locatelli-Hoops
- Kekulé-Institut für Organische Chemie und Biochemie, Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany
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36
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Alattia JR, Shaw JE, Yip CM, Privé GG. Direct visualization of saposin remodelling of lipid bilayers. J Mol Biol 2006; 362:943-53. [PMID: 16949605 DOI: 10.1016/j.jmb.2006.08.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Revised: 07/28/2006] [Accepted: 08/04/2006] [Indexed: 11/17/2022]
Abstract
Saposins A, B, C and D are soluble, non-enzymatic proteins that interact with lysosomal membranes to activate the breakdown and transfer of glycosphingolipids. The mechanisms of hydrolase activation and lipid transfer by saposins remain unknown. We have used in situ atomic force microscopy (AFM) with simultaneous confocal fluorescence microscopy to investigate the interactions of saposins with lipid membranes. AFM images of the effect of saposins A, B and C on supported lipid bilayers showed a time and concentration-dependent nucleated spread of membrane transformation. Saposin B produced deep gaps that ultimately filled with granular material, while saposins A and C lead to localized areas of membrane that were reduced in height by approximately 1.5 nm. Fluorescence-labeled saposin C co-localized with the transformed areas of the bilayer, indicating stable binding to the membrane. Fluorescence resonance energy transfer confirmed a direct interaction between saposin C and lipid. Under certain conditions of membrane lipid composition and saposin concentration, extensive bilayer lipid removal was observed. We propose a multi-step mechanism that integrates the structural features and amphipathic properties of the saposin proteins.
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Affiliation(s)
- Jean-René Alattia
- Division of Cancer Genomics and Proteomics, Ontario Cancer Institute, Toronto, Ontario, Canada M5G 1L7
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37
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Waring AJ, Walther FJ, Gordon LM, Hernandez-Juviel JM, Hong T, Sherman MA, Alonso C, Alig T, Braun A, Bacon D, Zasadzinski JA. The role of charged amphipathic helices in the structure and function of surfactant protein B. ACTA ACUST UNITED AC 2006; 66:364-74. [PMID: 16316452 DOI: 10.1111/j.1399-3011.2005.00300.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Surfactant protein B (SP-B) is essential for normal lung surfactant function. Theoretical models predict that the disulfide cross-linked, N- and C-terminal domains of SP-B fold as charged amphipathic helices, and suggest that these adjacent helices participate in critical surfactant activities. This hypothesis is tested using a disulfide-linked construct (Mini-B) based on the primary sequences of the N- and C-terminal domains. Consistent with theoretical predictions of the full-length protein, both isotope-enhanced Fourier transform infrared (FTIR) spectroscopy and molecular modeling confirm the presence of charged amphipathic alpha-helices in Mini-B. Similar to that observed with native SP-B, Mini-B in model surfactant lipid mixtures exhibits marked in vitro activity, with spread films showing near-zero minimum surface tensions during cycling using captive bubble surfactometry. In vivo, Mini-B shows oxygenation and dynamic compliance that compare favorably with that of full-length SP-B. Mini-B variants (i.e. reduced disulfides or cationic residues replaced by uncharged residues) or Mini-B fragments (i.e. unlinked N- and C-terminal domains) produced greatly attenuated in vivo and in vitro surfactant properties. Hence, the combination of structure and charge for the amphipathic alpha-helical N- and C-terminal domains are key to SP-B function.
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Affiliation(s)
- A J Waring
- Department of Medicine, Division of Infectious Diseases, UCLA School of Medicine, Center for Health Sciences, Los Angeles, CA 90095, USA.
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38
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Abstract
Saposins A and C are sphingolipid activator proteins required for the lysosomal breakdown of galactosylceramide and glucosylceramide, respectively. The saposins interact with lipids, leading to an enhanced accessibility of the lipid headgroups to their cognate hydrolases. We have determined the crystal structures of human saposins A and C to 2.0 Angstroms and 2.4 Angstroms, respectively, and both reveal the compact, monomeric saposin fold. We confirmed that these two proteins were monomeric in solution at pH 7.0 by analytical centrifugation. However, at pH 4.8, in the presence of the detergent C(8)E(5), saposin A assembled into dimers, while saposin C formed trimers. Saposin B was dimeric under all conditions tested. The self-association of the saposins is likely to be relevant to how these small proteins interact with lipids, membranes, and hydrolase enzymes.
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Affiliation(s)
- Victoria E Ahn
- Department of Medical Biophysics, University of Toronto, Canada
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39
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Ramamoorthy A, Thennarasu S, Tan A, Lee DK, Clayberger C, Krensky AM. Cell selectivity correlates with membrane-specific interactions: a case study on the antimicrobial peptide G15 derived from granulysin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:154-63. [PMID: 16579960 DOI: 10.1016/j.bbamem.2006.02.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2005] [Revised: 02/08/2006] [Accepted: 02/13/2006] [Indexed: 11/18/2022]
Abstract
A 15-residue peptide dimer G15 derived from the cell lytic protein granulysin has been shown to exert potent activity against microbes, including E. coli, but not against human Jurkat cells [Z. Wang, E. Choice, A. Kaspar, D. Hanson, S. Okada, S.C. Lyu, A.M. Krensky, C. Clayberger, Bactericidal and tumoricidal activities of synthetic peptides derived from granulysin. J. Immunol. 165 (2000) 1486-1490]. We investigated the target membrane selectivity of G15 using fluorescence, circular dichroism and 31P NMR methods. The ANS uptake assay shows that the extent of E. coli outer membrane disruption depends on G15 concentration. 31P NMR spectra obtained from E. coli total lipid bilayers incorporated with G15 show disruption of lipid bilayers. Fluorescence binding studies on the interaction of G15 with synthetic liposomes formed of E. coli lipids suggest a tight binding of the peptide at the membrane interface. The peptide also binds to negatively charged POPC/POPG (3:1) lipid vesicles but fails to insert deep into the membrane interior. These results are supported by the peptide-induced changes in the measured isotropic chemical shift and T1 values of POPG in 3:1 POPC:POPG multilamellar vesicles while neither a non-lamellar phase nor a fragmentation of bilayers was observed from NMR studies. The circular dichroism studies reveal that the peptide exists as a random coil in solution but folds into a less ordered conformation upon binding to POPC/POPG (3:1) vesicles. However, G15 does not bind to lipid vesicles made of POPC/POPG/Chl (9:1:1) mixture, mimicking tumor cell membrane. These results explain the susceptibility of E. coli and the resistance of human Jurkat cells to G15, and may have implications in designing membrane-selective therapeutic agents.
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Affiliation(s)
- Ayyalusamy Ramamoorthy
- Department of Chemistry and Biophysics Research Division, University of Michigan, 930 N. University Avenue, Ann Arbor, MI 48109-1055, USA.
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40
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Schultz-Heienbrok R, Remmel N, Klingenstein R, Rossocha M, Sandhoff K, Saenger W, Maier T. Crystallization and preliminary characterization of three different crystal forms of human saposin C heterologously expressed in Pichia pastoris. Acta Crystallogr Sect F Struct Biol Cryst Commun 2006; 62:117-20. [PMID: 16511279 PMCID: PMC2150943 DOI: 10.1107/s1744309105043186] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 12/23/2005] [Indexed: 11/10/2022]
Abstract
The amphiphilic saposin proteins (A, B, C and D) act at the lipid-water interface in lysosomes, mediating the hydrolysis of membrane building blocks by water-soluble exohydrolases. Human saposin C activates glucocerebrosidase and beta-galactosylceramidase. The protein has been expressed in Pichia pastoris, purified and crystallized in three different crystal forms, diffracting to a maximum resolution of 2.5 A. Hexagonal crystals grew from 2-propanol-containing solution and contain a single molecule in the asymmetric unit according to the Matthews coefficient. Orthorhombic and tetragonal crystals were both obtained with pentaerythritol ethoxylate and are predicted to contain two molecules in the asymmetric unit. Attempts to determine the respective crystal structures by molecular replacement using either the known NMR structure of human saposin C or a related crystal structure as search models have so far failed. The failure of the molecular-replacement method is attributed to conformational changes of the protein, which are known to be required for its biological activity. Crystal structures of human saposin C therefore might be the key to mapping out the conformational trajectory of saposin-like proteins.
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Affiliation(s)
| | - Natascha Remmel
- Kekule-Institut für Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany
| | - R. Klingenstein
- Kekule-Institut für Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany
| | - Maksim Rossocha
- Institut für Chemie und Biochemie/Kristallographie, Freie Universität Berlin, Germany
| | - Konrad Sandhoff
- Kekule-Institut für Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany
| | - Wolfram Saenger
- Institut für Chemie und Biochemie/Kristallographie, Freie Universität Berlin, Germany
| | - Timm Maier
- Institut für Chemie und Biochemie/Kristallographie, Freie Universität Berlin, Germany
- Institute for Molecular Biology and Biophysics, Swiss Federal Institute of Technology, ETH Zürich, Switzerland
- Correspondence e-mail:
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41
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Liu A, Wenzel N, Qi X. Role of lysine residues in membrane anchoring of saposin C. Arch Biochem Biophys 2006; 443:101-12. [PMID: 16256068 DOI: 10.1016/j.abb.2005.09.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Revised: 09/02/2005] [Accepted: 09/03/2005] [Indexed: 02/04/2023]
Abstract
Molecular dynamics (MD) simulations of the N-terminal region of saposin C, containing amino acid residues 4-20 (saposin C4-20), were performed over 2.5 ns in 1,2-dioleoyl-sn-glycero-3-phosphoserine (DOPS) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) monolayers. The simulations revealed several strong specific interactions of lysine 13 (Lys13) and lysine 17 (Lys17) in saposin C4-20 with the anionic phospholipids, which are required for membrane anchoring of the peptide. Membrane anchoring of saposin C4-20 facilitates saposin C-induced liposomal membrane fusion. Substitutions of Lys13 or Lys17 with alanine or glutamic acid led to a substantial loss of saposin C's fusogenicity. However, arginine replacement of Lys13 or Lys17 caused a partial loss of saposin C's fusogenic activity. The membrane anchoring of saposin C was altered in the presence of 0.4 M sodium chloride. Differential salt effects on Lys-mutant saposin Cs were observed using Trp fluorescence analysis. Low salt concentration had a more significant impact on Lys-mutant saposin C with a negatively charged amino acid residue replacement than those mutants with a positively charged or neutral residue replacement. These results indicate that positively charged amino acids at positions 13 and 17 are required for the fusogenic function of saposin C. In addition, the side-chain structure of lysine is crucial to the precise membrane anchoring which is necessary for the total fusion activity of saposin C. The MD simulations and vesicle size measurements of lysine-mutant saposins confirm the importance of the two lysine residues in saposin C4-20 for saposin C-induced fusion of negatively charged phospholipid membranes.
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Affiliation(s)
- Anping Liu
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
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42
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Lee JH, Yang ST, Rho SH, Im YJ, Kim SY, Kim YR, Kim MK, Kang GB, Kim JI, Rhee JH, Eom SH. Crystal structure and functional studies reveal that PAS factor from Vibrio vulnificus is a novel member of the saposin-fold family. J Mol Biol 2005; 355:491-500. [PMID: 16318855 DOI: 10.1016/j.jmb.2005.10.074] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 10/25/2005] [Accepted: 10/27/2005] [Indexed: 12/01/2022]
Abstract
PAS factor is a novel putative bacterial secretion factor thought to induce secretion of periplasmic proteins. We solved the crystal structure of PAS factor from Vibrio vulnificus at 1.8A resolution and found it to be comprised of five alpha helices that form an antiparallel bundle with an up-and-down topology, and to adopt the saposin-fold characteristic of a family of proteins that bind to membranes and lipids. PAS factor lacks the disulfide bridge characteristic of mammalian saposin-fold proteins; in fact, it shows no sequence homology with mammalian proteins. Nevertheless, the molecular architectures are similar, and the shared propensity for membrane interaction suggests strongly that PAS factor is another member of the saposin-fold family. Analysis of the CD spectra showed that PAS factor binds to membranes directly, while measurement of calcein dye leakage showed that PAS factor interacts strongly with liposomes composed of anionic phospholipids, making them leaky, but binds very weakly with liposomes composed of zwitterionic phospholipids. Moreover, by analyzing tryptophan fluorescence emission from four single-tryptophan mutants (V10W, T22W, F35W, and L70W), we identified the putative phospholipid-binding site of PAS factor. The resultant membrane destabilization likely mediates secretion of periplasmic proteins required for the in vivo survival and pathogenesis of V.vulnificus.
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Affiliation(s)
- Jun Hyuck Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
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43
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Abu-Baker S, Qi X, Newstadt J, Lorigan GA. Structural changes in a binary mixed phospholipid bilayer of DOPG and DOPS upon saposin C interaction at acidic pH utilizing 31P and 2H solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1717:58-66. [PMID: 16289479 DOI: 10.1016/j.bbamem.2005.09.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 09/07/2005] [Accepted: 09/12/2005] [Indexed: 12/15/2022]
Abstract
Saposin C (Sap C) is known to stimulate the catalytic activity of the lysosomal enzyme glucosylceramidase (GCase) that facilitates the hydrolysis of glucosylceramide to ceramide and glucose. Both Sap C and acidic phospholipids are required for full activity of GCase. In order to better understand this interaction, mixed bilayer samples prepared from dioleoylphosphatidylglycerol (DOPG) and dioleoylphosphatidylserine (DOPS) (5:3 ratio) and Sap C were investigated using (2)H and (31)P solid-state NMR spectroscopy at temperatures ranging from 25 to 50 degrees C at pH 4.7. The Sap C concentrations used to carry out these experiments were 0 mol%, 1 mol% and 3 mol% with respect to the phospholipids. The molecular order parameters (S(CD)) were calculated from the dePaked (2)H solid-state NMR spectra of Distearoyl-d70-phosphatidylglycerol (DSPG-d70) incorporated with DOPG and DOPS binary mixed bilayers. The S(CD) profiles indicate that the addition of Sap C to the negatively charged phospholipids is concentration dependent. S(CD) profiles of 1 mol% of the Sap C protein show only a very slight decrease in the acyl chain order. However, the S(CD) profiles of the 3 mol% of Sap C protein indicate that the interaction is predominantly increasing the disorder in the first half of the acyl chain near the head group (C1-C8) indicating that the amino and the carboxyl termini of Sap C are not inserting deep into the DOPG and DOPS mixed bilayers. The (31)P solid-state NMR spectra show that the chemical shift anisotropy (CSA) for both phospholipids decrease and the spectral broadening increases upon addition of Sap C to the mixed bilayers. The data indicate that Sap C interacts similarly with the head groups of both acidic phospholipids and that Sap C has no preference to DOPS over DOPG. Moreover, our solid-state NMR spectroscopic data agree with the structural model previously proposed in the literature [X. Qi, G.A. Grabowski, Differential membrane interactions of saposins A and C. Implication for the functional specificity, J. Biol. Chem. 276 (2001) 27010-27017] [1].
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Affiliation(s)
- Shadi Abu-Baker
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
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44
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McInturff JE, Wang SJ, Machleidt T, Lin TR, Oren A, Hertz CJ, Krutzik SR, Hart S, Zeh K, Anderson DH, Gallo RL, Modlin RL, Kim J. Granulysin-derived peptides demonstrate antimicrobial and anti-inflammatory effects against Propionibacterium acnes. J Invest Dermatol 2005; 125:256-63. [PMID: 16098035 PMCID: PMC4407689 DOI: 10.1111/j.0022-202x.2005.23805.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Propionibacterium acnes is a key therapeutic target in acne, yet this bacterium has become resistant to standard antibiotic agents. We investigated whether the human antimicrobial protein granulysin is a potential candidate for the treatment of acne. Granulysin and synthetic granulysin-derived peptides possessing a helix-loop-helix motif killed P. acnes in vitro. Modification of a helix-loop-helix peptide, 31-50, by substitution of a tryptophan for the valine at amino acid 44 (peptide 31-50v44w) to increase its interaction with bacterial surfaces also increased its antimicrobial activity. Moreover, when synthesized with D- rather than L-type amino acids, this peptide (D-31-50v44w) became less susceptible to degradation by proteases and more effective in killing P. acnes. Granulysin peptides were bactericidal, demonstrating an advantage over standard bacteriostatic antibiotics in their control of P. acnes. Moreover, peptide D-31-50v44w killed P. acnes in isolated human microcomedone preparations. Importantly, peptides 31-50, 31-50v44w, and D-31-50v44w also have potential anti-inflammatory effects, as demonstrated by suppression of P. acnes-stimulated cytokine release. Taken together, these data suggest that granulysin peptides may be useful as topical therapeutic agents, providing alternatives to current acne therapies.
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Affiliation(s)
- Jamie E. McInturff
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Shyh-Jeun Wang
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | | | | | - Ami Oren
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, West Los Angeles Veterans Administration Medical Center, Los Angeles, California, USA
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Cheryl J. Hertz
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Stephan R. Krutzik
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
- Department of Microbiology, Immunology, Molecular Genetics, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, USA
| | - Scott Hart
- Ansata Therapeutics, Inc., La Jolla, California, USA
| | - Karin Zeh
- Ansata Therapeutics, Inc., La Jolla, California, USA
| | - Daniel H. Anderson
- Howard Hughes Medical Institute, Los Angeles, California, USA
- UCLA-DOE Institute of Genomics and Proteomics, Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, USA
| | - Richard L. Gallo
- Division of Dermatology, University of California San Diego, San Diego, California, USA
- Veterans Administration San Diego Healthcare System, San Diego, California, USA
| | - Robert L. Modlin
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
- Department of Microbiology, Immunology, Molecular Genetics, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, USA
| | - Jenny Kim
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
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45
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Gopalakrishnan M, Grosch HW, Locatelli-Hoops S, Werth N, Smolenová E, Nettersheim M, Sandhoff K, Hasilik A. Purified recombinant human prosaposin forms oligomers that bind procathepsin D and affect its autoactivation. Biochem J 2005; 383:507-15. [PMID: 15255780 PMCID: PMC1133744 DOI: 10.1042/bj20040175] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Before delivery to endosomes, portions of proCD (procathepsin D) and proSAP (prosaposin) are assembled into complexes. We demonstrate that such complexes are also present in secretions of cultured cells. To study the formation and properties of the complexes, we purified proCD and proSAP from culture media of Spodoptera frugiperda cells that were infected with baculoviruses bearing the respective cDNAs. The biological activity of proCD was demonstrated by its pH-dependent autoactivation to pseudocathepsin D and that of proSAP was demonstrated by feeding to saposin-deficient cultured cells that corrected the storage of radioactive glycolipids. In gel filtration, proSAP behaved as an oligomer and proCD as a monomer. ProSAP altered the elution of proCD such that the latter was shifted into proSAP-containing fractions. ProSAP did not change the elution of mature cathepsin D. Using surface plasmon resonance and an immobilized biotinylated proCD, binding of proSAP was demonstrated under neutral and weakly acidic conditions. At pH 6.8, specific binding appeared to involve more than one binding site on a proSAP oligomer. The dissociation of the first site was characterized by a K(D1) of 5.8+/-2.9x10(-8) M(-1) (calculated for the monomer). ProSAP stimulated the autoactivation of proCD and also the activity of pseudocathepsin D. Concomitant with the activation, proSAP behaved as a substrate yielding tri- and disaposins and smaller fragments. Our results demonstrate that proSAP forms oligomers that are capable of binding proCD spontaneously and independent of the mammalian type N-glycosylation but not capable of binding mature cathepsin D. In addition to binding proSAP, proCD behaves as an autoactivable and processing enzyme and its binding partner as an activator and substrate.
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Affiliation(s)
| | - Hans-Wilhelm Grosch
- *Institute of Physiological Chemistry, Philipps-University Marburg, Karl-von-Frisch-Strasse 1, 35033 Marburg, Germany
| | - Silvia Locatelli-Hoops
- †The Kekulé Institute for Organic Chemistry and Biochemistry, University of Bonn, 53121 Bonn, Germany
| | - Norbert Werth
- †The Kekulé Institute for Organic Chemistry and Biochemistry, University of Bonn, 53121 Bonn, Germany
| | - Eva Smolenová
- *Institute of Physiological Chemistry, Philipps-University Marburg, Karl-von-Frisch-Strasse 1, 35033 Marburg, Germany
| | - Michael Nettersheim
- †The Kekulé Institute for Organic Chemistry and Biochemistry, University of Bonn, 53121 Bonn, Germany
| | - Konrad Sandhoff
- †The Kekulé Institute for Organic Chemistry and Biochemistry, University of Bonn, 53121 Bonn, Germany
| | - Andrej Hasilik
- *Institute of Physiological Chemistry, Philipps-University Marburg, Karl-von-Frisch-Strasse 1, 35033 Marburg, Germany
- To whom correspondence should be addressed (email )
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46
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You HX, Qi X, Yu L. Direct AFM observation of saposin C-induced membrane domains in lipid bilayers: from simple to complex lipid mixtures. Chem Phys Lipids 2005; 132:15-22. [PMID: 15530444 DOI: 10.1016/j.chemphyslip.2004.09.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Saposin C (Sap C) is a small glycoprotein required by glucosylceramidase (GCase) for hydrolysis of glucosylceramide to ceramide and glucose in lysosomes. The molecular mechanism underlying Sap C stimulation of the enzyme activation is not fully understood. Here, atomic force microscopy (AFM) has been used to study Sap C-membrane interactions under physiological conditions. First, to establish how Sap C-membrane interactions affect membrane structure, lipid bilayers containing zwitterionic and anionic phospholipids were used. It was observed that Sap C induced two types of membrane restructuring effects, i.e., the formation of patch-like domains and membrane destabilization. Bilayers underwent extensive structural reorganization. To validate the biological importance of the membrane restructuring effects, interaction of Sap C with lipid bilayers composed of cholesterol, sphingomyelin, and zwitterionic and anionic phospholipids were studied. Although similar membrane restructuring effects were observed, Sap C-membrane interactions, in this case, were remarkably modulated and their effects were restricted to a limited area. As a result, nanometer-sized domains were formed. The establishment of a model membrane system will allow us to further study the dynamics, structure and mechanism of the Sap C-associated membrane domains and to examine the important role that these domains may play in enzyme activation.
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Affiliation(s)
- Hong Xing You
- Department of Cell Biology, Neurobiology, and Anatomy, College of Medicine, University of Cincinnati, 3125 Eden Ave, Cincinnati, OH 45267-0521, USA.
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47
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Spiegel R, Bach G, Sury V, Mengistu G, Meidan B, Shalev S, Shneor Y, Mandel H, Zeigler M. A mutation in the saposin A coding region of the prosaposin gene in an infant presenting as Krabbe disease: first report of saposin A deficiency in humans. Mol Genet Metab 2005; 84:160-6. [PMID: 15773042 DOI: 10.1016/j.ymgme.2004.10.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A six-month-old infant girl presenting with progressive encephalopathy and abnormal myelination in the cerebral white matter was originally diagnosed as suffering from Krabbe disease. The diagnosis was based on a deficiency of galactocerebrosidase activity found in leukocytes isolated from whole blood. When cultured skin fibroblasts did not show a similar enzyme deficiency and sulphatide (stearoyl-1-14C) uptake indicated an abnormal storage of galactosylceramide, a deficiency of an activator was implied. A three base pair deletion was found in the saposin A coding sequence of the prosaposin gene leading to the deletion of a conserved valine at amino acid number 11 of the saposin A protein. This deletion in saposin A is proposed as the cause for the abnormal galactosylceramide metabolism in this infant. This is the first report of a saposin A mutation in humans leading to pathological consequences.
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Affiliation(s)
- Ronen Spiegel
- Department of Pediatrics, HaEmek Medical Center, Afula, Israel
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48
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Hawkins CA, de Alba E, Tjandra N. Solution structure of human saposin C in a detergent environment. J Mol Biol 2005; 346:1381-92. [PMID: 15713488 DOI: 10.1016/j.jmb.2004.12.045] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 11/04/2004] [Accepted: 12/20/2004] [Indexed: 01/19/2023]
Abstract
Saposin C is a lysosomal, membrane-binding protein that acts as an activator for the hydrolysis of glucosylceramide by the enzyme glucocerebrosidase. We used high-resolution NMR to determine the three-dimensional solution structure of saposin C in the presence of the detergent sodium dodecyl sulfate (SDS). This structure provides the first representation of membrane bound saposin C at the atomic level. In the presence of SDS, the protein adopts an open conformation with an exposed hydrophobic pocket. In contrast, the previously reported NMR structure of saposin C in the absence of SDS is compact and contains a hydrophobic core that is not exposed to the solvent. NMR data indicate that the SDS molecules interact with the hydrophobic pocket. The structure of saposin C in the presence of SDS is very similar to a monomer in the saposin B homodimer structure. Their comparison reveals possible similarity in the type of protein/lipid interaction as well as structural components differentiating their quaternary structures and functional specificity.
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Affiliation(s)
- Cheryl A Hawkins
- Laboratory of Biophysical Chemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, 50 Center Drive, Bethesda, MD 20892, USA
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49
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Qi X, Chu Z. Fusogenic domain and lysines in saposin C. Arch Biochem Biophys 2004; 424:210-8. [PMID: 15047193 DOI: 10.1016/j.abb.2004.02.023] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2003] [Revised: 02/17/2004] [Indexed: 02/07/2023]
Abstract
Saposin C, a sphingolipid activator protein with fusogenic activity, interacts specifically with the membrane containing negatively charged, unsaturated phospholipids. The kinetics and mechanism of saposin C-induced membrane fusion were previously investigated using acidic phospholipid liposomes. A hypothetic clip-on model for such a fusion process was illustrated by the ionic binding between saposin C and lipids, as well as the inter-saposin C hydrophobic interaction. Here, we report the location of the fusogenic domain in a linear sequence at the amino-terminal half of saposin C. This domain consisted of the first and second helical sequences. Selected positively charged lysines in the fusogenic domain were mutated to study the roles of basic residues in the saposin C-induced vesicle fusion. Based on the results, Lys13 and Lys17 were critical for the fusogenic activity, but had no effect on the enzymatic activation of acid beta-glucosidase (GCase). These results clearly indicate the segregation of the fusion and activation function into two different regions of saposin C. Interestingly, all the Lys mutant saposin Cs anchored on the acidic phospholipid membrane. Our data suggest that saposin C's fusogenic and activation functions have different requirements for the orientation and insertion manners of helical peptides in membranes.
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Affiliation(s)
- Xiaoyang Qi
- The Division and Program in Human Genetics, Cincinnati Children's Hospital Research Foundation, and Department of Pediatrics, The University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA.
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50
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Yamada M, Inui K, Hamada D, Nakahira K, Yanagihara K, Sakai N, Nishigaki T, Ozono K, Yanagihara I. Analysis of recombinant human saposin A expressed by Pichia pastoris. Biochem Biophys Res Commun 2004; 318:588-93. [PMID: 15120640 DOI: 10.1016/j.bbrc.2004.04.069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Indexed: 11/21/2022]
Abstract
Saposins (SAPs) are small glycoproteins required for activation of sphingolipid hydrolysis by lysosomal enzymes. Four SAPs, SAP-A, -B, -C, and -D, are proteolytically cleaved from a single gene product termed prosaposin. The mature coding sequence of human SAP-A tagged with 6-histidine was expressed in Pichia pastoris and the recombinant protein was purified from the culture supernatant by simple purification steps with an immobilized metal ion affinity column, a Concanavalin A column, and reversed-phase HPLC. Secreted SAP-A contained both glycosylated and nonglycosylated forms. Both forms of SAP-A activated galactocerebroside and 4-methylumbelliferyl beta-d-glucoside hydrolysis by galactocerebrosidase and glucocerebrosidase. SAP-A expressed in P. pastoris should be useful for further structural and functional analysis of this protein.
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Affiliation(s)
- Minoru Yamada
- Department of Developmental Infectious Diseases, Research Institute, Osaka Medical Center for Maternal and Child Health, Murodo-cho, Izumi, Japan
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