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Crow RS, Shaw CG, Grayfer L, Smith LC. Recombinant SpTransformer proteins are functionally diverse for binding and phagocytosis by three subtypes of sea urchin phagocytes. Front Immunol 2024; 15:1372904. [PMID: 38742116 PMCID: PMC11089230 DOI: 10.3389/fimmu.2024.1372904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 03/29/2024] [Indexed: 05/16/2024] Open
Abstract
Introduction The California purple sea urchin, Strongylocentrotus purpuratus, relies solely on an innate immune system to combat the many pathogens in the marine environment. One aspect of their molecular defenses is the SpTransformer (SpTrf) gene family that is upregulated in response to immune challenge. The gene sequences are highly variable both within and among animals and likely encode thousands of SpTrf isoforms within the sea urchin population. The native SpTrf proteins bind foreign targets and augment phagocytosis of a marine Vibrio. A recombinant (r)SpTrf-E1-Ec protein produced by E. coli also binds Vibrio but does not augment phagocytosis. Methods To address the question of whether other rSpTrf isoforms function as opsonins and augment phagocytosis, six rSpTrf proteins were expressed in insect cells. Results The rSpTrf proteins are larger than expected, are glycosylated, and one dimerized irreversibly. Each rSpTrf protein cross-linked to inert magnetic beads (rSpTrf::beads) results in different levels of surface binding and phagocytosis by phagocytes. Initial analysis shows that significantly more rSpTrf::beads associate with cells compared to control BSA::beads. Binding specificity was verified by pre-incubating the rSpTrf::beads with antibodies, which reduces the association with phagocytes. The different rSpTrf::beads show significant differences for cell surface binding and phagocytosis by phagocytes. Furthermore, there are differences among the three distinct types of phagocytes that show specific vs. constitutive binding and phagocytosis. Conclusion These findings illustrate the complexity and effectiveness of the sea urchin innate immune system driven by the natSpTrf proteins and the phagocyte cell populations that act to neutralize a wide range of foreign pathogens.
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Affiliation(s)
| | | | | | - L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC, United States
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2
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Barela Hudgell MA, Momtaz F, Jafri A, Alekseyev MA, Smith LC. Local Genomic Instability of the SpTransformer Gene Family in the Purple Sea Urchin Inferred from BAC Insert Deletions. Genes (Basel) 2024; 15:222. [PMID: 38397211 PMCID: PMC10887614 DOI: 10.3390/genes15020222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 02/02/2024] [Accepted: 02/05/2024] [Indexed: 02/25/2024] Open
Abstract
The SpTransformer (SpTrf) gene family in the purple sea urchin, Strongylocentrotus purpuratus, encodes immune response proteins. The genes are clustered, surrounded by short tandem repeats, and some are present in genomic segmental duplications. The genes share regions of sequence and include repeats in the coding exon. This complex structure is consistent with putative local genomic instability. Instability of the SpTrf gene cluster was tested by 10 days of growth of Escherichia coli harboring bacterial artificial chromosome (BAC) clones of sea urchin genomic DNA with inserts containing SpTrf genes. After the growth period, the BAC DNA inserts were analyzed for size and SpTrf gene content. Clones with multiple SpTrf genes showed a variety of deletions, including loss of one, most, or all genes from the cluster. Alternatively, a BAC insert with a single SpTrf gene was stable. BAC insert instability is consistent with variations in the gene family composition among sea urchins, the types of SpTrf genes in the family, and a reduction in the gene copy number in single coelomocytes. Based on the sequence variability among SpTrf genes within and among sea urchins, local genomic instability of the family may be important for driving sequence diversity in this gene family that would be of benefit to sea urchins in their arms race with marine microbes.
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Affiliation(s)
- Megan A. Barela Hudgell
- Department of Biological Sciences, George Washington University, Washington, DC 20052, USA; (M.A.B.H.); (F.M.)
| | - Farhana Momtaz
- Department of Biological Sciences, George Washington University, Washington, DC 20052, USA; (M.A.B.H.); (F.M.)
| | - Abiha Jafri
- Department of Biological Sciences, George Washington University, Washington, DC 20052, USA; (M.A.B.H.); (F.M.)
| | - Max A. Alekseyev
- Department of Mathematics and the Computational Biology Institute, George Washington University, Washington, DC 20052, USA;
| | - L. Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC 20052, USA; (M.A.B.H.); (F.M.)
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3
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Smith LC, Crow RS, Franchi N, Schrankel CS. The echinoid complement system inferred from genome sequence searches. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2023; 140:104584. [PMID: 36343741 DOI: 10.1016/j.dci.2022.104584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 10/01/2022] [Accepted: 10/31/2022] [Indexed: 06/16/2023]
Abstract
The vertebrate complement cascade is an essential host protection system that functions at the intersection of adaptive and innate immunity. However, it was originally assumed that complement was present only in vertebrates because it was activated by antibodies and functioned with adaptive immunity. Subsequently, the identification of the key component, SpC3, in sea urchins plus a wide range of other invertebrates significantly expanded the concepts of how complement functions. Because there are few reports on the echinoid complement system, an alternative approach to identify complement components in echinoderms is to search the deduced proteins encoded in the genomes. This approach identified known and putative members of the lectin and alternative activation pathways, but members of the terminal pathway are absent. Several types of complement receptors are encoded in the genomes. Complement regulatory proteins composed of complement control protein (CCP) modules are identified that may control the activation pathways and the convertases. Other regulatory proteins without CCP modules are also identified, however regulators of the terminal pathway are absent. The expansion of genes encoding proteins with Macpf domains is noteworthy because this domain is a signature of perforin and proteins in the terminal pathway. The results suggest that the major functions of the echinoid complement system are detection of foreign targets by the proteins that initiate the activation pathways resulting in opsonization by SpC3b fragments to augment phagocytosis and destruction of the foreign targets by the immune cells.
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Affiliation(s)
- L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington DC, USA.
| | - Ryley S Crow
- Department of Biological Sciences, George Washington University, Washington DC, USA
| | - Nicola Franchi
- Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Catherine S Schrankel
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, CA, USA
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4
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Queiroz V, Arizza V, Vazzana M, Custódio MR. Comparative evaluation of coelomocytes in Paracentrotus sea urchins: Description of new cell types and insights on spherulocyte maturation and sea urchin physiology. ZOOL ANZ 2022. [DOI: 10.1016/j.jcz.2022.06.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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5
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Barela Hudgell MA, Grayfer L, Smith LC. A flow cytometry based approach to identify distinct coelomocyte subsets of the purple sea urchin, Strongylocentrotus purpuratus. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2022; 130:104352. [PMID: 35065955 DOI: 10.1016/j.dci.2022.104352] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/12/2022] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
The sea urchin, Strongylocentrotus purpuratus, possesses at least seven distinguishable cell populations in the coelomic fluid, which vary in morphology, size, and function. Of these, the large phagocytes, small phagocytes, and red spherule cells are thought to be key to the echinoid immune response. Because there are currently no effective and rapid means of evaluating sea urchin coelomocytes, we developed a flow cytometry based approach to identify these subsets from unseparated, unstained, live cells. In particular our gating strategy distinguishes between the large phagocytes, small phagocytes, red spherule cells, and a mixed population of vibratile cells and colorless spherule cells. This flow cytometry based analysis increases the speed and improves the reliability of coelomocyte analysis compared to differential cell counts by microscopy.
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Affiliation(s)
- Megan A Barela Hudgell
- Department of Biological Sciences, George Washington University, Washington, DC, 20052, USA
| | - Leon Grayfer
- Department of Biological Sciences, George Washington University, Washington, DC, 20052, USA
| | - L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC, 20052, USA.
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6
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The Diverse Transformer (Trf) Protein Family in the Sea Urchin Paracentrotus lividus Acts through a Collaboration between Cellular and Humoral Immune Effector Arms. Int J Mol Sci 2021; 22:ijms22136639. [PMID: 34206148 PMCID: PMC8268236 DOI: 10.3390/ijms22136639] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 06/15/2021] [Accepted: 06/15/2021] [Indexed: 01/06/2023] Open
Abstract
Sea urchins are long-living marine invertebrates with a complex innate immune system, which includes expanded families of immune receptors. A central immune gene family in sea urchins encodes the Transformer (Trf) proteins. The Trf family has been studied mainly in the purple sea urchin Strongylocentrotus purpuratus. Here, we explore this protein family in the Mediterranean Sea urchin Paracentrotus lividus. The PlTrf genes and predicted proteins are highly diverse and show a typical Trf size range and structure. Coelomocytes and cell-free coelomic fluid from P. lividus contain different PlTrf protein repertoires with a shared subset, that bind specifically to E. coli. Using FACS, we identified five different P. lividus coelomocyte sub-populations with cell surface PlTrf protein expression. The relative abundance of the PlTrf-positive cells increases sharply following immune challenge with E. coli, but not following challenge with LPS or the sea urchin pathogen, Vibrio penaeicida. Phagocytosis of E. coli by P. lividus phagocytes is mediated through the cell-free coelomic fluid and is inhibited by blocking PlTrf activity with anti-SpTrf antibodies. Together, our results suggest a collaboration between cellular and humoral PlTrf-mediated effector arms in the P. lividus specific immune response to pathogens.
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7
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Schuh NW, Carrier TJ, Schrankel CS, Reitzel AM, Heyland A, Rast JP. Bacterial Exposure Mediates Developmental Plasticity and Resistance to Lethal Vibrio lentus Infection in Purple Sea Urchin (Strongylocentrotus purpuratus) Larvae. Front Immunol 2020; 10:3014. [PMID: 31993052 PMCID: PMC6971090 DOI: 10.3389/fimmu.2019.03014] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 12/09/2019] [Indexed: 12/27/2022] Open
Abstract
Exposure to and colonization by bacteria during development have wide-ranging beneficial effects on animal biology but can also inhibit growth or cause disease. The immune system is the prime mediator of these microbial interactions and is itself shaped by them. Studies using diverse animal taxa have begun to elucidate the mechanisms underlying the acquisition and transmission of bacterial symbionts and their interactions with developing immune systems. Moreover, the contexts of these associations are often confounded by stark differences between "wild type" microbiota and the bacterial communities associated with animals raised in conventional or germ-free laboratories. In this study, we investigate the spatio-temporal kinetics of bacterial colonization and associated effects on growth and immune function in larvae of the purple sea urchin (Strongylocentrotus purpuratus) as a model for host-microbe interactions and immune system development. We also compare the host-associated microbiota of developing embryos and larvae raised in natural seawater or exposed to adult-associated bacteria in the laboratory. Bacteria associated with zygotes, embryos, and early larvae are detectable with 16S amplicon sequencing, but 16S-FISH indicates that the vast majority of larval bacterial load is acquired after feeding begins and is localized to the gut lumen. The bacterial communities of laboratory-cultured embryos are significantly less diverse than the natural microbiota but recapitulate its major components (Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes), suggesting that biologically relevant host-microbe interactions can be studied in the laboratory. We also demonstrate that bacterial exposure in early development induces changes in morphology and in the immune system. In the absence of bacteria, larvae grow larger at the 4-arm stage. Additionally, bacteria-exposed larvae are significantly more resistant to lethal infection with the larva-associated pathogen Vibrio lentus suggesting that early exposure to high levels of microbes, as would be expected in natural conditions, affects the immune state in later larvae. These results expand our knowledge of microbial influences on early sea urchin development and establish a model in which to study the interactions between the developing larval immune system and the acquisition of larval microbiota.
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Affiliation(s)
- Nicholas W Schuh
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.,Department of Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada.,Department of Integrative Biology, University of Guelph, Guelph, ON, Canada
| | - Tyler J Carrier
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, United States
| | - Catherine S Schrankel
- Department of Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada.,Department of Immunology, University of Toronto, Toronto, ON, Canada.,Marine Biology Research Division, Scripps Institute of Oceanography, University of California, San Diego, San Diego, CA, United States
| | - Adam M Reitzel
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, United States
| | - Andreas Heyland
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada
| | - Jonathan P Rast
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.,Department of Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada.,Department of Immunology, University of Toronto, Toronto, ON, Canada.,Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, United States.,Emory Vaccine Center, Emory University, Atlanta, GA, United States
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8
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Oren M, Rosental B, Hawley TS, Kim GY, Agronin J, Reynolds CR, Grayfer L, Smith LC. Individual Sea Urchin Coelomocytes Undergo Somatic Immune Gene Diversification. Front Immunol 2019; 10:1298. [PMID: 31244844 PMCID: PMC6563789 DOI: 10.3389/fimmu.2019.01298] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 05/21/2019] [Indexed: 12/19/2022] Open
Abstract
The adaptive immune response in jawed vertebrates is marked by the ability to diversify somatically specific immune receptor genes. Somatic recombination and hypermutation of gene segments are used to generate extensive repertoires of T and B cell receptors. In contrast, jawless vertebrates utilize a distinct diversification system based on copy choice to assemble their variable lymphocyte receptors. To date, very little evidence for somatic immune gene diversification has been reported in invertebrate species. Here we show that the SpTransformer (SpTrf ; formerly Sp185/333) immune effector gene family members from individual coelomocytes from purple sea urchins undergo somatic diversification by means of gene deletions, duplications, and acquisitions of single nucleotide polymorphisms. While sperm cells from an individual sea urchin have identical SpTrf gene repertoires, single cells from two distinct coelomocyte subpopulations from the same sea urchin exhibit significant variation in the SpTrf gene repertoires. Moreover, the highly diverse gene sequences derived from single coelomocytes are all in-frame, suggesting that an unknown mechanism(s) driving these somatic changes involve stringent selection or correction processes for expression of productive SpTrf transcripts. Together, our findings infer somatic immune gene diversification strategy in an invertebrate.
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Affiliation(s)
- Matan Oren
- Department of Molecular Biology, Ariel University, Ariel, Israel.,Department of Biological Sciences, The George Washington University, Washington, DC, United States
| | - Benyamin Rosental
- French Associates' Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Be'er Sheva, Israel.,Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, United States.,Department of Pathology, Hopkins Marine Station, Stanford University, Pacific Grove, CA, United States
| | - Teresa S Hawley
- Flow Cytometry Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Gi-Young Kim
- Department of Biological Sciences, The George Washington University, Washington, DC, United States.,Department of Marine Life Sciences, Jeju National University, Jeju City, South Korea
| | - Jacob Agronin
- Department of Biological Sciences, The George Washington University, Washington, DC, United States
| | - Caroline R Reynolds
- Department of Biological Sciences, The George Washington University, Washington, DC, United States
| | - Leon Grayfer
- Department of Biological Sciences, The George Washington University, Washington, DC, United States
| | - L Courtney Smith
- Department of Biological Sciences, The George Washington University, Washington, DC, United States
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9
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Golconda P, Buckley KM, Reynolds CR, Romanello JP, Smith LC. The Axial Organ and the Pharynx Are Sites of Hematopoiesis in the Sea Urchin. Front Immunol 2019; 10:870. [PMID: 31105697 PMCID: PMC6494969 DOI: 10.3389/fimmu.2019.00870] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 04/04/2019] [Indexed: 01/01/2023] Open
Abstract
Background: The location of coelomocyte proliferation in adult sea urchins is unknown and speculations since the early 1800s have been based on microanatomy and tracer uptake studies. In adult sea urchins (Strongylocentrotus purpuratus) with down-regulated immune systems, coelomocyte numbers increase in response to immune challenge, and whether some or all of these cells are newly proliferated is not known. The gene regulatory network that encodes transcription factors that control hematopoiesis in embryonic and larval sea urchins has not been investigated in adults. Hence, to identify the hematopoietic tissue in adult sea urchins, cell proliferation, expression of phagocyte specific genes, and expression of genes encoding transcription factors that function in the conserved regulatory network that controls hematopoiesis in embryonic and larval sea urchins were investigated for several tissues. Results: Cell proliferation was induced in adult sea urchins either by immune challenge through injection of heat-killed Vibrio diazotrophicus or by cell depletion through aspiration of coelomic fluid. In response to either of these stimuli, newly proliferated coelomocytes constitute only about 10% of the cells in the coelomic fluid. In tissues, newly proliferated cells and cells that express SpTransformer proteins (formerly Sp185/333) that are markers for phagocytes are present in the axial organ, gonad, pharynx, esophagus, and gut with no differences among tissues. The expression level of genes encoding transcription factors that regulate hematopoiesis show that both the axial organ and the pharynx have elevated expression compared to coelomocytes, esophagus, gut, and gonad. Similarly, an RNAseq dataset shows similar results for the axial organ and pharynx, but also suggests that the axial organ may be a site for removal and recycling of cells in the coelomic cavity. Conclusions: Results presented here are consistent with previous speculations that the axial organ may be a site of coelomocyte proliferation and that it may also be a center for cellular removal and recycling. A second site, the pharynx, may also have hematopoietic activity, a tissue that has been assumed to function only as part of the intestinal tract.
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Affiliation(s)
| | | | | | | | - L. Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC, United States
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10
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Chou HY, Lun CM, Smith LC. SpTransformer proteins from the purple sea urchin opsonize bacteria, augment phagocytosis, and retard bacterial growth. PLoS One 2018; 13:e0196890. [PMID: 29738524 PMCID: PMC5940198 DOI: 10.1371/journal.pone.0196890] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 04/20/2018] [Indexed: 01/05/2023] Open
Abstract
The purple sea urchin, Strongylocentrotus purpuratus, has a complex and robust immune system that is mediated by a number of multi-gene families including the SpTransformer (SpTrf) gene family (formerly Sp185/333). In response to immune challenge from bacteria and various pathogen-associated molecular patterns, the SpTrf genes are up-regulated in sea urchin phagocytes and express a diverse array of SpTrf proteins. We show here that SpTrf proteins from coelomocytes and isolated by nickel affinity (cNi-SpTrf) bind to Gram-positive and Gram-negative bacteria and to Baker's yeast, Saccharomyces cerevisiae, with saturable kinetics and specificity. cNi-SpTrf opsonization of the marine bacteria, Vibrio diazotrophicus, augments phagocytosis, however, opsonization by the recombinant protein, rSpTrf-E1, does not. Binding by cNi-SpTrf proteins retards growth rates significantly for several species of bacteria. SpTrf proteins, previously thought to be strictly membrane-associated, are secreted from phagocytes in short term cultures and bind V. diazotrophicus that are located both outside of and within phagocytes. Our results demonstrate anti-microbial activities of native SpTrf proteins and suggest variable functions among different SpTrf isoforms. Multiple isoforms may act synergistically to detect a wide array of pathogens and provide flexible and efficient host immunity.
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Affiliation(s)
- Hung-Yen Chou
- Department of Biological Sciences, George Washington University, Washington, DC, United States of America
| | - Cheng Man Lun
- Department of Biological Sciences, George Washington University, Washington, DC, United States of America
| | - L. Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC, United States of America
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11
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DeFilippo J, Ebersole J, Beck G. Comparison of phagocytosis in three Caribbean Sea urchins. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2018; 78:14-25. [PMID: 28916267 DOI: 10.1016/j.dci.2017.09.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 07/24/2017] [Accepted: 09/10/2017] [Indexed: 06/07/2023]
Abstract
In 1983 large numbers of the sea urchin Diadema antillarum unexplainably began showing signs of illness and dying in the Caribbean, and over the next year they came close to extinction, making it one of the worst mass mortality events on record. Present evidence suggests a water-borne pathogen as the etiological agent. Decades later Diadema densities remain low, and its near extinction has been a major factor in transforming living coral reefs in the Caribbean to barren algae-covered rock. In the ensuing decades, no solid explanation has been found to the questions: what killed Diadema; why did Diadema succumb while other species of urchins on the same reefs did not; and why has Diadema still not recovered? A recent hypothesis posited by our lab as to Diadema's vulnerability was directed at possible compromised immunity in Diadema, and experimental results found a significantly impaired humoral response to a key component of gram-negative bacteria. Here we use flow cytometry to examine the cellular arm of invertebrate immunity. We performed cytotoxicity and phagocytosis assays as a measure of the cellular immune responses of cells from Diadema and two other species of sea urchins not affected by the die-off. Despite our previous findings of in impaired humoral response, our study found no apparent difference in the cellular phagocytic response of Diadema compared to the other urchin species studied.
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Affiliation(s)
- John DeFilippo
- Department of Biology, University of Massachusetts at Boston, Boston, MA, 02125-3393, USA
| | - John Ebersole
- Department of Biology, University of Massachusetts at Boston, Boston, MA, 02125-3393, USA
| | - Gregory Beck
- Department of Biology, University of Massachusetts at Boston, Boston, MA, 02125-3393, USA.
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12
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Smith LC, Lun CM. The SpTransformer Gene Family (Formerly Sp185/333) in the Purple Sea Urchin and the Functional Diversity of the Anti-Pathogen rSpTransformer-E1 Protein. Front Immunol 2017; 8:725. [PMID: 28713368 PMCID: PMC5491942 DOI: 10.3389/fimmu.2017.00725] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 06/08/2017] [Indexed: 12/12/2022] Open
Abstract
The complex innate immune system of sea urchins is underpinned by several multigene families including the SpTransformer family (SpTrf; formerly Sp185/333) with estimates of ~50 members, although the family size is likely variable among individuals of Strongylocentrotus purpuratus. The genes are small with similar structure, are tightly clustered, and have several types of repeats in the second of two exons and that surround each gene. The density of repeats suggests that the genes are positioned within regions of genomic instability, which may be required to drive sequence diversification. The second exon encodes the mature protein and is composed of blocks of sequence called elements that are present in mosaics of defined element patterns and are the major source of sequence diversity. The SpTrf genes respond swiftly to immune challenge, but only a single gene is expressed per phagocyte. Many of the mRNAs appear to be edited and encode proteins with altered and/or missense sequence that are often truncated, of which some may be functional. The standard SpTrf protein structure is an N-terminal glycine-rich region, a central RGD motif, a histidine-rich region, and a C-terminal region. Function is predicted from a recombinant protein, rSpTransformer-E1 (rSpTrf-E1), which binds to Vibrio and Saccharomyces, but not to Bacillus, and binds tightly to lipopolysaccharide, β-1,3-glucan, and flagellin, but not to peptidoglycan. rSpTrf-E1 is intrinsically disordered but transforms to α helical structure in the presence of binding targets including lipopolysaccharide, which may underpin the characteristics of binding to multiple targets. SpTrf proteins associate with coelomocyte membranes, and rSpTrf-E1 binds specifically to phosphatidic acid (PA). When rSpTrf-E1 is bound to PA in liposome membranes, it induces morphological changes in liposomes that correlate with PA clustering and leakage of luminal contents, and it extracts or removes PA from the bilayer. The multitasking activities of rSpTrf-E1 infer multiple and perhaps overlapping activities for the hundreds of native SpTrf proteins that are produced by individual sea urchins. This likely generates a flexible and highly protective immune system for the sea urchin in its marine habitat that it shares with broad arrays of microbes that may be pathogens and opportunists.
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Affiliation(s)
- L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC, United States
| | - Cheng Man Lun
- Department of Biological Sciences, George Washington University, Washington, DC, United States
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13
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Lun CM, Bishop BM, Smith LC. Multitasking Immune Sp185/333 Protein, rSpTransformer-E1, and Its Recombinant Fragments Undergo Secondary Structural Transformation upon Binding Targets. THE JOURNAL OF IMMUNOLOGY 2017; 198:2957-2966. [PMID: 28242650 DOI: 10.4049/jimmunol.1601795] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 01/26/2017] [Indexed: 12/31/2022]
Abstract
The purple sea urchin, Strongylocentrotus purpuratus, expresses a diverse immune response protein family called Sp185/333. A recombinant Sp185/333 protein, previously called rSp0032, shows multitasking antipathogen binding ability, suggesting that the protein family mediates a flexible and effective immune response to multiple foreign cells. Bioinformatic analysis predicts that rSp0032 is intrinsically disordered, and its multiple binding characteristic suggests structural flexibility to adopt different conformations depending on the characteristics of the target. To address the flexibility and structural shifting hypothesis, circular dichroism analysis of rSp0032 suggests that it transforms from disordered (random coil) to α helical structure. This structural transformation may be the basis for the strong affinity between rSp0032 and several pathogen-associated molecular patterns. The N-terminal Gly-rich fragment of rSp0032 and the C-terminal His-rich fragment show unique transformations by either intensifying the α helical structure or changing from α helical to β strand depending on the solvents and molecules added to the buffer. Based on these results, we propose a name change from rSp0032 to rSpTransformer-E1 to represent its flexible structural conformations and its E1 element pattern. Given that rSpTransformer-E1 shifts its conformation in the presence of solvents and binding targets and that all Sp185/333 proteins are predicted to be disordered, many or all of these proteins may undergo structural transformation to enable multitasking binding activity toward a wide range of targets. Consequently, we also propose an overarching name change for the entire family from Sp185/333 proteins to SpTransformer proteins.
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Affiliation(s)
- Cheng Man Lun
- Department of Biological Sciences, George Washington University, Washington, DC 20052; and
| | - Barney M Bishop
- Department of Chemistry and Biochemistry, George Mason University, Manassas, VA 20110
| | - L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC 20052; and
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A recombinant Sp185/333 protein from the purple sea urchin has multitasking binding activities towards certain microbes and PAMPs. Immunobiology 2016; 221:889-903. [PMID: 27020848 DOI: 10.1016/j.imbio.2016.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/14/2016] [Accepted: 03/17/2016] [Indexed: 11/22/2022]
Abstract
The purple sea urchin, Strongylocentrotus purpuratus, possesses a sophisticated innate immune system that responds to microbes effectively by swift expression of the highly diverse Sp185/333 gene family. The Sp185/333 proteins are predicted to have anti-pathogen functions based on inducible gene expression and their significant sequence diversity. Sp185/333 proteins are all predicted to be intrinsically disordered and do not exhibit sequence similarities to other known proteins. To test the anti-pathogen hypothesis, a recombinant Sp185/333 protein, rSp0032, was evaluated and found to exhibit specific binding to marine Vibrio diazotrophicus and to Saccharomyces cerevisiae, but not to two Bacillus species. rSp0032 also binds to LPS, β-1,3-glucan and flagellin but not to peptidoglycan. rSp0032 binding to LPS can be competed by LPS, β-1,3-glucan and flagellin but not by peptidoglycan. We speculate that the predicted intrinsically disordered structure of rSp0032 may adapt to different conformations in binding to a limited number of PAMPs and pathogens. Given that rSp0032 binds to a range of targets, and that up to 260 different Sp185/333 proteins can be expressed per individual sea urchin, this family of immune response proteins may facilitate effective host protection against a broad array of potential pathogens encountered in the marine environment.
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15
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Karakostis K, Karakostis K, Costa C, Zito F, Matranga V. Heterologous expression of newly identified galectin-8 from sea urchin embryos produces recombinant protein with lactose binding specificity and anti-adhesive activity. Sci Rep 2015; 5:17665. [PMID: 26640155 PMCID: PMC4671058 DOI: 10.1038/srep17665] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 11/03/2015] [Indexed: 12/11/2022] Open
Abstract
Galectin family members specifically bind beta-galactoside derivatives and are involved in different cellular events, including cell communication, signalling, apoptosis, and immune responses. Here, we report a tandem-repeat type galectin from the Paracentrotus lividus sea urchin embryo, referred to as Pl-GAL-8. The 933nt sequence encodes a protein of 34.73 kDa, containing the conserved HFNPRF and WGxExR motifs in the two highly similar carbohydrate-recognition domains (CRD). The three-dimensional protein structure model of the N-CRD confirms the high evolutionary conservation of carbohydrate binding sites. The temporal gene expression is regulated during development and transcripts localize at the tip of the archenteron at gastrula stage, in a subset of the secondary mesenchyme cells that differentiate into blastocoelar (immune) cells. Functional studies using a recombinant Pl-GAL-8 expressed in bacteria demonstrate its hemo-agglutinating activity on human red blood cells through the binding to lactose, as well as its ability in inhibiting the adhesion of human Hep-G2 cells to the substrate. The recent implications in autoimmune diseases and inflammatory disorders make Gal-8 an attractive candidate for therapeutic purposes. Our results offer a solid basis for addressing the use of the new Pl-GAL-8 in functional and applicative studies, respectively in the developmental and biomedical fields.
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Affiliation(s)
| | - Kostantinos Karakostis
- Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare "A. Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy
| | - Caterina Costa
- Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare "A. Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy
| | - Francesca Zito
- Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare "A. Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy
| | - Valeria Matranga
- Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare "A. Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy
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16
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Sherman LS, Schrankel CS, Brown KJ, Smith LC. Extraordinary Diversity of Immune Response Proteins among Sea Urchins: Nickel-Isolated Sp185/333 Proteins Show Broad Variations in Size and Charge. PLoS One 2015; 10:e0138892. [PMID: 26406912 PMCID: PMC4583492 DOI: 10.1371/journal.pone.0138892] [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: 06/24/2015] [Accepted: 09/04/2015] [Indexed: 11/18/2022] Open
Abstract
Effective protection against pathogens requires the host to produce a wide range of immune effector proteins. The Sp185/333 gene family, which is expressed by the California purple sea urchin Strongylocentrotus purpuratus in response to bacterial infection, encodes a highly diverse repertoire of anti-pathogen proteins. A subset of these proteins can be isolated by affinity to metal ions based on multiple histidines, resulting in one to four bands of unique molecular weight on standard Western blots, which vary depending on the individual sea urchin. Two dimensional gel electrophoresis (2DE) of nickel-isolated protein samples followed by Western blot was employed to detect nickel-isolated Sp185/333 (Ni-Sp185/333) proteins and to evaluate protein diversity in animals before and after immune challenge with marine bacteria. Ni-Sp185/333 proteins of the same molecular weight on standard Western blots appear as a broad complex of variants that differ in pI on 2DE Western blots. The Ni-Sp185/333 protein repertoire is variable among animals, and shows a variety of changes among individual sea urchins in response to immune challenges with both the same and different species of bacteria. The extraordinary diversity of the Ni-Sp185/333 proteins may provide significant anti-pathogen capabilities for sea urchins that survive solely on innate immunity.
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Affiliation(s)
- Lauren S Sherman
- Department of Biological Sciences, George Washington University, Washington DC, United States of America
| | - Catherine S Schrankel
- Department of Biological Sciences, George Washington University, Washington DC, United States of America
| | - Kristy J Brown
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC, United States of America
| | - L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington DC, United States of America
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17
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Pinsino A, Matranga V. Sea urchin immune cells as sentinels of environmental stress. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2015; 49:198-205. [PMID: 25463510 DOI: 10.1016/j.dci.2014.11.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 11/14/2014] [Accepted: 11/17/2014] [Indexed: 06/04/2023]
Abstract
Echinoderms, an ancient and very successful phylum of marine invertebrates, play a central role in the maintenance of ecosystem integrity and are constantly exposed to environmental pressure, including: predation, changes in temperature and pH, hypoxia, pathogens, UV radiation, metals, toxicants, and emerging pollutants like nanomaterials. The annotation of the sea urchin genome, so closely related to humans and other vertebrate genomes, revealed an unusually complex immune system, which may be the basis for why sea urchins can adapt to different marine environments and survive even in hazardous conditions. In this review, we give a brief overview of the morphological features and recognized functions of echinoderm immune cells with a focus on studies correlating stress and immunity in the sea urchin. Immune cells from adult Paracentrotus lividus, which have been introduced in the last fifteen years as sentinels of environmental stress, are valid tools to uncover basic molecular and regulatory mechanisms of immune responses, supporting their use in immunological research. Here we summarize laboratory and field studies that reveal the amenability of sea urchin immune cells for toxicological testing.
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Affiliation(s)
- Annalisa Pinsino
- Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare "A. Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy.
| | - Valeria Matranga
- Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare "A. Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy.
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18
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Dishaw LJ, Cannon JP, Litman GW, Parker W. Immune-directed support of rich microbial communities in the gut has ancient roots. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 47:36-51. [PMID: 24984114 PMCID: PMC4146740 DOI: 10.1016/j.dci.2014.06.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 05/30/2014] [Accepted: 06/21/2014] [Indexed: 05/12/2023]
Abstract
The animal gut serves as a primary location for the complex host-microbe interplay that is essential for homeostasis and may also reflect the types of ancient selective pressures that spawned the emergence of immunity in metazoans. In this review, we present a phylogenetic survey of gut host-microbe interactions and suggest that host defense systems arose not only to protect tissue directly from pathogenic attack but also to actively support growth of specific communities of mutualists. This functional dichotomy resulted in the evolution of immune systems much more tuned for harmonious existence with microbes than previously thought, existing as dynamic but primarily cooperative entities in the present day. We further present the protochordate Ciona intestinalis as a promising model for studying gut host-bacterial dialogue. The taxonomic position, gut physiology and experimental tractability of Ciona offer unique advantages in dissecting host-microbe interplay and can complement studies in other model systems.
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Affiliation(s)
- Larry J Dishaw
- Department of Pediatrics, University of South Florida Morsani College of Medicine, USF/ACH Children's Research Institute, 140 7th Avenue South, St. Petersburg, FL 33701, USA.
| | - John P Cannon
- Department of Pediatrics, University of South Florida Morsani College of Medicine, USF/ACH Children's Research Institute, 140 7th Avenue South, St. Petersburg, FL 33701, USA
| | - Gary W Litman
- Department of Pediatrics, University of South Florida Morsani College of Medicine, USF/ACH Children's Research Institute, 140 7th Avenue South, St. Petersburg, FL 33701, USA; Department of Molecular Genetics, All Children's Hospital-Johns Hopkins Medicine, 501 6th Avenue South, St. Petersburg, FL 33701, USA
| | - William Parker
- Department of Surgery, Duke University Medical Center, Box 2605, Durham, NC 27710, USA
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Majeske AJ, Oren M, Sacchi S, Smith LC. Single sea urchin phagocytes express messages of a single sequence from the diverse Sp185/333 gene family in response to bacterial challenge. THE JOURNAL OF IMMUNOLOGY 2014; 193:5678-88. [PMID: 25355922 DOI: 10.4049/jimmunol.1401681] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Immune systems in animals rely on fast and efficient responses to a wide variety of pathogens. The Sp185/333 gene family in the purple sea urchin, Strongylocentrotus purpuratus, consists of an estimated 50 (±10) members per genome that share a basic gene structure but show high sequence diversity, primarily due to the mosaic appearance of short blocks of sequence called elements. The genes show significantly elevated expression in three subpopulations of phagocytes responding to marine bacteria. The encoded Sp185/333 proteins are highly diverse and have central effector functions in the immune system. In this study we report the Sp185/333 gene expression in single sea urchin phagocytes. Sea urchins challenged with heat-killed marine bacteria resulted in a typical increase in coelomocyte concentration within 24 h, which included an increased proportion of phagocytes expressing Sp185/333 proteins. Phagocyte fractions enriched from coelomocytes were used in limiting dilutions to obtain samples of single cells that were evaluated for Sp185/333 gene expression by nested RT-PCR. Amplicon sequences showed identical or nearly identical Sp185/333 amplicon sequences in single phagocytes with matches to six known Sp185/333 element patterns, including both common and rare element patterns. This suggested that single phagocytes show restricted expression from the Sp185/333 gene family and infers a diverse, flexible, and efficient response to pathogens. This type of expression pattern from a family of immune response genes in single cells has not been identified previously in other invertebrates.
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Affiliation(s)
- Audrey J Majeske
- Department of Biological Sciences, George Washington University, Washington, DC 20052
| | - Matan Oren
- Department of Biological Sciences, George Washington University, Washington, DC 20052
| | - Sandro Sacchi
- Department of Biological Sciences, George Washington University, Washington, DC 20052
| | - L Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, DC 20052
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Li C, Blencke HM, Haug T, Jørgensen Ø, Stensvåg K. Expression of antimicrobial peptides in coelomocytes and embryos of the green sea urchin (Strongylocentrotus droebachiensis). DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 43:106-113. [PMID: 24239709 DOI: 10.1016/j.dci.2013.10.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 10/28/2013] [Accepted: 10/29/2013] [Indexed: 06/02/2023]
Abstract
Antimicrobial peptides (AMPs) play a crucial role in innate immunity. We have previously reported the isolation and characterization of the AMPs, strongylocins 1 and 2, and centrocin 1, from coelomocyte extracts of Strongylocentrotus droebachiensis. Here we show that these AMPs were expressed in phagocytes. In addition, transcripts of strongylocin 1 were detected in vibratile cells and/or colorless spherule cells, while transcripts of strongylocin 2 were found in red spherule cells. Results from immunoblotting and immunocytochemistry studies showed that centrocin 1 was produced by phagocytes and stored in granular vesicles. Co-localization of centrocin 1 and phagocytosed bacteria suggests that the granular vesicles containing centrocin 1 may be involved in the formation of phagolysosomes. We also analyzed the temporal and spatial expression of AMPs throughout larval development. Strongylocins were expressed in the early pluteus stage, while centrocin 1 was expressed in the mid pluteus stage. The spatial expression pattern showed that centrocin 1 was mainly located in blastocoelar cells (BCs) around the stomach and the esophagus. In addition, a few patrolling BCs were detected in some larval arms. Together, these results suggest that AMPs are expressed in different types of coelomocytes and that centrocin 1 is involved in response against bacteria. Furthermore, the expression of AMPs in larval pluteus stage, especially in BCs, indicates that AMPs and BCs are engaged in the larval immune system.
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Affiliation(s)
- Chun Li
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, University of Tromsø, Breivika, N-9037 Tromsø, Norway; Centre for Research-based Innovation on Marine Bioactives and Drug Discovery (MabCent-SFI), University of Tromsø, N-9037 Tromsø, Norway.
| | - Hans-Matti Blencke
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, University of Tromsø, Breivika, N-9037 Tromsø, Norway; Centre for Research-based Innovation on Marine Bioactives and Drug Discovery (MabCent-SFI), University of Tromsø, N-9037 Tromsø, Norway
| | - Tor Haug
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, University of Tromsø, Breivika, N-9037 Tromsø, Norway; Centre for Research-based Innovation on Marine Bioactives and Drug Discovery (MabCent-SFI), University of Tromsø, N-9037 Tromsø, Norway
| | | | - Klara Stensvåg
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, University of Tromsø, Breivika, N-9037 Tromsø, Norway; Centre for Research-based Innovation on Marine Bioactives and Drug Discovery (MabCent-SFI), University of Tromsø, N-9037 Tromsø, Norway.
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21
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Majeske AJ, Bayne CJ, Smith LC. Aggregation of sea urchin phagocytes is augmented in vitro by lipopolysaccharide. PLoS One 2013; 8:e61419. [PMID: 23613847 PMCID: PMC3629189 DOI: 10.1371/journal.pone.0061419] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 03/13/2013] [Indexed: 01/05/2023] Open
Abstract
Development of protocols and media for culturing immune cells from marine invertebrates has not kept pace with advancements in mammalian immune cell culture, the latter having been driven by the need to understand the causes of and develop therapies for human and animal diseases. However, expansion of the aquaculture industry and the diseases that threaten these systems creates the need to develop cell and tissue culture methods for marine invertebrates. Such methods will enable us to better understand the causes of disease outbreaks and to develop means to avoid and remedy epidemics. We report a method for the short-term culture of phagocytes from the purple sea urchin, Strongylocentrotus purpuratus, by modifying an approach previously used to culture cells from another sea urchin species. The viability of cultured phagocytes from the purple sea urchin decreases from 91.6% to 57% over six days and phagocyte morphology changes from single cells to aggregates leading to the formation of syncytia-like structures. This process is accelerated in the presence of lipopolysaccharide suggesting that phagocytes are capable of detecting this molecular pattern in culture conditions. Sea urchin immune response proteins, called Sp185/333, are expressed on the surface of a subset of phagocytes and have been associated with syncytia-like structures. We evaluated their expression in cultured phagocytes to determine their possible role in cell aggregation and in the formation of syncytia-like structures. Between 0 and 3 hr, syncytia-like structures were observed in cultures when only ∼10% of the cells were positive for Sp185/333 proteins. At 24 hr, ∼90% of the nuclei were Sp185/333-positive when all of the phagocytes had aggregated into syncytia-like structures. Consequently, we conclude that the Sp185/333 proteins do not have a major role in initiating the aggregation of cultured phagocytes, however the Sp185/333 proteins are associated with the clustered nuclei within the syncytia-like structures.
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Affiliation(s)
- Audrey J. Majeske
- Department of Biological Sciences, George Washington University, Washington, D. C., United States of America
| | - Christopher J. Bayne
- Department of Zoology, Oregon State University, Corvallis, Oregon, United States of America
| | - L. Courtney Smith
- Department of Biological Sciences, George Washington University, Washington, D. C., United States of America
- * E-mail:
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