| Surfactant protein D interacts with alpha2-macroglobulin and increases its innate immune potential. | |
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MedLine Citation:
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PMID: 20207732 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Surfactant protein D (SP-D) is an innate immune collectin that recognizes microbes via its carbohydrate recognition domains, agglutinates bacteria, and forms immune complexes. During microbial infections, proteases, such as elastases, cleave the carbohydrate recognition domains and can inactivate the innate immune functions of SP-D. Host responses to counterbalance the reduction of SP-D-mediated innate immune response under these conditions are not clearly understood. We have unexpectedly identified that SP-D could interact with protein fractions containing ovomucin and ovomacroglobulin. Here, we show that SP-D interacts with human alpha(2)-macroglobulin (A2M), a protease inhibitor present in the lungs and serum. Using enzyme-linked immunosorbent assays, surface plasmon resonance, and carbohydrate competition assays, we show that SP-D interacts with A2M both in solid phase (K(D) of 7.33 nM) and in solution via lectin-carbohydrate interactions under physiological calcium conditions. Bacterial agglutination assays further show that SP-D x A2M complexes increase the ability of SP-D to agglutinate bacteria. Western blot analyses show that SP-D, but not A2M, avidly binds bacteria. Interestingly, intact and activated A2M also protect SP-D against elastase-mediated degradation, and the cleaved A2M still interacts with SP-D and is able to enhance its agglutination abilities. We also found that SP-D and A2M can interact with each other in the airway-lining fluid. Therefore, we propose that SP-D utilizes a novel mechanism in which the collectin interacts with protease inhibitor A2M to decrease its degradation and to concurrently increase its innate immune function. These interactions particularly enhance bacterial agglutination and immune complex formation. |
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Authors:
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Hayley A Craig-Barnes; Barbara S Doumouras; Nades Palaniyar |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2010-03-05 |
Journal Detail:
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Title: The Journal of biological chemistry Volume: 285 ISSN: 1083-351X ISO Abbreviation: J. Biol. Chem. Publication Date: 2010 Apr |
Date Detail:
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Created Date: 2010-04-26 Completed Date: 2010-05-27 Revised Date: 2011-07-28 |
Medline Journal Info:
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Nlm Unique ID: 2985121R Medline TA: J Biol Chem Country: United States |
Other Details:
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Languages: eng Pagination: 13461-70 Citation Subset: IM |
Affiliation:
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Lung Innate Immunity Research Laboratory, Program in Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Agglutination Escherichia coli / chemistry, immunology* Humans Immunity, Innate / physiology* Lung / chemistry, immunology, metabolism Pancreatic Elastase / antagonists & inhibitors, chemistry, immunology, metabolism Protein Binding / physiology Pulmonary Surfactant-Associated Protein D / chemistry, immunology*, metabolism alpha-Macroglobulins / chemistry, immunology*, metabolism* |
| Grant Support | |
ID/Acronym/Agency:
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MOP-84312//Canadian Institutes of Health Research |
| Chemical | |
Reg. No./Substance:
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0/Pulmonary Surfactant-Associated Protein D; 0/alpha-Macroglobulins; EC 3.4.21.36/Pancreatic Elastase |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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