Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity

ABSTRACT Annexin A5 (AnxA5) has a high affinity for phosphatidylserine. The protein is widely used to detect apoptotic cells because phosphatidylserine, a phospholipid that is normally present in the inner leaflets of cytoplasmic membranes, becomes translocated to the outer leaflets during programme...

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Autores principales:	Jacob H. Rand, Xiao-Xuan Wu, Elaine Y. Lin, Alexander Griffel, Philip Gialanella, John C. McKitrick
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2012
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/60f1eadfa7ea484791554d32e3f0ec0d
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spelling	oai:doaj.org-article:60f1eadfa7ea484791554d32e3f0ec0d2021-11-15T15:39:08ZAnnexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity10.1128/mBio.00292-112150-7511https://doaj.org/article/60f1eadfa7ea484791554d32e3f0ec0d2012-05-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00292-11https://doaj.org/toc/2150-7511ABSTRACT Annexin A5 (AnxA5) has a high affinity for phosphatidylserine. The protein is widely used to detect apoptotic cells because phosphatidylserine, a phospholipid that is normally present in the inner leaflets of cytoplasmic membranes, becomes translocated to the outer leaflets during programmed cell death. Here we report the novel observation that AnxA5 binds to Gram-negative bacteria via the lipid A domain of lipopolysaccharide (LPS). Binding of AnxA5 to bacteria was measured quantitatively, confirmed by fluorescence microscopy, and found to be inhibited by antibodies against lipid A. AnxA5 also bound to purified dot-blotted LPS and lipid A. Through ellipsometry, we found that the binding of AnxA5 to purified LPS was calcium dependent and rapid and showed a high affinity—characteristics similar to those of AnxA5 binding to phosphatidylserine. Initial functional studies indicated that AnxA5 can affect LPS activities. AnxA5 inhibited LPS-mediated gelation in the Limulus amebocyte lysate assay. Incubation of LPS with the protein reduced the quantity of tumor necrosis factor alpha (TNF-α) released by cultured monocytes compared to that released upon incubation with LPS alone. Initial in vivo experiments indicated that injection of mice with LPS preincubated with AnxA5 produced serum TNF-α levels lower than those seen after injection of LPS alone. These data demonstrate that AnxA5 binds to LPS and open paths to investigation of the potential biological and therapeutic implications of this interaction. IMPORTANCE AnxA5 is highly expressed in cells that have a barrier function—including, among others, vascular endothelium, placental trophoblasts, and epithelial cells lining bile ducts, renal tubules, mammary ducts, and nasal epithelium. The protein has been well characterized for its binding to phospholipid bilayers that contain phosphatidylserine. This report of a previously unrecognized activity of AnxA5 opens the door to investigation of the possibility that this binding may have biological and therapeutic ramifications. In view of the tissue expression of the protein, the present results suggest the possibility that AnxA5 plays a role in modulating the host defense against lipopolysaccharide at these anatomic sites, where cells may interface with microorganisms. These results also raise the intriguing possibility that AnxA5 or analogous proteins or peptides could provide novel approaches to addressing the difficult clinical problem of Gram-negative sepsis.Jacob H. RandXiao-Xuan WuElaine Y. LinAlexander GriffelPhilip GialanellaJohn C. McKitrickAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 3, Iss 2 (2012)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Jacob H. Rand Xiao-Xuan Wu Elaine Y. Lin Alexander Griffel Philip Gialanella John C. McKitrick Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
description	ABSTRACT Annexin A5 (AnxA5) has a high affinity for phosphatidylserine. The protein is widely used to detect apoptotic cells because phosphatidylserine, a phospholipid that is normally present in the inner leaflets of cytoplasmic membranes, becomes translocated to the outer leaflets during programmed cell death. Here we report the novel observation that AnxA5 binds to Gram-negative bacteria via the lipid A domain of lipopolysaccharide (LPS). Binding of AnxA5 to bacteria was measured quantitatively, confirmed by fluorescence microscopy, and found to be inhibited by antibodies against lipid A. AnxA5 also bound to purified dot-blotted LPS and lipid A. Through ellipsometry, we found that the binding of AnxA5 to purified LPS was calcium dependent and rapid and showed a high affinity—characteristics similar to those of AnxA5 binding to phosphatidylserine. Initial functional studies indicated that AnxA5 can affect LPS activities. AnxA5 inhibited LPS-mediated gelation in the Limulus amebocyte lysate assay. Incubation of LPS with the protein reduced the quantity of tumor necrosis factor alpha (TNF-α) released by cultured monocytes compared to that released upon incubation with LPS alone. Initial in vivo experiments indicated that injection of mice with LPS preincubated with AnxA5 produced serum TNF-α levels lower than those seen after injection of LPS alone. These data demonstrate that AnxA5 binds to LPS and open paths to investigation of the potential biological and therapeutic implications of this interaction. IMPORTANCE AnxA5 is highly expressed in cells that have a barrier function—including, among others, vascular endothelium, placental trophoblasts, and epithelial cells lining bile ducts, renal tubules, mammary ducts, and nasal epithelium. The protein has been well characterized for its binding to phospholipid bilayers that contain phosphatidylserine. This report of a previously unrecognized activity of AnxA5 opens the door to investigation of the possibility that this binding may have biological and therapeutic ramifications. In view of the tissue expression of the protein, the present results suggest the possibility that AnxA5 plays a role in modulating the host defense against lipopolysaccharide at these anatomic sites, where cells may interface with microorganisms. These results also raise the intriguing possibility that AnxA5 or analogous proteins or peptides could provide novel approaches to addressing the difficult clinical problem of Gram-negative sepsis.
format	article
author	Jacob H. Rand Xiao-Xuan Wu Elaine Y. Lin Alexander Griffel Philip Gialanella John C. McKitrick
author_facet	Jacob H. Rand Xiao-Xuan Wu Elaine Y. Lin Alexander Griffel Philip Gialanella John C. McKitrick
author_sort	Jacob H. Rand
title	Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
title_short	Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
title_full	Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
title_fullStr	Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
title_full_unstemmed	Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity
title_sort	annexin a5 binds to lipopolysaccharide and reduces its endotoxin activity
publisher	American Society for Microbiology
publishDate	2012
url	https://doaj.org/article/60f1eadfa7ea484791554d32e3f0ec0d
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Annexin A5 Binds to Lipopolysaccharide and Reduces Its Endotoxin Activity

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