Characterization of Sialic Acid-Binding Immunoglobulin-Type Lectins in Fish Reveals Teleost-Specific Structures and Expression Patterns.

Kim F Bornhöfft,Marzia T Venuto,Torsten Viergutz,Alexander Rebl,Sebastian P Galuska,Joan Martorell Ribera,Ulrike Gimsa

doi:10.3390/cells9040836

Kim F Bornhöfft, Marzia T Venuto + Show 5 more

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https://doi.org/10.3390/cells9040836

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Journal: Cells	Publication Date: Mar 31, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Research Institute for Farm Animal Biology (FBN)

Abstract

The cellular glycocalyx of vertebrates is frequently decorated with sialic acid residues. These sialylated structures are recognized by sialic acid-binding immunoglobulin-type lectins (Siglecs) of immune cells, which modulate their responsiveness. Fifteen Siglecs are known to be expressed in humans, but only four Siglecs are regularly present in fish: Siglec1, CD22, myelin-associated glycoprotein (MAG), and Siglec15. While several studies have dealt with the physiological roles of these four Siglecs in mammals, little is known about Siglecs in fish. In the present manuscript, the expression landscapes of these Siglecs were determined in the two salmonid species Oncorhynchus mykiss and Coregonus maraena and in the percid fish Sander lucioperca. This gene-expression profiling revealed that the expression of MAG is not restricted to neuronal cells but is detectable in all analyzed blood cells, including erythrocytes. The teleostean MAG contains the inhibitory motif ITIM; therefore, an additional immunomodulatory function of MAG is likely to be present in fish. Besides MAG, Siglec1, CD22, and Siglec15 were also expressed in all analyzed blood cell populations. Interestingly, the expression profiles of genes encoding Siglecs and particular associated enzymes changed in a gene- and tissue-specific manner when Coregonus maraena was exposed to handling stress. Thus, the obtained data indicate once more that stress directly affects immune-associated processes.

Highlights

Innate immunity is of even more paramount importance for fish health than adaptive immune mechanisms [1]
Siglec1 is mainly expressed on those immune cells, since it has been reported that mammalian Siglec1 is highly expressed on splenic and lymph-node macrophages [9,13]
Our quantitative PCR (qPCR) analyses suggested that the basal gene-expression patterns of Siglec1, CD22, myelin-associated glycoprotein (MAG), and

Summary

Introduction

Innate immunity is of even more paramount importance for fish health than adaptive immune mechanisms [1]. More than 50 regulators of innate immunity are known in fish today [2]; these regulators maintain the balance between pathogen defense and pathophysiological manifestations. Some of these innate-immune regulators recognize self-associated molecular patterns (SAMPs), a heterogeneous group of molecules that stimulate inhibitory receptors to dampen immune responses [3,4,5]. The family of sialic acids consists of more than 50 members [6] and belongs to the group of SAMPs [7]. Sialic acids are frequently located at the terminal ends of glycans on glycoproteins and the glycolipids that coat all mammalian cells in a glycocalyx.

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