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Siglec-5 and Siglec-14 are polymorphic paired receptors that modulate neutrophil and amnion signaling responses to group B Streptococcus.

Ali SR, Fong JJ, Carlin AF, Busch TD, Linden R, Angata T, Areschoug T, Parast M, Varki N, Murray J, Nizet V, Varki A - J. Exp. Med. (2014)

Bottom Line: GBS amnion immune activation was likewise influenced by the SIGLEC14- polymorphism.We provide initial evidence that the polymorphism could influence the risk of prematurity among human fetuses of mothers colonized with GBS.This first functionally proven example of a paired receptor system in the Siglec family has multiple implications for regulation of host immunity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, Department of Pediatrics, Department of Pathology, Department of Medicine, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, Department of Pediatrics, Department of Pathology, Department of Medicine, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, Department of Pediatrics, Department of Pathology, Department of Medicine, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093.

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The Siglec-5/14 genotype influences primary human monocyte responses to LPS and GBS. (A) Pictorial representation of SIGLEC-14/5 polymorphism in humans. Highly similar regions of SIGLEC14 and SIGLEC5 resulted in the generation of a SIGLEC14/5 fusion gene, leading to deletion of SIGLEC14 and expression of SIGLEC5 under the SIGLEC14 promoter. (B) Human blood monocytes of the indicated genotypes were left unstimulated (Ctrl) or stimulated with 10 ng/ml LPS, and TNF protein release was measured at 6 h by ELISA. (C) Human blood monocytes of the indicated genotypes were left uninfected (Ctrl) or infected with GBS at MOI = 10, and TNF protein release was measured at 6 h by ELISA. (D) Human monocytes of the indicated genotypes were left uninfected or infected with GBS or GBSΔβ for the indicated times and then lysed and analyzed for phosphorylation of p38 MAPK and IκB-α degradation by immunoblot. The p-p38/actin and IκB-α/actin (×10) densitometry values are shown on corresponding blots. Data in B–D are representative of two to four independent experiments with one to three different donors per genotype in each experiment. Results are means ± SD; *, P < 0.05.
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fig2: The Siglec-5/14 genotype influences primary human monocyte responses to LPS and GBS. (A) Pictorial representation of SIGLEC-14/5 polymorphism in humans. Highly similar regions of SIGLEC14 and SIGLEC5 resulted in the generation of a SIGLEC14/5 fusion gene, leading to deletion of SIGLEC14 and expression of SIGLEC5 under the SIGLEC14 promoter. (B) Human blood monocytes of the indicated genotypes were left unstimulated (Ctrl) or stimulated with 10 ng/ml LPS, and TNF protein release was measured at 6 h by ELISA. (C) Human blood monocytes of the indicated genotypes were left uninfected (Ctrl) or infected with GBS at MOI = 10, and TNF protein release was measured at 6 h by ELISA. (D) Human monocytes of the indicated genotypes were left uninfected or infected with GBS or GBSΔβ for the indicated times and then lysed and analyzed for phosphorylation of p38 MAPK and IκB-α degradation by immunoblot. The p-p38/actin and IκB-α/actin (×10) densitometry values are shown on corresponding blots. Data in B–D are representative of two to four independent experiments with one to three different donors per genotype in each experiment. Results are means ± SD; *, P < 0.05.

Mentions: Based on the in vitro THP-1 experiments, we hypothesized that the human-specific SIGLEC14/5 gene polymorphism could influence the responsiveness of primary human monocytes to infectious agents. The 5′ regions of SIGLEC5 and SIGLEC14 exhibit high similarity as the result of ongoing gene conversion, and in some individuals, the two are fused into a single gene that encodes for a functionally Siglec-5 gene product expressed under the SIGLEC14 promoter (Fig. 2 A; Yamanaka et al., 2009). The homozygous state of this allele is hereafter referred to as Sig-14−/−, whereas the homozygous state of the ancestral WT alleles carrying Siglec-5 and Siglec-14 is denoted as Sig-14+/+. Genotype analysis of blood cells was performed and analyzed as described previously (Yamanaka et al., 2009), and cells from three to four donors with homozygous genotypes were used in this study; separate experiments were performed with each donor sample. Primary monocytes from Sig-14+/+ individuals showed elevated TNF production compared with monocytes from Sig-14−/− individuals after challenge with LPS (Fig. 2 B) or GBS (Fig. 2 C). To investigate the role of Siglec-5 and Siglec-14 in primary human monocytes, Sig-14+/+ and Sig-14−/− cells were infected with GBS at an MOI of 10; GBSΔβ infections served as negative control for β-protein–mediated effects. We observed increased p-p38 activation in Sig-14+/+ cells with WT versus mutant GBS infection, likely because of activation of Siglec-14 by WT bacteria. Indeed, as predicted, p-p38 activation was reduced in Sig-14−/− cells with WT versus mutant GBS infection (Fig. 2 D). Moreover, unlike in THP-1 cells (Fig. 1 F), we also observed a moderate increase in NF-κB activation, as indicated by the disappearance of IκB-α in GBS-exposed Sig-14+/+ compared with Sig-14−/− monocytes; GBSΔβ induced similar NF-κB activation in cells of both genotypes (Fig. 2 D). Collectively, results from THP-1 cells (Fig. 1) and from monocytes from healthy human donors without or with SIGLEC14/5 polymorphism (Fig. 2) indicate that Siglec-14 promotes proinflammatory responses to LPS and GBS through activation of AKT and/or p38 MAPK pathways, thus providing an opposing force to Siglec-5, which acts via a cytosolic ITIM motif that recruits the tyrosine phosphatases SHP-1 and SHP-2 (Carlin et al., 2009a).


Siglec-5 and Siglec-14 are polymorphic paired receptors that modulate neutrophil and amnion signaling responses to group B Streptococcus.

Ali SR, Fong JJ, Carlin AF, Busch TD, Linden R, Angata T, Areschoug T, Parast M, Varki N, Murray J, Nizet V, Varki A - J. Exp. Med. (2014)

The Siglec-5/14 genotype influences primary human monocyte responses to LPS and GBS. (A) Pictorial representation of SIGLEC-14/5 polymorphism in humans. Highly similar regions of SIGLEC14 and SIGLEC5 resulted in the generation of a SIGLEC14/5 fusion gene, leading to deletion of SIGLEC14 and expression of SIGLEC5 under the SIGLEC14 promoter. (B) Human blood monocytes of the indicated genotypes were left unstimulated (Ctrl) or stimulated with 10 ng/ml LPS, and TNF protein release was measured at 6 h by ELISA. (C) Human blood monocytes of the indicated genotypes were left uninfected (Ctrl) or infected with GBS at MOI = 10, and TNF protein release was measured at 6 h by ELISA. (D) Human monocytes of the indicated genotypes were left uninfected or infected with GBS or GBSΔβ for the indicated times and then lysed and analyzed for phosphorylation of p38 MAPK and IκB-α degradation by immunoblot. The p-p38/actin and IκB-α/actin (×10) densitometry values are shown on corresponding blots. Data in B–D are representative of two to four independent experiments with one to three different donors per genotype in each experiment. Results are means ± SD; *, P < 0.05.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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fig2: The Siglec-5/14 genotype influences primary human monocyte responses to LPS and GBS. (A) Pictorial representation of SIGLEC-14/5 polymorphism in humans. Highly similar regions of SIGLEC14 and SIGLEC5 resulted in the generation of a SIGLEC14/5 fusion gene, leading to deletion of SIGLEC14 and expression of SIGLEC5 under the SIGLEC14 promoter. (B) Human blood monocytes of the indicated genotypes were left unstimulated (Ctrl) or stimulated with 10 ng/ml LPS, and TNF protein release was measured at 6 h by ELISA. (C) Human blood monocytes of the indicated genotypes were left uninfected (Ctrl) or infected with GBS at MOI = 10, and TNF protein release was measured at 6 h by ELISA. (D) Human monocytes of the indicated genotypes were left uninfected or infected with GBS or GBSΔβ for the indicated times and then lysed and analyzed for phosphorylation of p38 MAPK and IκB-α degradation by immunoblot. The p-p38/actin and IκB-α/actin (×10) densitometry values are shown on corresponding blots. Data in B–D are representative of two to four independent experiments with one to three different donors per genotype in each experiment. Results are means ± SD; *, P < 0.05.
Mentions: Based on the in vitro THP-1 experiments, we hypothesized that the human-specific SIGLEC14/5 gene polymorphism could influence the responsiveness of primary human monocytes to infectious agents. The 5′ regions of SIGLEC5 and SIGLEC14 exhibit high similarity as the result of ongoing gene conversion, and in some individuals, the two are fused into a single gene that encodes for a functionally Siglec-5 gene product expressed under the SIGLEC14 promoter (Fig. 2 A; Yamanaka et al., 2009). The homozygous state of this allele is hereafter referred to as Sig-14−/−, whereas the homozygous state of the ancestral WT alleles carrying Siglec-5 and Siglec-14 is denoted as Sig-14+/+. Genotype analysis of blood cells was performed and analyzed as described previously (Yamanaka et al., 2009), and cells from three to four donors with homozygous genotypes were used in this study; separate experiments were performed with each donor sample. Primary monocytes from Sig-14+/+ individuals showed elevated TNF production compared with monocytes from Sig-14−/− individuals after challenge with LPS (Fig. 2 B) or GBS (Fig. 2 C). To investigate the role of Siglec-5 and Siglec-14 in primary human monocytes, Sig-14+/+ and Sig-14−/− cells were infected with GBS at an MOI of 10; GBSΔβ infections served as negative control for β-protein–mediated effects. We observed increased p-p38 activation in Sig-14+/+ cells with WT versus mutant GBS infection, likely because of activation of Siglec-14 by WT bacteria. Indeed, as predicted, p-p38 activation was reduced in Sig-14−/− cells with WT versus mutant GBS infection (Fig. 2 D). Moreover, unlike in THP-1 cells (Fig. 1 F), we also observed a moderate increase in NF-κB activation, as indicated by the disappearance of IκB-α in GBS-exposed Sig-14+/+ compared with Sig-14−/− monocytes; GBSΔβ induced similar NF-κB activation in cells of both genotypes (Fig. 2 D). Collectively, results from THP-1 cells (Fig. 1) and from monocytes from healthy human donors without or with SIGLEC14/5 polymorphism (Fig. 2) indicate that Siglec-14 promotes proinflammatory responses to LPS and GBS through activation of AKT and/or p38 MAPK pathways, thus providing an opposing force to Siglec-5, which acts via a cytosolic ITIM motif that recruits the tyrosine phosphatases SHP-1 and SHP-2 (Carlin et al., 2009a).

Bottom Line: GBS amnion immune activation was likewise influenced by the SIGLEC14- polymorphism.We provide initial evidence that the polymorphism could influence the risk of prematurity among human fetuses of mothers colonized with GBS.This first functionally proven example of a paired receptor system in the Siglec family has multiple implications for regulation of host immunity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, Department of Pediatrics, Department of Pathology, Department of Medicine, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, Department of Pediatrics, Department of Pathology, Department of Medicine, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093Glycobiology Research and Training Center, Department of Cellular and Molecular Medicine, Department of Pediatrics, Department of Pathology, Department of Medicine, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093.

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Related in: MedlinePlus