RTX cytotoxins recognize β
            <sub>2</sub>
            integrin receptors through N-linked oligosaccharides

Morová, Jana; Osička, Radim; Mašín, Jiří; Šebo, Peter

doi:10.1073/pnas.0711400105

Cited by 95 publications

(106 citation statements)

References 28 publications

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“…the specificity-determining loop segment is not required for formation of ␣5␤1, suggesting that use of subunit interface residues is variable among integrins (48). On the other hand, both the binding and killing of target cells by cytotoxins, such as CyaA, LtxA, and HlyA, depended on recognition of the N-glycans on ␤2 integrin (50).…”

Section: Discussionmentioning

confidence: 99%

N-Glycosylation of the I-like Domain of β1 Integrin Is Essential for β1 Integrin Expression and Biological Function

Isaji

Sato

Fukuda

et al. 2009

Journal of Biological Chemistry

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N-Glycosylation of integrin ␣5␤1 plays a crucial role in cell spreading, cell migration, ligand binding, and dimer formation, but the detailed mechanisms by which N-glycosylation mediates these functions remain unclear. In a previous study, we showed that three potential N-glycosylation sites (␣5S3-5) on the ␤-propeller of the ␣5 subunit are essential to the functional expression of the subunit. In particular, site 5 (␣5S5) is the most important for its expression on the cell surface. In this study, the function of the N-glycans on the integrin ␤1 subunit was investigated using sequential site-directed mutagenesis to remove the combined putative N-glycosylation sites. Removal of the N-glycosylation sites on the I-like domain of the ␤1 subunit (i.e. the ⌬4-6 mutant) decreased both the level of expression and heterodimeric formation, resulting in inhibition of cell spreading. Interestingly, cell spreading was observed only when the ␤1 subunit possessed these three N-glycosylation sites (i.e. the S4-6 mutant). Furthermore, the S4-6 mutant could form heterodimers with either ␣5S3-5 or ␣5S5 mutant of the ␣5 subunit. Taken together, the results of the present study reveal for the first time that N-glycosylation of the I-like domain of the ␤1 subunit is essential to both the heterodimer formation and biological function of the subunit. Moreover, because the ␣5S3-5/ ␤1S4-6 mutant represents the minimal N-glycosylation required for functional expression of the ␤1 subunit, it might also be useful for the study of molecular structures.Integrin is a heterodimeric glycoprotein that consists of both an ␣ and a ␤ subunit (1). The interaction between integrin and the extracellular matrix is essential to both physiologic and pathologic events, such as cell migration, development, cell viability, immune homeostasis, and tumorigenesis (2, 3). Among the integrin superfamily, ␤1 integrin can combine with 12 distinct ␣ subunits (␣1-11, ␣v) to form heterodimers, thereby acquiring a wide variety of ligand specificity (1, 4). Integrins are thought to be regulated by inside-out signaling mechanisms that provoke conformational changes, which modulate the affinity of integrin for the ligand (5). However, an increasing body of evidence suggests that cell-surface carbohydrates mediate a variety of interactions between integrin and its extracellular environment, thereby affecting integrin activity and possibly tumor metastasis as well (6 -8).Guo et al. (9) reported that an increase in ␤1-6-GlcNAc sugar chains on the integrin ␤1 subunit stimulated cell migration. In addition, elevated sialylation of the ␤1 subunit, because of Ras-induced STGal-I transferase activity, also induced cell migration (10, 11). Conversely, cell migration and spreading were reduced by the addition of a bisecting GlcNAc, which is a product of N-acetylglucosaminyltransferase III (GnT-III), 2 to the ␣5␤1 and ␣3␤1 integrins (12, 13). Alterations of N-glycans on integrins might also regulate their cis interactions with membrane-associated proteins, including the epidermal ...

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Section: Discussionmentioning

confidence: 99%

N-Glycosylation of the I-like Domain of β1 Integrin Is Essential for β1 Integrin Expression and Biological Function

Isaji

Sato

Fukuda

et al. 2009

Journal of Biological Chemistry

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“…LtxA interacts with clustered LFA-1, and this interaction may then stimulate an integrin signaling pathway. Morova et al (2008) recently reported that RTX toxins, including LtxA, recognize oligosaccharide subunits on LFA-1; however, LtxA was still partly active, even after the oligosaccharides were removed from WBCs with glycosidases, suggesting that either deglycosylation was not complete or that LtxA may recognize other entities as well. Bound LtxA destroys host cells by apoptosis (Mangan et al, 1991;Korostoff et al, 1998;Lally et al, 1999;Yamaguchi et al, 2001) or activation of caspase 1 through a process that differs from classic apoptosis (Kelk et al, 2003).…”

Section: Interaction With Host Cellsmentioning

confidence: 99%

Aggregatibacter actinomycetemcomitans Leukotoxin

2010

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Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium that colonizes the human oral cavity and is the causative agent for localized aggressive periodontitis (LAP), an aggressive form of periodontal disease that occurs in adolescents. A. actinomycetemcomitans secretes a protein toxin, leukotoxin (LtxA), which helps the bacterium evade the host immune response during infection. LtxA is a membrane-active toxin that specifically targets white blood cells (WBCs). In this review, we discuss recent developments in this field, including the identification and characterization of genes and proteins involved in secretion, regulation of LtxA, biosynthesis, newly described activities of LtxA, and how LtxA may be used as a therapy for the treatment of diseases.

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“…Upon initial interaction with N-linked oligosaccharides (31,32), CyaA specifically binds a loop outside the I domain of the CD11b subunit of the ␣ M ␤ 2 integrin (CR3) (5), and the toxin delivers the AC enzyme into phagocyte cytosol in two steps (33). Compelling indirect evidence suggests that the AC-translocating and pore-forming activities of CyaA are mutually independent and are accomplished by two distinct subpopulations of CyaA conformers that employ the same transmembrane CyaA segments in an alternative manner (34).…”

mentioning

confidence: 99%

Cyclic AMP-Elevating Capacity of Adenylate Cyclase Toxin-Hemolysin Is Sufficient for Lung Infection but Not for Full Virulence of Bordetella pertussis

et al. 2017

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The adenylate cyclase toxin-hemolysin (CyaA, ACT, or AC-Hly) of Bordetella pertussis targets phagocytic cells expressing the complement receptor 3 (CR3, Mac-1, ␣ M ␤ 2 integrin, or CD11b/CD18). CyaA delivers into cells an N-terminal adenylyl cyclase (AC) enzyme domain that is activated by cytosolic calmodulin and catalyzes unregulated conversion of cellular ATP into cyclic AMP (cAMP), a key second messenger subverting bactericidal activities of phagocytes. In parallel, the hemolysin (Hly) moiety of CyaA forms cation-selective hemolytic pores that permeabilize target cell membranes. We constructed the first B. pertussis mutant secreting a CyaA toxin having an intact capacity to deliver the AC enzyme into CD11b-expressing (CD11b ϩ ) host phagocytes but impaired in formation of cell-permeabilizing pores and defective in cAMP elevation in CD11b Ϫ cells. The nonhemolytic AC ϩ Hly Ϫ bacteria inhibited the antigen-presenting capacities of coincubated mouse dendritic cells in vitro and skewed their Toll-like receptor (TLR)-triggered maturation toward a tolerogenic phenotype. The AC ϩ Hly Ϫ mutant also infected mouse lungs as efficiently as the parental AC ϩ Hly ϩ strain. Hence, elevation of cAMP in CD11b Ϫ cells and/or the poreforming capacity of CyaA were not required for infection of mouse airways. The latter activities were, however, involved in bacterial penetration across the epithelial layer, enhanced neutrophil influx into lung parenchyma during sublethal infections, and the exacerbated lung pathology and lethality of B. pertussis infections at higher inoculation doses (Ͼ10 7 CFU/mouse). The pore-forming activity of CyaA further synergized with the cAMP-elevating activity in downregulation of major histocompatibility complex class II (MHC-II) molecules on infiltrating myeloid cells, likely contributing to immune subversion of host defenses by the whooping cough agent.KEYWORDS Bordetella pertussis, adenylate cyclase toxin-hemolysin, cAMP intoxication, lung colonization, pore-forming activity, virulence T he adenylate cyclase toxin-hemolysin is produced by all three Bordetella species pathogenic to mammals, and it plays a prominent role in the early phases of respiratory tract infection by the whooping cough agent, Bordetella pertussis (1-3). The toxin specifically binds the CD11b subunit of the complement receptor 3 (CR3) (4, 5) and exerts an array of immunosubversive and cytotoxic activities on myeloid phagocytes. CyaA delivers a cell-invasive adenylyl cyclase (AC) enzyme domain into cytosol of CD11b ϩ cells, where the AC is activated by calmodulin and converts cytosolic ATP to the signaling molecule cyclic AMP (cAMP). The generated supraphysiological levels of cAMP then nearly instantly ablate the bactericidal oxidative burst and opsonophago-

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RTX cytotoxins recognize β ₂ integrin receptors through N-linked oligosaccharides

Cited by 95 publications

References 28 publications

N-Glycosylation of the I-like Domain of β1 Integrin Is Essential for β1 Integrin Expression and Biological Function

N-Glycosylation of the I-like Domain of β1 Integrin Is Essential for β1 Integrin Expression and Biological Function

Aggregatibacter actinomycetemcomitans Leukotoxin

Cyclic AMP-Elevating Capacity of Adenylate Cyclase Toxin-Hemolysin Is Sufficient for Lung Infection but Not for Full Virulence of Bordetella pertussis

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RTX cytotoxins recognize β 2 integrin receptors through N-linked oligosaccharides

Cited by 95 publications

References 28 publications

N-Glycosylation of the I-like Domain of β1 Integrin Is Essential for β1 Integrin Expression and Biological Function

N-Glycosylation of the I-like Domain of β1 Integrin Is Essential for β1 Integrin Expression and Biological Function

Aggregatibacter actinomycetemcomitans Leukotoxin

Cyclic AMP-Elevating Capacity of Adenylate Cyclase Toxin-Hemolysin Is Sufficient for Lung Infection but Not for Full Virulence of Bordetella pertussis

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RTX cytotoxins recognize β ₂ integrin receptors through N-linked oligosaccharides