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Granulocyte CEACAM3 is a phagocytic receptor of the innate immune system that mediates recognition and elimination of human-specific pathogens.

Schmitter T, Agerer F, Peterson L, Munzner P, Hauck CR - J. Exp. Med. (2004)

Bottom Line: CEACAM3- but not CEACAM6-mediated uptake is blocked by dominant-negative versions of the small GTPase Rac.Moreover, CEACAM3 engagement triggers membrane recruitment and increased GTP loading of Rac that are not observed upon bacterial binding to CEACAM6.Internalization and Rac stimulation are also inhibited by compromising the integrity of an immunoreceptor tyrosine-based activation motif (ITAM)-like sequence in the cytoplasmic tail of CEACAM3 or by interference with Src family protein tyrosine kinases that phosphorylate CEACAM3.

View Article: PubMed Central - PubMed

Affiliation: Zentrum für Infektionsforschung, Universität Würzburg, Röntgenring 11, 97070 Würzburg, Germany.

ABSTRACT
Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) are used by several human pathogens to anchor themselves to or invade host cells. Interestingly, human granulocytes express a specific isoform, CEACAM3, that participates together with CEACAM1 and CEACAM6 in the recognition of CEACAM-binding microorganisms. Here we show that CEACAM3 can direct efficient, opsonin-independent phagocytosis of CEACAM-binding Neisseria, Moraxella, and Haemophilus species. CEACAM3- but not CEACAM6-mediated uptake is blocked by dominant-negative versions of the small GTPase Rac. Moreover, CEACAM3 engagement triggers membrane recruitment and increased GTP loading of Rac that are not observed upon bacterial binding to CEACAM6. Internalization and Rac stimulation are also inhibited by compromising the integrity of an immunoreceptor tyrosine-based activation motif (ITAM)-like sequence in the cytoplasmic tail of CEACAM3 or by interference with Src family protein tyrosine kinases that phosphorylate CEACAM3. In contrast to interfering with CEACAM6, blockage of CEACAM3-mediated events reduces the ability of primary human granulocytes to internalize and eliminate CEACAM-binding bacteria, indicating an important role of CEACAM3 in the control of human-specific pathogens by the innate immune system.

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Transient expression of CEACAMs in 293 cells allows interaction with OpaCEA gonococci. (A) 293 cells were transfected with CEACAM1, CEACAM3, CEACAM6, or the empty expression vector (pcDNA). After 2 d, cells were infected with OpaCEA gonococci. At the indicated time points, the number of internalized bacteria was determined by gentamicin protection assays. The graph shows mean values ± SDs of three independent experiments done in triplicate. (B) Transfected 293 cells were infected with nonopaque (Opa−), nonopaque, piliated (Opa−/P+), or OpaCEA-expressing (OpaCEA) gonococci for 1 h and analyzed in gentamicin protection assays. The graph shows mean values ± SDs of two independent experiments done in triplicate.
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fig2: Transient expression of CEACAMs in 293 cells allows interaction with OpaCEA gonococci. (A) 293 cells were transfected with CEACAM1, CEACAM3, CEACAM6, or the empty expression vector (pcDNA). After 2 d, cells were infected with OpaCEA gonococci. At the indicated time points, the number of internalized bacteria was determined by gentamicin protection assays. The graph shows mean values ± SDs of three independent experiments done in triplicate. (B) Transfected 293 cells were infected with nonopaque (Opa−), nonopaque, piliated (Opa−/P+), or OpaCEA-expressing (OpaCEA) gonococci for 1 h and analyzed in gentamicin protection assays. The graph shows mean values ± SDs of two independent experiments done in triplicate.

Mentions: To study the contribution of specific CEACAM molecules to the internalization of CEACAM-binding bacteria, we took advantage of 293 cells that do not express members of the CEACAM family (Fig. S2, C and D; reference 25). Transfection of 293 cells with CEACAM1, CEACAM3, CEACAM6, or the empty control vector (pcDNA) resulted in the surface expression of the respective receptor in ∼70–80% of the cell population (Fig. S2 D). CEACAM-transfected cells supported strong attachment of OpaCEA N. gonorrhoeae (Fig. S2 E). In addition, CEACAM3 and CEACAM6 mediated internalization of OpaCEA gonococci within 30–60 min after infection (Fig. 2 A). In contrast, internalization mediated by CEACAM1 was <15% compared with CEACAM3, and more than 100-fold lower numbers of bacteria were recovered from control-transfected cells (pcDNA) (Fig. 2 A). Importantly, the internalization process via CEACAM3 and CEACAM6 depended on the correct phenotype of the bacteria, since nonopaque, piliated gonococci were barely taken up by these receptors (Fig. 2 B). These results indicated that both CEACAM3 and CEACAM6, but not CEACAM1, are able to mediate efficient internalization of OpaCEA gonococci when expressed in epithelial cells.


Granulocyte CEACAM3 is a phagocytic receptor of the innate immune system that mediates recognition and elimination of human-specific pathogens.

Schmitter T, Agerer F, Peterson L, Munzner P, Hauck CR - J. Exp. Med. (2004)

Transient expression of CEACAMs in 293 cells allows interaction with OpaCEA gonococci. (A) 293 cells were transfected with CEACAM1, CEACAM3, CEACAM6, or the empty expression vector (pcDNA). After 2 d, cells were infected with OpaCEA gonococci. At the indicated time points, the number of internalized bacteria was determined by gentamicin protection assays. The graph shows mean values ± SDs of three independent experiments done in triplicate. (B) Transfected 293 cells were infected with nonopaque (Opa−), nonopaque, piliated (Opa−/P+), or OpaCEA-expressing (OpaCEA) gonococci for 1 h and analyzed in gentamicin protection assays. The graph shows mean values ± SDs of two independent experiments done in triplicate.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC1887732&req=5

fig2: Transient expression of CEACAMs in 293 cells allows interaction with OpaCEA gonococci. (A) 293 cells were transfected with CEACAM1, CEACAM3, CEACAM6, or the empty expression vector (pcDNA). After 2 d, cells were infected with OpaCEA gonococci. At the indicated time points, the number of internalized bacteria was determined by gentamicin protection assays. The graph shows mean values ± SDs of three independent experiments done in triplicate. (B) Transfected 293 cells were infected with nonopaque (Opa−), nonopaque, piliated (Opa−/P+), or OpaCEA-expressing (OpaCEA) gonococci for 1 h and analyzed in gentamicin protection assays. The graph shows mean values ± SDs of two independent experiments done in triplicate.
Mentions: To study the contribution of specific CEACAM molecules to the internalization of CEACAM-binding bacteria, we took advantage of 293 cells that do not express members of the CEACAM family (Fig. S2, C and D; reference 25). Transfection of 293 cells with CEACAM1, CEACAM3, CEACAM6, or the empty control vector (pcDNA) resulted in the surface expression of the respective receptor in ∼70–80% of the cell population (Fig. S2 D). CEACAM-transfected cells supported strong attachment of OpaCEA N. gonorrhoeae (Fig. S2 E). In addition, CEACAM3 and CEACAM6 mediated internalization of OpaCEA gonococci within 30–60 min after infection (Fig. 2 A). In contrast, internalization mediated by CEACAM1 was <15% compared with CEACAM3, and more than 100-fold lower numbers of bacteria were recovered from control-transfected cells (pcDNA) (Fig. 2 A). Importantly, the internalization process via CEACAM3 and CEACAM6 depended on the correct phenotype of the bacteria, since nonopaque, piliated gonococci were barely taken up by these receptors (Fig. 2 B). These results indicated that both CEACAM3 and CEACAM6, but not CEACAM1, are able to mediate efficient internalization of OpaCEA gonococci when expressed in epithelial cells.

Bottom Line: CEACAM3- but not CEACAM6-mediated uptake is blocked by dominant-negative versions of the small GTPase Rac.Moreover, CEACAM3 engagement triggers membrane recruitment and increased GTP loading of Rac that are not observed upon bacterial binding to CEACAM6.Internalization and Rac stimulation are also inhibited by compromising the integrity of an immunoreceptor tyrosine-based activation motif (ITAM)-like sequence in the cytoplasmic tail of CEACAM3 or by interference with Src family protein tyrosine kinases that phosphorylate CEACAM3.

View Article: PubMed Central - PubMed

Affiliation: Zentrum für Infektionsforschung, Universität Würzburg, Röntgenring 11, 97070 Würzburg, Germany.

ABSTRACT
Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) are used by several human pathogens to anchor themselves to or invade host cells. Interestingly, human granulocytes express a specific isoform, CEACAM3, that participates together with CEACAM1 and CEACAM6 in the recognition of CEACAM-binding microorganisms. Here we show that CEACAM3 can direct efficient, opsonin-independent phagocytosis of CEACAM-binding Neisseria, Moraxella, and Haemophilus species. CEACAM3- but not CEACAM6-mediated uptake is blocked by dominant-negative versions of the small GTPase Rac. Moreover, CEACAM3 engagement triggers membrane recruitment and increased GTP loading of Rac that are not observed upon bacterial binding to CEACAM6. Internalization and Rac stimulation are also inhibited by compromising the integrity of an immunoreceptor tyrosine-based activation motif (ITAM)-like sequence in the cytoplasmic tail of CEACAM3 or by interference with Src family protein tyrosine kinases that phosphorylate CEACAM3. In contrast to interfering with CEACAM6, blockage of CEACAM3-mediated events reduces the ability of primary human granulocytes to internalize and eliminate CEACAM-binding bacteria, indicating an important role of CEACAM3 in the control of human-specific pathogens by the innate immune system.

Show MeSH
Related in: MedlinePlus