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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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OpaCEA-expressing N. gonorrhoeae are efficiently recognized and eliminated by human granulocytes via lamellipodia-like membrane protrusions. (A) Granulocytes were incubated with OpaCEA gonococci (Ngo OpaCEA) or nonopaque, piliated gonococci (Ngo Opa−), respectively. At the indicated times, the number of viable gonococci was determined and expressed as the percentage of the initial inoculum. The graph shows mean values ± SDs of a representative experiment done in triplicate. Equivalent results were obtained with granulocytes isolated from four different donors. (B–E) Pseudocolored scanning electron micrographs of granulocytes infected for 1 h with OpaCEA gonococci (B and C), nonopaque N. gonorrhoeae (D), or nonpathogenic N. cinerea (E).
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fig1: OpaCEA-expressing N. gonorrhoeae are efficiently recognized and eliminated by human granulocytes via lamellipodia-like membrane protrusions. (A) Granulocytes were incubated with OpaCEA gonococci (Ngo OpaCEA) or nonopaque, piliated gonococci (Ngo Opa−), respectively. At the indicated times, the number of viable gonococci was determined and expressed as the percentage of the initial inoculum. The graph shows mean values ± SDs of a representative experiment done in triplicate. Equivalent results were obtained with granulocytes isolated from four different donors. (B–E) Pseudocolored scanning electron micrographs of granulocytes infected for 1 h with OpaCEA gonococci (B and C), nonopaque N. gonorrhoeae (D), or nonpathogenic N. cinerea (E).

Mentions: Human granulocytes express three of the four CEACAM family members, namely CEACAM1, CEACAM3, and CEACAM6, that bind neisserial OpaCEA proteins (Fig. S2 A, available at http://www.jem.org/cgi/content/full/jem.20030204/DC1). Accordingly, primary granulocytes can efficiently recognize and eliminate OpaCEA N. gonorrhoeae in the absence of specific antibodies or complement (4, 16). Indeed, when OpaCEA gonococci were incubated with granulocytes at a 2:1 ratio, only ∼40% of the initial bacterial inoculum could be recovered after 90 min (Fig. 1 A). Nonopaque organisms were not recognized or eliminated (Fig. 1 A). Contact of granulocytes with OpaCEA N. gonorrhoeae stimulated the cells to produce reactive oxygen derivatives (Fig. S2 B) and to exhibit pronounced lamellipodia-like protrusions on the surface (Fig. 1, B and C). These membrane protrusions were involved in the engulfment of the bacteria (Fig. 1 C). In contrast, nonopaque gonococci only moderately stimulated the oxidative burst of the granulocytes (Fig. S2 B), and neither nonopaque gonococci nor nonpathogenic N. cinerea induced lamellipodia-like protrusions on the phagocyte surface, indicating that the observed responses were due to the OpaCEA–CEACAM interaction (Fig. 1, D and E). These results suggested that granulocytes express CEACAM family member(s) with phagocytic properties. This receptor(s) seems to transduce signals that stimulate bactericidal mechanisms resulting in elimination of CEACAM-binding bacteria. However, the identity of the CEACAM family member(s) responsible for these processes was unknown.


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)

OpaCEA-expressing N. gonorrhoeae are efficiently recognized and eliminated by human granulocytes via lamellipodia-like membrane protrusions. (A) Granulocytes were incubated with OpaCEA gonococci (Ngo OpaCEA) or nonopaque, piliated gonococci (Ngo Opa−), respectively. At the indicated times, the number of viable gonococci was determined and expressed as the percentage of the initial inoculum. The graph shows mean values ± SDs of a representative experiment done in triplicate. Equivalent results were obtained with granulocytes isolated from four different donors. (B–E) Pseudocolored scanning electron micrographs of granulocytes infected for 1 h with OpaCEA gonococci (B and C), nonopaque N. gonorrhoeae (D), or nonpathogenic N. cinerea (E).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1887732&req=5

fig1: OpaCEA-expressing N. gonorrhoeae are efficiently recognized and eliminated by human granulocytes via lamellipodia-like membrane protrusions. (A) Granulocytes were incubated with OpaCEA gonococci (Ngo OpaCEA) or nonopaque, piliated gonococci (Ngo Opa−), respectively. At the indicated times, the number of viable gonococci was determined and expressed as the percentage of the initial inoculum. The graph shows mean values ± SDs of a representative experiment done in triplicate. Equivalent results were obtained with granulocytes isolated from four different donors. (B–E) Pseudocolored scanning electron micrographs of granulocytes infected for 1 h with OpaCEA gonococci (B and C), nonopaque N. gonorrhoeae (D), or nonpathogenic N. cinerea (E).
Mentions: Human granulocytes express three of the four CEACAM family members, namely CEACAM1, CEACAM3, and CEACAM6, that bind neisserial OpaCEA proteins (Fig. S2 A, available at http://www.jem.org/cgi/content/full/jem.20030204/DC1). Accordingly, primary granulocytes can efficiently recognize and eliminate OpaCEA N. gonorrhoeae in the absence of specific antibodies or complement (4, 16). Indeed, when OpaCEA gonococci were incubated with granulocytes at a 2:1 ratio, only ∼40% of the initial bacterial inoculum could be recovered after 90 min (Fig. 1 A). Nonopaque organisms were not recognized or eliminated (Fig. 1 A). Contact of granulocytes with OpaCEA N. gonorrhoeae stimulated the cells to produce reactive oxygen derivatives (Fig. S2 B) and to exhibit pronounced lamellipodia-like protrusions on the surface (Fig. 1, B and C). These membrane protrusions were involved in the engulfment of the bacteria (Fig. 1 C). In contrast, nonopaque gonococci only moderately stimulated the oxidative burst of the granulocytes (Fig. S2 B), and neither nonopaque gonococci nor nonpathogenic N. cinerea induced lamellipodia-like protrusions on the phagocyte surface, indicating that the observed responses were due to the OpaCEA–CEACAM interaction (Fig. 1, D and E). These results suggested that granulocytes express CEACAM family member(s) with phagocytic properties. This receptor(s) seems to transduce signals that stimulate bactericidal mechanisms resulting in elimination of CEACAM-binding bacteria. However, the identity of the CEACAM family member(s) responsible for these processes was unknown.

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