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TREM-2 (triggering receptor expressed on myeloid cells 2) is a phagocytic receptor for bacteria.

N'Diaye EN, Branda CS, Branda SS, Nevarez L, Colonna M, Lowell C, Hamerman JA, Seaman WE - J. Cell Biol. (2009)

Bottom Line: Internalization also requires src kinase activity and tyrosine phosphorylation.Finally, TREM-2-dependent phagocytosis is impaired in Syk-deficient macrophages.This study highlights a novel role for TREM-2-DAP12 in the immune response to bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Macrophage Biology Laboratory, San Francisco VA Medical Center, San Francisco, CA 94121, USA.

ABSTRACT
Phagocytosis, which is essential for the immune response to pathogens, is initiated by specific interactions between pathogens and cell surface receptors expressed by phagocytes. This study identifies triggering receptor expressed on myeloid cells 2 (TREM-2) and its signaling counterpart DAP12 as a molecular complex that promotes phagocytosis of bacteria. Expression of TREM-2-DAP12 enables nonphagocytic Chinese hamster ovary cells to internalize bacteria. This function depends on actin cytoskeleton dynamics and the activity of the small guanosine triphosphatases Rac and Cdc42. Internalization also requires src kinase activity and tyrosine phosphorylation. In bone marrow-derived macrophages, phagocytosis is decreased in the absence of DAP12 and can be restored by expression of TREM-2-DAP12. Depletion of TREM-2 inhibits both binding and uptake of bacteria. Finally, TREM-2-dependent phagocytosis is impaired in Syk-deficient macrophages. This study highlights a novel role for TREM-2-DAP12 in the immune response to bacterial pathogens.

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TREM-2–DAP12-mediated phagocytosis requires Rac1 and Cdc42 activity. (A) T2D12 cells were treated with C. difficile toxin B (Rho GTPase family inhibitor), LY29004 (PI-3 kinase inhibitor), or DNA–protein kinase inhibitor before phagocytosis of 594–E. coli. *, P < 0.05; **, P < 0.01 relative to untreated conditions. (B) Expression of dn Rho, Rac, or Cdc42 into T2D12 cells was verified by flow cytometry. Phagocytosis was analyzed as in A. **, P < 0.01; ***, P < 0.001 relative to vector-transfected cells. The graphs represent the mean of three experiments ± SEM.
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fig3: TREM-2–DAP12-mediated phagocytosis requires Rac1 and Cdc42 activity. (A) T2D12 cells were treated with C. difficile toxin B (Rho GTPase family inhibitor), LY29004 (PI-3 kinase inhibitor), or DNA–protein kinase inhibitor before phagocytosis of 594–E. coli. *, P < 0.05; **, P < 0.01 relative to untreated conditions. (B) Expression of dn Rho, Rac, or Cdc42 into T2D12 cells was verified by flow cytometry. Phagocytosis was analyzed as in A. **, P < 0.01; ***, P < 0.001 relative to vector-transfected cells. The graphs represent the mean of three experiments ± SEM.

Mentions: GTPases of the Rho family play essential roles in phagocytosis: rearrangement of actin-rich formations in the vicinity of the particle leads to its internalization by the surrounding membrane (Niedergang and Chavrier, 2005). Pretreatment of T2D12 cells with Clostridium difficile toxin B, an inhibitor of the Rho family of GTPases, reduced uptake of E. coli (Fig. 3 A). Consistent with this, phagocytosis was abrogated by inhibition of PI-3 kinase (Fig. 3 A), an activator of GTPases (Andrews et al., 2007) required for pseudopod extension during phagocytosis (Cox et al., 1999), but not by inhibition of DNA–protein kinase (Fig. 3 A). During phagocytosis, pseudopod formation and membrane expansion around the particle relies on Rac and Cdc42 (Caron and Hall, 1998), whereas formation of stress fibers beneath the bound particle and subsequent membrane retraction depend on Rho activity (Olazabal et al., 2002). The contribution of each GTPase to phagocytosis through TREM-2 was assessed through expression of dominant-negative (dn) constructs (Fig. 3 B). dn Rac1 and dn Cdc42 inhibited E. coli uptake, whereas dn RhoA had a marginal effect (Fig. 3 B). This shows a major role for Rac1 and Cdc42 and is consistent with electron micrographs showing pseudopod formation around bacteria (Fig. 1 D; Caron and Hall, 1998).


TREM-2 (triggering receptor expressed on myeloid cells 2) is a phagocytic receptor for bacteria.

N'Diaye EN, Branda CS, Branda SS, Nevarez L, Colonna M, Lowell C, Hamerman JA, Seaman WE - J. Cell Biol. (2009)

TREM-2–DAP12-mediated phagocytosis requires Rac1 and Cdc42 activity. (A) T2D12 cells were treated with C. difficile toxin B (Rho GTPase family inhibitor), LY29004 (PI-3 kinase inhibitor), or DNA–protein kinase inhibitor before phagocytosis of 594–E. coli. *, P < 0.05; **, P < 0.01 relative to untreated conditions. (B) Expression of dn Rho, Rac, or Cdc42 into T2D12 cells was verified by flow cytometry. Phagocytosis was analyzed as in A. **, P < 0.01; ***, P < 0.001 relative to vector-transfected cells. The graphs represent the mean of three experiments ± SEM.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2654305&req=5

fig3: TREM-2–DAP12-mediated phagocytosis requires Rac1 and Cdc42 activity. (A) T2D12 cells were treated with C. difficile toxin B (Rho GTPase family inhibitor), LY29004 (PI-3 kinase inhibitor), or DNA–protein kinase inhibitor before phagocytosis of 594–E. coli. *, P < 0.05; **, P < 0.01 relative to untreated conditions. (B) Expression of dn Rho, Rac, or Cdc42 into T2D12 cells was verified by flow cytometry. Phagocytosis was analyzed as in A. **, P < 0.01; ***, P < 0.001 relative to vector-transfected cells. The graphs represent the mean of three experiments ± SEM.
Mentions: GTPases of the Rho family play essential roles in phagocytosis: rearrangement of actin-rich formations in the vicinity of the particle leads to its internalization by the surrounding membrane (Niedergang and Chavrier, 2005). Pretreatment of T2D12 cells with Clostridium difficile toxin B, an inhibitor of the Rho family of GTPases, reduced uptake of E. coli (Fig. 3 A). Consistent with this, phagocytosis was abrogated by inhibition of PI-3 kinase (Fig. 3 A), an activator of GTPases (Andrews et al., 2007) required for pseudopod extension during phagocytosis (Cox et al., 1999), but not by inhibition of DNA–protein kinase (Fig. 3 A). During phagocytosis, pseudopod formation and membrane expansion around the particle relies on Rac and Cdc42 (Caron and Hall, 1998), whereas formation of stress fibers beneath the bound particle and subsequent membrane retraction depend on Rho activity (Olazabal et al., 2002). The contribution of each GTPase to phagocytosis through TREM-2 was assessed through expression of dominant-negative (dn) constructs (Fig. 3 B). dn Rac1 and dn Cdc42 inhibited E. coli uptake, whereas dn RhoA had a marginal effect (Fig. 3 B). This shows a major role for Rac1 and Cdc42 and is consistent with electron micrographs showing pseudopod formation around bacteria (Fig. 1 D; Caron and Hall, 1998).

Bottom Line: Internalization also requires src kinase activity and tyrosine phosphorylation.Finally, TREM-2-dependent phagocytosis is impaired in Syk-deficient macrophages.This study highlights a novel role for TREM-2-DAP12 in the immune response to bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Macrophage Biology Laboratory, San Francisco VA Medical Center, San Francisco, CA 94121, USA.

ABSTRACT
Phagocytosis, which is essential for the immune response to pathogens, is initiated by specific interactions between pathogens and cell surface receptors expressed by phagocytes. This study identifies triggering receptor expressed on myeloid cells 2 (TREM-2) and its signaling counterpart DAP12 as a molecular complex that promotes phagocytosis of bacteria. Expression of TREM-2-DAP12 enables nonphagocytic Chinese hamster ovary cells to internalize bacteria. This function depends on actin cytoskeleton dynamics and the activity of the small guanosine triphosphatases Rac and Cdc42. Internalization also requires src kinase activity and tyrosine phosphorylation. In bone marrow-derived macrophages, phagocytosis is decreased in the absence of DAP12 and can be restored by expression of TREM-2-DAP12. Depletion of TREM-2 inhibits both binding and uptake of bacteria. Finally, TREM-2-dependent phagocytosis is impaired in Syk-deficient macrophages. This study highlights a novel role for TREM-2-DAP12 in the immune response to bacterial pathogens.

Show MeSH
Related in: MedlinePlus