Limits...
Two C-type lectins cooperate to defend Anopheles gambiae against Gram-negative bacteria.

Schnitger AK, Yassine H, Kafatos FC, Osta MA - J. Biol. Chem. (2009)

Bottom Line: Although studies in insects and other invertebrates have described CTL activation of effector immune responses in vitro, the contribution of these CTLs to immune defenses in vivo is still poorly understood.Silencing either CTL dramatically reduces mosquito survival to Gram-negative but not to Gram-positive bacterial infections, suggesting a role in defense against Gram-negative bacteria.Apparently, CTL4 and CTLMA2 serve pleiotropic functions in the innate immune response of A. gambiae.

View Article: PubMed Central - PubMed

Affiliation: Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.

ABSTRACT
C-type lectins (CTLs) are a family of proteins that share a common structural motif, the carbohydrate recognition domain, and may act as receptors in pathogen recognition. Indeed, some vertebrate CTLs, particularly the collectins, are unequivocally implicated in the innate immune response to certain microbes. Although studies in insects and other invertebrates have described CTL activation of effector immune responses in vitro, the contribution of these CTLs to immune defenses in vivo is still poorly understood. Here we report that two CTLs, CTL4 and CTLMA2, which were shown previously to inhibit Plasmodium berghei ookinete melanization in the malaria vector Anopheles gambiae, are transcriptionally induced by bacterial challenge. Using in vivo reverse genetic analysis, we show that both CTLs are required for the clearance of Escherichia coli, but not Staphylococcus aureus, from adult female mosquitoes. Silencing either CTL dramatically reduces mosquito survival to Gram-negative but not to Gram-positive bacterial infections, suggesting a role in defense against Gram-negative bacteria. Furthermore, molecular characterization reveals that both CTLs are secreted into the mosquito hemolymph mainly in the form of a disulfide-linked heterodimer. This association explains the similar roles of these CTLs in bacterial defense as well as in the melanization response to P. berghei ookinetes. Apparently, CTL4 and CTLMA2 serve pleiotropic functions in the innate immune response of A. gambiae.

Show MeSH

Related in: MedlinePlus

Transcript levels of CTL4 and CTLMA2 in whole mosquitoes. Analysis of transcript levels was performed by qRT-PCR in mosquitoes injected with E. coli (gray), S. aureus (black), or sterile PBS (control, white) at the indicated time points. The ordinate represents expression values relative to the PBS 2-h time point. Means are calculated from three independent biological experiments. Error bars represent the means ± S.E. Statistical significance was determined using the Student's t test. *, p < 0.05; **, p < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2719400&req=5

Figure 1: Transcript levels of CTL4 and CTLMA2 in whole mosquitoes. Analysis of transcript levels was performed by qRT-PCR in mosquitoes injected with E. coli (gray), S. aureus (black), or sterile PBS (control, white) at the indicated time points. The ordinate represents expression values relative to the PBS 2-h time point. Means are calculated from three independent biological experiments. Error bars represent the means ± S.E. Statistical significance was determined using the Student's t test. *, p < 0.05; **, p < 0.01.

Mentions: The involvement of several C-type lectins in vertebrate and putatively in invertebrate innate immune responses prompted us to test whether CTL4 and CTLMA2 are involved in the mosquito immune defense against bacterial infections. We first measured by qRT-PCR whether CTL4 and CTLMA2 expression is induced by bacterial challenge. A. gambiae female mosquitoes of the G3 strain were injected with a bacterial suspension of E. coli or S. aureus in PBS or with PBS alone, and the transcript levels of both genes were assessed in whole mosquitoes at several time points post-challenge (Fig. 1). CTL4 and CTLMA2 transcripts were significantly up-regulated in mosquitoes injected with bacterial suspensions as compared with the PBS-injected controls, at 6–24 h post-injection. The induced expression of both genes was maximal at 12 h after infection.


Two C-type lectins cooperate to defend Anopheles gambiae against Gram-negative bacteria.

Schnitger AK, Yassine H, Kafatos FC, Osta MA - J. Biol. Chem. (2009)

Transcript levels of CTL4 and CTLMA2 in whole mosquitoes. Analysis of transcript levels was performed by qRT-PCR in mosquitoes injected with E. coli (gray), S. aureus (black), or sterile PBS (control, white) at the indicated time points. The ordinate represents expression values relative to the PBS 2-h time point. Means are calculated from three independent biological experiments. Error bars represent the means ± S.E. Statistical significance was determined using the Student's t test. *, p < 0.05; **, p < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2719400&req=5

Figure 1: Transcript levels of CTL4 and CTLMA2 in whole mosquitoes. Analysis of transcript levels was performed by qRT-PCR in mosquitoes injected with E. coli (gray), S. aureus (black), or sterile PBS (control, white) at the indicated time points. The ordinate represents expression values relative to the PBS 2-h time point. Means are calculated from three independent biological experiments. Error bars represent the means ± S.E. Statistical significance was determined using the Student's t test. *, p < 0.05; **, p < 0.01.
Mentions: The involvement of several C-type lectins in vertebrate and putatively in invertebrate innate immune responses prompted us to test whether CTL4 and CTLMA2 are involved in the mosquito immune defense against bacterial infections. We first measured by qRT-PCR whether CTL4 and CTLMA2 expression is induced by bacterial challenge. A. gambiae female mosquitoes of the G3 strain were injected with a bacterial suspension of E. coli or S. aureus in PBS or with PBS alone, and the transcript levels of both genes were assessed in whole mosquitoes at several time points post-challenge (Fig. 1). CTL4 and CTLMA2 transcripts were significantly up-regulated in mosquitoes injected with bacterial suspensions as compared with the PBS-injected controls, at 6–24 h post-injection. The induced expression of both genes was maximal at 12 h after infection.

Bottom Line: Although studies in insects and other invertebrates have described CTL activation of effector immune responses in vitro, the contribution of these CTLs to immune defenses in vivo is still poorly understood.Silencing either CTL dramatically reduces mosquito survival to Gram-negative but not to Gram-positive bacterial infections, suggesting a role in defense against Gram-negative bacteria.Apparently, CTL4 and CTLMA2 serve pleiotropic functions in the innate immune response of A. gambiae.

View Article: PubMed Central - PubMed

Affiliation: Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.

ABSTRACT
C-type lectins (CTLs) are a family of proteins that share a common structural motif, the carbohydrate recognition domain, and may act as receptors in pathogen recognition. Indeed, some vertebrate CTLs, particularly the collectins, are unequivocally implicated in the innate immune response to certain microbes. Although studies in insects and other invertebrates have described CTL activation of effector immune responses in vitro, the contribution of these CTLs to immune defenses in vivo is still poorly understood. Here we report that two CTLs, CTL4 and CTLMA2, which were shown previously to inhibit Plasmodium berghei ookinete melanization in the malaria vector Anopheles gambiae, are transcriptionally induced by bacterial challenge. Using in vivo reverse genetic analysis, we show that both CTLs are required for the clearance of Escherichia coli, but not Staphylococcus aureus, from adult female mosquitoes. Silencing either CTL dramatically reduces mosquito survival to Gram-negative but not to Gram-positive bacterial infections, suggesting a role in defense against Gram-negative bacteria. Furthermore, molecular characterization reveals that both CTLs are secreted into the mosquito hemolymph mainly in the form of a disulfide-linked heterodimer. This association explains the similar roles of these CTLs in bacterial defense as well as in the melanization response to P. berghei ookinetes. Apparently, CTL4 and CTLMA2 serve pleiotropic functions in the innate immune response of A. gambiae.

Show MeSH
Related in: MedlinePlus