Biomedical subjects

Raul Bettencourt

Publications and source records attributed to Raul Bettencourt.

4 recordsLinked to original sources

PubMed2006

RNA interference of Hemolin causes depletion of phenoloxidase activity in Hyalophora cecropia.

Melanization is regulated by the prophenoloxidase cascade and functions as a response to intruding microorganisms in invertebrates. When injecting dsRNA of the lepidopteran immune protein hemolin in pupae of Hyalophora cecropia (Lepidoptera: Saturniidae), we observed a significant reduction in phenoloxidase activity after 24 h, but not after 72 h. The link between hemolin and the prophenoloxidase system suggests that hemolin is a pattern recognition protein important for the triggering of the prophenoloxidase cascade in the defence against bacterial infections.

Animals↗

PubMed2004

Hemolymph-dependent and -independent responses in Drosophila immune tissue.

Insects possess an antimicrobial defense response that is similar to the mammalian innate immune response. The innate immune system is designed to recognize conserved components of microorganisms called pathogen-associated molecular patterns (PAMPs). How host receptors detect PAMPs and transmit the signals to mount the immune response is being elucidated. Using GFP-Dorsal, -Dif, and -Relish reporter proteins in ex vivo assays, we demonstrate that Drosophila fat bodies, a major immune tissue, have both hemolymph-dependent and -independent responses. Microbial preparations such as lipoteichoic acid (LTA) and peptidoglycan (PGN) can stimulate some responses from dissected and rinsed larval fat bodies. Therefore, at least some aspects of recognition can occur on fat body cell surfaces, bypassing the requirement of hemolymph. Our results also show that supernatants from bacterial cultures can stimulate the nuclear translocation of Dorsal in dissected fat bodies, but this stimulation is strictly hemolymph-dependent. Various biochemical assays suggest that the factors from bacterial supernatants that stimulate the hemolymph-dependent nuclear translocation are likely made up of proteins. We further show that Dorsal mutant larvae have much lower phenoloxidase activity, consistent with a more important role of Dorsal in innate immunity than previously shown.

Animals↗

PubMed2004

Learning the codes of fly immunity.

Insect antimicrobial response serves as an excellent model for studying human innate immunity. In this issue of Molecular Cell, Senger and colleagues demonstrate that a large number of immunity genes in Drosophila fat bodies can be regulated by a simple code, REL-GATA.

Animals↗

PubMed2004

Toll and Toll-9 in Drosophila innate immune response.

In both insects and mammals, members of the Toll receptor family play important roles in the initial events leading to the activation of immunity genes. The prototypic Toll in Drosophila appears to be activated by a host protein ligand after microbial stimulation. The cellular events and the biological response after Toll activation, however, require further investigation. We used transgenic Drosophila strains expressing NF-kappaB and Toll proteins to investigate innate immune response in whole larvae and dissected larval fat bodies. Substantial activation of antimicrobial peptide genes was observed after septic injury. To circumvent the contribution of injury-induced response, we used dissected larval fat bodies to show that commercially available microbial compounds were able to alter the cellular distribution of Toll. The results also demonstrate that complex cellular events, including receptor trafficking, likely take place after stimulation of the larval immune tissue. By genome-wide expression analysis, we further show that Toll and Toll-9 may utilize the same signaling pathway in activating many immunity genes. Thus, the innate immune response in Drosophila is regulated by complex mechanisms, which involve Toll and other Toll-related proteins.

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