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Updated: Sep 28, 2026
Spatial and Temporal Control of Murine Melanoma Initiation from Mutant Melanocyte Stem Cells
Published on: June 7, 2019
A serpin mutant links Toll activation to melanization in the host defence of Drosophila
Petros Ligoxygakis1, Nadège Pelte, Chuanyi Ji
1Institut de Biologie Moléculaire and Cellulaire, UPR 9022 du CNRS, 15, rue René Descartes, F-67084 Strasbourg Cedex, France.
Abstract:
A prominent response during the Drosophila host defence is the induction of proteolytic cascades, some of which lead to localized melanization of pathogen surfaces, while others activate one of the major players in the systemic antimicrobial response, the Toll pathway. Despite the fact that gain-of-function mutations in the Toll receptor gene result in melanization, a clear link between Toll activation and the melanization reaction has not been firmly established. Here, we present evidence for the coordination of hemolymph-borne melanization with activation of the Toll pathway in the Drosophila host defence. The melanization reaction requires Toll pathway activation and depends on the removal of the Drosophila serine protease inhibitor Serpin27A. Flies deficient for this serpin exhibit spontaneous melanization in larvae and adults. Microbial challenge induces its removal from the hemolymph through Toll-dependent transcription of an acute phase immune reaction component.
Insights
Drosophila host defense involves melanization and the Toll pathway. This study shows Toll activation is required for melanization, dependent on removing Serpin27A, linking these crucial immune responses.
Area of Science:
- Insects
- Immunology
- Biochemistry
Background:
- Drosophila host defense involves proteolytic cascades, including melanization and the Toll pathway.
- A direct link between Toll pathway activation and melanization has not been clearly established.
Purpose of the Study:
- To investigate the coordination between hemolymph-borne melanization and Toll pathway activation in Drosophila.
- To elucidate the role of Serpin27A in regulating melanization during host defense.
Main Methods:
- Analysis of Toll pathway activation and melanization in wild-type and mutant Drosophila.
- Investigated the function of Serpin27A in melanization.
- Studied the transcriptional regulation of Serpin27A during microbial challenge.
Main Results:
- Melanization requires Toll pathway activation and the removal of Serpin27A.
- Flies deficient in Serpin27A exhibit spontaneous melanization.
- Microbial challenge leads to Serpin27A removal via Toll-dependent transcription.
Conclusions:
- Toll pathway activation is essential for initiating melanization in Drosophila.
- Serpin27A acts as a key regulator, inhibiting melanization, and its removal is critical for the immune response.
- This study establishes a clear mechanistic link between Toll signaling and melanization in Drosophila immunity.
