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Activation of Drosophila hemocyte motility by the ecdysone hormone
Christopher J Sampson1, Unum Amin, Juan-Pablo Couso
1JMS Building, University of Sussex, Brighton BN1 9QG, East Sussex, UK.
Abstract:
Drosophila hemocytes compose the cellular arm of the fly's innate immune system. Plasmatocytes, putative homologues to mammalian macrophages, represent ∼95% of the migratory hemocyte population in circulation and are responsible for the phagocytosis of bacteria and apoptotic tissues that arise during metamorphosis. It is not known as to how hemocytes become activated from a sessile state in response to such infectious and developmental cues, although the hormone ecdysone has been suggested as the signal that shifts hemocyte behaviour from quiescent to migratory at metamorphosis. Here, we corroborate this hypothesis by showing the activation of hemocyte motility by ecdysone. We induce motile behaviour in larval hemocytes by culturing them with 20-hydroxyecdysone ex vivo. Moreover, we also determine that motile cell behaviour requires the ecdysone receptor complex and leads to asymmetrical redistribution of both actin and tubulin cytoskeleton.
Insights
The hormone ecdysone activates Drosophila hemocyte motility, specifically plasmatocytes, during metamorphosis. This process requires the ecdysone receptor and cytoskeletal changes for cell movement.
Area of Science:
- Invertebrate immunology
- Developmental biology
- Cellular signaling
Background:
- Drosophila hemocytes are crucial for innate immunity, with plasmatocytes acting like macrophages.
- Plasmatocytes are responsible for clearing pathogens and apoptotic cells during metamorphosis.
- The activation mechanism of sessile hemocytes remains unclear, though ecdysone is a suspected signaling molecule.
Purpose of the Study:
- To investigate the role of the hormone ecdysone in activating Drosophila hemocyte motility.
- To determine the molecular requirements for ecdysone-induced hemocyte activation.
Main Methods:
- Ex vivo culture of larval Drosophila hemocytes with 20-hydroxyecdysone.
- Observation of hemocyte motility and cytoskeletal changes.
- Analysis of ecdysone receptor complex involvement.
Main Results:
- Ecdysone treatment induced motile behavior in larval hemocytes.
- Ecdysone-induced cell motility requires the ecdysone receptor complex.
- Motile hemocytes exhibited asymmetrical redistribution of actin and tubulin.
Conclusions:
- Ecdysone acts as a key signaling molecule that activates hemocyte motility at metamorphosis.
- The ecdysone receptor pathway mediates the transition of hemocytes from a quiescent to a migratory state.
- Cytoskeletal rearrangements are essential for ecdysone-driven hemocyte migration.
