The Hemolymph Proteome of Fed and Starved Drosophila Larvae

Abstract

The co-operation of specialized organ systems in complex multicellular organisms depends on effective chemical communication. Thus, body fluids (like blood, lymph or intraspinal fluid) contain myriads of signaling mediators apart from metabolites. Moreover, these fluids are also of crucial importance for immune and wound responses. Compositional analyses of human body fluids are therefore of paramount diagnostic importance. Further improving their comprehensiveness should increase our understanding of inter-organ communication. In arthropods, which have trachea for gas exchange and an open circulatory system, the single dominating interstitial fluid is the hemolymph. Accordingly, a detailed analysis of hemolymph composition should provide an especially comprehensive picture of chemical communication and defense in animals. Therefore we used an extensive protein fractionation workflow in combination with a discovery-driven proteomic approach to map out the detectable protein composition of hemolymph isolated from Drosophila larvae. Combined mass spectrometric analysis revealed more than 700 proteins extending far beyond the previously known Drosophila hemolymph proteome. Moreover, by comparing hemolymph isolated from either fed or starved larvae, we provide initial provisional insights concerning compositional changes in response to nutritional state. Storage proteins in particular were observed to be strongly reduced by starvation. Our hemolymph proteome catalog provides a rich basis for data mining, as exemplified by our identification of potential novel cytokines, as well as for future quantitative analyses by targeted proteomics.

Systemic Activin signaling independently regulates sugar homeostasis, cellular metabolism, and pH balance in Drosophila melanogaster

“…Additionally, our finding that exogenously expressed Daw influences circulating sugar concentration, hemolymph pH, and FB-specific p-Smox signal in a tissue size (dose)-dependent manner further suggests that Daw is likely released into the hemolymph from tissues of origin and exerts its effect in an endocrine manner like a hormone. Consistent with this view, recent MS data reveal the presence of Daw in the hemolymph (21). Curiously, unlike most hormones whose expression is limited to one tissue or gland, daw is expressed in a wide array of tissues including muscle, FB, gut, imaginal discs, and surface glia of the CNS (22,23).…”

Trade‐offs between transgenerational transfer of nutritional stress tolerance and immune priming

“…We also measured haemolymph protein concentration as a measure of insect condition (e.g. Handke et al 2013). Thirty final-instar larvae from each of eight offspring treatments were weighed, and their haemolymph was collected individually by piercing the middle proleg with a fine needle and pooling haemolymph on Parafilm.…”

Strategies for exploring TGF-β signaling in Drosophila

“…The Dawdle ligand is notable because it has been modeled as a circulating factor based on genetic tests wherein ectopic Dawdle expression restores viability to otherwise lethal dawdle mutant animals [49,50]. Indeed, Dawdle was detected in a recent survey of larval hemolymph proteins [51]. Other TGF-β ligands were not detected, but this negative result is inconclusive because only a subset of known circulating proteins were identified.…”