Biosynthesis of Modular Ascarosides in C. elegans

Abstract

The nematode Caenorhabditis elegans uses simple building blocks from primary metabolism and a strategy of modular assembly to build a great diversity of signaling molecules, the ascarosides, which function as a chemical language in this model organism. In the ascarosides, the dideoxysugar ascarylose serves as a scaffold to which diverse moieties from lipid, amino acid, neurotransmitter, and nucleoside metabolism are attached. However, the mechanisms that underlie the highly specific assembly of ascarosides are not understood. We show that the acyl-CoA synthetase ACS-7, which localizes to lysosome-related organelles, is specifically required for the attachment of different building blocks to the 4′-position of ascr#9. We further show that mutants lacking lysosome-related organelles are defective in the production of all 4′-modified ascarosides, thus identifying the waste disposal system of the cell as a hotspot for ascaroside biosynthesis.

Biosynthetic tailoring of existing ascaroside pheromones alters their biological function in C. elegans

“…This result suggests that attachment of the IC group occurs after side-chain β-oxidation, at least in the biosynthetic pathway to IC-asc-C9. The acyl-CoA synthetase gene, acs-7 , has been shown to be required for biosynthesis of the short-chain IC- and OS-modified ascarosides, IC-asc-C5 and OS-asc-C5 (osas#9), but not for medium-chain IC- and OS-ascarosides, such as IC-asc-C9 and OS-asc-C9 (osas#10) ( Panda et al, 2017 ). Panda et al proposed that ACS-7 activates indole-3-carboxylic acid (ICA) as the corresponding CoA-thioester (IC-CoA) and is involved in the attachment of the IC group specifically to the short-chain ascaroside asc-C5 (ascr#9) to make IC-asc-C5 ( Figure 1A ).…”

“…Their interpretation of these data was that some other protein or factor was required for the full activity of ACS-7. Panda et al showed that mutant worms lacking lysosome-related organelles (LROs) did not make 4’-modified ascarosides, and they reported that ACS-7 was expressed in the lysosome ( Panda et al, 2017 ). Thus, they concluded that ACS-7 was functioning inside the lysosomes in IC-ascaroside biosynthesis.…”

“…In our model, under favorable conditions, the IC head group is attached by unknown enzymes to the medium-chain ascarosides, such as asc-C9, to make aggregation pheromones. This process may occur in the lysosome as it has been shown that the lysosome is required for the biosynthesis of 4’-modified ascarosides ( Panda et al, 2017 ). If conditions decline, such as during starvation, ACS-7 then plays a key role for activating IC-asc-C9 as the corresponding CoA-thioester for further β-oxidation of its side chain in the peroxisome to make shorter-chain IC-ascarosides, such as the dauer pheromone IC-asc-C5.…”

Improved Synthesis for Modular Ascarosides Uncovers Biological Activity

“…1,2 These compounds are derived from glycosides of the dideoxy sugars l -ascarylose and l -paratose, which are decorated with diverse building blocks from amino acid, nucleoside, carbohydrate, and fatty acid metabolism (Figure 1). 1,3 NDMMs function as signaling molecules that regulate many aspects of nematode life history, including development, 4–7 lifespan, 8,9 morphology, 10 social communication, 6,7,11–15 as well as interactions with other species. 16–18 Since even small changes in the chemical structures of NDMMs can greatly affect biological activity and NDMMs can be active at extremely low (femtomolar) concentrations, 12,19 requirements for the purity of synthetic samples for bioassays are particularly stringent.…”

Plant metabolism of nematode pheromones mediates plant-nematode interactions

“…Mass spectrometric analysis. High-resolution LC-MS analysis was performed on a Dionex 3000 UPLC system coupled with a Thermo Q Exactive high-resolution mass spectrometer as described previously 10,46 . Metabolite extracts were separated using a water-acetonitrile gradient using Agilent ZORBOX Eclispse XDB-C18 rapid resolution column (2.1 × 150 mm, particle size 1.8-micron) maintained at 40°C…”