A common muscarinic pathway for diapause recovery in the distantly related nematode species Caenorhabditis elegans and Ancylostoma caninum.

Converging TGF-beta and insulin-like neuroendocrine signaling pathways regulate whether Caenorhabditis elegans develops reproductively or arrests at the dauer larval stage. We examined whether neurotransmitters act in the dauer entry or recovery pathways. Muscarinic agonists promote recovery from dauer arrest induced by pheromone as well as by mutations in the TGF-beta pathway. Dauer recovery in these animals is inhibited by the muscarinic antagonist atropine. Muscarinic agonists do not induce dauer recovery of either daf-2 or age-1 mutant animals, which have defects in the insulin-like signaling pathway. These data suggest that a metabotropic acetylcholine signaling pathway activates an insulin-like signal during C. elegans dauer recovery. Analogous and perhaps homologous cholinergic regulation of mammalian insulin release by the autonomic nervous system has been noted. In the parasitic nematode Ancylostoma caninum, the dauer larval stage is the infective stage, and recovery to the reproductive stage normally is induced by host factors. Muscarinic agonists also induce and atropine potently inhibits in vitro recovery of A. caninum dauer arrest. We suggest that host or parasite insulin-like signals may regulate recovery of A. caninum and could be potential targets for antihelminthic drugs.

Ancylostoma caninum: metalloprotease release coincides with activation of infective larvae in vitro.

Infective stages of several nematode parasites are known to release proteases in excretory/secretory products. These enzymes are believed to facilitate tissue invasion, although direct evidence is lacking. For these investigations, we employed an assay that uses the resumption of feeding as a marker for early events in the infectious process. When Ancylostoma caninum third-stage infective larvae are stimulated to feed in vitro, they release proteases of approximately 50,000 and 90,000 molecular weight, as determined by substrate gel electrophoresis. The enzymes are inhibited by the zinc chelator 1,10-phenanthroline, but not by the nonchelating isomer 4,7-phenanthroline, indicating that the proteolytic activity is zinc-dependent. Both compounds inhibit in vitro feeding, although inhibition by 1,10-phenanthroline is zinc-dependent, whereas inhibition by 4,7-phenanthroline is zinc-independent. The specific release of proteases associated with the initiation of feeding suggests that the metalloprotease serves an integral function in the transition of the free-living stage to parasitism.