Neuroendocrine Coupling of Interoceptive Bacteria-Derived Cues to Foraging Behavior in C. elegans .

Animal internal state is modulated by nutrient intake, resulting in behavioral responses to changing food conditions. DAF-7 is a neuroendocrine TGF-beta ligand that regulates diverse food-related behaviors of Caenorhabditis elegans, including foraging behavior. Here, we show that in C. elegans, interoceptive cues from the ingestion of bacterial food inhibit the expression of DAF-7, a neuroendocrine TGF-beta ligand, from the ASJ pair of sensory neurons, whereas food deprivation in the presence of external chemosensory cues from bacteria promotes the expression of DAF-7 from the ASJ neurons. We show that SCD-2, the C. elegans ortholog of mammalian Anaplastic Lymphoma Kinase (ALK), which has been implicated in the central control of metabolism of mammals, functions in the AIA interneurons to regulate foraging behavior and cell-non-autonomously control the expression of DAF-7 from the ASJ neurons. Our data establish an SCD-2-dependent neuroendocrine DAF-7 gene expression feedback loop that couples the ingestion of bacterial food to foraging behavior.