No abstract

The frequencies of certain periodic behaviors of the nematode C. elegans are regulated in a dose-dependent manner by the activity of the gene egl-10. These behaviors are modulated oppositely by the activity of the G protein alpha subunit gene goa-1, suggesting that egl-10 may regulate a G protein signaling pathway in a dose-dependent fashion. egl-10 encodes a protein similar to Sst2p, a negative regulator of G protein signaling in yeast. EGL-10 protein is localized in neural processes, where it may function in neurotransmitter signaling. Two previously known and 13 newly identified mammalian genes have similarity to egl-10 and SST2, and we propose that members of this family regulate many G protein signaling pathways.

D1-like and D2-like dopamine receptors have synergistic and antagonistic effects on behavior. To understand the mechanisms underlying these effects, we studied dopamine signaling genetically in Caenorhabditis elegans. Knocking out a D2-like receptor, DOP-3, caused locomotion defects similar to those observed in animals lacking dopamine. Knocking out a D1-like receptor, DOP-1, reversed the defects of the DOP-3 knockout. DOP-3 and DOP-1 have their antagonistic effects on locomotion by acting in the same motor neurons, which coexpress the receptors and which are not postsynaptic to dopaminergic neurons. In a screen for mutants unable to respond to dopamine, we identified four genes that encode components of the antagonistic Galpha(o) and Galpha(q) signaling pathways, including Galpha(o) itself and two subunits of the regulator of G protein signaling (RGS) complex that inhibits Galpha(q). Our results indicate that extrasynaptic dopamine regulates C. elegans locomotion through D1- and D2-like receptors that activate the antagonistic Galpha(q) and Galpha(o) signaling pathways, respectively.