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- Title
SER-7, a Caenorhabditis elegans 5-HT<sub>7</sub>-like Receptor, Is Essential for the 5-HT Stimulation of Pharyngeal Pumping and Egg Laying.
- Authors
Hobson, Robert J.; Hapiak, Vera M.; Hong Xiao; Buehrer, Kara L.; Komuniecki, Patricia R.; Komuniecki, Richard W.
- Abstract
Serotonin (5-HT) stimulates both pharyngeal pumping and egg laying in Caenorhabditis elegans. Four distinct 5-HT receptors have been partially characterized, but little is known about their function in vivo. SER-7 exhibits most sequence identity to the mammalian 5-HT7 receptors and couples to a stimulation of adenyl cyclase when expressed in COS-7 cells. However, many 5-HT7-specific agonists have low affinity for SER-7. 5-HT fails to stimulate pharyngeal pumping and the firing of the MC motorneurons in animals containing the putative ser-7(tm1325) and ser-7(tm1728) null alleles. In addition, although pumping on bacteria is upregulated in ser-7(tm1325) animals, pumping is more irregular. A similar failure to maintain ‘fast pumping’ on bacteria also was observed in ser-1(ok345) and tph-1(mg280) animals that contain putative null alleles of a 5-HT2-like receptor and tryptophan hydroxylase, respectively, suggesting that serotonergic signaling, although not essential for the upregulation of pumping on bacteria, ‘fine tunes’ the process. 5-HT also fails to stimulate egg laying in ser-7(tm1325), ser-1(ok345), and ser-7(tm1325) ser-1(ok345) animals, but only the ser-7 ser-1 double mutants exhibit an Eg1 phenotype. All of the SER-7 mutant phenotypes are rescued by the expression of full-length ser-7::gfp translational fusions, ser-7::gfp is expressed in several pharyngeal neurons, including the MC, M2, M3, M4, and M5, and in vulval muscle. Interestingly, 5-HT inhibits egg laying and pharyngeal pumping in ser-7 null mutants and the 5-HT inhibition of egg laying, but not pumping, is abolished in ser-7(tm1325);ser-4(ok512) double mutants. Taken together, these results suggest that SER-7 is essential for the 5-HT stimulation of both egg laying and pharyngeal pumping, but that other signaling pathways can probably fulfill similar roles in vivo.
- Publication
Genetics, 2006, Vol 172, Issue 1, p159
- ISSN
0016-6731
- Publication type
Academic Journal
- DOI
10.1534/genetics.105.044495