Characterization of the Receptors Associated with the Differing Responses to the Neuropeptide, AST‐C, by the Cardiac Ganglion of the American Lobster, Homarus americanus

Abstract

Central pattern generators (CPGs) are neural networks that produce consistent, rhythmic patterned outputs to reliably activate specific muscles, resulting in repeated and rhythmic movements. The cardiac ganglion (CG) is a CPG in the American lobster, and is responsible for producing a consistent rhythmic heartbeat. Flexibility of rhythmic motor outputs arises from modulation of CPGs, largely by neuropeptides. The lobster heart is modulated by C‐type allatostatins (AST‐C), two of which [pQIRYHQCYFNPISCF, now AST‐C I, and SYWKQCAFNAVSCFamide, now AST‐C II] were previously known; both have been shown to modulate the lobster heart. Using transcriptomes generated from nervous system tissues, we identified a third isoform of AST‐C, GNGDGRLYWRCYFNAVSCF, or AST‐C III, in the lobster. All three AST‐C isoforms consistently lead to decreases in contraction frequency when perfused through an isolated lobster heart; in contrast, all can elicit variable responses in contraction amplitude, with amplitude increasing in some lobsters and decreasing in others. The responses to AST‐C I and AST‐C III are more similar to one another than to AST‐C II in any given lobster.We are currently testing the hypothesis that differences in AST‐C receptor expression among individuals underlie these varying responses. Mining of a Homarus americanus transcriptome has led to the identification of three full‐length and one partial putative AST‐C receptors. We are currently conducting experiments to determine whether and to what extent the four putative AST‐C receptors bind the three AST‐C isoforms. Understanding these receptor‐peptide relationships will allow us to elucidate the role the receptors play in the observed differential response to AST‐C.Support or Funding InformationNSF (IOS‐1353023, IOS‐1354567), NIH (8P20GM103423‐12), Cades Foundation, Doherty Foundation gift to Bowdoin College