To what extent may peptide receptor gene diversity/complement contribute to functional flexibility in a simple pattern-generating neural network?

Authors: DICKINSON, PATSY - Bowdoin College; Hull, Joe; MILLER, ALEXANDRA - Bowdoin College; OLEISKY, EMILY - Bowdoin College; CHRISTIE, ANDREW - University Of Hawaii

Submitted to: Comparative Biochemistry and Physiology, Part D: Genomics and Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2019
Publication Date: 3/7/2019
Publication URL: http://handle.nal.usda.gov/10113/6347695
Citation: Dickinson, P.S., Hull, J.J., Miller, A., Oleisky, E.R., Christie, A.E. 2019. To what extent may peptide receptor gene diversity/complement contribute to functional flexibility in a simple pattern-generating neural network? Comparative Biochemistry and Physiology, Part D: Genomics and Proteomics. 30:262-282.

Interpretive Summary: Peptides regulate numerous biological processes throughout the animal kingdom via interactions with cell membrane receptors that facilitate the process of turning an extracellular peptide signal into a cellular response. In the Jonah crab, multiple peptide families have been previously identified, however, the corresponding receptor repertoire is not as well defined. To address this deficiency, a mixed tissue transcriptomic sequence dataset was screened for peptide receptor-like sequences. The search identified 46 receptors for 27 peptide families. From this group of receptors, PCR-based profiling showed that 36 were expressed within the crab’s stomatogastric ganglion, a specific tissue associated with rhythmic chewing movements. The identification of these stomatogastric ganglion receptors provides insights into potential peptide regulation of the tissue and by proxy the behaviors it controls. Consequently, receptors expressed in the tissue would be expected to mediate a peptide signal, whereas receptors not expressed would have no biological effect. This hypothesis was confirmed by comparing the activity of two receptor-peptide sets not previously studied in terms of stomatogastric ganglion activity. Overall, the study provides a rational foundation for assessing the functional role of various peptides on the stomatogastric ganglion.

Technical Abstract: Peptides are known to contribute to central pattern generator (CPG) flexibility throughout the animal kingdom. However, the role played by receptor diversity/complement in determining this functional flexibility is not clear. The stomatogastric ganglion (STG) of the crab, Cancer borealis, contains CPGs that are models for investigating peptidergic control of rhythmic behavior. Although many Cancer peptides have been identified, their peptide receptors are largely unknown. Thus, the extent to which receptor diversity/complement contributes to mod- ulatory flexibility in this system remains unresolved. Here, a Cancer mixed nervous system transcriptome was used to determine the peptide receptor complement for the crab nervous system as a whole. Receptors for 27 peptide families, including multiple receptors for some groups, were identified. To increase confidence in the predicted sequences, receptors for allatostatin-A, allatostatin-B, and allatostatin-C were cloned, sequenced, and expressed in an insect cell line; as expected, all three receptors trafficked to the cell membrane. RT-PCR was used to determine whether each receptor was expressed in the Cancer STG. Transcripts for 36 of the 46 identified receptors were amplified; these included at least one for each peptide family except RYamide. Finally, two peptides untested on the crab STG were assessed for their influence on its motor outputs. Myosuppressin, for which STG receptors were identified, exhibited clear modulatory effects on the motor patterns of the ganglion, while a native RYamide, for which no STG receptors were found, elicited no consistent modulatory effects. These data support receptor diversity/complement as a major contributor to the functional flexibility of CPGs.