Molecular characterization of putative neuropeptide, amine, diffusible gas and small molecule transmitter biosynthetic enzymes in the eyestalk ganglia of the American lobster, Homarus Americanus

Authors: CHRISTIE, ANDREW - University Of Hawaii; GANDLER, HELEN - Bowdoin College; LAMEYER, TESS - Bowdoin College; PASCUAL, MICAH - University Of Hawaii; SHEA, DEVLIN - Bowdoin College; STANHOPE, MEREDITH - Bowdoin College; YU, ANDY - University Of Hawaii; DICKINSON, PATSY - Bowdoin College; Hull, Joe

Submitted to: Invertebrate Neuroscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2018
Publication Date: 10/1/2018
Citation: Christie, A.E., Gandler, H.I., Lameyer, T.J., Pascual, M.G., Shea, D.N., Stanhope, M.E., Yu, A., Dickinson, P.S., Hull, J.J. 2018. Molecular characterization of putative neuropeptide, amine, diffusible gas and small molecule transmitter biosynthetic enzymes in the eyestalk ganglia of the American lobster, Homarus Americanus. Invertebrate Neuroscience. 18:12.

Interpretive Summary: The American lobster, one of the world’s most well-known crustaceans, is a model system for understanding the generation, maintenance and neuromodulation of rhythmically active motor behaviors across the animal kingdom. Although much work has focused on identifying the various neuromodulators (peptides, amines, diffusible gases and small molecule transmitters), the molecular basis underlying the biosynthesis of these compounds in crustaceans has not been as thoroughly studied. To gain a better understanding of these processes, a lobster-specific database was searched for sequences with similarity to known neuromodulator biosynthesis genes. In total, 23 sequences were identified and specific expression of these products was confirmed using conventional PCR methods. Taken collectively, the data presented in this report provide a strong foundation from which to initiate gene-based studies of neuromodulatory control in the American lobster and provide insights into these processes in other crustaceans and arthropods.

Technical Abstract: The American lobster, Homarus americanus, is a model for investigating the neuromodulatory control of physiology and behavior. Prior studies have shown that multiple classes of chemicals serve as locally released/circulating neuromodulators/ neurotransmitters in this species. Interestingly, while many neuroactive compounds are known from Homarus, little work has focused on identifying/characterizing the enzymes responsible for their biosynthesis, despite the fact that these enzymes are key components for regulating neuromodulation/neurotransmission. Here, an eyestalk ganglia-specific transcriptome was mined for transcripts encoding enzymes involved in neuropeptide, amine, diffusible gas and small molecule transmitter biosynthesis. Using known Drosophila melanogaster proteins as templates, transcripts encoding putative Homarus homologs of peptide precursor processing (signal peptide peptidase, prohormone processing protease and carboxypeptidase) and immature peptide modifying (glutaminyl cyclase, tyrosylprotein sulfotransferase, protein disulfide isomerase, peptidylglycine-alpha-hydroxylating monooxygenase and peptidyl-alpha-hydroxyglycine-alpha-amidating lyase) enzymes were identified in the eyestalk assembly. Similarly, transcripts encoding full complements of the enzymes responsible for dopamine [tryptophan-phenylalanine hydroxylase (TPH), tyrosine hydroxylase and DOPA decarboxylase (DDC)], octopamine (TPH, tyrosine decarboxylase and tyramine beta-hydroxylase), serotonin (TPH or tryptophan hydroxylase and DDC) and histamine (histidine decarboxylase) biosynthesis were identified from the eyestalk ganglia, as were those responsible for the generation of the gases nitric oxide (nitric oxide synthase) and carbon monoxide (heme oxygenase), and the small molecule transmitters acetylcholine (choline acetyltransferase), glutamate (glutaminase) and GABA (glutamic acid decarboxylase). The presence and identity of the transcriptome-derived transcripts were confirmed using RT-PCR. The data presented here provide a foundation for future gene-based studies of neuromodulatory control at the level of neurotransmitter/modulator biosynthesis in Homarus.