Identification and cardiotropic actions of sulfakinin peptides in the American lobster Homarus americanus

SUMMARYIn insects, a family of peptides with sequence homology to the vertebrate calcitonins has been implicated in the control of diuresis, a process that includes mixing of the hemolymph. Here, we show that a member of the insect calcitonin-like diuretic hormone (CLDH) family is present in the American lobster, Homarus americanus, serving, at least in part, as a powerful modulator of cardiac output. Specifically, during an ongoing EST project, a transcript encoding a putative H. americanus CLDH precursor was identified; a full-length cDNA was subsequently cloned. In silico analyses of the deduced prepro-hormone predicted the mature structure of the encoded CLDH to be GLDLGLGRGFSGSQAAKHLMGLAAANFAGGPamide (Homam-CLDH), which is identical to a known Tribolium castaneum peptide. RT-PCR tissue profiling suggests that Homam-CLDH is broadly distributed within the lobster nervous system, including the cardiac ganglion (CG), which controls the movement of the neurogenic heart. RT-PCR analysis conducted on pacemaker neuron-and motor neuron-specific cDNAs suggests that the motor neurons are the source of the CLDH message in the CG. Perfusion of Homam-CLDH through the isolated lobster heart produced dose-dependent increases in both contraction frequency and amplitude and a dose-dependent decrease in contraction duration, with threshold concentrations for all parameters in the range 10 -11 to 10 -10 moll -1 or less, among the lowest for any peptide on this system. This report is the first documentation of a decapod CLDH, the first demonstration of CLDH bioactivity outside the Insecta, and the first detection of an intrinsic neuropeptide transcript in the crustacean CG.

Section: Homam-cldh Is a Potent Modulator Of Cardiac Outputmentioning

confidence: 69%

Section: The Distribution Of Calcitonin-like Diuretic Hormone Mrna Sumentioning

confidence: 92%

Section: Cldh Is a Powerful Cardioactive Peptide In H Americanusmentioning

confidence: 99%

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Identification of a calcitonin-like diuretic hormone that functions as an intrinsic modulator of the American lobster,Homarus americanus, cardiac neuromuscular system

Christie

Stevens

Bowers

et al. 2010

“…To date, over two dozen FMRFamide-like peptides have been identified in the nervous system of H. americanus (Trimmer et al, 1987;Stemmler et al, 2007;Dickinson et al, 2007;Ma et al, 2008); amongst these is pQDLDHVFLRFamide (Stemmler et al, 2007;Ma et al, 2008), a member of the Crust-MS subfamily. Immunohistochemistry using antibodies directed against the sequence FMRFamide has long suggested that at least a subset of these peptides is present within the lobster STNS (Fénelon et al, 1998), including within the cell bodies of the PS neurons (Fénelon et al, 1998).…”

Section: Rt-pcr Analysis Suggests That Crust-ms Is Present In the Lobmentioning

confidence: 99%

Coordination of distinct but interacting rhythmic motor programs by a modulatory projection neuron using different co-transmitters in different ganglia

Kwiatkowski

Gabranski

Huber

et al. 2013

Self Cite

SUMMARYWhile many neurons are known to contain multiple neurotransmitters, the specific roles played by each co-transmitter within a neuron are often poorly understood. Here, we investigated the roles of the co-transmitters of the pyloric suppressor (PS) neurons, which are located in the stomatogastric nervous system (STNS) of the lobster Homarus americanus. The PS neurons are known to contain histamine; using RT-PCR, we identified a second co-transmitter as the FMRFamide-like peptide crustacean myosuppressin (Crust-MS). The modulatory effects of Crust-MS application on the gastric mill and pyloric patterns, generated in the stomatogastric ganglion (STG), closely resembled those recorded following extracellular PS neuron stimulation. To determine whether histamine plays a role in mediating the effects of the PS neurons in the STG, we bath-applied histamine receptor antagonists to the ganglion. In the presence of the antagonists, the histamine response was blocked, but Crust-MS application and PS stimulation continued to modulate the gastric and pyloric patterns, suggesting that PS effects in the STG are mediated largely by Crust-MS. PS neuron stimulation also excited the oesophageal rhythm, produced in the commissural ganglia (CoGs) of the STNS. Application of histamine, but not Crust-MS, to the CoGs mimicked this effect. Histamine receptor antagonists blocked the ability of both histamine and PS stimulation to excite the oesophageal rhythm, providing strong evidence that the PS neurons use histamine in the CoGs to exert their effects. Overall, our data suggest that the PS neurons differentially utilize their cotransmitters in spatially distinct locations to coordinate the activity of three independent networks.

“…Delivery of myosuppressin to the lobster heart appears to be hormonal H. americanus possesses an extensive collection of FMRFamidelike peptides Dickinson et al, 2007a;Stemmler et al, 2007;Ma et al, 2008), including the myosuppressin isoform studied here Ma et al, 2008). Previous immunohistochemical and/or biochemical/mass spectral mapping of the distribution of this peptide family have shown that these peptides are broadly distributed within the nervous system of the lobster (e.g.…”

Section: Confirmation Of the Structure Of Homarus Americanus Myosupprmentioning

confidence: 99%

The peptide hormone pQDLDHVFLRFamide (crustacean myosuppressin) modulates theHomarus americanuscardiac neuromuscular system at multiple sites

Stevens

Cashman

Smith

et al. 2009

SUMMARY pQDLDHVFLRFamide is a highly conserved crustacean neuropeptide with a structure that places it within the myosuppressin subfamily of the FMRFamide-like peptides. Despite its apparent ubiquitous conservation in decapod crustaceans, the paracrine and/or endocrine roles played by pQDLDHVFLRFamide remain largely unknown. We have examined the actions of this peptide on the cardiac neuromuscular system of the American lobster Homarus americanus using four preparations: the intact animal, the heart in vitro, the isolated cardiac ganglion (CG), and a stimulated heart muscle preparation. In the intact animal, injection of myosuppressin caused a decrease in heartbeat frequency. Perfusion of the in vitro heart with pQDLDHVFLRFamide elicited a decrease in the frequency and an increase in the amplitude of heart contractions. In the isolated CG, myosuppressin induced a hyperpolarization of the resting membrane potential of cardiac motor neurons and a decrease in the cycle frequency of their bursting. In the stimulated heart muscle preparation, pQDLDHVFLRFamide increased the amplitude of the induced contractions, suggesting that myosuppressin modulates not only the CG, but also peripheral sites. For at least the in vitro heart and the isolated CG, the effects of myosuppressin were dose-dependent (10 -9 to 10 ) consistent with the peptide serving as a circulating hormone. Although cycle frequency, a parameter directly determined by the CG, consistently decreased when pQDLDHVFLRFamide was applied to all preparation types, the magnitudes of this decrease differed, suggesting the possibility that, because myosuppressin modulates the CG and the periphery, it also alters peripheral feedback to the CG.