Multiple modulators act on the cardiac ganglion of the crab, Cancer borealis

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%

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

“…Previous studies of modulation of the crustacean cardiac neuromuscular system have identified a number of potential sites at which transmitters and hormones can alter output of the system as a whole, and have shown that single modulators often affect multiple sites. Modulators act on the pattern generator of the CG itself (Cruz-Bermudez et al, 2006;Cruz-Bermudez and Marder, 2007;Fort et al, 2004;Fort et al, 2007a;Fort et al, 2007b;Freschi, 1989;Krajniak, 1991;Krajniak et al, 1990;Mercier et al, 2003;Miller and Sullivan, 1981;Saver et al, 1999;Stevens et al, 2008;Stevens et al, 2009). Several of these same modulators, including proctolin (Wilkens et al, 2005), and a number of different FMRFamide-like peptides (Fort et al, 2007a;Stevens et al, 2009;Wilkens et al, 2005), also exert effects at the neuromuscular junction or directly on crustacean cardiac muscle.…”

Section: Discussionmentioning

confidence: 99%

“…Inhibitory effects of all three AST types (A-, B-and C-types) have been documented in the pyloric pattern generator of the stomatogastric system, but details of the mechanisms used to cause the observed decreases in cycle frequency have not yet been examined Dircksen et al, 1999;Fu et al, 2007;Ma et al, 2009;Szabo et al, 2011). Additionally, inhibitory effects of A-type allatostatins have been recorded in the crab CG (Cruz-Bermudez and Marder, 2007). In this case, cycle frequency decreases as it does in the presence of C-AST in the lobster; however, although it does not change the membrane potentials of motor neurons, A-AST causes a decrease in both the frequency and number of spikes per burst, changes that do not take place in response to C-AST.…”

Section: Discussionmentioning

confidence: 99%

Inter-animal variability in the effects of C-type allatostatin on the cardiac neuromuscular system in the lobster Homarus americanus

Wiwatpanit

Powers

Dickinson

2012

SUMMARYAlthough the global effects of many modulators on pattern generators are relatively consistent among preparations, modulators can induce different alterations in different preparations. We examined the mechanisms that underlie such variability in the modulatory effects of the peptide C-type allatostatin (C-AST; pQIRYHQCYFNPISCF) on the cardiac neuromuscular system of the lobster Homarus americanus. Perfusion of C-AST through the semi-intact heart consistently decreased the frequency of ongoing contractions. However, the effect of C-AST on contraction amplitude varied between preparations, decreasing in some preparations and increasing in others. To investigate this variable effect, we examined the effects of C-AST both peripherally and centrally. When contractions of the myocardium were elicited by controlled stimuli, C-AST did not alter heart contraction at the periphery (myocardium or neuromuscular junction) in any hearts. However, when applied either to the semi-intact heart or to the cardiac ganglion (CG) isolated from hearts that responded to C-AST with increased contraction force, C-AST increased both motor neuron burst duration and the number of spikes per burst by about 25%. In contrast, CG output was increased only marginally in hearts that responded to C-AST with a decrease in contraction amplitude, suggesting that the decrease in amplitude in those preparations resulted from decreased peripheral facilitation. Our data suggest that the differential effects of a single peptide on the cardiac neuromuscular system are due solely to differential effects of the peptide on the pattern generator; the extent to which the peptide induces increased burst duration is crucial in determining its overall effect on the system.

“…preparations with high heart rates, it increases frequency in at least some preparations, notably those in which initial heart rate is very low, and it increases amplitude in virtually all preparations. One notable difference between the experiments reported here and those described in Cruz-Bermúdez and Marder (Cruz-Bermúdez and Marder, 2007) is that our experiments used whole hearts, whereas the effects of AST-B on Cancer were tested on the isolated cardiac ganglion. Thus, it is possible that the excitatory effects of SYWKQCAFNAVSCFamide require feedback from heart muscle tissue.…”

Section: A Physiological Role For Sywkqcafnavscfamidementioning

confidence: 90%

“…cockroaches, crickets and termites (Stay and Tobe, 2007). A-type peptides have also been found in a number of crustaceans (Duve et al, 1997;Dircksen et al, 1999;Duve et al, 2002;Huybrechts et al, 2003;Fu et al, 2005;Yasuda-Kamatani and Yasuda, 2006;Yin et al, 2006;Christie et al, 2008a;Ma et al, 2008;Gard et al, 2009;Ma et al, 2009), where they have been shown to function as locally released and/or hormonally delivered neuro/myomodulators (Skiebe and Schneider, 1994;Jorge-Rivera and Marder, 1997;Jorge-Rivera et al, 1998;Dircksen et al, 1999;Kreissl et al, 1999;Birmingham et al, 2003;Billimoria et al, 2006;Cruz-Bermúdez and Marder, 2007). Molecular, biochemical and mass spectral analyses have shown that multiple isoforms of A-type peptides are common in both insect and crustacean species, with multiple peptides encoded by the known arthropod A-AST prepro-hormones (e.g.…”

Section: Introductionmentioning

confidence: 99%

Identification of SYWKQCAFNAVSCFamide: a broadly conserved crustacean C-type allatostatin-like peptide with both neuromodulatory and cardioactive properties

Dickinson

Wiwatpanit

Gabranski

et al. 2009

SUMMARYThe allatostatins comprise three structurally distinct peptide families that regulate juvenile hormone production by the insect corpora allata. A-type family members contain the C-terminal motif -YXFGLamide and have been found in species from numerous arthropod taxa. Members of the B-type family exhibit a -WX 6 Wamide C-terminus and, like the A-type peptides, appear to be broadly conserved within the Arthropoda. By contrast, members of the C-type family, typified by the unblocked C-terminus -PISCF, a pyroglutamine blocked N-terminus, and a disulfide bridge between two internal Cys residues, have only been found in holometabolous insects, i.e. lepidopterans and dipterans. Here, using transcriptomics, we have identified SYWKQCAFNAVSCFamide (disulfide bridging predicted between the two Cys residues), a known honeybee and water flea C-typelike peptide, from the American lobster Homarus americanus (infraorder Astacidea). Using matrix assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS), a mass corresponding to that of SYWKQCAFNAVSCFamide was detected in the H. americanus brain, supporting the existence of this peptide and its theorized structure. Furthermore, SYWKQCAFNAVSCFamide was detected by MALDI-FTMS in neural tissues from five additional astacideans as well as 19 members of four other decapod infraorders (i.e. Achelata, Anomura, Brachyura and Thalassinidea), suggesting that it is a broadly conserved decapod peptide. In H. americanus, SYWKQCAFNAVSCFamide is capable of modulating the output of both the pyloric circuit of the stomatogastric nervous system and the heart. This is the first demonstration of bioactivity for this peptide in any species.