-
Zootaxa Dec 2022During the past century eight species of sea hares of the genus Aplysia were recorded from Peru. However, there is disagreement about how many of these species are valid...
During the past century eight species of sea hares of the genus Aplysia were recorded from Peru. However, there is disagreement about how many of these species are valid and their taxonomy needs to be critically evaluated. Based on detailed morphological examinations, this study presents a redescription of Aplysia nigra d'Orbigny, 1837 and Aplysia inca d'Orbigny, 1837, the most common species of Aplysia along the Peruvian coast. They showed consistent morphological differences, mainly in the foot, parapodia development, opaline gland, jaws, radular teeth and penial morphology. Anatomical data for both species are provided for the first time, as well as a comparison with other species of Aplysia reported for the Eastern Pacific. The records of Aplysia keraudreni Rang, 1828, Aplysia dactylomela Rang, 1828 and Aplysia juliana Quoy & Gaimard, 1832 for Peruvian waters are likely erroneous and need to be verified based on collected specimens.
Topics: Animals; Aplysia; Peru; Species Specificity
PubMed: 37044529
DOI: 10.11646/zootaxa.5222.3.1 -
Frontiers in Pharmacology 2023The vasopressin/oxytocin signaling system is present in both protostomes and deuterostomes and plays various physiological roles. Although there were reports for both...
The vasopressin/oxytocin signaling system is present in both protostomes and deuterostomes and plays various physiological roles. Although there were reports for both vasopressin-like peptides and receptors in mollusc and Octopus, no precursor or receptors have been described in mollusc . Here, through bioinformatics, molecular and cellular biology, we identified both the precursor and two receptors for vasopressin-like peptide, which we named vasotocin (apVT). The precursor provides evidence for the exact sequence of apVT, which is identical to conopressin G from cone snail venom, and contains 9 amino acids, with two cysteines at position 1 and 6, similar to nearly all vasopressin-like peptides. Through inositol monophosphate (IP1) accumulation assay, we demonstrated that two of the three putative receptors we cloned from cDNA are true receptors for apVT. We named the two receptors as apVTR1 and apVTR2. We then determined the roles of post-translational modifications (PTMs) of apVT, i.e., the disulfide bond between two cysteines and the C-terminal amidation on receptor activity. Both the disulfide bond and amidation were critical for the activation of the two receptors. Cross-activity with conopressin S, annetocin from an annelid, and vertebrate oxytocin showed that although all three ligands can activate both receptors, the potency of these peptides differed depending on their residue variations from apVT. We, therefore, tested the roles of each residue through alanine substitution and found that each substitution could reduce the potency of the peptide analog, and substitution of the residues within the disulfide bond tended to have a larger impact on receptor activity than the substitution of those outside the bond. Moreover, the two receptors had different sensitivities to the PTMs and single residue substitutions. Thus, we have characterized the vasotocin signaling system and showed how the PTMs and individual residues in the ligand contributed to receptor activity.
PubMed: 37021048
DOI: 10.3389/fphar.2023.1132066 -
Journal of Neurophysiology May 2023Many behaviors and types of information storage are mediated by lengthy changes in neuronal activity. In bag cell neurons of the hermaphroditic sea snail , a transient...
Many behaviors and types of information storage are mediated by lengthy changes in neuronal activity. In bag cell neurons of the hermaphroditic sea snail , a transient cholinergic synaptic input triggers an ∼30-min afterdischarge. This causes these neuroendocrine cells to release egg laying hormone and elicit reproductive behavior. When acetylcholine is pressure-ejected onto a current-clamped bag cell neuron, the evoked depolarization is far longer than the current evoked by acetylcholine under voltage clamp, suggesting recruitment of another conductance. Our earlier studies found bag cell neurons to display a voltage-dependent persistent Ca current. Hence, we hypothesized that this current is activated by the acetylcholine-induced depolarization and sought a selective Ca current blocker. Rapid Ca current evoked by 200-ms depolarizing steps in voltage-clamped cultured bag cell neurons demonstrated a concentration-dependent sensitivity to Ni, Co, Zn, and verapamil but not Cd or ω-conotoxin GIVa. Leak subtraction of Ca current evoked by 10-s depolarizing steps using the IC (concentration required to eliminate maximal current) of Ni, Co, Zn, or verapamil revealed persistent Ca current, demonstrating persistent current block. Only Co and Zn did not suppress the acetylcholine-induced current, although Zn appeared to impact additional channels. When Co was applied during an acetylcholine-induced depolarization, the amplitude was reduced; furthermore, protein kinase C activation, previously established to enhance the persistent Ca current, extended the depolarization. Therefore, the persistent Ca current sustains the acetylcholine-induced depolarization and may translate brief cholinergic input into afterdischarge initiation. This could be a general mechanism of triggering long-term change in activity with a short-lived input. Ionotropic acetylcholine receptors mediate brief synaptic communication, including in bag cell neurons of the sea snail . However, this study demonstrates that cholinergic depolarization can open a voltage-gated persistent Ca current, which extends the bag cell neuron response to acetylcholine. Bursting in these neuroendocrine cells results in hormone release and egg laying. Thus, this emphasizes the role of ionotropic signaling in reaching a depolarized level to engage Ca influx and perpetuating the activity necessary for behavior.
Topics: Animals; Aplysia; Acetylcholine; Neurons; Cholinergic Agents; Verapamil; Hormones; Calcium
PubMed: 36988203
DOI: 10.1152/jn.00429.2022 -
Research (Washington, D.C.) 2023Locomotion in mollusc is implemented by a pedal rolling wave, a type of axial locomotion. Well-studied examples of axial locomotion (pedal waves in larvae and body...
Locomotion in mollusc is implemented by a pedal rolling wave, a type of axial locomotion. Well-studied examples of axial locomotion (pedal waves in larvae and body waves in leech, lamprey, and fish) are generated in a segmented nervous system via activation of multiple coupled central pattern generators (CPGs). Pedal waves in molluscs, however, are generated by a single pedal ganglion, and it is unknown whether there are single or multiple CPGs that generate rhythmic activity and phase shifts between different body parts. During locomotion in intact , bursting activity in the parapedal commissural nerve (PPCN) was found to occur during tail contraction. A cluster of 20 to 30 P1 root neurons (P1Ns) on the ventral surface of the pedal ganglion, active during the pedal wave, were identified. Computational cluster analysis revealed that there are 2 phases to the motor program: phase I (centered around 168°) and phase II (centered around 357°). PPCN activity occurs during phase II. The majority of P1Ns are motoneurons. Coactive P1Ns tend to be electrically coupled. Two classes of pedal interneurons (PIs) were characterized. Class 1 (PI1 and PI2) is active during phase I. Their axons make a loop within the pedal ganglion and contribute to locomotor pattern generation. They are electrically coupled to P1Ns that fire during phase I. Class 2 (PI3) is active during phase II and innervates the contralateral pedal ganglion. PI3 may contribute to bilateral coordination. Overall, our findings support the idea that pedal waves are generated by a single CPG.
PubMed: 36930762
DOI: 10.34133/research.0060 -
Journal of Neurophysiology Apr 2023Noxious stimuli or injury can trigger long-lasting sensitization to non-nociceptive stimuli (referred to as allodynia in mammals). Long-term potentiation (LTP) of...
Noxious stimuli or injury can trigger long-lasting sensitization to non-nociceptive stimuli (referred to as allodynia in mammals). Long-term potentiation (LTP) of nociceptive synapses has been shown to contribute to nociceptive sensitization (hyperalgesia) and there is even evidence of heterosynaptic spread of LTP contributing to this type of sensitization. This study will focus on how activation of nociceptors elicits heterosynaptic LTP (hetLTP) in non-nociceptive synapses. Previous studies in the medicinal leech () have demonstrated that high-frequency stimulation (HFS) of nociceptors produces both homosynaptic LTP as well as hetLTP in non-nociceptive afferent synapses. This hetLTP involves endocannabinoid-mediated disinhibition of non-nociceptive synapses at the presynaptic level, but it is not clear if there are additional processes contributing to this synaptic potentiation. In this study, we found evidence for the involvement of postsynaptic level change and observed that postsynaptic -methyl-d-aspartate (NMDA) receptors (NMDARs) were required for this potentiation. Next, orthologs for known LTP signaling proteins, CamKII and PKCζ, were identified based on sequences from humans, mice, and the marine mollusk . In electrophysiological experiments, inhibitors of CamKII (AIP) and PKCζ (ZIP) were found to interfere with hetLTP. Interestingly, CamKII was found to be necessary for both induction and maintenance of hetLTP, whereas PKCζ was only necessary for maintenance. These findings show that activation of nociceptors can elicit a potentiation of non-nociceptive synapses through a process that involves both endocannabinoid-mediated disinhibition and NMDAR-initiated signaling pathways. Pain-related sensitization involves increases in signaling by non-nociceptive sensory neurons. This can allow non-nociceptive afferents to have access to nociceptive circuitry. In this study, we examine a form of synaptic potentiation in which nociceptor activity elicits increases in non-nociceptive synapses. This process involves endocannabinoids, "gating" the activation of NMDA receptors, which in turn activate CamKII and PKCζ. This study provides an important link in how nociceptive stimuli can enhance non-nociceptive signaling related to pain.
Topics: Humans; Animals; Mice; Long-Term Potentiation; Endocannabinoids; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Receptors, N-Methyl-D-Aspartate; Synapses; Pain; Mammals
PubMed: 36883763
DOI: 10.1152/jn.00494.2022 -
Proceedings of the National Academy of... Mar 2023The l- to d-amino acid residue isomerization of neuropeptides is an understudied post-translational modification found in animals across several phyla. Despite its...
The l- to d-amino acid residue isomerization of neuropeptides is an understudied post-translational modification found in animals across several phyla. Despite its physiological importance, little information is available regarding the impact of endogenous peptide isomerization on receptor recognition and activation. As a result, the full roles peptide isomerization play in biology are not well understood. Here, we identify that the allatotropin-related peptide (ATRP) signaling system utilizes l- to d-residue isomerization of one amino acid residue in the neuropeptide ligand to modulate selectivity between two distinct G protein-coupled receptors (GPCRs). We first identified a novel receptor for ATRP that is selective for the D2-ATRP form, which bears a single d-phenylalanine residue at position 2. Using cell-based receptor activation experiments, we then characterized the stereoselectivity of the two known ATRP receptors for both endogenous ATRP diastereomers, as well as for homologous toxin peptides from a carnivorous predator. We found that the ATRP system displayed dual signaling through both the Gα and Gα pathways, and each receptor was selectively activated by one naturally occurring ligand diastereomer over the other. Overall, our results provide insights into an unexplored mechanism by which nature regulates intercellular communication. Given the challenges in detecting l- to d-residue isomerization from complex mixtures de novo and in identifying receptors for novel neuropeptides, it is likely that other neuropeptide-receptor systems may also utilize changes in stereochemistry to modulate receptor selectivity in a manner similar to that discovered here.
Topics: Animals; Amino Acids; Isomerism; Ligands; Receptors, Neuropeptide; Phenylalanine; Aplysia
PubMed: 36877849
DOI: 10.1073/pnas.2217604120 -
Journal of Proteome Research Oct 2023Protein database search engines are an integral component of mass spectrometry-based peptidomic analyses. Given the unique computational challenges of peptidomics, many...
Protein database search engines are an integral component of mass spectrometry-based peptidomic analyses. Given the unique computational challenges of peptidomics, many factors must be taken into consideration when optimizing search engine selection, as each platform has different algorithms by which tandem mass spectra are scored for subsequent peptide identifications. In this study, four different database search engines, PEAKS, MS-GF+, OMSSA, and X! Tandem, were compared with and peptidomics data sets, and various metrics were assessed such as the number of unique peptide and neuropeptide identifications, and peptide length distributions. Given the tested conditions, PEAKS was found to have the highest number of peptide and neuropeptide identifications out of the four search engines in both data sets. Furthermore, principal component analysis and multivariate logistic regression were employed to determine whether specific spectral features contribute to false C-terminal amidation assignments by each search engine. From this analysis, it was found that the primary features influencing incorrect peptide assignments were the precursor and fragment ion / errors. Finally, an assessment employing a mixed species protein database was performed to evaluate search engine precision and sensitivity when searched against an enlarged search space containing human proteins.
Topics: Humans; Animals; Rats; Search Engine; Peptides; Algorithms; Tandem Mass Spectrometry; Neuropeptides; Databases, Protein; Software
PubMed: 36809008
DOI: 10.1021/acs.jproteome.2c00307 -
The FEBS Journal Jul 2023Recently, three proton channels (H ) have been identified and characterized in Aplysia californica (AcH 1-3). Focusing on AcH 1 and AcH 2, analysis of Transcriptome...
Recently, three proton channels (H ) have been identified and characterized in Aplysia californica (AcH 1-3). Focusing on AcH 1 and AcH 2, analysis of Transcriptome Shotgun Assembly and genomic databases of 91 molluscs identified H homologous channels in other molluscs: channels homologous to AcH 1 and to AcH 2 were found in 90 species (56 full-length sequences) and in 33 species (18 full-length sequences), respectively. Here, we report the discovery of a fourth distinct proton channel family, H 4. This new family has high homology to AcH 1 and AcH 2 and was identified only in bivalvian molluscs (13 species, 12 full-length sequences). Typically, these channels possess an extracellular S1-S2 loop of intermediate size (~ 20 amino acids) compared to the shorter loops of molluscan H 1 channels (~ 13 amino acids) and the much larger loops of molluscan H 2 channels (> 65 amino acids). The characteristic voltage-sensor motif in S4 possesses only two arginine residues with the common third arginine being replaced by a lysine. Moreover, H 4 channels are much smaller with only around 200 amino acids in total length. The smallest functional channel found so far in nature (189 amino acids) is expressed in the pacific oyster Crassostrea gigas (CgH 4) and might be considered an archetypical minimal proton channel. Functional expression and electrophysiological characterization demonstrated that CgH 4 shares distinctive hallmarks of other investigated proton channels as high proton selectivity, slow activation, and pH- and voltage-regulated gating. This work is the first description of a H 4 type channel, adding a new member to the recently expanded family of proton channels.
Topics: Animals; Ion Channels; Protons; Ion Channel Gating; Amino Acids; Arginine; Mollusca
PubMed: 36788452
DOI: 10.1111/febs.16751 -
The American Journal of Clinical... Apr 2023Although the belief that hypnotizability is a mental dysfunction has been refuted over time, there is still research today that seeks to explore and clarify this... (Observational Study)
Observational Study
Although the belief that hypnotizability is a mental dysfunction has been refuted over time, there is still research today that seeks to explore and clarify this preconception. The results of recent research indicate that, on the contrary, greater psychopathology is more frequent in subjects with low hypnotic susceptibility. Using the Stanford Hypnotic Susceptibility Scale type A (SHSS-A) for hypnotizability, Symptom Checklist-Revised (SCL-90-R) for psychopathology, and the Somatosensory Amplification Scale (SSAS) and Toronto Alexithymia Scale (TAS-20) for psychosomatic dimensions, we found no relationship between baseline psychopathology, alexithymia and hypnotizability in 69 subjects with chronic pain in this retrospective observational study. Psychopathology did not affect the 2-month outcomes of hypnotic suggestions for pain in terms of either pain (assess using Italian Pain Questionnaire), anxiety or depression (assessed through Hospital Anxiety and Depression Scale) scores. Furthermore, i) no relationships were found between hypnotizability and degree of either psychopathology or alexithymia, definitively eliminating any doubts about the belief that hypnosis is a mental dysfunction; ii) only single hypnotic phenomena (SHSS-A) could be linked to some psychopathological dimensions; iii) analgesia suggestions also acted on anxiety and depression; and iv) the use of hypnotic suggestions for analgesia revealed a close relationship between improvements in sensorial and evaluative dimensions of pain and mitigation of anxiety. Hypnosis thereby seems to be a powerful tool in psychosomatic medicine whose effects on mind and body are inextricably linked.
Topics: Humans; Chronic Pain; Affective Symptoms; Hypnosis; Analgesia; Mental Disorders
PubMed: 36749869
DOI: 10.1080/00029157.2022.2161868 -
Journal of Morphology Mar 2023The gill of Aplysia depilans consists of several wedge-shaped pinnules with a highly folded structure, differing from the typical ctenidial gills of mollusks. Light...
The gill of Aplysia depilans consists of several wedge-shaped pinnules with a highly folded structure, differing from the typical ctenidial gills of mollusks. Light microscopy and transmission electron microscopy were used to investigate this organ in juveniles and adults. In this species, the gill epithelium comprised ciliated, unciliated, and secretory cells. The ultrastructural analysis suggests other functions for the gill besides respiration. The deep cell membrane invaginations associated with mitochondria in the basal region of epithelium point to a role in ion regulation. Endocytosis and intracellular digestion were other activities detected in epithelial cells. In juveniles, an intranuclear crystalline structure was seen in some ciliated cells. The presence of an intranuclear crystalline structure was frequently associated with chromatin decondensation, swelling of the nuclear envelope and endoplasmic reticulum cisternae, and abundance of Golgi stacks. As these intranuclear inclusions were not found in the gill of the adult specimens, their occurrence in the two juveniles seems likely to be an anomalous condition whose cause cannot be established at the moment. Mucous cells were the most abundant secretory cells in the epithelium, but a few epithelial serous cells were also found. In addition, large protein-secreting subepithelial cells had the main cell body inserted in the connective tissue and a long thin neck crossing the epithelium. Mucous cells can be considered responsible for the production of the mucus layer that protects the epithelium, but the specific functions of the epithelial and subepithelial protein-secreting cells remain elusive. Below the epithelium, a layer of connective tissue with muscle cells lined the narrow hemolymph space. The connective tissue included cells with a large amount of rough endoplasmic reticulum cisternae. Bacteria were found on the surface of the gill, and the most abundant had a thin stalk for attachment to the epithelial cells.
Topics: Animals; Aplysia; Gills; Microscopy, Electron; Mollusca; Gastropoda; Epithelium
PubMed: 36719273
DOI: 10.1002/jmor.21562