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Proceedings of the National Academy of... Jul 2022The gastropod mollusk is an important model for cellular and molecular neurobiological studies, particularly for investigations of molecular mechanisms of learning and...
The gastropod mollusk is an important model for cellular and molecular neurobiological studies, particularly for investigations of molecular mechanisms of learning and memory. We developed an optimized assembly pipeline to generate an improved nervous system transcriptome. This improved transcriptome enabled us to explore the evolution of cognitive capacity at the molecular level. Were there evolutionary expansions of neuronal genes between this relatively simple gastropod (20,000 neurons) and (500 million neurons), the invertebrate with the most elaborate neuronal circuitry and greatest behavioral complexity? Are the tremendous advances in cognitive power in vertebrates explained by expansion of the synaptic proteome that resulted from multiple rounds of whole genome duplication in this clade? Overall, the complement of genes linked to neuronal function is similar between and As expected, a number of synaptic scaffold proteins have more isoforms in humans than in or . However, several scaffold families present in mollusks and other protostomes are absent in vertebrates, including the Fifes, Lev10s, SOLs, and a NETO family. Thus, whereas vertebrates have more scaffold isoforms from select families, invertebrates have additional scaffold protein families not found in vertebrates. This analysis provides insights into the evolution of the synaptic proteome. Both synaptic proteins and synaptic plasticity evolved gradually, yet the last deuterostome-protostome common ancestor already possessed an elaborate suite of genes associated with synaptic function, and critical for synaptic plasticity.
Topics: Animals; Aplysia; Biological Evolution; Cognition; Neuronal Plasticity; Neurons; Protein Isoforms; Proteome; Synapses; Transcriptome
PubMed: 35867761
DOI: 10.1073/pnas.2122301119 -
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 -
Scientific Reports Jul 2017Doxorubicin (DOX), a common chemotherapeutic agent, impairs synaptic plasticity. DOX also causes a persistent increase in basal neuronal excitability, which occludes...
Doxorubicin (DOX), a common chemotherapeutic agent, impairs synaptic plasticity. DOX also causes a persistent increase in basal neuronal excitability, which occludes serotonin-induced enhanced excitability. Therefore, we sought to characterize and reverse DOX-induced physiological changes and modulation of molecules implicated in memory induction using sensory neurons from the marine mollusk Aplysia californica. DOX produced two mechanistically distinct phases of extracellular signal-regulated kinase (ERK) activation, an early and a late phase. Inhibition of MEK (mitogen-activated protein kinase (MAPK)/ERK kinase) after DOX treatment reversed the late ERK activation. MEK inhibition during treatment enhanced the late ERK activation possibly through prolonged downregulation of MAPK phosphatase-1 (MKP-1). Unexpectedly, the late ERK activation negatively correlated with excitability. MEK inhibition during DOX treatment simultaneously enhanced the late activation of ERK and blocked the increase in basal excitability. In summary, we report DOX-mediated biphasic activation of ERK and the reversal of the associated changes in neurons, a potential strategy for reversing the deleterious effects of DOX treatment.
Topics: Animals; Aplysia; Doxorubicin; Enzyme Activation; Evoked Potentials; Extracellular Signal-Regulated MAP Kinases; Sensory Receptor Cells; Signal Transduction; p38 Mitogen-Activated Protein Kinases
PubMed: 28674403
DOI: 10.1038/s41598-017-04634-4 -
Sleep Sep 2014To characterize sleep in the marine mollusk, Aplysia californica.
STUDY OBJECTIVE
To characterize sleep in the marine mollusk, Aplysia californica.
DESIGN
Animal behavior and activity were assessed using video recordings to measure activity, resting posture, resting place preference, and behavior after rest deprivation. Latencies for behavioral responses were measured for appetitive and aversive stimuli for animals in the wake and rest states.
SETTING
Circadian research laboratory for Aplysia.
PATIENTS OR PARTICIPANTS
A. californica from the Pacific Ocean.
INTERVENTIONS
N/A.
MEASUREMENTS AND RESULTS
Aplysia rest almost exclusively during the night in a semi-contracted body position with preferential resting locations in the upper corners of their tank. Resting animals demonstrate longer latencies in head orientation and biting in response to a seaweed stimulus and less frequent escape response steps following an aversive salt stimulus applied to the tail compared to awake animals at the same time point. Aplysia exhibit rebound rest the day following rest deprivation during the night, but not after similar handling stimulation during the day.
CONCLUSIONS
Resting behavior in Aplysia fulfills all invertebrate characteristics of sleep including: (1) a specific sleep body posture, (2) preferred resting location, (3) reversible behavioral quiescence, (4) elevated arousal thresholds for sensory stimuli during sleep, and (5) compensatory sleep rebound after sleep deprivation.
Topics: Animals; Aplysia; Appetitive Behavior; Arousal; Behavior, Animal; Circadian Rhythm; Darkness; Escape Reaction; Head; Locomotion; Models, Animal; Posture; Rest; Sleep; Sleep Deprivation; Time Factors; Video Recording; Wakefulness
PubMed: 25142567
DOI: 10.5665/sleep.3992 -
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 Feb 2023So far one gene for Hv1 has been detected in studied species. The work presented by Chaves et al. in The FEBS Journal reported an 'Unexpected expansion of the...
So far one gene for Hv1 has been detected in studied species. The work presented by Chaves et al. in The FEBS Journal reported an 'Unexpected expansion of the voltage-gated proton channel family'. They searched for proton channel candidates and found three sequences in the genome of Aplysia californica (Ac), which were named AcHv1, AcHv2 and AcHv3. Based on electrophysiological experiments, AcHv1 and AcHv2 are voltage-gated channels. While AcHv1 behaves like Hv1 in other species, that is, it is voltage and pH-dependent, it can be inhibited by zinc and conducts protons outwardly, AcHv2 conducts protons inwards at symmetrical pH. AcHv3 constantly leaks protons, and its C-terminal part contains several cytoplasmic retention motifs. Through carefully designed and carried out electrophysiological experiments, Chaves et al. determined the biophysical parameters of all three proton channels, such as the voltage and the pH dependence, the threshold-voltage, the gating charge and the time constants of activation and inactivation. Comment on: https://doi.org/10.1111/febs.16617.
Topics: Protons; Ion Channel Gating; Ion Channels; Zinc
PubMed: 36315610
DOI: 10.1111/febs.16670 -
Frontiers in Systems Neuroscience 2014Across phylogeny, the endogenous biological clock has been recognized as providing adaptive advantages to organisms through coordination of physiological and behavioral... (Review)
Review
Across phylogeny, the endogenous biological clock has been recognized as providing adaptive advantages to organisms through coordination of physiological and behavioral processes. Recent research has emphasized the role of circadian modulation of memory in generating peaks and troughs in cognitive performance. The circadian clock along with homeostatic processes also regulates sleep, which itself impacts the formation and consolidation of memory. Thus, the circadian clock, sleep and memory form a triad with ongoing dynamic interactions. With technological advances and the development of a global 24/7 society, understanding the mechanisms underlying these connections becomes pivotal for development of therapeutic treatments for memory disorders and to address issues in cognitive performance arising from non-traditional work schedules. Invertebrate models, such as Drosophila melanogaster and the mollusks Aplysia and Lymnaea, have proven invaluable tools for identification of highly conserved molecular processes in memory. Recent research from invertebrate systems has outlined the influence of sleep and the circadian clock upon synaptic plasticity. In this review, we discuss the effects of the circadian clock and sleep on memory formation in invertebrates drawing attention to the potential of in vivo and in vitro approaches that harness the power of simple invertebrate systems to correlate individual cellular processes with complex behaviors. In conclusion, this review highlights how studies in invertebrates with relatively simple nervous systems can provide mechanistic insights into corresponding behaviors in higher organisms and can be used to outline possible therapeutic options to guide further targeted inquiry.
PubMed: 25136297
DOI: 10.3389/fnsys.2014.00133 -
Threading the biophysics of mammalian Slo1 channels onto structures of an invertebrate Slo1 channel.The Journal of General Physiology Nov 2017For those interested in the machinery of ion channel gating, the Ca and voltage-activated BK K channel provides a compelling topic for investigation, by virtue of its... (Review)
Review
For those interested in the machinery of ion channel gating, the Ca and voltage-activated BK K channel provides a compelling topic for investigation, by virtue of its dual allosteric regulation by both voltage and intracellular Ca and because its large-single channel conductance facilitates detailed kinetic analysis. Over the years, biophysical analyses have illuminated details of the allosteric regulation of BK channels and revealed insights into the mechanism of BK gating, e.g., inner cavity size and accessibility and voltage sensor-pore coupling. Now the publication of two structures of an BK channel-one liganded and one metal free-promises to reinvigorate functional studies and interpretation of biophysical results. The new structures confirm some of the previous functional inferences but also suggest new perspectives regarding cooperativity between Ca-binding sites and the relationship between voltage- and Ca-dependent gating. Here we consider the extent to which the two structures explain previous functional data on pore-domain properties, voltage-sensor motions, and divalent cation binding and activation of the channel.
Topics: Animals; Aplysia; Humans; Ion Channel Gating; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
PubMed: 29025867
DOI: 10.1085/jgp.201711845 -
Journal of Molecular Neuroscience : MN Feb 2022Although Alzheimer's disease (AD) is the most common form of dementia in the United States, development of therapeutics has proven difficult. Invertebrate alternatives...
Although Alzheimer's disease (AD) is the most common form of dementia in the United States, development of therapeutics has proven difficult. Invertebrate alternatives to current mammalian AD models have been successfully employed to study the etiology of the molecular hallmarks of AD. The marine snail Aplysia californica offers a unique and underutilized system in which to study the physiological, behavioral, and molecular impacts of AD. Mapping of the Aplysia proteome to humans and cross-referencing with two databases of genes of interest in AD research identified 898 potential orthologs of interest in Aplysia. Included among these orthologs were alpha, beta and gamma secretases, amyloid-beta, and tau. Comparison of age-associated differential expression in Aplysia sensory neurons with that of late-onset AD in the frontal lobe identified 59 ortholog with concordant differential expression across data sets. The 21 concordantly upregulated genes suggested increased cellular stress and protein dyshomeostasis. The 47 concordantly downregulated genes included important components of diverse neuronal processes, including energy metabolism, mitochondrial homeostasis, synaptic signaling, Ca regulation, and cellular cargo transport. Compromised functions in these processes are known hallmarks of both human aging and AD, the ramifications of which are suggested to underpin cognitive declines in aging and neurodegenerative disease.
Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Aplysia; Humans; Mammals; Neurodegenerative Diseases; Neurons; tau Proteins
PubMed: 34664226
DOI: 10.1007/s12031-021-01918-3 -
ELife Nov 2020Sea slugs increase the longevity of the chloroplasts they steal from algae by limiting the harmful side-effects of photosynthesis.
Sea slugs increase the longevity of the chloroplasts they steal from algae by limiting the harmful side-effects of photosynthesis.
Topics: Animals; Aplysia; Chloroplasts; Gastropoda; Photosynthesis; Theft
PubMed: 33215989
DOI: 10.7554/eLife.64057