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Cells Jan 2024has been implicated in Autism Spectrum Disorders (ASDs) and/or intellectual disability, where copy-number-variant losses or loss-of-function coding mutations segregate...
has been implicated in Autism Spectrum Disorders (ASDs) and/or intellectual disability, where copy-number-variant losses or loss-of-function coding mutations segregate with disease in an X-linked recessive fashion. Missense variants of have also been reported in patients. However, the significance of these mutations remains undetermined since the activities, subcellular localization, and regulation of the PTCHD1 protein are currently unknown. This paucity of data concerning PTCHD1 prevents the effective evaluation of sequence variants identified during diagnostic screening. Here, we characterize PTCHD1 protein binding partners, extending previously reported interactions with postsynaptic scaffolding protein, SAP102. Six rare missense variants of PTCHD1 were also identified from patients with neurodevelopmental disorders. After modelling these variants on a hypothetical three-dimensional structure of PTCHD1, based on the solved structure of NPC1, PTCHD1 variants harboring these mutations were assessed for protein stability, post-translational processing, and protein trafficking. We show here that the wild-type PTCHD1 post-translational modification includes complex -glycosylation and that specific mutant proteins disrupt normal -link glycosylation processing. However, regardless of their processing, these mutants still localized to PSD95-containing dendritic processes and remained competent for complexing SAP102.
Topics: Humans; Intellectual Disability; Autism Spectrum Disorder; Glycosylation; Membrane Proteins; Mutation; Protein Stability
PubMed: 38275824
DOI: 10.3390/cells13020199 -
Cell & Bioscience Jan 2024Rasal1 is a Ras GTPase-activating protein which contains C2 domains necessary for dynamic membrane association following intracellular calcium elevation. Membrane-bound...
BACKGROUND
Rasal1 is a Ras GTPase-activating protein which contains C2 domains necessary for dynamic membrane association following intracellular calcium elevation. Membrane-bound Rasal1 inactivates Ras signaling through its RasGAP activity, and through such mechanisms has been implicated in regulating various cellular functions in the context of tumors. Although highly expressed in the brain, the contribution of Rasal1 to neuronal development and function has yet to be explored.
RESULTS
We examined the contributions of Rasal1 to neuronal development in primary culture of hippocampal neurons through modulation of Rasal1 expression using molecular tools. Fixed and live cell imaging demonstrate diffuse expression of Rasal1 throughout the cell soma, dendrites and axon which localizes to the neuronal plasma membrane in response to intracellular calcium fluctuation. Pull-down and co-immunoprecipitation demonstrate direct interaction of Rasal1 with PKC, tubulin, and CaMKII. Consequently, Rasal1 is found to stabilize microtubules, through post-translational modification of tubulin, and accordingly inhibit dendritic outgrowth and branching. Through imaging, molecular, and electrophysiological techniques Rasal1 is shown to promote NMDA-mediated synaptic activity and CaMKII phosphorylation.
CONCLUSIONS
Rasal1 functions in two separate roles in neuronal development; calcium regulated neurite outgrowth and the promotion of NMDA receptor-mediated postsynaptic events which may be mediated both by interaction with direct binding partners or calcium-dependent regulation of down-stream pathways. Importantly, the outlined molecular mechanisms of Rasal1 may contribute notably to normal neuronal development and synapse formation.
PubMed: 38246997
DOI: 10.1186/s13578-024-01193-w -
Frontiers in Physiology 2023The plus-end directed actin-dependent motor protein, myosin Va, is of particular relevance for outward vesicular protein trafficking and for restraining specific cargo... (Review)
Review
The plus-end directed actin-dependent motor protein, myosin Va, is of particular relevance for outward vesicular protein trafficking and for restraining specific cargo vesicles within the actin cortex. The latter is a preferred site of cAMP production, and the specificity of cAMP signaling is largely mediated through the formation of microdomains that spatially couple localized metabotropic receptor activity and cAMP production to selected effectors and downstream targets. This review summarizes the core literature on the role of myosin Va for the creation of such a cAMP microdomain at the mammalian nerve-muscle synapse that serves the activity-dependent recycling of nicotinic acetylcholine receptors (nAChRs)-a principal ligand-gated ion channel which is imperative for voluntary muscle contraction. It is discussed that i) the nerve-muscle synapse is a site with a unique actin-dependent microstructure, ii) myosin Va and protein kinase A regulatory subunit Iα as well as nAChR and its constitutive binding partner, rapsyn, colocalize in endocytic/recycling vesicles near the postsynaptic membrane, and iii) impairment of myosin Va or displacement of protein kinase A regulatory subunit Iα leads to the loss of nAChR stability. Regulation of this signaling process and underlying basic pieces of machinery were covered in previous articles, to which the present review refers.
PubMed: 38239886
DOI: 10.3389/fphys.2023.1342994 -
International Journal of Molecular... Dec 2023Synaptic plasticity enhances or reduces connections between neurons, affecting learning and memory. Postsynaptic AMPARs mediate greater than 90% of the rapid excitatory... (Review)
Review
Synaptic plasticity enhances or reduces connections between neurons, affecting learning and memory. Postsynaptic AMPARs mediate greater than 90% of the rapid excitatory synaptic transmission in glutamatergic neurons. The number and subunit composition of AMPARs are fundamental to synaptic plasticity and the formation of entire neural networks. Accordingly, the insertion and functionalization of AMPARs at the postsynaptic membrane have become a core issue related to neural circuit formation and information processing in the central nervous system. In this review, we summarize current knowledge regarding the related mechanisms of AMPAR expression and trafficking. The proteins related to AMPAR trafficking are discussed in detail, including vesicle-related proteins, cytoskeletal proteins, synaptic proteins, and protein kinases. Furthermore, significant emphasis was placed on the pivotal role of the actin cytoskeleton, which spans throughout the entire transport process in AMPAR transport, indicating that the actin cytoskeleton may serve as a fundamental basis for AMPAR trafficking. Additionally, we summarize the proteases involved in AMPAR post-translational modifications. Moreover, we provide an overview of AMPAR transport and localization to the postsynaptic membrane. Understanding the assembly, trafficking, and dynamic synaptic expression mechanisms of AMPAR may provide valuable insights into the cognitive decline associated with neurodegenerative diseases.
Topics: Receptors, AMPA; Central Nervous System; Neurons; Cognition; Learning; Central Nervous System Depressants
PubMed: 38203282
DOI: 10.3390/ijms25010111 -
Science Progress 2024Proton concentration can change within the cleft during synaptic activity due to vesicular release and Ca extrusion from cellular compartments. These changes within the...
Proton concentration can change within the cleft during synaptic activity due to vesicular release and Ca extrusion from cellular compartments. These changes within the synaptic cleft can impact neural activity by proton-dependent modulation of ion channel function. The pH transient differs in magnitude and direction between synapses, requiring different synapse types to be measured to generate a complete understanding of this mechanism and its impacts on physiology. With a focus on the mouse neuromuscular junction (NMJ), the recently published "Postsynaptic Calcium Extrusion at the Mouse Neuromuscular Junction Alkalinizes the Synaptic Cleft" measured synaptic cleft pH at a cholinergic synapse and found a biphasic pH transient. The study demonstrated that the changes in proton concentration found were due to postsynaptic signaling when measuring pH at the muscle membrane, despite the expectation of a presynaptic contribution. This result suggests a diffusional barrier within the NMJ isolates pH transients to presynaptic versus postsynaptic compartments. Generating a Donnan equilibrium that impacts protons, evidence suggests the basal lamina may be a key regulator of pH at the NMJ. Exploring synaptic pH, proton regulating factors, and downstream pH transient effects at presynaptic versus postsynaptic membranes may lead to new insight for a variety of diseases.
Topics: Animals; Mice; Basement Membrane; Protons; Neuromuscular Junction; Hydrogen-Ion Concentration; Signal Transduction
PubMed: 38196184
DOI: 10.1177/00368504231225066 -
Nature Communications Jan 2024Synapses are pivotal sites of plasticity and memory formation. Consequently, synapses are energy consumption hotspots susceptible to dysfunction when their energy...
Synapses are pivotal sites of plasticity and memory formation. Consequently, synapses are energy consumption hotspots susceptible to dysfunction when their energy supplies are perturbed. Mitochondria are stabilized near synapses via the cytoskeleton and provide the local energy required for synaptic plasticity. However, the mechanisms that tether and stabilize mitochondria to support synaptic plasticity are unknown. We identified proteins exclusively tethering mitochondria to actin near postsynaptic spines. We find that VAP, the vesicle-associated membrane protein-associated protein implicated in amyotrophic lateral sclerosis, stabilizes mitochondria via actin near the spines. To test if the VAP-dependent stable mitochondrial compartments can locally support synaptic plasticity, we used two-photon glutamate uncaging for spine plasticity induction and investigated the induced and adjacent uninduced spines. We find VAP functions as a spatial stabilizer of mitochondrial compartments for up to ~60 min and as a spatial ruler determining the ~30 μm dendritic segment supported during synaptic plasticity.
Topics: Actins; Dendritic Spines; Neuronal Plasticity; Synapses; Mitochondria
PubMed: 38177103
DOI: 10.1038/s41467-023-44233-8 -
Molecular Pain 2024Repeated use of opioid analgesics may cause a paradoxically exacerbated pain known as opioid-induced hyperalgesia (OIH), which hinders effective clinical intervention...
Repeated use of opioid analgesics may cause a paradoxically exacerbated pain known as opioid-induced hyperalgesia (OIH), which hinders effective clinical intervention for severe pain. Currently, little is known about the neural circuits underlying OIH modulation. Previous studies suggest that laterocapsular division of the central nucleus of amygdala (CeLC) is critically involved in the regulation of OIH. Our purpose is to clarify the role of the projections from infralimbic medial prefrontal cortex (IL) to CeLC in OIH. We first produced an OIH model by repeated fentanyl subcutaneous injection in male rats. Immunofluorescence staining revealed that c-Fos-positive neurons were significantly increased in the right CeLC in OIH rats than the saline controls. Then, we used calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) labeling and the patch-clamp recordings with ex vivo optogenetics to detect the functional projections from glutamate pyramidal neurons in IL to the CeLC. The synaptic transmission from IL to CeLC, shown in the excitatory postsynaptic currents (eEPSCs), inhibitory postsynaptic currents (eIPSCs) and paired-pulse ratio (PPR), was observably enhanced after fentanyl administration. Moreover, optogenetic activation of this IL-CeLC pathway decreased c-Fos expression in CeLC and ameliorated mechanical and thermal pain in OIH. On the contrary, silencing this pathway by chemogenetics exacerbated OIH by activating the CeLC. Combined with the electrophysiology results, the enhanced synaptic transmission from IL to CeLC might be a cortical gain of IL to relieve OIH rather than a reason for OIH generation. Scaling up IL outputs to CeLC may be an effective neuromodulation strategy to treat OIH.
Topics: Rats; Male; Animals; Hyperalgesia; Analgesics, Opioid; Rats, Sprague-Dawley; Amygdala; Pain; Fentanyl; Prefrontal Cortex
PubMed: 38172075
DOI: 10.1177/17448069241226960 -
Research Square Dec 2023Adolescence, a developmental stage, is characterized by psychosocial and biological changes. The nucleus accumbens (NAc), a striatal brain region composed of the core...
BACKGROUND
Adolescence, a developmental stage, is characterized by psychosocial and biological changes. The nucleus accumbens (NAc), a striatal brain region composed of the core (NAcC) and shell (NAcSh), has been linked to risk-taking behavior and implicated in reward seeking and evaluation. Most neurons in the NAc are medium spiny neurons (MSNs) that express dopamine D1 receptors (D1R+) and/or dopamine D2 receptors (D2R+). Changes in dopaminergic and glutamatergic systems occur during adolescence and converge in the NAc. While there are previous investigations into sex differences in membrane excitability and synaptic glutamate transmission in both subdivisions of the NAc, to our knowledge, none have specified NAcSh D1R+MSNs from mice during mid-adolescence.
METHODS
Sagittal brain slices containing the NAc were prepared from B6.Cg-Tg(Drd1a-tdTomato)6Calak/J mice of both sexes from postnatal days 35-47. Stained smears were made from vaginal samples from female mice to identify the stage of Estrous at death. Whole-cell electrophysiology recordings were collected from NAcSh D1R+MSNs in the form of membrane-voltage responses to current injections and spontaneous excitatory postsynaptic currents (sEPSCs).
RESULTS
The action potential duration was longer in males than infemales. Additionally, the frequency of sEPSCs was higher in females, and the mean event amplitude was smaller than that in males. We found no evidence of the observed sex differences being driven by the stage of the Estrous cycle and no physiological parameter significantly varied with respect to the Estrous cycle.
CONCLUSIONS
Taken together, our results indicate that NAcSh D1R+MSNs exhibit sex differences during mid-adolescence that are independent of the stage of Estrous, in both AP waveform and glutamate transmission, possibly due to changes in voltage-gated potassium channels and α-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors, respectively.
PubMed: 38168228
DOI: 10.21203/rs.3.rs-3717874/v1 -
ENeuro Jan 2024Gordon Holmes syndrome (GHS) is a neurological disorder associated with neuroendocrine, cognitive, and motor impairments with corresponding neurodegeneration. Mutations...
Gordon Holmes syndrome (GHS) is a neurological disorder associated with neuroendocrine, cognitive, and motor impairments with corresponding neurodegeneration. Mutations in the E3 ubiquitin ligase are strongly linked to GHS. Previous studies show that deletion of in mice led to sex-specific neuroendocrine dysfunction due to disruptions in the hypothalamic-pituitary-gonadal axis. To address RNF216 action in cognitive and motor functions, we tested knock-out (KO) mice in a battery of motor and learning tasks for a duration of 1 year. Although male and female KO mice did not demonstrate prominent motor phenotypes, KO females displayed abnormal limb clasping. KO mice also showed age-dependent strategy and associative learning impairments with sex-dependent alterations of microglia in the hippocampus and cortex. Additionally, KO males but not females had more negative resting membrane potentials in the CA1 hippocampus without any changes in miniature excitatory postsynaptic current (mEPSC) frequencies or amplitudes. Our findings show that constitutive deletion of alters microglia and neuronal excitability, which may provide insights into the etiology of sex-specific impairments in GHS.
Topics: Male; Female; Mice; Animals; Microglia; Cerebellar Ataxia; Mice, Knockout; Cognition; Ubiquitin-Protein Ligases; Hypogonadism; Gonadotropin-Releasing Hormone
PubMed: 38164552
DOI: 10.1523/ENEURO.0074-23.2023 -
Arquivos de Neuro-psiquiatria Dec 2023The nerve terminal and muscle membrane compose the neuromuscular junction. After opening the voltage-gated calcium channels, action potentials from the motor axons... (Review)
Review
The nerve terminal and muscle membrane compose the neuromuscular junction. After opening the voltage-gated calcium channels, action potentials from the motor axons provoke a cascade for the acetylcholine release from synaptic vesicles to the synaptic cleft, where it binds to its receptor at the muscle membrane for depolarization. Low amplitude compound muscle action potential typically presents in presynaptic disorders, increasing by more than 100% after a 10-second effort in the Lambert-Eaton myasthenic syndrome and less in botulism. Needle electromyography may show myopathic motor unit action potentials and morphological instability ("") due to impulse blocking. Low-frequency repetitive nerve stimulation (RNS) is helpful in postsynaptic disorders, such as myasthenia gravis and most congenital myasthenic syndromes, where the number of functioning acetylcholine receptors is reduced. Low-frequency RNS with a decrement >10% is abnormal when comparing the 4th to the first compound muscle action potential amplitude. High-frequency RNS is helpful in presynaptic disorders like Lambert-Eaton myasthenic syndrome, botulism, and some rare congenital myasthenic syndromes. The high-frequency RNS releases more calcium, increasing the acetylcholine with a compound muscle action potential increment. Concentric needle records single-fiber action potentials (spikes). A voluntary activation measures the jitter between spikes from two endplates. An electrical activation measures the jitter of one spike (one endplate). The jitter is the most sensitive test for detecting a neuromuscular junction dysfunction. Most neuromuscular junction disorders are responsive to treatment.
Topics: Humans; Lambert-Eaton Myasthenic Syndrome; Myasthenic Syndromes, Congenital; Botulism; Acetylcholine; Neuromuscular Junction; Electromyography
PubMed: 38157872
DOI: 10.1055/s-0043-1777749