Project description:Voltage gated calcium channels play a central role in regulating the electrical and biochemical properties of neurons and muscle cells. Cells coordinate the expression of voltage gated calcium channels with the expression of other proteins that regulate membrane potential and calcium homeostasis. We report that the C-terminus of CaV 1.2, an L-type calcium channel (LTC) contains a C-terminal fragment that translocates to the nucleus and regulates transcription. This calcium channel associated transcription factor (CCAT) associates with transcriptional co-regulators such as p54nrb/NonO and binds to endogenous promoters. CCAT regulates the expression of gap junctions, sodium calcium exchangers, NMDA receptors, potassium channels and other proteins that regulate neuronal signaling. Electrical activity and developmental processes regulate the nuclear localization of CCAT, suggesting that the CCAT integrates information about the number of LTCs with information about the developmental history and electrical activity of a cell. These findings provide the first evidence that voltage gated calcium channels can directly activate transcription and suggest a novel mechanism linking voltage gated channels to the function and differentiation of excitable cells. Keywords: Genetic modification Analysis
Project description:Voltage-gated sodium channels are responsible for the initiation and propagation of action potentials in excitable cells. While the channel is functional on its own, it is the transient and stable protein-protein interactions that modulate functional outcomes. AP-MS has been successfully applied to a number of ion channels. However to the best of our knowledge, no AP-MS study has been carried out on any member of the voltage-gated sodium channel family.
Project description:Using whole-cell patch clamp recording and unbiased gene expression profiling in rat dissociated hippocampal neurons cultured at high density, we demonstrate here that chronic activity blockade induced by the sodium channel blocker tetrodotoxin leads to a homeostatic increase in action potential firing and down-regulation of potassium channel genes. In addition, chronic activity blockade reduces total potassium current, as well as protein expression and current of voltage-gated Kv1 and Kv7 potassium channels, which are critical regulators of action potential firing. Importantly, inhibition of N-Methyl-D-Aspartate receptors alone mimics the effects of tetrodotoxin, including the elevation in firing frequency and reduction of potassium channel gene expression and current driven by activity blockade, whereas inhibition of L-type voltage-gated calcium channels has no effect.
Project description:Voltage gated calcium channels play a central role in regulating the electrical and biochemical properties of neurons and muscle cells. Cells coordinate the expression of voltage gated calcium channels with the expression of other proteins that regulate membrane potential and calcium homeostasis. We report that the C-terminus of CaV 1.2, an L-type calcium channel (LTC) contains a C-terminal fragment that translocates to the nucleus and regulates transcription. This calcium channel associated transcription factor (CCAT) associates with transcriptional co-regulators such as p54nrb/NonO and binds to endogenous promoters. CCAT regulates the expression of gap junctions, sodium calcium exchangers, NMDA receptors, potassium channels and other proteins that regulate neuronal signaling. Electrical activity and developmental processes regulate the nuclear localization of CCAT, suggesting that the CCAT integrates information about the number of LTCs with information about the developmental history and electrical activity of a cell. These findings provide the first evidence that voltage gated calcium channels can directly activate transcription and suggest a novel mechanism linking voltage gated channels to the function and differentiation of excitable cells. Experiment Overall Design: The goal of these experiments was to identify the genes that are regulated by CCAT, a novel transcription factor derived from the C-terminus of CaV1.2. Neuro2A neuroblastoma cells were transfected with the last 503 AA of CaV1.2 which is full length CCAT (CCAT FL) or with the last 280 AA of CaV1.2, a form of CCAT that lacks the transcriptional activation domain (CCAT DTA). The mRNA from either CCAT FL or CCAT DTA expressing cells was hybridized to Agilent mouse genome microarrays along with mRNA from untransfected neuro2A cells (CCAT FL or DTA A series). Subsequent investigation revealed that transfection with the PA1 plasmid by itself increases the expression of some genes. To control for this effect we compared Neuro2A cells transfected with full length CCAT (in PA1) with Neuro2A cells transfectected with PA1 alone (CCAT FL B series). The microarray data was analyzed with the Rossetta Luminator gene expression data analysis system.
Project description:Spider venoms are a unique source of bioactive peptides displaying remarkable structural stability and potent neuroactivity. Phoneutria nigriventer, often referred to as Brazilian wandering spider, banana spider or “armed” spider, is endemic from South America and amongst the most dangerous venomous spiders in the world. Envenomation accidents with P. nigriventer often occur in Brazil with approximately 4,000 cases per year and which symptoms include priapism, hypertension, blurred vision, sweating, and vomiting, amongst others. Besides its clinical relevance, P. nigriventer venom comprises promising peptide drug leads providing therapeutic effects in a range of disease models. In this study, we further explored the neuroactivity and molecular diversity of the venom from P. nigriventer using fractionation-guided high-throughput cellular assays coupled to proteomics analysis and multi-pharmacology activity to broaden the knowledge and therapeutic potential of this venom, as well as a proof-of-concept for an investigative pipeline to study spider-venom derived neuroactive peptides. We applied ion channel assays in a neuroblastoma cell line to investigate modulation of voltage-gated sodium and calcium channels, and nicotinic acetylcholine α7 receptor. We then investigated the venom components using mass spectrometry to identify peptide masses and sequences associated to the observed neuromodulations. Our findings showed this venom is highly complex compared to other neurotoxin-rich venoms and comprises potent modulators of voltage-gated sodium and calcium channels which were classified into 4 families of neuroactive peptides based on their activities and structures. In addition to the reported P. nigriventer neuroactive peptides, we identified at least 27 novel cysteine-rich venom peptides in which neuroactivities are still to be elucidated in voltage-gated ion channels and other potential targets. Our findings provide a new basis for studying non-explored bioactivities of known and novel neuroactive components in P. nigriventer venom, and further supports the successful application of our discovery pipeline for identifying ion channel-targeting venom peptides with potential to become drug leads with diverse exploratory and therapeutic applications.
Project description:To explore the molecular basis of the distinct intrinsic membrane properties and other dstinguishing features of functionally defined DRG neuron subtypes, we bulk-sequenced RNA at high depth of genetically-labeled DRG neurons to generate transcriptome profiles of eight major DRG neuron subtypes. The trancriptome profiles revealed differentially expressed and functionally relevant genes, including voltage-gated ion channels. Guided by the transcriptome pofiles, electrophysiological analyses using pharmacological and genetic manipulations as well as computational modeling of DRG neuron subtypes were undertaken to assess the functions of select voltage-gated potassium channels (Kv1, Kv2, Kv3, and Kv4) in shaping action potential (AP) waveforms and firing patterns of the DRG neuron subtypes. Our findings show that the transcriptome profiles have predictive value for defining ion channel contributions to sensory neuron subtype-specific intrinsic physiological properties.
Project description:The cellular and molecular actions of general anaesthetics to induce anaesthesia state and also cellular signalling changes for subsequent potential “long term” effects remain largely elusive although great efforts have been made to study these in vitro, ex vivo and in vivo settings. General anaesthetics were reported to act on voltage-gated ion channels and ligand-gated ion channels. Here we used single-cell RNA-sequencing complemented with whole-cell patch clamp and calcium transient techniques to examine the gene transcriptome and ion channels profiling of sevoflurane and propofol, both commonly used clinically, on human embryonic primary prefrontal cortex (PFC) mixed cell cultures. Both propofol and sevoflurane at clinically relevant dose/concentration promoted “microgliosis” but only sevoflurane changed microglia cell similarity. Propofol and sevoflurane each extensively but transiently altered transcriptome profiling 2 hours after anaesthetics exposure across microglia, excitatory neurons, interneurons, astrocytes and oligodendrocyte progenitor cells. Within the excitatory neurons and microglia, exemplary ion-gated and ligand-gated ion channels related genes response to either anaesthetic included SCN1A, CACNAB2, KCNA1, GABRR2 and GRINA1 amongst many others. Utilising scRNA-seq as a robust and high-throughput tool, our work may provide a comprehensive blueprint for future mechanistic studies of general anaesthetics in clinically relevant settings.
Project description:Drosophila voltage-gated sodium channels are only expressed in active neurons and are localized to distal axonal initial segment-like domains