1
|
Andreyanov M, Heinrich R, Berlin S. Design of Ultrapotent Genetically Encoded Inhibitors of Kv4.2 for Gating Neural Plasticity. J Neurosci 2024; 44:e2295222023. [PMID: 38154956 PMCID: PMC10869153 DOI: 10.1523/jneurosci.2295-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 11/05/2023] [Accepted: 11/22/2023] [Indexed: 12/30/2023] Open
Abstract
The Kv4.2 potassium channel plays established roles in neuronal excitability, while also being implicated in plasticity. Current means to study the roles of Kv4.2 are limited, motivating us to design a genetically encoded membrane tethered Heteropodatoxin-2 (MetaPoda). We find that MetaPoda is an ultrapotent and selective gating-modifier of Kv4.2. We narrow its site of contact with the channel to two adjacent residues within the voltage sensitive domain (VSD) and, with docking simulations, suggest that the toxin binds the VSD from within the membrane. We also show that MetaPoda does not require an external linker of the channel for its activity. In neurons (obtained from female and male rat neonates), MetaPoda specifically, and potently, inhibits all Kv4 currents, leaving all other A-type currents unaffected. Inhibition of Kv4 in hippocampal neurons does not promote excessive excitability, as is expected from a simple potassium channel blocker. We do find that MetaPoda's prolonged expression (1 week) increases expression levels of the immediate early gene cFos and prevents potentiation. These findings argue for a major role of Kv4.2 in facilitating plasticity of hippocampal neurons. Lastly, we show that our engineering strategy is suitable for the swift engineering of another potent Kv4.2-selective membrane-tethered toxin, Phrixotoxin-1, denoted MetaPhix. Together, we provide two uniquely potent genetic tools to study Kv4.2 in neuronal excitability and plasticity.
Collapse
Affiliation(s)
- Michael Andreyanov
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa 3525433, Israel
| | - Ronit Heinrich
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa 3525433, Israel
| | - Shai Berlin
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa 3525433, Israel
| |
Collapse
|
2
|
Sodero AO, Rodriguez-Silva M, Salio C, Sassoè-Pognetto M, Chambers JW. Sab is differentially expressed in the brain and affects neuronal activity. Brain Res 2017; 1670:76-85. [PMID: 28606781 DOI: 10.1016/j.brainres.2017.06.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 06/01/2017] [Accepted: 06/03/2017] [Indexed: 01/27/2023]
Abstract
Sab (SH3 binding protein 5 or SH3BP5) is a mitochondrial scaffold protein involved in signaling associated with mitochondrial dysfunction and apoptosis; furthermore, Sab is a crucial signaling platform for neurodegenerative disease. To determine how this signaling nexus could have a significant effect on disease, we examined the regional abundance of Sab in the brain and sub-neuronal distribution, and we monitored the effect of Sab-mediated signaling on neuronal activity. We found that Sab is widely expressed in the adult mouse brain with increased abundance in hippocampus, ventral midbrain, and cerebellum. Sab was found in purified synaptosomes and in cultures of hippocampal neurons and astrocytes. Confocal and electron microscopy of mouse hippocampal sections confirmed the mitochondrial localization of Sab in the soma, dendrites, and axons. Given the localization and sub-neuronal distribution of Sab, we postulated that Sab-mediated signaling could affect neuronal function, so we measured the impact of inhibiting Sab-mediated events on the spontaneous activity in cultured hippocampal neurons. Treatment with a Sab-inhibitory peptide (Tat-SabKIM1), but not a scrambled control peptide, decreased the firing frequency and spike amplitudes. Our results demonstrate that brain-specific Sab-mediated signaling plays a role in neuronal activity through the manipulation of mitochondrial physiology by interacting kinases.
Collapse
Affiliation(s)
- Alejandro O Sodero
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, United States
| | - Monica Rodriguez-Silva
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, United States
| | - Chiara Salio
- Department of Veterinary Sciences, University of Turin, Italy
| | | | - Jeremy W Chambers
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, United States; Department of Neuroscience, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, United States; Biomolecular Sciences Institute, Florida International University, Miami, FL 33199, United States.
| |
Collapse
|
3
|
Pál I, Kardos J, Dobolyi Á, Héja L. Appearance of fast astrocytic component in voltage-sensitive dye imaging of neural activity. Mol Brain 2015; 8:35. [PMID: 26043770 PMCID: PMC4455916 DOI: 10.1186/s13041-015-0127-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 05/24/2015] [Indexed: 12/21/2022] Open
Abstract
Background Voltage-sensitive dye (VSD) imaging and intrinsic optical signals (IOS) are widely used methods for monitoring spatiotemporal neural activity in extensive networks. In spite of that, identification of their major cellular and molecular components has not been concluded so far. Results We addressed these issues by imaging spatiotemporal spreading of IOS and VSD transients initiated by Schaffer collateral stimulation in rat hippocampal slices with temporal resolution comparable to standard field potential recordings using a 464-element photodiode array. By exploring the potential neuronal and astroglial molecular players in VSD and IOS generation, we identified multiple astrocytic mechanisms that significantly contribute to the VSD signal, in addition to the expected neuronal targets. Glutamate clearance through the astroglial glutamate transporter EAAT2 has been shown to be a significant player in VSD generation within a very short (<5 ms) time-scale, indicating that astrocytes do contribute to the development of spatiotemporal VSD transients previously thought to be essentially neuronal. In addition, non-specific anion channels, astroglial K+ clearance through Kir4.1 channel and astroglial Na+/K+ ATPase also contribute to IOS and VSD transients. Conclusion VSD imaging cannot be considered as a spatially extended field potential measurement with predominantly neuronal origin, instead it also reflects a fast communication between neurons and astrocytes.
Collapse
Affiliation(s)
- Ildikó Pál
- Group of Functional Pharmacology, Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117, Budapest, Hungary.
| | - Julianna Kardos
- Group of Functional Pharmacology, Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117, Budapest, Hungary.
| | - Árpád Dobolyi
- MTA-ELTE-NAP B Laboratory of Molecular and Systems Neurobiology, H-1117, Budapest, Hungary. .,Department of Anatomy, Human Brain Tissue Bank, Semmelweis University, H-1450, Budapest, Hungary.
| | - László Héja
- Group of Functional Pharmacology, Institute of Cognitive Neuroscience and Psychology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117, Budapest, Hungary.
| |
Collapse
|
4
|
Bazzigaluppi P, Dufour S, Carlen PL. Wide field fluorescent imaging of extracellular spatiotemporal potassium dynamics in vivo. Neuroimage 2014; 104:110-6. [PMID: 25312775 DOI: 10.1016/j.neuroimage.2014.10.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 10/03/2014] [Accepted: 10/04/2014] [Indexed: 11/18/2022] Open
Abstract
Potassium homeostasis is fundamental for the physiological functioning of the brain. Increased [K(+)] in the extracellular fluid has a major impact on neuronal physiology and can lead to ictal events. Compromised regulation of extracellular [K(+)] is involved in generation of seizures in animal models and potentially also in humans. For this reason, the investigation of K(+) spatio-temporal dynamics is of fundamental importance for neuroscientists in the field of epilepsy and other related pathologies. To date, the majority of studies investigating changes in extracellular K(+) have been conducted using a micropipette filled with a K(+) sensitive solution. However, this approach presents a major limitation: the area of the measurement is circumscribed to the tip of the pipette and it is not possible to know the spatiotemporal distribution or origin of the focally measured K(+) signal. Here we propose a novel approach, based on wide field fluorescence, to measure extracellular K(+) dynamics in neural tissue. Recording the local field potential from the somatosensory cortex of the mouse, we compared responses obtained from a K(+)-sensitive microelectrode to the spatiotemporal increases in fluorescence of the fluorophore, Asante Potassium Green-2, in physiological conditions and during 4-AP induced ictal activity. We conclude that wide field imaging is a valuable and versatile tool to measure K(+) dynamics over a large area of the cerebral cortex and is capable of capturing fast dynamics such as during ictal events. Moreover, the present technique is potentially adaptable to address questions regarding spatiotemporal dynamics of other ionic species.
Collapse
Affiliation(s)
- Paolo Bazzigaluppi
- Toronto Western Research Institute, Toronto, Canada; Sunnybrook Research Center, Toronto, Canada.
| | - Suzie Dufour
- Toronto Western Research Institute, Toronto, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| | - Peter L Carlen
- Toronto Western Research Institute, Toronto, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
| |
Collapse
|
5
|
Witthoft A, Filosa JA, Karniadakis GE. Potassium buffering in the neurovascular unit: models and sensitivity analysis. Biophys J 2014; 105:2046-54. [PMID: 24209849 DOI: 10.1016/j.bpj.2013.09.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/20/2013] [Accepted: 09/10/2013] [Indexed: 12/01/2022] Open
Abstract
Astrocytes are critical regulators of neural and neurovascular network communication. Potassium transport is a central mechanism behind their many functions. Astrocytes encircle synapses with their distal processes, which express two potassium pumps (Na-K and NKCC) and an inward rectifying potassium channel (Kir), whereas the vessel-adjacent endfeet express Kir and BK potassium channels. We provide a detailed model of potassium flow throughout the neurovascular unit (synaptic region, astrocytes, and arteriole) for the cortex of the young brain. Our model reproduces several phenomena observed experimentally: functional hyperemia, in which neural activity triggers astrocytic potassium release at the perivascular endfoot, inducing arteriole dilation; K(+) undershoot in the synaptic space after periods of neural activity; neurally induced astrocyte hyperpolarization during Kir blockade. Our results suggest that the dynamics of the vascular response during functional hyperemia are governed by astrocytic Kir for the fast onset and astrocytic BK for maintaining dilation. The model supports the hypothesis that K(+) undershoot is caused by excessive astrocytic uptake through Na-K and NKCC pumps, whereas the effect is balanced by Kir. We address parametric uncertainty using high-dimensional stochastic sensitivity analysis and identify possible model limitations.
Collapse
|
6
|
Tønnesen J, Kokaia M. Electrophysiological investigations of synaptic connectivity between host and graft neurons. PROGRESS IN BRAIN RESEARCH 2013. [PMID: 23195416 DOI: 10.1016/b978-0-444-59575-1.00005-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The functional synaptic integration of grafted stem cell-derived neurons is one of the key aspects of neural cell replacement therapies for neurological disorders such as Parkinson's disease. However, little is currently known about the synaptic connectivity between graft and host cells after transplantation, not only in the settings of clinical trials but also in experimental studies. This knowledge gap is primarily due to the lack of experimental electrophysiological approaches allowing interrogation of synaptic connectivity between prospectively identified host and graft neurons and hampers our understanding of the mechanisms underlying functional integration of stem cell-derived neurons in the host brain, as well as the optimization of protocols for deriving stem cells for neural cell replacement therapy. Recent optogenetic tools allow for direct investigation of connectivity between host and graft neural populations and have already been applied to show bidirectional integration of dopaminergic neurons in a host tissue. These new tools have potential to advance our understanding of functional integration in the near future. Here, we provide an overview of the current literature addressing functional integration of stem cell-derived neurons in the settings of Parkinson's disease models and discuss some experimental paradigms to approach this issue.
Collapse
Affiliation(s)
- Jan Tønnesen
- Synaptic Plasticity and Superresolution Microscopy Group, Interdisciplinary Institute for Neurosciences, Université de Bordeaux Segalen, Bordeaux, France
| | | |
Collapse
|
7
|
Pál I, Nyitrai G, Kardos J, Héja L. Neuronal and astroglial correlates underlying spatiotemporal intrinsic optical signal in the rat hippocampal slice. PLoS One 2013; 8:e57694. [PMID: 23469218 PMCID: PMC3585794 DOI: 10.1371/journal.pone.0057694] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 01/28/2013] [Indexed: 11/24/2022] Open
Abstract
Widely used for mapping afferent activated brain areas in vivo, the label-free intrinsic optical signal (IOS) is mainly ascribed to blood volume changes subsequent to glial glutamate uptake. By contrast, IOS imaged in vitro is generally attributed to neuronal and glial cell swelling, however the relative contribution of different cell types and molecular players remained largely unknown. We characterized IOS to Schaffer collateral stimulation in the rat hippocampal slice using a 464-element photodiode-array device that enables IOS monitoring at 0.6 ms time-resolution in combination with simultaneous field potential recordings. We used brief half-maximal stimuli by applying a medium intensity 50 Volt-stimulus train within 50 ms (20 Hz). IOS was primarily observed in the str. pyramidale and proximal region of the str. radiatum of the hippocampus. It was eliminated by tetrodotoxin blockade of voltage-gated Na(+) channels and was significantly enhanced by suppressing inhibitory signaling with gamma-aminobutyric acid(A) receptor antagonist picrotoxin. We found that IOS was predominantly initiated by postsynaptic Glu receptor activation and progressed by the activation of astroglial Glu transporters and Mg(2+)-independent astroglial N-methyl-D-aspartate receptors. Under control conditions, role for neuronal K(+)/Cl(-) cotransporter KCC2, but not for glial Na(+)/K(+)/Cl(-) cotransporter NKCC1 was observed. Slight enhancement and inhibition of IOS through non-specific Cl(-) and volume-regulated anion channels, respectively, were also depicted. High-frequency IOS imaging, evoked by brief afferent stimulation in brain slices provide a new paradigm for studying mechanisms underlying IOS genesis. Major players disclosed this way imply that spatiotemporal IOS reflects glutamatergic neuronal activation and astroglial response, as observed within the hippocampus. Our model may help to better interpret in vivo IOS and support diagnosis in the future.
Collapse
Affiliation(s)
- Ildikó Pál
- Department of Functional Pharmacology, Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary.
| | | | | | | |
Collapse
|
8
|
Functional synapse formation between compartmentalized cortical neurons cultured inside microfluidic devices. BIOCHIP JOURNAL 2011. [DOI: 10.1007/s13206-011-5401-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
|
9
|
Doyon N, Prescott SA, Castonguay A, Godin AG, Kröger H, De Koninck Y. Efficacy of synaptic inhibition depends on multiple, dynamically interacting mechanisms implicated in chloride homeostasis. PLoS Comput Biol 2011; 7:e1002149. [PMID: 21931544 PMCID: PMC3169517 DOI: 10.1371/journal.pcbi.1002149] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Accepted: 06/11/2011] [Indexed: 11/19/2022] Open
Abstract
Chloride homeostasis is a critical determinant of the strength and robustness of inhibition mediated by GABA(A) receptors (GABA(A)Rs). The impact of changes in steady state Cl(-) gradient is relatively straightforward to understand, but how dynamic interplay between Cl(-) influx, diffusion, extrusion and interaction with other ion species affects synaptic signaling remains uncertain. Here we used electrodiffusion modeling to investigate the nonlinear interactions between these processes. Results demonstrate that diffusion is crucial for redistributing intracellular Cl(-) load on a fast time scale, whereas Cl(-)extrusion controls steady state levels. Interaction between diffusion and extrusion can result in a somato-dendritic Cl(-) gradient even when KCC2 is distributed uniformly across the cell. Reducing KCC2 activity led to decreased efficacy of GABA(A)R-mediated inhibition, but increasing GABA(A)R input failed to fully compensate for this form of disinhibition because of activity-dependent accumulation of Cl(-). Furthermore, if spiking persisted despite the presence of GABA(A)R input, Cl(-) accumulation became accelerated because of the large Cl(-) driving force that occurs during spikes. The resulting positive feedback loop caused catastrophic failure of inhibition. Simulations also revealed other feedback loops, such as competition between Cl(-) and pH regulation. Several model predictions were tested and confirmed by [Cl(-)](i) imaging experiments. Our study has thus uncovered how Cl(-) regulation depends on a multiplicity of dynamically interacting mechanisms. Furthermore, the model revealed that enhancing KCC2 activity beyond normal levels did not negatively impact firing frequency or cause overt extracellular K(-) accumulation, demonstrating that enhancing KCC2 activity is a valid strategy for therapeutic intervention.
Collapse
Affiliation(s)
- Nicolas Doyon
- Division of Cellular and Molecular Neuroscience, Centre de recherche Université Laval Robert-Giffard, Québec, Québec, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, Québec, Canada
| | - Steven A. Prescott
- Department of Neurobiology and Pittsburgh Center for Pain Research, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Annie Castonguay
- Division of Cellular and Molecular Neuroscience, Centre de recherche Université Laval Robert-Giffard, Québec, Québec, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, Québec, Canada
| | - Antoine G. Godin
- Division of Cellular and Molecular Neuroscience, Centre de recherche Université Laval Robert-Giffard, Québec, Québec, Canada
| | - Helmut Kröger
- Department of Physics, Université Laval, Québec, Québec, Canada
| | - Yves De Koninck
- Division of Cellular and Molecular Neuroscience, Centre de recherche Université Laval Robert-Giffard, Québec, Québec, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, Québec, Canada
| |
Collapse
|
10
|
Saraga F, Balena T, Wolansky T, Dickson CT, Woodin MA. Inhibitory synaptic plasticity regulates pyramidal neuron spiking in the rodent hippocampus. Neuroscience 2008; 155:64-75. [PMID: 18562122 DOI: 10.1016/j.neuroscience.2008.05.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 05/07/2008] [Accepted: 05/09/2008] [Indexed: 11/17/2022]
Abstract
Spike-timing modifies the efficacy of both excitatory and inhibitory synapses onto CA1 pyramidal neurons in the rodent hippocampus. Repetitively spiking the presynaptic neuron before the postsynaptic neuron induces inhibitory synaptic plasticity, which results in a depolarization of the reversal potential for GABA (E(GABA)). Our goal was to determine how inhibitory synaptic plasticity regulates CA1 pyramidal neuron spiking in the rat hippocampus. We demonstrate electrophysiologically that depolarizing E(GABA) by 24.7 mV increased the spontaneous action potential firing frequency of cultured hippocampal neurons 254% from 0.12+/-0.07 Hz to 0.44+/-0.13 Hz (n=11; P<0.05). Next we used a single compartment model of a CA1 pyramidal neuron to explore in detail how inhibitory synaptic plasticity of feedforward and feedback inhibition regulates the generation of action potentials, spike latency, and the minimum excitatory conductance required to generate an action potential; plasticity was modeled as a depolarization of E(GABA), which effectively weakens inhibition. Depolarization of E(GABA) at feedforward and feedback inhibitory synapses decreased the latency to the 1st spike by 2.27 ms, which was greater that the sum of the decreases produced by depolarizing E(GABA) at feedforward (0.85 ms) or feedback inhibitory synapses (0.02 ms) alone. In response to a train of synaptic inputs, depolarizing E(GABA) decreased the inter-spike interval and increased the number of output spikes in a frequency dependent manner, improving the reliability of input-output transmission. Moreover, a depolarizing shift in E(GABA) at feedforward and feedback synapses triggered by spike trains recorded from CA1 pyramidal layer neurons during field theta from anesthetized rats, significantly increased spiking on the up- and down-strokes of the first half of the theta rhythm (P<0.05), without changing the preferred phase of firing (P=0.783). This study provides the first explanation of how depolarizing E(GABA) affects pyramidal cell output within the hippocampus.
Collapse
Affiliation(s)
- F Saraga
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
| | | | | | | | | |
Collapse
|