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Hetsch F, Wang D, Chen X, Zhang J, Aslam M, Kegel M, Tonner H, Grus F, von Engelhardt J. CKAMP44 controls synaptic function and strength of relay neurons during early development of the dLGN. J Physiol 2022; 600:3549-3565. [PMID: 35770953 DOI: 10.1113/jp283172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/27/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Expression of CKAMP44 starts early during development of the dLGN and remains stable in relay neurons and interneurons. Genetic deletion of CKAMP44 decreases synaptic strength and increases silent synapse number in dLGN relay neurons. Genetic deletion of CKAMP44 increases the rate of recovery from desensitisation of AMPA receptors in dLGN relay neurons. Genetic deletion of CKAMP44 reduces synaptic short-term depression in retinogeniculate synapses. The probability to induce plateau potentials is elevated in relay neurons of CKAMP44-/- mice. Eye-specific input segregation is unaffected in the dLGN of CKAMP44-/- mice. Deletion of CKAMP44 mildly affects dendritic arborisation of relay neurons in the dLGN. ABSTRACT Relay neurons of the dorsal lateral geniculate nucleus (dLGN) receive inputs from retinal ganglion cells via retinogeniculate synapses. These connections undergo pruning in the first two weeks after eye opening. The remaining connections are strengthened several-fold by the insertion of AMPA receptors (AMPARs) into weak or silent synapses. In this study, we found that the AMPAR auxiliary subunit CKAMP44 is required for receptor insertion and function of retinogeniculate synapses during development. Genetic deletion of CKAMP44 resulted in decreased synaptic strength and a higher number of silent synapses in young (P9-11) mice. Recovery from desensitisation of AMPA receptors was faster in CKAMP44 knockout (CKAMP44-/- ) than in wildtype mice. Moreover, loss of CKAMP44 increased the probability to induce plateau potentials, which are known to be important for eye-specific input segregation and retinogeniculate synapse maturation. The anatomy of relay neurons in the dLGN was changed in young CKAMP44-/- mice showing a transient increase in dendritic branching that normalised during later development (P26-33). Interestingly, input segregation in young CKAMP44-/- mice was not affected when compared to wildtype mice. These results demonstrate that CKAMP44 promotes maturation and modulates function of retinogeniculate synapses during early development of the visual system without affecting input segregation. Abstract figure legend AMPA receptor auxiliary subunit CKAMP44 influences synaptic function in retinogeniculate synapses of young mice. CKAMP44 unsilences synapses by recruiting AMPA receptors to the synapse. Furthermore, genetic deletion of CKAMP44 reduces short-term depression and increases the probability to elicit L-type Ca2+ channel-mediated plateau potentials. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Florian Hetsch
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Danni Wang
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Xufeng Chen
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Jiong Zhang
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Muhammad Aslam
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Marcel Kegel
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
| | - Henrik Tonner
- Experimental Ophthalmology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstraße 1, 55131, Mainz, Germany
| | - Franz Grus
- Experimental Ophthalmology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstraße 1, 55131, Mainz, Germany
| | - Jakob von Engelhardt
- Institute of Pathophysiology, Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany
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Jung S, Zimin PI, Woods CB, Kayser EB, Haddad D, Reczek CR, Nakamura K, Ramirez JM, Sedensky MM, Morgan PG. Isoflurane inhibition of endocytosis is an anesthetic mechanism of action. Curr Biol 2022; 32:3016-3032.e3. [PMID: 35688155 PMCID: PMC9329204 DOI: 10.1016/j.cub.2022.05.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 03/30/2022] [Accepted: 05/13/2022] [Indexed: 10/18/2022]
Abstract
The mechanisms of volatile anesthetic action remain among the most perplexing mysteries of medicine. Across phylogeny, volatile anesthetics selectively inhibit mitochondrial complex I, and they also depress presynaptic excitatory signaling. To explore how these effects are linked, we studied isoflurane effects on presynaptic vesicle cycling and ATP levels in hippocampal cultured neurons from wild-type and complex I mutant (Ndufs4(KO)) mice. To bypass complex I, we measured isoflurane effects on anesthetic sensitivity in mice expressing NADH dehydrogenase (NDi1). Endocytosis in physiologic concentrations of glucose was delayed by effective behavioral concentrations of isoflurane in both wild-type (τ [unexposed] 44.8 ± 24.2 s; τ [exposed] 116.1 ± 28.1 s; p < 0.01) and Ndufs4(KO) cultures (τ [unexposed] 67.6 ± 16.0 s; τ [exposed] 128.4 ± 42.9 s; p = 0.028). Increasing glucose, to enhance glycolysis and increase ATP production, led to maintenance of both ATP levels and endocytosis (τ [unexposed] 28.0 ± 14.4; τ [exposed] 38.2 ± 5.7; reducing glucose worsened ATP levels and depressed endocytosis (τ [unexposed] 85.4 ± 69.3; τ [exposed] > 1,000; p < 0.001). The block in recycling occurred at the level of reuptake of synaptic vesicles into the presynaptic cell. Expression of NDi1 in wild-type mice caused behavioral resistance to isoflurane for tail clamp response (EC50 Ndi1(-) 1.27% ± 0.14%; Ndi1(+) 1.55% ± 0.13%) and halothane (EC50 Ndi1(-) 1.20% ± 0.11%; Ndi1(+) 1.46% ± 0.10%); expression of NDi1 in neurons improved hippocampal function, alleviated inhibition of presynaptic recycling, and increased ATP levels during isoflurane exposure. The clear alignment of cell culture data to in vivo phenotypes of both isoflurane-sensitive and -resistant mice indicates that inhibition of mitochondrial complex I is a primary mechanism of action of volatile anesthetics.
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Affiliation(s)
- Sangwook Jung
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Pavel I Zimin
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98195, USA
| | - Christian B Woods
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Ernst-Bernhard Kayser
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Dominik Haddad
- Gladstone Institute of Neurological Disease, San Francisco, CA 94158, USA
| | - Colleen R Reczek
- Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Ken Nakamura
- Gladstone Institute of Neurological Disease, San Francisco, CA 94158, USA; Department of Neurology, University of California, San Francisco, CA 94158, USA
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Neurological Surgery, University of Washington, Seattle, WA 98105, USA
| | - Margaret M Sedensky
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98195, USA
| | - Philip G Morgan
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98195, USA.
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Chater TE, Goda Y. The Shaping of AMPA Receptor Surface Distribution by Neuronal Activity. Front Synaptic Neurosci 2022; 14:833782. [PMID: 35387308 PMCID: PMC8979068 DOI: 10.3389/fnsyn.2022.833782] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 02/25/2022] [Indexed: 12/29/2022] Open
Abstract
Neurotransmission is critically dependent on the number, position, and composition of receptor proteins on the postsynaptic neuron. Of these, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are responsible for the majority of postsynaptic depolarization at excitatory mammalian synapses following glutamate release. AMPARs are continually trafficked to and from the cell surface, and once at the surface, AMPARs laterally diffuse in and out of synaptic domains. Moreover, the subcellular distribution of AMPARs is shaped by patterns of activity, as classically demonstrated by the synaptic insertion or removal of AMPARs following the induction of long-term potentiation (LTP) and long-term depression (LTD), respectively. Crucially, there are many subtleties in the regulation of AMPARs, and exactly how local and global synaptic activity drives the trafficking and retention of synaptic AMPARs of different subtypes continues to attract attention. Here we will review how activity can have differential effects on AMPAR distribution and trafficking along with its subunit composition and phosphorylation state, and we highlight some of the controversies and remaining questions. As the AMPAR field is extensive, to say the least, this review will focus primarily on cellular and molecular studies in the hippocampus. We apologise to authors whose work could not be cited directly owing to space limitations.
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