Gjd2b-mediated gap junctions promote glutamatergic synapse formation and dendritic elaboration in Purkinje neurons

Gap junctions between neurons serve as electrical synapses, in addition to conducting metabolites and signaling molecules. During development, early-appearing gap junctions are thought to prefigure chemical synapses, which appear much later. We present evidence for this idea at a central, glutamatergic synapse and provide some mechanistic insights. Loss or reduction in the levels of the gap junction protein Gjd2b decreased the frequency of glutamatergic miniature excitatory postsynaptic currents (mEPSCs) in cerebellar Purkinje neurons (PNs) in larval zebrafish. Ultrastructural analysis in the molecular layer showed decreased synapse density. Further, mEPSCs had faster kinetics and larger amplitudes in mutant PNs, consistent with their stunted dendritic arbors. Time-lapse microscopy in wild type and mutant PNs reveals that Gjd2b puncta promote the elongation of branches and that CaMKII may be a critical mediator of this process. These results demonstrate that Gjd2b-mediated gap junctions regulate glutamatergic synapse formation and dendritic elaboration in PNs.

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Gjd2b-mediated gap junctions promote glutamatergic synapse formation and dendritic elaboration in Purkinje neurons

10.1101/2020.01.31.928242 ◽

2020 ◽

Author(s):

Sahana Sitaraman ◽

Gnaneshwar Yadav ◽

Shaista Jabeen ◽

Vandana Agarwal ◽

Vatsala Thirumalai

Keyword(s):

Gap Junctions ◽

Dendritic Growth ◽

Synapse Formation ◽

Purkinje Neurons ◽

Dendritic Arbor ◽

Glutamatergic Synapse ◽

Wild Type ◽

Synapse Density ◽

Chemical Synapses ◽

Cerebellar Purkinje Neurons

AbstractGap junctions between neurons serve as electrical synapses, in addition to conducting metabolites and signaling molecules. These functions of gap junctions have led to the idea that during development, gap junctions could prefigure chemical synapses. We present evidence for this idea at a central, glutamatergic synapse and provide some mechanistic insights. Here, we show that reduction or loss of Gjd2b-containing gap junctions led to a decrease in glutamatergic synapse density in cerebellar Purkinje neurons (PNs) in larval zebrafish. Gjd2b-/- larvae exhibited faster mEPSCs and a consistent decrease in dendritic arbor size. These PNs also showed decreased branch elongations but normal rate of branch retractions. Further, the dendritic growth deficits in gjd2b-/- mutants were rescued by expressing full length Gjd2b in single PNs. This suggests that Gjd2b may form heterotypic channels with other connexins in gjd2b-/- larvae, though it is not clear if PNs in wild type animals make homotypic or heterotypic gap junction channels. Dendritic growth deficits were not rescued by expressing a deletion mutant of Gjd2b unable to form functional channels. Finally, the expression levels of five isoforms of camkii were increased in gjd2b-/- larvae and inhibition of CaMKII restored dendritic arbor lengths of mutant larvae to wild type levels. These results suggest a link between signaling via Gjd2b-containing gap junctions, CaMKII function and dendritic growth. In sum, our results demonstrate that Gjd2b-mediated gap junctions are key regulators of glutamatergic synapse formation and dendritic elaboration in PNs.

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BDNF mobilizes synaptic vesicles and enhances synapse formation by disrupting cadherin–β-catenin interactions

The Journal of Cell Biology ◽

10.1083/jcb.200601087 ◽

2006 ◽

Vol 174 (2) ◽

pp. 289-299 ◽

Cited By ~ 115

Author(s):

Shernaz X. Bamji ◽

Beatriz Rico ◽

Nikole Kimes ◽

Louis F. Reichardt

Keyword(s):

Synaptic Vesicle ◽

Synaptic Vesicles ◽

Hippocampal Neurons ◽

Molecular Mechanisms ◽

Synapse Formation ◽

Time Lapse ◽

Synapse Density ◽

Vesicle Mobility ◽

Small Clusters ◽

Vertebrate Central Nervous System

Neurons of the vertebrate central nervous system have the capacity to modify synapse number, morphology, and efficacy in response to activity. Some of these functions can be attributed to activity-induced synthesis and secretion of the neurotrophin brain-derived neurotrophic factor (BDNF); however, the molecular mechanisms by which BDNF mediates these events are still not well understood. Using time-lapse confocal analysis, we show that BDNF mobilizes synaptic vesicles at existing synapses, resulting in small clusters of synaptic vesicles “splitting” away from synaptic sites. We demonstrate that BDNF's ability to mobilize synaptic vesicle clusters depends on the dissociation of cadherin–β-catenin adhesion complexes that occurs after tyrosine phosphorylation of β-catenin. Artificially maintaining cadherin–β-catenin complexes in the presence of BDNF abolishes the BDNF-mediated enhancement of synaptic vesicle mobility, as well as the longer-term BDNF-mediated increase in synapse number. Together, this data demonstrates that the disruption of cadherin–β-catenin complexes is an important molecular event through which BDNF increases synapse density in cultured hippocampal neurons.

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Asymmetry of an intracellular scaffold at vertebrate electrical synapses

10.1101/173955 ◽

2017 ◽

Author(s):

Audrey J Marsh ◽

Jennifer Carlisle Michel ◽

Anisha P Adke ◽

Emily L Heckman ◽

Adam C Miller

Keyword(s):

Gap Junction ◽

Synapse Formation ◽

Neural Circuit ◽

Electrical Synapse ◽

Electrical Synapses ◽

Gap Junction Channels ◽

Junction Protein ◽

Chemical Synapses ◽

And Function

AbstractNeuronal synaptic connections are electrical or chemical and together are essential to dynamically defining neural circuit function. While chemical synapses are well known for their biochemical complexity, electrical synapses are often viewed as comprised solely of neuronal gap junction channels that allow direct ionic and metabolic communication. However, associated with the gap junction channels are structures observed by electron microscopy called the Electrical Synapse Density (ESD). The ESD has been suggested to be critical for the formation and function of the electrical synapse, yet the biochemical makeup of these structures is poorly understood. Here we find that electrical synapse formation in vivo requires an intracellular scaffold called Tight Junction Protein 1b (Tjp1b). Tjp1b is localized to electrical synapses where it is required for the stabilization of the gap junction channels and for electrical synapse function. Strikingly, we find that Tjp1b protein localizes and functions asymmetrically, exclusively on the postsynaptic side of the synapse. Our findings support a novel model in which there is molecular asymmetry at the level of the intracellular scaffold that is required for building the electrical synapse. ESD molecular asymmetries may be a fundamental motif of all nervous systems and could support functional asymmetry at the electrical synapse.

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Neuroprotective Metabolites of Hericium erinaceus Promote Neuro-Healthy Aging

International Journal of Molecular Sciences ◽

10.3390/ijms22126379 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6379

Author(s):

Elisa Roda ◽

Erica Cecilia Priori ◽

Daniela Ratto ◽

Fabrizio De Luca ◽

Carmine Di Iorio ◽

...

Keyword(s):

Oxidative Stress ◽

Healthy Aging ◽

Molecular Layer ◽

Dietary Supplementation ◽

Purkinje Neurons ◽

Geriatric Syndrome ◽

Oral Supplementation ◽

Erinacine A ◽

And Oxidative Stress

Frailty is a geriatric syndrome associated with both locomotor and cognitive decline, typically linked to chronic systemic inflammation, i.e., inflammaging. In the current study, we investigated the effect of a two-month oral supplementation with standardized extracts of H. erinaceus, containing a known amount of Erinacine A, Hericenone C, Hericenone D, and L-ergothioneine, on locomotor frailty and cerebellum of aged mice. Locomotor performances were monitored comparing healthy aging and frail mice. Cerebellar volume and cytoarchitecture, together with inflammatory and oxidative stress pathways, were assessed focusing on senescent frail animals. H. erinaceus partially recovered the aged-related decline of locomotor performances. Histopathological analyses paralleled by immunocytochemical evaluation of specific molecules strengthened the neuroprotective role of H. erinaceus able to ameliorate cerebellar alterations, i.e., milder volume reduction, slighter molecular layer thickness decrease and minor percentage of shrunken Purkinje neurons, also diminishing inflammation and oxidative stress in frail mice while increasing a key longevity regulator and a neuroprotective molecule. Thus, our present findings demonstrated the efficacy of a non-pharmacological approach, based on the dietary supplementation using H. erinaceus extract, which represent a promising adjuvant therapy to be associated with conventional geriatric treatments.

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Correction: Stimulus Discrimination in Cerebellar Purkinje Neurons

PLoS ONE ◽

10.1371/journal.pone.0101376 ◽

2014 ◽

Vol 9 (6) ◽

pp. e101376

Author(s):

Keyword(s):

Purkinje Neurons ◽

Stimulus Discrimination ◽

Cerebellar Purkinje Neurons

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Continuous network of endoplasmic reticulum in cerebellar Purkinje neurons.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.91.16.7510 ◽

1994 ◽

Vol 91 (16) ◽

pp. 7510-7514 ◽

Cited By ~ 113

Author(s):

M. Terasaki ◽

N. T. Slater ◽

A. Fein ◽

A. Schmidek ◽

T. S. Reese

Keyword(s):

Endoplasmic Reticulum ◽

Purkinje Neurons ◽

Cerebellar Purkinje Neurons

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Low pH enhances connexin32 degradation in the pancreatic acinar cell

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00010.2014 ◽

2014 ◽

Vol 307 (1) ◽

pp. G24-G32 ◽

Cited By ~ 7

Author(s):

Anamika M. Reed ◽

Thomas Kolodecik ◽

Sohail Z. Husain ◽

Fred S. Gorelick

Keyword(s):

Gap Junctions ◽

Acinar Cell ◽

Intercellular Communication ◽

Pancreatic Acinar Cell ◽

Low Ph ◽

Extracellular Ph ◽

Gap Junctional Intercellular Communication ◽

Junction Protein ◽

Clinical Conditions ◽

Gap Junctional

Decreased extracellular pH is observed in a number of clinical conditions and can sensitize to the development and worsen the severity of acute pancreatitis. Because intercellular communication through gap junctions is pH-sensitive and modulates pancreatitis responses, we evaluated the effects of low pH on gap junctions in the rat pancreatic acinar cell. Decreasing extracellular pH from 7.4 to 7.0 significantly inhibited gap junctional intracellular communication. Acidic pH also significantly reduced levels of connexin32, the predominant gap junction protein in acinar cells, and altered its localization. Increased degradation through the proteasomal, lysosomal, and autophagic pathways mediated the decrease in connexin32 under low-pH conditions. These findings provide the first evidence that low extracellular pH can regulate gap junctional intercellular communication by enhancing connexin degradation.

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