Calbindin regulates Kv4.1 trafficking and excitability in dentate granule cells via CaMKII-dependent phosphorylation

Calbindin, a major Ca2+ buffer in dentate granule cells (GCs), plays a critical role in shaping Ca2+ signals, yet how it regulates neuronal functions remains largely unknown. Here, we found that calbindin knock-out mice (CBKO) exhibited hyperexcitability in dentate GCs and impaired pattern separation, which was concurrent with reduced K+ current due to downregulated surface expression of Kv4.1. Consistently, manipulation of the calbindin expression in HT22 led to changes in CaMKII activation and the level of surface localization of Kv4.1 through phosphorylation at serine 555, confirming the mechanism underlying neuronal hyperexcitability in CBKO. We also discovered that Ca2+ buffering capacity was significantly reduced in the GCs of Tg2576 to the level of CBKO GCs, and this reduction was restored to normal levels by antioxidants, suggesting that calbindin is a target of oxidative stress. Our data suggest that regulation of CaMKII signaling by Ca2+ buffer is crucial for neuronal excitability regulation.

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PKA-RIIβ autophosphorylation modulates PKA activity and seizure phenotypes in mice

Communications Biology ◽

10.1038/s42003-021-01748-4 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Jingliang Zhang ◽

Chenyu Zhang ◽

Xiaoling Chen ◽

Bingwei Wang ◽

Weining Ma ◽

...

Keyword(s):

Therapeutic Target ◽

Neurological Disorders ◽

Neuronal Excitability ◽

Granule Cells ◽

Critical Role ◽

Intrinsic Excitability ◽

Seizure Susceptibility ◽

Seizure Onset ◽

Potential Therapeutic Target ◽

Seizure Model

AbstractTemporal lobe epilepsy (TLE) is one of the most common and intractable neurological disorders in adults. Dysfunctional PKA signaling is causally linked to the TLE. However, the mechanism underlying PKA involves in epileptogenesis is still poorly understood. In the present study, we found the autophosphorylation level at serine 114 site (serine 112 site in mice) of PKA-RIIβ subunit was robustly decreased in the epileptic foci obtained from both surgical specimens of TLE patients and seizure model mice. The p-RIIβ level was negatively correlated with the activities of PKA. Notably, by using a P-site mutant that cannot be autophosphorylated and thus results in the released catalytic subunit to exert persistent phosphorylation, an increase in PKA activities through transduction with AAV-RIIβ-S112A in hippocampal DG granule cells decreased mIPSC frequency but not mEPSC, enhanced neuronal intrinsic excitability and seizure susceptibility. In contrast, a reduction of PKA activities by RIIβ knockout led to an increased mIPSC frequency, a reduction in neuronal excitability, and mice less prone to experimental seizure onset. Collectively, our data demonstrated that the autophosphorylation of RIIβ subunit plays a critical role in controlling neuronal and network excitabilities by regulating the activities of PKA, providing a potential therapeutic target for TLE.

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Methylation determines the extracellular calcium sensitivity of the leak channel NALCN in hippocampal dentate granule cells

Experimental & Molecular Medicine ◽

10.1038/s12276-019-0325-0 ◽

2019 ◽

Vol 51 (10) ◽

pp. 1-14 ◽

Cited By ~ 1

Author(s):

Seul-Yi Lee ◽

Tuan Anh Vuong ◽

Xianlan Wen ◽

Hyeon-Ju Jeong ◽

Hyun-Kyung So ◽

...

Keyword(s):

Neuronal Excitability ◽

Granule Cells ◽

Phosphorylation Site ◽

Calcium Sensitivity ◽

Arginine Methylation ◽

Resting Membrane Potential ◽

Leak Channel ◽

Dentate Granule Cells ◽

Severe Intellectual Disability

Abstract The sodium leak channel NALCN is a key player in establishing the resting membrane potential (RMP) in neurons and transduces changes in extracellular Ca2+ concentration ([Ca2+]e) into increased neuronal excitability as the downstream effector of calcium-sensing receptor (CaSR). Gain-of-function mutations in the human NALCN gene cause encephalopathy and severe intellectual disability. Thus, understanding the regulatory mechanisms of NALCN is important for both basic and translational research. This study reveals a novel mechanism for NALCN regulation by arginine methylation. Hippocampal dentate granule cells in protein arginine methyltransferase 7 (PRMT7)-deficient mice display a depolarization of the RMP, decreased threshold currents, and increased excitability compared to wild-type neurons. Electrophysiological studies combined with molecular analysis indicate that enhanced NALCN activities contribute to hyperexcitability in PRMT7−/− neurons. PRMT7 depletion in HEK293T cells increases NALCN activity by shifting the dose-response curve of NALCN inhibition by [Ca2+]e without affecting NALCN protein levels. In vitro methylation studies show that PRMT7 methylates a highly conserved Arg1653 of the NALCN gene located in the carboxy-terminal region that is implicated in CaSR-mediated regulation. A kinase-specific phosphorylation site prediction program shows that the adjacent Ser1652 is a potential phosphorylation site. Consistently, our data from site-specific mutants and PKC inhibitors suggest that Arg1653 methylation might modulate Ser1652 phosphorylation mediated by CaSR/PKC-delta, leading to [Ca2+]e-mediated NALCN suppression. Collectively, these data suggest that PRMT7 deficiency decreases NALCN methylation at Arg1653, which, in turn, decreases CaSR/PKC-mediated Ser1652 phosphorylation, lifting NALCN inhibition, thereby enhancing neuronal excitability. Thus, PRMT7-mediated NALCN inhibition provides a potential target for the development of therapeutic tools for neurological diseases.

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Transient Neurophysiological Changes in CA3 Neurons and Dentate Granule Cells After Severe Forebrain Ischemia In Vivo

Journal of Neurophysiology ◽

10.1152/jn.1998.80.6.2860 ◽

1998 ◽

Vol 80 (6) ◽

pp. 2860-2869 ◽

Cited By ~ 20

Author(s):

T. M. Gao ◽

E. M. Howard ◽

Z. C. Xu

Keyword(s):

Synaptic Transmission ◽

Neuronal Excitability ◽

Granule Cells ◽

Input Resistance ◽

Cell Types ◽

Forebrain Ischemia ◽

Postsynaptic Potentials ◽

Dentate Granule Cells ◽

Ca3 Neurons

Gao, T. M., E. M. Howard, and Z. C. Xu. Transient neurophysiological changes in CA3 neurons and dentate granule cells after severe forebrain ischemia in vivo. J. Neurophysiol. 80: 2860–2869, 1998. The spontaneous activities, evoked synaptic responses, and membrane properties of CA3 pyramidal neurons and dentate granule cells in rat hippocampus were compared before ischemia and ≤7 days after reperfusion with intracellular recording and staining techniques in vivo. A four-vessel occlusion method was used to induce ∼14 min of ischemic depolarization. No significant change in spontaneous firing rate was observed in both cell types after reperfusion. The amplitude and slope of excitatory postsynaptic potentials (EPSPs) in CA3 neurons decreased to 50% of control values during the first 12 h reperfusion and returned to preischemic levels 24 h after reperfusion. The amplitude and slope of EPSPs in granule cells slightly decreased 24–36 h after reperfusion. The amplitude of inhibitory postsynaptic potentials in CA3 neurons transiently increased 24 h after reperfusion, whereas that in granule cells showed a transient decrease 24–36 h after reperfusion. The duration of spike width of CA3 and granule cells became longer than that of control values during the first 12 h reperfusion. The spike threshold of both cell types significantly increased 24–36 h after reperfusion, whereas the frequency of repetitive firing evoked by depolarizing current pulse was decreased during this period. No significant change in rheobase and input resistance was observed in CA3 neurons. A transient increase in rheobase and a transient decrease in input resistance were detected in granule cells 24–36 h after reperfusion. The amplitude of fast afterhyperpolarization in both cell types increased for 2 days after ischemia and returned to normal values 7 days after reperfusion. The results from this study indicate that the neuronal excitability and synaptic transmission in CA3 and granule cells are transiently suppressed after severe forebrain ischemia. The depression of synaptic transmission and neuronal excitability may provide protection for neurons after ischemic insult.

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Decreased surface expression of the δ subunit of the GABA A receptor contributes to reduced tonic inhibition in dentate granule cells in a mouse model of fragile X syndrome

Experimental Neurology ◽

10.1016/j.expneurol.2017.08.008 ◽

2017 ◽

Vol 297 ◽

pp. 168-178 ◽

Cited By ~ 12

Author(s):

Nianhui Zhang ◽

Zechun Peng ◽

Xiaoping Tong ◽

A. Kerstin Lindemeyer ◽

Yliana Cetina ◽

...

Keyword(s):

Mouse Model ◽

Fragile X Syndrome ◽

Granule Cells ◽

Fragile X ◽

Surface Expression ◽

Tonic Inhibition ◽

Gaba A ◽

Dentate Granule Cells

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Impaired pattern separation in Tg2576 mice is associated with hyperexcitable dentate gyrus caused by Kv4.1 downregulation

Molecular Brain ◽

10.1186/s13041-021-00774-x ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Kyung-Ran Kim ◽

Yoonsub Kim ◽

Hyeon-Ju Jeong ◽

Jong-Sun Kang ◽

Sang Hun Lee ◽

...

Keyword(s):

Dentate Gyrus ◽

Granule Cells ◽

Neurodegenerative Disorder ◽

Critical Role ◽

Memory Loss ◽

Pattern Separation ◽

Antioxidant Treatment ◽

Action Potential Firing ◽

Functional Changes ◽

Tg2576 Mice

AbstractAlzheimer’s disease (AD) is a progressive neurodegenerative disorder that causes memory loss. Most AD researches have focused on neurodegeneration mechanisms. Considering that neurodegenerative changes are not reversible, understanding early functional changes before neurodegeneration is critical to develop new strategies for early detection and treatment of AD. We found that Tg2576 mice exhibited impaired pattern separation at the early preclinical stage. Based on previous studies suggesting a critical role of dentate gyrus (DG) in pattern separation, we investigated functional changes in DG of Tg2576 mice. We found that granule cells in DG (DG-GCs) in Tg2576 mice showed increased action potential firing in response to long depolarizations and reduced 4-AP sensitive K+-currents compared to DG-GCs in wild-type (WT) mice. Among Kv4 family channels, Kv4.1 mRNA expression in DG was significantly lower in Tg2576 mice. We confirmed that Kv4.1 protein expression was reduced in Tg2576, and this reduction was restored by antioxidant treatment. Hyperexcitable DG and impaired pattern separation in Tg2576 mice were also recovered by antioxidant treatment. These results highlight the hyperexcitability of DG-GCs as a pathophysiologic mechanism underlying early cognitive deficits in AD and Kv4.1 as a new target for AD pathogenesis in relation to increased oxidative stress.

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Impaired pattern separation in Tg2576 mice is associated with hyperexcitable dentate gyrus caused by Kv4.1 downregulation

10.1101/2021.02.17.431569 ◽

2021 ◽

Author(s):

Kyung-Ran Kim ◽

Yoonsub Kim ◽

Hyeon-Ju Jeong ◽

Jong-Sun Kang ◽

Sang Hun Lee ◽

...

Keyword(s):

Dentate Gyrus ◽

Granule Cells ◽

Neurodegenerative Disorder ◽

Critical Role ◽

Memory Loss ◽

Pattern Separation ◽

Antioxidant Treatment ◽

Action Potential Firing ◽

Functional Changes ◽

Tg2576 Mice

AbstractAlzheimer’s disease (AD) is a progressive neurodegenerative disorder that causes memory loss. Most AD researches have focused on neurodegeneration mechanisms. Considering that neurodegenerative changes are not reversible, understanding early functional changes before neurodegeneration is critical to develop new strategies for early detection and treatment of AD. We found that Tg2576 mice exhibited impaired pattern separation at the early preclinical stage. Based on previous studies suggesting a critical role of dentate gyrus (DG) in pattern separation, we investigated functional changes in DG of Tg2576 mice. We found that granule cells in DG (DG-GCs) in Tg2576 mice showed increased action potential firing in response to long depolarizations and reduced 4-AP sensitive K+-currents compared to DG-GCs in wild-type (WT) mice. Among Kv4 family channels, Kv4.1 mRNA expression in DG was significantly lower in Tg2576 mice. We confirmed that Kv4.1 protein expression was reduced in Tg2576, and this reduction was restored by antioxidant treatment. Hyperexcitable DG and impaired pattern separation in Tg2576 mice were also recovered by antioxidant treatment. These results highlight the hyperexcitability of DG-GCs as a pathophysiologic mechanism underlying early cognitive deficits in AD and Kv4.1 as a new target for AD pathogenesis in relation to increased oxidative stress.

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Preferential targeting of lateral entorhinal inputs onto newly integrated granule cells

10.1101/153767 ◽

2017 ◽

Author(s):

Nicholas I. Woods ◽

Christopher E. Vaaga ◽

Christina Chatzi ◽

Jaimie D. Adelson ◽

Matthew F. Collie ◽

...

Keyword(s):

Entorhinal Cortex ◽

Spatial Information ◽

Granule Cells ◽

Molecular Layer ◽

Critical Role ◽

Perforant Path ◽

Spine Density ◽

Unique Role ◽

Dentate Granule Cells ◽

Episodic Memories

AbstractMature dentate granule cells in the hippocampus receive input from the entorhinal cortex via the perforant path in precisely arranged lamina, with medial entorhinal axons innervating the middle molecular layer and lateral entorhinal cortex axons innervating the outer molecular layer. Although vastly outnumbered by mature granule cells, adult-generated newborn granule cells play a unique role in hippocampal function, which has largely been attributed to their enhanced excitability and plasticity (Schmidt-Hieber et al., 2004; Ge et al., 2007). Inputs from the medial and lateral entorhinal cortex carry different informational content, thus the distribution of inputs onto newly integrated granules will affect their function in the circuit. Therefore we examined the functional innervation and synaptic maturation of newly-generated dentate granule cells using retroviral labeling in combination with selective optogenetic activation of medial or lateral entorhinal inputs. Our results indicate that lateral entorhinal inputs provide nearly all the functional innervation of newly integrated granule cells. Despite preferential functional targeting, the dendritic spine density of immature granule cells was not increased in the outer molecular layer compared to the middle molecular layer. However, chronic blockade of neurotransmitter release in medial entorhinal axons with tetanus toxin disrupted normal synapse development from both medial and lateral entorhinal inputs. Our results support a role for preferential lateral perforant path input onto newly generated neurons in mediating pattern separation, but also indicates that medial perforant path input is necessary for normal synaptic development.Significance StatementThe formation of episodic memories involves the integration of contextual and spatial information. Newly integrated neurons in the dentate gyrus of the hippocampus play a critical role in this process, despite constituting only a minor fraction of total granule cells. Here we demonstrate that these neurons preferentially receive information thought to convey the context of an experience - a unique role that each newly integrated granule cell serves for about a month before reaching maturity.

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