Neuronal CA2+/calmodulin-dependent protein kinase II: the role of structure and autoregulation in cellular function

Calmodulin as Ca2+-Dependent Interactor of FTO Dioxygenase

FTO is an N⁶-methyladenosine demethylase removing methyl groups from nucleic acids. Several studies indicate the creation of FTO complexes with other proteins. Here, we looked for regulatory proteins recognizing parts of the FTO dioxygenase region. In the Calmodulin (CaM) Target Database, we found the FTO C-domain potentially binding CaM, and we proved this finding experimentally. The interaction was Ca²⁺-dependent but independent on FTO phosphorylation. We found that FTO–CaM interaction essentially influences calcium-binding loops in CaM, indicating the presence of two peptide populations—exchanging as CaM alone and differently, suggesting that only one part of CaM interacts with FTO, and the other one reminds free. The modeling of FTO–CaM interaction showed its stable structure when the half of the CaM molecule saturated with Ca²⁺ interacts with the FTO C-domain, whereas the other part is disconnected. The presented data indicate calmodulin as a new FTO interactor and support engagement of the FTO protein in calcium signaling pathways.

Tilianin Ameliorates Cognitive Dysfunction and Neuronal Damage in Rats with Vascular Dementia via p-CaMKII/ERK/CREB and ox-CaMKII-Dependent MAPK/NF-κB Pathways

Vascular dementia (VaD) is a common cause of cognitive decline and dementia of vascular origin, but the precise pathological mechanisms are unknown, and so effective clinical treatments have not been established. Tilianin, the principal active compound of total flavonoid extract from Dracocephalum moldavica L., is a candidate therapy for cardio-cerebrovascular diseases in China. However, its potential in the treatment of VaD is unclear. The present study is aimed at investigating the protective effects of tilianin on VaD and exploring the underlying mechanism of the action. A model of VaD was established by permanent 2-vessel occlusion (2VO) in rats. Human neurons (hNCs) differentiated from human-induced pluripotent stem cells were used to establish an oxygen-glucose deprivation (OGD) model. The therapeutic effects and potential mechanisms of tilianin were identified using behavioral tests, histochemistry, and multiple molecular biology techniques such as Western blot analysis and gene silencing. The results demonstrated that tilianin modified spatial cognitive impairment, neurodegeneration, oxidation, and apoptosis in rats with VaD and protected hNCs against OGD by increasing cell viability and decreasing apoptosis rates. A study of the mechanism indicated that tilianin restored p-CaMKII/ERK1/2/CREB signaling in the hippocampus, maintaining hippocampus-independent memory. In addition, tilianin inhibited an ox-CaMKII/p38 MAPK/JNK/NF-κB associated inflammatory response caused by cerebral oxidative stress imbalance in rats with VaD. Furthermore, specific CaMKIIα siRNA action revealed that tilianin-exerted neuroprotection involved increase of neuronal viability, inhibition of apoptosis, and suppression of inflammation, which was dependent on CaMKIIα. In conclusion, the results suggested the neuroprotective effect of tilianin in VaD and the potential mechanism associated with dysfunction in the regulation of p-CaMKII-mediated long-term memory and oxidation and inflammation involved with ox-CaMKII, which may lay the foundation for clinical trials of tilianin for the treatment of VaD in the future.

Calcium Signaling Mechanisms Across Kingdoms

Calcium (Ca²⁺) is a unique mineral that serves as both a nutrient and a signal in all eukaryotes. To maintain Ca²⁺ homeostasis for both nutrition and signaling purposes, the toolkit for Ca²⁺ transport has expanded across kingdoms of eukaryotes to encode specific Ca²⁺ signals referred to as Ca²⁺ signatures. In parallel, a large array of Ca²⁺-binding proteins has evolved as specific sensors to decode Ca²⁺ signatures. By comparing these coding and decoding mechanisms in fungi, animals, and plants, both unified and divergent themes have emerged, and the underlying complexity will challenge researchers for years to come. Considering the scale and breadth of the subject, instead of a literature survey, in this review we focus on a conceptual framework that aims to introduce to readers to the principles and mechanisms of Ca²⁺ signaling. We finish with several examples of Ca²⁺-signaling pathways, including polarized cell growth, immunity and symbiosis, and systemic signaling, to piece together specific coding and decoding mechanisms in plants versus animals. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Preservation of vision after CaMKII-mediated protection of retinal ganglion cells

Retinal ganglion cells (RGCs) are the sole output neurons that transmit visual information from the retina to the brain. Diverse insults and pathological states cause degeneration of RGC somas and axons leading to irreversible vision loss. A fundamental question is whether manipulation of a key regulator of RGC survival can protect RGCs from diverse insults and pathological states, and ultimately preserve vision. Here, we report that CaMKII-CREB signaling is compromised after excitotoxic injury to RGC somas or optic nerve injury to RGC axons, and reactivation of this pathway robustly protects RGCs from both injuries. CaMKII activity also promotes RGC survival in the normal retina. Further, reactivation of CaMKII protects RGCs in two glaucoma models where RGCs degenerate from elevated intraocular pressure or genetic deficiency. Last, CaMKII reactivation protects long-distance RGC axon projections in vivo and preserves visual function, from the retina to the visual cortex, and visually guided behavior.

Rosmarinic Acid, a Bioactive Phenolic Compound, Inhibits Glutamate Release from Rat Cerebrocortical Synaptosomes through GABAA Receptor Activation

Rosmarinic acid, a major component of rosemary, is a polyphenolic compound with potential neuroprotective effects. Asreducing the synaptic release of glutamate is crucial to achieving neuroprotectant's pharmacotherapeutic effects, the effect of rosmarinic acid on glutamate release was investigated in rat cerebrocortical nerve terminals (synaptosomes). Rosmarinic acid depressed the 4-aminopyridine (4-AP)-induced glutamate release in a concentration-dependent manner. The removal of extracellular calcium and the blockade of vesicular transporters prevented the inhibition of glutamate release by rosmarinic acid. Rosmarinic acid reduced 4-AP-induced intrasynaptosomal Ca2+ elevation. The inhibition of N-, P/Q-type Ca2+ channels and the calcium/calmodulin-dependent kinase II (CaMKII) prevented rosmarinic acid from having effects on glutamate release. Rosmarinic acid also reduced the 4-AP-induced activation of CaMKII and the subsequent phosphorylation of synapsin I, the main presynaptic target of CaMKII. In addition, immunocytochemistry confirmed the presence of GABAA receptors. GABAA receptor agonist and antagonist blocked the inhibitory effect of rosmarinic acid on 4-AP-evoked glutamate release. Docking data also revealed that rosmarinic acid formed a hydrogen bond with the amino acid residues of GABAA receptor. These results suggested that rosmarinic acid activates GABAA receptors in cerebrocortical synaptosomes to decrease Ca2+ influx and CaMKII/synapsin I pathway to inhibit the evoked glutamate release.

The dysregulated expression and functional effect of CaMK2 in cancer

CaMK2 (calcium/calmodulin-dependent protein kinase 2), a multifunctional serine/threonine-protein kinase involved in diverse cellular processes, is vital for the transduction of the Ca²⁺ signaling cascade. Recently, research has highlighted the involvement of CaMK2 in cancer development. However, the specific effects of CaMK2 on cancer have not been fully elucidated. In this review, we summarize not only the altered expression of CaMK2 in a range of cancers, as evidenced by bioinformatics analysis, but also the significant role of CaMK2 in regulating cancer progression, such as proliferation and metastasis. In addition, we described the functional influence of CaMK2 on cancer stemness and resistance. Understanding the critical effects and mechanisms of CaMK2 in cancer would facilitate the development of a promising therapeutic strategy for cancer treatment.

The Relevance of Amyloid β-Calmodulin Complexation in Neurons and Brain Degeneration in Alzheimer's Disease

Intraneuronal amyloid β (Aβ) oligomer accumulation precedes the appearance of amyloid plaques or neurofibrillary tangles and is neurotoxic. In Alzheimer’s disease (AD)-affected brains, intraneuronal Aβ oligomers can derive from Aβ peptide production within the neuron and, also, from vicinal neurons or reactive glial cells. Calcium homeostasis dysregulation and neuronal excitability alterations are widely accepted to play a key role in Aβ neurotoxicity in AD. However, the identification of primary Aβ-target proteins, in which functional impairment initiating cytosolic calcium homeostasis dysregulation and the critical point of no return are still pending issues. The micromolar concentration of calmodulin (CaM) in neurons and its high affinity for neurotoxic Aβ peptides (dissociation constant ≈ 1 nM) highlight a novel function of CaM, i.e., the buffering of free Aβ concentrations in the low nanomolar range. In turn, the concentration of Aβ-CaM complexes within neurons will increase as a function of time after the induction of Aβ production, and free Aβ will rise sharply when accumulated Aβ exceeds all available CaM. Thus, Aβ-CaM complexation could also play a major role in neuronal calcium signaling mediated by calmodulin-binding proteins by Aβ; a point that has been overlooked until now. In this review, we address the implications of Aβ-CaM complexation in the formation of neurotoxic Aβ oligomers, in the alteration of intracellular calcium homeostasis induced by Aβ, and of dysregulation of the calcium-dependent neuronal activity and excitability induced by Aβ.

Characterization of two group III potato CDPKs, StCDPK22 and StCDPK24, that contain three EF-Hand motifs in their CLDs

Four members of the potato (Solanum tuberosum L.) calcium-dependent protein kinase (CDPK) family StCDPK22/23/24 and StCDPK27, present three functional EF-hands motifs in their calmodulin-like domain (CLD). StCDPK22/23/24 are clustered in clade III-b1 with tomato and Arabidopsis CDPKs that lack the first EF-hand motif, while StCDPK27 is clustered in clade III-b3 with CDPKs that lack EF-hand 2. Members of each clade share similar intron-exon structures and acylation profiles. 3D model predictions suggested that StCDPK22 and StCDPK24 are active kinases that undergo a conformational switch in the presence of Ca²⁺ even when lacking one functional EF-hand motif; however, assays performed with recombinant proteins indicated that StCDPK24:6xHis was active in all the conditions tested, and its activity was enhanced in the presence of Ca²⁺, but StCDPK22:6xHis had scarce or null activity. Both kinases share with AtCPK8 the same autophosphorylation pattern in the autoinhibitory (AD) and C-terminal variable (CTV) domains, suggesting that it could be a characteristic of clade III-b1. RT-qPCR analysis revealed that StCDPK22 is mainly expressed in early stages of tuberization, but not limited to, while StCDPK24 expression is more ubiquitous. In silico analysis predicted several abiotic stress-responsive elements in its promoters. Accordingly, StCDPK24 expression peaked at 10 h in in vitro plants exposed to salt shock and then declined. Moreover, a significant increase was observed at 2 h in stems of salt-treated greenhouse plants, suggesting that this CDPK could participate in the early events of the signaling cascade triggered in response to salt.

Interactive Roles of CaMKII/Ryanodine Receptor Signaling and Inflammation in Lung Diseases

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is a multifunctional protein kinase and has been recently recognized to play a vital role in pathological events in the pulmonary system. CaMKII has diverse downstream targets that promote vascular disease, asthma, and cancer, so improved understanding of CaMKII signaling has the potential to lead to new therapies for lung diseases. Multiple studies have demonstrated that CaMKII is involved in redox modulation of ryanodine receptors (RyRs). CaMKII can be directly activated by reactive oxygen species (ROS) which then regulates RyR activity, which is essential for Ca²⁺-dependent processes in lung diseases. Furthermore, both CaMKII and RyRs participate in the inflammation process. However, their role in the pulmonary physiology in response to ROS is still an ambiguous one. Because CaMKII and RyRs are important in pulmonary biology, cell survival, cell cycle control, and inflammation, it is possible that the relationship between ROS and CaMKII/RyRs signal complex will be necessary for understanding and treating lung diseases. Here, we review roles of CaMKII/RyRs in lung diseases to understand with how CaMKII/RyRs may act as a transduction signal to connect prooxidant conditions into specific downstream pathological effects that are relevant to rare and common forms of pulmonary disease.

Prox1 inhibits neurite outgrowth during central nervous system development

During central nervous system (CNS) development, proper and timely induction of neurite elongation is critical for generating functional, mature neurons, and neuronal networks. Despite the wealth of information on the action of extracellular cues, little is known about the intrinsic gene regulatory factors that control this developmental decision. Here, we report the identification of Prox1, a homeobox transcription factor, as a key player in inhibiting neurite elongation. Although Prox1 promotes acquisition of early neuronal identity and is expressed in nascent post-mitotic neurons, it is heavily down-regulated in the majority of terminally differentiated neurons, indicating a regulatory role in delaying neurite outgrowth in newly formed neurons. Consistently, we show that Prox1 is sufficient to inhibit neurite extension in mouse and human neuroblastoma cell lines. More importantly, Prox1 overexpression suppresses neurite elongation in primary neuronal cultures as well as in the developing mouse brain, while Prox1 knock-down promotes neurite outgrowth. Mechanistically, RNA-Seq analysis reveals that Prox1 affects critical pathways for neuronal maturation and neurite extension. Interestingly, Prox1 strongly inhibits many components of Ca2+ signaling pathway, an important mediator of neurite extension and neuronal maturation. In accordance, Prox1 represses Ca2+ entry upon KCl-mediated depolarization and reduces CREB phosphorylation. These observations suggest that Prox1 acts as a potent suppressor of neurite outgrowth by inhibiting Ca2+ signaling pathway. This action may provide the appropriate time window for nascent neurons to find the correct position in the CNS prior to initiation of neurites and axon elongation.

Role of calcium/calmodulin-dependent kinase 2 in neurodevelopmental disorders

Neurodevelopmental disorders are a complex and heterogeneous group of neurological disorders characterized by their early-onset and estimated to affect more than 3% of children worldwide. The rapid advancement of sequencing technologies in the past years allowed the identification of hundreds of variants in several different genes causing neurodevelopmental disorders. Between those, new variants in the Calcium/calmodulin dependent protein kinase II (CAMK2) genes were recently linked to intellectual disability. Despite many years of research on CAMK2, this proves for the first time that this well-known and highly conserved molecule plays an important role in the human brain. In this review, we give an overview of the identified CAMK2 variants, and we speculate on potential mechanisms through which dysfunctions in CAMK2 result in neurodevelopmental disorders. Additionally, we discuss how the identification of CAMK2 variants might result in new exciting discoveries regarding the function of CAMK2 in the human brain.

Gastrodin ameliorates learning and memory impairment in rats with vascular dementia by promoting autophagy flux via inhibition of the Ca2+/CaMKII signal pathway

Vascular dementia (VD) is a common disease that occurs during human aging. Gastrodin (GAS) has potential benefits for the prevention and treatment of VD. In the present study, we investigated the effects of GAS on cognitive dysfunction in rats with VD induced by permanent middle cerebral artery occlusion (pMCAO) and explored the underlying mechanism. Immunohistochemical and western blot analyses revealed that GAS attenuated hippocampal levels of LC3 (microtubule-associated protein 1 light chain 3), p62, and phosphorylated CaMKII (Ca2+-calmodulin stimulated protein kinase II) in VD rats. Additionally, our results revealed that cobalt chloride blocked autophagic flux in HT22 cells, which was confirmed by increased levels of LC3 and p62 when combined with chloroquine. Notably, GAS ameliorated the impaired autophagic flux. Furthermore, we confirmed that GAS combined with KN93 (a CaMKII inhibitor) or CaMKII knockdown did not impact the reduced p62 levels when compared with GAS treatment alone. Furthermore, a co-immunoprecipitation assay demonstrated that endogenous p62 bound to CaMKII, as confirmed by mass spectrometric analysis after the immunoprecipitation of p62 from HT22 cells. These findings revealed that GAS attenuated autophagic flux dysfunction by inhibiting the Ca2+/CaMKII signaling pathway to ameliorate cognitive impairment in VD.

Gating of hippocampal rhythms and memory by synaptic plasticity in inhibitory interneurons

Mental experiences can become long-term memories if the hippocampal activity patterns that encode them are broadcast during network oscillations. The activity of inhibitory neurons is essential for generating these neural oscillations, but molecular control of this dynamic process during learning remains unknown. Here, we show that hippocampal oscillatory strength positively correlates with excitatory monosynaptic drive onto inhibitory neurons (E→I) in freely behaving mice. To establish a causal relationship between them, we identified γCaMKII as the long-sought mediator of long-term potentiation for E→I synapses (LTP_E→I), which enabled the genetic manipulation of experience-dependent E→I synaptic input/plasticity. Deleting γCaMKII in parvalbumin interneurons selectively eliminated LTP_E→I and disrupted experience-driven strengthening in theta and gamma rhythmicity. Behaviorally, this manipulation impaired long-term memory, for which the kinase activity of γCaMKII was required. Taken together, our data suggest that E→I synaptic plasticity, exemplified by LTP_E→I, plays a gatekeeping role in tuning experience-dependent brain rhythms and mnemonic function.

Exosomal miR-211 contributes to pulmonary hypertension via attenuating CaMK1/PPAR-γaxis

AIM

Exsomes play a significant role in increasing pathophysiological processes by delivering their content. Recently, a variety of studies have showed exosomal microRNAs (miRNAs) are involved in pulmonary hypertension (PH) notably. In this study, we found that exosomal miR-211 was overexpressed in hypoxia-induced PH rats but its intrinsic regulation was unclear. Therefore, our aim was to reveal the underlying mechanism which overexpressed exosomal miR-211 targeted in the development of PH.

METHODS

18 male SD rats were randomly divided into normoxia and hypoxia group, housed in normal or hypoxic chamber for 3 weeks respectively. Then, mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance(PVR), right ventricular hypertrophy index(RV/(LV + S)), the percentage of medial wall area (WA%) and the percentage of medial wall thickness (WT%) were measured. Expression of miR-211 in exosomes was detected by qRT-PCR. Expression of Ca2+/calmodulin-dependent kinase1(CaMK1)and peroxisome proliferator-activated receptors-γ(PPAR-γ)in lung tissue were detected by Western blot(WB); After miR-211 overexpressed exosomes were injected to rats through caudal vein, mPAP, PVR, RV/(LV + S), WA% and WT% were also measured. Sequentially, hypoxia rats were injected with lentivirus riched in miR-211 inhibitor via tail vein, and PH-related indicators were measured. In vitro, after miR-211 was positively or negatively regulated in pulmonary arterial smooth muscle cell (PASMC) by plasmid transfection, proliferation of PASMC was detected by CCK8, as well as the expression of CaMK1 and PPAR- γ. Further, the relationship between CaMK1 and miR-211 was verified by Dual-Luciferase assay. And the regulatory relationship of CaMK1/PPAR- γ aixs was demonstrated in PASMC.

RESULTS

Evident increases of mPAP, PVR, RVHI, WT% and WA% were observed with hypoxia administration. And the concentration of plasma exosomes in hypoxia rats was increased and positively correlated with the above indexes. miR-211 in exosomes of PH was upregulated while the expression of CaMK1 and PPAR-γ decreased in lung tissues. Further, injection of exosomes overexpressed with miR-211 demonstrated that exosomal miR-211 aggravated PH while inhibition of miR-211 attenuated PH in rats. In vitro, overexpression of miR-211 promoted the proliferation of PASMC and inhibited expression of CaMK1 and PPAR-γ in PASMC. And Dual-luciferase assay demonstrated that CaMK1 was a downstream gene of miR-211. Plasmid transfection experiments indicated that CaMK1 can promote PPAR-γ expression.

CONCLUSION

Exosomal miR-211 promoted PH via inhibiting CaMK1/PPAR-γ axis, promoting PASMC proliferation in rats.

Calmodulin/CaMKII-γ mediates prosurvival capability in apicidin-persistent hepatocellular carcinoma cells via ERK1/2/CREB/c-fos signaling pathway

Calmodulin (CaM), a Ca²⁺ binding protein, plays a critical role in cancer initiation and progression through binding and activating numerous target proteins, including Ca²⁺ /calmodulin-dependent protein kinase (CaMK) family proteins. However, the mechanisms underlying the effects of CaM/CaMKs on the survival capability of liver cancer cells is unclear, and this study investigates this mechanism in apicidin-persistent HA22T cells. CaM level was upregulated, especially in the cytosol, in apicidin-persistent HA22T cells than in parental HA22T cells and was positively associated with cell proliferation and migration capacity of apicidin-persistent HA22T cells. Further, the expression of CaM-activated CaMKs-dependent signaling cascades, including CaMKK2, CaMKIV, CaMKII-γ, and p-CaMKII was observed in apicidin-persistent HA22T cells, which were transiently activated by mitogen-activated protein kinase oncogenic signaling, such as CREB, ERK1/2, and c-fos. Furthermore, a specific CaM inhibitor trifluoperazine reduced the levels of p-CREB, p-ERK1/2, and c-fos in apicidin-persistent HA22T cells than in parental HA22T cells. Additionally, inhibition of CaM also suppressed CaM-induced Bcl-XL (an antiapoptotic protein) expression in apicidin-persistent HA22T cells. Our finding emphasizes an essential role of CaM/CaMKs in augmentation of the survival capability of apicidin-persistent liver cancer cells and suggests that CaM inhibition significantly attenuates CaM-induced tumor growth and abrogates antiapoptotic function and also offers a promising therapeutic target for cancer treatment.

The NMDAR GluN1-1a C-terminus binds to CaM and regulates synaptic function

The binding of calmodulin (CaM) to NMDAR (N-methyl-D-aspartate receptor) GluN1 C-terminus is required for cacium (Ca²⁺)/calmodulin (CaM)-dependent inactivation of NMDAR. Previously, we found that GluN1 C-terminus translocated to nucleus, and regulated synaptic transmission. However, whether GluN1 C-terminus containing the nuclear localization signaling regulates the cellular distribution of CaM, and the CaM binding are not clear. In this study, we found that the 10 positive residues of GluN1 C-terminus determined the translocation of CaM to the nucleus. RNA sequencing data showed that CaM could regulate the genes expression of multiple cell surface membrane receptors. This was confirmed by electrophysiology data that the 10A mutation of GluN1 C-terminus increased the NMDAR/AMAPR-mediated synaptic transduction.

HIF/Ca2+/NO/ROS is critical in roxadustat treating bone fracture by stimulating the proliferation and migration of BMSCs

AIMS

Fracture site is regionally hypoxic resulting from vasculature disruption. HIF-1αplays an essential role in fracture repair. This study aims to investigate the influence of FG4592 on the femur fracture of SD rats and the proliferation, migration of BMSCs.

MATERIALS AND METHODS

After the femoral fracture model was established, computed tomography imaging and histological analyses were used to quantify bone healing and the expression of CD90, HIF-1α, VEGF were observed by means of immunohistochemistry method on Day 10 and Day 20. In addition, CCK-8 assay, transwell, flow cytometric analysis, laser confocal microscopy assay, western blot and rT-PCR were performed to text the proliferation and migration of BMSCs using FG4592.

KEY FINDINGS

In vivo, FG4592 facilitated the repair of bone fracture by increasing the number of BMSCs and cartilage formation. In vitro, FG4592 markedly improved the proliferation, migration of BMSCs via upregulation of intracellular Ca²⁺, NO and concomitant decrease of ROS. Gene silencing of HIF-1α resulted in the opposite phenomenon in BMSCs with the treatment of FG4592.

SIGNIFICANCE

The transplantation of BMSCs is the most promising candidate for the treatment of fracture non-union. We illustrated that FG4592 promoted the proliferation, migration of BMSCs via the HIF/Ca²⁺/NO/ROS pathway and further accelerated fracture healing. These results provide a deeper understanding for the mechanism of HIF in promoting fracture healing.

Adipose-Derived Mesenchymal Stem Cells and Conditioned Medium Attenuate the Memory Retrieval Impairment During Sepsis in Rats

In this study, we hypothesized that sepsis induction impairs memory retrieval in rats while transplanted mesenchymal stem cells (MSCs) and MSC-conditioned medium (MSC-CM) application are capable of attenuating those complications. MSCs were obtained from adipose tissue of rats and at the second culture passage; MSCs and MSC-CM were collected. Rats were randomly divided into four experimental groups: sham, CLP, MSC, and MSC-CM. Sepsis was induced by cecal ligation and puncture (CLP) model in the CLP, MSC, and MSC-CM groups. The MSC group received 1 × 106 MSCs/rat (i.p., 2 h after CLP surgery); the MSC-CM rats received the conditioned medium (CM) from 1 × 106 MSCs intraperitoneally 2 h after sepsis induction. Novel object recognition test, sepsis score, and blood pressure measurement were performed 24 h after the treatments. The right hippocampus was taken for western blot analysis. CLP rats showed a significantly higher sepsis score and systolic blood pressure. They also had a significant increase in the phosphorylated form of CAMKII-α, cleaved caspase 3 and Bax/Bcl2 ratio, and a reduction in c-fos protein in the hippocampus tissue samples compared with the sham group. MSC transplantation and MSC-CM administration significantly decreased the mean sepsis score and prevented sepsis-induced attenuation of blood pressure compared with the CLP rats. Animals in the MSC and MSC-CM groups showed a better memory retrieval, attenuation in phosphorylated form of CAMKII-α, cleaved caspase 3 and Bax/Bcl2 ratio, and an increase in c-fos protein expression compared with the CLP group. It seems that CAMKII and c-fos are inversely involved in regulating memory processes in hippocampus. Phosphorylated form of CaMKII-α overexpression may impair the ability of object recognition. Our findings confirmed that MSC-CM application has more advantages compared with transplanted MSCs and may be offered as a promising therapy for inflammatory diseases such as severe sepsis.

Interactions between calmodulin and neurogranin govern the dynamics of CaMKII as a leaky integrator

Calmodulin-dependent kinase II (CaMKII) has long been known to play an important role in learning and memory as well as long term potentiation (LTP). More recently it has been suggested that it might be involved in the time averaging of synaptic signals, which can then lead to the high precision of information stored at a single synapse. However, the role of the scaffolding molecule, neurogranin (Ng), in governing the dynamics of CaMKII is not yet fully understood. In this work, we adopt a rule-based modeling approach through the Monte Carlo method to study the effect of Ca2+ signals on the dynamics of CaMKII phosphorylation in the postsynaptic density (PSD). Calcium surges are observed in synaptic spines during an EPSP and back-propagating action potential due to the opening of NMDA receptors and voltage dependent calcium channels. Using agent-based models, we computationally investigate the dynamics of phosphorylation of CaMKII monomers and dodecameric holoenzymes. The scaffolding molecule, Ng, when present in significant concentration, limits the availability of free calmodulin (CaM), the protein which activates CaMKII in the presence of calcium. We show that Ng plays an important modulatory role in CaMKII phosphorylation following a surge of high calcium concentration. We find a non-intuitive dependence of this effect on CaM concentration that results from the different affinities of CaM for CaMKII depending on the number of calcium ions bound to the former. It has been shown previously that in the absence of phosphatase, CaMKII monomers integrate over Ca2+ signals of certain frequencies through autophosphorylation (Pepke et al, Plos Comp. Bio., 2010). We also study the effect of multiple calcium spikes on CaMKII holoenzyme autophosphorylation, and show that in the presence of phosphatase, CaMKII behaves as a leaky integrator of calcium signals, a result that has been recently observed in vivo. Our models predict that the parameters of this leaky integrator are finely tuned through the interactions of Ng, CaM, CaMKII, and PP1, providing a mechanism to precisely control the sensitivity of synapses to calcium signals. Author Summary not valid for PLOS ONE submissions.

The Regulating Mechanism of Chrysophanol on Protein Level of CaM-CaMKIV to Protect PC12 Cells Against Aβ25-35-Induced Damage

Objective

To investigate the neuroprotective effect of chrysophanol (CHR) on PC12 treated with Aβ_25-35, and the involved mechanism.

Methods

After the establishment of an AD cell model induced by Aβ_25-35, the cell survival rate was detected by MTT, cell apoptosis was assayed by Hoechst 33342 staining, mRNA expressions of calmodulin (CaM), calcium/calmodulin-dependent protein kinase kinase (CaMKK), calcium/calmodulin-dependent protein kinase IV (CaMKIV) and tau (MAPT; commonly known as tau) were determined by qRT-PCR, and protein levels of CaM, CaMKK, CaMKIV, phospho-CaMKIV (p-CaMKIV), tau and phospho-tau (p-tau) were detected by Western blot analysis.

Results

When pretreated with CHR before exposure to Aβ_25-35, PC12 cells showed that increased cell viability and reduced apoptosis. The qRT-PCR results indicated that the deposition of Aβ_25-35 triggers a decrease in levels of CaM, CaMKK, CaMKIV, and tau in PC12 cells. In addition, Western blot results also suggested that Aβ_25-35 decreases the protein expression of CaM, CaMKK, CaMKIV, p-CaMKIV, and the ratio of p-tau to tau in PC12 cells. However, the above effects were significantly alleviated after the treatment of CHR.

Conclusion

CHR plays a neuroprotective role in AD though decreasing the protein level of CaM-CaMKK-CaMKIV and the expression of p-tau downstream.

CaMKII enhances voltage-gated sodium channel Nav1.6 activity and neuronal excitability

Nav1.6 is the primary voltage-gated sodium channel isoform expressed in mature axon initial segments and nodes, making it critical for initiation and propagation of neuronal impulses. Thus, Nav1.6 modulation and dysfunction may have profound effects on input-output properties of neurons in normal and pathological conditions. Phosphorylation is a powerful and reversible mechanism regulating ion channel function. Because Nav1.6 and the multifunctional Ca²⁺/CaM-dependent protein kinase II (CaMKII) are independently linked to excitability disorders, we sought to investigate modulation of Nav1.6 function by CaMKII signaling. We show that inhibition of CaMKII, a Ser/Thr protein kinase associated with excitability, synaptic plasticity, and excitability disorders, with the CaMKII-specific peptide inhibitor CN21 reduces transient and persistent currents in Nav1.6-expressing Purkinje neurons by 87%. Using whole-cell voltage clamp of Nav1.6, we show that CaMKII inhibition in ND7/23 and HEK293 cells significantly reduces transient and persistent currents by 72% and produces a 5.8-mV depolarizing shift in the voltage dependence of activation. Immobilized peptide arrays and nanoflow LC-electrospray ionization/MS of Nav1.6 reveal potential sites of CaMKII phosphorylation, specifically Ser-561 and Ser-641/Thr-642 within the first intracellular loop of the channel. Using site-directed mutagenesis to test multiple potential sites of phosphorylation, we show that Ala substitutions of Ser-561 and Ser-641/Thr-642 recapitulate the depolarizing shift in activation and reduction in current density. Computational simulations to model effects of CaMKII inhibition on Nav1.6 function demonstrate dramatic reductions in spontaneous and evoked action potentials in a Purkinje cell model, suggesting that CaMKII modulation of Nav1.6 may be a powerful mechanism to regulate neuronal excitability.

Extrasynaptic CaMKIIα is involved in the antidepressant effects of ketamine by downregulating GluN2B receptors in an LPS-induced depression model

BACKGROUND

A subanesthetic dose of ketamine provides rapid and effective antidepressant effects, but the molecular mechanism remains elusive. It has been reported that overactivation of extrasynaptic GluN2B receptors is associated with the antidepressant effects of ketamine and the interaction between GluN2B and calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) is important for GluN2B localization and activity. Here, we tested whether changes of CaMKIIα and GluN2B are involved in the antidepressant effects of ketamine.

METHODS

Lipopolysaccharide (LPS) was injected intraperitoneally (i.p.) into male C57BL/6 mice. For the interventional study, mice were administrated with ketamine (10 mg/kg, i.p.) or a CaMKIIα inhibitor KN93. Behavioral alterations were evaluated by open-field, novelty-suppressed feeding, and forced-swimming tests. Physiological functions were evaluated by the body weight and fur coat state of mice. The levels of p-CaMKIIα, CaMKIIα, p-GluN2B, GluN2B, p-CREB, CREB, BDNF, GluR1, and GluR2 in the hippocampus were detected by western blotting. The interaction between GluN2B and CaMKIIα was studied using immunoprecipitation assay and small interfering RNA (siRNA) assays. The colocalizations of GluN2B/PSD95 and p-GluN2B/PSD95 were detected by immunofluorescence. The long-term potentiation (LTP) in SC-CA1 of the hippocampus was detected by electrophysiology.

RESULTS

LPS injection induced depression-like behaviors, which were accompanied by significant increases in extrasynaptic p-CaMKIIα expression, extrasynaptic GluN2B localization, and phosphorylation and decreases in p-CREB, BDNF, and GluR1 expressions and LTP impairment. These changes were prevented by ketamine administration. Immunoprecipitation assay revealed that LPS induced an increase in the p-CaMKIIα-GluN2B interaction, which was attenuated by ketamine administration. SiRNA assay revealed that CaMKIIα knockdown reduced the level and number of clusters of GluN2B in the cultured hippocampal neurons. KN93 administration also reduced extrasynaptic p-CaMKIIα expression, extrasynaptic GluN2B localization, and phosphorylation and exerted antidepressant effects.

CONCLUSION

These results indicate that extrasynaptic CaMKIIα plays a key role in the cellular mechanism of ketamine's antidepressant effect and it is related to the downregulation of extrasynaptic GluN2B localization and phosphorylation.

Structural Insights into the Regulation of Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII)

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is a highly conserved serine/threonine kinase that is ubiquitously expressed throughout the human body. Specialized isoforms of CaMKII play key roles in neuronal and cardiac signaling. The distinctive holoenzyme architecture of CaMKII, with 12-14 kinase domains attached by flexible linkers to a central hub, poses formidable challenges for structural characterization. Nevertheless, progress in determining the structural mechanisms underlying CaMKII functions has come from studying the kinase domain and the hub separately, as well as from a recent electron microscopic investigation of the intact holoenzyme. In this review, we discuss our current understanding of the structure of CaMKII. We also discuss the intriguing finding that the CaMKII holoenzyme can undergo activation-triggered subunit exchange, a process that has implications for the potentiation and perpetuation of CaMKII activity.

Glu60 of α-Calcium/calmodulin dependent protein kinase II mediates crosstalk between the regulatory T-site and protein substrate binding region of the active site

Memory formation transpires to be by activation and persistent modification of synapses. A chain of biochemical events accompany synaptic activation and culminate in memory formation. These biochemical events are steered by interplay and modulation of various synaptic proteins, achieved by conformational changes and phosphorylation/dephosphorylation of these proteins. Calcium/calmodulin dependent protein kinase II (CaMKII) and N-methyl-d-aspartate receptors (NMDARs) are synaptic proteins whose interactions play a pivotal role in learning and memory process. Catalytic activity of CaMKII is modulated upon its interaction with the GluN2B subunit of NMDAR. The structural basis of this interaction is not clearly understood. We have investigated the role of Glu⁶⁰ of α-CaMKII, a conserved residue present in the ATP binding region of kinases, in the regulation of catalysis of CaMKII by GluN2B. Mutation of Glu⁶⁰ to Gly exerts different effects on the kinetic parameters of phosphorylation of GluN2B and GluN2A, of which only GluN2B binds to the T-site of CaMKII. GluN2B induced modulation of the kinetic parameters of peptide substrate was altered in the E60G mutant. The mutation almost abolished the modulation of the apparent K_m value for protein substrate. However, although kinetic parameters for ATP were altered by mutating Glu⁶⁰, modulation of the apparent K_m value for ATP by GluN2B seen in WT was exhibited by the E60G mutant of α-CaMKII. Hence our results posit that the communication of the T-site of CaMKII with protein substrate binding region of active site is mediated through Glu⁶⁰ while the communication of the T-site with the ATP binding region is not entirely dependent on Glu⁶⁰.

miR-142-3p Regulates BDNF Expression in Activated Rodent Microglia Through Its Target CAMK2A

Microglia, the innate immune effector cells of the mammalian central nervous system (CNS), are involved in the development, homeostasis, and pathology of CNS. Microglia become activated in response to various insults and injuries and protect the CNS by phagocytosing the invading pathogens, dead neurons, and other cellular debris. Recent studies have demonstrated that the epigenetic mechanisms ensure the coordinated regulation of genes involved in microglial activation. In this study, we performed a microRNA (miRNA) microarray in activated primary microglia derived from rat pup's brain and identified differentially expressed miRNAs targeting key genes involved in cell survival, apoptosis, and inflammatory responses. Interestingly, miR-142-3p, one of the highly up-regulated miRNAs in microglia upon lipopolysaccharide (LPS)-mediated activation, compared to untreated primary microglia cells was predicted to target Ca²⁺/calmodulin dependent kinase 2a (CAMK2A). Further, luciferase reporter assay confirmed that miR-142-3p targets the 3'UTR of Camk2a. CAMK2A has been implicated in regulating the expression of brain-derived neurotrophic factor (BDNF) and long-term potentiation (LTP), a cellular mechanism underlying memory and learning. Given this, this study further focused on understanding the miR-142-3p mediated regulation of the CAMK2A-BDNF pathway via Cyclic AMP-responsive element-binding protein (CREB) in activated microglia. The results revealed that CAMK2A was downregulated in activated microglia, suggesting an inverse relationship between miR-142-3p and Camk2a in activated microglia. Overexpression of miR-142-3p in microglia was found to decrease the expression of CAMK2A and subsequently BDNF through regulation of CREB phosphorylation. Functional analysis through shRNA-mediated stable knockdown of CAMK2A in microglia confirmed that the regulation of BDNF by miR-142-3p is via CAMK2A. Overall, this study provides a database of differentially expressed miRNAs in activated primary microglia and reveals that microglial miR-142-3p regulates the CAMK2A-CREB-BDNF pathway which is involved in synaptic plasticity.

CaMKII(δ) regulates osteoclastogenesis through ERK, JNK, and p38 MAPKs and CREB signalling pathway

Calcium/calmodulin-dependent protein kinases (CaMKs) are a group of important molecules mediating calcium signal transmission and have been proved to participate in osteoclastogenesis regulation. CaMKII, a subtype of CaMKs is expressed during osteoclast differentiation, but its role in osteoclastogenesis regulation remains controversial. In the present study, we identified that both mRNA and protein levels of CaMKII (δ) were upregulated in a time-dependent manner during osteoclast differentiation. CaMKII (δ) gene silencing significantly inhibited osteoclast formation, bone resorption, and expression of osteoclast-related genes, including nuclear factor of activated T cells c1 (NFATc1), tartrate-resistant acid phosphatase (TRAP), and c-Src. Furthermore, CaMKII (δ) gene silencing downregulated phosphorylation of mitogen-activated protein kinases (MAPKs), including JNK, ERK, and p38, which were transiently activated by RANKL. Specific inhibitors of ERK, JNK, and p38 also markedly inhibited expression of osteoclast-related genes, osteoclast formation, and bone resorption like CaMKII (δ) gene silencing. Additionally, CaMKII (δ) gene silencing also suppressed RANKL-triggered CREB phosphorylation. Collectively, these data demonstrate the important role of CaMKII (δ) in osteoclastogenesis regulation through JNK, ERK, and p38 MAPKs and CREB pathway.

SIRT1 Decreases Emotional Pain Vulnerability with Associated CaMKIIα Deacetylation in Central Amygdala

Emotional disorders are common comorbid conditions that further exacerbate the severity and chronicity of chronic pain. However, individuals show considerable vulnerability to the development of chronic pain under similar pain conditions. In this study on male rat and mouse models of chronic neuropathic pain, we identify the histone deacetylase Sirtuin 1 (SIRT1) in central amygdala as a key epigenetic regulator that controls the development of comorbid emotional disorders underlying the individual vulnerability to chronic pain. We found that animals that were vulnerable to developing behaviors of anxiety and depression under the pain condition displayed reduced SIRT1 protein levels in central amygdala, but not those animals resistant to the emotional disorders. Viral overexpression of local SIRT1 reversed this vulnerability, but viral knockdown of local SIRT1 mimicked the pain effect, eliciting the pain vulnerability in pain-free animals. The SIRT1 action was associated with CaMKIIα downregulation and deacetylation of histone H3 lysine 9 at the CaMKIIα promoter. These results suggest that, by transcriptional repression of CaMKIIα in central amygdala, SIRT1 functions to guard against the emotional pain vulnerability under chronic pain conditions. This study indicates that SIRT1 may serve as a potential therapeutic molecule for individualized treatment of chronic pain with vulnerable emotional disorders.SIGNIFICANCE STATEMENT Chronic pain is a prevalent neurological disease with no effective treatment at present. Pain patients display considerably variable vulnerability to developing chronic pain, indicating individual-based molecular mechanisms underlying the pain vulnerability, which is hardly addressed in current preclinical research. In this study, we have identified the histone deacetylase Sirtuin 1 (SIRT1) as a key regulator that controls this pain vulnerability. This study reveals that the SIRT1-CaMKIIaα pathway in central amygdala acts as an epigenetic mechanism that guards against the development of comorbid emotional disorders under chronic pain, and that its dysfunction causes increased vulnerability to the development of chronic pain. These findings suggest that SIRT1 activators may be used in a novel therapeutic approach for individual-based treatment of chronic pain.

Flexible linkers in CaMKII control the balance between activating and inhibitory autophosphorylation

The many variants of human Ca2+/calmodulin-dependent protein kinase II (CaMKII) differ in the lengths and sequences of disordered linkers connecting the kinase domains to the oligomeric hubs of the holoenzyme. CaMKII activity depends on the balance between activating and inhibitory autophosphorylation (on Thr 286 and Thr 305/306, respectively, in the human α isoform). Variation in the linkers could alter transphosphorylation rates within a holoenzyme and the balance of autophosphorylation outcomes. We show, using mammalian cell expression and a single-molecule assay, that the balance of autophosphorylation is flipped between CaMKII variants with longer and shorter linkers. For the principal isoforms in the brain, CaMKII-α, with a ~30 residue linker, readily acquires activating autophosphorylation, while CaMKII-β, with a ~200 residue linker, is biased towards inhibitory autophosphorylation. Our results show how the responsiveness of CaMKII holoenzymes to calcium signals can be tuned by varying the relative levels of isoforms with long and short linkers.

Enhanced CaMKII-Dependent Late I Na Induces Atrial Proarrhythmic Activity in Patients With Sleep-Disordered Breathing

Rationale:

Sleep-disordered breathing (SDB) is frequently associated with atrial arrhythmias. Increased CaMKII (Ca/calmodulin-dependent protein kinase II) activity has been previously implicated in atrial arrhythmogenesis.

Objective:

We hypothesized that CaMKII-dependent dysregulation of Na current (I Na ) may contribute to atrial proarrhythmic activity in patients with SDB.

Methods and Results:

We prospectively enrolled 113 patients undergoing elective coronary artery bypass grafting for cross-sectional study and collected right atrial appendage biopsies. The presence of SDB (defined as apnea-hypopnea index ≥15/h) was assessed with a portable SDB monitor the night before surgery. Compared with 56 patients without SDB, patients with SDB (57) showed a significantly increased level of activated CaMKII. Patch clamp was used to measure I Na . There was a significantly enhanced late I Na , but reduced peak I Na due to enhanced steady-state inactivation in atrial myocytes of patients with SDB consistent with significantly increased CaMKII-dependent cardiac Na channel phosphorylation (Na V 1.5, at serine 571, Western blotting). These gating changes could be fully reversed by acute CaMKII inhibition (AIP [autocamtide-2 related inhibitory peptide]). As a consequence, we observed significantly more cellular afterdepolarizations and more severe premature atrial contractions in atrial trabeculae of patients with SDB, which could be blocked by either AIP or KN93 (N-[2-[[[(E)-3-(4-chlorophenyl)prop-2-enyl]-methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide). In multivariable linear regression models incorporating age, sex, body mass index, existing atrial fibrillation, existing heart failure, diabetes mellitus, and creatinine levels, apnea-hypopnea index was independently associated with increased CaMKII activity, enhanced late I Na and correlated with premature atrial contraction severity.

Conclusions:

In atrial myocardium of patients with SDB, increased CaMKII-dependent phosphorylation of Na V 1.5 results in dysregulation of I Na with proarrhythmic activity that was independent from preexisting comorbidities. Inhibition of CaMKII may be useful for prevention or treatment of arrhythmias in SDB.

Clinical Trial Registration:

URL: http://www.clinicaltrials.gov . Unique identifier: NCT02877745.

Visual Overview:

An online visual overview is available for this article.

Dezocine attenuates the remifentanil-induced postoperative hyperalgesia by inhibition of phosphorylation of CaMKⅡα

Remifentanil, ultra-short-acting μ-opioid receptor agonist, has the greatest advantage in analgesia but could increase postoperative pain scores and induces postoperative hyperalgesia. Dezocine is a mixed opioid receptor partial agonist/antagonist and has been used for postoperative hyperalgesia management in clinical patients,but the potential molecular mechanism is still unclear. Ca²⁺/calmodulin-dependent protein kinase Ⅱ(CaMKⅡ) has been reported involved in remifentanil-induced hyperalgesia (RIH) in previous studies, but the relationship between CaMKⅡ and dezocine in RIH is still unclear. To investigate the mechanism of dezocine in RIH, we used a remifentanil induced postoperative hyperalgesia (RIPH) in incisional pain model of mouse. We subcutaneously infused remifentanil (40 μg/kg) to induce postoperative hyperalgesia. Dezocine (1.5 mg/kg, 3.0 mg/kg, and 6.0 mg/kg) was infused subcutaneously with remifentanil using the apparatus pump for 30 min. Paw withdrawal thermal latency (PWTL) and paw withdrawal mechanical threshold (PWMT) were used to assess thermal hyperalgesia and mechanical allodynia. Western blotting analysis and immunohistochemistry analysis were used to assess the expression of phosphorylated CaMKⅡα (p-CaMKⅡα) in somatosensory cortex, hippocampus and spinal cord. Subcutaneous infusion of remifentanil enhanced postoperative pain induced by surgical incision and increased PWTL and PWMT. Dezocine dose-dependently decreased the PWTL and PWMT in RIPH model. Correlating with behavioral effects, dezocine inhibited remifentanil-induced up-regulation of p-CaMKⅡα expression in somatosensory cortex, hippocampus and spinal cord. Dezocine could attenuate RIPH by suppressing p-CaMKⅡα.

Neurogranin Regulates Metaplasticity

Long-term potentiation (LTP) and long-term depression (LTD) are two major forms of synaptic plasticity that are widely accepted as cellular mechanisms involved in learning and memory. Metaplasticity is a process whereby modifications in synaptic processes shift the threshold for subsequent plasticity. While metaplasticity has been functionally observed, its molecular basis is not well understood. Here, we report that neurogranin (Ng) regulates metaplasticity by shifting the threshold toward potentiation, i.e., increasing Ng in hippocampal neurons lowers the threshold for LTP and augments the threshold for LTD. We also show that Ng does not change the ultrastructural localization of calmodulin (CaM)-dependent protein Kinase II (CaMKII) or calcineurin, critical enzymes for the induction of LTP and LTD, respectively. Interestingly, while CaMKII concentrates close to the plasma membrane, calcineurin concentrates away from the plasma membrane. These data, along with the previous observation showing Ng targets CaM closer to the plasma membrane, suggesting that shifting the localization of CaM within the dendritic spines and closer to the plasma membrane, where there is more CaMKII, may be favoring the activation of CaMKII vs. that of calcineurin. Thus, the regulation of CaM localization/targeting within dendritic spines by Ng may provide a mechanistic basis for the regulation of metaplasticity.

Regulation of Multifunctional Calcium/Calmodulin Stimulated Protein Kinases by Molecular Targeting

Multifunctional calcium/calmodulin-stimulated protein kinases control a broad range of cellular functions in a multitude of cell types. This family of kinases contain several structural similarities and all are regulated by phosphorylation, which either activates, inhibits or modulates their kinase activity. As these protein kinases are widely or ubiquitously expressed, and yet regulate a broad range of different cellular functions, additional levels of regulation exist that control these cell-specific functions. Of particular importance for this specificity of function for multifunctional kinases is the expression of specific binding proteins that mediate molecular targeting. These molecular targeting mechanisms allow pools of kinase in different cells, or parts of a cell, to respond differently to activation and produce different functional outcomes.

A multi-state model of the CaMKII dodecamer suggests a role for calmodulin in maintenance of autophosphorylation

Ca2+/calmodulin-dependent protein kinase II (CaMKII) accounts for up to 2 percent of all brain protein and is essential to memory function. CaMKII activity is known to regulate dynamic shifts in the size and signaling strength of neuronal connections, a process known as synaptic plasticity. Increasingly, computational models are used to explore synaptic plasticity and the mechanisms regulating CaMKII activity. Conventional modeling approaches may exclude biophysical detail due to the impractical number of state combinations that arise when explicitly monitoring the conformational changes, ligand binding, and phosphorylation events that occur on each of the CaMKII holoenzyme's subunits. To manage the combinatorial explosion without necessitating bias or loss in biological accuracy, we use a specialized syntax in the software MCell to create a rule-based model of a twelve-subunit CaMKII holoenzyme. Here we validate the rule-based model against previous experimental measures of CaMKII activity and investigate molecular mechanisms of CaMKII regulation. Specifically, we explore how Ca2+/CaM-binding may both stabilize CaMKII subunit activation and regulate maintenance of CaMKII autophosphorylation. Noting that Ca2+/CaM and protein phosphatases bind CaMKII at nearby or overlapping sites, we compare model scenarios in which Ca2+/CaM and protein phosphatase do or do not structurally exclude each other's binding to CaMKII. Our results suggest a functional mechanism for the so-called "CaM trapping" phenomenon, wherein Ca2+/CaM may structurally exclude phosphatase binding and thereby prolong CaMKII autophosphorylation. We conclude that structural protection of autophosphorylated CaMKII by Ca2+/CaM may be an important mechanism for regulation of synaptic plasticity.

Association Between Side Effects and Blood microRNA Expression Levels and Their Targeted Pathways in Patients With Major Depressive Disorder Treated by a Selective Serotonin Reuptake Inhibitor, Escitalopram: A CAN-BIND-1 Report

INTRODUCTION

Antidepressant drugs are effective therapies for major depressive disorder; however, they are frequently associated with side effects. Although there is some evidence for a relationship between genetic variation and side effects, little is known regarding the role of dynamic molecular factors as moderators of side effects. The aim of this study was to assess microRNA (miRNA) changes associated with side effects during escitalopram treatment and their downstream effects on target gene expression.

METHODS

A total 160 patients with major depressive disorder from the CAN-BIND-1 cohort were included. Side effects were assessed with the Toronto Side Effect Scale after 2 weeks of treatment with escitalopram. We assessed the relationship between side effects and changes in peripheral expression of miRNAs between baseline and week 2. For miRNA whose expression changed, we used target prediction algorithms to identify putative messenger RNA (mRNA) targets and assessed their expression.

RESULTS

Nausea was experienced by 42.5% of patients. We identified 45 miRNAs whose expression changed on initiation of escitalopram treatment, of which 10 displayed a negative association with intensity of nausea (miR15b-5p, miR17-5p, miR20a-5p, miR20b-5p, miR103a-3p, miR103b, miR106a-5p, miR182-5p, miR185-5p, and miR660-5p). Additionally, we found negative associations between 4 microRNAs (miR20a-5p, miR106a-5p, miR185-5p, miR660-5p) and mRNA targets. The expression of the miR185-5p target, CAMK2δ was significantly decreased [log 2 mean = -0.048 (0.233)] between weeks 0 and 2 (P = .01)].

CONCLUSIONS

We identified an overexpression of miR185-5p during escitalopram treatment of major depressive disorder, which was negatively associated with intensity of nausea, and identified a potential mRNA target that may mediate this effect.

Lymnaea stagnalis as model for translational neuroscience research: From pond to bench

The purpose of this review is to illustrate how a reductionistic, but sophisticated, approach based on the use of a simple model system such as the pond snail Lymnaea stagnalis (L. stagnalis), might be useful to address fundamental questions in learning and memory. L. stagnalis, as a model, provides an interesting platform to investigate the dialog between the synapse and the nucleus and vice versa during memory and learning. More importantly, the "molecular actors" of the memory dialogue are well-conserved both across phylogenetic groups and learning paradigms, involving single- or multi-trials, aversion or reward, operant or classical conditioning. At the same time, this model could help to study how, where and when the memory dialog is impaired in stressful conditions and during aging and neurodegeneration in humans and thus offers new insights and targets in order to develop innovative therapies and technology for the treatment of a range of neurological and neurodegenerative disorders.

Brain activity regulates loose coupling between mitochondrial and cytosolic Ca2+ transients

Mitochondrial calcium ([Ca²⁺]_mito) dynamics plays vital roles in regulating fundamental cellular and organellar functions including bioenergetics. However, neuronal [Ca²⁺]_mito dynamics in vivo and its regulation by brain activity are largely unknown. By performing two-photon Ca²⁺ imaging in the primary motor (M1) and visual cortexes (V1) of awake behaving mice, we find that discrete [Ca²⁺]_mito transients occur synchronously over somatic and dendritic mitochondrial network, and couple with cytosolic calcium ([Ca²⁺]_cyto) transients in a probabilistic, rather than deterministic manner. The amplitude, duration, and frequency of [Ca²⁺]_cyto transients constitute important determinants of the coupling, and the coupling fidelity is greatly increased during treadmill running (in M1 neurons) and visual stimulation (in V1 neurons). Moreover, Ca²⁺/calmodulin kinase II is mechanistically involved in modulating the dynamic coupling process. Thus, activity-dependent dynamic [Ca²⁺]_mito-to-[Ca²⁺]_cyto coupling affords an important mechanism whereby [Ca²⁺]_mito decodes brain activity for the regulation of mitochondrial bioenergetics to meet fluctuating neuronal energy demands as well as for neuronal information processing.

CaMKII Activity in the Inflammatory Response of Cardiac Diseases

Inflammation is a physiological process by which the body responds to external insults and stress conditions, and it is characterized by the production of pro-inflammatory mediators such as cytokines. The acute inflammatory response is solved by removing the threat. Conversely, a chronic inflammatory state is established due to a prolonged inflammatory response and may lead to tissue damage. Based on the evidence of a reciprocal regulation between inflammation process and calcium unbalance, here we described the involvement of a calcium sensor in cardiac diseases with inflammatory drift. Indeed, the Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is activated in several diseases with an inflammatory component, such as myocardial infarction, ischemia/reperfusion injury, pressure overload/hypertrophy, and arrhythmic syndromes, in which it actively regulates pro-inflammatory signaling, among which includes nuclear factor kappa-B (NF-κB), thus contributing to pathological cardiac remodeling. Thus, CaMKII may represent a key target to modulate the severity of the inflammatory-driven degeneration.

Myocardial Energy Stress, Autophagy Induction, and Cardiomyocyte Functional Responses

Significance: Energy stress in the myocardium occurs in a variety of acute and chronic pathophysiological contexts, including ischemia, nutrient deprivation, and diabetic disease settings of substrate disturbance. Although the heart is highly adaptive and flexible in relation to fuel utilization and routes of adenosine-5'-triphosphate (ATP) generation, maladaptations in energy stress situations confer functional deficit. An understanding of the mechanisms that link energy stress to impaired myocardial performance is crucial. Recent Advances: Emerging evidence suggests that, in parallel with regulated enzymatic pathways that control intracellular substrate supply, other processes of "bulk" autophagic macromolecular breakdown may be important in energy stress conditions. Recent findings indicate that cargo-specific autophagic activity may be important in different stress states. In particular, induction of glycophagy, a glycogen-specific autophagy, has been described in acute and chronic energy stress situations. The impact of elevated cardiomyocyte glucose flux relating to glycophagy dysregulation on contractile function is unknown. Critical Issues: Ischemia- and diabetes-related cardiac adverse events comprise the majority of cardiovascular disease morbidity and mortality. Current therapies involve management of systemic comorbidities. Cardiac-specific adjunct treatments targeted to manage myocardial energy stress responses are lacking. Future Directions: New knowledge is required to understand the mechanisms involved in selective recruitment of autophagic responses in the cardiomyocyte energy stress response. In particular, exploration of the links between cell substrate flux, calcium ion (Ca²⁺) flux, and phagosomal cargo flux is required. Strategies to target specific fuel "bulk" management defects in cardiac energy stress states may be of therapeutic value.

Interactome Analyses implicated CAMK2A in the genetic predisposition and pharmacological mechanism of Bipolar Disorder

Bipolar disorder (BPD) is a severe mental illness characterized by fluctuations in mood states, behaviors and energy levels. Growing evidence suggests that genes associated with specific illnesses tend to interact together and encode a tight protein-protein interaction (PPI) network, providing valuable information for understanding their pathogenesis. To gain insights into the genetic and physiological foundation of BPD, we conduct the physical PPI analysis of 184 BPD risk genes distilled from genome-wide association studies and exome sequencing studies. We have identified several hub genes (CAMK2A, HSP90AA1 and PLCG1) among those risk genes, and observed significant enrichment of the BPD risk genes in certain pathways such as calcium signaling, oxytocin signaling and circadian entrainment. Furthermore, while none of the 184 genetic risk genes are "well established" BPD drug targets, our PPI analysis showed that αCaMKII (encoded by CAMK2A) had direct physical PPIs with targets (HRH1, SCN5A and CACNA1E) of clinically used anti-manic BPD drugs, such as carbamazepine. We thus speculated that αCaMKII might be involved in the cellular pharmacological actions of those drugs. Using cultured rat primary cortical neurons, we found that carbamazepine treatment induced phosphorylation of αCaMKII in dose-dependent manners. Intriguingly, previous study showed that CAMK2A heterozygous knockout (CAMK2A^+/-) mice exhibited infradian oscillation of locomotor activities that can be rescued by carbamazepine. Our data, in combination with previous studies, provide convergent evidence for the involvement of CAMK2A in the risk of BPD.

Effects of combined traffic noise on the synaptic ultrastructure and expressions of p-CaMKII and NMDAR1 in the hippocampus of young SD rats

In order to explore the effects of combined traffic noise (CTN) on learning and memory function, young Sprague-Dawley (SD) rats were exposed to CTN from highway and high-speed railway for 52 days, whose day-night equivalent continuous A-weighted sound pressure level (L_dn) was 70 dB(A) (corresponding sound pressure level was 80 dB). The synaptic ultrastructure and the expressions of phosphorylated calcium/calmodulin-dependent protein kinase II (p-CaMKII) and N-methyl-D-aspartate receptor 1 (NMDAR1 or NR1) in the hippocampus were tested by transmission electron microscopy (TEM) and Western blot, respectively. Results showed that there was no significant difference in the synaptic ultrastructure and the expressions of p-CaMKII and NR1 in the hippocampus of young rats between the experimental group and control group. Compared with single high-speed railway noise (HSRN) with L_dn of 70 dB(A), CTN had less influences on learning and memory function, which was closely related to smaller intermittency of CTN and less anxiety caused by CTN. In comparison with white noise with a sound pressure level of 80 dB, CTN had less impacts on learning and memory function, which was mainly associated with CTN's smaller R-weighted sound pressure level based on rats' auditory sensitivity.

Proteomic Profile of Carbonylated Proteins Screen the Regulation of Calmodulin-Dependent Protein Kinases-AMPK-Beclin1 in Aerobic Exercise-Induced Autophagy in Middle-Aged Rat Hippocampus

BACKGROUND

Carbonylation is an oxidative modification of the proteins and a marker of oxidative stress. The accumulation of toxic carbonylated proteins might be one of the onsets of pathogenesis in hippocampal aging or neurodegeneration. Enormous evidence indicates that regular aerobic exercise might alleviate the dysfunction of carbonylated proteins, but the adaptational mechanisms in response to exercise are unclear.

OBJECTIVE

This study explored the carbonyl stress mechanism in the hippocampus using proteomics and the role of calmodulin-dependent protein kinases (CAMK)-AMP-activated protein kinase (AMPK)-Beclin1 signaling pathways in alleviating aging or improving function with regular aerobic exercise.

METHODS

Twenty-four healthy 13-month-old male Sprague-Dawley rats (average 693.21 ± 68.85 g) were randomly divided into middle-aged sedentary control group (M-SED, n = 12) and middle-aged aerobic exercise runner group (M-EX, n = 12). The M-EX group participated in regular aerobic exercise - treadmill running - with exercise intensity increasing gradually from 50-55% to 65-70% of maximum oxygen consumption (V˙O2max) over 10 weeks. The targeted proteins of oxidative modification were profiled by avidin magnetic beads and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS). Western blots were used to test for molecular targets.

RESULTS

Regular aerobic exercise restores the intersessional habituation and rescues the hippocampus morphological structure in middle-aged rats. -ESI-Q-TOF-MS screened 56 carbonylated proteins only found in M-SED and 16 carbonylated proteins only found in M-EX, indicating aerobic exercise decreased carbonyl stress. Intriguingly, Ca2+/CAMK II alpha (CAMKIIα) was carbonylated only in the M-SED group at the oxidative modification site of 4-hydroxynonenal adducts, while regular aerobic exercise alleviated CAMKIIα carbonylation. Regular aerobic exercise significantly increased the expression and phosphorylated, active levels of CAMKIIα and AMPKα1. It also upregulated the expression of Beclin1 and microtubule-associated protein1-light chain 3 in the hippocampus.

CONCLUSION

Quantification of CAMKIIα carbonylation may be a potential biomarker of the hippocampal senescence. Additionally, regular aerobic exercise-induced autophagy via the activation of CAMK-AMPK-Beclin1 signaling pathway may mitigate the hippocampal neurodegeneration or pathological changes by alleviating protein carbonylation (carbonyl stress).

Molecular Characterization of Ca2+/Calmodulin-Dependent Protein Kinase II Isoforms in Three Rice Planthoppers-Nilaparvata lugens, Laodelphax striatellus, and Sogatella furcifera

This study reports the identification of splice variants for the calcium/calmodulin-dependent protein kinase II (CaMKII) gene from Nilaparvata lugens, Laodelphax striatellus, and Sogatella furcifera. CaMKII is a multifunctional serine/threonine protein kinase that transduces Ca²⁺ signals in cells to control a range of cellular processes in the nervous system and muscular tissue. Sequence analysis showed that CaMKII was 99.0% identical at the amino acid level among three rice planthoppers, with the exception of a variable region located in the association domain. Four kinds of 20–81 amino acid “inserts” were found in the variable region. The phylogenetic tree of the deduced amino acid sequences showed that the NlCaMKII isoforms were more closely related to the LsCaMKII isoforms and were slightly distinct from SfCaMKII. CaMKII-E was the dominant type among the five main isoforms. CaMKII genes were constitutively expressed in various nymphal and adult stages and in tested tissues with the predominant transcription occurring in the head. There was no major tissue specificity of isoform expression, but the expression pattern and relative abundance of isoforms varied when compared with the RT-PCR between tissues. In addition, RNAi in N. lugens with dsRNA at a concentration of 200 ng nymph⁻¹ induced a mortality of 77.7% on the 10th day and a reduction in the mRNA expression level of 67.2%. Unlike the holometabolous insect Helicoverpa armigera, the knockdown of NlCaMKII did not suppress the expression of 20E response genes, such as ECR, USP1, and HR3, in N. lugens. These results indicate that the role of CaMKII in hemimetabolous insects may be different from that in holometabolous insects.

The Metastasis Suppressor Protein Nme1 Is a Concentration-Dependent Modulator of Ca2+/Calmodulin-Dependent Protein Kinase II

Nucleoside diphosphate kinases (Nmes or NDPKs) have been implicated in a multitude of cellular processes, including an important role in metastasis suppression, and several enzymatic activities have been assigned to the Nme family. Nevertheless, for many of these processes, it has not been possible to establish a strong connection between Nme enzymatic activity and the relevant biological function. We hypothesized that, in addition to its known enzymatic functions, members of the Nme family might also regulate signaling cascades by acting on key signal transducers. Accordingly, here we show that Nme1 directly interacts with the calcium/calmodulin-dependent kinase II (CaMKII). Using purified proteins, we monitored the phosphorylation of a number of CaMKII substrates and determined that at nanomolar levels Nme1 enhances the phosphorylation of T-type substrates; this modulation shifts to inhibition at low micromolar concentrations. Specifically, the autophosphorylation of CaMKII at Thr286 is completely inhibited by 2 μM Nme1, a feature that distinguishes Nme1 from other known endogenous CaMKII inhibitors. Importantly, CaMKII inhibition does not require phosphotransfer activity by Nme1 because the kinase-dead Nme1 H118F mutant is as effective as the wild-type form of the enzyme. Our results provide a novel molecular mechanism whereby Nme1 could modulate diverse cellular processes in a manner that is independent of its known enzymatic activities.

Inhibition of CaMKIIα Activity Enhances Antitumor Effect of Fullerene C60 Nanocrystals by Suppression of Autophagic Degradation

Fullerene C60 nanocrystals (nano-C60) possess various attractive bioactivities, including autophagy induction and calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) activation. CaMKIIα is a multifunctional protein kinase involved in many cellular processes including tumor progression; however, the biological effects of CaMKIIα activity modulated by nano-C60 in tumors have not been reported, and the relationship between CaMKIIα activity and autophagic degradation remains unclear. Herein, nano-C60 is demonstrated to elicit reactive oxygen species (ROS)-dependent cytotoxicity and persistent activation of CaMKIIα in osteosarcoma (OS) cells. CaMKIIα activation, in turn, produces a protective effect against cytotoxicity from nano-C60 itself. Inhibition of CaMKIIα activity by either the chemical inhibitor KN-93 or CaMKIIα knockdown dramatically promotes the anti-OS effect of nano-C60. Moreover, inhibition of CaMKIIα activity causes lysosomal alkalinization and enlargement, and impairs the degradation function of lysosomes, leading to autophagosome accumulation. Importantly, excessive autophagosome accumulation and autophagic degradation blocking are shown to play an important role in KN-93-enhanced-OS cell death. The synergistic anti-OS efficacy of KN-93 and nano-C60 is further revealed in an OS-xenografted murine model. The results demonstrate that CaMKIIα inhibition, along with the suppression of autophagic degradation, presents a promising strategy for improving the antitumor efficacy of nano-C60.

Inhibition of Calcium/Calmodulin-Dependent Protein Kinase IIα Suppresses Oxidative Stress in Cerebral Ischemic Rats Through Targeting Glucose 6-Phosphate Dehydrogenase

Ischemic stroke is a leading cause of mortality and morbidity worldwide, and oxidative stress plays a significant role in the ischemia stage and reperfusion stage. Previous studies have indicated that both calcium/calmodulin-dependent protein kinase II (CaMKII) and glucose 6-phosphate dehydrogenase (G6PD) are involved in the oxidative stress. Thus, the aim of this study was to investigate the roles of CaMKIIα, an important isoform of CaMKII, and G6PD in a rat model of middle cerebral artery occlusion (MCAO). Intracerebroventricular injection of small interfering ribonucleic acid (siRNA) for CaMKIIα was performed at 48 h pre-MCAO surgery. Immunofluorescence Staining and western blot were performed to detect the expression of p-CaMKIIα and G6PD in the cortices. 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining was performed to investigate the infarct volume. In addition, neurological deficit, reactive oxygen species (ROS), ratio of reduced-to-oxidized glutathione (GSH/GSSG) and ratio of reduced-to-oxidized oxidized nicotinamide adenine dinucleotide phosphate (NADPH/NADP⁺) were assessed. The results indicated that both p-CaMKIIα and G6PD were widely located in the neurons and astrocytes, and their expression was gradually increased in the cortices after MCAO, which was accompanied by increased level of ROS and decreased levels of GSH/GSSG and NADPH/NADP⁺. However, after treatment with siRNA for CaMKIIα, p-CaMKIIα expression was decreased and G6PD expression was increased. Moreover, inhibition of CaMKIIα improved the neurological deficit, reduced the infarct volume, decreased the level of ROS and increased the levels of GSH/GSSG and NADPH/NADP⁺. The results suggested that CaMKIIα inhibition exerted neuroprotective effects through regulating G6PD expression, which provides a new target for prevention and treatment of stroke.

Effects of HIV-1 Tat on oligodendrocyte viability are mediated by CaMKIIβ-GSK3β interactions

Myelin disruptions are frequently reported in human immunodeficiency virus (HIV)-infected individuals and can occur in the CNS very early in the disease process. Immature oligodendrocytes (OLs) are quite sensitive to toxic increases in [Ca²⁺ ]_i caused by exposure to HIV-1 Tat (transactivator of transcription, a protein essential for HIV replication and gene expression), but sensitivity to Tat-induced [Ca²⁺ ]_i is reduced in mature OLs. Tat exposure also increased the activity of Ca²⁺ /calmodulin-dependent kinase IIβ (CaMKIIβ), the major isoform of CaMKII expressed by OLs, in both immature and mature OLs. Since CaMKIIβ is reported to interact with glycogen synthase kinase 3β (GSK3β), and GSK3β activity is implicated in OL apoptosis as well as HIV neuropathology, we hypothesized that disparate effects of Tat on OL viability with maturity might be because of an altered balance of CaMKIIβ-GSK3β activities. Tat expression in vivo led to increased CaMKIIβ and GSK3β activity in multiple brain regions in transgenic mice. In vitro, immature murine OLs expressed higher levels of GSK3β, but much lower levels of CaMKIIβ, than did mature OLs. Exogenous Tat up-regulated GSK3β activity in immature, but not mature, OLs. Tat-induced death of immature OLs was rescued by the GSK3β inhibitors valproic acid or SB415286, supporting involvement of GSK3β signaling. Pharmacologically inhibiting CaMKIIβ increased GSK3β activity in Tat-treated OLs, and genetically knocking down CaMKIIβ promoted death in mature OL cultures treated with Tat. Together, these results suggest that the effects of Tat on OL viability are dependent on CaMKIIβ-GSK3β interactions, and that increasing CaMKIIβ activity is a potential approach for limiting OL/myelin injury with HIV infection.

Salicylate-Induced Ototoxicity of Spiral Ganglion Neurons: Ca2+/CaMKII-Mediated Interaction Between NMDA Receptor and GABAA Receptor

Sodium salicylate (SS) is one of the nonsteroidal anti-inflammatory drugs and widely used in clinical practice. Therefore, we aimed to investigate the potential ototoxicity mechanism of sodium salicylate: the influence of Ca²⁺/calmodulin-dependent protein kinase II (Ca²⁺/CaMKII) in interaction between NMDA receptors (NMDAR) and GABA_A receptors (GABA_AR) in rat cochlear spiral ganglion neurons (SGNs). After treatment with SS, NMDA, and an NMDAR inhibitor (APV), the changes of GABA_AR β3 (GABR β3) mRNA, surface and total protein, and GABA_AR currents in SGNs were assessed by quantitative PCR, Western blot, and whole-cell patch clamp. Mechanistically, SS and/or NMDA increased the GABR β3 mRNA expression, while decreased GABR β3 surface protein levels and GABA_AR-mediated currents. Moreover, application of SS and/or NMDA showed promotion in phosphorylation levels at S383 of GABR β3. Collectively, Ca²⁺ chelator (BAPTA) or Ca²⁺/CaMKII inhibitor (KN-93) reversed the effects of SS and/or NMDA on GABA_AR. Therefore, we hypothesize that the interaction between NMDAR and GABA_AR is involved in the SGNs damage induced by SS. In addition, the underlying molecular mechanism is related to Ca²⁺/CaMKII-mediated signaling pathway, which suggests that the interaction between calcium signal-regulated receptors mediates SS ototoxicity.