Calcium/calmodulin-dependent Protein Kinase II Expression Research Articles

Ca2+/Calmodulin-Dependent Protein Kinase II Regulation by Inhibitor of Receptor Interacting Protein Kinase 3 Alleviates Necroptosis in Glycation End Products-Induced Cardiomyocytes Injury.

Necroptosisis a regulatory programmed form of necrosis. Receptor interacting protein kinase 3 (RIPK3) is a robust indicator of necroptosis. RIPK3 mediates myocardial necroptosis through activation of calcium/calmodulin-dependent protein kinase II (CaMKII) in cardiac ischemia-reperfusion (I/R) injury and heart failure. However, the exact mechanism of RIPK3 in advanced glycation end products (AGEs)-induced cardiomyocytes necroptosis is not clear. In this study, cardiomyocytes were subjected to AGEs stimulation for 24 h. RIPK3 expression, CaMKII expression, and necroptosis were determined in cardiomyocytes after AGEs stimulation. Then, cardiomyocytes were transfected with RIPK3 siRNA to downregulate RIPK3 followed by AGEs stimulation for 24 h. CaMKIIδ alternative splicing, CaMKII activity, oxidative stress, necroptosis, and cell damage were detected again. Next, cardiomyocytes were pretreated with GSK′872, a specific RIPK3 inhibitor to assess whether it could protect cardiomyocytes against AGEs stimulation. We found that AGEs increased the expression of RIPK3, aggravated the disorder of CaMKII δ alternative splicing, promoted CaMKII activation, enhanced oxidative stress, induced necroptosis, and damaged cardiomyocytes. RIPK3 downregulation or RIPK3 inhibitor GSK′872 corrected CaMKIIδ alternative splicing disorder, inhibited CaMKII activation, reduced oxidative stress, attenuated necroptosis, and improved cell damage in cardiomyocytes.

P21-Activated Kinase 1 Promotes Breast Tumorigenesis via Phosphorylation and Activation of the Calcium/Calmodulin-Dependent Protein Kinase II.

p21-Activated kinase-1 (Pak1) is frequently overexpressed and/or amplified in human breast cancer and is necessary for transformation of mammary epithelial cells. Here, we show that Pak1 interacts with and phosphorylates the Calcium/Calmodulin-dependent Protein Kinase II (CaMKII), and that pharmacological inhibition or depletion of Pak1 leads to diminished activity of CaMKII. We found a strong correlation between Pak1 and CaMKII expression in human breast cancer samples, and combined inhibition of Pak1 and CaMKII with small-molecule inhibitors was synergistic and induced apoptosis more potently in Her2 positive and triple negative breast cancer (TNBC) cells. Co-adminstration of Pak and CaMKII small-molecule inhibitors resulted in a dramatic reduction of proliferation and an increase in apoptosis in a 3D cell culture setting, as well as an impairment in migration and invasion of TNBC cells. Finally, mice bearing xenografts of TNBC cells showed a significant delay in tumor growth when treated with small-molecule inhibitors of Pak and CaMKII. These data delineate a signaling pathway from Pak1 to CaMKII that is required for efficient proliferation, migration and invasion of mammary epithelial cells, and suggest new therapeutic strategies in breast cancer.

Pain, Anxiety- and Depression-Like Behaviors in Alcohol-Preferring and -NonPreferring Rats

Introduction: Psychiatric disorders such as anxiety, hyperalgesia, and depression have been associated with excessive alcohol drinking, but the neuronal mechanisms involved are only partially understood. Alcoholism more often occurs in individuals with a family history, indicating that genes may play a critical role. Chronic alcohol exposure alters calcium/calmodulin-dependent protein kinase II (CaMKII) signaling in the lateral habenula (LHb), and the LHb is implicated in mediating aversive behaviors, including those related to alcohol. We compared the CaMKII signaling in the LHb and the aberrant behaviors in the selectively bred alcohol-preferring (P) and alcohol-non-preferring (NP) lines of rats. Materials and Methods: The responses to mechanical (Von Frey) and thermal (Hargreaves) nociception tests, anxiety- (elevated plus maze, Marble burying) and depressive-like behaviors (forced swimming) were examined in the alcohol-naïve P and NP rats, as well as in P rats after 4-8 weeks of alcohol consumption; their LHb tissues were also collected for Western blot analysis of CaMKII expression. Results: Compared to NP rats, the P rats had a higher sensitivity to mechanical stimuli, and displayed depressive- and anxiety-like behaviors, as well as a higher level of CaMKII in the LHb. Alcohol consumption alleviated all these behaviors, except for anxiety, and decreased CaMKII levels in the LHb of P rats. Conclusions: The results show that selective breeding for different oral alcohol preference has produced differences in nociception, anxiety, and depression, as well as CaMKII expression in the LHb of P and NP rats. P rats may deal with pain and depression by self-medicating with alcohol.

Ginsenoside Rb1 pretreatment attenuates myocardial ischemia by reducing calcium/calmodulin-dependent protein kinase II-medicated calcium release

Objective: The aim of this study was to investigate the protective effects of ginsenoside Rb1 and assess whether these protective effects are related to calcium/calmodulin-dependent protein kinase II (CaMKII).Methods: A myocardial ischemia (IS) rat. model and a myocardial H9C2 cell hypoxia model were established. MI was induced by occluding the left anterior descending artery for 120 min. Ginsenoside Rb1 (10 mg/kg) was administered 30 min before ischemia induction, and the treatment continued for 7 days. Results: In the rat IS injury model, ginsenoside Rb1 reduced myocardial infarct size, mean left ventricular diastolic pressure, incidence of arrhythmia, and levels of serum creatine kinase, lactate dehydrogenase, and malondialdehyde. However, the mean left ventricular systolic pressure, and maximal rising and falling rates of ventricular pressure (±dp/dtmax) increased. In the myocardial H9C2 cell hypoxia model, ginsenoside Rb1 reduced intracellular calcium concentrations ([Ca2+ ]i) during hypoxia, and markedly reversed the hypoxia-induced decrease in cell survival. Ginsenoside Rb1 was involved in the downregulation of CaMKII and the ryanodine receptor, as well as hypoxia-induced H9C2 cell survival. Conclusion: The findings of the present study suggest that ginsenoside Rb1 attenuates MI injury in rats, partially through the downregulation of CaMKII expression.

Effect of Electroacupuncture on Intracellular Calcium Ion Concentration and Expression of Calcium/Calmodulin Dependent Protein Kinase Ⅱ in Lumbar Spinal Cord in Rats with Neuropathic Pain

To observe the changes of intracellular calcium ([Ca2＋]i) concentration and expression of calcium/calmodulin dependent protein kinaseⅡ (CaMKⅡ) in spinal dorsal horn neurons of spared nerve injury (SNI) rats, so as to explore its mechanisms underlying improvement of neuropathic pain. One hundred and ten SD rats were randomly divided into 5 groups: sham control, model, EA, AP-5 and L-NAME groups. The sham group underwent only a simple separation of the sciatic nerve but without ligation and abscission. The neuropathic pain model was established by abscission of the right tibial and common peroneal nerve. EA (2 Hz, 1－3 mA) was applied to right "Weizhong" (BL 40) and "Huantiao" (GB 30) for 30 min, once a day for 7 days, starting from day 11 after surgery. For rats of the AP-5 and L-NAME groups, AP-5 (a competitive antagonist for NMDA receptor, 0.7 mg·kg－1·d－1) and L-NAME (a non-selective antagonist for nitric oxide synthase [NOS], 60 mg·kg－1·d－1) were respectively administrated by intraperitoneal injection, once daily for 7 days. The mechanical pain threshold was measured, and the calcium fluorescence intensity (shown by Fluo-3/AM calcium fluorescence indicator) of the superficial layer of the lumbar spinal cord (L 4－L 6) was measured by immunohistochemical staining and the expression of spinal cord (L 4－L 6) CaMK Ⅱ protein was detected by Western blot (WB). After modeling, the mechanical pain threshold was significantly decreased on day 10 and 16 after operation in comparison with the sham operation group and baseline data of pre-operation in each group (P<0.01), and remarkably increased in the EA, AP-5 and L-NAME groups relevant to the model group on day 16 (P<0.01, P<0.05), while the effect of EA was significantly superior to that of AP-5 and L-NAME groups (P<0.05), suggesting a reduction of EA analgesia after administration of AP-5 and L-NAME. The concentration of intracellular [Ca2＋]i was significantly higher in the model group than in the sham group, and considerably lower in the EA, AP-5 and L-NAME groups than in the model group (P<0.01, P<0.05). Moreover, the expression level of CaMKⅡ shown by WB and immunohistochemical staining was significantly higher in the model group than in the sham group (P<0.05) and obviously lower in the EA group (not the AP-5 and L-NAME groups) than in the model group on day 16 after the intervention (P<0.05). It suggests an involvement of glutamate NMDA receptor and NMDAR-NOS/NO signaling in the analgesic effect and CaMKⅡ expression down-regulation of EA. EA can ease pain in rats with neuropathic pain, which is closely related to its effect in reducing the calcium concentration and the expression of CaMKⅡ in the lumbar spinal cord, possibly mediated by glutamate NMDA receptor and NMDAR-NOS/NO signaling.

Calcium/Calmodulin-Dependent Protein Kinase II Activity Persists During Chronic β-Adrenoceptor Blockade in Experimental and Human Heart Failure.

Considerable evidence suggests that calcium/calmodulin-dependent protein kinase II (CaMKII) overactivity plays a crucial role in the pathophysiology of heart failure (HF), a condition characterized by excessive β-adrenoceptor (β-AR) stimulation. Recent studies indicate a significant cross talk between β-AR signaling and CaMKII activation presenting CaMKII as a possible downstream mediator of detrimental β-AR signaling in HF. In this study, we investigated the effect of chronic β-AR blocker treatment on CaMKII activity in human and experimental HF. Immunoblot analysis of myocardium from end-stage HF patients (n=12) and non-HF subjects undergoing cardiac surgery (n=12) treated with β-AR blockers revealed no difference in CaMKII activity when compared with non-β-AR blocker-treated patients. CaMKII activity was judged by analysis of CaMKII expression, autophosphorylation, and oxidation and by investigating the phosphorylation status of CaMKII downstream targets. To further evaluate these findings, CaMKIIδC transgenic mice were treated with the β1-AR blocker metoprolol (270 mg/kg*d). Metoprolol significantly reduced transgene-associated mortality (n≥29; P<0.001), attenuated the development of cardiac hypertrophy (-14±6% heart weight/tibia length; P<0.05), and strongly reduced ventricular arrhythmias (-70±22% premature ventricular contractions; P<0.05). On a molecular level, metoprolol expectedly decreased protein kinase A-dependent phospholamban and ryanodine receptor 2 phosphorylation (-42±9% for P-phospholamban-S16 and -22±7% for P-ryanodine receptor 2-S2808; P<0.05). However, this was paralled neither by a reduction in CaMKII autophosphorylation, oxidation, and substrate binding nor a change in the phosphorylation of CaMKII downstream target proteins (n≥11). The lack of CaMKII modulation by β-AR blocker treatment was confirmed in healthy wild-type mice receiving metoprolol. Chronic β-AR blocker therapy in patients and in a mouse model of CaMKII-induced HF is not associated with a change in CaMKII activity. Thus, our data suggest that the molecular effects of β-AR blockers are not based on a modulation of CaMKII. Directly targeting CaMKII may, therefore, further improve HF therapy in addition to β-AR blockade.

613. A Comparison of CNS Transduction After Systemic versus Cranial Delivery of an AAV2/9 CamKII Promoter-eGFP Vector in Mice

Niemann-Pick type C (NPC) disease is a rare but fatal lysosomal storage disorder characterized by accumulation of unesterified cholesterol and other lipids within the lysosome. Clinical manifestations include ataxia, dementia and hepatosplenomegaly. 95% of cases are caused by an NPC1 gene mutation resulting in a lack of functional NPC1 protein, a putative cholesterol transport protein found in the lysosomal limiting membrane. The neuronal pathology seen in NPC1−/− mice begins with cerebellar axonal swelling, progresses to gliosis and visible lipid accumulation within lysosomes, then is followed by a marked loss of Purkinje cells. Weight loss and ataxia accompany disease progression. We have previously demonstrated that systemic delivery of an AAV9 vector designed to express the human NPC1 gene under the control of the neuronal-specific promoter, mouse calcium/calmodulin-dependent protein kinase II (CamKII), to Npc1−/− mice resulted in a modest but significant increase in survival. Transgene expression, assayed by immunohistochemistry (IHC), revealed widespread NPC1 expression within the brain, broadly correlating with the endogenous CamKII expression pattern. Delayed loss of Purkinje cells in the AAV treated Npc1−/− mice was also observed. Despite the increase in lifespan, expression of NPC1 in the Purkinje cells of the AAV treated Npc1−/− mice was limited, and the mice eventually succumbed to NPC1 disease. This result is notable due to the association between Purkinje cell loss and NPC1 disease progression. In an effort to improve neuronal transduction, particularly in Purkinje cells, we have explored various central nervous system (CNS) delivery routes with an AAV9 reporter, configured to express eGFP under the CamKII promoter. Three groups of mice (n=3 mice per group) received stereotactic-guided AAV9 CamKII-eGFP injections into either the lateral ventricles (dose: 3.8 × 1011 GC), cisterna magna (dose: 3.1 × 1011 GC), or a combination of both (dose: 3.8 × 1011 GC). After two weeks, eGFP expression was assessed using IHC and microscopy. Lateral ventricle and combination injections yielded widespread neuronal transduction throughout the brain, but expression in the cerebellum was limited and sporadic. Injections into the cisterna magna - expected to target the cerebellum - did not improve cerebellar expression compared to the other routes. Overall, aside from a heightened intensity of transgene expression, cranial injections did not appear to increase neuronal targeting compared to systemic delivery by retro-orbital injections (dose: 1×1012 GC). Based on preliminary evidence from a limited number of mice, gross differences in transduction between Npc1−/− and control mice were not observed, suggesting that the disease state at the time of assessment did not influence vector tropism. Our results will help define the optimal delivery route for future NPC1 vector optimization studies, and may be informative for others who seek to correct neurodegenerative mouse models using AAV9-mediated gene therapy.

Role of CaMK II in primary somatosensory area and hippocampi in reduction of remifentanil-induced hyperalgesia by lidocaine in rats

Objective To investigate the role of calcium/calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) in the primary somatosensory area (S1 area) and hippocampi in reduction of remifentanil-induced hyperalgesia by lidocaine in rats. Methods One hundred fifty-six male Sprague-Dawley rats, aged 8-10 weeks, weighing 240-260 g, were randomly allocated into 4 groups using a radom number table: control group (group C, n=6), remifentanil group (group R, n=50), lidocaine group (group L, n=50), and remifentanil+ lidocaine group (group RL, n=50). Remifentanil was given as a bolus of 6 mg/kg followed by an 2 h infusion of 2.4 μg·kg-1·min-1 in group R. Lidocaine was given as a bolus of 6 mg/kg followed by an infusion of 200 μg·kg-1·min-1 for 2 h in group L. In group RL, drug administration was similar to those previously described in R and L groups.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured before administration and at 0.5, 2, 5 and 24 h after the end of administration.The rats were then sacrificed immediately after administration and at 0.5, 2, 5 and 24 h after the end of administration in R, L and RL groups, or at the corresponding time point in group C. The S1 area and hippocampi were isolated for determination of phosphorylated CaMKⅡ (p-CaMKⅡ) expression by Western blot. Results Compared with the value before administration, the MWT was significantly decreased at 0.5 and 2 h after the end of administration (P 0.05). Compared with group C, p-CaMKⅡ expression in the S1 area and hippocampi was significantly up-regulated immediately after administration and at 0.5 and 2 h after the end of administration in group R (P 0.05). Conclusion The mechanism by which lidocaine mitigates remifentanil-induced hyperalgesia is associated with inhibited activity of CaMKII in the S1 area and hippocampi of rats. Key words: Piperidines; Lidocaine; Hyperalgesia; Calcium; calmodulin dependent protein kinase type 2; Hippocampus; Somatosensory cortex

Tubulin polymerization disrupts cardiac β-adrenergic regulation of late INa

The anticancer drug paclitaxel (TXL) that polymerizes microtubules is associated with arrhythmias and sinus node dysfunction. TXL can alter membrane expression of Na channels (NaV1.5) and Na current (INa), but the mechanisms are unknown. Calcium/calmodulin-dependent protein kinase II (CaMKII) can be activated by β-adrenergic stimulation and regulates INa gating. We tested whether TXL interferes with isoproterenol (ISO)-induced activation of CaMKII and consequent INa regulation. In wild-type mouse myocytes, the addition of ISO (1 µmol/L) resulted in increased CaMKII auto-phosphorylation (western blotting). This increase was completely abolished after pre-treatment with TXL (100 µmol/L, 1.5 h). The mechanism was further investigated in human embryonic kidney cells. TXL inhibited the ISO-induced β-arrestin translocation. Interestingly, both knockdown of β-arrestin2 expression using small interfering RNA and inhibition of exchange protein directly activated by cAMP (Epac) blocked the ISO-induced CaMKII auto-phosphorylation similar to TXL. The generation of cAMP, however, was unaltered (Epac1-camps). CaMKII-dependent Na channel function was measured using patch-clamp technique in isolated cardiomyoctes. ISO stimulation failed to induce CaMKII-dependent enhancement of late INa and Na channel inactivation (negative voltage shift in steady-state activation and enhanced intermediate inactivation) after pre-incubation with TXL. Consistent with this, TXL also inhibited ISO-induced CaMKII-specific Na channel phosphorylation (at serine 571 of NaV1.5). Pre-incubation with TXL disrupts the ISO-dependent CaMKII activation and consequent Na channel regulation. This may be important for patients receiving TXL treatments, but also relevant for conditions of increased CaMKII expression and enhanced β-adrenergic stimulation like in heart failure.

CaMKII activity is reduced in skeletal muscle during sepsis

Exercise-induced muscle hypertrophy is associated with increased calcium/calmodulin-dependent protein kinase II (CaMKII) expression and activity. In contrast, the influence of muscle atrophy-related conditions on CaMKII is poorly understood. Here, we tested the hypothesis that sepsis-induced muscle wasting is associated with reduced CaMKII expression and activity. Sepsis, induced by cecal ligation and puncture in rats, and treatment of rats with TNFα, resulted in reduced total CaMKII activity in skeletal muscle whereas autonomous CaMKII activity was unaffected. The expression of CaMKIIδ, but not β and γ, was reduced in septic muscle. In additional experiments, treatment of cultured myotubes with TNFα resulted in reduced total CaMKII activity and decreased levels of phosphorylated glycogen synthase kinase (GSK)-3β, a downstream target of CaMKII. The present results suggest that sepsis-induced muscle wasting is associated with reduced CaMKII activity and that TNFα may be involved in the regulation of CaMKII activity in skeletal muscle. Decreased phosphorylation (consistent with activation) of GSK-3β may be a consequence of reduced CaMKII activity, indicating that inhibited CaMKII activity may be involved in the catabolic response to sepsis.

Differentiation of C2C12 cells results in enhanced expression of δ Ca2+/calmodulin‐dependent protein kinase II isoforms

Previous work from our lab provided evidence for increased expression of δ-isoforms of calcium/calmodulin-dependent protein kinase II (CaMKII) in skeletal muscle undergoing regeneration after spontaneous or digitonin-induced necrosis. C2C12 myoblasts were used to examine how CaMKII expression changes during skeletal muscle differentiation. These cells were cultured in 10% fetal bovine serum-containing media and then allowed to differentiate into myotubes for up to 4 days. Western blots of extracts from these cells were probed with a pan antibody against CaMKII, which detected two CaMKII isoforms (50, 51 kDa) in undifferentiated myoblasts. Within 24 hours of differentiation there was a 2–3 fold increase in CaMKII expression that remained elevated during the 4-day period. Furthermore, differentiating cells were found to express 2–3 additional CaMKII bands in the 48–56 kDa range. Probing these samples with a δCaMKII-selective antibody suggested that these expressed proteins were most likely δ-isoforms. RT-PCR of RNA from these cells, using specific primers against the variable regions δCaMKII, produced multiple amplicons that were consistent with the upregulation of δCaMKII isoforms. Confocal imaging of cells labeled with CaMKII antibodies, demonstrated that immunoreactivity to these antibodies was primarily associated with differentiated myofibers rather than myoblasts. These results suggest that differentiating skeletal muscle express multiple isoforms of δCaMKII that may play a critical role in the differentiation/regeneration process.

MicroRNA-148/152 Impair Innate Response and Antigen Presentation of TLR-Triggered Dendritic Cells by Targeting CaMKIIα

MicroRNAs (miRNAs) are involved in the regulation of immunity, including the lymphocyte development and differentiation, and inflammatory cytokine production. Dendritic cells (DCs) play important roles in linking innate and adaptive immune responses. However, few miRNAs have been found to regulate the innate response and APC function of DCs to date. Calcium/calmodulin-dependent protein kinase II (CaMKII), a major downstream effector of calcium (Ca(2+)), has been shown to be an important regulator of the maturation and function of DCs. Our previous study showed that CaMKIIα could promote TLR-triggered production of proinflammatory cytokines and type I IFN. Inspired by the observations that dicer mutant Drosophila display defect in endogenous miRNA generation and higher CaMKII expression, we wondered whether miRNAs can regulate the innate response and APC function of DCs by targeting CaMKIIα. By predicting with software and confirming with functional experiments, we demonstrate that three members of the miRNA (miR)-148 family, miR-148a, miR-148b, and miR-152, are negative regulators of the innate response and Ag-presenting capacity of DCs. miR-148/152 expression was upregulated, whereas CaMKIIα expression was downregulated in DCs on maturation and activation induced by TLR3, TLR4, and TLR9 agonists. We showed that miR-148/152 in turn inhibited the production of cytokines including IL-12, IL-6, TNF-α, and IFN-β upregulation of MHC class II expression and DC-initiated Ag-specific T cell proliferation by targeting CaMKIIα. Therefore, miRNA-148/152 can act as fine-tuner in regulating the innate response and Ag-presenting capacity of DCs, which may contribute to the immune homeostasis and immune regulation.

Human Astrocytes Are Resistant to Fas Ligand and Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand-Induced Apoptosis

Human astrocytes express Fas yet are resistant to Fas-induced apoptosis. Here, we report that calcium/calmodulin-dependent protein kinase II (CaMKII) is constitutively activated in human astrocytes and protects the cells from apoptotic stimulation by Fas agonist. Once stimulated, Fas recruits Fas-associated death domain and caspase-8 for the assembly of the death-inducing signaling complex (DISC); however, caspase-8 cleavage is inhibited in the DISC. Inhibition of CaMKII kinase activity inhibits the expression of phosphoprotein enriched astrocytes-15 kDa/phosphoprotein enriched in diabetes (PEA-15/PED) and cellular Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (c-FLIP), thus releasing their inhibition of caspase-8 cleavage. Inhibition of PEA-15/PED or c-FLIP by small interfering RNA sensitizes human astrocytes to Fas-induced apoptosis. In contrast, inhibition of CaMKII, PEA-15, or c-FLIP does not affect the sensitivity of human astrocytes to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL death receptors (DR4, DR5) are weakly expressed at mRNA, protein, and cell surface levels and thus fail to mediate the assembly of the DISC in human astrocytes. Overexpression of DR5 restores TRAIL signaling pathways and sensitizes the human astrocytes to TRAIL-induced apoptosis if CaMKII kinase activity or expression of PEA-15 and c-FLIP is inhibited; the results suggest that CaMKII-mediated pathways prevent TRAIL-induced apoptosis in human astrocytes under conditions in which TRAIL death receptors are upregulated. This study has therefore identified the molecular mechanisms that protect normal human astrocytes from apoptosis induced by Fas ligand and TRAIL.

Alterations of CaMKII after hypoxia-ischemia during brain development.

Transient brain hypoxia-ischemia (HI) in neonates leads to delayed neuronal death and long-term neurological deficits. However, the underlying mechanisms are incompletely understood. Calcium-calmodulin-dependent protein kinase II (CaMKII) is one of the most abundant protein kinases in neurons and plays crucial roles in synaptic development and plasticity. This study used a neonatal brain HI model to investigate whether and how CaMKII was altered after HI and how the changes were affected by brain development. Expression of CaMKII was markedly up-regulated during brain development. After HI, CaMKII was totally and permanently depleted from the cytosol and concomitantly deposited into a Triton-insoluble fraction in neurons that were undergoing delayed neuronal death. Autophosphorylation of CaMKII-Thr286 transiently increased at 30 min of reperfusion and declined thereafter. All these changes were mild in P7 pups but more dramatic in P26 rats, consistent with the development-dependent CaMKII expression in neurons. The results suggest that long-term CaMKII depletion from the cytosolic fraction and deposition into the Triton-insoluble fraction may disable synaptic development, damage synaptic plasticity, and contribute to delayed neuronal death and long-term synaptic deficits after transient HI.

CyclinB1 expression is elevated and mitosis is delayed in HeLa cells expressing autonomous CaMKII

Calcium is a second messenger that is implicated in the regulation of cell cycle transitions. Calmodulin is a ubiquitous protein that translates intracellular calcium signals and activates several enzymes including calcium/calmodulin-dependent protein kinase II (CaMKII). Pharmacological inhibitors and constitutively active mutants have implicated CaMKII in cell cycle mediation. Specifically, constitutively active CaMKII impedes mitosis. In order to elucidate the molecular mechanisms underlying this phenomenon, the effect of constitutively active CaMKII gene expression on cdc2/cyclin B1 was investigated. As seen in previous studies with S. pombe, constitutively active CaMKII-hindered mitosis. However, this report shows that CaMKII does not cause permanent cell cycle arrest but delays progression into mitosis. Constitutive CaMKII expression also leads to elevations in cyclin B1 expression and cdc2 tyrosine-15 phosphorylation, analogous to observations in cells treated with hydroxyurea. Taken together, these data suggest that constitutive CaMKII may delay mitosis by activating a cell cycle checkpoint.

Molecular cloning and sequence analyses of calcium/calmodulin-dependent protein kinase II from fetal and adult human brain. Sequence analyses of human brain calciuum/calmodulin-dependent protein kinase II.

The aims of this study were to characterize specific mRNAs and the expression pattern for isoforms of calcium/calmodulin-dependent protein kinase II (CaMKII) in the human brain. We cloned and sequenced the CaMKII alpha and beta subunit cDNAs, and used them to study the CaMKII expression in human brain. Four distinct isoforms of CAMKII were isolated. Two of them were characterized as CaMKII alpha and beta subunits. The other two showed similar nucleotide sequences, but one had a 33-bp insertion relative to the alpha subunit, and the other had a 75-bp deletion relative to the beta subunit. These alterations are located within the variable regions. These two isoforms were characterized as CaMKII alphaB and beta(e). Northern blot analysis showed that a 4.4-kb messenger RNA for the alpha isoform and a 3.9-kb messenger RNA for the beta isoform were expressed in both human fetal and adult brain to different degrees. The results indicate that CaMKII expression is developmentally regulated. The CaMKII isoform expression was confirmed in human fetal and adult brain using RT-PCR with specific primers, which flanked the CaMKII variable regions. The CaMKII alpha, alphaB, beta, beta' and beta(e) isoforms were characterized in both human fetal and adult brain.

Stabilization of dendritic arbor structure in vivo by CaMKII.

Calcium-calmodulin-dependent protein kinase II (CaMKII) promotes the maturation of retinotectal glutamatergic synapses in Xenopus. Whether CaMKII activity also controls morphological maturation of optic tectal neurons was tested using in vivo time-lapse imaging of single neurons over periods of up to 5 days. Dendritic arbor elaboration slows with maturation, in correlation with the onset of CaMKII expression. Elevating CaMKII activity in young neurons by viral expression of constitutively active CaMKII slowed dendritic growth to a rate comparable to that of mature neurons. CaMKII overexpression stabilized dendritic structure in more mature neurons, whereas CaMKII inhibition increased their dendritic growth. Thus, endogenous CaMKII activity limits dendritic growth and stabilizes dendrites, and it may act as an activity-dependent mediator of neuronal maturation.