High level expression and preparation of autonomous Ca2+/calmodulin-dependent protein kinase II in Escherichia coli

The chymotryptic fragment of Ca2+/calmodulin-dependent protein kinase II (30K-CaMKII) is a constitutively active enzyme that phosphorylates a variety of protein substrates in vitro. Although 30K-CaMKII is an often used and powerful tool for protein phosphorylation, the efficient production of catalytically active 30K-CaMKII in Escherichia coli has not yet been successfully realized, probably due to its toxicity in host cells. In this study, we found that a high-level expression of 30K-CaMKII as an insoluble form was attained when the N-terminal 43 amino acid residues of Xenopus CaMKI were fused to the N-terminal end of 30K-CaMKII (CX-30K-CaMKII). The inactive CX-30K-CaMKII thus expressed in E. coli was reactivated by simple denaturation/renaturation processes and purified on a Ni2+-chelating column. The renatured CX-30K-CaMKII exhibited specific activity similar to that of rat brain CaMKII, and phosphorylated various proteins such as histones, myosin light chain, myelin basic protein, and synapsin I, as in case of 30K-CaMKII or purified CaMKII. Thus, CX-30K-CaMKII, an autonomous CaMKII, can be obtained with a simple procedure using E. coli expression system.

Axodendritic contacts onto calcium/calmodulin-dependent protein kinase type II-expressing neurons in the barn owl auditory space map

In the owl midbrain, a map of auditory space is synthesized in the inferior colliculus (IC) and conveyed to the optic tectum (OT). Ascending auditory information courses through these structures via topographic axonal projections. Little is known about the molecular composition of projection neurons or their postsynaptic targets. To visualize axodendritic contacts between identified cell types, we used double-label immunohistochemistry, in vivo retrograde tracing, in vitro anterograde tracing, high-resolution confocal microscopy, three-dimensional reconstruction and fly-through visualization. We discovered a major class of IC neurons that strongly expressed calcium/calmodulin-dependent protein kinase type II, alpha subunit (CaMKII). The distribution of these cells within the IC was mostly restricted to the external nucleus of the IC (ICX), in which the auditory space map is assembled. A large proportion of ICX-OT projection neurons were CaMKII positive. In addition to being the principal outputs, CaMKII cells were in direct contact with axonal boutons emanating from the main source of input to ICX, the lateral shell of the central nucleus of the inferior colliculus (ICCls). Numerous sites of putative synaptic contact were found on the somata, proximal dendrites, and distal dendrites. Double-label immunoelectron microscopy confirmed the existence of synapses between ICCls axons and the dendrites of CaMKII cells. Collectively, our data indicate that CaMKII ICX neurons are a cellular locus for the computation of auditory space-specific responses. Because the ICCls-ICX projection is physically altered during experience-dependent plasticity, these results lay the groundwork for probing microanatomical rearrangements that may underlie plasticity and learning.

Prominent expression and activity-dependent nuclear translocation of Ca2+/calmodulin-dependent protein kinase Idelta in hippocampal neurons

Multifunctional Ca2+/calmodulin-dependent protein kinases (CaMKs) including CaMKI, II and IV, are thought to regulate a variety of neuronal functions. Unlike CaMKII, which is regulated by autophosphorylation, CaMKI as well as CaMKIV are activated by CaMKK. In this study, we examined the cellular and subcellular localization of CaMKIdelta, a recently identified fourth isoform of CaMKI, in the mature brain. In situ hybridization analysis demonstrated wide expression of CaMKIdelta mRNA in the adult mouse brain with prominent expression in the hippocampal pyramidal cells. FLAG-tagged CaMKIdelta was localized at the cytoplasm and neurites without nuclear immunoreactivity in approximately 80% of the transfected primary hippocampal neurons. The stimulation with either KCl depolarization or glutamate triggered the nuclear localization of FLAG-tagged CaMKIdelta by two-fold with a peak at 1 min. In contrast, the catalytically inactive mutants of CaMKIdelta remained cytoplasmic without nuclear translocation during KCl depolarization, indicating the requirement of its activation for the nuclear translocation. Furthermore, we showed that immunoprecipitated CaMKIdelta could phosphorylate cAMP response element binding protein (CREB)alphain vitro and that the over-expression of CaMKIdelta enhanced GAL4-CREB-luciferase activity in PC12 cells stimulated by KCl depolarization. Our present study provides the first evidence for the possible involvement of CaMKIdelta in nuclear functions through its nuclear translocation in response to stimuli that trigger intracellular Ca2+ influx.

Behavioral testing upregulates pCaMKII, BDNF, PSD-95 and egr-1 in hippocampus of FVB/N mice

Several protein cascades are proposed to be involved in the formation of synaptic plasticity and have been linked to neuronal information processing and storage. Although modified expression of specific proteins following behavioral testing has been shown, no systematic approach for their concomitant determination has been reported. We therefore determined hippocampal expression of signaling proteins, transcription factors and synaptosomal-associated proteins representing key elements of neuronal plasticity in mice following behavioral training. Male FVB/N mice, 12 weeks of age, were used for behavioral testing. After completion of tests mice were sacrificed and hippocampi were dissected. Levels of total and autophosphorylated (T286) alphacalcium-calmodulin dependent kinase II (CaMKII, pCaMKII), total and phosphorylated mitogen-activated protein kinase (MAPK, pMAPK), total and phosphorylated calcium-responsive element binding (creb, pcreb), early-growth response protein 1 (egr-1), brain derived neurotrophic factor (BDNF), tyrosine kinase receptor B (trk B), drebrin and postsynaptic density-95 (PSD-95) were quantified in hippocampi of behavior trained animals (n=7) and naïve caged controls (n=7). Expression of pCaMKII, BDNF, PSD-95 and egr-1 was significantly increased in the behavior-trained group. Expression of total CaMKII, total and pMAPK, total and pcreb, trk B and drebrin was comparable between groups. Detection of significantly increased pCaMKII, BDNF, PSD-95 and egr-1 induced by behavioral training at the protein level per se is intriguing and supports the proposed importance of these molecules for neuronal information storage.

[Inhibitory effect of 5-Aza-2'-deoxycytidine on human nasopharyngeal carcinoma xenograft in nude mice]

BACKGROUND & OBJECTIVE

5-Aza-2'-deoxycytidine (5-Aza-CdR) is an inhibitor of DNA methyltransferase; it may reactivate methylated antioncogene, therefore, inhibit the growth of cancer cells. This study was to observe the inhibitory effect of 5-Aza-CdR on the growth of human nasopharyngeal carcinoma (NPC) cells and xenografts in nude mice, explore the possible mechanisms, and search for new treatment target of NPC.

METHODS

NPC cell line CNE cells were treated with 5-Aza-CdR; the methylation status of death-associated protein kinase (DAPK) gene was evaluated by methylation-specific polymerase chain reaction (PCR). The model of human NPC xenograft in nude mice was constructed and treated with 5-Aza-CdR; the xenograft growth in nude mice was observed, and the mRNA and protein expression of DAPK was detected by reverse transcription-PCR (RT-PCR) and immunohistochemistry.

RESULTS

No expression of DAPK mRNA was found in CNE cells and the xenografts in nude mice without treatment of 5-Aza-CdR. After treatment, the expression of DAPK mRNA in CNE cells and the xenografts was increased along with the increasing concentration of 5-Aza-CdR; the growth of CNE cells and the xenografts in nude mice were obviously inhibited, and the methylated DAPK gene was reactivated. Four weeks after treatment, no significant difference was found in body weight of nude mice between 5-Aza-CdR group and control group [(22.35+/-2.02) g vs. (21.68+/-2.14) g, t=0.011, P>0.05]; the volume of xenografts was significantly smaller in 5-Aza-CdR group than in control group [(195.32+/-27.57) mm(3) vs. (343.67+/-23.08) mm(3), t=10.11, P<0.01].

CONCLUSION

5-Aza-CdR may reactivate antioncogene silenced by de novo methylation, therefore, inhibit the growth of CNE cells in vivo and in vitro.

Active Ca2+/calmodulin-dependent protein kinase II gamma B impairs positive selection of T cells by modulating TCR signaling

T cell development is regulated at two critical checkpoints that involve signaling events through the TCR. These signals are propagated by kinases of the Src and Syk families, which activate several adaptor molecules to trigger Ca(2+) release and, in turn, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activation. In this study, we show that a constitutively active form of CaMKII antagonizes TCR signaling and impairs positive selection of thymocytes in mice. Following TCR engagement, active CaMKII decreases TCR-mediated CD3zeta chain phosphorylation and ZAP70 recruitment, preventing further downstream events. Therefore, we propose that CaMKII belongs to a negative-feedback loop that modulates the strength of the TCR signal through the tyrosine phosphatase Src homology 2 domain-containing phosphatase 2 (SHP-2).

Calcium/calmodulin-dependent kinase I and calcium/calmodulin-dependent kinase kinase participate in the control of cell cycle progression in MCF-7 human breast cancer cells

Calcium is universally required for cell growth and proliferation. Calmodulin is the main intracellular receptor for calcium. Although calcium and calmodulin are well known to be required for cell cycle regulation, the target pathways for their action remain poorly defined. Potential targets include the calcium/calmodulin-dependent kinases (CaM-K). The aim of this study was to determine the role of the CaM-Ks on cell proliferation and progress through the cell cycle in breast cancer cells. CaM-KI inhibition with either KN-93 or specific interfering RNA (siRNA) caused an arrest in the cell cycle in the human breast cancer cell line, MCF-7. This arrest occurred in the G(1) phase of the cell cycle. Supporting this finding, CaM-K inhibition using KN-93 also resulted in a reduction of cyclin D1 protein and pRb phosphorylation when cells were compared with control cultures. Furthermore, inhibition of the upstream activator of CaM-KI, CaM-KK, using siRNA also resulted in cell cycle arrest. In summary, CaM-KK and CaM-KI participate in the control of the G(0)-G(1) restriction check point of the cell cycle in human breast cancer cells. This arrest seems due to an inhibition in cyclin D1 synthesis and a reduction in pRb phosphorylation. To the best of our knowledge, this is the first time that CaM-KK has been reported to be involved in mammalian cell cycle regulation and that CaM-Ks are regulating breast cancer cell cycle.

A pivotal role for the multifunctional calcium/calmodulin-dependent protein kinase II in T cells: from activation to unresponsiveness

Stimulation of the TCR leads to an oscillatory release of free calcium that activates members of the calcium/calmodulin-dependent protein kinase II (CaMKII) family. The CaMKII molecules have profound and lasting effects on cellular signaling in several cell types, yet the role of CaMKII in T cells is still poorly characterized. In this report we describe a splice variant of CaMKIIbeta, CaMKIIbeta'e, in mouse T cells. We have determined its function, along with that of CaMKIIgamma, by introducing the active and kinase-dead mutants into activated P14 TCR transgenic T cells using retroviral transduction. Active CaMKII enhanced the proliferation and cytotoxic activity of T cells while reducing their IL-2 production. Furthermore, it induced a profound state of unresponsiveness that could be overcome only by prolonged culture in IL-2. These results indicate that members of the CaMKII family play an important role in regulation of CD8 T cell proliferation, cytotoxic effector function, and the response to restimulation.

Kainic acid (KA)-induced Ca2+/Calmodulin-dependent protein kinase II (CaMK II) expression in the neurons, astrocytes and microglia of the mouse hippocampal CA3 region, and the phosphorylated CaMK II only in the hippocampal neurons

In the present study, we investigated the role of Ca2+/calmodulin-dependent protein kinase II (CaMK II) and which types of neuronal cells contain CaMK II and phosphorylated CaMK II (p-CaMK II) in the CA3 hippocampal region of mice using confocal immunofluorescence study. KA increased the CaMK II, p-CaMK II, glial fibrillary acidic protein (GFAP) and complement receptor type 3 (OX-42) immunoreactivities (IR) at 30 min after KA treatment in mouse hippocampal area. In studies, nevertheless KA-induced CaMK II is expressed in neurons or astrocytes or microglia, p-CaMK II is expressed only in neurons. Thus, our results suggest that the activated CaMK II in early time may be performed important roles only in neurons but not in the astrocytes and microglia.

Inhibition of phosphatase activity facilitates the formation and maintenance of NMDA-induced calcium/calmodulin-dependent protein kinase II clusters in hippocampal neurons

The majority of hippocampal neurons in dissociated cultures and in intact brain exhibit clustering of calcium/calmodulin-dependent protein kinase II (CaMKII) into spherical structures with an average diameter of 110 nm when subjected to conditions that mimic ischemia and excitotoxicity [Neuroscience 106 (2001) 69]. Because clustering of CaMKII would reduce its effective concentration within the neuron, it may represent a cellular strategy to prevent excessive CaMKII-mediated phosphorylation during episodes of Ca2+ overload. Here we employ a relatively mild excitatory stimulus to promote sub-maximal clustering for the purpose of studying the conditions for the formation and disappearance of CaMKII clusters. Treatment with 30 microM N-methyl-D-aspartic acid (NMDA) for 2 min produced CaMKII clustering in approximately 15% of dissociated hippocampal neurons in culture, as observed by pre-embedding immunogold electron microscopy. These CaMKII clusters could be labeled with antibodies specific to the phospho form (Thr286) of CaMKII, suggesting that at least some of the CaMKII molecules in clusters are autophosphorylated. To test whether phosphorylation is involved in the formation and maintenance of CaMKII clusters, the phosphatase inhibitors calyculin A (5 nM) or okadaic acid (1 microM) were included in the incubation medium. With inhibitors more neurons exhibited CaMKII clusters in response to 2 min NMDA treatment. Furthermore, 5 min after the removal of NMDA and Ca2+, CaMKII clusters remained and could still be labeled with the phospho-specific antibody. In contrast, in the absence of phosphatase inhibitors, no clusters were detected 5 min after the removal of NMDA and Ca2+ from the medium. These results suggest that phosphatases type 1 and/or 2A regulate the formation and disappearance of CaMKII clusters.

Hypermethylation of the death-associated protein kinase promoter attenuates the sensitivity to TRAIL-induced apoptosis in human non-small cell lung cancer cells

Death-associated protein (DAP) kinase plays an important role in IFN-gamma, tumor necrosis factor (TNF)-alpha, or Fas-ligand induced apoptosis. TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF ligand family and can induce caspase-dependent apoptosis in cancer cells while sparing most of the normal cells. However, some of the cancer cell lines are insensitive to TRAIL, and such resistance cannot be explained by the dysfunction of TRAIL receptors or their known downstream targets. We reported previously that DAP kinase promoter is frequently methylated in non-small cell lung cancer (NSCLC), and such methylation is associated with a poor clinical outcome. To determine whether DAP kinase promoter methylation contributes to TRAIL resistance in NSCLC cells, we measured DAP kinase promoter methylation and its gene expression status in 11 NSCLC cell lines and correlated the methylation/expression status with the sensitivity of cells to TRAIL. Of the 11 cell lines, 1 had a completely methylated DAP kinase promoter and no detectable DAP kinase expression, 4 exhibited partial promoter methylation and substantially decreased gene expression, and the other 6 cell lines showed no methylation in the promoter and normal DAP kinase expression. Therefore, the amount of DAP kinase expression amount was negatively correlated to its promoter methylation (r = -0.77; P = 0.003). Interestingly, the cell lines without the DAP kinase promoter methylation underwent substantial apoptosis even in the low doses of TRAIL, whereas those with DAP kinase promoter methylation were resistant to the treatment. The resistance to TRAIL was reciprocally correlated to DAP kinase expression in 10 of the 11 cell lines at 10 ng/mL concentration (r = 0.91; P = 0.001). We treated cells resistant to TRAIL with 5-aza-2'-deoxycytidine, a demethylating reagent, and found that these cells expressed DAP kinase and became sensitive to TRAIL. These results suggest that DAP kinase is involved in TRAIL-mediated cell apoptosis and that a demethylating agent may have a role in enhancing TRAIL-mediated apoptosis in some NSCLC cells by reactivation of DAP kinase.

Cellular distribution and functions of wild-type and constitutively activated Dictyostelium PakB

Dictyostelium PakB, previously termed myosin I heavy chain kinase, is a member of the p21-activated kinase (PAK) family. Two-hybrid assays showed that PakB interacts with Dictyostelium Rac1a/b/c, RacA (a RhoBTB protein), RacB, RacC, and RacF1. Wild-type PakB displayed a cytosolic distribution with a modest enrichment at the leading edge of migrating cells and at macropinocytic and phagocytic cups, sites consistent with a role in activating myosin I. PakB fused at the N terminus to green fluorescent protein was proteolyzed in cells, resulting in removal of the catalytic domain. C-terminal truncated PakB and activated PakB lacking the p21-binding domain strongly localized to the cell cortex, to macropinocytic cups, to the posterior of migrating cells, and to the cleavage furrow of dividing cells. These data indicate that in its open, active state, the N terminus of PakB forms a tight association with cortical actin filaments. PakB-null cells displayed no significant behavioral defects, but cells expressing activated PakB were unable to complete cytokinesis when grown in suspension and exhibited increased rates of phagocytosis and pinocytosis.

Calcium/calmodulin up-regulates a cytoplasmic receptor-like kinase in plants

Calcium/calmodulin-dependent kinases play an important role in protein phosphorylation in eukaryotes. However, not much is known about calcium/calmodulin-dependent protein phosphorylation and its role in signal transduction in plants. By using a protein-protein interaction-based approach, we have isolated a novel plant-specific calmodulin-binding receptor-like cytoplasmic kinase (CRCK1) from Arabidopsis thaliana, as well as its ortholog from Medicago sativa (alfalfa). CRCK1 does not show high homology to calcium/calmodulin-dependent protein kinases in animals. In contrast, it shows high homology in the kinase domain to serine/threonine receptor-like kinases in plants. However, it contains neither a transmembrane domain nor an extracellular domain. Calmodulin binds to CRCK1 in a calcium-dependent manner with an affinity of approximately 20.5 nm. The calmodulin-binding site in CRCK1 is located in amino acids 160-183, which overlap subdomain II of the kinase domain. CRCK1 undergoes autophosphorylation in the presence of Mg2+ at the threonine residue(s). The Km and Vmax values of CRCK1 for ATP are 1 microm and 33.6 pmol/mg/min, respectively. Calcium/calmodulin stimulates the kinase activity of CRCK1, which increases the Vmax of CRCK1 approximately 9-fold. The expression of CRCK1 is increased in response to stresses such as cold and salt and stress molecules such as abscisic acid and hydrogen peroxide. These results indicate the presence of a calcium/calmodulin-regulated receptor-like cytoplasmic kinase in plants. Furthermore, these results also suggest that calcium/calmodulin-regulated protein phosphorylation involving CRCK1 plays a role in stress signal transduction in plants.

[Hypermethylation of the death-associated protein kinase promoter in laryngeal squamous cell cancer]

OBJECTIVE

To explore the relationship between hypermethylation of the promoter of death-associated protein kinase (DAPK) gene and laryngeal squamous cell cancer.

METHODS

Promoter hypermethylation and mRNA expression of DAPK gene were detected by methylation-specific PCR, RT-PCR and gene sequencing.

RESULTS

Among the 58 patients with laryngeal squamous cell cancer, hypermethylation of DAPK promoter was detected in 39 cases (67.2%). There was no significant difference in hypermethylation in relation to pathological grade and clinical staging, but a highly significant difference was observed between patients with and without lymph node metastasis (N0 and N1) (P < 0.001). DAPK promoter hypermethylation was detected in tumor adjacent tissues in 6 of the 58 cases. DAPK mRNA was not expressed in all laryngeal squamous cell cancers having hypermethylation of DAPK promoter, whereas it was expressed in normal laryngeal mucosa, laryngeal squamous cell cancers without hypermethylation and tumor adjacent tissues.

CONCLUSION

Hypermethylation of DAPK promoter is associated with loss of its transcription in laryngeal squamous cell carcinoma. The high frequency hypermethylation of DAPK promoter illustrates its potential clinical application as tumor marker for diagnosis and prognosis.

Oscillatory shear stress upregulation of endothelial nitric oxide synthase requires intracellular hydrogen peroxide and CaMKII*1

We have previously shown that hydrogen peroxide (H(2)O(2)) upregulates endothelial nitric oxide synthase (eNOS) expression via a calcium/calmodulin-dependent protein kinase II (CaMKII)-mediated mechanism whereas it also acutely activates eNOS enzyme. We hypothesized that oscillatory shear stress (OSS), which stimulates endogenous H(2)O(2), would have effects on eNOS expression and function similar to that of exogenous H(2)O(2). Exposure of bovine aortic endothelial cells to OSS (+/-15 dynes/cm(2)) increased eNOS mRNA expression by 3-fold. Pretreatment with either polyethylene glycol-catalase (PEG-CAT, a scavenger of H(2)O(2)) or KN93, an inhibitor of CaMKII, abolished this response. OSS activated CaMKII in an H(2)O(2)-dependent fashion whereas unidirectional laminar shear stress (LSS) inhibited CaMKII phosphorylation. Inhibition of c-Src (essential for LSS upregulation of eNOS) had no effect on OSS upregulation of eNOS. Additionally, OSS stimulated NO* production acutely. Scavenging of H(2)O(2) by PEG-CAT attenuated OSS stimulation of NO* by 50% whereas it had no effect on LSS regulation of NO* production. These data suggest that intracellular H(2)O(2) and CaMKII mediate OSS upregulation of eNOS. The acute activation of eNOS by OSS also partially requires H(2)O(2). As OSS has been shown previously to stimulate sustained production of superoxide (O(2)*-) which would inactivate NO*, these responses may represent attempted compensation to restore NO* bioavailability in areas exposed to OSS. Simultaneous stimulation of O(2)*- and NO* by this mechanism, however, could facilitate peroxynitrite formation and protein nitration, which may enhance atherosclerotic lesion formation. Both OSS and LSS upregulate eNOS expression but via different signaling mechanisms.

Ca2+/calmodulin-dependent protein kinase II in the rat cranial sensory ganglia

Immunohistochemistry for Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) was performed on the rat cranial sensory ganglia. More than one half of neurons was immunoreactive for the enzyme in the trigeminal (60%), jugular (70%), petrosal (55%) and nodose ganglia (63%). These neurons were mainly small to medium-sized. The co-expression study demonstrated that one half of CaMKII-immunoreactive (ir) neurons was also immunoreactive for calcitonin gene-related peptide (CGRP) or the vanilloid receptor subtype 1 (VR1) in the trigeminal, jugular and petrosal ganglia. In the nodose ganglion, CaMKII-ir neurons were mostly devoid of CGRP-immunoreactivity (ir) (8.2%) whereas the co-expression with VR1-ir was common among such neurons (72%). In the facial skin, nasal mucosa and palate, the epithelium and taste bud were innervated by CaMKII-ir nerve fibers. In addition, the retrograde tracing study demonstrated that 39.6% and 44.8% of trigeminal neurons which were retrogradely traced with fluorogold from the facial skin and nasal mucosa exhibited CaMKII-ir. Forty-six percent of petrosal neurons which innervated the soft palate were immunoreactive for the enzyme.

Formalin-induced spinal cord calcium/calmodulin-dependent protein kinase II alpha expression is modulated by heme oxygenase in mice

The injection of formalin into the hindpaws of rats and mice is widely used as a model of inflammatory pain. The allodynia observed in this model is due in part to sensitization of spinal cord dorsal horn neurons, a form of neuroplasticity similar to long-term potentiation in the hippocampus. Ca(2+)/calmodulin-dependent kinase type IIalpha (CaMKIIalpha) is a key component of long-term potentiation. Here we report alterations in CaMKIIalpha mRNA and protein expression in spinal cord tissue from wild-type and heme oxygenase type 2 (HO-2) null mutant mice after formalin injection. Behavioral experiments demonstrated a long lived allodynia in wild-type C57Bl/6J mice after hindpaw formalin injection, but less in null mutant mice. Both CaMKIIalpha mRNA and protein expression were increased in a time-dependent manner in the spinal cords of wild-type mice after formalin injection. Confocal microscopy localized the increased expression to the superficial laminae of the spinal cord dorsal horn. In the HO-2 null mutant mice no significant change in CaMKIIalpha mRNA expression and only a small increase in protein were noted. These findings suggest that time-dependent CaMKIIalpha expression may underlie central sensitization and allodynia induced by hindpaw formalin injection, and that this process is modulated by HO-2.

Diurnal, circadian and photic regulation of calcium/calmodulin-dependent kinase II and neuronal nitric oxide synthase in the hamster suprachiasmatic nuclei

Mammalian circadian rhythms are entrained by light pulses that induce phosphorylation events in the suprachiasmatic nuclei (SCN). Ca(2+)-dependent enzymes are known to be involved in circadian phase shifting. In this paper, we show that calcium/calmodulin-dependent kinase II (CaMKII) is rhythmically phosphorylated in the SCN both under entrained and free-running (constant dark) conditions while neuronal nitric oxide synthase (nNOS) is rhythmically phosphorylated in the SCN only under entrained conditions. Both p-CaMKII and p-NOS (specifically phosphorylated by CaMKII) levels peak during the day or subjective day. Light pulses administered during the subjective night, but not during the day, induced rapid phosphorylation of both enzymes. Moreover, we found an inhibitory effect of KN-62 and KN-93, both CaMKII inhibitors, on light-induced nNOS activity and nNOS phosphorylation respectively, suggesting a direct pathway between both enzymes which is at least partially responsible of photic circadian entrainment.

Overexpression of type-1 adenylyl cyclase in mouse forebrain enhances recognition memory and LTP

Cyclic AMP is a positive regulator of synaptic plasticity and is required for several forms of hippocampus-dependent memory including recognition memory. The type I adenylyl cyclase, Adcy1 (also known as AC1), is crucial in memory formation because it couples Ca(2+) to cyclic AMP increases in the hippocampus. Because Adcy1 is neurospecific, it is a potential pharmacological target for increasing cAMP specifically in the brain and for improving memory. We have generated transgenic mice that overexpress Adcy1 in the forebrain using the Camk2a (also known as alpha-CaMKII) promoter. These mice showed elevated long-term potentiation (LTP), increased memory for object recognition and slower rates of extinction for contextual memory. The increase in recognition memory and lower rates of contextual memory extinction may be due to enhanced extracellular signal-related kinase (ERK)/mitogen-activated protein kinase (MAPK) signaling, which is elevated in mice that overexpress Adcy1.

Death-Associated Protein Kinase Loss of Expression Is a New Marker for Breast Cancer Prognosis

PURPOSE

Death-associated protein (DAP)-kinase is a new Ser/Thr kinase involved in cell apoptosis and tumor suppression, the expression of which has been correlated to invasive potential and metastasis in several human neoplastic tissues. We analyzed the level of DAP-kinase expression in breast cancer specimens and its correlation with survival.

EXPERIMENTAL DESIGN

One hundred twenty-eight breast cancer specimens were analyzed by immunohistochemistry. Patient records were studied retrospectively for demographic characteristics, clinical data, hormonal treatment, outcome, and survival. DAP-kinase protein expression was also studied in normal breast cells primary cultures under estrogen and antiestrogen treatment.

RESULTS

Among the 128 patients, 30 showed a DAP-kinase staining < or = 20%, whereas 98 had a staining over 20%. Mean follow-up time was 62 months. The association between tumor Scarff-Bloom and Richardson grade (P = 0.009), estrogen receptor and progesterone receptor expression (P = 0.002 and 0.001, respectively), tumor size (P = 0.05), Bcl-2 expression (P = 0.004), and DAP-kinase immunostaining in the ductal carcinoma group was highly significant. Overall (64 months) and disease-free (63 months) survival in the high DAP-kinase expression group were significantly longer compared with the women whose tumors showed a loss of DAP-kinase expression (51 and 43 months, respectively). DAP-kinase protein was strongly expressed in normal breast tissue and in human breast epithelial cells primary cultures. Estradiol decreased DAP-kinase expression in these cells, arguing for hormonal regulation of the protein.

CONCLUSIONS

Loss of DAP-kinase expression negatively correlates to survival and positively correlates to the probability of recurrence in a very significant manner. DAP-kinase thus constitutes a novel and independent prognosis marker for breast cancer.

Cloning and Characterization of a Novel Ca2+/Calmodulin-Dependent Protein Kinase I Homologue in Xenopus laevis

In order to investigate protein kinases expressed in the different developmental stages of Xenopus laevis, recently developed expression cloning was carried out. When two different expression libraries, Xenopus oocyte and Xenopus head (embryonic stage 28/30) cDNA libraries, were screened by kinase-specific monoclonal antibodies, cDNA clones for various known and novel protein serine/threonine kinases (Ser/Thr kinases) were isolated. In addition to well-characterized Ser/Thr kinases, one cDNA clone for a putative kinase was isolated from the Xenopus head library. The sequence of the open reading frame of the cDNA encoded a protein of 337 amino acid residues with a predicted molecular weight of 38,404. Since the deduced animo acid sequence of this protein was 75% identical to that of rat Ca(2+)/calmodulin-dependent protein kinase I (CaMKI), it was designated as CaMKIx. Although recombinant CaMKIx expressed in Escherichia coli showed no protein kinase activity against syntide-2, a synthetic peptide substrate, it was activated when phosphorylated by mouse Ca(2+)/calmodulin-dependent protein kinase kinase alpha (CaMKKalpha). Activated CaMKIx significantly phosphorylated various proteins including synapsin I, histones, and myelin basic protein. CaMKIx could not be detected in the early stages of embryogenesis, but was detected in late embryos of stages 37/38 and thereafter when examined by Western blotting using a specific antibody. This kinase was found to be highly expressed in adult brain and heart, and an upstream kinase that could activate CaMKIx was detected in these tissues. These results suggest that CaMKIx plays some critical role in the late stages of embryogenesis of Xenopus laevis.

NMDA receptor subunit and CaMKII changes in rat hippocampus induced by acute MDMA treatment: a mechanism for learning impairment

RATIONALE

Cognitive deficits have been reported in recreational 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") users. In rats and other animal species, acute MDMA administration produces an impairment in passive avoidance and other learning tasks. Different studies have shown that this learning deficit is not strictly related to the pronounced serotonin (5-HT) depletion induced by the drug.

OBJECTIVES

This study was aimed at determining if acute MDMA administration induces in the rat hippocampus early molecular changes related to memory impairment in a passive avoidance task. The membrane expression of key molecules in memory consolidation, such as the NR1 and NR2B subunits of the N-methyl-D-aspartate (NMDA) receptor, Ca2+/calmodulin-dependent protein kinase II (CaMKII) and protein phosphatase 1 (PP1) was measured. Some of these studies were also performed after 5-HT depletion induced by the 5-HT synthesis inhibitor p-chlorophenylalanine (PCPA).

METHODS

Neurochemical studies were performed in rats treated with MDMA and killed 90 min later and also in rats subjected to passive avoidance 30 min after MDMA treatment. Western blotting was used for measuring the levels of NMDA receptor subunits, CAMKII and PP1. Enzyme activity assays were also performed.

RESULTS

In hippocampal membrane extracts, passive avoidance training increased NMDA receptor NR1 subunit expression as well as CaMKII levels and phosphorylated CaMKII. In untrained rats, MDMA reduced NR1 and NR2B protein levels, membrane CaMKII levels and enzyme activity, and enhanced PP1 levels and activity. In trained rats, MDMA prevented the learning-specific increase in NR1 subunit expression and membrane CaMKII/pCaMKII levels. After pronounced 5-HT depletion by PCPA, MDMA impaired passive avoidance retention to a similar extent and also prevented the training-associated changes in NR1 levels and CaMKII activity.

CONCLUSIONS

Diminished function of hippocampal CaMKII and reduced levels of synaptic NMDA receptor subunits appear to be involved in the impairment of passive avoidance learning induced in rats by acute MDMA treatment.

Increased expression of Ca2+/calmodulin-dependent protein kinase II alpha during chronic morphine exposure

The chronic administration of morphine and related opioid drugs results in tolerance and dependence which limits the clinical utility of these agents. Neuronal plasticity is probably responsible in large part for tolerance and dependence. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) plays a crucial role in the neuroplastic events underlying memory formation and other phenomena. However, the role of this kinase in morphine tolerance remains unclear. To clarify this issue we explored mRNA and protein expression of CaMKIIalpha in spinal cord tissue from control and morphine treated mice using real-time polymerase chain reaction, Western blot analysis and confocal microscopy. Our chronic exposure paradigm involved the subcutaneous implantation of morphine pellets for 6 days prior to tissue analysis. The results indicate that the levels of CaMKIIalpha mRNA and protein were robustly increased in spinal cord tissue from morphine-treated mice. Confocal microscopy demonstrated that the increase in CaMKIIalpha expression was primarily localized to superficial laminae of the dorsal horn. In addition, the abundance of phosphorylated CaMKIIalpha was increased in spinal cord tissue from morphine-treated mice. We conclude that enhanced CaMKIIalpha expression and activity in spinal cord tissue may contribute to the development of morphine tolerance in mice. The involvement of this enzyme in opioid tolerance suggests other parallels may exist between the neuroplastic events related to memory formation and those related to opioid tolerance or pain.

Effects of PU.1-induced mouse calcium–calmodulin-dependent kinase I-like kinase (CKLiK) on apoptosis of murine erythroleukemia cells

PU.1, a hematopoietic cell-specific Ets family transcription factor, is involved in the generation of murine erythroleukemia (MEL). To identify the target gene(s) of PU.1 in MEL cells, we carried out differential display (DD) analysis and isolated a novel gene whose expression was up-regulated after overexpression of PU.1 in MEL cells. Because the gene exhibited about 90% homology with the human calcium-calmodulin-dependent kinase I-like kinase (CKLiK) gene, it was identified as a mouse homologue of human CKLiK. The mCKLiK gene was mapped to the mouse chromosome 2A1-A3 region and shown to be expressed predominantly in T cells lymphoma and embryonal carcinoma cell lines and primary thymus and brain. Two types of transcripts were present showing a difference in the 3' portion of the coding region and CREB-activating ability. Overexpression of each isoform of mCKLiK in MEL cells revealed that one of them induces, while the other inhibits apoptosis under low serum condition. Differentiation inhibition and lineage switch to myelomonocytes, which were previously observed in MEL cells overexpressing PU.1, were not provoked in the cells overexpressing mCKLiK. These results suggest that mCKLiK is up-regulated by PU.1 in MEL cells and involved in apoptosis of the cells.

Reduced expression of death-associated protein kinase in human uterine and ovarian carcinoma cells

The expression of the death-associated protein kinase (DAPK) protein and promoter methylation in 11 human uterine and ovarian carcinoma cell lines originally established from histopathologically-different carcinoma tissues were examined to investigate the relationship between DAPK and carcinogenesis in female reproductive tissues. The 11 cell lines included three cervical carcinomas, three endometrial carcinomas and five ovarian carcinomas. Western blot analysis showed no detectable expression of DAPK protein in 4 cell lines (ME180, HOKUG, MCAS and OVK-18) while moderate levels of DAPK protein were readily detected in normal human endometrium, and normal murine uterus and ovary. Methylation-specific PCR of the 11 cell lines revealed that 5 carcinoma cell lines (ME180, HOKUG, MCAS, OVK-18 and HEC-1) expressed hypermethylated promoters in the DAPK genes, while DAPK promoters in the other 6 carcinoma cell lines remained unmethylated. These results indicate that DAPK protein expression is reduced or silenced in some human uterine and ovarian carcinoma cells by methylation of the DAPK gene promoter region. Therefore, reduced DAPK expression and methylation of the DAPK promoter may be involved in carcinogenesis of human uterine and ovarian tissues.