cDNA sequence and differential expression of the mouse Ca2+/calmodulin-dependent protein kinase IV gene

A testis-specific gene within a widely expressed gene: Contrasting evolutionary patterns of two differentially expressed mammalian proteins encoded by a single gene, CAMK4

Understanding the patterns of genetic variations within fertility-related genes and the evolutionary forces that shape such variations is crucial in predicting the fitness landscapes of subsequent generations. This study reports distinct evolutionary features of two differentially expressed mammalian proteins [CaMKIV (Ca(2+) /calmodulin-dependent protein kinase IV) and CaS (calspermin)] that are encoded by a single gene, CAMK4. The multifunctional CaMKIV, which is expressed in multiple tissues including testis and ovary, is evolving at a relatively low rate (0.46-0.64 × 10(-9) nucleotide substitutions/site/year), whereas the testis-specific CaS gene, which is predominantly expressed in post-meiotic cells, evolves at least three to four times faster (1.48-1.98 × 10(-9) substitutions/site/year). Concomitantly, maximum-likelihood-based selection analyses revealed that the ubiquitously expressed CaMKIV is constrained by intense purifying selection and, therefore, remained functionally highly conserved throughout the mammalian evolution, whereas the testis-specific CaS gene is under strong positive selection. The substitution rates of different mammalian lineages within both genes are positively correlated with GC content, indicating the possible influence of GC-biased gene conversion on the estimated substitution rates. The observation of such unusually high GC content of the CaS gene (≈74%), particularly in the lineage that comprises the bovine species, suggests the possible role of GC-biased gene conversion in the evolution of CaS that mimics positive selection.

Nicotine reward and affective nicotine withdrawal signs are attenuated in calcium/calmodulin-dependent protein kinase IV knockout mice

The influx of Ca(2+) through calcium-permeable nicotinic acetylcholine receptors (nAChRs) leads to activation of various downstream processes that may be relevant to nicotine-mediated behaviors. The calcium activated protein, calcium/calmodulin-dependent protein kinase IV (CaMKIV) phosphorylates the downstream transcription factor cyclic AMP response element binding protein (CREB), which mediates nicotine responses; however the role of CaMKIV in nicotine dependence is unknown. Given the proposed role of CaMKIV in CREB activation, we hypothesized that CaMKIV might be a crucial molecular component in the development of nicotine dependence. Using male CaMKIV genetically modified mice, we found that nicotine reward is attenuated in CaMKIV knockout (-/-) mice, but cocaine reward is enhanced in these mice. CaMKIV protein levels were also increased in the nucleus accumbens of C57Bl/6 mice after nicotine reward. In a nicotine withdrawal assessment, anxiety-related behavior, but not somatic signs or the hyperalgesia response are attenuated in CaMKIV -/- mice. To complement our animal studies, we also conducted a human genetic association analysis and found that variants in the CaMKIV gene are associated with a protective effect against nicotine dependence. Taken together, our results support an important role for CaMKIV in nicotine reward, and suggest that CaMKIV has opposing roles in nicotine and cocaine reward. Further, CaMKIV mediates affective, but not physical nicotine withdrawal signs, and has a protective effect against nicotine dependence in human genetic association studies. These findings further indicate the importance of calcium-dependent mechanisms in mediating behaviors associated with drugs of abuse.

Calcium/calmodulin and cAMP/protein kinase-A pathways regulate sperm motility in the stallion

In spite of the importance of sperm motility to fertility in the stallion, little is known about the signaling pathways that regulate motility in this species. In other mammals, calcium/calmodulin signaling and the cyclic AMP/protein kinase-A pathway are involved in sperm motility regulation. We hypothesized that these pathways also were involved in the regulation of sperm motility in the stallion. Using immunoblotting, calmodulin and the calmodulin-dependent protein kinase II β were shown to be present in stallion sperm and with indirect immunofluorescence calmodulin was localized to the acrosome and flagellar principal piece. Additionally, inhibition of either calmodulin or protein kinase-A significantly reduced sperm motility without affecting viability. Following inhibition of calmodulin, motility was not restored with agonists of the cyclic AMP/protein kinase-A pathway. These data suggest that calcium/calmodulin and cyclic AMP/protein kinase-A pathways are involved in the regulation of stallion sperm motility. The failure of cyclic AMP/protein kinase-A agonists to restore motility of calmodulin inhibited sperm suggests that both pathways may be required to support normal motility.

Loss of the Ca2+/calmodulin-dependent protein kinase type IV in dopaminoceptive neurons enhances behavioral effects of cocaine

The persistent nature of addiction has been associated with activity-induced plasticity of neurons within the striatum and nucleus accumbens (NAc). To identify the molecular processes leading to these adaptations, we performed Cre/loxP-mediated genetic ablations of two key regulators of gene expression in response to activity, the Ca(2+)/calmodulin-dependent protein kinase IV (CaMKIV) and its postulated main target, the cAMP-responsive element binding protein (CREB). We found that acute cocaine-induced gene expression in the striatum was largely unaffected by the loss of CaMKIV. On the behavioral level, mice lacking CaMKIV in dopaminoceptive neurons displayed increased sensitivity to cocaine as evidenced by augmented expression of locomotor sensitization and enhanced conditioned place preference and reinstatement after extinction. However, the loss of CREB in the forebrain had no effect on either of these behaviors, even though it robustly blunted acute cocaine-induced transcription. To test the relevance of these observations for addiction in humans, we performed an association study of CAMK4 and CREB promoter polymorphisms with cocaine addiction in a large sample of addicts. We found that a single nucleotide polymorphism in the CAMK4 promoter was significantly associated with cocaine addiction, whereas variations in the CREB promoter regions did not correlate with drug abuse. These findings reveal a critical role for CaMKIV in the development and persistence of cocaine-induced behaviors, through mechanisms dissociated from acute effects on gene expression and CREB-dependent transcription.

Mechanisms of injury to the newborn brain

Preterm and ill term infants are at risk for brain injury and subsequent neurodevelopmental delay as a result of many perinatal factors. Outlined in this article are the basic science mechanisms by which hypoxia, hypocapnia, and hypercapnia may result in neuronal injury in the newborn brain.

Monocular enucleation induces nuclear localization of calcium/calmodulin-dependent protein kinase IV in cortical interneurons of adult monkey area V1

Elevation of intracellular Ca2+ levels activates calcium/calmodulin-dependent protein kinase (CaMK) IV, which in turn plays an important role in neuroprotection and neuroplasticity. The possibility that CaMKIV is similarly involved in neocortical tissue has not been examined previously, especially with regard to the plastic nature of ocular dominance features in the primary visual cortex (area V1). We addressed this question by way of monocular enucleation (ME) to disrupt sensory input and examine CaMKIV expression changes in monkey area V1. Immunohistochemical staining of area V1 in normal infants showed a nuclear presence of CaMKIV, which did not changed after ME. However, a striking set of layer- and time-dependent changes in nuclear CaMKIV expression was observed in adult area V1 after ME. A strong increase in nuclear CaMKIV levels was evident in cortical layers II/III and VI after 1 d of ME and in layer IVC after 5 d of ME. These specific laminar changes persisted after 30 d of ME and, most notably, showed a columnar profile in which CaMKIV expression was linked to open-eye columns. Real-time quantitative reverse transcription-PCR and Western blot analysis showed that total amounts of CaMKIV mRNA and protein remained unchanged after ME, suggesting that a nuclear translocation may occur from the cytoplasm. Finally, double-label immunohistochemical staining with a pyramidal cell marker (SMI-32) showed that CaMKIV was absent in this subtype, whereas coincidental expression with GABA, parvalbumin, and calretinin, but not calbindin, showed its clear presence in a subset of interneurons. We propose that CaMKIV activity within diverse groups of cortical interneurons may play an important role in adaptive plastic reorganization of adult neocortical tissue.

A complex deoxyribonucleic acid response element in the rat Ca(2+)/calmodulin-dependent protein kinase IV gene 5'-flanking region mediates thyroid hormone induction and chicken ovalbumin upstream promoter transcription factor 1 repression

Ca(2+)/calmodulin-dependent protein kinase IV (CaMKIV) is regulated by T(3) in a time- and concentration-dependent manner in the developing rat brain and plays an important role in neuronal-specific gene regulation. T(3) treatment, but not retinoic acid (RA), stimulated endogenous CaMKIV mRNA 5-fold in mouse embryonic stem (ES) cells differentiated into neurons. We localized a region -750 to -700 in the CaMKIV gene 5'-flanking region that conferred T(3) responsiveness and bound thyroid hormone receptor (TR), retinoic acid receptor (RAR), and chicken ovalbumin upstream promoter-transcription factor 1 (COUP-TF1). T(3) and RA treatment stimulated the CaMKIV hormone response element. Cotransfection of a COUP-TF1 expression vector repressed the T(3) response and augmented the RA response. Mutational analysis identified three half-sites arranged in a direct repeat (AB) and overlapping inverted repeat (BC), required for functional induction and receptor binding. TR and RAR bound predominantly to the BC portion of the element and COUP-TF1 to the AB region, with a close correlation of binding and functional studies. COUP-TF1 binding did not influence TR/retinoid X receptor binding but modestly augmented RAR/retinoid X receptor binding. A single element confers T(3) and COUP-TF1 regulation of CaMKIV expression.

A targeted thyroid hormone receptor alpha gene dominant-negative mutation (P398H) selectively impairs gene expression in differentiated embryonic stem cells

Thyroid hormone and retinoic acid (RA) are essential for normal neural development in vivo, yet all in vitro differentiation strategies of embryonic stem (ES) cells use only RA. We developed a novel differentiation strategy of mouse ES cells using T(3). A dominant-negative knock-in point mutation (P398H) was introduced into the thyroid hormone receptor alpha gene to determine the influence of T(3) on ES cell differentiation. Differentiation promoted by T(3) (1 nM), RA (1 microM), or combined T(3)/RA was assessed in wild-type (wt) and mutant (m) ES cells on the basis of neuronal-specific gene expression and cell cycle. T(3) alone stimulated neural differentiation in a similar fashion as that seen with RA in both wtES and mES cells. Expression of neurogranin and Ca(2+)/calmodulin-dependent kinase IV mRNA (identified in vivo as T(3)-regulated genes), however, was markedly reduced in mES, compared with wtES cells. RA treatment enhanced apoptosis, significantly greater than that seen with T(3) stimulation. T(3) treatment given with RA significantly reduced the apoptotic effects of RA, an effect not seen in mES cells. T(3)-induced ES cell neural differentiation of thyroid hormone alpha mutant and wtES cells provides an in vitro model to study T(3)-dependent gene regulation in neural development. This system could also be used to identify novel T(3)-regulated genes. The modulation of the apoptotic effects of RA by T(3) may have implications for stem cell therapy.

Nitric oxide synthase sequences in the marine fish Stenotomus chrysops and the sea urchin Arbacia punctulata, and phylogenetic analysis of nitric oxide synthase calmodulin-binding domains

The phylogenetic distribution and structural diversity of the nitric oxide synthases (NOS) remain important and issues that are little understood. We present sequence information, as well as phylogenetic analysis, for three NOS cDNAs identified in two non-mammalian species: the vertebrate marine teleost fish Stenotomus chrysops (scup) and the invertebrate echinoderm Arbacia punctulata (sea urchin). Partial gene sequences containing the well-conserved calmodulin (CaM)-binding domain were amplified by RT-PCR. Identical 375-bp cDNAs were amplified from scup brain, heart, liver and spleen; this sequence shares 82% nucleic acid and 91% predicted amino acid identity with the corresponding region of human neuronal NOS. A 387-bp cDNA was amplified from sea urchin ovary and testes; this sequence shares 72% nucleic acid identity and 65% deduced amino acid identity with human neuronal NOS. A second cDNA of 381 bp was amplified from sea urchin ovary and it shares 66% nucleic acid and 57% deduced amino acid identity with the first sea urchin sequence. Together with earlier reports of neuronal and inducible NOS sequences in fish, these data indicate that multiple NOS isoforms exist in non-mammalian species. Phylogenetic analysis of these sequences confirms the conserved nature of NOS, particularly of the calmodulin-binding domains.

CaMKIV/Gr is dispensable for spermatogenesis and CREM-regulated transcription in male germ cells

The calcium/calmodulin-dependent protein kinase type IV/Gr (CaMKIV/Gr) is expressed in male germ cells and spermatids and has been implicated in controlling the differentiation of germ cells into mature spermatozoa. The function of CaMKIV/Gr in spermatogenesis was investigated using CaMKIV/Gr-deficient mice generated by targeted gene disruption. CaMKIV/Gr-deficient males exhibited normal spermatogenesis, and their fertility was similar to that of wild-type littermates. Notwithstanding the function of CaMKIV/Gr as an activator of cAMP response element (CRE)-dependent transcription, mRNA levels of several testis-specific CRE modulator (CREM)-regulated genes were unaltered. These results indicate that CaMKIV/Gr is not essential for spermatogenesis or for CRE-regulated gene transcription in the testis.

Calcium-stimulated autophosphorylation site of plant chimeric calcium/calmodulin-dependent protein kinase

The existence of two molecular switches regulating plant chimeric Ca(2+)/calmodulin-dependent protein kinase (CCaMK), namely the C-terminal visinin-like domain acting as Ca(2+)-sensitive molecular switch and calmodulin binding domain acting as Ca(2+)-stimulated autophosphorylation-sensitive molecular switch, has been described (Sathyanarayanan, P. V., Cremo, C. R., and Poovaiah, B. W. (2000) J. Biol. Chem. 275, 30417-30422). Here we report the identification of Ca(2+)-stimulated autophosphorylation site of CCaMK by matrix-assisted laser desorption ionization time of flight-mass spectrometry. Thr(267) was confirmed as the Ca(2+)-stimulated autophosphorylation site by post-source decay experiments and by site-directed mutagenesis. The purified T267A mutant form of CCaMK did not show Ca(2+)-stimulated autophosphorylation, autophosphorylation-dependent variable calmodulin affinity, or Ca(2+)/calmodulin stimulation of kinase activity. Sequence comparison of CCaMK from monocotyledonous plant (lily) and dicotyledonous plant (tobacco) suggests that the autophosphorylation site is conserved. This is the first identification of a phosphorylation site specifically responding to activation by second messenger system (Ca(2+) messenger system) in plants. Homology modeling of the kinase and calmodulin binding domain of CCaMK with the crystal structure of calcium/calmodulin-dependent protein kinase 1 suggests that the Ca(2+)-stimulated autophosphorylation site is located on the surface of the kinase and far from the catalytic site. Analysis of Ca(2+)-stimulated autophosphorylation with increasing concentration of CCaMK indicates the possibility that the Ca(2+)-stimulated phosphorylation occurs by an intermolecular mechanism.

Impaired synaptic plasticity and cAMP response element-binding protein activation in Ca2+/calmodulin-dependent protein kinase type IV/Gr-deficient mice

The Ca(2+)/calmodulin-dependent protein kinase type IV/Gr (CaMKIV/Gr) is a key effector of neuronal Ca(2+) signaling; its function was analyzed by targeted gene disruption in mice. CaMKIV/Gr-deficient mice exhibited impaired neuronal cAMP-responsive element binding protein (CREB) phosphorylation and Ca(2+)/CREB-dependent gene expression. They were also deficient in two forms of synaptic plasticity: long-term potentiation (LTP) in hippocampal CA1 neurons and a late phase of long-term depression in cerebellar Purkinje neurons. However, despite impaired LTP and CREB activation, CaMKIV/Gr-deficient mice exhibited no obvious deficits in spatial learning and memory. These results support an important role for CaMKIV/Gr in Ca(2+)-regulated neuronal gene transcription and synaptic plasticity and suggest that the contribution of other signaling pathways may spare spatial memory of CaMKIV/Gr-deficient mice.

Cloning of a calmodulin kinase I homologue from Schizosaccharomyces pombe

By using (35)S-labeled calmodulin (CaM), we have isolated a full-length cDNA clone expressing the Schizosaccharomyces pombe homologue of calmodulin kinase I (CaMK-I), a gene we have named cmk1. It has been previously been shown in mammals that CaMK-I is a member of a CaM-dependent protein kinase cascade that ultimately regulates transcription factors such as ATF and cAMP-response element-binding protein. The cmk1 cDNA encodes a 335-amino acid protein with significant homology to mammalian CaMK-I, including a conserved sequence for phosphorylation by CaM kinase kinase. We have expressed the cmk1 cDNA in bacteria and yeast, and we have shown that it is a CaM-dependent protein kinase. A truncation mutant of cmk1 (d320) failed to bind CaM, indicating that the CaM-binding domain is at the extreme C terminus of the protein. The mRNA for cmk1 is expressed in a cell cycle-dependent manner, peaking at or near the G(1)/S boundary. Overexpression of wild-type cmk1 in S. pombe caused no apparent effects on growth and division. However, mutation of a predicted regulatory site (Thr-192) to aspartic acid resulted in hyperactivation of CMK1 activity in the presence of CaM and causes cell cycle arrest in vivo. Arrest is also accompanied by morphological defects. These results suggest the presence of a CaM-dependent protein kinase cascade in yeast and indicate that cmk1 may be important in cell cycle progression, a process known to be dependent on CaM in eukaryotic cells.

Calmodulin-dependent protein kinase IV: regulation of function and expression

Calmodulin-dependent protein kinase IV (CaMKIV) is a key mediator of Ca2+-induced gene expression. This serine/threonine kinase is itself activated by a calmodulin kinase kinase. In the present contribution the gene structure, regulation of activity, the role in Ca2+-dependent gene expression, and the hormonal induction and controlled expression of CaMKIV during tissue development are reviewed.

Calcium/calmodulin-dependent protein kinase IV is cleaved by caspase-3 and calpain in SH-SY5Y human neuroblastoma cells undergoing apoptosis

We have previously demonstrated cleavage of alpha-spectrin by caspase-3 and calpain during apoptosis in SH-SY5Y neuroblastoma cells (Nath, R., Raser, K. J., Stafford, D., Hajimohammadreza, I., Posner, A., Allen, H., Talanian, R. V., Yuen, P., Gilbertsen, R. B., and Wang, K. K. (1996) Biochem. J. 319, 683-690). We demonstrate here that calcium/calmodulin-dependent protein kinase IV (CaMK IV) is cleaved during apoptosis by caspase-3 and calpain. We challenged SH-SY5Y cells with the pro-apoptotic agent thapsigargin. Western blot analysis revealed major CaMK IV breakdown products of 40, 38, and 33 kDa. Digestion of control SH-SY5Y lysate with purified caspase-3 produced a 38-kDa CaMK IV fragment; digestion with purified calpain produced a major fragment of 40 kDa. Pretreatment with carbobenzoxy-Asp-CH2OC(O)-2,6-dichlorobenzene or Z-Val-Ala-Asp-fluoromethylketone was able to block the caspase-3-mediated production of the 38-kDa fragment both in situ and in vitro. Calpain inhibitor II similarly blocked formation of the calpain-mediated 40-kDa fragment both in situ and in vitro. Digestion of recombinant CaMK IV by other caspase family members revealed that only caspase-3 produces a fragmentation pattern consistent to that seen in situ. The major caspase-3 and calpain cleavage sites are respectively identified as PAPD176*A and CG201*A, both within the CaMK IV catalytic domain. Furthermore, calmodulin-stimulated protein kinase activity decreases within 6 h in thapsigargin-treated SH-SY5Y. The loss of activity precedes cell death.

Characterization of a calmodulin-binding transporter from the plasma membrane of barley aleurone

We have used Arabidopsis calmodulin (CaM) covalently coupled to horseradish peroxidase to screen a barley aleurone cDNA expression library for CaM binding proteins. The deduced amino acid sequence of one cDNA obtained by this screen was shown to be a unique protein of 702 amino acids with CaM and cyclic nucleotide binding domains at the carboxyl terminus and high similarity to olfactory and K+ channels. This cDNA was designated HvCBT1 (Hordeum vulgare CaM binding transporter). Hydropathy plots of HvCBT1 showed the presence of six putative transmembrane domains, but sequence alignment indicated a pore domain that was unlike the consensus domains in K+ and olfactory channels. Expression of a subclone of amino acids 482-702 in Escherichia coli generated a peptide that bound CaM. When a fusion protein of HvCBT1 and green fluorescent protein was expressed in barley aleurone protoplasts, fluorescence accumulated in the plasma membrane. Expression of HvCBT1 in the K+ transport deficient Saccharomyces cerevisiae mutant CY162 showed no rescue of the mutant phenotype. However, growth of CY162 expressing HvCBT1 with its pore mutated to GYGD, the consensus sequence of K+ channels, was compromised. We interpret these data as indicating that HvCBT1 acts to interfere with ion transport.

The Ca2+/calmodulin-dependent kinase type IV is involved in the CD5-mediated signaling pathway in human T lymphocytes

The CD5 receptor on T lymphocytes is involved in T cell activation and T-B cell interactions. In the present study, we have characterized the signaling pathways induced by anti-CD5 stimulation in human T lymphocytes. In T lymphocytes, anti-CD5 co-stimulation enhances the phytohemagglutinin/anti-CD28-induced interleukin-2 (IL-2) mRNA accumulation 1.6-fold and IL-2 protein secretion 2. 2-fold, whereby the up-regulation is mediated at both the transcriptional and post-transcriptional level. The CD5 signaling pathway up-regulates the IL-2 gene expression by increasing the DNA binding and transactivation activity of activator protein 1 but affects none of the other transcription factors like nuclear factor of activated T cells, nuclear factor kappaB, Oct, and CD28-responsive complex/nuclear factor of mitogen-activated T cells involved in the regulation of the IL-2 promoter activity. The CD5-induced increase of the activator protein 1 activity is mediated through the activation of calcium/calmodulin-dependent (CaM) kinase type IV, and is independent of the activation of mitogen-activated protein kinases Jun N-terminal kinase, extracellular signal-regulated kinase, and p38/Mpk2, and calcium/calmodul-independent kinase type II. The expression of a dominant negative mutant of CaM kinase IV in T lymphocytes transfected with an IL-2 promoter-driven reporter construct completely abrogates the response to CD5 stimulation, indicating that CaM kinase IV is essential to the CD5 signaling pathway. In addition, it is demonstrated that calcium/calmodulin-dependent kinase type IV is also involved in the stabilization of the IL-2 transcripts, which is observed after co-stimulation of phytohemagglutinin/anti-CD28 activated T lymphocytes with anti-CD5.

Reticalmin: a novel calcium/calmodulin-dependent protein kinase IV-like protein in rat retina

Western blot analysis of 100,000 g supernatant of rat retina using a polyclonal anti-Ca2+/ calmodulin-dependent protein kinase IV (CaM-kinase IV) antibody revealed an immunoreactive mass of 35 kDa, termed reticalmin. Lower amount of a isoform of CaM-kinase IV was also expressed in rat retina. Reticalmin did not react with anti-CaM-kinase IV C-terminal peptide antibody which recognized alpha and beta isoforms of CaM-kinase IV and calspermin. Immunohistochemically reticalmin was shown to be localized mainly in the outer segment of photo-receptor cells, and in dendrites of inner plexiform layers and may be in nuclei of ganglion cells and some inner nuclear layer cells.

Inhibition of M3 muscarinic acetylcholine receptor-mediated Ca2+ influx and intracellular Ca2+ mobilization in neuroblastoma cells by the Ca2+/calmodulin-dependent protein kinase inhibitor 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-trosyl]-4-phenylpiperazin e (KN-62)

The role of Ca2+/calmodulin-dependent protein kinase (CaM kinase; EC 2.7.1.123) in the generation of Ca2+ signals by muscarinic acetylcholine receptors (mAChR) was studied. Changes in intracellular Ca2+ concentrations ([Ca2+]i) induced by mAChR activation were monitored in SK-N-SH human neuroblastoma cells using the dye Fura-2. SK-N-SH cells express M3 mAChR, as well as CaM kinase types II and IV, which are specifically inhibited by the CaM kinase antagonist KN-62 (1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazi ne). Carbamylcholine (100 microM) elicited an initial transient peak in [Ca2+]i due to mobilization of Ca2+ from internal stores, followed by a sustained elevation in [Ca2+]i that depended on the influx of extracellular Ca2+ and which was inhibited by EGTA and Ni2+. These mAChR-induced Ca2+ signals were diminished to an equal extent by preincubating the cells with 0.01 to 100 microM KN-62. KN-62 inhibited mAChR-induced Ca2+ influx and mobilization from internal stores by about 25-30%, producing a half-maximal effect at approximately 1 microM. In contrast, KN-62 (25 microM) almost completely abolished carbamylcholine-stimulated entry of divalent cations through Mn2+-permeant channels, as revealed by Mn2+ quenching of Fura-2 fluorescence. KN-62 also almost completely abolished Ca2+ influx induced by depolarization of the cells with 25 mM K+ (IC50 = 3 microM). These results suggest that CaM kinases regulate both the mobilization of intracellular Ca2+ and the stimulation of Ca2+ influx that are induced by mAChR activation, and indicate that the mAChR-induced influx of Ca2+ occurs through Ca2+ channels other than, or in addition to, the voltage-gated calcium channels or Mn2+-permeant channels which are inhibited by KN-62.

Calmodulin kinase IV: expression and function during rat brain development

The expression of calmodulin kinase IV (CaMKIV) can be induced by the thyroid hormone T3 in a time- and concentration-dependent manner at a very early stage of brain differentiation using a fetal rat telencephalon primary cell culture system which can grow and differentiate under chemically defined conditions (Krebs et al. (1996) J. Biol. Chem. 271, 11055-11058). After the induction of CaMKIV by T3 we examined the influence of prolonged absence of T3 from the culture medium on the expression of CaMKIV. We could demonstrate that after the T3-dependent induction of CaMKIV, omission of the hormone, even for 8 days, from the medium did not downregulate the expression of CaMKIV indicating that different regulatory mechanisms became important for the expression of the enzyme. We further showed that CaMKIV could be involved in the Ca(2+) -dependent expression of the immediate early gene c-fos, probably via phosphorylation of the transcription factor CREB. Convergence of signal transduction pathways on this transcription factor by using different protein kinases may explain the importance of CREB for the regulation of different cellular processes.

A unique phosphorylation-dependent mechanism for the activation of Ca2+/calmodulin-dependent protein kinase type IV/GR

The activity of the Ca2+/calmodulin-dependent protein kinase IV/Gr (CaMKIV/Gr) is shown to be strictly regulated by phosphorylation of three residues both in vitro and in response to antigen receptor-mediated signaling in lymphocytes. One residue, Thr-200, is indispensable for enhancement of Ca2+/calmodulin-dependent basal activity by CaMKIV/Gr kinase. This event requires Ca2+/calmodulin in the full-length CaMKIV/Gr but is Ca2+/calmodulin-independent when a truncated version of CaMKIV/Gr is used as a substrate (DeltaCaMKIV/Gr1-317 (Delta1-317)). The other two residues, Ser12 and Ser13, are apparently autophosphorylated by the Ca2+/calmodulin-bound CaMKIV/Gr. Phosphorylation of neither Ser12-Ser13 nor Thr312 (the residue in a homologous position to Thr286 of CaMKIIalpha influences the development of Ca2+/calmodulin-independent activity or any other property of CaMKIV/Gr examined. Similarly, removal of the NH2-terminal 20 amino acids has no effect on the activation or function of CaMKIV/Gr. However, mutation of both Ser12 and Ser13 residues to Ala in Delta1-317 completely abrogates activity, while individual substitutions have no effect. These results indicate that the NH2-terminal Ser cluster mediates a novel type of intrasteric inhibition and suggest that three events are required for CaMKIV/Gr activation: 1) Ca2+/calmodulin binding; 2) phosphorylation of the Ca2+/calmodulin-bound enzyme on Thr200 by a Ca2+/calmodulin-dependent protein kinase kinase; and 3) autophosphorylation of Ser12-Ser13. This three-step requirement is unique among the multifunctional Ca2+/calmodulin-dependent kinases.

Activation protein 1-dependent transcriptional activation of interleukin 2 gene by Ca2+/calmodulin kinase type IV/Gr

The Ca2+/calmodulin-dependent protein kinase (CaMK) type IV/Gr is selectively expressed in T lymphocytes and is activated after signaling via the T cell antigen receptor (TCR), indicating that it mediates some of the Ca(2+)-dependent transcriptional events that follow TCR engagement. Here we show that CaMKIV/Gr induces the transcription factor activation protein 1 (AP-1) alone or in synergy with T cell mitogens and with the p21ras oncoprotein. CaMKIV/ Gr signaling is associated with transcriptional activation of c-fos but is independent of p21ras or calcineurin. AP-1 is an integral component of the nuclear factor of activated T cells (NFAT) transcriptional complex, which is required for interleukin 2 gene expression in T cells. We demonstrate that CaMKIV/Gr reconstitutes the capacity of the cytosolic component of NFAT to direct transcription from NFAT sites in non-T cells. These results reveal a central role for CaMKIV/Gr as a Ca(2+)-regulated activator of gene transcription in T lymphocytes.

Induction of calmodulin kinase IV by the thyroid hormone during the development of rat brain

This communication reports the specific induction of calmodulin kinase IV by the thyroid hormone 3,3',5-triiodo-L-thyronine (T3) in a time- and concentration-dependent manner at a very early stage of brain differentiation using a fetal rat telencephalon primary cell culture system, which can grow and differentiate under chemically defined conditions. The induction of the enzyme that can be observed both on the mRNA and on the protein level is T3-specific, i.e. it cannot be induced by retinoic acid or reverse T3, and can be inhibited on both the transcriptional and the translational level by adding to the culture medium actinomycin D or cycloheximide, respectively. The earliest detection of calmodulin kinase IV in the fetal brain tissue of the rat is at days E16/E17, both on the mRNA as well as on the protein level. This is the first report in which a second messenger-dependent kinase involved in the control of cell regulatory processes is itself controlled by a primary messenger, the thyroid hormone.

Multiple Ca(2+)-calmodulin-dependent protein kinase kinases from rat brain. Purification, regulation by Ca(2+)-calmodulin, and partial amino acid sequence

We have purified to near homogeneity from rat brain two Ca(2+)-calmodulin-dependent protein kinase I (CaM kinase I) activating kinases, termed here CaM kinase I kinase-alpha and CaM kinase I kinase-beta (CaMKIK alpha and CaMKIK beta, respectively). Both CaMKIK alpha and CaMKIK beta are also capable of activating CaM kinase IV. Activation of CaM kinase I and CaM kinase IV occurs via phosphorylation of an equivalent Thr residue within the "activation loop" region of both kinases, Thr-177 and Thr-196, respectively. The activities of CaMKIK alpha and CaMKIK beta are themselves strongly stimulated by the presence of Ca(2+)-CaM, and both appear to be capable of Ca(2+)-CaM-dependent autophosphorylation. Automated microsequence analysis of the purified enzymes established that CaMKIK alpha and -beta are the products of distinct genes. In addition to rat, homologous nucleic acids corresponding to these CaM kinase kinases are present in humans and the nematode, Caenorhabditis elegans. CaMKIK alpha and CaMKIK beta are thus representatives of a family of enzymes, which may function as key intermediaries in Ca(2+)-CaM-driven signal transduction cascades in a wide variety of eukaryotic organisms.

Inactivation of calmodulin-dependent protein kinase IV by autophosphorylation of serine 332 within the putative calmodulin-binding domain

When brain calmodulin-dependent protein kinase IV is incubated with calmodulin-dependent protein kinase IV kinase under the phosphorylation conditions in the presence of Ca2+/calmodulin, rapid initial incorporation of 1 mol of phosphate into 1 mol of the enzyme by the action of the kinase kinase occurs, resulting in marked activation of the enzyme, and the subsequent incorporation of more than 3 mol of phosphate by autophosphorylation occurs, resulting in no significant change in the activity (Okuno, S., Kitani, T., and Fujisawa, H. (1994) J. Biochem. (Tokyo) 116, 923-930; Okuno, S., Kitani, T., and Fujisawa, H. (1995) J. Biochem. (Tokyo) 117, 686-690). After the maximal phosphorylation, the continued incubation in the presence of excess EGTA resulted in additional autophosphorylation of the enzyme, leading to a complete loss of the Ca2+/calmodulin-dependent activity, while causing no significant change in the Ca2+/calmodulin-independent activity. The amino acid sequence analysis revealed that the autophosphorylation after removal of Ca2+ occurred on Ser332, Ser333, Ser337, and Ser341. Analysis by site-directed mutagenesis clearly showed that the autophosphorylation site responsible for the inactivation is Ser332. Thus, calmodulin-dependent protein kinase IV activated by the kinase kinase may lose its Ca2+/calmodulin-dependent activity by autophosphorylation on Ser332 located within the putative calmodulin-binding domain in the absence of Ca2+.

Expression of Ca2+/calmodulin-dependent protein kinase types II and IV, and reduced DNA synthesis due to the Ca2+/calmodulin-dependent protein kinase inhibitor KN-62 (1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenyl piperazine) in small cell lung carcinoma

Because changes in intracellular Ca2+ affect progression through the mitotic cell cycle, we investigated the role of Ca2+-binding proteins in regulating cell cycle progression. Evidence was found demonstrating that the activation of Ca2+/calmodulin-dependent protein kinase (CaM kinase) inhibits cell cycle progression in small cell lung carcinoma (SCLC) cells. We also demonstrated that SCLC cells express both CaM kinase type II (CaMKII) and CaM kinase type IV (CaMKIV). Five independent SCLC cell lines expressed proteins reactive with antibody to the CaMKII beta subunit, but none expressed detectable proteins reactive with antibody to the CaMKII alpha subunit. All SCLC cell lines tested expressed both the alpha and beta isoforms of CaMKIV. Immunoprecipitation of CaMKII from SCLC cells yielded multiple proteins that autophosphorylated in the presence of Ca2+ / calmodulin. Autophosphorylation was inhibited by the CaMKII(281-302) peptide, which corresponds to the CaMKII autoinhibitory domain, and by 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4- phenylpiperazine (KN-62), a specific CaM kinase antagonist. Influx of Ca2+ through voltage-gated Ca2+ channels stimulated phosphorylation of CaMKII in SCLC cells, and this was inhibited by KN-62. Incubation of SCLC cells of KN-62 potently inhibited DNA synthesis, and slowed progression through S phase. Similar anti-proliferative effects of KN-62 occurred in SK-N-SH human neuroblastoma cells, which express both CaMKII and CaMKIV, and in K562 human chronic myelogenous leukemia cells, which express CaMKII but not CaMKIV. The expression of both CaMKII and CaMKIV by SCLC cells, and the sensitivity of these cells to the anti-proliferative effects of KN-62, suggest a role for CaM kinase in regulating SCLC proliferation.

The CREB, ATF-1, and ATF-2 transcription factors from bovine leukemia virus-infected B lymphocytes activate viral expression

Efficient transcription and replication of the bovine leukemia virus (BLV) genome require both the viral long terminal repeat (LTR) and the virus-coded transcriptional activator Tax, which functions through a 21-bp sequence (Tax-responsive element [TxRE]) which is repeated three times within the LTR. Since Tax does not bind directly to DNA, host cell transcription factors play a central role in BLV expression. Electrophoretic mobility shift assays with nuclear extracts prepared with infected bovine B lymphocytes revealed five TxRE-specific complexes (C1, C2, C3, C4, and C5). Here, by using a UV-induced indirect labeling technique (UV cross-linking) in conjunction with mobility shift assays, eight major polypeptides of 31, 33, 42, 46, 51, 57, 87, and 119 kDa were identified within these five complexes. Immunoprecipitation experiments identified the 57- and 119-kDa proteins as cyclic AMP response element-binding (CREB) proteins, the 46- and 51-kDa proteins as activating transcription factor-1 (ATF-1), and the 87-kDa as protein ATF-2. All of these proteins (except the ATF-1 protein of 51 kDa) belong to the complex C1, which is the major complex identified in freshly isolated BLV-infected lymphocytes from cattle with persistent lymphocytosis. In transient-cotransfection experiments, these three transcription factors were able to activate LTR-directed gene expression in the presence of protein kinase A or Ca2+/calmodulin-dependent protein kinase IV. CREB protein, ATF-1, and ATF-2 thus appear to be the major transcription factors involved in the early stages of viral expression.

Inhibition of voltage-gated Ca2+ channel activity in small cell lung carcinoma by the Ca2+/calmodulin-dependent protein kinase inhibitor KN-62 (1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperaz ine)

Although small cell lung carcinoma (SCLC) cells express both voltage-gated Ca2+ channels (VGCC) and second messenger-operated Ca2+ channels (SMOCC), little is known about the factors that regulate the activity of these channels in SCLC cells. Ca2+/calmodulin-dependent protein kinase (CaM kinase) type II has been implicated recently in regulating Ca2+ channel activity in other cell types. Because of this, we investigated the effects of the specific CaM kinase antagonist 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tryosyl] -4-phenylpiperazine [sequence: see text] (KN-62) on Ca2+ channel activity in SCLC cells. Incubation with 10 microM KN-62 for 20 min inhibited depolarization-dependent 45Ca2+ influx by 96.1 +/- 2.1% in four independent SCLC cell lines, and by 42.2 +/- 6.8% in the NCI-H146 SCLC cell line. Similar inhibitory effects of KN-62 were observed when Fura-2 was used to measure depolarization-dependent Ca2+ influx. These results indicate that KN-62 potently inhibits VGCC activity in SCLC cells. In contrast, KN-62 (10 microM, 20 min) did not inhibit significantly Ca2+ mobilization induced by muscarinic acetylcholine receptor (mAChR) activation in SCLC cells. This indicates that SMOCC are less susceptible than VGCC to inhibition by KN-62 in SCLC cells. Because mAChR activation also inhibits VGCC activity in SCLC cells, we examined the effects of KN-62 on the mAChR-mediated inhibition of VGCC activity. To do this, we measured depolarization-dependent 45Ca2+ influx in SCLC cells incubated with submaximal concentrations of KN-62 and the mAChR agonist carbachol. Treatment of cells with both drugs resulted in almost twice as much inhibition of VGCC activity as in cells treated with only one of the drugs. This indicates that inactivation of CaM kinase with KN-62 does not suppress the ability of mAChR agonists to inhibit VGCC activity.

Activation of Ca2+/calmodulin-dependent protein kinase (CaM-kinase) IV by CaM-kinase kinase in Jurkat T lymphocytes

Ca2+/calmodulin-dependent protein kinase IV (CaM-kinase IV), a member of the CaM-kinase family involved in transcriptional regulation, is stimulated by Ca2+/CaM but also requires phosphorylation by a CaM-kinase kinase for full activation. In this study we investigated the physiological role of a CaM-kinase cascade in Jurkat T human lymphocytes through antigen receptor (CD3) signaling. Total and Ca(2+)-independent CaM-kinase IV activities were increased 8-14-fold by anti-CD3 antibody. This CD3-mediated activation involved phosphorylation since the immunoprecipitated CaM-kinase IV from stimulated Jurkat cells could be subsequently inactivated in vitro by protein phosphatase 2A. CaM-kinase IV immunoprecipitated from unstimulated Jurkat cells or CD3-negative mutant Jurkat cells could be activated in vitro 10-40-fold by CaM-kinase kinase purified from rat brain or thymus, whereas CaM-kinase IV from CD3-stimulated wild-type Jurkat cells was only activated to 2-3-fold by exogenous CaM-kinase kinase. CaM-kinase IV activation was triggered by Ca2+ acting through calmodulin since activation could also be elicited by ionomycin treatment, and CD3-mediated activation was blocked by the calmodulin antagonist calmidazolium. These data are consistent with a CaM-kinase cascade in which CaM-kinase IV is activated by a CaM-kinase kinase cascade triggered by elevated intracellular calcium in Jurkat cells.

Organization and analysis of the complete rat calmodulin-dependent protein kinase IV gene

A 42-kilobase pair region of rat DNA containing the Ca2+/calmodulin-dependent protein kinase IV (CaM kinase IV) gene has been cloned and characterized. The gene consists of 12 exons and 11 introns and is predicted to encode both beta and alpha forms of CaM kinase IV as well as the testis-specific calmodulin-binding protein calspermin. The promoter utilized to generate the alpha-kinase isoform is located in intron 1, whereas the promoter utilized to produce the calspermin transcript is contained in intron 10. The calspermin promoter region which extends from -200 to +321 relative to the calspermin transcription initiation site that contains two cyclic AMP response elements (CRE) at -70 and -50 and has been shown previously to be inactive in NIH3T3 cells (Sun, Z., Sassone-Corsi, P., and Means, A. R. (1995) Mol. Cell. Biol. 15, 561-571) was ligated to the lacZ reporter gene and used to generate transgenic mice. The promoter was expressed exclusively in postmeiotic testis where beta-galactosidase was found predominantly in elongating spermatids. The cell and developmental specificity of transgene expression was very similar to the pattern shown by the endogenous gene. Although the transgene promoter was silent in somatic tissues, beta-galactosidase expression could be restored in primary cultures of skin fibroblasts by introduction of vectors encoding CREM tau and CaM kinase IV.

An intron facilitates activation of the calspermin gene by the testis-specific transcription factor CREM tau

Calspermin is a high affinity Ca2+/calmodulin binding protein that is found only in postmeiotic male germ cells. Our previous studies have shown that the calspermin transcript is produced by utilization of a testis-specific promoter located within an intron of the calmodulin kinase IV gene. This promoter contains two cAMP response element-like motifs that bind the testis-specific transcription factor CREM tau. This interaction is required for transcriptional activation. Here we describe a novel regulatory element, the 111-base pair first intron of the calspermin gene, which is also required for enhancement of transcription by CREM tau via the cAMP response element motifs. Deletion or inversion of this intron results in loss of CREM tau-mediated stimulation of transcription. However, CREM tau stimulates calspermin promoter activity when the intron is moved upstream of the promoter but only when inserted in the proper orientation. Footprint, linker scanning, and deletion analyses were used to identify regulatory elements in the intron. We suggest that the intron functions as an orientation-dependent but position-independent regulatory element to activate the calspermin promoter by facilitating the stimulatory effect of CREM tau on transcription.

Phosphorylation and activation of Ca(2+)-calmodulin-dependent protein kinase IV by Ca(2+)-calmodulin-dependent protein kinase Ia kinase. Phosphorylation of threonine 196 is essential for activation

Purified pig brain Ca(2+)-calmodulin (CaM)-dependent protein kinase Ia kinase (Lee, J. C., and Edelman, A. M. (1994) J. Biol. Chem. 269, 2158-2164) enhances, by up to 24-fold, the activity of recombinant CaM kinase IV in a reaction also requiring Ca(2+)-CaM and MgATP. The addition of brain extract, although capable of activating CaM kinase IV by itself, provides no further activation beyond that induced by purified CaM kinase Ia kinase, consistent with the lack of a requirement of additional components for activation. Activation is accompanied by the development of significant (38%) Ca(2+)-CaM-independent CaM kinase IV activity. In parallel fashion to its activation, CaM kinase IV is phosphorylated in a CaM kinase Ia kinase-, Ca(2+)-CaM-, and MgATP-dependent manner. Phosphorylation occurs on multiple serine and threonine residues with a Ser-P:Thr-P ratio of approximately 3:1. The identical requirements for phosphorylation and activation and a linear relationship between extent of phosphorylation of CaM kinase IV and its activation state indicate that CaM kinase IV activation is induced by its phosphorylation. Replacement of Thr-196 of CaM kinase IV with a nonphosphorylatable alanine by site-directed mutagenesis abolishes both the phosphorylation and activation of CaM kinase IV, demonstrating that Thr-196 phosphorylation is essential for activation.

Calspermin gene transcription is regulated by two cyclic AMP response elements contained in an alternative promoter in the calmodulin kinase IV gene

The transcript for the high-affinity Ca2+/calmodulin-binding protein calspermin is generated from the gene encoding Ca2+/calmodulin-dependent protein kinase IV only in postmeiotic germ cells during spermatogenesis. We demonstrate that this testis-specific calspermin transcript can be produced in heterologous cells by utilization of a promoter located in an intron of the calmodulin (CaM) kinase IV gene. Critical motifs within this promoter are two cyclic AMP response element (CRE)-like sequences located about -70 and -50 bp upstream of the transcriptional initiation site. Both CRE motifs are footprinted by the authentic testis-specific transcriptional activator CREM tau or by CREM tau present in adult testis nuclear extract. Whereas a 2.1-kb DNA fragment containing the calspermin promoter is inactive when transfected into NIH 3T3 cells, activity can be restored by cotransfection of CREM tau and protein kinase A or CaM kinase IV but not CaM kinase II alpha. Restoration of activity is greatly reduced by mutation of the two CRE motifs. Since CRE-like motifs have been identified in many genes uniquely expressed in postmeiotic germ cells, which contain abundant CREM tau protein, we suggest that CREM tau may function as one transcription factor responsible for the expression of postmeiotic germ cell-specific genes.

Differential activation of CREB by Ca2+/calmodulin-dependent protein kinases type II and type IV involves phosphorylation of a site that negatively regulates activity

The cAMP response element-binding protein (CREB) has been shown to mediate transcriptional activation of genes in response to both cAMP and calcium influx signal transduction pathways. The roles of two multifunctional calcium/calmodulin-dependent protein kinases, CaMKIV and CaMKII, were examined in transient transfection studies that utilized either the full-length or the constitutively active forms of these kinases. The results indicate that CaMKIV is much more potent than CaMKII in activating CREB in three different cell lines. It was also found in these studies that Ser133 of CREB is essential for its activation by CaMKIV. Because both CaMKII and CaMKIV can phosphorylate CREB, we pursued further the mechanism by which CaMKII and CaMKIV differentially regulate CREB activity. Mutagenesis studies and phosphopeptide mapping analysis demonstrated that in vitro, CaMKIV phosphorylates CREB at Ser133 only, whereas CaMKII phosphorylates CREB at Ser133 and a second site, Ser142. Transient transfection studies revealed that phosphorylation of Ser142 by CaMKII blocks the activation of CREB that would otherwise occur when Ser133 is phosphorylated. When Ser142 was mutated to alanine, CREB was activated by CaMKII, as well as by CaMKIV. Furthermore, mutation of Ser142 to alanine enhanced the ability of Ca2+ influx to activate CREB, suggesting a physiological role for the phosphorylation of Ser142 in modulation of CREB activity. These data provide evidence for a new mechanism for regulation of CREB activity involving phosphorylation of a negative regulatory site in the transcriptional activation domain. The studies also provide new insights into possible interactions between the cAMP and Ca2+ signaling pathways in the regulation of transcription. In particular, changes in intracellular Ca2+ have the potential to either inhibit or augment the ability of cAMP to stimulate transcription, depending on the presence of specific forms of Ca2+/calmodulin-dependent protein kinases.

Caenorhabditis elegans unc-51 gene required for axonal elongation encodes a novel serine/threonine kinase

Mutations in the unc-51 gene of the nematode Caenorhabditis elegans result in various abnormalities in axonal elongation and axonal structures. We cloned the unc-51 gene by tagging with the transposon Tc1. The wild-type unc-51 gene, which rescued the mutant phenotypes, encodes a novel serine/threonine kinase of 856 amino acids. Mutation sites were identified in the unc-51 gene of six mutants. A Lys-->Met mutation created in vitro in the kinase domain led to the loss of rescuing activity and was dominant negative, indicating that the kinase domain of Unc-51 is essential for the function. Expression of an unc-51/lacZ fusion gene was observed in many neurons at all stages. We propose that protein phosphorylation by the unc-51 product is important for axonal elongation and possibly for axonal guidance.

Calcium/calmodulin-dependent protein kinase types II and IV differentially regulate CREB-dependent gene expression

Phosphorylation of CREB (cyclic AMP [cAMP]- response element [CRE]-binding protein) by cAMP-dependent protein kinase (PKA) leads to the activation of many promoters containing CREs. In neurons and other cell types, CREB phosphorylation and activation of CRE-containing promoters can occur in response to elevated intracellular Ca2+. In cultured cells that normally lack this Ca2+ responsiveness, we confer Ca(2+)-mediated activation of a CRE-containing promoter by introducing an expression vector for Ca2+/calmodulin-dependent protein kinase type IV (CaMKIV). Activation could also be mediated directly by a constitutively active form of CaMKIV which is Ca2+ independent. The CaMKIV-mediated gene induction requires the activity of CREB/ATF family members but is independent of PKA activity. In contrast, transient expression of either a constitutively active or wild-type Ca2+/calmodulin-dependent protein kinase type II (CaMKII) fails to mediate the transactivation of the same CRE-containing reporter gene. Examination of the subcellular distribution of transiently expressed CaMKIV and CaMKII reveals that only CaMKIV enters the nucleus. Our results demonstrate that CaMKIV, which is expressed in neuronal, reproductive, and lymphoid tissues, may act as a mediator of Ca(2+)-dependent gene induction.

Calcium/calmodulin-dependent protein kinase types II and IV differentially regulate CREB-dependent gene expression

Phosphorylation of CREB (cyclic AMP [cAMP]- response element [CRE]-binding protein) by cAMP-dependent protein kinase (PKA) leads to the activation of many promoters containing CREs. In neurons and other cell types, CREB phosphorylation and activation of CRE-containing promoters can occur in response to elevated intracellular Ca2+. In cultured cells that normally lack this Ca2+ responsiveness, we confer Ca(2+)-mediated activation of a CRE-containing promoter by introducing an expression vector for Ca2+/calmodulin-dependent protein kinase type IV (CaMKIV). Activation could also be mediated directly by a constitutively active form of CaMKIV which is Ca2+ independent. The CaMKIV-mediated gene induction requires the activity of CREB/ATF family members but is independent of PKA activity. In contrast, transient expression of either a constitutively active or wild-type Ca2+/calmodulin-dependent protein kinase type II (CaMKII) fails to mediate the transactivation of the same CRE-containing reporter gene. Examination of the subcellular distribution of transiently expressed CaMKIV and CaMKII reveals that only CaMKIV enters the nucleus. Our results demonstrate that CaMKIV, which is expressed in neuronal, reproductive, and lymphoid tissues, may act as a mediator of Ca(2+)-dependent gene induction.

The cDNA sequence and characterization of the Ca2+/calmodulin-dependent protein kinase-Gr from human brain and thymus

We have isolated and sequenced cDNAs encoding Ca2+/calmodulin-dependent protein kinase type Gr (CaM-K-Gr, also called CaM-K-IV) from human brain and thymus. The sequence of the protein coding region of the cDNA is identical in both brain and thymus, although Northern hybridization analysis shows variation of the mRNA transcripts in these tissues. The sequence predicts a protein of M(r) 51,897 that is 83.7% identical and shows 89.2% similarity with the rat homologue. The deduced human CaM-K-Gr is identical to the rat and mouse proteins in the portion of the enzyme involved in ATP binding, the catalytic domain and Ca2+/calmodulin-binding domain; however, the N terminus of the human kinase, which may comprise a second regulatory domain [McDonald et al., J. Biol. Chem. 268 (1993) 10054-10059], contains a 4-amino-acid (aa) insertion relative to the rodent enzymes. Additionally, the C-terminal association domain shows only 45.2 and 41.6% identity with the rat and mouse proteins, respectively, suggesting that this domain is not constrained by stringent structural and functional requirements. Based on the predicted aa sequence of the human kinase, we produced polyclonal antisera against a C-terminal peptide that recognizes two forms of CaM-K-Gr in human T-cell lymphoma and neuroblastoma cell lines. The human antiserum cross-reacts with the rat and mouse proteins and immunoprecipitates the active kinase.

A Ca2+/calmodulin-dependent protein kinase, CaM kinase-Gr, expressed after transformation of primary human B lymphocytes by Epstein-Barr virus (EBV) is induced by the EBV oncogene LMP1

CaM kinase-Gr is a multifunctional Ca2+/calmodulin-dependent protein kinase which is enriched in neurons and T lymphocytes. The kinase is absent from primary human B lymphocytes but is expressed in Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines, suggesting that expression of the kinase can be upregulated by an EBV gene product(s). We investigated the basis of CaM kinase-Gr expression in EBV-transformed cells and the mechanisms that regulate its activity therein by using an EBV-negative Burkitt lymphoma cell line, BJAB, and BJAB cells converted to expression of individual EBV proteins by single-gene transfer. CaM kinase-Gr expression was upregulated in BJAB cells by EBV latent-infection membrane protein 1 (LMP1) but not by LMP2A or by nuclear proteins EBNA1, EBNA2, EBNA3A, and EBNA3C. In LMP1-converted BJAB cells, the kinase was functional and was dramatically activated upon cross-linking of surface immunoglobulin M. Overlapping cDNA clones that encode human CaM kinase-Gr were sequenced, revealing 81% amino acid identity between the rat and human proteins. Transfection of BJAB cells with an expression construct for the human enzyme resulted in a functional kinase which was shown by epitope tagging to localize primarily to cytoplasmic and perinuclear structures. Induction of CaM kinase-Gr expression by LMP1 provides the first example of a Ca2+/calmodulin-dependent protein kinase upregulated by a viral protein. In view of the key role played by LMP1 in B-lymphocyte immortalization by EBV, these findings implicate CaM kinase-Gr as a potential mediator of B-lymphocyte growth transformation.

DUN1 encodes a protein kinase that controls the DNA damage response in yeast

DNA damage induces the expression of many genes proposed to enhance DNA repair capacities. We investigated the mechanism by which DNA damage induces transcription of RNR3, a subunit of ribonucleotide reductase. Five complementation groups of DNA-damage uninducible (dun) mutants were identified. Each is sensitive to DNA damage. dun1 mutants are also defective for RNR1 and RNR2 induction but are proficient for induction of other genes, defining the existence of at least two distinct DNA damage induction pathways. DUN1 encodes a nuclear protein kinase that is also a phosphoprotein. Phosphorylation of Dun1 increases in response to DNA damage in a Dun1-dependent manner, suggesting an increase in autophosphorylation activity. These results establish the existence of a eukaryotic SOS response regulated by protein phosphorylation.

Cloning and sequencing of a gene encoding the beta polypeptide of Ca2+/calmodulin-dependent protein kinase IV and its expression confined to the mature cerebellar granule cells

A cDNA encoding the beta polypeptide of Ca2+/calmodulin-dependent protein kinase IV (CaM kinase IV) was isolated and sequenced from a rat cerebellar cDNA library. By in situ hybridization histochemistry, we demonstrated the differential gene expression for alpha and beta polypeptides of CaM kinase IV in mature and developing rat brains using oligonucleotide probes specific for each polypeptide.

Gene expression of Ca2+/calmodulin-dependent protein kinase of the cerebellar granule cell type or type IV in the mature and developing rat brain

The localization and ontogenic changes of expression of the mRNA for Ca2+/calmodulin-dependent protein kinase of the cerebellar granule cell type or type IV (CaM kinase Gr or IV) in the rat brain were examined by in situ hybridization histochemistry. At the young adult stage, intense expression signals for this kinase mRNA were detected in the cerebellar granule cells, the hippocampal pyramidal cells, the dentate granule cells, and the piriform cortex. Moderate levels of the mRNA were expressed in the thalamic nuclei and the cerebral cortex. No distinct expression signals were detected in the Purkinje cells and most brainstem nuclei except for the pontine nuclei, locus ceruleus and inferior olive which showed weak expression. During development, two chronological patterns of changes in the gene expression for this kinase were discerned. The first was a high and persistent expression from the developing stages till the adult stage, which was observed in the cerebellar granule cells, the hippocampal pyramidal cells and the dentate granule cells. The other was a transiently high expression during limited developmental periods, which was observed in the Purkinje cells, neurons in the inferior olive, various brain stem nuclei, and the subventricular neuronal cells. These findings suggest that this Ca2+/calmodulin-dependent protein kinase is involved differentially in multiple Ca2+ signaling pathways in different developing and mature neurons.

GABAA receptor function and regional analysis of subunit mRNAs in long-sleep and short-sleep mouse brain

The greater sensitivity of long-sleep (LS), as compared with short-sleep (SS), mice to ethanol is due in part to differences in GABAA receptor function in specific brain regions. To determine if differences in subunit composition of GABAA receptors contribute to this differential sensitivity, we measured alpha 1 and gamma 2 subunit mRNAs with Northern analysis and in situ hybridization and gamma 2S, gamma 2L and alpha 6 subunit mRNAs with polymerase chain reaction (PCR) amplification. No differences in mRNAs in whole brain were apparent by Northern analysis. In situ hybridization revealed that alpha 1 and gamma 2 subunit mRNAs were co-localized in many brain regions but that they still had distinct patterns of hybridization. However, the few differences observed between LS and SS mice in the levels of hybridization for these subunits did not show a regional distribution consistent with ethanol sensitivity differences. Similar ratios of gamma 2L, and gamma 2S subunit mRNAs were found in LS and SS mouse cerebral cortex and hippocampus, and both mouse lines expressed essentially only gamma 2L subunit mRNA in cerebellum. mRNA for the alpha 6 subunit was detected only in cerebellum and also was qualitatively similar between LS and SS mice. Studies of muscimol-stimulated 36Cl- uptake by cortical membrane vesicles confirmed earlier findings that ethanol does not enhance function of GABAA receptors in SS mice when assayed at 30 degrees C. However, at 34 degrees C ethanol did increase this function in SS mice although the enhancement remained greater in LS mice. These functional results, together with the results showing similar levels of alpha 1, gamma 2S, gamma 2L and alpha 6 subunits in LS and SS mice, suggest that the ethanol-insensitivity of SS mouse GABAA receptors cannot be due solely to lack of subunits required for ethanol action and further suggest that differences in catalytic mechanisms affecting post-translational processing may account for some genetic differences in ethanol sensitivity of GABAA receptors.