The association of death-associated protein kinase hypermethylation with early recurrence in superficial bladder cancers

Mechanisms for bladder carcinogenesis and the development of recurrentbladder cancer remain unclear. Aberrant methylation of the 5' CpG island is thought to play an important role in the inactivation of the tumor suppressor genes in cancer. To study whether specific or bulk hypermethylation predicts intrabladder recurrence, we determined the frequency of aberrant promoter hypermethylation of seven genes, hMLH1, O(6)-methylguanine-DNA-methyltransferase (MGMT), p16, Von Hippel-Lindau (VHL), death-associated protein kinase (DAP-kinase), glutathione S-transferase P1 (GST-P1) and E-cadherin in 55 superficial bladder cancers and 5 normal urothelial epithelia by methylation-specific PCR (MSP). These patients of superficial bladder cancer had been followed prospectively by cystoscopy. Simultaneous hypermethylation of three genes or more among the seven genes was observed in 2 (7%) of 30 patients in the nonrecurrence group and 7 (28%) of 25 patients in the recurrence group. There was a significant concordance between the number of methylated genes and the development of recurrence (P = 0.012). In particular, the recurrence rate for 24 months was 88% for hypermethylation of DAP-kinase and 28% for nonmethylation of DAP-kinase. Hypermethylation of DAP-kinase is, therefore, a strong indicator of the superficial bladder cancer associated with a high recurrence rate (P < 0.001; hazards ratio, 7.01). Our results suggest that hypermethylation of DAP-kinase might be a useful prognostic marker for disease recurrence in superficial bladder cancers.

Expression of glycogen synthase kinase-3 isoforms in mouse tissues and their transcription in the brain

Glycogen synthase kinase-3alpha and -3beta (GSK-3alpha and -3beta) are multi-substrate, serine/threonine-specific kinases that can phosphorylate microtubule-associated protein tau and other neuronal proteins. In this study, the expression level and mRNA distribution of two GSK-3 isoforms, GSK-3alpha and -3beta in mice were investigated. Northern blot analyses indicated that GSK-3alpha mRNA is encoded by a 2.5-kb transcript in adult tissues, whereas a 4.1-kb transcript was found in neonatal tissues. The GSK-3beta mRNA is encoded by a 1.6-kb transcript in the testis and a 7.6-kb transcript in the brain, and in many other adult tissues, but not neonatal tissues. Western blot analyses demonstrated that GSK-3beta protein was mainly expressed in the brain and heart, whereas GSK-3alpha was highly expressed in the brain, heart, and testis. A non-radioactive in situ hybridization study using specific digoxigenin-labeled RNA probes showed that GSK-3alpha and -3beta mRNAs were found in many brain regions, and were especially abundant in the hippocampus, cerebral cortex, and the Purkinje cells of the cerebellum. This implies the importance of GSK-3alpha and -3beta for brain function. The differential expression of GSK-3alpha and -3beta mRNAs as well as proteins in other tissues indicate that they play different roles in cellular functions and the developmental process.

Biphasic developmental changes in Ca2+/calmodulin-dependent proteins in R6/2 Huntington's disease mice

Widespread disturbances in calcium-dependent proteins are reported both in humans with advanced Huntington's disease (HD) and in symptomatic HD transgenic mice. Using a HD mouse model transgenic for exon 1 of the abnormal gene (e.g. the Bates R6/2 mouse), we found increased expression of calmodulin kinase IV and neuronal nitric oxide synthase (NOS) in 3-week-old presymptomatic HD mice striatum and cortex. Conversely, reduced expression was found at 6 weeks (early symptom onset) and 11 weeks (advanced disease) of age. The changes in protein expression may have a broad impact on the HD striatum. Calmodulin kinase IV directly regulates the activation of the transcription factors CREB (cyclic AMP response element binding protein) and CREM (cyclic AMP response element modulator) and, as well, modulates the activity of neuronal NOS. In homeostasis, nitric oxide is involved in long-term potentiation, neurotransmission, endocrine regulation and cerebral blood flow regulation, among others, while under pathological conditions nitric oxide combines with superoxide to produce the potent neurotoxin peroxynitrite. The current findings suggest that mutant HD protein may alter these processes by disturbing the regulation of calmodulin kinase IV and neuronal NOS expression across the lifespan of the HD mouse.

Seizure-mediated accumulation of the beta subunit of Ca2+/calmodulin-dependent protein kinase II in nuclei of mouse brain cells

We identified a 45-kDa protein by 2D electrophoresis that was enhanced following pentylenetetrazol (PTZ)-mediated seizures. Mass-spectrography of this protein revealed the beta subunit of Ca2+/calmodulin-dependent protein kinase II (CaMKIIbeta), although no evidence for increase in bulk CaMKIIbeta transcripts was obtained. Physicochemical parameters of the 45-kDa species coincided with those of the type 7 isoform of CaMKIIbeta, CaMKIIbeta7. Reverse transcription-polymerase chain reaction revealed the existence of the CaMKIIbeta7 transcript in the mouse brain, but its RNA content was small and was not elevated by PTZ injection. CaMKIIbeta7 protein is thought to be accumulated in the nuclei of brain cells by PTZ-mediated seizure via some cellular mechanisms other than transcriptional and post-transcriptional regulation.

Decreased prefrontal CaMKII alpha mRNA in bipolar illness

Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays critical roles in neurotransmission, synaptic plasticity, learning and memory. The aim of this study was to examine, by in situ hybridization, prefrontal cortical expression of CaMKII alpha mRNA in postmortem brains of unipolar, bipolar, schizophrenic, and control subjects. Compared to controls, bipolar patients had significantly lower levels of CaMKII alpha mRNA in laminae I-VI of Brodmann's area 9 and laminae I-III and VI of area 46. Unipolar patients also exhibited significantly lower levels of CaMKII alpha mRNA in laminae I-IV of area 9 than did controls. The significant decrease in CaMKII alpha mRNA in bipolar patients could be associated with some of the affective and cognitive alterations that have been linked to prefrontal cortical dysfunction in bipolar disorder, although this requires further direct examination.

High frequency of promoter hypermethylation of the death-associated protein-kinase gene in nasopharyngeal carcinoma and its detection in the peripheral blood of patients

PURPOSE

Death-associated protein (DAP)-kinase gene is frequently inactivated by promoter hypermethylation in cancer. The aim of this study was to evaluate the promoter methylation status of the DAP-kinase gene in nasopharyngeal carcinoma (NPC).

EXPERIMENTAL DESIGN

The methylation status was evaluated by methylation-specific PCR (MSP). Thirty-two NPC biopsy specimens, plasma and buffy coat of 12 patients, 5 NPC cell lines, 3 normal nasopharyngeal biopsy tissues, and 2 normal nasopharyngeal epithelial primary cultures were included in this study.

RESULTS

There was no promoter hypermethylation in all 3 normal nasopharyngeal tissues and 2 normal nasopharyngeal primary cultures. Hypermethylation was found in 24 (75%) NPC primary tumor biopsies and 4 (80%) NPC cell lines. Of the 24 patients with hypermethylation of DAP-kinase promoter in the primary tumors, 12 patients had their plasma and buffy coat DNA available for MSP study. Hypermethylated DAP-kinase promoter was detectable in 5 patients in the plasma but not in the buffy coat, 2 patients in the buffy coat but not in the plasma, and 1 patient in both plasma and buffy coat. Four patients had no detectable hypermethylated DAP-kinase promoter in both plasma and buffy coat. Hypermethylation of DAP-kinase promoter was found in both early- and late-stage NPC.

CONCLUSIONS

Our results show that hypermethylation of the DAP-kinase promoter is a common early event in NPC. The high frequency of identification of hypermethylated DAP-kinase promoter in plasma and buffy coat of NPC patients illustrates its potential clinical application as tumor marker for the diagnosis and monitoring of treatment result.

PTH induction of transcriptional activity of the cAMP response element-binding protein requires the serine 129 site and glycogen synthase kinase-3 activity, but not casein kinase II sites

We have previously shown that PTH induction of c-fos expression in the rat osteoblastic cell line UMR 106-01 requires the phosphorylation of cAMP response element-binding protein (CREB) at serine 133. Here we show that this event is not sufficient for induced transcriptional activity in UMR cells. Serine 129, but not the casein kinase II sites (serines 108, 111, 114, 117, and 121), also plays a role in the activation of CREB. First, by metabolically labeling an epitope-tagged CREB, we determined that, in addition to serine 133, other residues are phosphorylated in vivo. Using mutational analysis of a GAL4-CREB reporter system we demonstrate that serines 129 and 133 are both required for PTH-induced transcriptional activity, whereas the casein kinase II sites are not. Furthermore, PTH failed to induce transcriptional activity of GAL4-CREB in cells treated with genistein, a general tyrosine kinase inhibitor known to inhibit glycogen synthase kinase-3 (GSK-3) activity, or LiCl, the most specific GSK-3-inhibiting agent known, strongly implicating GSK-3beta in this process. Importantly, although genistein and LiCl each inhibit GSK-3beta activity, neither prevented the phosphorylation of serine 133 induced by PTH. Lastly, when serine 129 is replaced with a negatively charged aspartic acid, LiCl has no effect on the PTH-induced trans-activation of CREB. We propose that GSK-3beta phosphorylates CREB at serine 129 and thus is required for the increased transcriptional activity of CREB in response to PTH.

Caspase-3 activation induced by inhibition of mitochondrial complex I is facilitated by glycogen synthase kinase-3beta and attenuated by lithium

The compound 1-methyl-4-phenylpyridinium (MPP) is a selective inhibitor of mitochondrial complex I, and is widely used in model systems to elicit neurochemical alterations that may be associated with Parkinson's disease. In the present study treatment of human neuroblastoma SH-SY5Y cells with MPP resulted in a time- and concentration-dependent activation of the apoptosis-associated cysteine protease caspase-3, and caused morphological changes characteristic of apoptosis. To test if the activation state of the cell survival-promoting phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway affects MPP-induced caspase-3 activation, PI3K was inhibited with LY294002, or activated with insulin-like growth factor-1. MPP-induced caspase-3 activation was increased by inhibition of PI3K, and decreased by stimulation of PI3K, indicative of anti-apoptotic signaling by the PI3K/Akt pathway. To test if glycogen synthase kinase-3beta (GSK3beta), a pro-apoptotic kinase that is inhibited by Akt, is involved in regulating MPP-induced apoptosis, overexpression of GSK3beta and lithium, a selective inhibitor of GSK3beta, were used to directly alter GSK3beta activity. MPP-induced caspase-3 activity was increased by overexpression of GSK3beta. Conversely, the GSK3beta inhibitor lithium attenuated MPP-induced caspase-3 activation. To test if these regulatory interactions applied to other mitochondrial complex I inhibitors, cells were treated with rotenone. Rotenone-induced activation of caspase-3 was enhanced by inhibition of PI3K or increased GSK3beta activity, and was attenuated by inhibiting GSK3beta with lithium. Overall, these results indicate that inhibition of GSK3beta provides protection against the toxic effects of agents, such as MPP and rotenone, that impair mitochondrial function.

Reduced activity and protein expression of NOS in R6/2 HD transgenic mice: effects of L-NAME on symptom progression

Previous work found that dietary l-arginine alters symptom progression in mice transgenic for Huntington's disease (HD), and that cerebral blood flow (CBF) is abnormal in early stage HD patients. Both of these findings potentially implicate nitric oxide (NO) and its converting enzyme, nitric oxide synthase (NOS), in HD. The current experiment found that both NOS enzymatic activity and neuronal NOS (nNOS) protein expression were reduced (P<0.05) in R6/2 HD transgenic mice compared to non-HD controls (CON). Conversely, inducible NOS (iNOS) protein expression was not significantly different between groups. The changes in nNOS were accompanied by changes in protein expression of calmodulin kinase II (CaMKII) (P<0.05) and calmodulin kinase IV (CaMKIV) (P<0.05). Protein expression of 3-nitrotyrosine (3-NT), a marker for the neurotoxin peroxynitrite, was slightly increased in non-drug treated HD and was accompanied by increased immunostaining of 3-NT in cells adhering to the vasculature and choroid plexus. Mice that received the broad-spectrum NOS inhibitor N(g)-nitro-L-arginine methyl ester hydrochloride (L-NAME) via their drinking water had reduced NOS enzyme activity. NOS activity varied as a function of L-NAME dose, was virtually eliminated in the 500-mg/l groups, and correlated (P<0.05) with the behavioral scores as revealed by regression and correlation analyses. High dose L-NAME (500 mg/l) accelerated symptom onset in HD transgenics. These results support the hypothesis that nNOS activity and NO production are abnormal in HD, this in the setting of a more global dysregulation of calcium protein expression. Taken collectively with earlier data from our laboratory demonstrating abnormal CBF findings in early-stage HD patients, these results suggest that abnormalities in NOS function may significantly contribute to the neurodegeneration found in HD.

The effect of autonomous alpha-CaMKII expression on sensory responses and experience-dependent plasticity in mouse barrel cortex

The calcium/calmodulin kinase II (CaMKII) autophosphorylation site is thought to be important for plasticity, learning and memory. If autophosphorylation is prevented by a point mutation (T286A) LTP is blocked in the hippocampus and cortex. Conversely, if the point mutation mimics autophosphorylation (T286D) a range of frequencies that normally produce LTP in wild types cause LTD instead. In order to test whether the alphaCaMKII-T286D mutation increases levels of depression in vivo, we examined the effect of the alphaCaMKII-T286D transgene on plasticity induced in the barrel cortex by whisker deprivation. Surprisingly, the mutation did not affect depression or potentiation. However, in animals reared with the transgene turned on from birth, the surround receptive field responses were greater than normal. This effect may be due to the potentiating action of autophosphorylated CaMKII during early development.

Isoproterenol activates extracellular signal-regulated protein kinases in cardiomyocytes through calcineurin

BACKGROUND

Extracellular signal-regulated kinases (ERKs) and calcineurin have been reported to play important roles in the development of cardiac hypertrophy. We examined here the relation between calcineurin and ERKs in cardiomyocytes.

METHODS AND RESULTS

Isoproterenol activated ERKs in cultured cardiomyocytes of neonatal rats, and the activation was abolished by chelation of extracellular Ca(2+) with EGTA, blockade of L-type Ca(2+) channels with nifedipine, or depletion of intracellular Ca(2+) stores with thapsigargin. Isoproterenol-induced activation of ERKs was also significantly suppressed by calcineurin inhibitors in cultured cardiomyocytes as well as in the hearts of mice. Isoproterenol failed to activate ERKs in either the cultured cardiomyocytes or the hearts of mice that overexpress the dominant negative mutant of calcineurin. Isoproterenol elevated intracellular Ca(2+) levels at both systolic and diastolic phases and dose-dependently activated calcineurin. Inhibition of calcineurin also attenuated isoproterenol-stimulated phosphorylation of Src, Shc, and Raf-1 kinase. The immunocytochemistry revealed that calcineurin was localized in the Z band, and isoproterenol induced translocation of calcineurin and ERKs into the nucleus.

CONCLUSIONS

Calcineurin, which is activated by marked elevation of intracellular Ca(2+) levels by the Ca(2+)-induced Ca(2+) release mechanism, regulates isoproterenol-induced activation of ERKs in cardiomyocytes.

Developmental regulation of mitogen-activated protein kinase-activated kinases-2 and -3 (MAPKAPK-2/-3) in vivo during corpus luteum formation in the rat

The current study investigates the activation in vivo and regulation of the expression of components of the p38 mitogen-activated protein kinase (MAPK) pathway during gonadotropin-induced formation and development of the rat corpus luteum, employing a sequential PMSG/human CG (hCG) treatment paradigm. We postulated that the p38 MAPK pathway could serve to promote phosphorylation of key substrates during luteal maturation, since maturing luteal cells, thought to be cAMP-nonresponsive, nevertheless maintain critical phosphoproteins. Both p38 MAPK and its upstream activator MAPK kinase-6 (MKK6) were found to be chronically activated during the luteal maturation phase, with activation detected by 24 h post hCG and maintained through 4 days post hCG. The p38 MAPK downstream protein kinase target termed MAPK-activated protein kinase-3 (MAPKAPK-3) was newly induced at both mRNA and protein levels during luteal formation and maturation, while mRNA and protein expression of the closely related MAPKAPK-2 diminished. Two potential substrates for MAPKAPKs, the small heat shock protein HSP-27 and the cAMP regulatory element binding protein CREB, were monitored in vivo for phosphorylation. HSP-27 phosphorylation was not modulated during luteal maturation. In contrast, we observed sustained luteal-phase CREB phosphorylation in vivo, consistent with upstream MKK6/p38 MAPK activation and MAPKAPK-3 induction. MAPKAPK-3-specific immune complex kinase assays provided direct evidence that MAPKAPK-3 was in an activated state during luteal maturation in vivo. Cellular inhibitor studies indicated that an intact p38 MAPK path was required for CREB phosphorylation in a cellular model of luteinization, as treatment of luteinized granulosa cells with the p38 MAPK inhibitor SB 203580 strongly inhibited CREB phosphorylation. Transient transfection studies provided direct evidence that MAPKAPK-3 was capable of signaling to activate CREB transcriptional activity, as assessed by means of GAL4-CREB fusion protein construct coexpressed with GAL4-luciferase reporter construct. Introduction of wild-type, but not kinase-dead mutant, MAPKAPK-3 cDNA, into a mouse ovarian cell line stimulated GAL4-CREB- dependent transcriptional activity approximately 3-fold. Thus MAPKAPK-3 is indeed uniquely poised to support luteal maturation through the phosphorylation and activation of the nuclear transcription factor CREB.

p38 MAP kinase negatively regulates cyclin D1 expression in airway smooth muscle cells

We have demonstrated that platelet-derived growth factor (PDGF) stimulates p38 mitogen-activated protein (MAP) kinase activation in bovine tracheal myocytes, suggesting that p38 is involved in growth regulation. We therefore examined whether p38 regulates expression of cyclin D1, a G(1) cyclin required for cell cycle traversal. The chemical p38 inhibitors SB-202190 and SB-203580 each increased basal and PDGF-induced cyclin D1 promoter activity and protein abundance. Overexpression of a dominant negative allele of MAP kinase kinase-3 (MKK3), an upstream activator of p38alpha, had similar effects. Conversely, active MKK3 and MKK6, both of which increase p38alpha activity, each decreased transcription from the cyclin D1 promoter. Together, these data demonstrate that p38 negatively regulates cyclin D1 expression. We tested whether p38 regulates cyclin D1 expression via inhibition of extracellular signal-regulated kinase (ERK) activation. Chemical inhibitors of p38 induced modest ERK phosphorylation and activation. However, dominant negative MKK3 was insufficient to activate ERK, and active MKK3 and MKK6 did not attenuate platelet-derived growth factor-mediated ERK activation. These data are consistent with the notion that p38alpha negatively regulates cyclin D1 expression via an ERK-independent pathway.

Expression of tumor-suppressor genes interferon regulatory factor 1 and death-associated protein kinase in primitive acute myelogenous leukemia cells

Previous studies indicate that human acute myelogenous leukemia (AML) arises from a rare population of leukemic stem cells. Cells of this nature can initiate and maintain leukemic cell growth in both long-term cultures and nonobese diabetic/severe combined immune-deficient mice. To characterize the biology of primitive AML cells, gene expression screens were performed with 7 primary AML and 3 normal specimens. For each sample, stem cell populations (CD34(+)/CD38(-)) were isolated and used to synthesize radiolabeled complementary DNA (cDNA). AML vs normal probes were then hybridized to cDNA arrays containing genes related to cancer and apoptosis. Of approximately 1400 genes analyzed, 2 tumor-suppressor genes were identified that were overexpressed in all 7 of the AML CD34(+)/CD38(-) cell populations: death-associated protein kinase and interferon regulatory factor 1. Expression of each gene was confirmed by reverse-transcription polymerase chain reaction and immunoblot analysis. It is proposed that tumor-suppressor proteins play a role in the biology of primitive AML cells. (Blood. 2001;97:2177-2179)

Enhanced activity and level of protein kinase A in the spinal cord supernatant of diisopropyl phosphorofluoridate (DFP)-treated hens. Distribution of protein kinases and phosphatases in spinal cord subcellular fractions

Diisopropyl phosphorofluoridate (DFP) is a type I organophosphorus compound and produces delayed neurotoxicity (OPIDN) in adult hens. A single dose of DFP (1.7 mg/kg, s.c.) produces mild ataxia in hens in 7-14 days, which develops into severe ataxia or paralysis as the disease progresses. We have previously shown altered expression of several proteins (e.g. Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) alpha-subunit, tau, tubulin, neurofilament protein (NF), vimentin, GFAP) and an immediate early gene (e.g. c-fos) in DFP-treated hens. Here we show an increase in protein kinase A (PKA) protein level and activity in the spinal cord at 1-day and 5-days time periods after DFP administration. We also determined the protein levels of protein kinase C (PKC), CaM kinase II and several phosphatases (i.e. phosphatase 1 (PP1), phosphatase 2A (PP2A), phosphatase 2B (PP2B) in the spinal cord of DFP-treated hens after 1, 5, 10, and 20 days). There was increase in CaM kinase II alpha subunit level after 10 and 20 days of treatment, and decrease in PKC level at 1-day and 20-days time periods in spinal cord mitochondria. In contrast, the cerebrum, which is resistant to DFP-induced axonal degeneration, did not show change in PKA and CaM Kinase II levels at any time period DFP post-administration. No alteration was found in the protein levels of PP1, PP2A, and PP2B at any time period. An early induction in PKA, which is an important protein kinase in signal transduction, followed by that of CaM kinase might be contributing towards the development of OPIDN in DFP-treated hens.

Modulation of WNT-5A expression by actinonin: linkage of APN to the WNT-pathway?

Inhibition of alanyl-aminopeptidase gene expression or enzymatic activity compromises T cell proliferation and function. Molecular mechanisms mediating these effects are not known as yet. Applying the cDNA array technique we identified the proto-oncogen Wnt-5a strongly affected by APN-inhibition. Wnt-5a and other members of the Wnt family of secreted factors are implicated in cell growth and differentiation. Wnt-5a was moderately expressed in resting T cells, but strongly down-regulated in response to activation by OKT3/IL-4/IL-9. Actinonin increased Wnt-5a-mRNA contents as confirmed by RT-PCR. In addition, expression of GSK-3 beta, an inherent component of the Wnt-pathway, was found to be increased in response to activation, but suppressed by actinonin at both the mRNA and protein level. These findings may provide a rationale for the strong growth inhibitory effects resulting from an inhibition of alanyl aminopeptidase expression or activity.

Opposing actions of phosphatidylinositol 3-kinase and glycogen synthase kinase-3beta in the regulation of HSF-1 activity

Elevated temperatures activate the survival promoters Akt and heat shock factor-1 (HSF-1), a transcription factor that induces the expression of heat shock proteins (HSPs), such as HSP-70. Because neuronal mechanisms controlling these responses are not known, these were investigated in human neuroblastoma SH-SY5Y cells. Heat shock (45 degrees C) rapidly activated Akt, extracellular signal-regulated kinases 1 and 2 (ERK1/2), and p38, but only Akt was activated in a phosphatidylinositol 3-kinase (PI-3K)-dependent manner, as the PI-3K inhibitors LY294002 and wortmannin blocked Akt activation, but not ERK1/2 or p38 activation. Akt activation was not blocked by inhibition of p38 or ERK1/2, indicating the independence of these signaling systems. Heat shock treatment also caused a rapid increase in HSF-1 DNA binding activity that was partially dependent on PI-3K activity, as both the PI-3K inhibitors attenuated this response. Because Akt inhibits glycogen synthase kinase-3beta (GSK-3beta), an enzyme that facilitates cell death, we tested if GSK-3beta is a negative regulator of HSF-1 activation. Overexpression of GSK-3beta impaired heat shock-induced activation of HSF-1, and also reduced HSP-70 production, which was partially restored by the GSK-3beta inhibitor lithium. Thus, heat shock-induced activation of PI-3K and the inhibitory effect of GSK-3beta on HSF-1 activation and HSP-70 expression imply that Akt-induced inhibition of GSK-3beta contributes to the activation of HSF-1.

Sensing of osmotic pressure changes in tomato cells

Cells of tomato (Lycopersicon esculentum) growing in suspension gradually depleted their culture medium and caused a steady decrease in its osmolality. When confronted with a sudden change in medium osmolality (a hypo-osmotic or hyperosmotic shock), respectively, these cells responded with volume changes and stress symptoms such as rapid extracellular alkalinization, efflux of K(+)-ions, and induction of 1-aminocyclopropane-1-carboxylate synthase acid, the key enzyme of ethylene biosynthesis. This array of stress symptoms is well known from cultured plant cells treated with microbial elicitors. Compared with elicitor treatment, induction of responses by hyperosmotic shock was slow and occurred only after increases of approximately 200,000 Pa in osmotic pressure. In contrast, hypo-osmotic shock induced responses without measurable lag and faster than elicitor treatments. Measurable medium alkalinization was induced when medium osmolality was reduced by as little as approximately 10 mosmol, a change corresponding to only approximately 0.2 bar in osmotic pressure. Like treatment with elicitors, hypo-osmotic shock induced specific changes in protein phosphorylations as demonstrated by in vivo labeling with [(33)P]orthophosphate. Exposure of cells to consecutive up- and down-shifts in medium osmolality showed that sensing of osmotic changes occurred within seconds, whereas adaptation to new osmotic conditions proceeded over hours. In conclusion, suspension-cultured plant cells display rapid, easily measurable macroscopic responses to osmotic shock and provide an interesting model system to study osmoregulation, a key process in plant growth and development.

Synapses call the shots

Neuroscience research is shedding light on how neurons delegate their protein synthesis, shipping some messenger RNAs out to the dendrites, where they are translated to protein under the control of local synapses. Indeed, it appears that finely controlled, decentralized protein production may contribute to learning and memory in a way that neuroscientists could scarcely have imagined 20 years ago. As researchers presss on, they are filling in a picture of a complex loop of communication and supply, with synapses acting as local managers wielding more power than anyone might have imagined, to get what they need for carrying out the critical task of storing memories.

Involvement of Ca2+/calmodulin-dependent protein kinase II in neurite outgrowth induced by cAMP treatment and serum deprivation in a central nervous system cell line, CAD derived from rat brain

A central nervous system (CNS) cell line, CAD, is known to differentiate in the absence of serum. This cell line was found to differentiate by the treatment of cAMP. Expression of Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II) was induced to about 2-fold or more on day 1, and was continued at a high level for 5 days after the exposure to differentiating conditions. Neurite extension was stimulated from day 1 and continued for 5 days, suggesting that CaM kinase II activity is correlated with neurite outgrowth. Of the four distinct isoforms (alpha, beta, gamma, and delta) of the kinase, the delta isoform was the major isoform in CAD cells. The splicing pattern of this isoform in the differentiated cells differed from that in undifferentiated cells, suggesting that expression of CaM kinase II is regulated during neural differentiation.

The caM kinase, Pnck, is spatially and temporally regulated during murine mammary gland development and may identify an epithelial cell subtype involved in breast cancer

While screening for protein kinases expressed in the murine mammary gland, we identified previously a Ca2+/calmodulin-dependent kinase, Pnck, that is most closely related to CaMKI. In this report, we show that Pnck is temporally regulated during murine mammary development with highest levels of expression observed late in pregnancy, concomitant with the decreased cellular proliferation and terminal differentiation of the mammary epithelium. Consistent with this finding, Pnck is up-regulated in confluent mammary epithelial cells and is down-regulated as serum-starved cells are stimulated to reenter the cell cycle. In the mammary gland, Pnck is expressed in an epithelial-specific and markedly heterogeneous manner, suggesting that the expression of this kinase may be restricted to a particular mammary epithelial cell type. Potentially related to its heterogeneous in vivo expression pattern, Pnck expression is oncogene-associated in murine epithelial cell lines derived from mammary tumors arising in different transgenic mouse models of breast cancer; cell lines derived from mammary tumors initiated by c-myc or int-2/Fgf3 express Pnck, whereas cell lines initiated by neu or H-ras do not. In an analogous manner, expression of the human homologue of Pnck is restricted to a subset of human breast cancer cell lines. Moreover, PNCK was found to be highly overexpressed in a subset of human primary human breast cancers compared with benign mammary tissue. Together, our data suggest that Pnck may play a role in mammary development, and that expression of this kinase may be restricted to a mammary epithelial cell type that is transformed in a subset of human breast cancers.

Coordinate expression of Ca2+-ATPase slow-twitch isoform and of beta calmodulin-dependent protein kinase in phospholamban-deficient sarcoplasmic reticulum of rabbit masseter muscle

Modulation of sarcoplasmic reticulum (SR) Ca(2+) transport by endogenous calmodulin-dependent protein kinase II (CaM K II) involves covalent changes of regulatory protein phospholamban (PLB), as a common, but not the only mechanism, in limb slow-twitch muscles of certain mammalian species, such as the rabbit. Here, using immunofluorescent techniques in situ, and biochemical and immunological methods on the isolated SR, we have demonstrated that rabbit masseter, a muscle with a distinct embryological origin, lacks PLB. Accommodating embryological heterogeneity in the paradigm of neural-dependent expression of specific isogenes in skeletal muscle fibers, our results provide novel evidence for the differential expression in the SR of 72 kDa beta components of CaM K II, together with the expression of a slow-twitch sarcoendoplasmic reticulum Ca(2+)-ATPase isoform, both in limb muscle and in the masseter.

Wound-induced expression and activation of WIG, a novel glycogen synthase kinase 3

Glycogen synthase kinase 3 (GSK-3) is involved in the regulation of several physiological processes, including glycogen metabolism, protein synthesis, transcription factor activity, and developmental control. Although GSK-3-like genes have been isolated from plants, no function for any of these kinases has been defined. We report here that the alfalfa wound-induced gene (WIG, for wound-induced GSK-3), lencoding a functional plant GSK-3-like kinase, is activated when the alfalfa leaves are wounded. Although WIG transcripts are hardly detectable in mature leaves, WIG mRNA accumulates rapidly after wounding. Using a peptide antibody that specifically recognizes p53(WIG), we show that p53(WIG) kinase is activated immediately after wounding. Wound-induced activation of p53(WIG) kinase is a post-translational process, because the concentrations of p53(WIG) protein do not change in intact and wounded leaves, and inhibition of transcription or translation does not block activation by wounding. However, inactivation of p53(WIG) kinase, which usually occurs within 60 min after wounding, is dependent on transcription and translation of one or more protein factors. These data suggest that the WIG kinase is involved in wound signaling in plants.