Gene expression analysis of MAOA and the clock gene ARNTL in individuals with bipolar disorder compared to healthy controls.

INTRODUCTION: Circadian rhythms are associated with bipolar disorder (BD). This cross-sectional study aimed at investigating ARNTL and MAOA gene expression differences (1) between individuals with BD and controls, (2) between affective episodes, and (3) the relationship between ARNTL and MAOA expression. METHODS: ARNTL and MAOA gene expression in peripheral mononuclear blood cells were analysed from fasting blood samples (BD n = 81, controls n = 54) with quantitative real-time PCR operating on TaqMan® assays (normalised to 18S RNA expression). ANCOVAs corrected for age, sex, body mass index, and medication was used to evaluate expression differences and correlation analyses for the relation between ARNTL and MAOA expression. RESULTS: ARNTL gene expression differed between affective episodes (F(2,78) = 3.198, p = 0.047, Partial Eta2= 0.083), but not between BD and controls (n.s.). ARNTL and MAOA expression correlated positively in BD (r = 0.704, p < 0.001) and in controls (r = 0.932, p < 0.001). MAOA expression differed neither between BD and controls nor between affective episodes (n.s.). DISCUSSION: Clock gene expression changes were observed in different affective states of BD. More precisely, ARNTL gene expression was significantly higher in euthymia than in depression. ARNTL and MAOA gene expression correlated significantly in BD and in controls, which emphasises the strong concatenation between circadian rhythms and neurotransmitter breakdown.

The relationship between "Eyes Reading" ability and verbal memory in bipolar disorder.

In psychiatric disorders, neurocognitive impairments are prevalent and have been associated with poor outcome. Deficits in Theory of Mind (ToM, "mentalising") have also been observed in bipolar disorder (BD); however, the literature shows inconsistent data. The aim of this study was to explore ToM performance in a well-characterized sample of euthymic individuals with BD and its relationship with neurocognitive function. One hundred sixteen euthymic patients with BD between 18 and 74 years (mean age = 42.4, SD = 13.8) and 79 healthy controls (mean age = 39.8, SD = 16.5) were investigated with an extensive neurocognitive test battery (Trail Making Test A/B, d2 Test of Attention, Stroop Color-Word Test, California Verbal Learning Test, Multiple Choice Vocabulary Test). Additionally, all participants were given the Reading the Mind in the Eyes Test (RMET) to measure affective ToM, the ability to make assumptions about other people´s feelings. Overall, "Eyes Reading" performance was not impaired in individuals with BD compared with controls. However, a significant relationship between RMET and verbal memory in BD was shown, particularly in males. Data showed worse RMET performance in patients with memory deficits compared to patients without memory deficits and controls. Due to cross-sectional data, no conclusions can be made with respect to cause and effect.

Epigenetics of the molecular clock and bacterial diversity in bipolar disorder.

Objectives The gut microbiome harbors substantially more genetic material than our body cells and has an impact on a huge variety of physiological mechanisms including the production of neurotransmitters and the interaction with brain functions through the gut-brain-axis. Products of microbiota can affect methylation according to preclinical studies. The current investigation aimed at analyzing the correlation between gut microbiome diversity and the methylation of the clock gene ARNTL in individuals with Bipolar Disorder (BD). Methods Genomic DNA was isolated from fasting blood of study participants with BD (n = 32). The methylation analysis of the ARNTL CG site cg05733463 was performed by bisulfite treatment of genomic DNA with the Epitect kit, PCR and pyrosequencing. Additionally, DNA was extracted from stool samples and subjected to 16S rRNA sequencing. QIIME was used to analyze microbiome data. Results Methylation status of the ARNTL CpG position cg05733463 correlated significantly with bacterial diversity (Simpson index: r= -0.389, p = 0.0238) and evenness (Simpson evenness index: r= -0.358, p = 0.044). Furthermore, bacterial diversity differed significantly between euthymia and depression (F(1,30) = 4.695, p = 0.039). Discussion The results of our pilot study show that bacterial diversity differs between euthymia and depression. Interestingly, gut microbiome diversity and evenness correlate negatively with methylation of ARNTL, which is known to regulate monoamine oxidase A transcription. We propose that alterations in overall diversity of the gut microbiome represent an internal environmental factor that has an epigenetic impact on the clock gene ARNTL which is thought to be involved in BD pathogenesis.

Gender differences in the association between physical activity and cognitive function in individuals with bipolar disorder.

INTRODUCTION: Bipolar disorder (BD) is accompanied by a high number of comorbidities and associated with an overall increased mortality. Especially obesity, systemic inflammatory processes and cognitive deficits are highly prevalent and increase with the course of illness. Physical activity (PA) is associated with beneficial effects on somatic comorbidities such as obesity or cardiovascular disease in individuals without psychiatric disorder. Furthermore, PA might increase neurocognitive performance and reduce systemic inflammation. OBJECTIVE: The aim of the study was to investigate the association between PA and neurocognitive function in euthymic individuals suffering from BD. METHODS AND PARTICIPANTS: 120 individuals with BD, euthymic at test time, completed the self-reported International Physical Activity Questionnaire (IPAQ) assessing PA of the past seven days and were accordingly assigned to a specific activity category (low, moderate or vigorous). Furthermore, clinical parameters were gathered and cognitive tests analysing verbal-dependent intelligence, attention, executive functioning as well as memory were administered. RESULTS: Female individuals in the vigorous PA group performed significantly higher in most of the cognitive domains compared to females with moderate or low PA. In males, we only found a significant difference in one test for attention between moderate/vigorous and the low activity group. CONCLUSION: Differences between PA groups in cognitive performance in female individuals with BD were obvious in almost all cognitive domains. As cognitive deficits are strongly associated with a worse course of disease and outcome, PA might offer a concomitant therapy targeting not only somatic comorbidities such as obesity and cardiovascular disease, but also neurocognition.

Laccase-catalysed synthesis of coupling products of phenolic substrates in different reactors.

Substrate oxidation of aromatic substances by the enzyme laccase followed by a heteromolecular coupling with a co-substrate is a promising possibility for the synthesis of new compounds. To find a suitable reactor for the effective production of new compounds, the laccase-catalysed coupling of 3-(3,4-dihydroxyphenyl)propionic acid with 4-aminobenzoic acid was investigated as a model system. Based on the kinetic parameters, a mathematical model was used to predict the reaction yield and oxygen demand in a discontinuously stirred tank reactor and a continuously operated stirred tank reactor. Membrane processes were used for bubble-free aeration of the system and to recover the soluble enzyme.

Cyclic AMP regulates expression of the RI alpha subunit of cAMP-dependent protein kinase through an alternatively spliced 5' UTR.

The present study examines novel mechanisms that regulate levels of the RI alpha subunit of cAMP-dependent protein kinase. We found that RI alpha protein is induced threefold by 8-(4-chlorophenyl)thio-cAMP in hormone responsive rat Sertoli cells, while total RI alpha mRNA is not correspondingly induced. Two RI alpha mRNA isoforms with different 5' untranslated sequences (RI alpha 1a and RI alpha 1b) are produced from the RI alpha gene in Sertoli cells. Deletion/mutation analysis of the cAMP-response-element-containing promoter upstream of the RI alpha exon 1b revealed that while mutation of the cAMP response element had no effects on cAMP-mediated induction, a 73-bp region of the RI alpha exon 1b itself conferred a fivefold to eightfold induction of reporter activity to homologous and heterologous promoters. The responsiveness of this region was dependent on a sense orientation downstream of the promoter start sites and had no effect on reporter mRNA, indicating that the cAMP-mediated induction occurs at the post-transcriptional level. Modeling of the RI alpha 1b 5' UTR secondary structure revealed a 5' CAP-proximal, strong stem-loop presenting an element similar to multiple start-site element downstream-1 (GCTCGG) in the loop region. RNA-EMSAs performed with the labeled RI alpha 1b 5' UTR showed stabilization of a protein/RNA complex in extracts from 8-(4-chlorophenyl)thio-cAMP stimulated Sertoli cells. This complex was abolished by mutation of the multiple start-site element downstream-1-like element. Our findings indicate that there is a cAMP-mediated induction of RI alpha expression at the post-transcriptional level, dependent on the 5' UTR of RI alpha 1b mRNA.

Quantitative determination of Rap 1 activation in cyclic nucleotide-treated HL-60 leukemic cells: lack of Rap 1 activation in variant cells.

We have previously isolated variant HL-60 cells that are resistant to cGMP-induced differentiation and showed that they are deficient in proteolytic cleavage and/or carboxyl methylation of Rap 1A (J. Biol. Chem. 269, 32155 - 32161, 1994 and Oncogene 17, 2211 - 2233, 1998). We have now developed an enzyme-based method for assessing Rap 1 activation which is quantitative and provides a measurement of the per cent of Rap molecules in the active GTP-bound state. Using this method, we show that cAMP and cGMP analogs activate Rap 1 in parental HL-60 cells but not in the variant cells and that H-89, a cAMP-dependent protein kinase inhibitor, has no effect on cAMP-induced Rap 1 activation in parental cells. Thus, cAMP activation of Rap 1 in HL-60 cells is likely through a cAMP-regulated guanine nucleotide exchange factor (cAMP-GEF) and since cAMP does not activate Rap 1 in the variant cells, the data suggest that full post-translational processing of Rap 1 is necessary for cAMP-GEF activation of Rap 1. Activation of Rap 1 by cGMP analogs has not been previously found and suggests possible cross-talk between the NO/cGMP signal transduction pathway and Rap 1 signaling. Oncogene (2000) 19, 4029 - 4034.

Cell type-specific regulation of B-Raf kinase by cAMP and 14-3-3 proteins.

Cyclic AMP can either activate or inhibit the mitogen-activated protein kinase (MAPK) pathway in different cell types; MAPK activation has been observed in B-Raf-expressing cells and has been attributed to Rap1 activation with subsequent B-Raf activation, whereas MAPK inhibition has been observed in cells lacking B-Raf and has been attributed to cAMP-dependent protein kinase (protein kinase A)-mediated phosphorylation and inhibition of Raf-1 kinase. We found that cAMP stimulated MAPK activity in CHO-K1 and PC12 cells but inhibited MAPK activity in C6 and NB2A cells. In all four cell types, cAMP activated Rap1, and the 95- and 68-kDa isoforms of B-Raf were expressed. cAMP activation or inhibition of MAPK correlated with activation or inhibition of endogenous and transfected B-Raf kinase. Although all cell types expressed similar amounts of 14-3-3 proteins, approximately 5-fold less 14-3-3 was associated with B-Raf in cells in which cAMP was inhibitory than in cells in which cAMP was stimulatory. We found that the cell type-specific inhibition of B-Raf could be completely prevented by overexpression of 14-3-3 isoforms, whereas expression of a dominant negative 14-3-3 mutant resulted in partial loss of B-Raf activity. Our data suggest that 14-3-3 bound to B-Raf protects the enzyme from protein kinase A-mediated inhibition; the amount of 14-3-3 associated with B-Raf may explain the tissue-specific effects of cAMP on B-Raf kinase activity.

NO activation of fos promoter elements requires nuclear translocation of G-kinase I and CREB phosphorylation but is independent of MAP kinase activation.

We have shown that nitric oxide (NO) regulates c-fos gene expression via cGMP-dependent protein kinase (G-kinase), but NO's precise mechanism of action is unclear. We now demonstrate that: (1) NO targets two transcriptional elements in the fos promoter, i.e., the fos AP-1 binding site and the cAMP-response element (CRE); (2) NO activation of these two enhancer elements requires the CRE binding protein CREB because a dominant negative CREB fully inhibits NO transactivation of reporter genes whereas dominant negative Fos or CCAAT enhancer binding proteins have no effect; (3) CREB is phosphorylated by G-kinase in vitro and its phosphorylation increases in vivo when G-kinase is activated either directly by cGMP or indirectly by NO via soluble guanylate cyclase; (4) NO activation of fos promoter elements requires nuclear translocation of G-kinase but not activation of mitogen-activated protein kinases.

Nitric oxide and cGMP regulate gene expression in neuronal and glial cells by activating type II cGMP-dependent protein kinase.

Nitric oxide (NO) and cGMP have been implicated in many neuronal functions, including regulation of gene expression, but little is known about the downstream targets of NO/cGMP in the nervous system. We found that type II cGMP-dependent protein kinase (G-kinase), which is widely expressed in the brain, mediated NO- and cGMP-induced activation of the fos promoter in cells of neuronal and glial origin; the enzyme was ineffective in regulating gene expression in fibroblast-like cells. The effect of G-kinase II on gene expression did not require calcium uptake but was synergistically enhanced by calcium. G-kinase II was membrane associated and did not translocate to the nucleus; however, a soluble G-kinase II mutant translocated to the nucleus and regulated gene expression in fibroblast-like cells. Soluble G-kinase I also regulates fos promoter activity, but membrane targeting of G-kinase I prevented the enzyme from translocating to the nucleus and regulating transcription in multiple cell types, including glioma cells; this suggests that cell type-specific factor(s) that mediate the transcriptional effects of extranuclear G-kinase II are not regulated by G-kinase I. Our results suggest that G-kinase I and II control gene expression by different mechanisms and that NO effects on neuronal plasticity may involve G-kinase II regulation of gene expression.-Gudi, T., Hong, G. K.-P., Vaandrager, A. B., Lohmann, S. M., Pilz, R. B. Nitric oxide and cGMP regulate gene expression in neuronal and glial cells by activating type II cGMP-dependent protein kinase.

Transcriptional elongation of c-myb is regulated by NF-kappaB (p50/RelB).

High levels of c-myb expression are necessary for the proliferation of hematopoietic precursor cells whereas down-regulation of c-myb is required for terminal differentiation; this down-regulation occurs through a conditional block to transcriptional elongation in intron I. We previously observed that cAMP analogs prevented the late down-regulation of c-myb during hexamethylene bisacetamide (HMBA)-induced differentiation of murine erythroleukemia (MEL) cells and blocked differentiation; this correlated with the induction of NF-kappaB (p50/RelB) complexes which were shown to bind to NF-kappaB recognition sites flanking the transcriptional pause site of c-myb. We now selected stably-transfected MEL cells which overexpressed p50, RelB or both at levels similar to those induced by cAMP to determine whether these NF-kappaB proteins regulate c-myb expression in intact cells. We demonstrate that transcriptionally active NF-kappaB (p50/RelB) complexes, but not p50 or RelB alone, prevented the early and late down-regulation of c-myb mRNA and increased c-myb transcriptional elongation in HMBA-induced MEL cells. The increase in c-myb expression was sufficient to block erythroid differentiation and allow continuous proliferation of cells in the presence of HMBA. Steady-state c-myb mRNA levels in untreated cells were not affected by overexpression of NF-kappaB, suggesting that p50/RelB specifically modulated the efficiency of transcriptional attenuation during MEL cell differentiation.

Nitric oxide regulation of gene transcription via soluble guanylate cyclase and type I cGMP-dependent protein kinase.

Nitric oxide (NO) regulates the expression of multiple genes but in most cases its precise mechanism of action is unclear. We used baby hamster kidney (BHK) cells, which have very low soluble guanylate cyclase and cGMP-dependent protein kinase (G-kinase) activity, and CS-54 arterial smooth muscle cells, which express these two enzymes, to study NO regulation of the human fos promoter. The NO-releasing agent Deta-NONOate (ethanamine-2,2'-(hydroxynitrosohydrazone)bis-) had no effect on a chloramphenicol acetyltransferase (CAT) reporter gene under control of the fos promoter in BHK cells transfected with an empty vector or in cells transfected with a G-kinase Ibeta expression vector. In BHK cells transfected with expression vectors for guanylate cyclase, Deta-NONOate markedly increased the intracellular cGMP concentration and caused a small (2-fold) increase in CAT activity; the increased CAT activity appeared to be from cGMP activation of cAMP-dependent protein kinase. In BHK cells co-transfected with guanylate cyclase and G-kinase expression vectors, CAT activity was increased 5-fold in the absence of Deta-NONOate and 7-fold in the presence of Deta-NONOate. Stimulation of CAT activity in the absence of Deta-NONOate appeared to be largely from endogenous NO since we found that: (i) BHK cells produced high amounts of NO; (ii) CAT activity was partially inhibited by a NO synthase inhibitor; and (iii) the inhibition by the NO synthase inhibitor was reversed by exogenous NO. In CS-54 cells, we found that NO increased fos promoter activity and that the increase was prevented by a guanylate cyclase inhibitor. In summary, we found that NO activates the fos promoter by a guanylate cyclase- and G-kinase-dependent mechanism.

Deficient post-translational processing of Rap 1A in variant HL-60 cells.

Variant HL-60 cells resistant to differentiation induced by nitroprusside and cGMP analogs have normal guanylate cyclase and cGMP-dependent protein kinase (G-kinase) activity (J. Biol. Chem. 269, 32155-32161, 1994). We found decreased phosphorylation of a low molecular weight protein (pp23) in the variant cells and by co-migration on two-dimensional polyacrylamide gels, phosphopeptide mapping, immunoprecipitation and immunoblotting, we showed that pp23 was one of three post-translationally modified forms of Rap 1A expressed in HL-60 cells. Using an in vitro transcription/translation system, we studied each of the posttranslational processing steps of Rap 1A and we showed that pp23 represented fully processed Rap 1A. By immunoprecipitation, immunoblotting and 35S-methionine/cysteine incorporation, we showed that the variant cells were deficient in pp23, and thus in fully processed Rap 1A, but that these cells did express normal amounts of completely unprocessed Rap 1A and geranylgeranylated Rap 1A; the lack of Rap 1A processing beyond geranylgeranylation in the variant cells was not secondary to a change in Rap 1A's amino acid sequence. The variant cells had normal carboxyl methyltransferase activity suggesting they are deficient in proteolytic cleavage of Rap 1A. The deficient post-translational processing of Rap 1A had no effect on Rap 1A's subcellular distribution and we found no evidence for altered post-translational processing of H-Ras.

Cyclic-GMP-dependent protein kinase inhibits the Ras/Mitogen-activated protein kinase pathway.

Agents which increase the intracellular cyclic GMP (cGMP) concentration and cGMP analogs inhibit cell growth in several different cell types, but it is not known which of the intracellular target proteins of cGMP is (are) responsible for the growth-suppressive effects of cGMP. Using baby hamster kidney (BHK) cells, which are deficient in cGMP-dependent protein kinase (G-kinase), we show that 8-(4-chlorophenylthio)guanosine-3', 5'-cyclic monophosphate and 8-bromoguanosine-3',5'-cyclic monophosphate inhibit cell growth in cells stably transfected with a G-kinase Ibeta expression vector but not in untransfected cells or in cells transfected with a catalytically inactive G-kinase. We found that the cGMP analogs inhibited epidermal growth factor (EGF)-induced activation of mitogen-activated protein (MAP) kinase and nuclear translocation of MAP kinase in G-kinase-expressing cells but not in G-kinase-deficient cells. Ras activation by EGF was not impaired in G-kinase-expressing cells treated with cGMP analogs. We show that activation of G-kinase inhibited c-Raf kinase activation and that G-kinase phosphorylated c-Raf kinase on Ser43, both in vitro and in vivo; phosphorylation of c-Raf kinase on Ser43 uncouples the Ras-Raf kinase interaction. A mutant c-Raf kinase with an Ala substitution for Ser43 was insensitive to inhibition by cGMP and G-kinase, and expression of this mutant kinase protected cells from inhibition of EGF-induced MAP kinase activity by cGMP and G-kinase, suggesting that Ser43 in c-Raf is the major target for regulation by G-kinase. Similarly, B-Raf kinase was not inhibited by G-kinase; the Ser43 phosphorylation site of c-Raf is not conserved in B-Raf. Activation of G-kinase induced MAP kinase phosphatase 1 expression, but this occurred later than the inhibition of MAP kinase activation. Thus, in BHK cells, inhibition of cell growth by cGMP analogs is strictly dependent on G-kinase and G-kinase activation inhibits the Ras/MAP kinase pathway (i) by phosphorylating c-Raf kinase on Ser43 and thereby inhibiting its activation and (ii) by inducing MAP kinase phosphatase 1 expression.

Decreased phosphorylation of a low molecular weight protein by cGMP-dependent protein kinase in variant HL-60 cells resistant to nitric oxide- and cGMP-induced differentiation.

We previously described the isolation of a variant subline of HL-60 cells that does not differentiate in response to nitric oxide (NO)-generating agents or to cGMP analogs. The variant cells have normal guanylate cyclase activity and normal NO-induced increases in the intracellular cGMP concentration. We now show that the variant cells have normal cGMP-dependent protein kinase (G-kinase) activity, both by an in vitro and in vivo assay, and using two-dimensional gel electrophoresis we have identified six G-kinase substrates in the parental cells. Of these six proteins, we found considerably less phosphorylation of one of the proteins in the variant cells than in parental cells, both in vitro and in intact cells, and by 35S-methionine/35S-cysteine incorporation we found much less of this protein in the variant cells than in parental cells. The protein is a shared substrate of cAMP-dependent protein kinase (A-kinase); since cAMP analogs still induce differentiation of the variant cells, it appears that the NO/cGMP/G-kinase and cAMP/A-kinase signal transduction pathways share some but not all of the same target proteins in inducing differentiation of HL-60 cells.

Regulation of the erythroid transcription factor NF-E2 by cyclic adenosine monophosphate-dependent protein kinase.

Activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (A-kinase) promotes hemoglobin synthesis in several erythropoietin-dependent cell lines, whereas A-kinase-deficient murine erythroleukemia (MEL) cells show impaired hemoglobin production; A-kinase may regulate the erythroid transcription factor NF-E2 by directly phosphorylating its p45 subunit or by changing p45 interactions with other proteins. We have mapped the major A-kinase phosphorylation site of p45 to Ser(169); Ala substitution for Ser(169) resulted in a protein that was no longer phosphorylated by A-kinase in vitro or in vivo. The mutant protein formed NF-E2 complexes that bound to DNA with the same affinity as wild-type p45 and functioned normally to restore beta-globin gene expression in a p45-deficient MEL cell line. Transactivation properties of the (Ser (169)--> Ala) mutant p45 were also indistinguishable from wild-type p45 when Gal4-p45 fusion constructs were tested with a Gal4-dependent reporter gene. Transactivation of the reporter by both mutant and wild-type p45 was significantly enhanced when A-kinase was activated by membrane-permeable cAMP analogs or when cells were cotransfected with the catalytic subunit of A-kinase. Stimulation of p45 transactivation by A-kinase required only the N-terminal transactivation domain of p45, suggesting that A-kinase regulates the interaction of p45 with downstream effectors.

cAMP-induced NF-kappaB (p50/relB) binding to a c-myb intronic enhancer correlates with c-myb up-regulation and inhibition of erythroleukemia cell differentiation.

During hexamethylene bisactamide (HMBA)-induced differentiation of murine erythroleukemia (MEL) cells erythroid genes are transcriptionally activated while c-myb and several other nuclear proto-oncogenes are down-regulated. Differentiation is inhibited by cAMP analogues and the adenyl cyclase-stimulating agent forskolin. We found that these drugs prevented the late down-regulation of c-myb which is known to be critical for MEL cell differentiation. Since the increase in c-myb mRNA levels was due to increased mRNA transcription, we examined the transcription factors NF-kappaB and AP-1 which have been implicated in the regulation of c-myb expression. Binding of MEL cell nuclear proteins to a NF-kappaB recognition sequence in c-myb intron I was strongly induced by 8-Br-cAMP or forskolin; induction was delayed and correlated with the up-regulation of c-myb. The cAMP-induced NF-kappaB complex contained p50 and RelB; in co-transfection assays, p50 and RelB transactivated a reporter construct containing the c-myb intronic NF-kappaB site upstream of a minimal promoter. 8-Br-cAMP and forskolin also increased the DNA binding activity of AP-1 complexes containing JunB, JunD and c-Fos in MEL cells which could cooperate with NF-kappaB. We conclude that inhibition of MEL cell differentiation by pharmacological doses of cAMP can be explained by the up-regulation of c-myb which is mediated, at least in part, by NF-kappaB p50/RelB heterodimers.

Regulation of gene expression by cyclic GMP-dependent protein kinase requires nuclear translocation of the kinase: identification of a nuclear localization signal.

We recently demonstrated that cyclic GMP (cGMP)-dependent protein kinase (G-kinase) activates the human fos promoter in a strictly cGMP-dependent manner (T. Gudi et al., J. Biol. Chem. 271:4597-4600, 1996). Here, we demonstrate that G-kinase translocates to the nucleus by an active transport mechanism which requires a nuclear localization signal (NLS) and is regulated by cGMP. Immunofluorescent staining of G-kinase was predominantly cytoplasmic in untreated cells, but intense nuclear staining appeared in 8-bromo (Br)-cGMP-treated cells. We identified a putative NLS in the G-kinase ATP binding domain which resembles the NLS of the interleukin-1alpha precursor. Fusion of the G-kinase NLS to the N terminus of beta-galactosidase produced a chimeric protein which localized to the nucleus. Mutation of a single amino acid residue (K407-->E) within the G-kinase NLS produced an enzyme with normal cGMP-dependent activity in vitro which did not translocate to the nucleus and did not transactivate the fos promoter in the presence of 8-Br-cGMP in vivo. In contrast, N-terminally truncated versions of G-kinase with constitutive, cGMP-independent activity in vitro localized to the nucleus and transactivated the fos promoter in the absence of 8-Br-cGMP. These results indicate that nuclear localization of G-kinase is required for transcriptional activation of the fos promoter and suggest that a conformational change of the kinase, induced by cGMP binding or by removal of the N-terminal autoinhibitory domain, functionally activates an otherwise cryptic NLS.

A low molecular weight substance purified from human placenta inhibits cAMP-dependent protein kinase and activates protein kinase C.

We have purified from human placenta a low molecular mass substance that inhibits cAMP-dependent protein kinase and activates protein kinase C. This protein kinase regulator was purified in three steps: (1) homogenizing placentas in chloroform/methanol and extracting the regulator into water; (2) eluting a strong anion exchange high performance liquid chromatography (HPLC) column with a quaternary gradient; and (3) eluting a reversed-phase HPLC column with a binary gradient. The regulator was found to be highly purified by HPLC, thin-layer chromatography (TLC) and laser desorption ionization mass spectrometry with a molecular mass of 703 Daltons by the latter procedure. The physical and biochemical properties of this protein kinase regulator suggest that it is a phospholipid but it did not co-elute by HPLC or by TLC with any of the known phospholipid activators of protein kinase C.