Regulation of ion channel localization and phosphorylation by neuronal activity

Voltage-dependent Kv2.1 K(+) channels, which mediate delayed rectifier Kv currents (I(K)), are expressed in large clusters on the somata and dendrites of principal pyramidal neurons, where they regulate neuronal excitability. Here we report activity-dependent changes in the localization and biophysical properties of Kv2.1. In the kainate model of continuous seizures in rat, we find a loss of Kv2.1 clustering in pyramidal neurons in vivo. Biochemical analysis of Kv2.1 in the brains of these rats shows a marked dephosphorylation of Kv2.1. In cultured rat hippocampal pyramidal neurons, glutamate stimulation rapidly causes dephosphorylation of Kv2.1, translocation of Kv2.1 from clusters to a more uniform localization, and a shift in the voltage-dependent activation of I(K). An influx of Ca(2+) leading to calcineurin activation is both necessary and sufficient for these effects. Our finding that neuronal activity modifies the phosphorylation state, localization and function of Kv2.1 suggests an important link between excitatory neurotransmission and the intrinsic excitability of pyramidal neurons.

Convergent and divergent signaling mechanisms of growth cone collapse by ephrinA5 and slit2

EphrinA5 and slit2 are important repulsive guidance cues in the developing retinotectal system. Both ephrinA5 and slit2 cause growth cone collapse of embryonic chick retinal ganglion growth cones cultured on EHS laminin. However, the signaling mechanism that these guidance cues initiate to cause collapse remains unclear. Here we provide evidence that while both ephrinA5 and slit2 cause collapse in morphologically similar ways, the intracellular signaling leading to the collapse involves shared as well as divergent paths. Pharmacological inhibition of either phosphatidylinositol 3-kinase (PI3K) or src family kinases prevented both ephrinA5-mediated and slit2-mediated growth cone collapse. In contrast, the inhibition of nonclassical protein kinase C (PKC) isoforms blocked ephrinA5-mediated collapse, but did not interfere with slit2-mediated collapse. PI3K was copurified by affinity chromatography with either the ephrinA5 receptors (ephAs) or the slit2 receptor (roundabout). Colocalization studies have also shown that src family kinase members are recruited to the ephA and roundabout receptors upon activation. In contrast, PKC members are recruited to the ephA receptors, but not to the roundabout receptors, upon activation. This demonstrates distinct points of convergence and divergence between the two signaling molecules, ephrinA5 and slit2, and their repulsive guidance in the chick retinotectal system.

The response of human natural killer cells to interleukin-2

Natural killer cells play a key role in the defence of organisms against virus infections and in the control of tumor onset. Interleukin-2 is a multifunctional inflammatory cytokine able to activate natural killer cells, essentially inducing cell proliferation, lymphokine-activated-killer cell generation and cytokine production. Here we discuss some signaling events generated by interleukin-2 in the cell nucleus of primary human natural killer cells, specifically focusing on the lipid signal transduction and the induction of the cyclic adenosine-5'-monophosphate response element binding protein transcription factor. The implications of these nuclear events in the response of natural killer cells to interleukin-2 are also discussed.

Glucose transporter GLUT8 translocation in neurons is not insulin responsive

We examined the subcellular distribution of a novel glucose transporter isoform (GLUT8) in murine N2A neuroblastoma cells. Exogenous expression of GLUT8-green fluorescent protein (GFP) DNA constructs mimicked the endogenous GLUT8 localization to intracellular vesicles and minimally to the Giantin-positive Golgi. This distribution was unlike the distributions of endogenous GLUT1 and GLUT3 (predominant neuronal isoform), which were limited predominantly to the plasma membrane and minimal in the cytoplasm. Although GLUT4-GFP (insulin responsive isoform) was expressed transiently, no endogenous GLUT4 was detected in N2A cells. By employing stable transfectants that expressed GLUT8-GFP, the effect of insulin and insulin-like growth factor-I, potassium chloride (depolarized state), and 3% oxygen on translocation of GLUT8 to the plasma membrane of N2A cells was examined immunohistochemically and by subfractionation, followed by Western blot analysis. None of these agents translocated GLUT8 to the plasma membrane. However, when the internalization dileucine motif (L(12,13)) of GLUT8 was mutated to a dialanine motif (A(12,13)), GLUT8 colocalized with GLUT3 in the plasma membrane. We conclude that GLUT8 translocation to the N2A cellular plasma membrane is not observed secondary to the various stimuli investigated. Mutation of the N-terminal dileucine motif led to constitutive GLUT8 localization in the plasma membrane. The endogenous stimulus required for translocating neuronal GLUT8 is unknown. This stimulus, which is necessary for uncoupling the "cytoplasmic vesicular anchor" of GLUT8, would be crucial for its glucose-transporting function.

5-HT1A-mediated promotion of mitogen-activated T and B cell survival and proliferation is associated with increased translocation of NF-kappaB to the nucleus

Mitogenic activation of T and B lymphocytes induces expression of the 5-HT(1A) receptor through an NF-kappaB-dependent signaling pathway. In the present study, it is shown that serotonin (5-HT), as well as the selective 5-HT(1A) receptor agonist R-DPAT, increase cell survival and S phase transition in mouse splenocytes stimulated by T or B cell mitogens. Further examination of the mechanisms underlying increased cell survival revealed that 5-HT and R-DPAT inhibited apoptotic cell death, assessed both by soluble DNA content, internucleosomal DNA cleavage, and hypodiploid DNA content. Additionally, 5-HT and R-DPAT treatment increased intranuclear levels of the p50 and p65 subunits of NF-kappaB. Potentiation by 5-HT and R-DPAT of mitogen-activated cell survival, S phase transition, and nuclear localization of NF-kappaB, as well as inhibition of apoptosis, were all reversed by the selective 5-HT(1A) receptor antagonist WAY-100635. These results indicate that 5-HT(1A)-mediated promotion of cell survival and proliferation of mitogen-activated T and B lymphocytes is associated with increased translocation of NF-kappaB in the nucleus.

Age-dependent increase of NF-κB translocation and PDGF-B expression in aortic endothelial cells of hypercholesterolemic rats

The objective of this study was to determine whether there was an age-dependent difference in promoting nuclear translocation of NF-kappa B and platelet derived growth factor expression in aortic endothelial cells between two groups of Wistar rats of 2 and 10 months in age, respectively, accompanied by hypercholesterolemia. The serum cholesterol levels became significantly higher in the older rats after taking a cholesterol-enriched diet for 16 weeks (129.3+/-11.9 vs. 194.5+/-22.6 mg/dl, P<0.01). The increase in total cholesterol levels were due to an elevation of LDL cholesterol since serum HDL cholesterol concentrations were similar in rats on either a high cholesterol- or a standard diet. Immunohistologic staining revealed nuclear translocation of NF-kappaB in aortic endothelial cells of rats was responsible for a high cholesterol uptake by cells. PDGF-B production was also increased in the endothelial cells of these animals as identified by situ hybridization and immunohistologic staining. Interestingly, the intensity of PDGF-B expression in the 10 months old rats was markedly higher than those of 2 months old. Taken together, these findings provide evidence that there was an elevation of serum cholesterol levels coinciding with an increase of PDGF-B expression in older rats, in which NF-kappaB might be an important transcription factor in mediating a hypercholesterolemia-induced PDGF-B expression.

Id4 is deregulated by a t(6;14)(p22;q32) chromosomal translocation in a B-cell lineage acute lymphoblastic leukemia

BACKGROUND AND OBJECTIVES

Chromosome translocations resulting in gene overexpression are commonly associated with lymphoid neoplasia. Enhancer elements of the immunoglobulin or T-cell receptor (TCR) loci are abnormally located in the vicinity of the entire coding sequences of genes which exert an influence on the normal maturation and differentiation program of lymphoid cells.

DESIGN AND METHODS

A patient who presented with a B-cell lineage acute lymphoblastic leukemia had a t(6;14)(p22;q32). Cytogenetic and molecular findings confirmed the involvement of IgH. Molecular cloning of the breakpoint revealed that this was located near the coding sequence of the Id4 gene, a helix-loop-helix (HLH) inhibitor protein. Alu-repeated sequences at the 6p22 end flanked a short stretch of 10 bases shared by the 6p22 and 14q32 ends, suggesting that a deletion or a looping-Alu mediated mispairing mechanism may lead to this chromosome translocation.

RESULTS

Northern blot and real-time polymerase chain reaction analyses showed that the Id4 mRNA was abnormally overexpressed in this case. Only the two smaller Id4 mRNA products were detected (1.6 and 1.1 kb). Immunohistochemical analysis of Id4 protein was also assayed in a series of hematologic malignancies. Marked overexpression was found in two cases of T-cell prolymphocytic leukemias and in four B-cell lineage acute lymphoblastic leukemia including one case with the t(8;14) and another case with a p53 mutation.

INTERPRETATION AND CONCLUSIONS

The Id4 gene may behave as an oncogene in some human leukemias, perhaps through its capacity to sequester specific B-cell transcription factors. A genetic recombination between Alu-repeated sequences may not be the exclusive mechanism of generating pathogenic chromosomal translocations.

Robertsonian translocations: mechanisms of formation, aneuploidy, and uniparental disomy and diagnostic considerations

Robertsonian translocations (ROBs) are rearrangements of the acrocentric chromosomes 13-15 and 21-22. Cytologically, ROBs between homologous chromosomes cannot be distinguished from isochromosomes that originate through duplication of a single homologue. Both types of rearrangements can be involved in aneuploidy. A conceptus with a trisomy or a monosomy can be rescued, and in a proportion of cases, a uniparental disomy (UPD) would result. If there are regions of genome imprinting on a uniparental chromosome pair, phenotypic consequences can result. Chromosomes 14 and 15 are imprinted, and UPD of these are known to result in abnormalities. Thus, prenatal testing should be considered in all pregnancies when one of the parents is a balanced carrier of a ROB because of the risk for aneuploidy, and UPD testing should be considered in fetuses found to carry a balanced ROB or isochromosome that involves chromosomes 14 or 15. Additionally, infants or children with congenital anomalies who carry a ROB should also be considered for UPD testing.

The pathogenetic role of oncogenes deregulated by chromosomal translocation in B-cell malignancies

Chromosomal translocations involving the immunoglobulin (IG) loci play a pivotal role in the pathogenesis of many subtypes of mature B-cell malignancy. Although all the common IG translocations have been cloned, cloning of rare but nonetheless recurrent translocations continues to allow identification of genes of importance to the development of both normal and malignant B-cells. Clustering of breakpoints within the IG gene segments has allowed development of polymerase chain reaction methods that facilitate cloning. IG translocations result in overexpression of a wide variety of genes ranging from cell surface receptors to transcriptional repressors. Genes recently shown to be involved in such translocations include BCL11A and MALT1. As with the acute leukemias, different translocations in B-cell lymphomas may target different proteins that interact directly. A common endpoint for several translocations is activation of the nuclear factor kappaB pathway. Analysis of the mechanisms of transformation may define new therapeutic strategies.

Mitochondrial biogenesis and the role of the protein import pathway

PURPOSE

The importance of the mitochondrial protein import pathway, discussed relative to other steps involved in the overall biogenesis of the organelle, are reviewed.

RESULTS

Mitochondrial biogenesis is a product of complex interactions between the nuclear and mitochondrial genomes. Signaling pathways, such as those activated by exercise, initiate the activation of transcription factors that increase the production of mRNA from nuclear and mitochondrial DNA. Nuclear gene products are translated in the cytosol as precursor proteins with inherent targeting signals. These precursor proteins interact with molecular chaperones that direct them to the import machinery of the outer membrane (Tom complex). The precursor is unfolded and transferred through the outer membrane, across the intermembrane space to the mitochondrial inner membrane translocases (Tim complex). Intramitochondrial components (mtHSP70) pull the precursor into the matrix, cleave off the targeting sequence (mitochondrial processing peptidase), and refold the protein (HSP60, cpn10) into its mature conformation. Physiological stressors such as contractile activity and thyroid hormone accelerate protein import into the mitochondria, coincident with an increase in the expression of some components of the import machinery. This is important for the overall expansion of the mitochondrial reticulum. Conversely, impairments in the import process can be a cause of mitochondrial dysfunction and disease.

CONCLUSIONS

Efforts to further characterize the components of the import machinery, to define the role of specific machinery components on the import rate, and to examine protein import function in a variety of mitochondrial diseases are warranted.

Inhibition of NF-kappa B binding correlates with increased nuclear glucocorticoid receptor levels in acute alcohol-treated human monocytes

BACKGROUND

Acute alcohol treatment blocks inflammatory cytokines via inhibition of NF-kappaB in monocytes in the presence of ongoing IkappaBalpha degradation, suggesting regulation of NF-kappaB activation downstream of IkappaBalpha degradation. DNA binding of NF-kappaB has been suggested to be regulated by other nuclear regulatory factors, including the glucocorticoid receptor (GR). Here, we show for the first time that acute alcohol (25 mM) exposure modulates GR activation in monocytes.

METHODS

Human peripheral blood monocytes were treated with lipopolysaccharide (LPS) in the presence or absence of alcohol (25 mM) for 1 hour. Nuclear GR levels were estimated by Western blotting and NFkappaB activation was studied in the same extracts by gel shift analysis (EMSA). Cells were stimulated with 1 microM of Dex to be used as positive control for GR activation. GR/GRE binding was also determined in nuclear extracts by EMSA. IkappaBalpha mRNA known to be induced by GR/GRE activation was studied in total RNA extracts by the SuperArray method (SuperArray Inc., Bethesda, MD).

RESULTS

LPS is a potent inducer of GR nuclear translocation and GR binding to the glucocorticoid response element (GRE). Acute alcohol treatment both induced (p < 0.05) and augmented (p < 0.05) LPS-stimulated GR nuclear levels. However, alcohol inhibits LPS-induced (nonligand bound) GR/GRE binding activity in monocytes. This inhibition of GR transactivation by alcohol was further confirmed by decreased expression (40%) of a target gene, IkappaBalpha. Thus, alcohol treatment increases nonligand-bound nuclear GR, but inhibits its transactivation function. Ligand-induced GR/GRE binding was decreased in alcohol-treated monocytes. Inhibition of ligand-induced GR/GRE binding by alcohol exposure is likely due to cytoplasmic retention of the GR.

CONCLUSIONS

Our results show that acute alcohol exposure inhibits GR in monocytes by differently affecting ligand- and nonligand-induced GR nuclear translocation. These data also suggest that acute alcohol regulates GR activation in monocytes concomitant to inhibition of NF-kappaB activation.

Cholesterol and steroid synthesizing smooth endoplasmic reticulum of adrenocortical cells contains high levels of translocation apparatus proteins

Steroid-secreting cells possess abundant smooth endoplasmic reticulum whose membranes contain many enzymes involved in sterol and steroid synthesis. In this study we demonstrate that adrenal smooth microsomal subfractions enriched in these membranes also possess high levels of proteins belonging to the translocation apparatus, proteins previously assumed to be confined to morphologically identifiable rough endoplasmic reticulum (RER). We further demonstrate that these smooth microsomal subfractions are capable of effecting the functions of these protein complexes: co-translational translocation, signal peptide cleavage and N-glycosylation of newly synthesized polypeptides. We hypothesize that these elements participate in regulating the levels of ER-targeted membrane proteins involved in cholesterol and steroid metabolism in a sterol-dependent and hormonally-regulated manner.

Gene content and function of the ancestral chromosome fusion site in human chromosome 2q13-2q14.1 and paralogous regions

Various portions of the region surrounding the site where two ancestral chromosomes fused to form human chromosome 2 are duplicated elsewhere in the human genome, primarily in subtelomeric and pericentromeric locations. At least 24 potentially functional genes and 16 pseudogenes reside in the 614-kb of sequence surrounding the fusion site and paralogous segments on other chromosomes. By comparing the sequences of genomic copies and transcripts, we show that at least 18 of the genes in these paralogous regions are transcriptionally active. Among these genes are new members of the cobalamin synthetase W domain (CBWD) and forkhead domain FOXD4 gene families. Copies of RPL23A and SNRPA1 on chromosome 2 are retrotransposed-processed pseudogenes that were included in segmental duplications; we find 53 RPL23A pseudogenes in the human genome and map the functional copy of SNRPA1 to 15qter. The draft sequence of the human genome also provides new information on the location and intron-exon structure of functional copies of other 2q-fusion genes (PGM5, retina-specific F379, helicase CHLR1, and acrosin). This study illustrates that the duplication and rearrangement of subtelomeric and pericentromeric regions have functional relevance to human biology; these processes can change gene dosage and/or generate genes with new functions.

A role for protein kinase C during rat egg activation

Upon sperm-egg interaction, an increase in intracellular calcium concentration ([Ca(2+)](i)) is observed. Several studies reported that cortical reaction (CR) can be triggered not only by a [Ca(2+)](i) rise but also by protein kinase C (PKC) activation. Because the CR is regarded as a Ca(2+)-dependent exocytotic process and because the calcium-dependent conventional PKCs (cPKC) alpha and beta II are considered as exocytosis mediators in various cell systems, we chose to study activation of the cPKC in the rat egg during in vivo fertilization and parthenogenetic activation. By using immunohistochemistry and confocal microscopy techniques, we demonstrated, for the first time, the activation of the cPKC alpha, beta I, and beta II during in vivo fertilization. All three isozymes examined presented translocation to the egg's plasma membrane as early as the sperm-binding stage. However, the kinetics of their translocation was not identical. Activation of cPKC alpha was obtained by the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) or by 1-oleoyl-2-acetylglycerol (OAG) but not by the calcium ionophore ionomycin. PKC alpha translocation was first detected 5-10 min after exposure to TPA and reached a maximum at 20 min, whereas in eggs activated by OAG, translocation of PKC alpha was observed almost immediately and reached a maximum within 5 min. These results suggest that, although [Ca(2+)](i) elevation on its own does not activate PKC alpha, it may accelerate OAG-induced PKC alpha activation. We also demonstrate a successful inhibition of the CR by a myristoylated PKC pseudosubstrate (myrPKCPsi), a specific PKC inhibitor. Our study suggests that exocytosis can be triggered independently either by a [Ca(2+)](i) rise or by PKC.

Evidence for position effects as a variant ETV6-mediated leukemogenic mechanism in myeloid leukemias with a t(4;12)(q11-q12;p13) or t(5;12)(q31;p13)

The ETV6 gene (first identified as TEL) is a frequent target of chromosomal translocations in both myeloid and lymphoid leukemias. At present, more than 40 distinct translocations have been cytogenetically described, of which 13 have now also been characterized at the molecular level. These studies revealed the generation of in-frame fusion genes between different domains of ETV6 and partner genes encoding either kinases or transcription factors. However, in a number of cases-including a t(6;12)(q23;p13), the recurrent t(5;12)(q31;p13), and some cases of the t(4;12)(q11-q12;p13) described in this work-functionally significant fusions could not be identified, raising the question as to what leukemogenic mechanism is implicated in these cases. To investigate this, we have evaluated the genomic regions at 4q11-q12 and 5q31, telomeric to the breakpoints of the t(4;12)(q11-q12;p13) and t(5;12)(q31;p13). The homeobox gene GSH2 at 4q11-q12 and the IL-3/CSF2 locus at 5q31 were found to be located close to the respective breakpoints. In addition, GSH2 and IL-3 were found to be ectopically expressed in the leukemic cells, suggesting that expression of GSH2 and IL-3 was deregulated by the translocation. Our results indicate that, besides the generation of fusion transcripts, deregulation of the expression of oncogenes could be a variant leukemogenic mechanism for translocations involving the 5' end of ETV6, especially for those translocations lacking functionally significant fusion transcripts.

Jun, Fos and Krox in the thalamus after C-fiber stimulation: coincident-input-dependent expression, expression across somatotopic boundaries, and nucleolar translocation

Expression of the inducible transcription factors Jun, Fos and Krox is commonly used to map neurons in the brain that are activated by sensory inputs. However, some neurons known to be electrically excited by such inputs do not always express these factors. In particular, stimulation of hindlimb sensory nerve C-fibers induces expression of c-Fos in the medial thalamus (the mediodorsal, intermediodorsal, centrolateral and centromedial), but not in the lateral thalamus (the ventroposterolateral, ventroposteromedial and posterior group). We hypothesized that c-Fos expression might only occur in these lateral areas after more complex stimulation patterns, or that only other transcription factors can be induced in these areas by such stimuli. Thus we examined the effects of single, repeated and coincident C-fiber inputs on expression of six inducible transcription factors in the medial, lateral and reticular thalamus of the rat. A weak C-fiber input caused by noxious mechanical stimulation of the skin of one hindpaw did not induce expression of c-Fos, FosB, Krox-20 or Krox-24; but it did reduce the basal expressions of c-Jun and JunD in both the medial and lateral areas. An intense input produced by electrical stimulation of all the C-fibers in one sciatic nerve also failed to induce expression of c-Fos, FosB, Krox-20 or Krox-24 in the medial or lateral areas. However, in the medial thalamus it increased c-Jun and reduced the basal expression of JunD, whereas in the lateral thalamus it had no effect on c-Jun but again reduced the basal expression of JunD. With repeated stimulation, i.e. when the noxious stimulus was applied to the contralateral hindpaw 6 h after the sciatic stimulation, there was again no induction of c-Fos, FosB or Krox-20 in the medial thalamus; but there was an increase in c-Jun and Krox-24, and a decrease in JunD levels. In the lateral thalamus the repeated stimulation again failed to induce c-Fos, but the expressions of FosB, c-Jun and Krox-24 were increased, and that of JunD was again reduced. With coincident stimulation, i.e. when a stimulus was applied to each hindpaw simultaneously, c-Fos and Krox-24 remained absent; but there was a marked induction of FosB and Krox-20, a strong repression of c-Jun, and no effect or a reduction of the basal levels of JunD. This coincident stimulation also caused FosB to appear in the nucleolus of many thalamic neurons. MK-801, but not L-NAME, blocked all these changes. In summary, noxious stimulation affects the expression of all transcription factors in the medial, lateral and reticular thalamus in a complex manner depending upon the inducible transcription factor considered, the thalamic nucleus, and the stimulation paradigm. The expression of some transcription factors uniquely after simultaneous inputs suggests they act as coincidence detectors at the gene level.

NK cell activity and subsets in women with a history of spontaneous abortion. Cause, number of abortions, and subsequent pregnancy outcome

OBJECTIVE

The aim of this study was to assess the role of NK cells in nonpregnant women with a history of spontaneous abortion.

STUDY DESIGN

113 nonpregnant women with a history of spontaneous abortion were assessed for peripheral NK cell activity and percentage of NK cell subsets, in relation to the cause of abortions, the number of spontaneous abortions, and subsequent pregnancy outcome (n = 56).

RESULTS

Neither NK cell activity nor subsets showed a significant difference in relation to the cause or number of spontaneous abortions. NK cell activity in nonpregnant women who later experienced subsequent abortion with normal chromosomes (n = 10) (mean +/- SD: 42.8 +/- 15.8%) was relatively higher than that in women with subsequent live birth (control, n = 39) (32.1 +/- 13.7%) (p = 0.099). NK cell activity in women who later experienced subsequent abortion with abnormal chromosomes (n = 7) (28.7 +/- 21.4%) was the same as the level in the control.

CONCLUSION

Peripheral NK cell activity or subsets during nonpregnant status were not related to the cause or number of previous spontaneous abortions. A relation between preconceptional NK cell activity and later experiencing abortion with normal chromosomes should be further studied.

The T. cruzi trans-sialidase induces PC12 cell differentiation via MAPK/ERK pathway

The trans-sialidase (TS) of Trypanosoma cruzi induces survival and differentiation of neuronal and glial cells. This mechanism underlying survival is via phosphatidylinositol 3-kinase (PI3K) but how TS promotes neuronal differentiation remained to be determined. Here we show that TS-induced neurite outgrowth in PC12 cells is through sustained activation of the mitogen-activated protein kinase or ERK cascade and, therefore, by a signaling mechanism distinct from the one it uses to induce cell survival. Such differential activation of signal pathways in neuronal cells to effectuate diverse biological activities is analogous to the action of authentic neurotrophins and other growth factors, thereby reinforcing the novel concept of T. cruzi mimicry of host neurotrophic factor(s).

A novel protein interacts with a clock-related protein, rPer1

Mammalian Per proteins are thought to be important in the mechanism of circadian rhythm. We identified a novel protein PIPS (Per1 interacting protein of the suprachiasmatic nucleus) with the yeast two-hybrid system using PAS domain of rat Per1 (rPer1) as a bait. PIPS is about a 180-kDa protein and expressed mainly in the brain, especially in the hypothalamus including the suprachiasmatic nuclei (SCN). PIPS interacts with mouse Per1 (mPer1) in vitro and in cultured cells transfected with both molecules. Furthermore, it was found that mPer1 translocated PIPS into the nuclei in the cultured cells. Thus, these findings suggest a possibility that PIPS is involved in the feedback loop or output mechanism of circadian rhythm through interacting with Per1 in the SCN.

Increased association of brain protein kinase C with the receptor for activated C kinase-1 (RACK1) in bipolar affective disorder

BACKGROUND

Membrane protein kinase C (PKC) activity is increased in frontal cortex of subjects with bipolar affective disorder, and lithium was demonstrated to inhibit PKC translocation to membranes. Protein kinase C is anchored to the membrane via the receptor for activated C kinase-1 (RACK1), suggesting that interactions between these proteins may be altered in bipolar disease.

METHODS

The levels of RACK1 coimmunoprecipitating with PKC isozymes were compared in homogenates of frontal cortex slices from postmortem bipolar subjects and matched control subjects.

RESULTS

Receptor for activated C kinase-1 was located exclusively in membranes and, in control brains, the levels of RACK1 that coimmunoprecipitated with most PKC isozymes were increased by stimulation with the PKC activator, phorbol 12-myristate, 13-acetate (PMA). The association of RACK1 with membrane gammaPKC and zetaPKC was increased under basal conditions in bipolar relative to control brains. Stimulation with PMA increased the amount of RACK1 that coimmunoprecipitated with the alpha, beta, gamma, delta, and varepsilonPKC isozymes, but not zetaPKC, in bipolar tissues over that elicited in control tissues.

CONCLUSIONS

These data suggest that the increased association of RACK1 with PKC isozymes may be responsible for the increases in membrane PKC and in its activation that were previously observed in frontal cortex of bipolar affective disorder brains.

RNA delivery into mitochondria

Mitochondria, though containing their own genome, import the vast majority of their macromolecular components from the cytoplasm. If the mechanisms of pre-protein import are well understood, the import of nuclear-coded RNAs into mitochondria was investigated to a much lesser extent. This targeting, if not universal, is widely spread among species. The origin and the mechanisms of RNA import seem to differ from one system to another and striking differences are observed even in closely related species. We describe data concerning the various experimental systems of studying RNA import with emphasis on the model of the yeast Saccharomyces cerevisiae, which was studied in our laboratory. We compare various requirements of RNA import into mitochondria in different species and demonstrate that this pathway can be transferred from yeast to human cells, in which tRNAs normally are not imported. We speculate on the possibility to use RNA import for biomedical purposes.

Fish cytogenetics and the future of radiation biodosimetry

Fluorescence in situ hybridisation (FISH) with whole chromosome paints has greatly facilitated the analysis of structural chromosome aberrations and has led to translocations replacing dicentrics as the aberration of choice for many applications. Major challenges remain if we are to go from translocations to an understanding of the health consequences of radiation exposure. Yet to be surmounted are the roles of individual susceptibility, time since exposure, and the effects of subjects age. Accomplishing these objectives will require automation, reduced costs, improved calibration, and extensive use of baseline samples.

Interaction of expanded polyglutamine stretches with nuclear transcription factors leads to aberrant transcriptional regulation in polyglutamine diseases

At least eight inherited neurodegenerative diseases are known to be caused by expanded CAG repeats encoding polyglutamine (polyQ) stretches. Although cytotoxicities of expanded polyQ stretches have been suggested, the molecular mechanisms of neurodegeneration remain unclear. The nuclear translocation of mutant proteins containing expanded polyQ stretches has been demonstrated as a prerequisite for the expression of their cytotoxicity. Hypothesizing that nuclear proteins that interact with mutant proteins, particularly, those that bind to the expanded polyQ stretches, are involved in the pathogenetic mechanisms underlying neurodegeneration, nuclear proteins were screened for their capability of binding to expanded polyQ stretches. It was found that expanded polyQ stretches preferentially bind to TAF(II)130, a coactivator involved in cAMP-responsive element-binding protein (CREB)-dependent transcriptional activation. The binding of TAF(II)130 with expanded polyQ stretches strongly suppresses CREB-dependent transcriptional activation, suggesting that interference with transcription due to the binding of expanded polyQ stretches with TAF(II)130 and redistribution of TAF(II)130 are involved in the pathogenetic mechanisms underlying neurodegeneration.