cAMP-dependent protein kinase phosphorylates and activates nuclear Ca2+-ATPase.

A Ca2+-pump ATPase, similar to that in the endoplasmic reticulum, has been located on the outer membrane of rat liver nuclei. The effect of cAMP-dependent protein kinase (PKA) on nuclear Ca2+-ATPase (NCA) was studied by using purified rat liver nuclei. Treatment of isolated nuclei with the catalytic unit of PKA resulted in the phosphorylation of a 105-kDa band that was recognized by antibodies specific for sarcoplasmic reticulum Ca2+-ATPase type 2b. Partial purification and immunoblotting confirmed that the 105-kDa protein band phosphorylated by PKA is NCA. The stoichiometry of phosphorylation was 0.76 mol of phosphate incorporated/mol of partially purified enzyme. Measurement of ATP-dependent 45Ca2+ uptake into purified nuclei showed that PKA phosphorylation enhanced the Ca2+-pumping activity of NCA. We show that PKA phosphorylation of Ca2+-ATPase enhances the transport of 10-kDa fluorescent-labeled dextrans across the nuclear envelope. The findings reported in this paper are consistent with the notion that the crosstalk between the cAMP/PKA- and Ca2+-dependent signaling pathways identified at the cytoplasmic level extends to the nucleus. Furthermore, these data support a function for crosstalk in the regulation of calcium-dependent transport across the nuclear envelope.

[Pharmacological management of failure of treatment with antidepressants]. / Approche pharmacologique des échecs aux traitements antidépresseurs.

Depression, a chronic disease and a leading cause of disability worldwide, will generate increasing needs in terms of public health in the coming years. Many antidepressants are now available. However, these molecules present real limitations and disadvantages. Thus there are great expectations on the part of the clinicians for more efficient drugs that are better tolerated. How can we satisfy such hopes and innovate in this domain today? One original and most promising strategy for developing new antidepressants that are more efficient and better tolerated involves antagonizing both alpha 2-noradrenergic and 5HT2 and 5HT3 serotonergic receptors, without blocking 5HT1A serotonergic receptors. The technology now available in pharmacological research allows the development of such molecules.

[Pharmacological approach to failures of antidepressant treatment]. / Approche pharmacologique des échecs aux traitements antidépresseurs.

Depression, a chronic disease and a leading cause of disability worldwide, will generate increasing needs in terms of public health in the coming years. Many antidepressants are now available. However, these molecules present real limitations and disadvantages. Thus there are great expectations on the part of the clinicians for more efficient drugs that are better tolerated. How can we satisfy such hopes and innovate in this domain today? One original and most promising strategy for developing new antidepressants that are more efficient and better tolerated involves antagonizing both alpha 2-noradrenergic and 5HT2 and 5HT3 serotonergic receptors, without blocking 5HT1A serotonergic receptors. The technology now available in pharmacological research allows the development of such molecules.

Pervanadate elicits proliferation and mediates activation of mitogen-activated protein (MAP) kinase in the nucleus.

There is growing evidence for the role of protein tyrosine phosphatases in controlling such fundamental cellular processes as growth and differentiation. Pervanadate is a potent inhibitor of protein tyrosine phosphatase which has been observed here to induce proliferation in C3H10T1/2 mouse fibroblasts. Pervanadate also translocated/activated p42/44 mitogen-activated protein (MAP) kinase to the cell nucleus. An almost similar pattern of nuclear p42/44 MAP kinase stimulation is seen with TPA. On the other hand, TPA treatment results in a rapid activation of cytosolic MAP kinase which declines with time. Thus pervanadate appears as a very useful tool for studying tyrosine phosphorylation.

Regulation of signalling pathways to the nucleus by dopaminergic receptors.

Dopamine regulates postsynaptic gene expression in the central nervous system. The pattern of gene expression is different from chronic vs acute stimulation of dopaminergic receptors. Signalling to the nucleus through dopamine receptors involves different second messenger systems, and each receptor subtype regulates multiple effectors. Long term adaptive changes in neuronal function following administration of dopaminergic drugs such as antipsychotic agent or drugs of abuse is one such example of molecular plasticity triggered by dopaminergic receptors. Role of dopaminergic receptors in the control of transcriptional events and immediate early gene regulation are reviewed.

Neuroleptics differentially induce jun family genes in the rat striatum.

The effect of neuroleptics in single administration on the expression of genes of the jun family was studied in the rat striatum. jun B, but not jun D was dose-dependently and transiently induced. This effect was blocked by pretreatment with a specific dopamine D2 agonist. The expression of c-jun was also stimulated, although this did not reach statistical significance. Thus dopamine D2 receptors differentially regulate the expression of jun family members in the striatum.

Impaired gene transcription and nuclear protein kinase C activation in the brain and liver of aged rats.

The expression of the hsp70 and c-fos genes and the activation of nuclear protein kinase C (PKC) were studied in young and aged whole rats under heat-shock conditions. The induction of hsp70 and c-fos genes by heat shock were decreased several fold in the brain as well as in the liver of senescent animals. Nuclear run-off transcription assay indicated that this age-related impairment could be attributed to a block at the level of transcription. Nuclear PKC activation by heat shock was not apparent in old animals. Nuclear PKC involvement in the repression of transcription during senescence is postulated.

[Regulation of the dopamine D2 receptor gene and the early genes in the CNS by neuroleptics]. / Régulation du gène du récepteur dopaminergique D2 et des gènes précoces dans le SNC par les neuroleptiques.

The interaction of a ligand with its cognate receptor not only activates signal transduction pathways but also determines adaptive responses affecting key elements in these pathways, in particular the cell surface receptor. Such is the case for G protein-linked receptors, the expression and functional status of which are highly regulated. The regulatory mechanisms involved can be divided according to two distinct time frames, acute and chronic. In the short-term, posttranslational mechanisms alter the functional status of the elements without changing steady-state levels or gene expression. Protein phosphorylation plays a prominent role in these acute adaptive responses. Thus agonists promote phosphorylation and the desensitization of several G protein-linked receptors. And we have shown in the case of the dopamine D2 receptor that protein kinase C modulates receptor coupling to its G-protein. Longer-term regulation involves transcriptional (gene expression), posttranslational (mRNA stability), and posttranslational (protein phosphorylation) regulation of the turnover of the elements in the information transduction pathway. In the case of G protein-linked receptors, long-term regulation is often reflected in changes in steady-state levels of mRNA (which can be quantified by techniques such as northern blot analysis, solution hybridization or in-situ hybridization). For dopamine D2 receptors, prolonged administration of neuroleptic drugs induces an up-regulation of receptor mRNA in various brain regions, probably through an increase in gene transcription. Receptor-transduced extracellular stimuli are converted into long-term changes in gene expression through specific nuclear transcription factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Heat stressing stimulates nuclear protein kinase C raising diacylglycerol levels. Nuclear protein kinase C activation precedes Hsp70 mRNA expression.

Protein kinase C (pKC) activity has been studied in rat liver after subjecting animals to heat shocking. Nuclear pKC activity was stimulated owing to heat shocking without any change in the cytosolic enzyme activity. The nuclear diacylglycerol levels were raised owing to heat stress along with the stimulation of polarhead phospholipid hydrolysis. Kinetically, the Vmax of nuclear pKC was enhanced as a result of heat shocking, with no change in apparent Km and with concomitant phosphorylation of nuclear lamin B2. Western blot analysis as well as phorbol dibutyrate binding indicate that pKC protein levels did not change because of heat shocking. The stimulation of nuclear pKC under heat stress conditions represents an in vivo phenomenon and the enzymes stimulation precedes Hsp70 mRNA expression.

Stimulation of nuclear protein kinase C leads to phosphorylation of nuclear inositol 1,4,5-trisphosphate receptor and accelerated calcium release by inositol 1,4,5-trisphosphate from isolated rat liver nuclei.

Rat liver nuclei inositol 1,4,5-trisphosphate receptor (Malviya, A.N., Rogue, P., and Vincendon, G. (1990) Proc. Natl. Acad. Sci U.S.A. 87, 9270-9274) is identified as a 220-kDa protein on Western blotting employing two types of antibodies (anti-goat and anti-rabbit) raised against purified rat brain inositol 1,4,5-trisphosphate receptor (IP3R). Nuclear IP3R does not seem identical with microsomal IP3R in rat liver. Treatment of isolated rat liver nuclei with 12-O-tetradecanoylphorbol-13-acetate stimulates native protein kinase C activity severalfold. Nuclear IP3R is phosphorylated by stimulated protein kinase C, with accelerated as well as enhanced maximum 45Ca2+ release by inositol 1,4,5-trisphosphate from isolated nuclei, without altering 1,4,5-trisphosphate binding characteristics (KD and Bmax). Stimulation of nuclear protein kinase C is found physiologically relevant since lamin B2, a nuclear protein, is concomitantly phosphorylated. These data deal with functional consequences of nuclear IP3R phosphorylation by native protein kinase C in isolated rat liver nuclei. It is postulated that phosphorylation of nuclear IP3R, probably dephosphorylation also, subserves a key mechanism in nuclear calcium homeostasis.

Dopamine D2 receptor antagonists induce immediate early genes in the rat striatum.

The acute effects of dopamine D2 antagonists and agonists on the expression of c-jun, zif-268, ETR101 and c-fos in the rat striatum were studied. A single injection IP of haloperidol (2 mg/kg) or sulpiride (100 mg/kg) produced a rapid and transient increase in c-jun, zif-268 and c-fos mRNA. ETR101 was not activated. These inductions were dose dependent and were specifically blocked by pretreatment with a D2 agonist (1 mg/kg quinelorane). Quinelorane alone had no effect. Thus, dopamine D2 receptors inhibit the expression of a particular set of immediate early genes in the striatum.

[Induction by neuroleptics of certain genes in the central nervous system]. / Induction par les neuroleptiques de certains gènes dans le système nerveux central.

Prolonged administration of neuroleptic drugs increases the density of dopamine D2 receptors in several brain regions. We have recently shown that such treatment also raises dopamine D2 receptor mRNA levels in the striatum. To elucidate some of the initial events which lead to this upregulation, we studied the acute effects of dopamine D2 agonists and antagonists on the expression of c-jun and c-fos. A single injection I.P. of haloperidol (2 mg/kg) produced a rapid and transient increase in c-jun and c-fos mRNA in the rat striatum. This induction was specifically blocked by a D2 agonist (1 mg/kg quinelorane). In contrast, by itself quinelorane was without effect. These results show that dopamine D2 receptors inhibit the expression of a set of immediate early genes in the striatum, and these may be involved in the up-regulation of D2 mRNA upon prolonged neuroleptic treatment.

Bio-clinical prevalence or non-prevalence of drug addiction over psychiatric symptomatology.

It has been found that opiate abusers once detoxified are afflicted with personality disorders. An attempt was made to test the origin of drug abuse by comparing a group of drug abusers with personality disorders diagnosed as borderline or schizotypal with a group of people suffering from similar personality disorders but who did not use drugs. The results of the test are discussed.

[Results of an epidemiological survey conducted with psychiatrists, general practitioners, liberal nurses and social workers in a mental health sector]. / Résultat d'une enquête épidémiologique effectuée auprès de psychiatres, d'omnipraticiens, d'infirmiers libéraux et de travailleurs sociaux exerçant au sein du secteur A4.

An epidemiological survey was carried out, amongst psychiatrists, general practitioners, social workers and liberal nurses, with a double aim. To determine the number of psychiatric cases followed or identified; these were classified according to DSMIII criteria (simplified for use by those interviewers little used to psychiatric jargon), essentially: dementia, depression, schizophrenia, other psychosis, other cases (neurosis, substance abuse, alcoholism). Another aim was to determine how the psychiatric care facilities were perceived and used by the person's interviewed. The results reveal a lack of information on their part, despite pst information given by us (systematic misappreciation?); as well as the lack of a desire to collaborate: the practitioners address their patients to the public health service (and preferentially for full-time hospitalisation) when they feel the case is beyond them.

Up-regulation of dopamine D2 receptor mRNA in rat striatum by chronic neuroleptic treatment.

The effect of prolonged administration of antagonists on rat striatal dopamine D2 receptor binding and mRNA content was examined. Both haloperidol (2 and 4 mg/kg) and sulpiride (10 mg/kg) induced a significant rise in total D2 and D2(444) mRNA level and in Bmax. Regulation of messenger RNA accumulation is thus an important determinant of dopamine D2 receptor density.

Stereospecific inositol 1,4,5-[32P]trisphosphate binding to isolated rat liver nuclei: evidence for inositol trisphosphate receptor-mediated calcium release from the nucleus.

It is well known that inositol 1,4,5-trisphosphate binding and release of calcium are mediated by the same protein. Several reports have indicated the location of the inositol 1,4,5-trisphosphate receptor in organelles other than endoplasmic reticulum. Immunocytochemical studies on the subcellular localization of 1,4,5-trisphosphate receptor in the Purkinje cells from two laboratories have given contradictory results regarding the nuclear location of this receptor. In this paper, a high-affinity inositol 1,4,5-[32P]trisphosphate binding site (Kd = 0.11 nM) on nuclei isolated from rat liver and devoid of any microsomal, mitochondrial, or plasma membrane constituents is documented. Furthermore, we present data demonstrating that inositol 1,4,5-trisphosphate is capable of releasing 45Ca2+ from the intact isolated liver nuclei. A rapid and transient release of calcium that was taken up by nuclei in the presence of ATP is observed. The role of inositol 1,4,5-trisphosphate in the coupling between cytoplasmic second messengers and nuclear events activated during signal transduction is postulated.

Phosphorylation by protein kinase C modulates agonist binding to striatal dopamine D2 receptors.

The effect of purified protein kinase C (PKC) on dopamine D2 receptor binding was studied. Saturation binding with [3H]spiperone was not affected. In competition experiments using agonists PKC-treated membranes showed a significant reduction in the proportion of high affinity sites, and the influence of GTP gamma S was abolished. These results suggest that PKC-dependent mechanisms can regulate the coupling between the dopamine D2 receptor and its G-protein.