Increased cyclic AMP response to forskolin in Epstein-Barr virus-transformed human B-lymphocytes derived from schizophrenics

Phorbol 12-myristate-13-acetate (PMA), a protein kinase C (PKC) activator, elevated basal cyclic AMP levels and enhanced isoproterenol-, prostaglandin E1- (PGE1), forskolin- and cholera toxin-stimulated cyclic AMP accumulation in Epstein-Barr virus (EBV)-transformed human B-lymphocytes. Staurosporine, a PKC inhibitor, significantly antagonized the increase in cyclic AMP accumulation produced by PMA, whereas the inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD), had no effect. Basal levels of cyclic AMP and the accumulation of cyclic AMP produced by PMA, isoproterenol, PGE1, cholera toxin and the combination of these compounds with PMA were not significantly different between schizophrenics and controls. The cyclic AMP response to forskolin in the presence and absence of PMA was significantly greater in EBV-transformed human B-lymphocytes from schizophrenics. These results suggest that activation of adenylyl cyclase by forskolin is elevated in EBV-transformed B-lymphocytes derived from schizophrenics and that this elevation is further enhanced through a PKC-dependent phosphorylation mechanism.

Chronic cocaine administration increases tyrosine hydroxylase activity in the ventral tegmental area through glutaminergic- and dopaminergic D2-receptor mechanisms

Tyrosine hydroxylase activity was measured in the brain of rats treated chronically with saline or cocaine (10 mg/kg, 2 x day, for 7 days). Tyrosine hydroxylase activity was significantly increased in the ventral tegmental area 1, 6 and 12 weeks after the last treatment with cocaine. The increase in tyrosine hydroxylase activity at 6 weeks after the last cocaine injection was prevented by the prior administration of MK-801, haloperidol or clozapine but not by the D1 receptor antagonist, SCH-23390. SCH-23390 produced a significant increase in tyrosine hydroxylase activity when administered with saline. These data indicate that glutaminergic and dopaminergic D2-receptor mediated mechanisms are important in regulating the effect of cocaine on the ventral tegmental area.

Evaluation of cyclic AMP accumulation in EBV-transformed human B-lymphocytes: effects of dopamine agonists, isoproterenol, prostaglandin E1, cholera toxin, forskolin, and phorbol 12-myristate-13 acetate

1. Phorbol 12-myristate-13-acetate (PMA), a protein kinase C activator, elevated cyclic AMP accumulation in EBV-transformed human B-lymphocytes, and potentiated isoproterenol-, prostaglandin- (PGE1), cholera toxin-, and forskolin-stimulated cyclic AMP accumulation. 2. The dopamine D1 receptor agonist, SKF38393 (10(-7) to 10(-5) MH, had no effect on cyclic AMP accumulation in transformed human B-lymphocytes. 3. The dopamine D2 receptor agonist, quinpirole (10(-7) to 10(-5) MH did not inhibit cyclic AMP accumulation even when cyclic AMP accumulation was maximized by the addition of PMA and forskolin. 4. These data suggest that dopamine D1- and D2-receptor coupling to a cyclic AMP generating system is not present at detectable levels in transformed human B-lymphocytes.

Immunocytochemical localization of calmodulin in PC12 cells and its possible interaction with histones

The subcellular localization of calmodulin, a multi-functional calcium-binding regulatory protein, was examined immunocytochemically in undifferentiated PC12 rat pheochromocytoma cells and cells differentiated with nerve growth factor (NGF) and dibutyryl cyclic AMP. In undifferentiated PC12 cells, diffuse immunostaining for calmodulin was observed in the cytoplasm, and weak, patch-like staining was found in the nucleus. In differentiated cells, intense immunostaining for calmodulin was observed in the cytoplasm, while nuclear immunostaining was still evident. Immunoreactivity for calmodulin was also observed along newly-formed neuritic processes, with strong staining in varicosity-like structures and growth cones. Using double-label immunochemistry, the relative intensity of immunostaining for calmodulin among the nuclei was found to correlate with the relative intensity of immunostaining for histones in the same nuclei. A comparison of a profile of 125I-calmodulin binding in the nuclear fraction from PC12 cells to that of immunoblotting for histones in the same fraction indicated that some of the histones are calmodulin-binding proteins in PC12 cells. These results show that the level and subcellular distribution of calmodulin are altered during the course of nerve cell differentiation and suggest the possibility that histones may function as major nuclear binding proteins for calmodulin.

Phenotypic heterogeneity of an adult form of adrenoleukodystrophy in monozygotic twins

We describe genetically proven monozygotic twins with the adult form of adrenoleukodystrophy with significant phenotypic heterogeneity. Myeloneuropathy was common to both patients, but cognitive impairment and affective symptoms with extensive demyelination in the brain were prominent in the older twin, while adrenal insufficiency was predominant in the younger twin. The younger twin, however, exhibited affective symptoms similar to those displayed by his elder twin 10 years later. These findings suggest that nongenetic factors are important in determining the phenotypic variation of adrenoleukodystrophy gene.

Continuously infusing quinpirole decreases Ca2+/calmodulin-dependent phosphorylation in mouse striatum

Continuously administering the D2 dopamine agonist quinpirole to mice for 6 days produces an initial stereotypy that is reduced by 2 h and is absent from 3 h to the 6 day duration of the infusion. In an attempt to determine the biochemical correlates for this down-regulation of stereotypic behavior, the effects of continuously administering quinpirole on a number of biochemical parameters were measured in mouse corpus striatum. After 6 days of infusion with quinpirole, the striata were analyzed for D1 and D2 dopamine receptors, for the activities of several protein phosphorylation reactions which are thought to be involved in receptor activity and for the levels of calmodulin-binding proteins. Quinpirole decreased the D2 receptors in striatum and produced a small but statistically non-significant increase in D1 receptors, resulting in a significant increase in the ratio of D1 to D2 dopamine receptors. An examination of the effects of quinpirole on protein phosphorylation systems showed that the agonist failed to alter the activity of cyclic AMP-dependent protein kinase or protein kinase C but significantly decreased the Ca2+/calmodulin-dependent phosphorylation of striatal membranes. However, this decrease in Ca2+/calmodulin-dependent phosphorylation was not associated with changes in the levels of calmodulin-binding proteins. The results suggest that behavioral down-regulation following the continuous administration of a D2 dopamine agonist is associated with at least two biochemical events: a down-regulation of D2 dopamine receptors and a decrease of Ca2+/calmodulin-dependent phosphorylation of striatal membranes.

Localization of the multiple calmodulin messenger RNAs in differentiated PC12 cells

Calmodulin, a ubiquitous calcium-binding protein which is involved in many biological processes, including cell proliferation and differentiation, has been shown to be encoded by three genes from which five calmodulin messenger RNAs are transcribed. In our previous studies, using the PC12 pheochromocytoma cell line as a model system for neuronal differentiation, all five calmodulin messenger RNAs were found to be present, and treatment with both nerve growth factor and dibutyryl cyclic AMP, which induce neurite outgrowth in these cells, increased the level of calmodulin and differentially increased the levels of the various calmodulin messenger RNAs. In an attempt to uncover the nature of the differential increase in the calmodulin messenger RNAs during neuronal differentiation, we examined here the subcellular distribution of the individual calmodulin messenger RNAs in PC12 cells treated with nerve growth factor and dibutyryl cyclic AMP by in situ hybridization cytochemistry, using radiolabeled oligodeoxynucleotide probes. Using an oligodeoxynucleotide probe which detects all of the calmodulin transcripts, the calmodulin messenger RNAs were found to be distributed throughout the cell bodies of differentiated PC12 cells; significant amounts of calmodulin messenger RNAs were also found in most neurites (approximately 70% of the total number). Using specific probes for the calmodulin messenger RNAs derived from each calmodulin gene, distinct patterns of localization of the different calmodulin messenger RNAs were revealed. The messenger RNAs from calmodulin genes I and II were readily detected in all cell bodies and in about one-half of the neurites. In contrast, a weak signal for the messenger RNAs from calmodulin gene III was associated with cell bodies, while no significant signal was found in neurites. A population distribution analysis of the labeling of individual PC12 cell bodies, as determined by counting autoradiographic grains, revealed differences in the relative abundance of each group of messenger RNAs derived from each of the three calmodulin genes. The order of relative abundance of the messenger RNAs in cell bodies was found to be: calmodulin gene II messenger RNA > calmodulin gene I messenger RNAs >> calmodulin gene III messenger RNAs. An analysis of the labeling density along neurites indicated a similar density of neuritic messenger RNAs from calmodulin gene I and calmodulin gene II, whereas there was no significant signal for the messenger RNAs from calmodulin gene III.(ABSTRACT TRUNCATED AT 400 WORDS)

Calmodulin-binding proteins of calcium-independent type in rat brain synaptosomal membranes: their localization and properties

Some properties of calmodulin(CaM)-binding proteins (CaMBPs) of the Ca(2+)-independent type were investigated in the synaptosomal membrane (SM) from rat brain using the [125I]CaM gel overlay method. When SM was prepared in the presence of Ca2+, Ca(2+)-independent CaM binding was decreased, whereas the Ca(2+)-dependent type was not altered. All Ca(2+)-independent-type CaMBPs were membrane-bound and scarcely present in the soluble fractions. When SM was heat-denatured, the 24/22.5-kDa CaMBPs could no longer be detected by [125]CaM binding and a new component with higher molecular mass (greater than 200 kDa) was shown to bind CaM in a Ca(2+)-independent manner. A possible effect of cAMP- and Ca2+/CaM-dependent phosphorylation on CaM binding was also examined.

Characterization of EGTA-washed synaptosomal membrane with emphasis on its calmodulin-binding proteins. Demonstration of possible reconstitution with added calcium/calmodulin

Endogenous calmodulin (CaM) in the EGTA-washed cerebral-cortical synaptosomal membrane (SM) preparation was estimated below 3 micrograms/ml protein by the semiquantitative immunoblot analysis (Natsukari, N., Ohta, H. and Fujita, M. (1989) J. Immunol. Methods 125, 159-166). Membrane-bound CaM was immunoelectron-microscopically demonstrated in EGTA-washed, non-treated (control), and Ca(2+)-treated cerebral-cortical synaptosomal membranes (SM) as well as for the SM enriched with added CaM. The density of CaM increased in the above order. CaM-dependent adenylate cyclase and CaM-dependent protein kinase II (CaM-kinase II) activities were restored, whereas the phosphodiesterase (PDE) activity was not affected by exogenous CaM over all the Ca2+ concentrations tested. Adenylate cyclase at pCa 6.2 was synergistically activated either by GTP and CaM or by CaM and beta-adrenergic agonist, (+/-)-isoproterenol, reflecting the intactness of signal transduction pathway in the SM. Also demonstrated were the presence of protein kinase A, CaM-kinase II, and their endogenous substrates in the SM. Based on 32P-autoradiography and 125I-CaM overlay data certain CaM-binding proteins such as CaM-kinase II and synapsin I were identified on SDS-PAGE. Ca(2+)-dependent and -independent CaMBPs were distinguished by 125I-CaM gel overlay with and without Ca2+. The former had bigger molecular size (greater than or equal to 49 kDa) than the latter (less than or equal to 34 kDa). Yield of Ca(2+)-dependent CaMBPs was not affected by Ca2+ concentration during preparation of the SM while that of Ca(2+)-independent CaMBPs was reduced by exposure to 100 microM Ca2+. In contrast with the CaMBPs of brain SM, those of enterocyte and eyrthrocyte plasma membranes especially, microvillous membrane of the enterocyte, showed quite distinct CaMBP profiles. The present findings suggested that the EGTA-washed SM preparation made a useful system for studying the role of CaM in the brain SM.

Dopamine D2-receptor mRNA level in rat striatum after chronic haloperidol treatment

Chronic treatment with haloperidol, a D2-receptor antagonist and a neuroleptic, increases the number of D2-receptors in rat striatum. However, there have been inconsistent reports on the D2-receptor mRNA level, one showing the increase in the mRNA level and another detecting no changes. Furthermore, they did not distinguish the two isoforms of D2-receptor, D2A and D2B. In the present work, both D2- and DeA-receptor mRNA levels in rat striatum were estimated after chronic administration of haloperidol. There was, within the sensitivity of the assay, no significant increase in either of them between 3 and 24 h after the last administration. This suggests that chronic haloperidol treatment does not affect the transcriptional regulation of the D2-receptor gene or the alternative splicing process of its transcripts.

Synergistic activation of brain adenylate cyclase by calmodulin, and either GTP or catecholamines including dopamine

The effects of calmodulin (CaM), guanosine triphosphate (GTP) and dopaminergic or beta-adrenergic agonists on the activities of adenylate cyclase were studied in EGTA-washed lysed synaptosomal membranes from rat striatum and cerebral cortex. Based on the free calcium ion concentration-dependence of the enzymic activity, it was found that the stimulatory effect of CaM and GTP on adenylate cyclase was synergistic with maximum activation at pCa 6.2 for both striatal and cortical membranes. This was not due to the effect of CaM-dependent phosphodiesterase because exogenous CaM did not affect particulate phosphodiesterase activity. Added CaM not only enhanced the adenylate cyclase activity but acted cooperatively with dopaminergic or beta-adrenergic agonists in the presence of GTP. Most marked was enhancement found for the striatal SKF 38393- (a specific D1 agonist) and the cortical isoproterenol-dependent activities. A synergism was also found for CaM and forskolin. These findings strongly suggest that CaM is involved in the striatal dopaminergic as well as in the cortical beta-adrenergic systems.

Simple immunoassays for semiquantitative determination of calmodulin (CaM) and anti-CaM. Applications to affinity column chromatography of anti-CaM antibodies and estimation of CaM in synaptosomal membranes from rat cerebral cortex

Dot-immunobinding assay for anti-calmodulin (CaM), and immunoblot assay for CaM have become feasible by proper choice of a fixative, i.e., formaldehyde vapor. The protocol for these simple and convenient immunological procedures is presented. Dot-immunobinding assay could be accomplished in 3 h, and immunoblot assay in 8 h. Activities of anti-CaM antibodies in fractions eluted from CaM affinity column were monitored by immunobinding assay. Semiquantitative immunoblot analysis was used to estimate CaM present in various fractions during preparation of EGTA-washed lysed synaptosomal membranes from rat cerebral cortex. CaM content in the final preparation was estimated at lower than 3 micrograms/mg of membrane protein.