The Ca2+/calmodulin signaling system in the neural response to excitability. Involvement of neuronal and glial cells

Magnetic Stimulation as a Therapeutic Approach for Brain Modulation and Repair: Underlying Molecular and Cellular Mechanisms

Neurological and psychiatric diseases generally have no cure, so innovative non-pharmacological treatments, including non-invasive brain stimulation, are interesting therapeutic tools as they aim to trigger intrinsic neural repair mechanisms. A common brain stimulation technique involves the application of pulsed magnetic fields to affected brain regions. However, investigations of magnetic brain stimulation are complicated by the use of many different stimulation parameters. Magnetic brain stimulation is usually divided into two poorly connected approaches: (1) clinically used high-intensity stimulation (0.5-2 Tesla, T) and (2) experimental or epidemiologically studied low-intensity stimulation (μT-mT). Human tests of both approaches are reported to have beneficial outcomes, but the underlying biology is unclear, and thus optimal stimulation parameters remain ill defined. Here, we aim to bring together what is known about the biology of magnetic brain stimulation from human, animal, and in vitro studies. We identify the common effects of different stimulation protocols; show how different types of pulsed magnetic fields interact with nervous tissue; and describe cellular mechanisms underlying their effects-from intracellular signalling cascades, through synaptic plasticity and the modulation of network activity, to long-term structural changes in neural circuits. Recent advances in magneto-biology show clear mechanisms that may explain low-intensity stimulation effects in the brain. With its large breadth of stimulation parameters, not available to high-intensity stimulation, low-intensity focal magnetic stimulation becomes a potentially powerful treatment tool for human application.

Interdomain Dynamics via Paramagnetic NMR on the Highly Flexible Complex Calmodulin/Munc13-1

Paramagnetic NMR constraints are very useful to study protein interdomain motion, but their interpretation is not always straightforward. On the example of the particularly flexible complex Calmodulin/Munc13-1, we present a new approach to characterize this motion with pseudocontact shifts and residual dipolar couplings. Using molecular mechanics, we sampled the conformational space of the complex and used a genetic algorithm to find ensembles that are in agreement with the data. We used the Bayesian information criterion to determine the ideal ensemble size. This way, we were able to make an accurate, unambiguous, reproducible model of the interdomain motion of Calmodulin/Munc13-1 without prior knowledge about the domain orientation from crystallography.

Axotomy-Induced Changes of the Protein Profile in the Crayfish Ventral Cord Ganglia

We suggest novel experimental model of nerve injury-bilaterally axotomized ganglia of the crayfish ventral nerve cord (VNC). Using proteomic antibody microarrays, we showed upregulation of apoptosis execution proteins (Bcl-10, caspases 3, 6, and 7, SMAC/DIABLO, AIF), proapoptotic signaling proteins and transcription factors (c-Myc, p38, E2F1, p53, GADD153), and multifunctional proteins capable of initiating apoptosis in specific situations (p75, NMDAR2a) in the axotomized VNC ganglia. Simultaneously, anti-apoptotic proteins (p21WAF-1, MDM2, Bcl-x, Mcl-1, MKP1, MAKAPK2, ERK5, APP, calmodulin, estrogen receptor) were overexpressed. Some proteins associated with actin cytoskeleton (α-catenin, catenin p120CTN, cofilin, p35, myosin Vα) were upregulated, whereas other actin-associated proteins (ezrin, distrophin, tropomyosin, spectrin (α + β), phosphorylated Pyk2) were downregulated. Various cytokeratins and β_IV-tubulin, components of intermediate filament and microtubule cytoskeletons, were also downregulated that could be the result of tissue destruction. Downregulation of proteins involved in clathrin vesicle formation (AP2α and AP2γ, adaptin (β1 + β2), and syntaxin) indicated impairment of vesicular transport and synaptic processes. The levels of L-DOPA decarboxylase, tyrosine, and tryptophan hydroxylases that mediate synthesis of serotonin, dopamine, norepinephrine, and epinephrine decreased. Overexpression of histone deacetylases HDAC1, HDAC2, and HDAC4 contributed to suppression of transcription and protein synthesis. So, the balance of multidirectional processes aimed either at cell death, or to repair and recovery, determines the cell fate. Present data provide integral, albeit incomplete, view on the nervous tissue response to axotomy. Some of these proteins can be probably potential markers of nerve injury and targets for neuroprotective therapy.

Nicotinic acetylcholine receptors regulate type 1 inositol 1,4,5-trisphosphate receptor expression via calmodulin kinase IV activation

Type 1 inositol 1,4,5-trisphosphate receptors (IP3 R-1) are among the important calcium channels regulating intracellular Ca(2+) concentration in the central nervous system. In a previous study, we showed that drugs of abuse, such as cocaine, methamphetamine, and ethanol, induced IP3 R-1 upregulation via the calcium signal transduction pathway in psychological dependence. Although nicotine, a major component in tobacco smoke, participates in psychological and/or physical dependence, it has not yet been clarified how nicotine alters IP3 R-1 expression. The present study, therefore, seeks to clarify the mechanism bgy which nicotine modifies IP3 R-1 expression by using mouse cerebral cortical neurons in primary culture. Nicotine induced dose- and time-dependent upregulation of IP3 R-1 protein following its mRNA increase, and the latter was significantly suppressed by a nonselective nicotinic acetylcholine receptors (nAChR) antagonist, mecamylamine. Both cFos and phosphorylated-cJun (p-cJun) were immediately increased in the nucleus, together with an increase of calmodulin kinase (CaMK) IV but not CaMKII expression after nicotine exposure. A nonselective inhibitor of CaMKs, KN-93, and a calcium chelating regent, BAPTA-AM, completely suppressed the expression of cFos and p-cJun in the nucleus as well as the nicotine-induced IP3 R-1 upregulation. These results indicate that nAChR activation by nicotine upregulates IP3 R-1 via increase of activator protein-1, which is a cFos and cJun dimmer, in the nucleus, with activation of Ca(2+) signaling transduction processes.

Dopamine D1 receptors regulate type 1 inositol 1,4,5-trisphosphate receptor expression via both AP-1- and NFATc4-mediated transcriptional processes

Although our recent report demonstrates the essential involvement of up-regulation of a regulator of intracellular Ca(2+) concentration, type 1 inositol 1,4,5-trisphosphate receptors (IP(3) Rs-1), mediated via dopamine D1-like receptor (D1DR) stimulation in the cocaine-induced psychological dependence, the exact mechanisms of regulation of IP(3) R-1 expression by D1DRs have not yet been clarified. This study attempted to clarify these mechanisms using mouse cerebral cortical neurons. An agonist for phosphatidylinositide-linked D1DRs, SKF83959, induced dose- and time-dependently IP(3) R-1 protein up-regulation following its mRNA increase without cAMP production. U73122 (a phospholipase C inhibitor), BAPTA-AM (an intracellular calcium chelating reagent), W7 (a calmodulin inhibitor), KN-93 (a calmodulin-dependent protein kinases inhibitor), and FK506 (a calcineurin inhibitor), significantly inhibited the SKF83959-induced IP(3) R-1 up-regulation. Furthermore, immunohistochemical examinations showed that SKF83959 increased expression of both cFos and cJun in nucleus as well as enhanced translocation of both calcineurin and NFATc4 complex to nucleus from cytoplasm. In addition, SKF83959 directly recruited binding of both AP-1 and NFATc4 to IP(3) R-1 promoter region. These results indicate that D1DR activation induces IP(3) R-1 up-regulation via increased translocation of AP-1 as well as NFATc4 in Gαq protein-coupled calcium signaling transduction pathway.

The wheat germ agglutinin-fractionated proteome of subjects with Alzheimer's disease and mild cognitive impairment hippocampus and inferior parietal lobule: Implications for disease pathogenesis and progression

Lectin affinity chromatography is a powerful separation technique that fractionates proteins by selectively binding to specific carbohydrate moieties characteristic of protein glycosylation type. Wheat germ agglutinin (WGA) selectively binds terminal N-acetylglucosamine (O-GlcNAc) and sialic acid moieties characteristic of O-linked glycosylation. The current study utilizes WGA affinity chromatography to fractionate proteins from hippocampus and inferior parietal lobule (IPL) from subjects with Alzheimer's disease (AD) and arguably its earliest form, mild cognitive impairment (MCI). Proteins identified by proteomics that were fractionated from MCI and AD hippocampus by WGA affinity chromatography with altered levels compared with age-matched controls included GP96, γ-enolase, glutamate dehydrogenase, glucosidase IIα, 14-3-3ϵ, 14-3-3γ, 14-3-3ζ, tropomyosin-2, calmodulin 2, gelsolin, β-synuclein, α1-antichymotrypsin, and dimethylguanosine tRNA methyltransferase. Proteins identified by proteomics that were fractionated from MCI and AD IPL by WGA affinity chromatography showing altered levels compared with age-matched controls included protein disulfide isomerase, calreticulin, and GP96. The proteins described in this study are involved in diverse processes, including glucose metabolism, endoplasmic reticulum (ER) functions, chaperoning, cytoskeletal assembly, and proteolysis, all of which are affected in AD. This study, the first to use proteomics to identify WGA-fractionated proteins isolated from brains from subjects with MCI and AD, provides additional information about the active proteome of the brain throughout AD progression.

Collapsin response mediator protein-2 is a calmodulin-binding protein

Collapsin response mediator protein-2 (CRMP-2) plays a crucial role in axonal guidance and neurite outgrowth during neural development and regeneration. We have studied the interaction between calmodulin (CaM) and CRMP-2 and how Ca(2+)/CaM binding modulates the biological functions of CRMP-2. We have shown that CRMP-2 binds to CaM directly in a Ca(2+)-dependent manner. The CaM binding site of CRMP-2 is proposed to reside in the last helix of the folded domain, and in line with this, a synthesized peptide representing this helix bound to CaM. In addition, CaM binding inhibits a homotetrameric assembly of CRMP-2 and attenuates calpainmediated CRMP-2 proteolysis. Furthermore, a CaM antagonist reduces the number and length of process induced by CRMP-2 overexpression in HEK293 cells. Take together, our data suggest that CRMP-2 is a novel CaM-binding protein and that CaM binding may play an important role in regulating CRMP-2 functions.

Characterization of the antinociceptive and anti-inflammatory activities of doxycycline and minocycline in different experimental models

Tetracyclines induce anti-inflammatory effects unrelated to their antimicrobial activities. We investigated the effect induced by minocycline and doxycycline in models of nociceptive and inflammatory pain, edema, fever, cell migration and formation of fibrovascular tissue, as these effects have not been fully investigated. Tetracyclines were administered via intraperitoneal route 1 h before the tests. Minocycline and doxycycline (100 mg/kg) inhibited the second phase of the formalin-induced nociceptive response in mice. Doxycycline (100 mg/kg) also inhibited the first phase. The nociceptive response induced by phorbol 12,13-didecanoate (PDD) in mice was inhibited by doxycycline (100 mg/kg). Furthermore, carrageenan-induced mechanical allodynia in rats was inhibited by doxycycline and minocycline (50 or 100 mg/kg). However, they did not enhance the latency in the hot-plate test. It is unlikely that antinociception resulted from motor incoordination or muscle relaxing effect, as both tetracyclines (100 mg/kg) did not impair the motor activity of mice in the rota-rod test. Doxycycline (50 or 100 mg/kg) or minocycline (50 or 100 mg/kg) inhibited carrageenan-induced paw edema in rats. However, only minocycline (100 mg/kg) inhibited PDD-induced edema. Carrageenan-induced leukocyte migration into the peritoneal cavity of rats was inhibited by both tetracyclines (100 mg/kg). Endotoxin-induced fever in rats was also inhibited by doxycycline (50 or 100 mg/kg) or minocycline (100 mg/kg). Finally, formation of fibrovascular tissue induced by subcutaneous implant of a cotton pellet in mice was inhibited by a 6-day administration of both tetracyclines (50 or 100 mg/kg day). Concluding, this study clearly shows the antinociceptive and anti-inflammatory activities of these second-generation tetracyclines.

Involvement of Ca2+- and cyclic adenosine monophosphate-mediated signaling pathways in photodynamic injury of isolated crayfish neuron and satellite glial cells

To investigate the mechanisms of oxidative injury of neurons and glia, we studied the photodynamic effect on isolated stretch receptor that consists of only two sensory neurons enwrapped by satellite glial cells. Photodynamic therapy (PDT), a potent inducer of oxidative stress, is a prospective method for destruction of brain tumors. PDT induced functional inactivation and necrosis of neurons, necrosis, apoptosis, and proliferation of glial cells. The roles of calmodulin, calmodulin-dependent kinase II, phospholipase C, protein kinases A and C, and phosphodiesterase in these processes were studied by using their inhibitors: fluphenazine, KN-93, D-609, H89, staurosporine, and papaverine, respectively. PDT-induced firing abolishment was enhanced by H89 or papaverine, whereas staurosporine acted oppositely. Fluphenazine or KN-93 reduced necrosis of neurons and glial cells. H89 enhanced necrosis of neurons, whereas staurosporine enhanced necrosis of glial cells. Inhibition of protein kinases A and C enhanced PDT-induced glial apoptosis. Photodynamic gliosis was prevented by KN-93 or staurosporine. These data indicate possible involvement of calmodulin and calmodulin-dependent kinase II in photoinduced necrosis of neurons and glia. Protein kinase C could protect glial cells from necrosis and apoptosis and participate in photoinduced gliosis and loss of neuronal activity. Protein kinase A maintained neuronal firing and protected neurons from photoinduced necrosis and glial cells from apoptosis. Phosphodiesterase reduced necrosis of photosensitized neurons and glia. Thus, Ca(2+)- and cAMP-mediated signaling pathways were involved in photooxidative injury of neurons and glia. Their pharmacological modulation may differently change the efficacy of photodynamic injury of neurons and glial cells.

Analysis of pThr286-CaMKII and CaMKII immunohistochemistry in the hippocampus of patients with temporal lobe epilepsy

Ca2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylates a variety of neuronal proteins, thereby, coordinating responses to changes of intracellular Ca2+ concentrations. Autophosphorylation at threonine286 generates an autonomously active form of CaMKII (pThr286-CaMKII), thus prolonging responses to transient increases in Ca2+. Our previous studies in hippocampi of temporal lobe epilepsy (TLE) patients revealed a significant up-regulation of CaMKII in dentate granule cells (DGCs) of specimens with Ammon's horn sclerosis (AHS). However, the functional status of the up-regulated enzyme remained unclear. Therefore, we performed double immunofluorescence staining for CaMKII and pThr286-CaMKII in hippocampi of TLE patients and controls. Furthermore, we analyzed the ratio of the relative fluorescence intensities pThr286-CaMKII: CaMKII in DGCs. CaMKII immunoreactivity was significantly increased in DGC bodies and their proximal dendrites in AHS. In contrast, immunostaining for pThr286-CaMKII was localized to the DGC bodies, revealing similar labeling intensities in all TLE and control specimens, and was not observed in the dendritic compartment of DGCs. Analysis of the ratio of the relative fluorescence intensities pThr286-CaMKII:CaMKII in DGC bodies revealed a significantly reduced ratio in AHS compared to lesion-associated TLE and controls. Thus, up-regulation of total CaMKII in DGCs of AHS specimens is not paralleled by an increase of its autonomously active form.

Modulation of calmodulin gene expression as a novel mechanism for growth hormone feedback control by insulin-like growth factor in grass carp pituitary cells

Calmodulin (CaM), the Ca2+ sensor in living cells, is essential for biological functions mediated by Ca2+-dependent mechanisms. However, modulation of CaM gene expression at the pituitary level as a means to regulate pituitary hormone synthesis has not been characterized. In this study we examined the functional role of CaM in the feedback control of GH by IGF using grass carp pituitary cells as a cell model. To establish the structural identity of CaM expressed in the grass carp, a CaM cDNA, CaM-L, was isolated from the carp pituitary using 3'/5' rapid amplification of cDNA ends. The open reading frame of this cDNA encodes a 149-amino acid protein sharing the same primary structure with CaMs reported in mammals, birds, and amphibians. This CaM cDNA is phylogenetically related to the CaM I gene family, and its transcripts are ubiquitously expressed in the grass carp. In carp pituitary cells, IGF-I and IGF-II induced CaM mRNA expression with a concurrent drop in GH transcript levels. These stimulatory effects on CaM mRNA levels were not mimicked by insulin and appeared to be a direct consequence of IGF activation of CaM gene transcription without altering CaM transcript stability. CaM antagonism and inactivation of calcineurin blocked the inhibitory effects of IGF-I and IGF-II on GH gene expression, and CaM overexpression also suppressed the 5' promoter activity of the grass carp GH gene. These results, as a whole, provide evidence for the first time that IGF feedback on GH gene expression is mediated by activation of CaM gene expression at the pituitary level.

Depolarization of neural cells induces transcription of the Down syndrome critical region 1 isoform 4 via a calcineurin/nuclear factor of activated T cells-dependent pathway

In this study we showed that the transcriptional regulation of Down syndrome critical region isoform 4 (DSCR1.4) is mediated by the calcineurin/nuclear factor of activated T cells (NFAT) pathway in neural cells. Stimuli that elicit an increase in the intracellular concentrations of calcium, such as membrane depolarization, induced de novo transcription of DSCR1.4, with mRNA expression peaking after 4 h and then declining. Action via the physiologically relevant L-type calcium channel was confirmed by blockade with nifedipine and verapamil. This calcium-dependent transcription of DSCR1.4 was inhibited by the calcineurin inhibitors cyclosporin A and FK506. Deletional analysis showed that the calcium- and calcineurin-dependent activation is mediated by the promoter region between nucleotides -350 and -166, a region that contains putative NFAT-binding motifs. Exogenous NFATc2 potently augmented the DSCR1.4 promoter transcriptional activity, and the involvement of endogenous NFAT signaling pathway in DSCR1.4 transcription was confirmed by the suppression of depolarization-inducible promoter activity with the NFAT inhibitor peptide VIVIT. Exogenous overexpression of DSCR1 protein (calcipressin 1) resulted in the inhibition of the transcription of DSCR1.4 and NFAT-dependent signaling. These findings suggest that calcineurin-dependent induction of DSCR1.4 product may represent an important auto-regulatory mechanism for the homeostatic control of NFAT signaling in neural cells.

Goldfish calmodulin: molecular cloning, tissue distribution, and regulation of transcript expression in goldfish pituitary cells

Calmodulin (CaM) is a Ca(2+)-binding protein essential for biological functions mediated through Ca(2+)-dependent mechanisms. In the goldfish, CaM is involved in the signaling events mediating pituitary hormone secretion induced by hypothalamic factors. However, the structural identity of goldfish CaM has not been established, and the neuroendocrine mechanisms regulating CaM gene expression at the pituitary level are still unknown. Here we cloned the goldfish CaM and tested the hypothesis that pituitary expression of CaM transcripts can be the target of modulation by hypothalamic factors. Three goldfish CaM cDNAs, namely CaM-a, CaM-bS, and CaM-bL, were isolated by library screening. These cDNAs carry a 450-bp open reading frame encoding the same 149-amino acid CaM protein, the amino acid sequence of which is identical with that of mammals, birds, and amphibians and is highly homologous (>/=90%) to that in invertebrates. In goldfish pituitary cells, activation of cAMP- or PKC-dependent pathways increased CaM mRNA levels, whereas the opposite was true for induction of Ca(2+) entry. Basal levels of CaM mRNA was accentuated by GnRH and pituitary adenylate cyclase-activating polypeptide but suppressed by dopaminergic stimulation. Pharmacological studies using D1 and D2 analogs revealed that dopaminergic inhibition of CaM mRNA expression was mediated through pituitary D2 receptors. At the pituitary level, D2 activation was also effective in blocking GnRH- and pituitary adenylate cyclase-activating polypeptide-stimulated CaM mRNA expression. As a whole, the present study has confirmed that the molecular structure of CaM is highly conserved, and its mRNA expression at the pituitary level can be regulated by interactions among hypothalamic factors.

Molecular Profiling of Experimental Parkinson's Disease: Direct Analysis of Peptides and Proteins on Brain Tissue Sections by MALDI Mass Spectrometry

Direct molecular profiling of biological samples using matrix-assisted laser desorption ionization mass spectrometry is a powerful tool for identifying phenotypic markers. In this report, protein profiling was used for the first time to generate peptide and protein profiles of brain tissue sections obtained from experimental Parkinson's disease (unilaterally 6-hydroxydopamine treated rats). The mass spectrometer was used to map the peptide and protein expression directly on 12 microm tissue sections in mass-to-charge (m/z) values, providing the capability of mapping specific molecules of the original sample, that is, localization, intensity and m/z ratio. Several protein expression profile differences were found in the dopamine depleted side of the brain when compared to the corresponding intact side, for example, calmodulin, cytochrome c, and cytochrome c oxidase. An increased ratio of post-translational modifications such as acetylations were found in the striatum of proteins in the dopamine depleted side of the brain. These modifications were decreased after subchronic administration of L-Dopa. The present study shows that unique protein profiles can be obtained in specific brain regions (and subregions) directly on brain tissue sections and allows for the study of complex biochemical processes such as those occurring in experimental Parkinson's disease.

The eag Potassium Channel Binds and Locally Activates Calcium/Calmodulin-dependent Protein Kinase II

Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the regulation of neuronal excitability in many systems. Recent studies suggest that local regulation of membrane potential can have important computational consequences for neuronal function. In Drosophila, CaMKII regulates the eag potassium channel, but if and how this regulation was spatially restricted was unknown. Using coimmunoprecipitation from head extracts and in vitro binding assays, we show that CaMKII and Eag form a stable complex and that association with Eag activates CaMKII independently of CaM and autophosphorylation. Ca(2+)/CaM is necessary to initiate binding of CaMKII to Eag but not to sustain association because binding persists when CaM is removed. The Eag CaMKII-binding domain has homology to the CaMKII autoregulatory region, and the constitutively active CaMKII mutant, T287D, binds Eag Ca(2+)-independently in vitro and in vivo. These results favor a model in which the CaMKII-binding domain of Eag displaces the CaMKII autoinhibitory region. Displacement results in autophosphorylation-independent activation of CaMKII which persists even when Ca(2+) levels have gone down. Activity-dependent binding to this potassium channel substrate allows CaMKII to remain locally active even when Ca(2+) levels have dropped, providing a novel mechanism by which CaMKII can regulate excitability locally over long time scales.

Ontogeny of calmodulin gene expression in rat brain

Calmodulin (CaM), a multifunctional intracellular calcium receptor, is a key element in signaling mechanisms. It is encoded in vertebrates by multiple apparently redundant genes (CaM I, II, III). To investigate whether differential expression takes place in the developing rat brain, a quantitative in situ hybridization analysis was carried out involving 15 brain areas at six ages between embryonic day 19 and postnatal day 20 (PD20) with gene-specific [(35)S]cRNA probes. A widespread, developmental stage-specific and differential expression of the three CaM genes was observed. The characteristic changes in the CaM mRNA levels in the examined time frame allowed the brain regions to be classified into three categories. For the majority of the areas (e.g. the piriform cortex for CaM III), the signal intensities peaked at around PD10 and the expression profile was symmetric (type 1). Other regions (e.g. the cerebral cortex, layer 1 for CaM II) displayed their highest signal intensities at the earliest age measured, followed by a gradual decrease (type 2). The signal intensities in the regions in the third group (e.g. the hypothalamus for CaM III) fluctuated from age to age (type 3). Marked CaM mRNA levels were measured for each transcript corresponding to the three CaM genes in the molecular layers of the cerebral and cerebellar cortici and hippocampus, suggesting their dendritic translocation. The highest signal intensity was measured for CaM II mRNA, followed by those for CaM III and CaM I mRNAs on PD1. However, the CaM II and CaM III mRNAs subsequently decreased steeply, while the CaM I mRNAs were readily detected even on PD20. Our results suggest that during development (1) the transcription of the CaM genes is under differential, area-specific control, and (2) a large population of CaM mRNAs is targeted to the dendritic compartment in a gene-specific manner.

Na(+)/Ca(2+) exchanger expression in the developing rat cortex

The Na(+)/Ca(2+) exchanger (NCX) participates in the regulation of neuronal Ca(2+) homeostasis and is also believed to be involved in the neuronal responses to hypoxia. However, there are very limited data on how NCX mRNA and protein expression are regulated during brain development. In the present study, we sought to elucidate the developmental expression of NCX1 and NCX2 in the rat cortex from late fetal to adult stages using reverse transcription-polymerase chain reaction and western blot assays. The primers for NCX1 mRNA targeted the alternative splicing domain to allow differentiation between NCX1 splice variants. Our results show that: (1) only two NCX1 mRNA splice variants (NCX1.5 and NCX1.4) are present in the cortex and their expression is age-dependent; (2) total NCX1 mRNA levels are low in fetal tissue, reach maximum density at postnatal day 8 and substantially decline with further maturation; (3) NCX2 mRNA density is significantly greater than total NCX1 mRNA for all ages and increases markedly during maturation from fetus/neonate to adult; and (4) NCX1 protein expression is lowest in late fetal cortex and reaches maximum levels after 2 weeks postnatally, even though expression levels are not significantly different between newborn and adult animals. Also, we found a similar NCX1 protein trend in the subcortical and cerebellar regions during development. From these data we suggest that NCX1 and NCX2 are differentially expressed in the cortex with a predominance of NCX2 levels during postnatal development. We speculate that the developmental increase in NCX2 expression is responsible for the overall increase in Na(+)/Ca(2+) exchange capacity during maturation.

Is neuroleptic malignant syndrome a neurogenic form of malignant hyperthermia?

Neuroleptic malignant syndrome is a rare and potentially lethal disorder associated with the use of antipsychotic medications. Heightened vigilance on the part of clinical providers has reduced morbidity and mortality caused by this disorder over the past decade, but there is still no consensus regarding its diagnosis, pathophysiology, or treatment. Efforts to demonstrate a direct link between neuroleptic malignant syndrome and malignant hyperthermia have been unsuccessful, indicating mutually distinct etiologies despite striking clinical similarities. This paper concisely reviews essential aspects of electromechanical transduction in muscle and nerve cells and current knowledge concerning the pathophysiology of malignant hyperthermia and neuroleptic malignant syndrome. Utilizing this conceptual framework, the author proposes that neuroleptic malignant syndrome may be caused by a spectrum of inherited defects in genes that are responsible for a variety of calcium regulatory proteins within sympathetic neurons or the higher order assemblies that regulate them. In this proposed model, neuroleptic malignant syndrome may be understood as a neurogenic form of malignant hyperthermia.

Differential calmodulin gene expression in the rodent brain

Apparently redundant members of the calmodulin (CaM) gene family encode for the same amino acid sequence. CaM, a ubiquitous cytoplasmic calcium ion receptor, regulates the function of a variety of target molecules even in a single cell. Maintenance of the fidelity of the active CaM-target interactions in different compartments of the cell requires a rather complex control of the total cellular CaM pool comprising multiple levels of regulatory circuits. Among these mechanisms, it has long been proposed that a multigene family maximizes the regulatory potentials at the level of the gene expression. CaM genes are expressed at a particularly profound level in the mammalian central nervous system (CNS), especially in the highly polarized neurons. Thus, in the search for clear evidence of the suggested differential expression of the CaM genes, much of the research has been focused on the elements of the CNS. This review aims to give a comprehensive survey on the current understanding of this field at the level of the regulation of CaM mRNA transcription and distribution in the rodent brain. The results indicate that the CaM genes are indeed expressed in a gene-specific manner in the developing and adult brain under physiological conditions. To establish local CaM pools in distant intracellular compartments (dendrites and glial processes), local protein synthesis from differentially targeted mRNAs is also employed. Moreover, the CaM genes are controlled in a unique, gene-specific fashion when responding to certain external stimuli. Additionally, putative regulatory elements have been identified on the CaM genes and mRNAs.

Signaling and gene expression in the neuron-glia unit during brain function and dysfunction: Holger Hydén in memoriam

Holger Hydén demonstrated almost 40 years ago that learning changes the base composition of nuclear RNA, i.e. induces an alteration in gene expression. An equally revolutionary observation at that time was that a base change occurred in both neurons and glia. From these findings, Holger Hydén concluded that establishment of memory is correlated with protein synthesis, and he demonstrated de novo synthesis of several high-molecular protein species after learning. Moreover, the protein, S-100, which is mainly found in glial cells, was increased during learning, and antibodies towards this protein inhibited memory consolidation. S-100 belongs to a family of Ca(2+)-binding proteins, and Holger Hydén at an early point realized the huge importance of Ca(2+) in brain function. He established that glial cells show more marked and earlier changes in RNA composition in Parkinson's disease than neurons. Holger Hydén also had the vision and courage to suggest that "mental diseases could as well be thought to depend upon a disturbance of processes in glia cells as in the nerve cells", and he showed that antidepressant drugs cause profound changes in glial RNA. The importance of Holger Hydén's findings and visions can only now be fully appreciated. His visionary concepts of the involvement of glia in neurological and mental illness, of learning being associated with changes in gene expression, and of the functional importance of Ca(2+)-binding proteins and Ca(2+) are presently being confirmed and expanded by others. This review briefly summarizes highlights of Holger Hydén's work in these areas, followed by a discussion of recent research, confirming his findings and expanding his visions. This includes strong evidence that glial dysfunction is involved in the development of Parkinson's disease, that drugs effective in mood disorders alter gene expression and exert profound effects on astrocytes, and that neuronal-astrocytic interactions in glutamate signaling, NO synthesis, Ca(2+) signaling, beta-adrenergic activity, second messenger production, protein kinase activities, and transcription factor phosphorylation control the highly programmed events that carry the memory trace through the initial, signal-mediated short-term and intermediate memory stages to protein synthesis-dependent long-term memory.

The role of calcineurin in lymphocyte activation

Lymphokine gene transcription involves numerous signal transduction molecules and second messengers. The serine/threonine phosphatase calcineurin has been demonstrated to play a central role in the immediate, early activation of numerous lymphokines (such as interleukin [IL]-2) and in the regulation of cell surface receptors such as CD40L, CD95, and recently CD25 alpha (the alpha chain of the IL-2 receptor). In addition to lymphocyte activation, calcineurin functions include control of neuronal signaling, muscle contraction, muscle hypertrophy and cellular death. Therefore, calcineurin not only plays a vital role in the regulation of T lymphocyte function, but also functions in cellular environments outside the immune system.