Modulation of a neuronal calmodulin mRNA species in the rat brain stem by reserpine

Cross talk among PMCA, calcineurin and NFAT transcription factors in control of calmodulin gene expression in differentiating PC12 cells

Brain aging is characterized by progressive loss of plasma membrane calcium pump (PMCA) and its activator - calmodulin (CaM), but the mechanism of this phenomenon remains unresolved. CaM encoded by three genes Calm1, Calm2, Calm3, works to translate Ca²⁺ signal into changes in frequently opposite cellular activities. This unique function allows CaM to affect gene expression via stimulation of calcineurin (CaN) and its downstream target - nuclear factor of activated T-cells (NFAT) and to terminate Ca²⁺ signal by stimulation of its extrusion. PMCA, which exists in four isoforms PMCA1-4, may in turn shape the pattern of Ca²⁺ transients and control CaN activity by its direct binding. Therefore, the interplay between PMCA, CaM and CaN/NFAT is highly plausible. To verify that, we used differentiated PC12 cells with reduced expression of PMCA2 or PMCA3 to mimic the potential changes in aged brain. Manipulation in PMCAs level decreased CaM protein in PMCA2 or PMCA3-reduced lines that was accompanied by down-regulation of Calm1 and Calm2 in both lines, but Calm3 only in PMCA2-reduced cells. Further studies showed substantially higher NFATc2 nuclear accumulation and increased NFAT transcriptional activity. Blocking of CaN/NFAT signalling resulted in almost full CaM recovery, mainly due to up-regulation of Calm2 and Calm3 genes. Moreover, higher occupancy of Calm2 and Calm3 promoters by NFATc2 and increased expression of these genes in response to NFATc2 silencing were demonstrated in PMCA2 and PMCA3-reduced lines. Our results indicate that decrease in CaM level in response to PMCAs downregulation can be driven by CaN/NFAT pathway.

Revisiting de Beer's textbook example of heterochrony and jaw elongation in fish: calmodulin expression reflects heterochronic growth, and underlies morphological innovation in the jaws of belonoid fishes

Background

Heterochronic shifts during ontogeny can result in adaptively important innovations and might be initiated by simple developmental switches. Understanding the nature of these developmental events can provide insights into fundamental molecular mechanisms of evolutionary change. Fishes from the Suborder Belonoidei display a vast array of extreme craniofacial morphologies that appear to have arisen through a series of heterochronic shifts. We performed a molecular heterochrony study, comparing postembryonic jaw development in representatives of the Suborder Belonoidei, the halfbeak Dermogenys pusilla (where the lower jaw is considerably elongated compared to the upper jaw) and the needlefish Belone belone (where both jaws are elongated), to a representative of their sister group the Suborder Adrianichthyoidei, the medaka Oryzias latipes, which has retained the ancestral morphology.

Results

Early in development, the lower jaw displays accelerated growth both in needlefish and halfbeak compared to medaka, and secondary acceleration of the upper jaw is seen in needlefish later in their development, representing a case of mosaic heterochrony. We identified toothless extensions of the dentaries as innovations of Belonoid fishes and the source of heterochronic growth. The molecular basis of growth heterochronies in the Belonoidei was examined through comparing expression of skeletogenic genes during development of halfbeak and medaka. The calmodulin paralogue calm1 was identified as a potential regulator of jaw length in halfbeak as its expression gradually increases in the lower jaw, but not the upper jaw, in a pattern that matches its outgrowth. Moreover, medaka displays equal expression of calm1 in the upper and lower jaws, consistent with the lack of jaw outgrowth in this species.

Conclusions

Heterochronic shifts in jaw growth have occurred repeatedly during the evolution of Belonoid fishes and we identify toothless extensions of the dentaries as an important innovation of this group. Our results suggest that calm1 contributes to jaw heterochrony in halfbeak, potentially driving further heterochronic shifts in jaw growth across the Suborder Belonoidei, such as the upper jaw acceleration observed in needlefish.

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.

Role of calmodulin in the differentiation/activation of microglial cells

In the present work the role of calmodulin (CaM) in regulating lipopolysaccharide (LPS)-induced microglial activation and in the spontaneous microglial differentiation has been investigated. We used pure rat microglial cell cultures to examine the effects of W13, a specific inhibitor of CaM, on microglial activation produced by LPS and the effect of CaM inhibition on microglial proliferation induced by the macrophage colony-stimulating factor (M-CSF). Microglial morphological transformation, inducible nitric oxide synthase (iNOS) activity and proliferating cell nuclear antigen (PCNA) immunostaining were determinate. Results show that CaM does not participate in the microglial increase of iNOS produced by LPS. In contrast, it is involved in spontaneous microglial ramification and in the activation of proliferation from quiescence. Multiple second-messenger pathways are involved in the transduction of signals initiated by LPS. The study of these mechanisms may allow us to extend our knowledge of the signals controlling the expression of these mediators.

The Ca2+/calmodulin system in neuronal hyperexcitability

Calmodulin (CaM) is a major Ca2+-binding protein in the brain, where it plays an important role in the neuronal response to changes in the intracellular Ca2+ concentration. Calmodulin modulates numerous Ca2+-dependent enzymes and participates in relevant cellular functions. Among the different CaM-binding proteins, the Ca2+/CaM dependent protein kinase II and the phosphatase calcineurin are especially important in the brain because of their abundance and their participation in numerous neuronal functions. Therefore, the role of the Ca2+/CaM signalling system in different neurotoxicological or neuropathological conditions associated to alterations in the intracellular Ca2+ concentration is a subject of interest. We here report different evidences showing the involvement of CaM and the CaM-binding proteins above mentioned in situations of neuronal hyperexcitability induced by convulsant agents. Signal transduction pathways mediated by specific CaM binding proteins warrant future study as potential targets in the development of new drugs to inhibit convulsant responses or to prevent or attenuate the alterations in neuronal function associated to the deleterious increases in the intracellular Ca2+ levels described in different pathological situations.

Multiple calmodulin genes exhibit systematically differential responses to chronic ethanol treatment and withdrawal in several regions of the rat brain

Ethanol induces profound alterations in the neuronal signaling systems, including the calcium (Ca(2+)) signaling. Prolonged exposure to ethanol evokes adaptive changes in the affected systems as they strive to restore the normal neuronal function. We investigated the involvement of calmodulin (CaM) genes, coding for the major mediator protein of intracellular Ca(2+) signals, in these adaptive processes at the mRNA level. The changes induced in the regional abundances of the CaM I, II, and III mRNA classes by chronic ethanol treatment and withdrawal were examined by means of quantitative in situ hybridization, employing gene-specific [35S]cRNA probes on rat brain cryostat sections. Regional analysis of the resulting changes in mRNA levels highlighted brain areas that belong in neuronal systems known to be especially sensitive to the action of ethanol. The results revealed systematically differential regulation for the three mRNA classes: the CaM I and CaM III mRNA levels displayed increases, and CaM II levels decreases in the affected brain regions, in both chronic ethanol- and withdrawal-treated animals. As regards the numbers of brain regions undergoing significant alterations in mRNA content, the CaM I mRNA levels exhibited changes in most brain areas, the CaM II levels did so in a lower number of brain regions, and the CaM III levels changed in only a few brain areas. These results suggest a differential regulation for the CaM genes in the rat brain and may help towards elucidation of the functional significance of the multiple CaM genes in the mammalian genome.

Differential regulation of calmodulin content and calmodulin messenger RNA levels by acute and repeated, intermittent amphetamine in dopaminergic terminal and midbrain areas

Repeated doses of psychoactive drugs often produce adaptive responses that differ from the initial drug application and additional adaptive processes occur following cessation of the drug. The relationship between alterations in calmodulin protein and messenger RNA produced by an initial versus a repeated dose of amphetamine was examined, as well as changes following drug cessation. Calmodulin protein and messenger RNA of the three individual calmodulin genes were measured in rat dopaminergic cell body and terminal areas following acute or repeated amphetamine. Rats were either injected once with 2.5mg/kg amphetamine or saline and decapitated after 3h, or given 10 injections of amphetamine three to four days apart and decapitated 3h after the final injection. Calmodulin messenger RNA and protein were also measured three and seven days after ceasing drug treatment. Acute amphetamine increased calmodulin 1.7-fold in the striatum and threefold in the ventral mesencephalon, with corresponding elevations in calmodulin messenger RNAs. In response to the 10th dose of amphetamine, however, the degree of increase in calmodulin was diminished in the striatum and ablated in the ventral mesencephalon. Correspondingly, select species of calmodulin messenger RNA were decreased from control levels. In the frontal cortex or nucleus accumbens, calmodulin levels were basically unaltered by the first or 10th doses of amphetamine, but both calmodulin and its messenger RNA were altered with time upon cessation of the drug. Three days later, both calmodulin protein and messenger RNA were decreased in select brain areas. By seven days after the 10th injection, calmodulin content was altered compared to saline controls in all areas, but the change in messenger RNA no longer paralleled the change in protein.Our findings demonstrate that both calmodulin protein and select species of calmodulin messenger RNA are altered by acute amphetamine, but this effect is attenuated after repeated, intermittent amphetamine. There are further time-dependent changes after cessation of repeated amphetamine, which may reflect compensatory neuronal responses. The alterations in calmodulin content and synthesis could contribute to changes in patterns or duration of behaviors that occur upon cessation of repeated amphetamine.

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

Ca2+ plays a critical role in the normal function of the central nervous system. However, it can also be involved in the development of different neuropathological and neurotoxicological processes. The processing of a Ca2+ signal requires its union with specific intracellular proteins. Calmodulin is a major Ca(2+)-binding protein in the brain, where it modulates numerous Ca(2+)-dependent enzymes and participates in relevant cellular functions. Among the different calmodulin-binding proteins, the Ca2+/calmodulin-dependent protein kinase II and the phosphatase calcineurin are especially important in the brain because of their abundance and their participation in numerous neuronal functions. We present an overview on different works aimed at the study of the Ca2+/calmodulin signalling system in the neural response to convulsant agents. Ca2+ and calmodulin antagonists inhibit the seizures induced by different convulsant agents, showing that the Ca2+/calmodulin signalling system plays a role in the development of the seizures induced by these agents. Processes occurring in association with seizures, such as activation of c-fos, are not always sensitive to calmodulin, but depend on the convulsant agent considered. We characterized the pattern of expression of the three calmodulin genes in the brain of control mice and detected alterations in specific areas after inducing seizures. The results obtained are in favour of a differential regulation of these genes. We also observed alterations in the expression of the Ca2+/calmodulin-dependent protein kinase II and calcineurin after inducing seizures. In addition, we found that reactive microglial cells increase the expression of calmodulin and Ca2+/calmodulin-dependent protein kinase II in the brain after seizures.

Identification of specific mRNAs affected by treatments producing long-term facilitation in Aplysia

Neural correlates of long-term sensitization of defensive withdrawal reflexes in Aplysia occur in sensory neurons in the pleural ganglia and can be mimicked by exposure of these neurons to serotonin (5-HT). Studies using inhibitors indicate that transcription is necessary for production of long-term facilitation by 5-HT. Several mRNAs that change in response to 5-HT have been identified, but the molecular events responsible for long-term facilitation have not yet been fully described. To detect additional changes in mRNAs, we investigated the effects of 5-HT (1.5 hr) on levels of mRNA in pleural-pedal ganglia using in vitro translation. Four mRNAs were affected by 5-HT, three of which were identified as calmodulin (CaM), phosphoglycerate kinase (PGK), and a novel gene product (protein 3). Using RNase protection assays, we found that 5-HT increased all three mRNAs in the pleural sensory neurons. CaM and protein 3 mRNAs were also increased in the sensory neurons by sensitization training. Furthermore, stimulation of peripheral nerves of pleural-pedal ganglia, an in vitro analog of sensitization training, increased the incorporation of labeled amino acids into CaM, PGK, and protein 3. These results indicate that increases in CaM, PGK, and protein 3 are part of the early response of sensory neurons to stimuli that produce long-term facilitation, and that CaM and protein 3 could have a role in the generation of long-term sensitization.

Calmodulin is expressed by reactive microglia in the hippocampus of kainic acid-treated mice

Calmodulin is a calcium-binding protein that is highly abundant in the brain, where it is involved in many essential functions. The protein is mainly expressed by neuronal cells. Calmodulin is encoded by three different genes in mammals, all of them producing an identical protein. Alterations in the expression of either calmodulin genes or protein have been reported in the rodent brain by several authors in different experimental situations. However, no mention has been made to date of possible alterations in calmodulin expression in glial cells in response to certain stimuli. In the present study, we found an increase in the expression of calmodulin in reactive microglial cells in the mouse hippocampus 24 h after an intraperitoneal administration of a convulsant dose of kainic acid. The results show that a high expression of calmodulin can be added to the list of changes described to occur in microglial cells when they become reactive microglia in response to certain kinds of stimuli, in contrast to the non-detectable level of expression of this protein observed in the resting microglial cells. It is difficult to explain such an increase due to the great number of processes in which calmodulin is involved, but the great level of calmodulin observed in the reactive microglial cells shows that calmodulin immunolabelling can be used to reveal these kinds of cells.

Alterations of calmodulin and its mRNA in rat brain after acute and chronic administration of methamphetamine

The effect of acute and chronic administration of methamphetamine (METH) on the levels of calmodulin (CaM) and its mRNAs has been investigated in rat brain using antisense oligonucleotides to three distinct rat CaM genes (CaM I, CaM II, CaM III). CaM I mRNA was reduced in the striatum and nucleus accumbens within 2 h of acute administration of 4 mg/kg METH, but returned to the control level by 6 h. The CaM content in both the cytosolic and membrane fractions of the striatum was reduced 0.5, 2, and 6 h after acute administration of METH. In the chronic experiments, rats were treated with either 4 mg/kg METH or saline once daily for 14 days. This was followed by a withdrawal period of 28 days, and thereafter, the animals were challenged with either METH (4 mg/kg, i.p.) or saline. All the animals were decapitated 6 h after this injection. There were four treatment groups: METH-METH (MM); METH-saline (MS); saline-METH (SM); and saline-saline (SS). There was a significant decrease in the mRNA for CaM I and CaM II in the striatum, and CaM II and CaM III in the nucleus accumbens in the MS group and the MS and MM groups, respectively, when compared to the SS group. The CaM content in the striatal membrane fraction decreased in both the SM and MS groups but not in the MM group. In contrast, the CaM content in the membrane fraction of the mesolimbic area showed a significant increase in the MM group. The CaM content in the cytosolic fraction of these brain areas decreased in both the SM and MM groups. The total CaM decreased significantly in the SM and MM groups of the striatum, but increased significantly in the MM group of the mesolimbic area. The mRNA for CaM I and CaM III decreased significantly in the MM group, and in the SM and MM groups, in the substantia nigra pars compacta (SNC) and ventral tegmental area (VTA), respectively. The CaM content in both the cytosolic and membrane fractions and total CaM content of the SN/VTA decreased significantly in the SM, MS and MM group as compared with the SS group. In the medial prefrontal cortex and hippocampus the significant increase of CaM content in the membrane fraction of the MM group was also found, but neither the CaM content in the cytosol fraction nor total CaM content changed. These results suggest that chronic METH administration leads to a translocation of CaM from the cytosolic to membrane fractions; these may underlie METH-induced behavioral sensitization.

Differential response of calmodulin genes in the mouse brain after systemic kainate administration

In the central nervous system, many of the effects resulting from an increase in the intracellular levels of calcium are mediated by calmodulin, a major calcium-binding protein in the mammalian brain. Calmodulin is expressed by three different genes, namely CaM I, CaM II and CaM III, all of which encode an identical protein. We studied the expression of calmodulin in the mouse brain at different times after the administration of a convulsant dose of kainate, a potent neuroexcitotoxic agent. We detected the presence of the different calmodulin messenger RNAs and of the protein itself in brain sections by in situ hybridization histochemistry and immunocytochemistry respectively. In addition, we determined the calmodulin content in brain regions by radioimmunoassay. Kainate-treated animals did not show areas of neuronal death at the different times following administration considered. An increase in the hybridization signal for CaM I messenger RNAs was observed from 5 h after kainate administration in the different brain regions tested. In contrast, the CaM II messenger RNA signal decreased gradually to a minimum 24 h after treatment in the hippocampus, while the CaM III messenger RNA signal was mostly unaffected. Calmodulin immunoreactivity also increased in the hippocampus. Nevertheless, we did not detect any significant difference in calmodulin content between brain regions of control and treated animals by radioimmunoassay. Kainate treatment induced modifications in the expression of calmodulin at the level of both messenger RNAs and protein. The results suggest a differential regulation of the three calmodulin genes in the adult mouse brain and a post-transcriptional or a post-translational regulation of calmodulin expression.

Comparative study of the pattern of expression of calmodulin messenger RNAs in the mouse brain

Calmodulin is a major calcium-binding protein in the mammalian brain, playing an important role in neuronal cell function. Its amino acid sequence is highly conserved and the protein is encoded by multiple genes. In the mouse brain, as well as in the rat and the human brain, three different genes have been detected for calmodulin, CaM I, CaM II and CaM III, all of which encode an identical protein. We studied the pattern of expression of the three calmodulin genes and the pattern of calmodulin distribution in the mouse brain by in situ hybridization histochemistry and immunohistochemistry. We found that calmodulin messenger RNAs from the three calmodulin genes were widely expressed in the mouse brain. Nevertheless, there were differences in their patterns of distribution. In general, all calmodulin messenger RNAs were preferentially distributed in hippocampus, cerebral cortex and cerebellar cortex, and CaM II messenger RNA also in caudate-putamen. However, all messenger RNAs showed clearly differentiated patterns of distribution in the hippocampus and the cerebellar cortex. Calmodulin immunoreactivity was present in all cells so far examined. Immunostaining was observed both in the cell nucleus, where it was especially strong, and in the cytoplasm. Our results suggest that the three calmodulin genes are differentially regulated in the mouse brain and also that, although all calmodulin genes have a basal expression, precise regulation of calmodulin levels might be attained through the different contribution of the three calmodulin genes.

CaM I mRNA is localized to apical dendrites during postnatal development of neurons in the rat brain

In the rat, a single calmodulin (CaM) protein is encoded by three separate genes which produce five different transcripts. The significance of the multiple CaM genes is not known; however, individual CaM transcripts could be targeted to specific intracellular sites. In this report, the cellular distribution of CaM I mRNAs was analyzed in the postnatal rat brain. The 4.0-kb CaM I transcript was present in neuronal cell bodies and also localized to apical dendritic processes. In cerebral cortical neurons, the 4.0-kb CaM I mRNA was detected in apical dendrites at postnatal day (PD) 5 to 15. In hippocampal neurons, this CaM message was present in dendritic processes from PD S to 20, whereas in Purkinje neurons it was detected in dendrites at PD 15 and 20. The presence of the 4.0-kb CaM I mRNA in dendrites of the rat brain supports the notion of targeting transcripts derived from the CaM multigene family to discrete intracellular destinations.

Alteration of CaM I mRNA expression in the developing rat superior colliculus following chronic treatment with an NMDA receptor antagonist

The spatial distribution of CaM I mRNA was investigated in the developing superior colliculus of rats that were chronically treated with the NMDA receptor antagonist AP-5. In control animals, CaM I message was localized in a continuous band of cells that extended across the entire rostro caudal axis of the superficial superior colliculus. Chronic AP-5 treatment resulted in a specific reduction of CaM I message in the caudal colliculus at postnatal day 10. Since normal NMDA receptor function has been implicated in activity dependent synaptic plasticity in the superior colliculus, these results suggest that the regulation of calmodulin may be part of a cascade of events that mediate this plasticity following NMDA receptor activation.

Developmental expression of calmodulin mRNA and protein in regions of the postnatal rat brain

The expression of calmodulin (CaM) protein and mRNA was analyzed in specific regions of the rat brain during postnatal development. CaM levels in the adult brain were more abundant in the cerebral hemispheres and thalamus compared to brain stem and superior plus inferior colliculus. All brain regions contained higher CaM protein and mRNA levels than in non-neural tissues such as the kidney. During postnatal development of the brain, maximal levels of CaM protein and CaM I mRNAs were attained at day 10 or 15. Protein levels declined thereafter in the adult in all regions except the thalamus. With respect to products of the rat CaM I gene, the 4.0 kb neural transcript demonstrated a pronounced increase during postnatal development, whereas the 1.8 kb message showed little change.

Effect of hexachlorocyclohexane isomers on calmodulin mRNA expression in the central nervous system

Three different calmodulin genes that encode the same protein have been found in the brain of all mammalian species so far examined. Little is known about the factors involved in regulating the expression of this gene family in the central nervous system. We have investigated the possibility of differential expression of two calmodulin genes, CaM I and CaM II, which are expressed strongly in neuronal cells in the adult rat brain, after treatment with the gamma (lindane) and the delta isomers of the hexachlorocyclohexane (HCH). In this study a decrease of CaM I mRNA (mainly in the 4.0 kb transcript) was found in the cortex of the rats after 24 h of isomer administration. CaM I expression seemed to be more sensitive to delta isomer action, whereas the gamma isomer acted mainly at CaM II level. The levels of mRNA of calmodulin CaM II gene were also found to decrease after lindane administration; delta-HCH produced an increase of this transcript. These results were obtained by Northern blot analysis and confirmed by means of in situ hybridization. Our results suggest that levels of neuronal calmodulin mRNA species are modified in response to changes in neuronal activity.

Calmodulin: effects of cell stimuli and drugs on cellular activation

The activity, localization and cellular content of CaM can be regulated by drugs, hormones and neurotransmitters. Regulation of physiological responses of CaM can depend upon local Ca(2+)-entry domains in the cells and phosphorylation of CaM target proteins, which would either decrease responsiveness of CaM target enzymes or increase CaM availability for binding to other target proteins. Despite the abundance of CaM in many cells, persistent cellular activation by a variety of substances can lead to an increase in CaM, reflected both in the nucleus and other cellular compartments. Increases in CaM-binding proteins can accompany stimuli-induced increases in CaM. A role for CaM in vesicular or protein transport, cell morphology, secretion and other cytoskeletal processes is emerging through its binding to cytoskeletal proteins and myosins in addition to the more often investigated activation of target enzymes. More complete knowledge of the physiological regulation of CaM can lead to a greater understanding of its role in physiological processes and ways to alter its actions through pharmacology.