Distribution and subcellular localization of calmodulin in adult and developing brain tissue

Mechanism of stress-induced attacks in an episodic neurologic disorder

Stress is the most common trigger among episodic neurologic disorders. In episodic ataxia type 2 (EA2), physical or emotional stress causes episodes of severe motor dysfunction that manifest as ataxia and dystonia. We used the tottering (tg/tg) mouse, a faithful animal model of EA2, to dissect the mechanisms underlying stress-induced motor attacks. We find that in response to acute stress, activation of α1-adrenergic receptors (α1-Rs) on Purkinje cells by norepinephrine leads to their erratic firing and consequently motor attacks. We show that norepinephrine induces erratic firing of Purkinje cells by disrupting their spontaneous intrinsic pacemaking via a casein kinase 2 (CK2)-dependent signaling pathway, which likely reduces the activity of calcium-dependent potassium channels. Moreover, we report that disruption of this signaling cascade at a number of nodes prevents stress-induced attacks in the tottering mouse. Together, our results suggest that norepinephrine and CK2 are required for the initiation of stress-induced attacks in EA2 and provide previously unidentified targets for therapeutic intervention.

Further Evidence of the Melatonin Calmodulin Interaction: Effect on CaMKII Activity

Melatonin (MEL) is a pleiotropic indolamine that reaches multiple intracellular targets. Among these, MEL binds to calmodulin (CaM) with high affinity. In presence of Ca²⁺, CaM binds to CaM-dependent kinase II (CaMKII). The Ca²⁺-CaM/CaMKII pathway regulates a myriad of brain functions in different cellular compartments. Evidence showing the regulation of this cellular pathway by MEL is scarce. Thus, our main objective was to study the interaction of MEL with CaM and its effects on CaMKII activity in two microenvironments (aqueous and lipidic) naturally occurring within the cell. In addition, colocalization of MEL with CaM in vivo was explored in mice brain hippocampus. In vitro CaM-MEL interaction and the structural conformations of CaM in the presence of this indoleamine were assessed through electrophoretic mobility and isoelectric point. The functional consequence of this interaction was evaluated by measuring CaMKII activity. Ca²⁺-CaM-MEL increased the activity of CaMKII in aqueous buffer but reduced the kinase activity in lipid buffer. Importantly, MEL colocalizes in vivo with Ca²⁺-CaM in the hippocampus. Our evidence suggests that MEL regulates the key cellular Ca²⁺-CaM/CaMKII pathway and might explain why physiological MEL concentrations reduce CaMKII activity in some experimental conditions, while in others it drives biological processes through activation of this kinase.

Calmodulin and Its Binding Proteins in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder that manifests with rest tremor, muscle rigidity and movement disturbances. At the microscopic level it is characterized by formation of specific intraneuronal inclusions, called Lewy bodies (LBs), and by a progressive loss of dopaminergic neurons in the striatum and substantia nigra. All living cells, among them neurons, rely on Ca²⁺ as a universal carrier of extracellular and intracellular signals that can initiate and control various cellular processes. Disturbances in Ca²⁺ homeostasis and dysfunction of Ca²⁺ signaling pathways may have serious consequences on cells and even result in cell death. Dopaminergic neurons are particularly sensitive to any changes in intracellular Ca²⁺ level. The best known and studied Ca²⁺ sensor in eukaryotic cells is calmodulin. Calmodulin binds Ca²⁺ with high affinity and regulates the activity of a plethora of proteins. In the brain, calmodulin and its binding proteins play a crucial role in regulation of the activity of synaptic proteins and in the maintenance of neuronal plasticity. Thus, any changes in activity of these proteins might be linked to the development and progression of neurodegenerative disorders including PD. This review aims to summarize published results regarding the role of calmodulin and its binding proteins in pathology and pathogenesis of PD.

Structures of AAA protein translocase Bcs1 suggest translocation mechanism of a folded protein

The mitochondrial membrane-bound AAA protein Bcs1 translocate substrates across the mitochondrial inner membrane without previous unfolding. One substrate of Bcs1 is the iron-sulfur protein (ISP), a subunit of the respiratory Complex III. How Bcs1 translocates ISP across the membrane is unknown. Here we report structures of mouse Bcs1 in two different conformations, representing three nucleotide states. The apo and ADP-bound structures reveal a homo-heptamer and show a large putative substrate-binding cavity accessible to the matrix space. ATP binding drives a contraction of the cavity by concerted motion of the ATPase domains, which could push substrate across the membrane. Our findings shed light on the potential mechanism of translocating folded proteins across a membrane, offer insights into the assembly process of Complex III and allow mapping of human disease-associated mutations onto the Bcs1 structure.

Calcium-binding protein and some neuropeptides in the retina of Octopus vulgaris: A morpho-histochemical study

The existence of both calcium-binding proteins (CBPs) and neuropeptides in the retina and brain of various species of vertebrates and invertebrates is well documented. Octopus retina is particularly interesting because it represents a case of convergent evolution. The aim of this study was to characterize the distribution of two CBPs, calretinin and calbindin, in Octopus retina using morphology, in situ hybridization, immunocytochemistry and Western blot. Calretinin-like immunoreactivity was found in the photoreceptor cells, but unexpectedly also in the supporting cells. In situ hybridization and Western blot analysis confirmed these results. No immunoreactivity was found for calbindin. Two neuropeptides, Substance P and calcitonin gene-related peptide (CGRP), as well as neurofilament protein and glial fibrillary acidic protein were also localized in the Octopus retina by immunocytochemistry. Our work provides new insights about calcium-binding proteins and neuropeptide distribution in Octopus retina and suggests a functional role for calretinin, a highly conserved protein, in visual signal transduction of cephalopods.

Calcium signals drive cell shape changes during zebrafish midbrain-hindbrain boundary formation

Calcium signals via calmodulin, myosin light chain kinase, and nonmuscle myosin II to mediate neuroepithelial apical-basal cell length during zebrafish brain morphogenesis.

One of the first morphogenetic events in the vertebrate brain is the formation of the highly conserved midbrain–hindbrain boundary (MHB). Specific cell shape changes occur at the point of deepest constriction of the MHB, the midbrain–hindbrain boundary constriction (MHBC), and are critical for proper MHB formation. These cell shape changes are controlled by nonmuscle myosin II (NMII) motor proteins, which are tightly regulated via the phosphorylation of their associated myosin regulatory light chains (MRLCs). However, the upstream signaling pathways that initiate the regulation of NMII to mediate cell shape changes during MHB morphogenesis are not known. We show that intracellular calcium signals are critical for the regulation of cell shortening during initial MHB formation. We demonstrate that the MHB region is poised to respond to calcium transients that occur in the MHB at the onset of MHB morphogenesis and that calcium mediates phosphorylation of MRLC specifically in MHB tissue. Our results indicate that calmodulin 1a (calm1a), expressed specifically in the MHB, and myosin light chain kinase together mediate MHBC cell length. Our data suggest that modulation of NMII activity by calcium is critical for proper regulation of cell length to determine embryonic brain shape during development.

Calmodulin inhibition regulates morphological and functional changes related to the actin cytoskeleton in pure microglial cells

The roles of calmodulin (CaM), a multifunctional intracellular calcium receptor protein, as concerns selected morphological and functional characteristics of pure microglial cells derived from mixed primary cultures from embryonal forebrains of rats, were investigated through use of the CaM antagonists calmidazolium (CALMID) and trifluoperazine (TFP). The intracellular localization of the CaM protein relative to phalloidin, a bicyclic heptapeptide that binds only to filamentous actin, and the ionized calcium-binding adaptor molecule 1 (Iba1), a microglia-specific actin-binding protein, was determined by immunocytochemistry, with quantitative analysis by immunoblotting. In unchallenged and untreated (control) microglia, high concentrations of CaM protein were found mainly perinuclearly in ameboid microglia, while the cell cortex had a smaller CaM content that diminished progressively deeper into the branches in the ramified microglia. The amounts and intracellular distributions of both Iba1 and CaM proteins were altered after lipopolysaccharide (LPS) challenge in activated microglia. CALMID and TFP exerted different, sometimes opposing, effects on many morphological, cytoskeletal and functional characteristics of the microglial cells. They affected the CaM and Iba1 protein expressions and their intracellular localizations differently, inhibited cell proliferation, viability and fluid-phase phagocytosis to different degrees both in unchallenged and in LPS-treated (immunologically challenged) cells, and differentially affected the reorganization of the actin cytoskeleton in the microglial cell cortex, influencing lamellipodia, filopodia and podosome formation. In summary, these CaM antagonists altered different aspects of filamentous actin-based cell morphology and related functions with variable efficacy, which could be important in deciphering the roles of CaM in regulating microglial functions in health and disease.

Neurogranin targets calmodulin and lowers the threshold for the induction of long-term potentiation

Calcium entry and the subsequent activation of CaMKII trigger synaptic plasticity in many brain regions. The induction of long-term potentiation (LTP) in the CA1 region of the hippocampus requires a relatively high amount of calcium-calmodulin. This requirement is usually explained, based on in vitro and theoretical studies, by the low affinity of CaMKII for calmodulin. An untested hypothesis, however, is that calmodulin is not randomly distributed within the spine and its targeting within the spine regulates LTP. We have previously shown that overexpression of neurogranin enhances synaptic strength in a calmodulin-dependent manner. Here, using post-embedding immunogold labeling, we show that calmodulin is not randomly distributed, but spatially organized in the spine. Moreover, neurogranin regulates calmodulin distribution such that its overexpression concentrates calmodulin closer to the plasma membrane, where a high level of CaMKII immunogold labeling is also found. Interestingly, the targeting of calmodulin by neurogranin results in lowering the threshold for LTP induction. These findings highlight the significance of calmodulin targeting within the spine in synaptic plasticity.

Calcium signaling in synapse-to-nucleus communication

Changes in the intracellular concentration of calcium ions in neurons are involved in neurite growth, development, and remodeling, regulation of neuronal excitability, increases and decreases in the strength of synaptic connections, and the activation of survival and programmed cell death pathways. An important aspect of the signals that trigger these processes is that they are frequently initiated in the form of glutamatergic neurotransmission within dendritic trees, while their completion involves specific changes in the patterns of genes expressed within neuronal nuclei. Accordingly, two prominent aims of research concerned with calcium signaling in neurons are determination of the mechanisms governing information conveyance between synapse and nucleus, and discovery of the rules dictating translation of specific patterns of inputs into appropriate and specific transcriptional responses. In this article, we present an overview of the avenues by which glutamatergic excitation of dendrites may be communicated to the neuronal nucleus and the primary calcium-dependent signaling pathways by which synaptic activity can invoke changes in neuronal gene expression programs.

Glutamate-induced calcium signals stimulate CO production in piglet astrocytes

Glutamate-stimulated, astrocyte-derived carbon monoxide (CO) causes cerebral arteriole dilation by activating smooth muscle cell large-conductance Ca(2+)-activated K(+) channels. Here, we examined the hypothesis that glutamate activates heme oxygenase (HO)-2 and CO production via the intracellular Ca(2+) concentration ([Ca(2+)](i))/Ca(2+)-calmodulin signaling pathway in newborn pig astrocytes. The major findings are: 1) glutamate stimulated Ca(2+) transients and increased steady-state [Ca(2+)](i) in cerebral cortical astrocytes in primary culture, 2) in astrocytes permeabilized with ionomycin, elevation of [Ca(2+)](i) concentration-dependently increased CO production, 3) glutamate did not affect CO production at any [Ca(2+)](i) when the [Ca(2+)](i) was held constant, 4) thapsigargin, a sarco/endoplasmic reticulum Ca(2+)-ATPase blocker, decreased basal CO production and blocked glutamate-induced increases in CO, and 5) calmidazolium, a calmodulin inhibitor, blocked CO production induced by glutamate and by [Ca(2+)](i) elevation. Taken together, our data are consistent with the hypothesis that glutamate elevates [Ca(2+)](i) in astrocytes, leading to Ca(2+)- and calmodulin-dependent HO-2 activation, and CO production.

Differential calmodulin gene expression in the nuclei of the rat midbrain-brain stem region

We investigated the expression patterns of the three calmodulin (CaM) genes, using in situ hybridization techniques, to detect gene-specific [(35)S]- and digoxigenin-labeled cRNA probes complementary to the multiple CaM mRNAs in the nuclei of the midbrain-brain stem region of the adult rat. The distinct CaM genes were widely expressed throughout this region with moderate intensities. In spite of the similar general pattern, significant differences in the distributions of the multiple CaM mRNA species were found in certain areas. In general, the CaM III mRNAs were most abundant, followed by the CaM I and CaM II mRNA populations. Most of the transcripts were found in the neuronal somata comprising the medullar nuclei, while much less label was detected in the neuropil. The CaM III mRNAs were more than 2.5 times more abundant than the CaM II mRNAs in the nucleus of the trapezoid body, and more than two times more abundant in the motor trigeminal nucleus, the principal sensory trigeminal nucleus and the olivary nucleus. The CaM III mRNAs were less dominant in the medial lemniscus, the inferior colliculus and the pontine reticular nucleus than those of the other CaM gene-specific transcripts. The CaM mRNA levels were low to moderate, without significant differences, in the mesencephalic trigeminal nucleus. The differential control of the expression of the CaM genes may contribute to the regulation of the multiple neuronal functions linked to this complex brain region and regulated by different CaM-dependent mechanisms via its target proteins.

Calmodulin spatial dynamics in RBL-2H3 mast cells

A line of rat basophilic leukaemia (RBL) cells, a model of mast cells, stably expressing EGFP-tagged calmodulin secreted normally in response to standard agonists. As reported for other cell types, calmodulin was concentrated in the mitotic spindle poles of dividing cells. In unstimulated interphase cells calmodulin was concentrated in the cell cortex and at a single central location. Disruption of cortical actin eliminated the concentration of calmodulin at the cortex while the central calmodulin concentration was associated with an enrichment of tubulin and is likely to represent the centrosome. Following stimulation with either an agonist that crosslinks Fc receptors or co-application of phorbol ester and a calcium ionophore the interior of the cells lost calmodulin while cortical fluorescence became more pronounced but also less uniform. After stimulation discrete bright puncta of calmodulin-EGFP (CaM-EGFP) appeared in the cell interior. Puncta colocalised with moving lysotracker-labelled granules, suggesting that calmodulin may play a role in organising their transport. Our results show that in interphase RBL cells a large fraction of the calmodulin pool is associated with targets in the actin cytoskeleton and demonstrate the utility of this model system for studying calmodulin biology.

Evidence of nuclear localization of neuronal nitric oxide synthase in cultured astrocytes of rats

With immunocytochemistry, we have observed the nuclear localization of neuronal nitric oxide synthase (nNOS) in cultured cerebral cortical astrocytes of rats. During the early six days in the subcultures of these cells, nNOS-immunoreactivity was mainly distributed in the cytoplasm. However, nNOS-immunoreactivity was mainly distributed in the nucleus at day 7, and this nuclear localization lasted about ten hours. Meanwhile, inducible nitric oxide synthase expression was significantly inhibited in these cells. Thereafter, nNOS-immunoreactivity was mainly distributed in the cytoplasm again. By confocal microscopy and western blot analysis, the phenomenon of nNOS nuclear localization was further confirmed; and the activity of nNOS in nuclear protein extracts from astrocytes of day 7-subculture could be detected using electron spin resonance (ESR) technique. These results may represent a new pathway of nitric oxide/nNOS participating in inducible nitric oxide synthase gene transcription regulation.

Calmodulin gene expression in the neural retina of the adult rat

Calmodulin (CaM) mRNAs are expressed with low abundancy in the adult rat neural retina. However, when digoxigenin (DIG)-labeled cRNA probes specific for each CaM mRNA population were hybridized at slightly alkaline pH (pH 8.0), the widespread distribution of CaM mRNA-expressing cells was revealed, with similar abundance for all three CaM genes. The CaM genes displayed a uniquely similar, layer-specific expression throughout the retina, and no significant differences were found in the distribution patterns of the CaM mRNA populations or the labeled cell types. The strongest signal for all CaM mRNAs was demonstrated in the ganglion cell layer and the inner nuclear layer, where the highest signal intensity was found within the inner sublamina. Similarly intermediate signal intensities for all CaM genes were detected in the inner and outer plexiform layers, within the vicinity of the outer limiting membrane and in the retinal pigment epithelium. A very low specific signal was characteristic in the outer nuclear layer and the photoreceptor inner segment layer, while no specific hybridization signal was observed in the photoreceptor outer segment layer. In summary, all CaM genes exhibited a similar and a characteristically layer-specific expression pattern in the adult rat retina.

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.

Differential expression of multiple calmodulin genes in cells of the white matter of the rat spinal cord

Calmodulin (CaM) displays complex cytoplasmic and synaptic functions in the nervous system. However, the very little information that is available on the gene expression of the multiple CaM genes in different glial cell types are from brain tissues of rodents, and no data have been published on their CaM gene expression in the spinal cord. Therefore, we have modified and tested a color in situ hybridization method sensitive enough to detect mRNA populations in cells with low CaM mRNA abundances in the white matter of the rat lumbar spinal cord. Morphologically, two distinct cell types expressing CaM mRNAs were detected. Differential CaM gene expression was demonstrated in medium-sized astrocyte-like cells that reside predominantly in the dorsal column of the spinal cord, where CaM I mRNA was most abundant, followed by the CaM III and CaM II mRNA populations. The oligodendrocytes displayed a less differential CaM gene expression in both the dorsal and the lateral columns, but the CaM I gene had a slightly higher expression level than those of the other CaM genes. The results indicate that the CaM gene expression profile of the spinal cord is richer and more complex than previously thought on the basis of conventional radioactive in situ hybridization techniques. Thus, when a method that is sufficiently sensitive was used, more cell types could be demonstrated to express CaM mRNAs; hence, in spite of their lower CaM expression, glial cells could also be visualized.

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.

Immunostaining of calmodulin and aluminium in Alzheimer's disease-affected brains

Previous in vitro studies have shown that Al(3+) binds to calmodulin, inducing alterations in its capability to interact with target proteins, accompanied by loss of immunological recognition by its conformational specific monoclonal antibody CAM1. In spite of the wealth of data of calmodulin action in vitro, little information is available on the possible involvement of this protein in the pathology typical of Alzheimer's disease. In the present study, we investigated calmodulin immunoreactivity in post-mortem human brains affected by Alzheimer's disease, compared with age-matched control brains. Conformational monoclonal antibodies raised against Ca(2+)-calmodulin, namely CAM1 and CAM4, were used in this study for the characterization of calmodulin. Calmodulin immunorecognition by monoclonal antibody CAM1 was found to be lost in cortical tissue sample from brains affected by Alzheimer's disease. This finding leads to the hypothesis of a new, possibly inactive, conformation of the molecule during the disease. On the other hand, CAM4 immunoreactivity was decreased in neurons of brains affected by Alzheimer's disease. Anti-Al(3+) monoclonal antibodies revealed instead more marked aluminium immunoreactivity in the affected brains compared to normal ones. The loss of CAM1 immunoreactivity and the occurrence of large amounts of aluminium suggest an alteration of the active conformation of calmodulin in disease-affected brains. These alterations could be involved in the development of Alzheimer's disease pathology.

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.

Regulation of dendritic spine stability

Dendritic spines undergo several types of transformations, ranging from growth to collapse, and from elongation to shortening, and they experience dynamic morphological activity on a rapid time scale. Changes in spine number and morphology occur under pathological conditions like excitotoxicity, but also during normal central nervous system development, during hormonal fluctuations, and in response to neural activity under physiological circumstances. We briefly review evidence for various types of alterations in spines, and discuss the possible molecular basis for changes in spine stability. Filamentous actin appears to be the most important cytoskeletal component of spines, and a growing list of actin-associated and actin-regulatory proteins has been reported to reside within spines. We conclude that spines contain two distinct pools of actin filaments (one stable, the other unstable) that provide the spine with both a stable core structure and a dynamic, complex shape. Finally, we review the current state of knowledge of actin filament regulation, based on studies in nonneuronal cells.

Quantitative imaging of tyrosine hydroxylase and calmodulin in the human brain

The distributions of tyrosine hydroxylase and calmodulin in adult normal postmortem human brain were analyzed quantitatively. Consecutive coronal sections were obtained from the anterior area of the right hemisphere and were stained immunohistochemically for tyrosine hydroxylase and calmodulin. Stained sections were divided into approximately 3 million microareas at 50 microm intervals, and the immunohistochemical fluorescence intensity in each area was measured by a human brain mapping analyzer, which is a microphotometry system for analysis of the distribution of neurochemicals in a large tissue slice. Immunoreactive staining of tyrosine hydroxylase and calmodulin was observed in almost all brain regions, but its intensity varied. Relatively high levels of calmodulin were observed in brain regions with high levels of tyrosine hydroxylase, though high levels of tyrosine hydroxylase were not always observed in brain regions where high levels of calmodulin were distributed. In particular, high levels of both of tyrosine hydroxylase and calmodulin were distributed in the caudate nucleus and putamen. Previously it was shown that tyrosine hydroxylase was activated and dopamine synthesis was enhanced in the neostriatum region in mice and rats by the intracerebroventricular administration of calcium through a calmodulin-dependent system. The present results combined with these previous findings suggest that the activity of tyrosine hydroxylase in the caudate nucleus and putamen of humans may also be regulated by a calcium/calmodulin-dependent system.

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.

Actin-associated protein synaptopodin in the rat hippocampal formation: localization in the spine neck and close association with the spine apparatus of principal neurons

Dendritic spines are sites of synaptic plasticity in the brain and are capable of remodeling their shape and size. However, little is known about the cellular mechanisms that regulate spine morphology and motility. Synaptopodin is a recently described actin-associated protein found in renal podocytes and dendritic spines (Mundel et al. J Cell Biol. [1997] 139:193-204), which is believed to play a role in spine plasticity. The present study analyzed the distribution of synaptopodin in the hippocampal formation. In situ hybridization histochemistry revealed a high constitutive expression of synaptopodin mRNA in the principal cell layers. Light microscopic immunohistochemistry showed that the protein is distributed throughout the hippocampal formation in a region- and lamina-specific manner. Postembedding immunogold histochemistry demonstrated that synaptopodin is exclusively present in dendrites and spines, specifically in the spine neck in close association with the spine apparatus. Spines lacking a spine apparatus are not immunoreactive for synaptopodin. These data suggest that synaptopodin links the spine apparatus to actin and may thus be involved in the actin-based plasticity of spines.

Water deprivation upregulates the three calmodulin genes in exclusively the supraoptic nucleus of the rat brain

Calmodulin (CaM), the ubiquitous intracellular calcium-binding protein, is coded by three bona fide CaM genes (CaM I, CaM II and CaM III) in mammals. They code for the same protein and are transcribed at particularly high levels in the brain, where CaM plays an essential role in basic neuronal functions. In this study, the expression of the three CaM genes in response to osmotic stimuli by water deprivation was investigated in the rat brain, with particular interest as concerns the hypothalamic magnocellular nuclei. CaM mRNA levels were determined by quantitative in situ hybridization autoradiography with gene-specific [35S]cRNA probes. In response to osmotic challenge, it was found that upregulation of the three CaM genes participates in the activation of the hypothalamo-hypophyseal system in the supraoptic nucleus (SON) (126% to 169%), but not in the magnocellular part of the paraventricular hypothalamic nucleus (PVN) (-10%). CaM mRNA levels decreased by 10%-15% in the suprachiasmatic nucleus (SCh) and many other extrahypothalamic brain areas. The opposite responses of the CaM gene expression in the SON and the magnocellular part of the PVN suggest a functional difference between them. Moreover, the significantly different magnitudes of the changes in the CaM mRNA levels in the SON nucleus (138%, 126% and 169% for CaM I, CaM II and CaM III, respectively) exemplify the precise differential control of the CaM gene expression in the brain.

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.

Differential distribution and intracellular targeting of mRNAs corresponding to the three calmodulin genes in rat brain. A quantitative in situ hybridization study

To investigate the pattern of expression of the three calmodulin (CaM) genes by in situ hybridization, gene-specific [35S]-cRNA probes complementary to the multiple CaM mRNAs were hybridized in rat brain sections and subsequently detected by quantitative film or high-resolution nuclear emulsion autoradiography. A widespread and differential area-specific distribution of the CaM mRNAs was detected. The expression patterns corresponding to the three CaM genes differed most considerably in the olfactory bulb, the cerebral and cerebellar cortices, the diagonal band, the suprachiasmatic and medial habenular nuclei, and the hippocampus. Moreover, the significantly higher CaM I and CaM III mRNA copy numbers than that of CaM II in the molecular layers of certain brain areas revealed a differential dendritic targeting of these mRNAs. The results indicate a differential pattern of distribution of the multiple CaM mRNAs at two levels of cellular organization in the brain: (a) region-specific expression and (b) specific intracellular targeting. A precise and gene-specific regulation of synthesis and distribution of CaM mRNAs therefore exists under physiological conditions in the rat brain.

Developmental regulation and tissue-specific localization of calmodulin mRNA in the protochordate Ciona intestinalis

A full-length cDNA encoding a highly conserved calmodulin was isolated from a cDNA library prepared from hatched larvae of the ascidian Ciona intestinalis. Sequence analysis has identified a 447 b.p. open reading frame, encoding a putative protein of 149 amino acid residues, with a predicted molecular weight of 16.8 kDa, showing 85-98% identity to known calmodulins. Northern blot analysis revealed a single transcript of about 0.8 kb in length, which was maternally expressed and progressively increased during development, until late tail-bud stage. Whole-mount in situ hybridizations, carried out on embryos at different stages of development, showed that starting from the neurula stage, the C. intestinalis calmodulin (Ci-CaM) expression became restricted to the neuroectoderm and that in larvae it was specifically detected in the nervous system.

Immunocytochemical changes of cytoskeleton components and calmodulin in the frog cerebellum and optic tectum during hibernation

During hibernation, variation in the metabolism of nerve cells occurs. Since the cytoskeleton plays an important role in nerve cell function, we have analyzed the immunocytochemical expression of two cytoskeleton components, i.e. phosphorylated 200 kDa neurofilament protein, and microtubule-associated protein 2 in the cerebellum and optic tectum of hibernating frogs (Rana esculenta) in comparison with active animals. In addition, we have considered the immunocytochemical expression of calmodulin, which is known to be involved in neurofilament phosphorylation. In hibernating animals, there was a decrease in the immunoreactivity for phosphorylated 200 kDa neurofilament protein and microtubule-associated protein 2 of fibers in both the cerebellum and in the optic tectum. In contrast, in the large neurons of the cerebellum, i.e. Purkinje neurons, there was an increase in the immunoreactivity for microtubule-associated protein 2. The changes in the cytoskeleton components were accompanied by a decrease in calmodulin immunoreactivity in the cytoplasm of nerve cells of the cerebellum. All the changes observed are consistent with a low neuronal activity during hibernation, as also indicated by previous microdensitometric and microfluorometric data. This shows a higher degree of chromatin condensation in hibernating animals and suggests that hibernation represents a simple form of neuronal plasticity.

Ultrastructural co-localization of calmodulin and B-50/growth-associated protein-43 at the plasma membrane of proximal unmyelinated axon shafts studied in the model of the regenerating rat sciatic nerve

Calmodulin and de-phosphorylated B-50/growth-associated protein-43 (GAP-43) have been shown to bind in vitro in a molecular complex, but evidence for an in situ association in the nervous system does not exist. Previously, we have reported that, in the model of the regenerating rat sciatic nerve, the B-50/GAP-43 immunoreactivity is increased and concentrated at the axolemma of unmyelinated axons located proximal to the site of injury and axon outgrowth. To explore a putative function of B-50/GAP-43, namely, the capacity of binding calmodulin to the plasma membrane, we examined the ultrastructural distribution of calmodulin in the proximal unmyelinated axon shafts of this model, using double immunolabelling and detection by fluorescent or gold probes conjugated to second antibodies. Immunofluorescence showed that seven days post-sciatic nerve crush the calmodulin immunoreactivity, similar to B-50/GAP-43 immunoreactivity, was intense in unmyelinated axon shafts located proximal to the site of injury of the regenerating nerve. Ultrastructurally, calmodulin was located at the axolemma of these regenerating unmyelinated axon shafts and inside the axoplasm, where it was associated with vesicles and microtubules. The plasma membrane labelling (approximately 69%) was significantly higher than the axoplasmic labelling. Over 60% of the plasma membrane-associated calmodulin co-localized with B-50/GAP-43 in a non-random distribution. Since normally calmodulin is largely present in the cytoplasm, these data suggest that calmodulin has been concentrated at the plasma membrane of unmyelinated axons, most probably by B-50/GAP-43. If the concentrating effect is due to B-50/GAP-43, then there is a possibility that these proteins may be present as a molecular complex in situ. The physiological significance could be that this association regulates the local availability of both B-50/GAP-43 and calmodulin for other interactions.

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.

Direct modulation of calmodulin targets by the neuronal calcium sensor NCS-1

Ca2+ and its ubiquitous intracellular receptor calmodulin (CaM) are required in the nervous system, among a host of cellular responses, for the modulation of several important enzymes and ion channels involved in synaptic efficacy and neuronal plasticity. Here, we report that CaM can be replaced by the neuronal calcium sensor NCS-1 both in vitro and in vivo. NCS-1 is a calcium binding protein with two Ca(2+)-binding domains that shares only 21% of homology with CaM. We observe that NCS-1 directly activates two Ca2+/CaM-dependent enzymes (3':5'-cyclic nucleotide phosphodiesterase and protein phosphatase calcineurin). Co-activation of nitric oxide synthase by NCS-1 and CaM results in a higher activity than with CaM alone. Moreover, NCS-1 is coexpressed with calcineurin and nitric oxide synthase in several neuron populations. Finally, injections of NCS-1 into calmodulin-defective cam1 Paramecium partially restore wildtype behavioral responses. With this highly purified preparation of NCS-1, we have obtained crystals suitable for crystallographic structure studies. NCS-1, despite its very different structure, distribution, and Ca(2+)-binding affinity as compared with CaM, can substitute for or potentiate CaM functions. Therefore, NCS-1 represents a novel protein capable of mediating multiple Ca(2+)-signaling pathways in the nervous system.

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.

Signaling from synapse to nucleus: postsynaptic CREB phosphorylation during multiple forms of hippocampal synaptic plasticity

Phosphorylation of the transcription factor CREB is thought to be important in processes underlying long-term memory. It is unclear whether CREB phosphorylation can carry information about the sign of changes in synaptic strength, whether CREB pathways are equally activated in neurons receiving or providing synaptic input, or how synapse-to-nucleus communication is mediated. We found that Ca(2+)-dependent nuclear CREB phosphorylation was rapidly evoked by synaptic stimuli including, but not limited to, those that induced potentiation and depression of synaptic strength. In striking contrast, high frequency action potential firing alone failed to trigger CREB phosphorylation. Activation of a submembranous Ca2+ sensor, just beneath sites of Ca2+ entry, appears critical for triggering nuclear CREB phosphorylation via calmodulin and a Ca2+/calmodulin-dependent protein kinase.

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.

The calmodulin-binding domain in the mouse type 1 inositol 1,4,5-trisphosphate receptor

We determined the amino acid sequence responsible for the calmodulin (CaM)-binding ability of mouse type 1 Ins(1,4,5)P3 receptor (IP3R1). We expressed various parts of IP3R1 from deleted cDNA and examined their CaM-binding ability. It was shown that the sequence stretching from Lys-1564 to Arg-1585 is necessary for the binding. The full-length IP3R1 with replacement of Trp-1576 by Ala lost its CaM-binding ability. Antibody against residues 1564-1585 of IP3R1 inhibited cerebellar IP3R1 from binding CaM. The fluorescence spectrum of the peptide that corresponds to residues 1564-1585 shifted when Ca(2+)-CaM was added. From the change in the fluorescence spectrum, we estimated the dissociation constant (KD) between the peptide and CaM to be 0.7 microM. The submicromolar value of KD suggests an actual interaction between CaM and IP3R1 within cells. The CaM-binding ability of other types of IP3Rs was also examined. A part of the type 2IP3R, including the region showing sequence identity with the CaM-binding domain of IP3R1, also bound CaM, while the expressed full-length type 3 IP3R did not.

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.

The cerebral neurons of Helix aspersa during hibernation. Changes in the cytochemical detection of calmodulin, cytoskeletal components and phosphatases

Some markers of the intracellular systems that regulate neuronal activity and morphology were analyzed in the cerebral ganglion of hibernating snails (Helix aspersa), in comparison with active animals. The immunocytochemical expression of a calcium-binding protein, i.e. calmodulin, and some cytoskeletal components, i.e. 200 kDa phosphorylated neurofilament protein (pNFH), microtubule associated protein 2 (MAP2) and alpha-tubulin were analyzed by the use of a panel of antibodies raised against mammal antigens. Moreover, by enzymatic reactions the Ca(2+)-ATPase and alkaline phosphatase (AIPase) activities were demonstrated. In comparison with the active phase, the hibernation induced an increase in the immunopositivity for calmodulin in all the neurons. The increase may be linked to unmasking of immunoreactive epitopes due to conformational changes of the protein, which in turn may be a consequence of a reduction or absence of binding with calcium ions or of a real increase in the amount of calmodulin in the somata of neurons. In any event, both the hypotheses indicate that neurons have decreased or suppressed the Ca(2+)-dependent mechanisms as also shown by the lower Ca(2+)-ATPase activity. Nevertheless, the AIPase activity, which was localized in the epineural sheat, was not significantly changed during hibernation and this supports that some metabolic activities are preserved in the hibernated animals. Changes in the immunopositivity for cytoskeletal components were found. There was an increase in the epitopes recognized by the mammalian pNF antibody, that concerned both the positivity of the entire cytoplasm of some clusters of metacerebral neurons and the intensity of the reaction. This would be aimed to improve the stability of the somata and primary neurites. Moreover, the decrease of alpha-tubulin and MAP2 immunopositivity, suggests that a disassembly of microtubules have occurred. The findings indicate that the transport of vesicles in the axons is slowed down during hibernation. In fact, research in progress show that the patterns of neurotransmission and neuromodulation are also deeply modified.

The role of calcium-binding proteins in selective motoneuron vulnerability in amyotrophic lateral sclerosis

The factors contributing to selective motoneuron loss in amyotrophic lateral sclerosis (ALS) remain undefined. To investigate whether calcium-binding proteins contribute to selective motoneuron vulnerability in ALS, we compared calbindin-D28K and parvalbumin immunoreactivity in motoneuron populations in human ALS, and in a ventral spinal cord hybrid cell line selectively vulnerable to the cytotoxic effects of ALS IgG. In human autopsy specimens, immunoreactive calbindin-D28k and parvalbumin were absent in motoneuron populations lost early in ALS (i.e., cortical and spinal motoneurons, lower cranial nerve motoneurons), while motoneurons damaged late or infrequently in the disease (i.e., Onuf's nucleus motoneurons, oculomotor, trochlear, and abducens nerve neurons) expressed markedly higher levels of immunoreactive calbindin-D28K and/or parvalbumin. Motoneuron-neuroblastoma VSC 4.1 hybrid cells lost immunoreactive calbindin-D28k and parvalbumin following dibutyryl-cyclic AMP-induced differentiation and were killed by IgG from ALS patients. Undifferentiated calbindin/parvalbumin-reactive VSC 4.1 cells were not killed, nor were other cell lines expressing high levels of calbindin-D28K and parvalbumin immunoreactivity (substantia nigra-neuroblastoma hybrid cells and N18TG2 neuroblastoma parent cells). These studies suggest that decreased calbindin-D28K and parvalbumin immunoreactivity may help explain the selective vulnerability of motoneurons in ALS.

Postsynaptic integration of glutamatergic and dopaminergic signals in the striatum

The aim of this study was to achieve a better understanding of the integration in striatal medium-sized spiny neurons (MSNs) of converging signals from glutamatergic and dopaminergic afferents. The review of the literature in the first section shows that these two types of afferents not only contact the same striatal cell type, but that individual MSNs receive both a corticostriatal and a dopaminergic terminal. The most common sites of convergence are dendritic shafts and spines of MSNs with a distance between the terminals of less than 1-2 microns. The second section focuses on synaptic transmission and second messenger activation. Glutamate, the candidate transmitter of corticostriatal terminals, via different types of glutamate receptors can evoke an increase in intracellular free calcium concentrations. The net effect of dopamine in the striatum is a stimulation of adenylate cyclase activity leading to an increase in cAMP. The subsequent sections present information on calcium- and cAMP-sensitive biochemical pathways and review the regional and subcellular distribution of the components in the striatum. The specific biochemical reaction steps were formalized as simplified equilibrium equations. Parameter values of the model were chosen from published experimental data. Major results of this analysis are: at intracellular free calcium concentrations below 1 microM the stimulation of adenylate cyclase by calcium and dopamine is at least additive in the steady state. Free calcium concentrations exceeding 1 microM inhibit adenylate cyclase, which is not overcome by dopaminergic stimulation. The kinases and phosphatases studied can be divided in those that are almost exclusively calcium-sensitive (PP2B and CaMPK), and others that are modulated by both calcium and dopamine (PKA and PP1). Maximal threonine-phosphorylation of the phosphoprotein DARPP requires optimal concentrations of calcium (about 0.3 microM) and dopamine (above 5 microM). It seems favourable if the glutamate signal precedes phasic dopamine release by approximately 100 msec. The phosphorylation of MAP2 is under essentially calcium-dependent control of at least five kinases and phosphatases, which differentially affect its heterogeneous phosphorylation sites. Therefore, MAP2 could respond specifically to the spatio-temporal characteristics of different intracellular calcium fluxes. The quantitative description of the calcium- and dopamine-dependent regulation of DARPP and MAP2 provides insights into the crosstalk between glutamatergic and dopaminergic signals in striatal MSNs. Such insights constitute an important step towards a better understanding of the links between biochemical pathways, physiological processes, and behavioural consequences connected with striatal function. The relevance to long-term potentiation, reinforcement learning, and Parkinson's disease is discussed.

A comparative study of the calcium-binding proteins calbindin-D28K, calretinin, calmodulin and parvalbumin in the rat spinal cord

Comparison of the immunocytochemical localizations revealed distinct patterns of differential distribution and overlapping of calbindin-D28K (CB-D28K), calretinin (CR), calmodulin (CM) and parvalbumin (PV) in the rat spinal cord. In some areas, one of the four calcium-binding proteins (CBPs) appears to be predominant, for example, CB-D28K in lamina I and ependymal cells, PV at the inner part of laminae II, CR in laminae V and VI and CM in motoneurons of lamina IX. In other regions of the spinal cord, more than one CBPs was abundant. CB-D28K and CR were similarly distributed in lamina II and the lateral spinal and cervical nucleus; CM and PV were similarly abundant in the ventromedial dorsal horn, internal basilar and central cervical nucleus; CR and PV were similarly abundant in the ventromedial dorsal horn, internal basilar and central cervical nucleus; CR and PV were similarly heterogeneous in the gracile fasciculus from caudal to rostral spinal cord. In the sacral dorsal gray commissure, the distribution patterns of CR and PV were clearly complementary. The unilateral ganglionectomies resulted in a substantial reduction of CBP-like immunoreactivity (CBP-LI) in the dorsal columns and a reduction of CM- and PV-LI in the ventromedial dorsal horn. In the motor system, only CM labeled large motoneurons in lamina IX and CB-D28K lightly stained pyramidal tract. The apparent absence of CM-LI in the superficial dorsal horn is contradictory to the presence of a CM-dependent nitric oxide synthase in the region. These data indicate that most CBP-LI in the dorsal column pathway had primary afferent origin, while the superficial dorsal horn exhibited intrinsic CBP immunoreactivity. The differential and selective localizations of CBPs in the spinal cord suggest a role for these proteins in spinal nociceptive processing, visceral regulation and dorsal column sensory pathways.

Expression of three nonallelic genes coding calmodulin exhibits similar localization on the central nervous system of adult rats

By Northern blot analysis with the digoxigenin-labeled antisense RNA probes of the noncoding regions, the transcripts of three calmodulin (CaM) genes, CaMI, CaMII, and CaMIII, were separately detected in 12 different tissues of adult Wistar albino rats, without any cross-hybridization. The mRNAs of all three CaM genes were abundant in the central nervous system (CNS) as well as in the testis, although ubiquitous expression was detected at low levels in the other tissues. There were subtle but significant differences in the tissue-specific distribution of the three CaM gene RNAs. By in situ hybridization, strong hybridization of the three CaM gene probes was observed in common in large projection neurons of the CNS: the hippocampal pyramidal cells, the cerebellar Purkinje cells, and the large neurons of the cerebral neocortex, the pyriform cortex, the mesencephalon, the pons, and the spinal cord. The expression of the three CaM genes was at lower levels in small interneurons of the CNS. These profiles of expression were almost the same among the three CaM genes. Thus, all three CaM genes were coordinately expressed in neurons of the adult rat CNS. Certain regulatory mechanisms of the three CaM genes seemed to mediate similar tissue- and cell type-specific expression in the CNS.

Reduction of calbindin-28k mRNA levels in Alzheimer as compared to Huntington hippocampus

Disturbances in calcium homeostasis have been observed to be associated with Alzheimer's and other neurodegenerative diseases. Increased total calcium levels and decreased levels of calcium binding proteins have been found in Alzheimer brain tissue. However, the mechanism behind these disturbances remain unknown. In situ hybridization with tritiated antisense RNA probes for the calcium binding proteins, calbindin-28k and calmodulin, was used to examine the expression of genes coding for these proteins in Alzheimer and Huntington brain tissues matched for age, agonal process and autopsy interval. mRNA levels for calbindin-28k were reduced by 35% in CA1 and CA2 regions of Alzheimer hippocampus, as compared to Huntington control. In contrast, calmodulin expression was unchanged in CA1 but reduced by 30% in CA2. mRNA expression of calbindin-28k and calmodulin in Alzheimer temporal cortex did not differ from control. There were no significant differences in calcium binding protein message levels in cerebellar Purkinje cells between Alzheimer and Huntington control. There was no correlation between calcium binding protein message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, decreased calbindin-28k expression in Alzheimer-affected hippocampus was due to an increase in the percentage of neurons expressing lower message levels for these proteins.

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

Reserpine evokes transsynaptic impulse activity by depleting catecholaminergic neurotransmitters in the rat brain. Previous studies suggest a relationship between catecholaminergic activity and calmodulin concentration. In this report we employ Northern blot analysis to examine the effect of a single subcutaneous injection of reserpine on levels of calmodulin mRNA species which are preferentially expressed in neurons of the rat brain. Regional differences in mRNA levels were also investigated by in situ hybridization and drug-induced changes were noted particularly in specific regions of the rat brain stem. The riboprobe used in the in situ hybridization study recognized a 4.0 kilobase neuronal calmodulin mRNA species (NGB1), which was derived from the rat CaM1 gene. A calmodulin radio-immunoassay was utilized to demonstrate a drug-induced increased in calmodulin protein levels in a region which included the brain stem.

Developmental expression of neuronal calmodulin mRNA species in the rat brain analyzed by in situ hybridization

The temporal and spatial distribution of calmodulin mRNAs which are preferentially expressed in neurons was determined during postnatal development of rat central nervous system. Expression of these mRNAs was strongly detected in the developing neocortex, hippocampus, and cerebellum. Differences in the pattern of expression of a 1.8 and 4.0 kb neuronal calmodulin mRNA species were identified in the developing cerebellum. Expression of the smaller mRNA appeared to correlate with proliferating and developing cerebellar granule neurons while the larger mRNA was present in the mature granule neuron population. A transient elevation in the neuronal calmodulin mRNA species was observed in the superior and inferior colliculus and in the thalamus at postnatal days 5 and 10.

Molecular cloning of a novel mRNA using an antibody directed against synaptic glycoproteins

It has been suggested by a number of investigators that glycoproteins may play a role in the development and/or maintenance of synapses in the mammalian CNS. For many synaptic glycoproteins, however, little precise structural or functional information is available. In an effort to isolate probes specific to individual glycoproteins, we have screened a rat brain cDNA expression library with a mixed polyclonal antibody directed against concanavalin A-binding synaptic junctional glycoproteins. Using this approach, we have previously reported the cloning of SC1, a putative extracellular matrix glycoprotein found in adult brain (Johnston et al., Neuron 2:165-176, 1990). We now report the cloning and characterization of a second novel cDNA, which has been designated SC2. Northern blots show that this cDNA recognizes a 1.2-kb mRNA that is present throughout postnatal development in the rat. It is expressed at high levels in brain and is also found at lower levels in several other tissues. In situ hybridization suggests that the SC2 mRNA is strongly expressed by many types of neurons. Sequence data reveals a single open reading frame in the cDNA, encoding a putative hydrophobic protein with a calculated molecular weight of 36.1 kDa. Sequence analysis reveals some similarity between SC2 and 5 alpha-reductase, a microsomal membrane protein important in testosterone metabolism.

Calmodulin transcription is limited to the nervous system during Drosophila embryogenesis

We have examined the RNA expression pattern for the Drosophila calmodulin gene during embryogenesis by in situ hybridization to transcripts in whole embryos. Our results indicate that maternally derived calmodulin mRNA is homogeneously distributed throughout the early embryo, but that these maternal transcripts are lost by maximal germ band extension. Zygotic transcription of the gene in mid- to late-stage embryos is restricted to neural cell precursors and their progeny in both the central and peripheral nervous systems. Thus, activation of calmodulin transcription during embryonic development appears to mark a commitment to a neural fate. Northern blot analysis revealed that the two transcripts from the calmodulin gene are differentially expressed during embryogenesis. Comparison of Northern blot and in situ hybridization data indicates that the longer calmodulin mRNA is a nervous tissue-specific transcript. This suggests that neural-specific regulation of polyadenylation site usage occurs. We have also examined calmodulin expression in embryos homozygous for mutations in four loci which are known to affect nervous system development: numb, the achaete-scute complex, daughterless, and mastermind. The calmodulin transcription pattern is altered in embryos mutant for each of these loci, suggesting that regulation by these genes, either directly or indirectly, is taking place.

Molecular cloning of calmodulin mRNA species which are preferentially expressed in neurons in the rat brain

A cDNA clone designated NGB, which was isolated from a rat brain expression library, detected two mRNA species of 1.8 and 4.0 kb which are highly enriched in brain tissue. cDNAs NGB1 and NGB2 corresponding to these two mRNAs have been isolated and characterized. Sequence data showed that both mRNA species contain the same open reading frames but differ in their 3' untranslated regions. The open reading frame encodes a calmodulin protein of 148 amino acids. Both mRNA species are derived from the rat CaMI gene by utilization of different polyadenylation addition sites. Analysis of the 3' untranslated sequence which is unique to the larger mRNA species revealed a putative AU-rich 'destabilizer' sequence which is thought to be involved in mechanisms of selective mRNA breakdown. In situ hybridization studies revealed that the two calmodulin mRNAs are expressed strongly in neuronal cells in the adult rat brain. Levels of the two mRNA species increased during early postnatal development.