Parvalbumin is a mobile presynaptic Ca2+ buffer in the calyx of Held that accelerates the decay of Ca2+ and short-term facilitation

Presynaptic Ca2+ signaling plays a crucial role in short-term plasticity of synaptic transmission. Here, we studied the role of mobile endogenous presynaptic Ca2+ buffer(s) in modulating paired-pulse facilitation at a large excitatory nerve terminal in the auditory brainstem, the calyx of Held. To do so, we assessed the effect of presynaptic whole-cell recording, which should lead to the diffusional loss of endogenous mobile Ca2+ buffers, on paired-pulse facilitation and on intracellular Ca2+ concentration ([Ca2+]i) transients evoked by action potentials. In unperturbed calyces briefly preloaded with the Ca2+ indicator fura-6F, the [Ca2+]i transient decayed surprisingly fast (tau(fast), approximately 30 ms). Presynaptic whole-cell recordings made without additional Ca2+ buffers slowed the decay kinetics of [Ca2+]i and paired-pulse facilitation (twofold to threefold), but the amplitude of the [Ca2+]i transient was changed only marginally. The fast [Ca2+]i decay was restored by adding the slow Ca2+ buffer EGTA (50-100 microM) or parvalbumin (100 microM), a Ca2+-binding protein with slow Ca2+-binding kinetics, to the presynaptic pipette solution. In contrast, the fast Ca2+ buffer fura-2 strongly reduced the amplitude of the [Ca2+]i transient and slowed its decay, suggesting that the mobile endogenous buffer in calyces of Held has slow, rather than fast, binding kinetics. In parvalbumin knock-out mice, the decay of [Ca2+]i and facilitation was slowed approximately twofold compared with wild-type mice, similar to what is observed during whole-cell recordings in rat calyces of Held. Thus, in young calyces of Held, a mobile Ca2+ buffer with slow binding kinetics, primarily represented by parvalbumin, accelerates the decay of spatially averaged [Ca2+]i and paired-pulse facilitation.

Networks of parvalbumin-positive interneurons in the basolateral amygdala

The amygdala is a temporal lobe structure that is required for processing emotional information. Polymodal sensory information enters the amygdala at the level of the basolateral amygdala (BLA) and undergoes local processing, after which the behavioral and autonomic responses that accompany emotions are initiated. Two main neuron types are present in the BLA, pyramidal-like principal neurons that use glutamate as their transmitter, and local circuit interneurons that use GABA as their transmitter. Although the properties of principal neurons are known in some detail, very little is known about the properties of BLA interneurons or the local circuits in which they are involved. Using mice in which EGFP (enhanced green fluorescent protein) is expressed under the control of the parvalbumin promoter, we characterized the properties of parvalbumin-positive interneurons in the BLA. By making recordings from interneuron-interneuron and interneuron-principal neuron pairs, we analyzed the intrinsic circuitry of the BLA. We show that parvalbumin-positive interneurons can be divided into four subtypes as defined by their firing properties. Interneurons are electrically coupled in subtype-specific networks and exhibit subtype-specific heterogeneities in their synaptic dynamics and patterns of connectivity. We propose that these properties allow networks of parvalbumin-expressing neurons to perform an array of information-processing tasks within the BLA.

Differences in locomotor behavior revealed in mice deficient for the calcium-binding proteins parvalbumin, calbindin D-28k or both

We investigated the role of the two calcium-binding proteins parvalbumin (PV) and calbindin D-28k (CB) in the locomotor activity and motor coordination using null-mutant mice for PV (PV-/-), CB (CB-/-) or both proteins (PV-/-CB-/-). These proteins are expressed in distinct, mainly non-overlapping populations of neurons of the central and peripheral nervous system and PV additionally in fast-twitch muscles. In a test measuring repeated locomotor activity during 18-20 days, the analysis revealed a slightly increased activity in mice lacking either protein, while the lack of both decreased the number of beams crossed during active periods. An increase in the characteristic speed during the first 8 days could be attributed to PV-deficiency, while the elimination of CB in CB-/- and double-KO mice decreased the percentage of fast movements at all time points. In the latter, additionally a reduction of the fastest speed was observed. The alterations in locomotor activity (fast movements, fastest speed) strongly correlate with the impairment in locomotor coordination in mice deficient for CB evidenced in the runway assay and the rotarod assay. The graded locomotor phenotype (CB>PV) is qualitatively correlated with alterations in Purkinje cell firing reported previously in these mice. The presence or absence of either protein did not affect the spontaneous locomotor activity when animals were placed in a novel environment and tested only once for 30 min. In summary, the lack of these calcium-binding proteins yields characteristic, yet distinct phenotypes with respect to locomotor activity and coordination.

Modifications of the retina neuronal populations of the heterozygous mutant small eye mouse, the Sey(Dey)

We analyzed the modifications of the retinal neurons in a heterozygous mutant small eye mouse, the Sey(Dey). This mouse presents a mutation in chromosome 2 which affects the gene Pax6 and other nearby genes, such as the Wt1 gene and the gene of the Reticulocalbin. The eyes of these animals do not have lenses and their retinas present important morphological alterations: in the anterior portion they are joined to the cornea, they are found detached from the pigment epithelium, they present folds that form rosettes in some zones and alteration of the lamination can be observed. The partial loss of the genes affected does not prevent the formation of the different layers of the retina, but does affect its thickness, principally of the plexiform layers; moreover, the internal limiting membrane is found disorganized. All the neuronal populations are present in the retina of these animals and express the same neurochemical markers as the control animals, but the number of Pax6(+) cells is notably reduced. In these retinas a marked disorganization of the distribution of the dendrites and axons is observed and a notable reduction in the axons of ganglion cells. These results suggest that, although it does not appear determinant in the differentiation of the distinct neuronal types of the retina, the partial lack of genes of the heterozygotes +/Sey(Dey) provokes important morphological and neurochemical modifications in the cytoarchitecture of the retina.

Potential influence of Asp in the Ca2+ coordination position 5 of parvalbumin on the calcium-binding affinity: A computational study

Parvalbumins (PV) are calcium-binding proteins, all sharing the common helix-loop-helix (EF-hand) motif. This motif contains a central twelve-residue Ca(2+)-binding loop with the flanking helices positioned roughly perpendicular to each other. The precise role of these coordination residues has been the subject of intense studies. In this work, we focus on the coordination position 5 in the CD Ca(2+)-binding site of silver hake parvalbumin isoform B (SHPV-B). The most common residue at site 5 of calcium-binding loop in canonical EF-hands is Asp [B.J. Marsden, G.S. Shaw, B.D. Sykes, Biochem. Cell Biol. 68 (1990) 587-601], but in the CD site of PV, this position is almost always serine (Ser). The substitution of Ser with Asp will add the 5th carboxylate residue in the CD coordination sphere. However, as predicted by the acid pair hypothesis, the Ca(2+)-binding affinity would be maximized in an EF-hand motif that has four carboxylate ligands paired along the +/-x, and +/-z-axes [R.E. Reid, R.S. Hodges, J. Theor. Biol. 84 (1980) 401-444]. Molecular dynamics simulations and free energy calculations were employed to investigate the influence of Ser to Asp mutation at position 5 on calcium-binding affinity. We found that the Asp variant exhibited remarkable stability during the entire molecular dynamics simulation, with not only the retention of the Ca(2+)-binding site, but also increased compactness in the coordination sphere. The S55D fragment also accommodated Ca(2+) well. We conclude that the reason why Asp which is the most common residue at site 5 of calcium-binding loop in canonical EF-hands has never been identified at this position experimentally for PVs might be related to its physiological functions.

Diagnostic value of cytokeratin 7 and parvalbumin in differentiating chromophobe renal cell carcinoma from renal oncocytoma

OBJECTIVE

To investigate the diagnostic value of cytokeratin 7 (CK7) and parvalbumin at mRNA and protein levels.

STUDY DESIGN

CK7 and parvalbumin mRNA expression levels in 23 oncocytomas and 32 chromophobe renal cell carcinomas (RCCs) were examined using gene expression microarrays. Immunohistochemistry was performed using monoclonal antibodies specific for CK7 or parvalbumin in 41 chromophobe RCCs and 55 oncocytomas.

RESULTS

CK7 mRNA was overexpressed in 18 of 32 chromophobe RCCs but only 3 of 23 oncocytomas. Parvalbumin mRNA was overexpressed in 15 of 32 chromophobe RCCs and only 4 of 23 oncocytomas. In contrast, CK7 mRNA underexpression was noted in 13 of 23 oncocytomas and only 6 of 32 chromophobe RCCs, while parvalbumin underexpression was seen in 14 of 23 oncocytomas but only 6 of 32 chromophobe RCCs. By immunohistochemistry, 27 of 41 (66%) chromophobe RCCs expressed CK7 diffusely compared to only 3 of 55 (5%) oncocytomas. Diffuse parvalbumin expression was seen in all 41 of 41 (100%) chromophobe RCCs and only in 26 of 55 (47%) oncocytomas.

CONCLUSION

Both mRNA and protein expression levels of CK7 appear significantly higher in chromophobe RCC compared to oncocytoma (p < 0.001). Parvalbumin expression is less specific but often displays a patchy pattern in oncocytomas. Our study provides further evidence that CK7 and parvalbumin immunostains may be useful in differentiating oncocytoma from chromophobe RCC in problematic cases. Negative or patchy staining (< 50% cells) for CK7 and/or parvalbumin strongly favors the diagnosis of oncocytoma.

Characterization of two parvalbumin genes and their association with growth traits in Asian seabass (Lates calcarifer)

Parvalbumins are extremely abundant in fish muscle and play an important role in muscle relaxation. In this study, two parvalbumin genes (PVALB1 and PVALB2) were cloned from Asian seabass (Lates calcarifer). The cDNAs for PVALB1 and PVALB2 were 840 and 667 bp respectively. Both genes consisted of five exons and four introns, encoded 109 amino acids, and were of beta lineage. Using real-time polymerase chain reaction, expression of PVALB1 was detected in all 10 tissues tested, with expression in brain, kidney, muscle and small intestine being 15- to 322-fold higher than in the other tissues. Expression of PVALB2 was detected only in muscle, brain and intestine, and was up to 10-fold lower than PVALB1 expression. A (CT)(17) microsatellite in the 3'-untranslated region of PVALB1 and three single nucleotide polymorphisms (SNPs) in the third intron of PVALB2 were identified. The microsatellite in PVALB1 was significantly associated with body weight and body length at 90 days post-hatch (P < 0.01), whereas the SNPs in PVALVB2 were not associated with these traits.

Endogenous ciliary neurotrophic factor protects GABAergic, but not cholinergic, septohippocampal neurons following fimbria-fornix transection

Application of neurotrophic proteins including ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF), members of the family of gp130-associated cytokines, can rescue CNS neurons from injury-induced degeneration. However, it is not clear so far if these effects reflect a physiological function of the endogenous cytokines. Using fimbria-fornix transection as a model, we examined whether responses of GABAergic and cholinergic septohippocampal neurons to axotomy are altered in mice lacking CNTF. In addition, we studied the cellular expression of CNTF, LIF and related cytokine receptor components in the septal complex following lesion. Degeneration of septohippocampal GABAergic neurons in the medial septum as indicated by the loss of parvalbumin-immunoreactive neurons was accelerated and permanently enhanced in CNTF(-/-) mice as compared to wild-type animals. Unexpectedly, the number of axotomized cholinergic MS neurons was significantly higher in CNTF-deficient mice during the first 2 weeks postlesion. Both in wild-type and in CNTF(-/-) mutants, expression of mRNA for the CNTF-specific alpha-subunit of the cytokine receptor complex was specifically upregulated in axotomized GABAergic septal neurons, whereas enhanced expression of the LIF-binding beta-subunit was specifically observed in axotomized cholinergic neurons. Following lesion, CNTF expression in wild-type mice was induced in activated astrocytes surrounding the axotomized neurons and at the lesion site. Expression of LIF mRNA was localized in the GABAergic and cholinergic septohippocampal neurons. These results strongly indicate that endogenous CNTF, supplied by reactive glia cells, acts as a neuroprotective factor for axotomized CNS neurons. In the septum, endogenous CNTF specifically supports lesioned GABAergic projection neurons, whereas LIF may play a similar role for the cholinergic counterparts.

Complementary roles of cholecystokinin- and parvalbumin-expressing GABAergic neurons in hippocampal network oscillations

In the hippocampal CA1 area, a relatively homogenous population of pyramidal cells is accompanied by a diversity of GABAergic interneurons. Previously, we found that parvalbumin-expressing basket, axo-axonic, bistratified, and oriens-lacunosum moleculare cells, innervating different domains of pyramidal cells, have distinct firing patterns during network oscillations in vivo. A second family of interneurons, expressing cholecystokinin but not parvalbumin, is known to target the same domains of pyramidal cells as do the parvalbumin cells. To test the temporal activity of these independent and parallel GABAergic inputs, we recorded the precise spike timing of identified cholecystokinin interneurons during hippocampal network oscillations in anesthetized rats and determined their molecular expression profiles and synaptic targets. The cells were cannabinoid receptor type 1 immunopositive. Contrary to the stereotyped firing of parvalbumin interneurons, cholecystokinin-expressing basket and dendrite-innervating cells discharge, on average, with 1.7 +/- 2.0 Hz during high-frequency ripple oscillations in an episode-dependent manner. During theta oscillations, cholecystokinin-expressing interneurons fire with 8.8 +/- 3.3 Hz at a characteristic time on the ascending phase of theta waves (155 +/- 81 degrees), when place cells start firing in freely moving animals. The firing patterns of some interneurons recorded in drug-free behaving rats were similar to cholecystokinin cells in anesthetized animals. Our results demonstrate that cholecystokinin- and parvalbumin-expressing interneurons make different contributions to network oscillations and play distinct roles in different brain states. We suggest that the specific spike timing of cholecystokinin interneurons and their sensitivity to endocannabinoids might contribute to differentiate subgroups of pyramidal cells forming neuronal assemblies, whereas parvalbumin interneurons contribute to synchronizing the entire network.

Correlation between axonal morphologies and synaptic input kinetics of interneurons from mouse visual cortex

Neocortical interneurons display great morphological and physiological variability and are ideally positioned to control circuit dynamics, although their exact role is still poorly understood. To better understand this diversity, we have performed a detailed anatomical and physiological characterization of 3 subtypes of visual cortex interneurons, isolated from transgenic mice which express green fluorescent protein in somatostatin, parvalbumin, and neuropeptide Y positive neurons. We find that these 3 groups of interneurons have systematic differences in dendritic and axonal morphologies and also characteristically differ in the frequencies, amplitude, and kinetics of the spontaneous excitatory and inhibitory synaptic currents they receive. Moreover, we detect a correlation between the kinetics of their synaptic inputs and quantitative aspects of their axonal arborizations. This suggests that different interneuron types could channel different temporal patterns of activity. Our results also confirm the importance of the axonal morphology to classify interneurons.

Adenosine A2A receptors are expressed by GABAergic neurons of medulla oblongata in developing rat

During early development, adenosine contributes to the occurrence of respiratory depression and recurrent apneas. Recent physiological studies indicate that GABAergic mechanisms may be involved in this inhibitory action of adenosine, via their A(2A) receptors. In the present study, in situ hybridization with ribonucleotide probes for A(2A) receptor (A(2A)R) mRNA was combined with the immunolabeling technique for parvalbumin and transneuronal retrograde tracing method using green fluorescent protein expressing pseudorabies virus (GFP-PRV) to (1) characterize age-dependent changes in the expression of adenosine A(2A)Rs mRNA in brain stem regions where GABAergic neurons are located; (2) determine whether GABA-containing neurons express A(2A)R mRNA traits, and (3) identify whether bulbospinal GABAergic neurons projecting to phrenic nuclei contain A(2A)R mRNA. Results revealed expression of A(2A) receptors in regions of medulla oblongata containing GABAergic neurons, namely in the ventral aspect of the medulla, within the Bötzinger region and caudal to it, the gigantocellular reticular nucleus, midline neurons and the caudal ventrolateral medulla oblongata. Furthermore, a subpopulation of identified GABAergic neurons, projecting to the phrenic motor nuclei, possess A(2A)R mRNA. It is concluded that adenosine A(2A)Rs expressed by GABAergic neurons are likely to play a role in mediating adenosine-induced respiratory depression.

Functional and molecular development of striatal fast-spiking GABAergic interneurons and their cortical inputs

Despite their small number, fast-spiking (FS) GABAergic interneurons play a critical role in controlling striatal output by mediating cortical feed-forward inhibition of striatal medium-sized spiny (MS) projection neurons. We have examined the functional development of FS interneurons and their cortical inputs, and the expression of three of their molecular markers, in the dorsolateral rat striatum between postnatal days (P)12--14 and 19--23, the time of major corticostriatal synaptogenesis. FS interneurons were visualized with infrared differential interference contrast (IR-DIC) optics and examined with current-clamp recording in the presence of the GABA(A) receptor antagonist bicuculline methiodide. FS interneurons displayed action potentials at relatively high frequencies in response to depolarizing current pulses by P12, but developmental changes occurred in action potential and afterhyperpolarization duration and amplitude and input resistance between P12--14 and P19--23, as well as an increase in maximum firing frequency in response to depolarizing current pulses. Maturation in electrophysiological properties was paralleled by increases in Kv 3.1 and parvalbumin mRNA expression, while GAD-67 mRNA levels remained constant. Furthermore, FS interneurons in the younger age group responded to stimulation of cortical afferents with excitatory postsynaptic potentials (EPSPs) of higher amplitudes and received significantly more spontaneous depolarizing inputs than did MS neurons. Thus, FS interneurons are under frequent and continuous cortical influence by the end of the 2nd postnatal week, a time when corticostriatal synapses are sparse, suggesting that they may provide a major inhibitory influence in the striatum during the period of intense developmental maturation.

Parvalbumin isoforms in zebrafish

By using an analysis of existing genomic information it is concluded that in zebrafish nine genes encode parvalbumin (PV). These genes possess introns that differ in size and show nucleotide variability but they contain the same number of exons, and for each corresponding exon, the number of nucleotides therein are identical in all the paralogs. This rule also applies to the multiple PV genes of other species e.g. mammals. Each of these genes displays, however, characteristic 5' and 3' UTRs which appear highly conserved between closely related species (so that orthologs among these species can be readily identified) but which show larger numbers of mutations between species that are more distant in evolution. A tree is presented which suggests that the traditional classification of PVs as alpha or beta (based mainly on charge of the protein molecule) is not sustainable. Numbers 1-9 are assigned to the various isoforms to facilitate their identification in future studies. A bifurcation of isoforms into 1 and 4; 2 and 3; 6 and 7; 8 and 9 appears to have occurred simultaneously in more recent time, i.e. perhaps approximately 60 mys ago when primates and rodents branched.

Deprenyl enhances the striatal neuronal damage produced by quinolinic acid

We have tested the effect of deprenyl on the neurotoxicity induced by the injection of quinolinic acid within the striatum. Deprenyl was unable to prevent these quinolinic acid-induced damages, but enhanced the loss of several gamma-aminobutyric acid (GABA) positive subpopulations, the loss of the astroglial population and the activation of microglia produced by quinolinic acid. These effects are produced by deprenyl potentiation of dopamine actions since dopamine depletion produced by previous injection of the dopaminergic toxin 6-hydroxydopamine within the medial forebrain bundle overcomes deprenyl effects and the involvement of dopamine in the quinolinic acid-induced toxicity in striatum. In these conditions, quinolinic acid toxic action in striatum is significantly lower and similar in the animals treated with or without deprenyl. All these data justify why deprenyl worsen some pathological signals of disorders involving excitotoxicity. This also may be involved in other secondary effects described for deprenyl.

Sonic hedgehog maintains the identity of cortical interneuron progenitors in the ventral telencephalon

Fate determination in the mammalian forebrain, where mature phenotypes are often not achieved until postnatal stages of development, has been an elusive topic of study despite its relevance to neuropsychiatric disease. In the ventral telencephalon, major subgroups of cerebral cortical interneurons originate in the medial ganglionic eminence (MGE), where the signaling molecule sonic hedgehog (Shh) continues to be expressed during the period of neuronogenesis. To examine whether Shh regulates cortical interneuron specification, we studied mice harboring conditional mutations in Shh within the neural tube. At embryonic day 12.5, NestinCre:ShhFl/Flmutants have a relatively normal index of S-phase cells in the MGE, but many of these cells do not co-express the interneuron fate-determining gene Nkx2.1. This effect is reproduced by inhibiting Shh signaling in slice cultures, and the effect can be rescued in NestinCre:ShhFl/Fl slices by the addition of exogenous Shh. By culturing MGE progenitors on a cortical feeder layer, cell fate analyses suggest that Shh signaling maintains Nkx2.1 expression and cortical interneuron fate determination by MGE progenitors. These results are corroborated by the examination of NestinCre:ShhFl/Fl cortex at postnatal day 12, in which there is a dramatic reduction in cell profiles that express somatostatin or parvalbumin. By contrast, analyses of Dlx5/6Cre:SmoothenedFl/Flmutant mice suggest that cell-autonomous hedgehog signaling is not crucial to the migration or differentiation of most cortical interneurons. These results combine in vitro and ex vivo analyses to link embryonic abnormalities in Shh signaling to postnatal alterations in cortical interneuron composition.

Postnatal development of synaptopodin expression in the rodent hippocampus

Synaptopodin is an actin-binding protein of renal podocytes and dendritic spines. We have recently shown that synaptopodin is localized to the spine apparatus, a characteristic organelle of dendritic spines on forebrain neurons. Synaptopodin-deficient mice do not form spine apparatuses, indicating a role of synaptopodin in the formation of this organelle. Here we studied the development of synaptopodin expression in the postnatal rat hippocampus. At birth, synaptopodin mRNA is mainly expressed in CA3 pyramidal neurons. At postnatal day (P) 6, synaptopodin mRNA expression is still strongest in CA3 but is now also found in CA1 pyramidal neurons and granule cells of the suprapyramidal blade of the dentate gyrus. At P9, an almost adult pattern is seen with synaptopodin mRNA expressed by virtually all principal neurons. While synaptopodin mRNA was restricted to cell somata, immunostaining for synaptopodin protein labeled dendritic layers. At birth, no immunoreactivity was visible, while at P5 a weak staining mainly in stratum oriens was observed. At P9, immunolabeling was still strongest in stratum oriens followed by the molecular layer of the dentate gyrus. The adult pattern with strong labeling of all dendritic layers was reached by P12. Together these findings show that synaptopodin expression follows the well-known sequence of hippocampal principal neuron development. Unexpectedly, we also observed synaptopodin mRNA expression in a small population of interneurons as revealed by double labeling with interneuron markers. However, no immunolabeling for synaptopodin was observed in identified interneurons, confirming that the protein is mainly present in spine-bearing principal cells.

Brn-3a is required for the generation of proprioceptors in the mesencephalic trigeminal tract nucleus

The distribution of motor and proprioceptive neurons was investigated in the trigeminal nervous system of wild-type and Brn-3a knockout mice at embryonic day 18.5 and postnatal day 0. We found that the trigeminal motor nucleus (Mo5) contained abundant motoneurons in wild-type (mean number +/- SD per section = 128 +/- 22, range = 93-167) and knockout (mean number +/- SD per section = 121 +/- 23, range = 75-158) mice and that the cell size of Mo5 neurons was similar between these mice (wild-type, mean +/- SD = 165 +/- 59 microm2, range = 65-326 microm2; knockout, mean +/- SD = 167 +/- 59 microm2, range = 71-327 microm2). Mo5 neurons were immunoreactive for calcitonin gene-related peptide and such immunoreactive neurons were abundant in both wild-type and mutant mice. In the mesencephalic tract nucleus (Mes5) of wild-type mice, many proprioceptors (mean number +/- SD per section = 56 +/- 19, range = 27-85) that contained parvalbumin immunoreactivity were also observed. In knockout mice, however, Mes5 neurons could not be detected. The area of brainstems which normally contained the Mes5 was devoid of parvalbumin-immunoreactive proprioceptors. The present study suggests that Brn-3a is required for the development of proprioceptors but not motoneurons in the trigeminal nervous system.

Mimotopes identify conformational epitopes on parvalbumin, the major fish allergen

Parvalbumin, the major fish allergen, is recognized by allergen-specific IgE of more than 90% of all fish-allergic patients. A detailed knowledge of allergenic structures is crucial for developing a vaccine inducing blocking antibodies specifically directed towards the IgE binding epitopes. In the present study we aimed to use the phage display technique to generate mimotopes, which mimic epitopes on parvalbumin. Parvalbumin-specific IgE was purified from sera of fish-allergic patients and used for screening of a constrained decamer phage library. After four rounds of biopanning using parvalbumin-specific IgE, five phage clones were selected which were specifically recognized by parvalbumin-specific IgE as well as IgG. DNA sequencing and peptide alignment revealed a high degree of sequence similarities between the mimotopes. Interestingly, on the surface of natural parvalbumin three regions could be defined by computational mimotope matching. In accordance, previously defined allergenic peptides of cod parvalbumin highlighted areas in close proximity or overlapping with the mimotope matching sites. From the presented data we conclude that our approach identified conformational epitopes of parvalbumin relevant for IgE and IgG binding. We suggest that these mimotopes are suitable candidates for an epitope-specific immunotherapy of fish-allergic patients.

In vivo gene transfer of parvalbumin improves diastolic function in aged rat hearts

OBJECTIVE

Diastolic dysfunction is a characteristic finding of the aged mammalian heart. Parvalbumin acts as a Ca2+ sink and enhances relaxation in skeletal muscle, and overexpression of parvalbumin in myocardium increased cardiac relaxation in vitro as well as in vivo. Therefore, the objective of this study is to test the hypothesis that in vivo gene transfer of parvalbumin will improve diastolic dysfunction in aged rat heart.

METHODS

We used adenovirus to transfer parvalbumin into two different rat models of aging: the Fischer 344 (F344) and the Fischer 344 x Brown Norway F1 hybrid (F344 x BN). Cardiac function was measured and compared after gene transfer.

RESULTS

In vivo overexpression of parvalbumin in both rat aging models had no effect on systolic parameters but reduced left ventricular diastolic pressure and the time course of pressure decline. Overexpression of parvalbumin also improved the force frequency relationship in senescent rats.

CONCLUSION

In vivo overexpression of parvalbumin improves diastolic dysfunction in two rat models of senescence, and this effect is independent of the rat strain investigated. The results show promise that gene therapy of parvalbumin may address the impaired Ca2+ homeostasis and diastolic dysfunction without an increase in energy expenditure.

Crystal Structure of the D94S/G98E Variant of Rat α-Parvalbumin. An Explanation for the Reduced Divalent Ion Affinity

Simultaneous replacement of Asp-94 with serine and Gly-98 with glutamate in rat alpha-parvalbumin creates a CD-site ligand array in the context of the EF-site binding loop. Previous work has shown that, relative to the wild-type CD site, this engineered site has markedly reduced Ca(2+) affinity. Seeking an explanation for this phenomenon, we have obtained the crystal structure of the alpha D94S/G98E variant. The Ca(2+) coordination within the engineered EF site of the 94/98E variant is nearly identical to that within the CD site, suggesting that the attenuated affinity of the EF site in 94/98E is not a consequence of suboptimal coordination geometry. We have also examined the divalent ion binding properties of the alpha 94/98E variant in both Na(+)- and K(+)-containing buffers. Although the Ca(2+) and Mg(2+) affinities are higher in K(+) solution, the increases are comparable to those observed for wild-type alpha. Consistent with that finding, the apparent Na(+) stoichiometry, estimated from stability studies conducted as a function of Na(+) concentration, is 1.0 +/- 0.1, identical to that of wild-type alpha. Thus, the reduced affinity for divalent ions is evidently not the result of heightened monovalent ion competition. The thermodynamic analysis indicates that the less favorable Gibbs free energy of binding reflects a substantial enthalpic penalty. Significantly, the crystal structure reveals a steric clash between Phe-57 and the C(gamma) atom of Glu-98. The consequent displacement of Phe-57 also produces a close contact with Ser-55. Thus, steric interference may be the source of the enthalpic penalty.

Impairment in perceptual attentional set-shifting following PCP administration: a rodent model of set-shifting deficits in schizophrenia

RATIONALE

Impaired ability to shift perceptual attentional set forms a core feature of schizophrenic illness and is associated with prefrontal cortical dysfunction. A pharmacological model producing equivalent deficits in rodents may enable the development of novel therapeutic strategies for effective treatment of cognitive impairments in schizophrenia.

OBJECTIVE

This study was designed to investigate the effects of phencyclidine (PCP) administration on performance in a rodent attentional set-shifting task and the neural correlates of PCP-induced deficits in task performance.

METHODS

Twenty-four hours following acute administration of 2.58 mg/kg PCP or vehicle, rats were tested on a perceptual attentional set shifting task (Birrell and Brown in J Neurosci 20:4320-4324, 2000). Following completion of the task, in situ hybridisation was employed to detect concurrent regional alterations in zif-268 and parvalbumin mRNA expression.

RESULTS

PCP administration selectively decreased the ability of rats to shift attentional set between perceptual dimensions (extra-dimensional shift, EDS). This impairment was accompanied by, and correlated with, decreases in expression of zif-286 in the infralimbic cortex and of parvalbumin in the dorsal reticular nucleus of the thalamus.

CONCLUSION

Acute administration of PCP produces deficits in perceptual set shifting comparable to an aspect of executive dysfunction in schizophrenia. Moreover, this impairment is associated with altered medial prefrontal cortical and reticular thalamic activity. Therefore, this rodent paradigm may model the set-shifting deficits that form a core feature of schizophrenic pathology.

5-HT1A receptor mRNA and immunoreactivity in the rat medial septum/diagonal band of Broca—relationships to GABAergic and cholinergic neurons

Activation of 5-HT1A receptors results in a variety of physiological responses, depending on their localization on neurons with different phenotypes in the brain. This study investigated the localization of 5-HT1A receptor mRNA and 5-HT1A receptor immunoreactivity in cell bodies of the rat septal complex using in situ hybridization and immunohistochemistry. In adjacent sections of the medial septum/diagonal band of Broca (MSDB), the distribution of cell bodies expressing 5-HT1A receptor mRNA was closely related to cells labeled with oligonucleotide probes to GAD (glutamic acid decarboxylase), VAChT (vesicular acetylcholine transporter) or parvalbumin mRNA. Using antiserum to GAD and antibodies to GABA, 5-HT1A receptor immunoreactivity was demonstrated in a majority of GABAergic cells in the MSDB. 5-HT1A receptor-immunoreactive GABAergic cells in the MSDB were also demonstrated to contain the calcium-binding protein parvalbumin, a marker for septohippocampal projecting GABAergic neurons. In the lateral septum, 5-HT1A receptor immunoreactivity was colocalized with the calcium-binding protein calbindin D-28k, a marker for septal GABAergic somatospiny neurons. 5-HT1A receptor immunoreactivity was also detected in a subpopulation of VAChT-containing cholinergic neurons of the MSDB. In MSDB neurons, colocalization of 5-HT1A and 5-HT2A receptor immunoreactivities was demonstrated. These observations suggest that serotonin via 5-HT1A receptors may represent an important modulator of hippocampal transmission important for cognitive and emotional functions through actions on both GABAergic and cholinergic neurons of the rat septal complex. In addition, 5-HT may exert its effects in the MSDB via cells expressing both 5-HT1A and 5-HT2A receptors.

Ethanol withdrawal reduces cerebellar parvalbumin expression in a manner reversed by estrogens

Parvalbumin (PA) is a calcium-binding protein that has been implicated in neuroprotection. We examined whether the stimulus effect of ethanol withdrawal (EW) alters the expression of PA in a manner that is prevented by 17beta-estradiol (E2). Ovariectomized rats implanted with E2 (EW/E2) or oil (EW/Oil) pellets received chronic ethanol (7.5%, w/v, 5 weeks) or control dextrin diets (Dex/Oil). At 24h of EW, rats were tested for overt EW signs, and the cerebellum was prepared for immunoblotting and immunohistological assessment for PA. The EW/Oil group showed a higher EW sign score, a lower PA expression, and fewer PA-positive Purkinje neurons than the dextrin control group. In the EW/E2 group, EW sign scores, PA expression, and PA-positive Purkinje neurons were not significantly different from those in the control dextrin group. These data suggest that E2 treatment protects against the PA-suppression associated with EW toxicity.

Solution structure of human beta-parvalbumin and structural comparison with its paralog alpha-parvalbumin and with their rat orthologs

The aim of this research was to determine the structure of human beta-parvalbumin (109 amino acids) and to compare it with its paralog and ortholog proteins. The structure was determined in solution using multinuclear and multidimensional NMR methods and refined using substitution of the EF-hand Ca(2+) ion with a paramagnetic lanthanide. The resulting family of structures had a backbone rmsd of 0.50 A. Comparison with rat oncomodulin (X-ray, 1.3 A resolution) as well as with human (NMR, backbone rmsd of 0.49 A) and rat (X-ray, 2.0 A resolution) parvalbumins reveals small but reliable local differences, often but not always related to amino acid variability. The analysis of these structures has led us to propose an explanation for the different affinity for Ca(2+) between alpha- and beta-parvalbumins and between parvalbumins and calmodulins.

Characterization of parvalbumin, the major allergen in Alaska pollack, and comparison with codfish Allergen M

Increased fish consumption has led to frequent reporting of fish allergy and adverse reactions. Alaska pollack (Theragra chalcogramma) is a globally important commercial fish species, belonging to the Gadidae family. This family of fish also includes cod whose parvalbumin, Allergen M (Gad c 1), has been thoroughly studied and considered as a reference to sensitization in fish allergy. In the present study, parvalbumin from Alaska pollack, designated The c 1, was purified by use of anion exchange chromatography. To demonstrate the homogeneity of the purified protein, reverse phase high performance liquid chromatography was performed and showed two distinct fractions which had similar IgG and IgE binding capacities. Accordingly, cDNA cloning revealed two isotypic parvalbumin transcripts in pollack muscle. Recombinant parvalbumins of pollack exhibited low IgG and IgE binding capacities, in contrast to the native counterparts, which were almost as potent as cod Gad c 1. The allergenicity of The c 1 was assayed by ELISA inhibition, and compared to cod, the concentration required for obtaining 50% ELISA inhibition (C 50%) was only 18% higher for The c 1.