Isolation of a rat parvalbumin gene and full length cDNA

Repeated 4-aminopyridine seizures reduce parvalbumin content in the medial mammillary nucleus of the rat brain

Parvalbumin (Pv) containing fast spiking neurons play a crucial role in synchronizing the activity of excitatory neuronal circuits in the brain. Alterations of parvalbumin content in these neurons can affect their spike characteristics and, ultimately, may increase the susceptibility of neuronal circuits to epileptic seizures. In the present study, we examined whether repeated 4-aminopyridine (4-AP)-induced seizures modify the regional parvalbumin contents in the rat brain. 4-Aminopyridine was injected intraperitoneally in adult rats, controls received the solvent. Animals were sacrificed at 3 h after a single acute treatment, or following repeated, daily treatments of 12 days. In situ hybridization (ISH) indicated significantly decreased parvalbumin mRNA level in the medial mammillary nucleus (MM) at 12 days. Western blotting revealed 20.1% significant decrease of parvalbumin content in the medial mammillary area, while parvalbumin immunohistochemistry indicated no change of the number of immunoreactive cells in the medial mammillary nucleus. The results reveal the downregulation of the transcription of the parvalbumin gene and the decrease of parvalbumin synthesis in medial mammillary nucleus neurons in response to experimental seizures.

Crystal structure of rat alpha-parvalbumin at 1.05 Angstrom resolution

The crystal structure of rat alpha-parvalbumin has been determined at 1.05 Angstrom resolution, using synchrotron data collected at Advanced Photon Source beamline 19-ID. After refinement with SHELX, employing anisotropic displacement parameters and riding hydrogen atoms, R = 0.132 and R(free) = 0.162. The average coordinate estimated standard deviations are 0.021 Angstrom and 0.038 Angstrom for backbone atoms and side-chain atoms, respectively. Besides providing a more precise view of the alpha-isoform than previously available, these data permit comparison with the 0.91 Angstrom structure determined for pike beta-parvalbumin. Visualization of the anisotropic displacement parameters as thermal ellipsoids yields insight into the atomic motion within the Ca(2+)-binding sites. The asymmetric unit includes three parvalbumin (PV) molecules. Interestingly, the EF site in one displays uncharacteristic flexibility. The ellipsoids for Asp-92 are particularly large and non-spherical, and the shape of the Ca(2+) ellipsoid implies significant vibrational motion perpendicular to the plane defined by the four y and z ligands. The relative dearth of crystal-packing interactions in this site suggests that the heightened flexibility may be the result of diminished intermolecular contacts. The implication is that, by impeding conformational mobility, crystal-packing forces may cause serious overestimation of EF-hand rigidity. The high quality of the data permitted 11 residues to be modeled in alternative side-chain conformations, including the two core residues, Ile-97 and Leu-105. The discrete disorder observed for Ile-97 may have functional ramifications, providing a mechanism for communicating binding status between the CD and EF binding loops and between the PV metal ion-binding domain and the N-terminal AB region.

Estimation of parvalbumin Ca(2+)- and Mg(2+)-binding constants by global least-squares analysis of isothermal titration calorimetry data

The use of competitive isothermal titration calorimetry (ITC) to measure high-affinity binding constants has been largely restricted to systems with a single binding site or multiple identical sites. This study demonstrates the extension of this approach to proteins with two nonequivalent EF-hand Ca(2+)-binding sites--rat beta parvalbumin and the S55D/E59D variant of rat alpha parvalbumin. The method involves simultaneous (global) least-squares analysis of titrations with Ca(2+), with Mg(2+), with Ca(2+) in the presence of Mg(2+), and with Ca(2+) or Mg(2+) in the presence of a competitive chelator (EDTA or EGTA). The Ca(2+) and Mg(2+) binding constants obtained for rat beta agree well with estimates obtained by flow dialysis. Although the Ca(2+) affinity of alpha S55D/E59D is too high to measure by flow dialysis, it was amenable to analysis using the ITC-based approach. The combined S55D and E59D mutations increase the Ca(2+) and Mg(2+) affinities of the mutated binding site by factors of 14 and 26, respectively. This behavior is consistent with that seen previously for the rat beta S55D variant.

"Dormant basket cell" hypothesis revisited: relative vulnerabilities of dentate gyrus mossy cells and inhibitory interneurons after hippocampal status epilepticus in the rat

The "dormant basket cell" hypothesis suggests that postinjury hippocampal network hyperexcitability results from the loss of vulnerable neurons that normally excite insult-resistant inhibitory basket cells. We have reexamined the experimental basis of this hypothesis in light of reports that excitatory hilar mossy cells are not consistently vulnerable and inhibitory basket cells are not consistently seizure resistant. Prolonged afferent stimulation that reliably evoked granule cell discharges always produced extensive hilar neuron degeneration and immediate granule cell disinhibition. Conversely, kainic acid-induced status epilepticus in chronically implanted animals produced similarly extensive hilar cell loss and immediate granule cell disinhibition, but only when granule cells discharged continuously during status epilepticus. In both preparations, electron microscopy revealed degeneration of presynaptic terminals forming asymmetrical synapses in the mossy cell target zone, including some terminating on gamma-aminobutyric acid-immunoreactive elements, but no evidence of axosomatic or axoaxonic degeneration in the adjacent granule cell layer. Although parvalbumin immunocytochemistry and in situ hybridization revealed decreased staining, this apparently was due to altered parvalbumin expression rather than basket cell death, because substance P receptor-positive interneurons, some of which contained residual parvalbumin immunoreactivity, survived. These results confirm the inherent vulnerability of dendritically projecting hilar mossy cells and interneurons and the relative resistance of dentate inhibitory basket and chandelier cells that target granule cell somata. The variability of hippocampal cell loss after status epilepticus suggests that altered hippocampal structure and function cannot be assumed to cause the spontaneous seizures that develop in these animals and highlights the importance of confirming hippocampal pathology and pathophysiology in vivo in each case.

Alterations in slow-twitch muscle phenotype in transgenic mice overexpressing the Ca2+ buffering protein parvalbumin

The purpose of this study was to determine whether induced expression of the Ca2+ buffering protein parvalbumin (PV) in slow-twitch fibres would lead to alterations in physiological, biochemical and molecular properties reflective of a fast fibre phenotype. Transgenic (TG) mice were generated that overexpressed PV in slow (type I) muscle fibres. In soleus muscle (SOL; 58 % type I fibres) total PV expression was 2- to 6-fold higher in TG compared to wild-type (WT) mice. Maximum twitch and tetanic tensions were similar in WT and TG but force at subtetanic frequencies (30 and 50 Hz) was reduced in TG SOL. Twitch time-to-peak tension and half-relaxation time were significantly decreased in TG SOL (time-to-peak tension: 39.3 +/- 2.6 vs. 55.1 +/- 4.7 ms; half-relaxation time: 42.1 +/- 3.5 vs. 68.1 +/- 9.6 ms, P < 0.05 for TG vs. WT, respectively; n = 8-10). There was a significant increase in expression of type IIa myosin heavy chain (MHC) and ryanodine receptor at the mRNA level in TG SOL but there were no differences in MHC expression at the protein level and thus no difference in fibre type. Whole muscle succinate dehydrogenase activity was reduced by 12 +/- 0.4 % in TG SOL and single fibre glycerol-3-phosphate dehydrogenase activity was decreased in a subset of type IIa fibres. These differences were associated with a 64 % reduction in calcineurin activity in TG SOL. These data show that overexpression of PV, resulting in decreased calcineurin activity, can alter the functional and metabolic profile of muscle and influence the expression of key marker genes in a predominantly slow-twitch muscle with minimal effects on the expression of muscle contractile proteins.

Molecular characterization of the murine SIGNR1 gene encoding a C-type lectin homologous to human DC-SIGN and DC-SIGNR

The C-type lectin human dendritic cell (DC)-specific intercellular adhesion molecule (ICAM)-3-grabbing non-integrin (DC-SIGN) plays important roles in pattern recognition by dendritic cells in the immune system. In addition to binding human immunodeficiency virus (HIV), this type II membrane protein binds with high affinity to the adhesion molecules ICAM-3 and -2 to promote important dendritic cell interactions with naive T cells and endothelial cells, respectively. DC-SIGNR, a human DC-SIGN homologue expressed on sinusoidal endothelial cells in liver and lymph node, also binds and transmits HIV virus. We describe the cloning and characterization of a family of murine complementary DNAs (cDNAs) called SIGNR1, expressed in skin and spleen, that encode C-type lectins highly related to human DC-SIGN and DC-SIGNR. We also report the genomic structure of the SIGNR1 gene and compare it to that of human DC-SIGN and DC-SIGNR. The different transcripts (alpha, beta, gamma, delta) are generated by differences in 5' untranslated sequences, alternative splicing and/or the use of different polyadenylation sites. The predicted open reading frames encoded by the cDNAs are most closely related to human DC-SIGN and DC-SIGNR in the cytoplasmic domain, the transmembrane region and the carbohydrate recognition domain. Moreover, the alternatively spliced transcripts encode proteins that lack the transmembrane region or have modified carbohydrate recognition domains. Northern hybridization experiments with several different SIGNR1 cDNA probes reveal transcripts of 1.3 and 2.1 kb that are expressed in a tissue-restricted fashion in murine skin, spleen and lung. In situ hybridization and immunocytochemistry experiments demonstrate that, like human DC-SIGN, the murine messenger RNAs are expressed in subsets of dendritic cells in the spleen and skin.

Protective effect of parvalbumin on excitotoxic motor neuron death

The mechanism responsible for the selective vulnerability of motor neurons in amyotrophic lateral sclerosis (ALS) is poorly understood. Several lines of evidence indicate that susceptibility of motor neurons to Ca(2+) overload induced by excitotoxic stimuli is involved. In this study, we investigated whether the high density of Ca(2+)-permeable AMPA receptors on motor neurons gives rise to higher Ca(2+) transients in motor neurons compared to dorsal horn neurons. Dorsal horn neurons were chosen as controls as these cells do not degenerate in ALS. In cultured spinal motor neurons, the rise of the cytosolic Ca(2+) concentration induced by kainic acid (KA) and mediated by the AMPA receptor was almost twice as high as in spinal neurons from the dorsal horn. Furthermore, we investigated whether increasing the motor neuron's cytosolic Ca(2+)-buffering capacity protects them from excitotoxic death. To obtain motor neurons with increased Ca(2+) buffering capacity, we generated transgenic mice overexpressing parvalbumin (PV). These mice have no apparent phenotype. PV overexpression was present in the central nervous system, kidney, thymus, and spleen. Motor neurons from these transgenic mice expressed PV in culture and were partially protected from KA-induced death as compared to those isolated from nontransgenic littermates. PV overexpression also attenuated KA-induced Ca(2+) transients, but not those induced by depolarization. We conclude that the high density of Ca(2+)-permeable AMPA receptors on the motor neuron's surface results in high Ca(2+) transients upon stimulation and that the low cytosolic Ca(2+)-buffering capacity of motor neurons may contribute to the selective vulnerability of these cells in ALS. Overexpression of a high-affinity Ca(2+) buffer such as PV protects the motor neuron from excitotoxicity and this protective effect depends upon the mode of Ca(2+) entry into the cell.

15N nuclear magnetic resonance relaxation studies on rat beta-parvalbumin and the pentacarboxylate variants, S55D and G98D

15N relaxation data for Ca(2+)-bound rat beta-parvalbumin (a.k.a. oncomodulin) were analyzed using the Lipari-Szabo formalism and compared with existing data for rat alpha-parvalbumin. Although the average S(2) values for the two proteins are very similar (0.85 for alpha, 0.84 for beta), residue-by-residue inspection reveals systematic differences. alpha tends to have the lower S(2) value in helical regions; beta tends to have the lower value in the loop regions. Rat beta was also examined in the Ca(2+)-free state. The 59 assigned residues displayed an average order parameter (0.90) significantly greater than the corresponding residues in the Ca(2+)-loaded form. The pentacarboxylate variants of rat beta-S55D and G98D-also were examined in the Ca(2+)-bound state. Although both mutations significantly heighten Ca(2+) affinity, they utilize distinct energetic strategies. S55D improves the Ca(2+)-binding enthalpy; G98D improves the binding entropy. They also show disparate peptide backbone dynamics. Whereas beta G98D displays an average order parameter (0.87) slightly greater than that of the wild-type protein, beta S55D displays an average order parameter (0.82) slightly lower than wild-type beta. Furthermore, whereas just two backbone N-H bonds in beta G98D show internal motion on the 20-200-psec timescale, fully 52 of the 93 residues analyzed in beta S55D show this behavior. These findings suggest that the increased electrostatic repulsion attendant to introduction of an additional carboxylate into the CD site ligand array impedes backbone vibrational motion throughout the molecule.

Control of IP(3)-mediated Ca2+ puffs in Xenopus laevis oocytes by the Ca2+-binding protein parvalbumin

1. Elementary events of Ca2+ release (Ca2+ puffs) can be elicited from discrete clusters of inositol 1,4,5 trisphosphate receptors (IP(3)Rs) at low concentrations of IP(3). Ca(2+) puffs have rarely been observed unless elicited by either hormone treatment or introduction of IP(3) into the cell. However, cells appear to have sufficient concentrations of IP(3) (0.1-3.0 microM) to induce Ca2+ release under resting conditions. 2. Here, we investigated Ca2+ puff activity in non-stimulated Xenopus oocytes using confocal microscopy. The fluorescent Ca2+ dye indicators Calcium Green 1 and Oregon Green 488 BAPTA-2 were injected into oocytes to monitor basal Ca2+ activity. 3. In this preparation, injection or overexpression of parvalbumin, an EF-hand Ca(2+)-binding protein (CaBP), induced Ca2+ puffs in resting Xenopus oocytes. This activity was inhibited by heparin, an IP(3)R channel blocker, and by mutation of the Ca(2+)-binding sites in parvalbumin. 4. Ca2+ puff activity was also evoked by injection of low concentrations of the Ca2+ chelator EGTA, but not by calbindin D(28k), another member of the EF-hand CaBP superfamily. 5. BAPTA and the Ca2+ indicator dye Oregon Green 488 BAPTA-1 evoked Ca2+ puff activity, while the dextran conjugate of Oregon Green 488 BAPTA-1 did not. These data indicate that a Ca(2+) buffer must be mobile in order to increase Ca2+ puff activity. 6. Together, the data indicate that some IP(3)Rs spontaneously release Ca2+ under resting concentrations of IP(3). These elementary Ca2+ events appear to be below the level of detection of current imaging techniques. We suggest that parvalbumin evokes Ca2+ puffs by coordinating the activity of elementary IP(3)R channel openings. 7. We conclude that Ca2+ release can be evoked not only by hormone-induced increases in IP(3), but also by expression of mobile cytosolic CaBPs under resting concentrations of IP(3).

Parvalbumin Expression Is Downregulated in Rat Fast-Twitch Skeletal Muscles during Aging

In this study, the protein expression profile of extensor digitorum longous (EDL) and Soleus (SOL) muscles, representing fast- and slow-twitch skeletal muscles, respectively, was established using high resolution two-dimensional electrophoresis (2-DE). One protein spot was found uniquely expressed in EDL muscle. N-terminal sequence analysis identified the protein as parvalbumin. Parvalbumin is a high affinity calcium binding protein that regulates muscle contraction and relaxation. Our experiments revealed that parvalbumin expression in EDL muscle was down-regulated during aging. In addition, high-intensity exercise could reverse this age-related change. Soleus muscles do not normally express parvalbumin, but high-intensity exercise could ectopically induce its expression in both young and old SOL muscles. We have also confirmed our 2-DE findings by immunohistochemistry on muscle sections. Our results suggest that high-intensity training could be used to improve muscle functions during aging because parvalbumin play an important role in regulating skeletal muscle contraction and relaxation.

Characterization of control and immobilized skeletal muscle: an overview from genetic engineering

To elucidate the molecular basis of muscle atrophy, we have performed the serial analysis of gene expression (SAGE) method with control and immobilized muscles of 10 rats. The genes that expressed >0.5% in muscle are involved in the following three functions: 1) contraction (troponin I, C and T; myosin light chain 1-3; actin; tropomyosin; and parvalbumin), 2) energy metabolism (cytochrome c oxidase I and III, creatine kinase, glyceraldehyde-3-phosphate-dehydrogenase, phosphoglycerate mutase, ATPase 6, and aldolase A), and 3) housekeeping (lens epithelial protein). Muscle atrophy appears to be caused by changes in mRNA levels of specific regulators of proteolysis, protein synthesis, and contractile apparatus assembling, such as polyubiquitin, elongation factor 2, and nebulin. Immobilization has produced a decrease more than threefold in gene expression of enzymes involved in energy metabolism, especially ATPase, cytochrome c oxidase, NADH dehydrogenase, and protein phosphatase 1. Differential gene expressions of selenoprotein W and uroporphyrinogen decarboxylase, which can be involved in oxidative stress, were also observed. Other genes with various functions, such as cholesterol metabolism and growth factors, were also differentially expressed. Moreover, novel genes regulated by immobilization were discovered. Thus, the current study allows a better understanding of global muscle characteristics and the molecular mechanisms of sedentarity and sarcopenia.

Species-specific expression of parvalbumin in the entorhinal cortex of the Mongolian gerbil: dependence on local activity but not extrinsic afferents

Mongolian gerbils are genetically predisposed to develop epileptic seizures in limbic structures. A species-specific property of the Mongolian gerbil is the expression of the calcium-binding protein parvalbumin in the perforant path where it is predominantly concentrated in nerve terminals. To test the hypothesis that this atypical expression of parvalbumin is induced by seizure-correlated hyperactivity in the entorhinohippocampal loop, we investigated whether it is dependent on extrinsic afferents to the entorhinal cortex. We cultivated organotypic slice cultures of neonate gerbil entorhinal cortex, isolated from all regions it is normally connected with in vivo. In these cultures, parvalbumin-expressing neurons demonstrated their characteristic features like in vivo. Blockade of spontaneous local activity with the sodium-channel blocker tetrodotoxin, however, considerably reduced the number of parvalbumin-expressing neurons in culture. These results indicate that spontaneous local activity, but not activity mediated by extrinsic afferents, is an essential factor for the expression of parvalbumin in the entorhinal cortex of the Mongolian gerbil.

Patterns of variant polyadenylation signal usage in human genes

The formation of mature mRNAs in vertebrates involves the cleavage and polyadenylation of the pre-mRNA, 10-30 nt downstream of an AAUAAA or AUUAAA signal sequence. The extensive cDNA data now available shows that these hexamers are not strictly conserved. In order to identify variant polyadenylation signals on a large scale, we compared over 8700 human 3' untranslated sequences to 157,775 polyadenylated expressed sequence tags (ESTs), used as markers of actual mRNA 3' ends. About 5600 EST-supported putative mRNA 3' ends were collected and analyzed for significant hexameric sequences. Known polyadenylation signals were found in only 73% of the 3' fragments. Ten single-base variants of the AAUAAA sequence were identified with a highly significant occurrence rate, potentially representing 14.9% of the actual polyadenylation signals. Of the mRNAs, 28.6% displayed two or more polyadenylation sites. In these mRNAs, the poly(A) sites proximal to the coding sequence tend to use variant signals more often, while the 3'-most site tends to use a canonical signal. The average number of ESTs associated with each signal type suggests that variant signals (including the common AUUAAA) are processed less efficiently than the canonical signal and could therefore be selected for regulatory purposes. However, the position of the site in the untranslated region may also play a role in polyadenylation rate.

Structure and developmental expression of the mouse CCK-B receptor gene

Cholecystokinin (CCK) and gastrin exert their effects through two receptors, the CCK-A and CCK-B receptors. We have cloned the mouse CCK-B receptor gene (Cckbr) and determined its complete genomic structure, nucleotide sequence, and tissue-specific expression pattern. Cckbr is divided into five exons spanning 11 kb. A primer extension assay was used to map the transcription initiation site to 199 bp upstream of the translational start site. Rapid amplification of cDNA ends was used to localize the 3' end downstream of an atypical polyadenylation site (GATAAA). Mouse Cckbr transcripts were most abundant in brain and stomach, but were also detected in colon, kidney, ovary, and pancreas. Prenatal expression of both CCK-A and CCK-B receptors in various tissues was analyzed by RT-PCR. The expression pattern was similar to the adult pattern, suggesting that receptor transcription is an early event in gastrointestinal development.

Granule cell hyperexcitability in the early post-traumatic rat dentate gyrus: the 'irritable mossy cell' hypothesis

1. Cytochemical and in vitro whole-cell patch clamp techniques were used to investigate granule cell hyperexcitability in the dentate gyrus 1 week after fluid percussion head trauma. 2. The percentage decrease in the number of hilar interneurones labelled with either GAD67 or parvalbumin mRNA probes following trauma was not different from the decrease in the total population of hilar cells, indicating no preferential survival of interneurones with respect to the non-GABAergic hilar cells, i.e. the mossy cells. 3. Dentate granule cells following trauma showed enhanced action potential discharges, and longer-lasting depolarizations, in response to perforant path stimulation, in the presence of the GABAA receptor antagonist bicuculline. 4. There was no post-traumatic alteration in the perforant path-evoked monosynaptic excitatory postsynaptic currents (EPSCs), or in the intrinsic properties of granule cells. However, after trauma, the monosynaptic EPSC was followed by late, polysynaptic EPSCs, which were not present in controls. 5. The late EPSCs in granule cells from fluid percussion-injured rats were not blocked by the NMDA receptor antagonist 2-amino-5-phosphonovaleric acid (APV), but were eliminated by both the non-NMDA glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the AMPA receptor antagonist GYKI 53655. 6. In addition, the late EPSCs were not present in low (0.5 mM) extracellular calcium, and they were also eliminated by the removal of the dentate hilus from the slice. 7. Mossy hilar cells in the traumatic dentate gyrus responded with significantly enhanced, prolonged trains of action potential discharges to perforant path stimulation. 8. These data indicate that surviving mossy cells play a crucial role in the hyperexcitable responses of the post-traumatic dentate gyrus.

Remodeling of the AB site of rat parvalbumin and oncomodulin into a canonical EF-hand

Parvalbumin (PV) and the homologous protein oncomodulin (OM) contain three EF-hand motifs, but the first site (AB) cannot bind Ca2+. Here we aimed to recreate the putative ancestral proteins [D19-28E]PV and [D19-28E]OM by replacing the 10-residue-long nonfunctional loop in the AB site by a 12-residue canonical loop. To create an optical conformational probe we also expressed the homologs with a F102W replacement. Unexpectedly, in none of the proteins did the mutation reactivate the AB site. The AB-remodeled parvalbumins bind two Ca2+ ions with strong positive cooperativity (nH = 2) and moderate affinity ([Ca2+]0.5 = 2 microM), compared with [Ca2+]0.5 = 37 nM and nH = 1 for the wild-type protein. Increasing Mg2+ concentrations changed nH from 2 to 0.65, but without modification of the [Ca2+]0. 5-value. CD revealed that the Ca2+ and Mg2+ forms of the remodeled parvalbumins lost one-third of their alpha helix content compared with the Ca2+ form of wild-type parvalbumin. However, the microenvironment of single Trp residues in the hydrophobic cores, monitored using intrinsic fluorescence and difference optical density, is the same. The metal-free remodeled parvalbumins possess unfolded conformations. The AB-remodeled oncomodulins also bind two Ca2+ with [Ca2+]0.5 = 43 microM and nH = 1.45. Mg2+ does not affect Ca2+ binding. Again the Ca2+ forms display two-thirds of the alpha-helical content in the wild-type, while their core is still strongly hydrophobic as monitored by Trp and Tyr fluorescence. The metal-free oncomodulins are partially unfolded and seem not to possess a hydrophobic core. Our data indicate that AB-remodeled parvalbumin has the potential to regulate cell functions, whereas it is unlikely that [D19-28E]OM can play a regulatory role in vivo. The predicted evolution of the AB site from a canonical to an abortive EF-hand may have been dictated by the need for stronger interaction with Mg2+ and Ca2+, and a high conformational stability of the metal-free forms.

Conformational stabilities of the rat alpha- and beta-parvalbumins

It is widely believed that beta-parvalbumin (PV) isoforms are intrinsically less stable than alpha-parvalbumins, due to greater electrostatic repulsion and an abbreviated C-terminal helix. However, when examined by differential scanning calorimetry, the apo-form of the rat beta-PV (i.e. oncomodulin) actually displays greater thermal stability than the alpha-PV. Whereas the melting temperature of the a isoform is 45.8 degrees C at physiological pH and ionic strength, the Tm for the beta isoform is more than 7 degrees higher (53.6 degrees C). This result suggests that factors besides net charge and C-terminal helix length strongly influence parvalbumin conformational stability. Extension of the F helix in the beta-PV, by insertion of Ser-109, has a modest stabilizing effect, raising the Tm, by 1.1 degrees. Truncation of the alpha-PV F helix, by removal of Glu-108, has a more profound impact, lowering the Tm by 4.0 degrees.

Age-related changes of calbindin-D28k, calretinin, and parvalbumin mRNAs in the hamster brain

Changes of three different cytosolic Ca2+ binding proteins, calbindin-D28k, calretinin, and parvalbumin mRNA expression in the brain of the hamster during aging were investigated by in situ hybridization using brains from hamsters aged 4, 9, 13, 19, to 24 months old. In cerebellum area, calbindin-D28k transcripts showed about 50% to 68% decrease in content in aged-hamster (19 and 24 months old) compared with young (4 months) and adult (9 months), whereas calretinin and parvalbumin mRNA expression remain unchanged throughout the ages examined. Calbindin-D28k gene expression was decreased during aging also in the hippocampus (approximately 60% reduction) and striatum (approximately 25%). In the same areas, striatum and hippocampus, calretinin and parvalbumin mRNA expression in the equivalent sections were not significantly changed with age. These data raise the possibility that CNS calbindin-D28k expression may be selectively down-regulated during aging. The statistically significant decrease of calbindin-D28k mRNA in the normal aging process also suggests and provides further support for the hypothesis that this calcium binding protein may have an important role in neuronal degeneration.

Expression of the calcium-binding protein, parvalbumin, in cultured cortical neurons using a HSV-1 vector system enhances NMDA neurotoxicity

Calcium-binding proteins (CaBPs) are a family of proteins having a unique distribution in the brain and are thought to be important in buffering intracellular calcium. Glutamate neurotoxicity is a process by which the over-activation of glutamate receptors can cause the influx of excessive extracellular calcium and neuronal cell death. It has been proposed that neurons containing CaBP may be more resistant to glutamate neurotoxicity due to their increased ability to buffer calcium. Using a herpes simplex virus-1 (HSV-1) vector system we packaged the CaBP gene, parvalbumin, or the marker gene, beta-galactosidase (beta-gal), correctly in viron particles, which were found upon infection to express mRNA specific to these vectors. PC12 and neocortical cultures showed strong immunohistochemical staining for either beta-gal or parv. The cortical cultures stained positively for endogenous glutamate decarboxylase, a marker for GABAergic neurons, but not for endogenous parvalbumin, indicating that parvalbumin was being expressed ectopically from the HSV-1 vector. Interestingly, the expression of parvalbumin increased cortical culture's susceptibility to N-methyl-D-aspartate-induced neurotoxicity. This increase in neurotoxicity was not due to the wild-type virus or the helper virus which accompanies the packaging of these vectors. We speculate that the ectopic expression of parvalbumin in cortical cultures may be increasing glutamate release which in turn increases cell death.

Transient colocalization of parvalbumin and calbindin D28k in the postnatal cerebral cortex: evidence for a phenotypic shift in developing nonpyramidal neurons

In the adult rat cerebral cortex the calcium-binding proteins parvalbumin and calbindin D28k are present in essentially non-overlapping populations of GABAergic interneurons. These proteins follow different developmental patterns in the cortex: calbindin D28k-immunoreactive nonpyramidal neurons are abundant until the second postnatal week and decrease markedly thereafter; it is at this time that parvalbumin immunoreactivity develops in cortical nonpyramidal neurons. To determine whether parvalbumin-immunoreactive neurons derive from calbindin D38k positive cells we used double-immunofluorescence studies for both calcium-binding proteins, together with combined immunocytochemistry for calbindin D28k and in situ hybridization for parvalbumin mRNA during postnatal development. Double-labelled cells were found in all cortical layers between P9 and P21, coinciding with the onset of parvalbumin expression. The percentage of colocalization of the two calcium-binding proteins depended on the age and layer examined. Colocalization reached a peak (80-100%) during the second postnatal week. Double-labelled neurons were rare in layer V at all ages studied. The present results indicate a phenotypic shift during the development of some cortical interneurons that halts the expression of calbindin D28k while parvalbumin expression starts. These findings agree with lineage analyses reporting that different types of nonpyramidal neuron arise from a common progenitor.

Molecular cloning and expression of alpha parvalbumin in the guinea pig cochlea

We have cloned and sequenced an alpha parvalbumin cDNA from the guinea pig cochlea. The deduced amino acid sequence shows greater identity with the rabbit sequence (86.3%) than with other mammalian sequences (< 82%). Using in situ hybridization and immunohistochemistry, alpha parvalbumin mRNA and protein were found in primary auditory neurons and inner hair cells, in agreement with RT-PCR data showing alpha parvalbumin mRNA expression in the spiral ganglion and the organ or Corti.

Parvalbumin expression during developmental differentiation of the rat ovary

Parvalbumin (PV) is a high-affinity Ca(2+)-binding protein which is expressed in a limited number of vertebrates tissues and restricted to a few distinct cell types. It has been shown by biochemical methods to be present in the adult rat ovary, but cellular localizations or developmental appearance have not been described until now. This study describes the presence of PV and its transcripts, analyzed by immunohistochemistry and in situ hybridization, respectively, during the postnatal development of the rat ovary: 13 developmental stages between day 1 and day 83 were examined. In ovaries 1-16 days old, neither PV mRNA nor PV was observed in any caaaaaaaaaaaaaay. By contrast, starting from day 18 postpartum, both PV mRNA and PV were detected in low amounts, simultaneously with the onset of differentiation of secondary intestitial gland cells in the ovarian interfollicular stroma. PV and its transcripts were primarily detected in conspicuous patches of interstitial gland tissue and in the differentiated thecal cells around the large follicles, and PV appeared to be fully expressed 33 days after birth. The parallel time courses of PV mRNA and PV accumulation during developmental differentiation, and the appearance of a steroid-producing cellular phenotype as well as the strict cellular colocalization of these two features, strongly suggest involvement of PV in the steroid metabolism of these cells, as earlier proposed for the Leydig cells of the testis. According to this hypothesis, we also show that suppression of gonadotrophic hormone production by hypophysectomy of adult rats totally suppresses PV production in parallel with the disappearance of the morphological features typical of steroid-producing cells in the remaining interstitial tissue of the ovary.

Developmental expression of parvalbumin mRNA in the cerebral cortex and hippocampus of the rat

Parvalbumin (PARV) belongs to the family of calcium-binding proteins bearing the EF hand domain. Immunocytochemical studies in the cerebral cortex have demonstrated that neurons containing PARV include two types of GABAergic interneurons, namely, basket and axo-axonic chandelier cells. The present study examines the onset and pattern of PARV mRNA expression during the development of rat neocortex and hippocampus by means of 'in situ' hybridization with an oligonucleotide probe corresponding to rat PARV cDNA. In animals aged P0-P6 no signal was detected above background in neocortex or hippocampus. At P8, a few cortical cells displayed a number of silver grains just above background levels. By P10 PARV mRNA-expressing cells in the neocortex were detected almost exclusively in layer V of somatosensory, frontal and cingulate cortices. At P12 PARV mRNA was mainly detected in layers IV, V and VIa. By P14 there was a marked overall increase in the entire neocortex, including layer II-III, both in the number of cells and in their intensity of labelling. Further maturation in the pattern of PARV mRNA concentration was observed between P16 and P21. In the hippocampus low hybridization was observed at P10-P12. In subsequent stages both the number of positive cells and the intensity of labelling increased steadily. No clear-cut radial gradients for the expression of PARV mRNA were observed in the hippocampal region. Our results show that the developmental radial gradient followed by PARV mRNA expression in the neocortex does not follow an 'inside-out' gradient, consistent with previous immunocytochemical findings. Taken together, these data indicate that the developmental sequence followed by the PARV protein directly reflects mRNA abundance and suggest that PARV mRNA expression correlates with the functional maturation of cortical interneurons.

Differential expression of mGluR5 metabotropic glutamate receptor mRNA by rat striatal neurons

Metabotropic glutamate receptors (mGluRs) mediate the effects of glutamate neurotransmission on intracellular second messenger systems. Among the seven distinct mGluR receptor isoforms currently identified, the mGluR5 isoform is expressed particularly prominently in the striatum, where it may contribute to neuronal plasticity, motor behaviors, and excitotoxic injury. mGluR5 mRNA expression in striatal enkephalinergic, somatostatinergic, and cholinergic neurons was examined using double label in situ hybridization techniques. mGluR5 expression is abundant in a large number of medium-sized striatal cells but is absent in a significant minority of neurons. Double label in situ hybridization with 35S-dATP- and digoxygenin-dUTP-tailed oligonucleotide probes demonstrated that mGluR5 message is highly expressed by enkephalinergic striatal neurons but is not detectable in cholinergic or somatostatin interneurons. In addition, some nonenkephalin, presumably substance P, neurons were also strongly labeled for mGluR5. The differential expression of mGluR5 in striatal projection neurons vs. interneurons may contribute to the selective vulnerability of these neurons to disease processes.

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.

Subtractive cDNA cloning as a tool to analyse secondary effects of a muscle disease. Characterization of affected genes in the myotonic ADR mouse

In myotonic ADR mice that are homozygous for a defect in the muscular chloride channel gene adr/Clc-1, the hyperexcitability of fast muscles is associated with secondary changes in gene expression and fibre type composition. cDNA clones derived from a set of genes down regulated in fast muscles of the myotonic ADR mouse were isolated by a subtractive cloning procedure. A total of 1200 clones were analysed for high expression in fast muscle of wild type and low expression in mutant mouse. Differential transcript levels were verified by northern blot hybridizations. The identities of the corresponding transcripts were determined by sequencing as myosin heavy chain IIB, alpha-tropomyosin, troponin C, a Ca2+ ATPase and parvalbumin mRNAs. Of these, mRNAs for parvalbumin and myosin heavy chain IIB were drastically downregulated in myotonic muscle (to < 10% of control). A full length cDNA clone for skeletal muscle alpha-tropomyosin was homologous to the mouse fibroblast tropomyosin isoform 2, except for the portion encoding the alpha-tropomyosin specific amino acids 258-284. A cDNA derived from the 1100 nucleotide parvalbumin transcript was cloned and the sequence for the as yet unknown 3' extended trailer, generated by alternative polyadenylation, was determined.

Distribution of calcium binding protein mRNAs in rat cerebellar cortex

The distribution of three calcium binding protein mRNAs in the rat cerebellar cortex was investigated using alkaline phosphatase labelled specific antisense oligodeoxynucleotide probes. Calbindin D28k mRNA was detected in the Purkinje cells, parvalbumin mRNA was located in the Purkinje cells and also in basket/stellate cells of the molecular layer. Calretinin in contrast was found only in the granule cell layer. Use of multiple alkaline phosphatase (AP)-labelled oligodeoxynucleotides resulted in an increase in signal strength and reduced detection time with no increase in background staining indicating the utility of these enzyme labelled probes for non-isotopic in situ.

Immunoreactive parvalbumin concentrations in parahippocampal gyrus decrease in patients with Alzheimer's disease

By using a sensitive enzyme immunoassay system for rat parvalbumin, we determined parvalbumin contents in the 4 cerebrocortical regions (superior frontal gyrus of frontal lobe, parahippocampal gyrus of temporal lobe, superior parietal lobule of parietal lobe, and calcarine area of occipital lobe) of patients with Alzheimer's disease and age-matched controls. Among the 4 regions, concentrations of parvalbumin were the highest in calcarine area (68.6 +/- 6.7 ng/mg protein, rat parvalbumin equivalents, mean +/- SE) and the lowest in the parahippocampal gyrus (11.0 +/- 1.7 ng/mg protein) in the controls. A similar regional difference of the concentration was observed also in the patients with Alzheimer's disease. When compared with the controls, however, concentrations of parvalbumin in parahippocampal gyrus of patients with Alzheimer's disease (4.0 +/- 0.9 ng/mg protein) were significantly low (P less than 0.01), showing less than a half of the control values. In contrast, the concentrations in the 3 other regions showed little difference between Alzheimer's disease and the controls.

The structure of the mouse parvalbumin gene

Parvalbumin (PV) is a calcium-binding protein of the EF-hand family, expressed mainly in fast contracting/relaxing muscles of vertebrates. We have isolated five overlapping genomic PV clones which overall span 28 kilobase pairs (kb) around the Pva locus on mouse Chromosome (Chr) 15. The positions of four introns were determined by DNA sequencing. They interrupt the coding sequences at positions corresponding to those in rat and human PV genes. The transcription start site, 25 bp downstream from the TATA-box, was mapped by oligonucleotide primer extension on poly(A)(+)-RNA. The analysis of 0.4 kb promoter sequence of the mouse PV gene revealed CCAAT- and TATA-box sequences and a 59 bp GC-rich stretch between positions -59 and -118. Similar motifs have been found in the parvalbumin genes of rat and human. A perfect 11-bp repeat upstream to positions -149 and -163 respectively is homologous only to the rat promoter. These results will be related to tissue and species differences in PV expression.

Structure and expression of the Aplysia californica calmodulin gene

We have isolated and characterized the calmodulin (CaM) gene of the marine mollusc Aplysia californica. Its primary structure, deduced from the nucleotide sequence of the gene, is highly conserved, containing only three amino acid substitutions compared to the CaM of higher vertebrates. The structural gene consists of four exons that encode the protein, 3' non-translated mRNA and at least one additional exon encoding 5' non-translated mRNA and the initiator methionine. A comparison of the exon/intron structure of CaM genes from several organisms shows conservation of intron position, suggesting that introns have been both inserted and deleted during evolution. Northern analysis of RNA prepared from several Aplysia tissues reveals the presence of several CaM mRNA transcripts with the greatest expression observed in neural and muscle tissue. One of these transcripts is abundant only in mRNA prepared from nervous tissue.

Evolution of EF-hand calcium-modulated proteins. I. Relationships based on amino acid sequences

The relationships among 153 EF-hand (calcium-modulated) proteins of known amino acid sequence were determined using the method of maximum parsimony. These proteins can be ordered into 12 distinct subfamilies--calmodulin, troponin C, essential light chain of myosin, regulatory light chain, sarcoplasmic calcium binding protein, calpain, aequorin, Stronglyocentrotus purpuratus ectodermal protein, calbindin 28 kd, parvalbumin, alpha-actinin, and S100/intestinal calcium-binding protein. Eight individual proteins--calcineurin B from Bos, troponin C from Astacus, calcium vector protein from Branchiostoma, caltractin from Chlamydomonas, cell-division-cycle 31 gene product from Saccharomyces, 10-kd calcium-binding protein from Tetrahymena, LPS1 eight-domain protein from Lytechinus, and calcium-binding protein from Streptomyces--are tentatively identified as unique; that is, each may be the sole representative of another subfamily. We present dendrograms showing the relationships among the subfamilies and uniques as well as dendrograms showing relationships within each subfamily. The EF-hand proteins have been characterized from a broad range of organismal sources, and they have an enormous range of function. This is reflected in the complexity of the dendrograms. At this time we urge caution in assigning a simple scheme of gene duplications to account for the evolution of the 600 EF-hand domains of known sequence.

Partial nucleotide sequence of the parvalbumin from chicken thymus designated "avian thymic hormone"

The incomplete amino acid sequence of the protein identified as avian thymic hormone was recently reported [Brewer et al. (1989), Biochem. Biophys. Res. Commun. 160, 11555-1161], and a very high degree of homology to the parvalbumins was apparent. Using mixed oligonucleotide primers based on the reported protein sequence, we have succeeded in amplifying and cloning a 188 bp fragment of the coding region for this protein, beginning with double-stranded cDNA prepared from chicken thymus mRNA. The translated nucleotide sequence of this fragment and the reported amino acid sequence display substantial disagreement. Most notably, the nucleotide sequence indicates that the CD site of avian thymic hormone is a typical parvalbumin CD site.

Parvalbumin genes from human and rat are identical in intron/exon organization and contain highly homologous regulatory elements and coding sequences

The structural organization of the chromosomal gene for human parvalbumin was determined mostly by sequencing exons and intron exon junctions of a 7500 base-pair (bp) long genomic clone derived from a chromosome 22-specific gene library. Four exons coding for 100 from a total of 109 amino acids were detected in this clone and 472 bp of the 5'-flanking region were sequenced. The region corresponding to the C-terminal amino acids 101 to 109 of human parvalbumin was determined by sequencing a cDNA fragment derived from human brain mRNA after amplification by the polymerase chain reaction. The first intron is placed 7 bp upstream from the ATG translation start signal, whereas all other splice sites divide putative Ca2+-binding domains. All intron positions coincide exactly with those reported for the rat parvalbumin gene. The 5' mRNA leader sequence has a similarity of 57%, the coding region of 91% and the 3' non-coding region of 83% to the corresponding rat sequences. Only nine conservative amino acid replacements were observed between human and rat parvalbumins. The predicted secondary structures for human, rat, mouse and rabbit parvalbumins are very similar, indicating a strong structural relationship among mammalian parvalbumins. Several elements with potential transcription regulatory activities were found in the region immediately 5' to the transcription start site including a TATA box (TATATA) and a CAAT box (CCAAAAT). Several regions in the putative promoter are strongly conserved between the human and rat parvalbumin genes. One of these with a length of 32 bp is identical with the rat counterpart and has a high degree of homology to a promoter region in the myosin light chain 3F gene, which is expressed in fast contracting/relaxing muscle fibers (anaerobic/type IIb), the cell type that also exhibits highest levels of parvalbumin expression. The human parvalbumin mRNA contains the putative polyadenylation signal AATAAA 13 nucleotides upstream from the polyadenylation site. A 700-nucleotide long parvalbumin mRNA is synthesized at low levels in the human cerebellum as well as in the neuroblastoma cell line SK-N-BE.

cDNA sequence and chromosomal localization of the mouse parvalbumin gene, Pva

In the homozygous condition, the mutation adr (arrested development of righting response) of the mouse causes a myotonia and a drastic reduction of the Ca2+-binding protein parvalbumin (PV) in fast muscles. Using a rat PV probe, a mouse cDNA clone was isolated from a lambda gt11 wild-type fast-muscle library and its nucleotide sequence was determined. The protein coding and the 3' nontranslated regions of the mouse gene show extensive homology with the rat PV gene. The result of Southern blot hybridization is consistent with a single copy gene for parvalbumin. Restriction fragment length polymorphisms (RFLPs) between Mus musculus domesticus (e.g. C57BL/6) and Mus spretus (SPE) were detected with the enzymes Eco RI, Pst I, and Sst I. The restriction fragment patterns of DNA samples from 65 individual offspring of (C57BL/6 x SPE)F1 x C57BL/6 backcrosses were tested with the PV probe and matched, for linkage detection, to pre-existing patterns established with various RFLP probes on the same samples. A co-distribution of PV-RFLPs with Pvt-1 and Mlvi-2, which had been localized on chromosome 15, was detected. Thus, the structural gene for PV, designated Pva, maps to chromosome 15 of the mouse whereas the adr mutation shows no linkage with markers on this chromosome. Gene locus homology between chromosome 15 of the mouse and chromosome 22 of man (which carries the human PV gene) is discussed.

Opposite regulation of the mRNAs for parvalbumin and p19/6.8 in myotonic mouse muscle

The gene mutation in the mouse, 'arrested development of righting response', adr, causes a defect of chloride conductance of the muscle fibre membrane leading to the symptoms of myotonia [Mehrke, G., Brinkmeier, H. and Jockusch, H. (1988) Muscle & Nerve 11, 440-446]. In fast muscle, the myotonic phenotype is accompanied by a drastic reduction of the Ca2+-binding protein, parvalbumin. Messenger RNA levels in organs of myotonic (ADR) mice were analysed. In fast muscles of the mutant, in-vitro-translatable parvalbumin mRNA was strongly reduced, whereas the mRNA for the slow-muscle-specific protein, p19/6.8, was increased. In contrast, the parvalbumin mRNA in the cerebellum was not affected by the adr mutation. A reduction of the two parvalbumin mRNA species (700 and 1100 nucleotides) in ADR fast muscle and unaltered parvalbumin mRNA levels in mutant cerebella were demonstrated by cDNA/mRNA hybridisation, using a rat parvalbumin cDNA as a probe. The mRNA level for another Ca2+-binding protein, calmodulin, was low in muscle and high in the central nervous system but was unaffected by the mutation. When adr/adr mice were fed a diet containing the membrane-stabilising drug, tocainide, the levels in muscle of the mRNAs for parvalbumin and p19/6.8 were partially normalised.

Structure and sequence of the Drosophila melanogaster calmodulin gene

A series of phage clones overlapping the single calmodulin gene locus of Drosophila melanogaster has been isolated and the exons of the gene positioned and sequenced within these clones. A calmodulin cDNA clone of the electric eel was used to identify these clones and to position the two major protein-coding exons of the gene. cDNA clones for D. melanogaster calmodulin were then isolated, characterized and used to identify the remaining exons. The gene consists of four exons separated by three introns of 3400 to 4300 bases in length. Exon 1 consists of the 5' untranslated region and the initiator ATG; exon 2 encodes amino acid residues 1 to 58.3; exon 3 encodes residues 58.3 to 139.3; and exon 4 encodes residues 139.3 to 148 and the 3' untranslated region. From the sequence of the 3' untranslated region and the lengths of the cDNA clones, two or three polyadenylation sites are indicated. Sequences potentially involved in the control of transcription of the gene and splicing of the mRNA product have been identified. Comparison of the intron-exon structures of the D. melanogaster calmodulin gene, the chick calmodulin gene, and other genes of the troponin C superfamily reinforces previous hypotheses that these genes arose from a common progenitor and permits identification of four introns that were probably present in the progenitor gene structure. The D. melanogaster calmodulin gene contains three of these introns, and the chick gene contains all four. These gene comparisons also indicate that the region of these genes encoding Ca2+-binding loop 3 is highly variable in structure. The chick and D. melanogaster calmodulin genes differ in this region, the chick gene containing a fifth intron here that is absent from the D. melanogaster gene.