Isolation of neuronal parvalbumin by high-performance liquid chromatography. Characterization and comparison with muscle parvalbumin

Comprehensive analysis of the roles of 'black' and 'gray' clusters in structure and function of rat β-parvalbumin

Recently we found two highly conserved structural motifs in the proteins of the EF-hand calcium binding protein family. These motifs provide a supporting scaffold for the Ca²⁺ binding loops and contribute to the hydrophobic core of the EF-hand domain. Each structural motif forms a cluster of three amino acids called cluster I ('black' cluster) and cluster II ('grey' cluster). Cluster I is much more conserved and mostly incorporates aromatic amino acids. In contrast, cluster II includes a mix of aromatic, hydrophobic, and polar amino acids. The 'black' and 'gray' clusters in rat β-parvalbumin consist of F48, A100, F103 and G61, L64, M87, respectively. In the present work, we sequentially substituted these amino acids residues by Ala, except Ala100, which was substituted by Val. Physical properties of the mutants were studied by circular dichroism, scanning calorimetry, dynamic light scattering, chemical crosslinking, and fluorescent probe methods. The Ca²⁺ and Mg²⁺ binding affinities of these mutants were evaluated by intrinsic fluorescence and equilibrium dialysis methods. In spite of a rather complicated pattern of contributions of separate amino acid residues of the 'black' and 'gray' clusters into maintenance of rat β-parvalbumin structural and functional status, the alanine substitutions in the cluster I cause noticeably more pronounced changes in various structural parameters of proteins, such as hydrodynamic radius of apo-form, thermal stability of Ca²⁺/Mg²⁺-loaded forms, and total energy of Ca²⁺ binding in comparison with the changes caused by amino acid substitutions in the cluster II. These findings were further supported by the outputs of computational analysis of the effects of these mutations on the intrinsic disorder predisposition of rat β-parvalbumin, which also indicated that local intrinsic disorder propensities and the overall levels of predicted disorder were strongly affected by mutations in the cluster I, whereas mutations in cluster II had less pronounced effects. These results demonstrate that amino acids of the cluster I provide more essential contribution to the maintenance of structuraland functional properties of the protein in comparison with the residues of the cluster II.

A Ca(2+)-binding protein with numerous roles and uses: parvalbumin in molecular biology and physiology

Parvalbumins (PVs) are acidic, intracellular Ca(2+)-binding proteins of low molecular weight. They are associated with several Ca(2+)-mediated cellular activities and physiological processes. It has been suggested that PV might function as a "Ca2+ shuttle" transporting Ca2+ from troponin-C (TnC) to the sarcoplasmic reticulum (SR) Ca2+ pump during muscle relaxation. Thus, PV may contribute to the performance of rapid, phasic movements by accelerating the contraction-relaxation cycle of fast-twitch muscle fibers. Interestingly, PVs promote the generation of power stroke in fish by speeding up the rate of relaxation and thus provide impetus to attain maximal sustainable speeds. However, immunological monitoring of diverse tissues demonstrated that PVs are also present in non-muscle cells. The axoplasmic transport and various intracellular secretory mechanisms including the endocrine secretions seem to be controlled by the Ca2+ regulation machinery. Any defect in the Ca2+ handling apparatus may cause several clinical problems; for instance, PV deficiency alters the neuronal activity, a key mechanism leading to epileptic seizures. Moreover, atypical relaxation of the heart results in diastolic dysfunction, which is a major cause of heart failure predominantly among the aged people. PV may offer a unique potential to correct defective relaxation in energetically compromised failing hearts through PV gene transfer. Consequently, PV gene transfer may present a new therapeutic approach to correct cellular disturbances in Ca2+ signaling pathways of diseased organs. Hence, PVs appear to be amazingly useful candidate proteins regulating a variety of cellular functions through action on Ca2+ flux management.

The reversal by sulfate of the denaturant activity of guanidinium

Guanidinium (Gdm+) chloride is a powerful protein denaturant, whereas the sulfate dianion (SO42-) is a strong stabilizer of folded protein states; Gdm2SO4 is effectively neutral in its effects on protein stability. While the "neutralizing" effects of protein-stabilizing solutes on the activity of denaturants can be broadly interpreted in terms of additive effects of the solutes, recent experimental and simulation studies support a role for hetero-ion interactions in the effect of sulfate on Gdm+ denaturation [Mason, P. E.; et al. J. Phys. Chem. B 2005, 109, 24185-24196]. Here we describe an experimental strategy for testing this mechanism that involves spectroscopic analysis of the separate effects of alkali metal sulfates (Na2SO4, Rb2SO4), GdmCl, and Gdm2SO4 on the folded populations of several peptides chosen to dissect specific noncovalent contributions to the conformational stability of proteins [alanine-based helical peptides stabilized by hydrogen bonds, tryptophan zipper (trpzip) peptides stabilized largely by cross-strand indole-indole interactions]. While the trpzip peptides are highly sensitive to GdmCl denaturation, they are unaffected by NaCl, Na2SO4, or Gdm2SO4, indicating that the reversal of the denaturant activity of Gdm+ by sulfate in this case is not due to competing stabilizing (sulfate) and destabilizing (Gdm+) interactions. Gdm2SO4 was found to retain considerable denaturant activity against alanine-based alpha-helical peptides. The differences in the effects of Gdm2SO4 on the two peptide types can be understood in terms of the different mechanisms of Gdm+ denaturation of trpzip peptides and helical peptides, respectively, and the specific nature of Gdm+ and SO42- ionic "clustering" that differentially affects the ability of Gdm+ to make the molecular interactions with the peptides that underlie its denaturant activity.

Interfacial Water Structure Controls Protein Conformation

A phenomenological theory of salt-induced Hofmeister phenomena is presented, based on a relation between protein solubility in salt solutions and protein-water interfacial tension. As a generalization of previous treatments, it implies that both kosmotropic salting out and chaotropic salting in are manifested via salt-induced changes of the hydrophobic/hydrophilic properties of protein-water interfaces. The theory is applied to describe the salt-dependent free energy profiles of proteins as a function of their water-exposed surface area. On this basis, three classes of protein conformations have been distinguished, and their existence experimentally demonstrated using the examples of bacteriorhodopsin and myoglobin. The experimental results support the ability of the new formalism to account for the diverse manifestations of salt effects on protein conformation, dynamics, and stability, and to resolve the puzzle of chaotropes stabilizing certain proteins (and other anomalies). It is also shown that the relation between interfacial tension and protein structural stability is straightforwardly linked to protein conformational fluctuations, providing a keystone for the microscopic interpretation of Hofmeister effects. Implications of the results concerning the use of Hofmeister effects in the experimental study of protein function are discussed.

Hofmeister salt effects on surface tension arise from partitioning of anions and cations between bulk water and the air-water interface

We apply a recently developed surface-bulk partitioning model to interpret the effects of individual Hofmeister cations and anions on the surface tension of water. The most surface-excluded salt (Na2SO4) provides a minimum estimate for the number of water molecules per unit area of the surface region of 0.2 H2O A-2. This corresponds to a lower bound thickness of the surface region of approximately 6 A, which we assume is a property of this region and not of the salt investigated. At salt concentrations < or = 1 m, single-ion partition coefficients Kp,i, defined relative to Kp,Na+ = Kp,SO42- = 0, are found to be independent of bulk salt concentration and additive for different salt ions. Semiquantitative agreement with surface-sensitive spectroscopy data and molecular dynamics simulations is attained. In most cases, the rank orders of Kp,i for both anions and cations follow the conventional Hofmeister series, qualitative rankings of ions based on their effects on protein processes (folding, precipitation, assembly). Most anions that favor processes that expose protein surface to water (e.g., SCN-), and hence must interact favorably with (i.e., accumulate at) protein surface, are also accumulated at the air-water interface (Kp >1, e.g., Kp,SCN- =1.6). Most anions that favor processes that remove protein surface from water (e.g., F-), and hence are excluded from protein surface, are also excluded from the air-water interface (Kp,F- = 0.5). The guanidinium cation, a strong protein denaturant and therefore accumulated at the protein surface exposed in unfolding, is somewhat excluded from the air-water surface (Kp,GuH+ = 0.7), but is much less excluded than alkali metal cations (e.g., Kp,Na+ identical with 0, Kp,K+ = 0.1). Hence, cation Kp values for the air-water surface appear shifted (toward exclusion) as compared with values inferred for interactions of these cations with protein surface.

Local Composition in the Vicinity of a Protein Molecule in an Aqueous Mixed Solvent

This paper is focused on the composition of a cosolvent in the vicinity of a protein surface (local composition) and its dependence on various factors. First, the Kirkwood-Buff theory of solution is used to obtain analytical expressions that connect the excess or deficit number of cosolvent and water molecules in the vicinity of a protein surface with experimentally measurable quantities such as the bulk concentration of the mixed solvent, the preferential binding parameter, and the molar volumes of water and cosolvent. Using these expressions, relations between the preferential binding parameter (at a molal concentration scale) and the above excesses (or deficits) are established. In addition, the obtained expressions are used to examine the effect of the nonideality of the water + cosolvent mixtures and of the molar volume of the cosolvent on the excess (or deficit) number of cosolvent molecules in the vicinity of the protein surface. It is shown that at least for the mixed solvents considered (water + urea and water + glucose) the nonideality of the mixed solvent is not an important factor in the local compositions around a protein molecule and that the main contribution is provided by the nonidealities of the protein-water and protein-cosolvent mixtures. Special attention is paid to urea as cosolvent, because urea is one of only a few compounds with a concentration at the protein surface larger than its concentration in the bulk. The composition dependence of the excess of urea around a protein molecule is calculated for the water + lysozyme + urea mixture at pH = 7.0 and 2.0. At pH = 7.0, the excess of urea becomes almost composition independent at high urea concentrations. Such independence could be explained by assuming that urea totally replaces water in some areas of the protein surface, whereas on the remaining areas of the protein surface both water and urea are present with concentration comparable to those in the bulk. The Schellman exchange model was used to relate the preferential binding parameter in water + lysozyme + urea mixtures to the urea concentration.

Mesoscopic simulation of adsorption of peptides in a hydrophobic chromatography system

Mesoscopic simulations using Langevin dipoles on a lattice for the solvent and calculated partial charges for the solute have been used to estimate free energies of adsorption from data on reversed-phase chromatography on nine protected peptides covering a wide range of structures. There is a single parameter, the effective solvent dipole moment, that is fit to data for one peptide and used to predict properties of the other eight peptides. Good agreement of adsorption chemical potentials, including order of chromatographic retention times, is found for calculations that are Boltzmann-averaged over a set of orientations. In addition, the results suggest that there are preferential orientations for each peptide at the model hydrophobic chromatographic surface. Estimation methods for adsorption based on molecular descriptors and hydrophobicity scales are shown to be unreliable for these systems. With refinements and extensions, this simulation method should be applicable to solvents containing salt, such as in hydrophobic interaction chromatography, and to larger solutes including proteins.

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.

Spectroscopic studies of the intermolecular interactions of Congo red and tinopal CBS with modified cellulose fibers

The adsorption of Congo red and tinopal CBS dyes on cellulose fibers was investigated using electronic absorption and fluorescence spectroscopies. Hydrogen bonds appear to be relevant for the dye-fiber interactions as indicated by the solvatochromism of Congo red in water, methanol, and dimethyl sulfoxide solutions, and when adsorbed on cellulose fibers. We also demonstrate that electrostatic interactions play an important role in the dye-medium interaction, through the analysis of absorption spectra of Congo red and fluorescence spectra of tinopal in aqueous solutions containing salt and in layer-by-layer nanostructured films with poly(allylamine hydrochloride). For instance, dye adsorption was enhanced when salt was added to the dipping solution, which was explained by the synergistic effect between the conformational changes of the cellulose and changes in the solvation layer around the cellulose chains and around dye molecules. On the basis of the fluorescence results for tinopal CBS, we inferred that dye aggregation is not relevant for adsorption on the fibers. In addition, fluorescence spectroscopy is proven very sensitive for studying the organization of dye molecules in layer-by-layer films, particularly those undergoing irreversible structural changes.

Identification of parvalbumin alpha in bovine hypothalamus: a partial primary structure

In the course of the study of structure-functional properties and molecular mechanisms of neuropeptides and of low molecular weight proteins of the central nervous system we succeeded in isolating from the soluble fraction of bovine hypothalamus a protein having M(r) 11897.3, according to mass spectral analysis. The purification procedure was mainly based on reversed phase HPLC. As the N-terminus of the molecule was found to be blocked, we have subjected it to CNBr degradation. By Edman microsequence analysis of the peptide fragments and by data base searching the isolated substance was identified as parvalbumin alpha (PRVA)-one of the calcium-binding proteins. However, its primary structure was found not to be identical to that of the known PRVAs from other sources. One of the features of PRVA is its stability. Being subjected to an exhausting purification procedure it retains its complete structure. As neuropeptides and low molecular weight proteins are found to be polyfunctional, a central question concerns the biological role of PRVAs in terms of "where and when" they express their action.

Intracellular concentration of parvalbumin in nerve cells

Parvalbumin is supposed to function as an intracellular Ca2+ buffer in the brain, but its concentration in nerve cells is unknown. We combined radioimmunoassay of parvalbumin in rat brain extracts, together with image analysis of area fractions immunostained with the parvalbumin antibody on sections, to deduce the intracellular concentration of parvalbumin. We found that the average amount of parvalbumin varied between 6 microM in the caudatoputamen and 45 microM in the cerebellum. Although these values are only rough averages and do not demonstrate a Ca2+ buffering role for parvalbumin in neurons, the concentration of the protein is at least in the appropriate range for such a function.

Calcium-binding proteins in Aplysia neurons

1. Calcium (Ca)-binding proteins of neuronal ganglia and of single, identified neurons of the marine mollusk, Aplysia californica, were investigated. Using transblot/45Ca overlays two proteins, at Mr 45,000 and Mr 23,000, with a high Ca-binding ability were found. 2. Western blot analysis revealed that the protein at Mr 45,000 could be separated by 2D-PAGE into proteins with Mr 40,000 and Mr 43,000. The protein at Mr 40,000 immunocross-reacted with antisera directed against parvalbumin and rat calbindin D-28K, indicating a novel Ca-binding protein sharing common antigenic determinants for both proteins. 3. The protein at Mr 23,000 could be separated into a group of proteins with Mr 13,000-20,000 which showed a high degree of similarity to sarcoplasmatic calcium-binding proteins (SCP). 4. We further investigated the protein pattern of single, identified neurons of different electrical activity (bursting, beating, and silent) by 2D-PAGE. Major differences were found in the range of low Mr and low pI, where Ca-binding proteins are generally located. A protein at high concentrations characteristic for silent cells migrated at a position similar to crayfish SCP. 5. The results show that various Ca-binding proteins are characteristic for neurons in the Aplysia nervous system and support the idea that they may effect the electrical behavior of nerve cells.

Parvalbumin-immunoreactive neurons in the human central nervous system are decreased in Alzheimer's disease

Immunohistochemical localization of the Ca(2+)-binding protein parvalbumin (PV) was investigated in the adult human central nervous system (CNS). The antiserum against purified rat skeletal muscle PV specifically recognized certain neuronal populations and their processes. Strongly positive were Purkinje, basket and stellate cells of the cerebellum, cerebral cortical nonpyramidal cells, and neurons in the thalamic reticular and ventrolateral nuclei, subthalamic nucleus, lateral and medial geniculate bodies, vestibular and cochlear nuclei, spinal trigeminal nucleus, cuneate and gracile nuclei, and dorsal nucleus of Clarke. Negative were cortical pyramidal neurons, neurons of the autonomic nerves, and neurons in the caudate nucleus, putamen, dentate nucleus, inferior olive, and substantia gelatinosa. The number and size of PV-immunoreactive neurons were significantly decreased in Alzheimer's disease. However, the decrease was not disease specific.

Molecular cloning of the thymus-specific parvalbumin known as avian thymic hormone: isolation of a full length cDNA and expression of the recombinant protein in Escherichia coli

The complete coding sequence of the thymus-specific parvalbumin called avian thymic hormone (ATH) has been cloned into Escherichia coli. The translated amino acid sequence was found to be identical to the sequence of map turtle parvalbumin at 90 of 108 positions. Northern blot analysis of thymic RNA indicated a transcript length of approximately 1050 bp. However, the ATH cDNA probe failed to hybridize to poly(A)+ RNA from chicken leg muscle, a further indication that avian thymic hormone is distinct from the muscle-associated parvalbumin previously isolated from chicken. Southern analysis of chicken genomic DNA suggests the presence of a single copy of the ATH gene, and the absence of hybridization between an ATH cDNA fragment and genomic DNA from rat and rabbit is confirmatory evidence that ATH expression is restricted to avian species. One of the full length ATH cDNA clones harbored an insert that lacked all 5' noncoding sequences. This cDNA was inserted without further alteration into the prokaryotic expression vector, pKK223-3. The resulting construction, which contains eleven base pairs between the Shine-Dalgarno sequence and the initiation codon, affords reasonably high levels of expression in E. coli. In most respects, recombinant ATH mimics the tissue-derived protein, retaining a similarly high affinity for Ca2+ ion (KCa = 14 +/- 5 nM). However, in contrast to ATH isolated from chicken thymus tissue, the N-terminal alanine of recombinant ATH is unacetylated. As a result, the isoelectric point is shifted upward from 4.3 to approximately 4.8.

Calcyclin is a calcium and zinc binding protein

Calcyclin, a cell cycle regulated protein, was recently purified from Ehrlich ascites tumour (EAT) cells and shown to be a calcium binding protein. Here we show that calcyclin monomer and dimer also bind zinc ions. Zinc binding sites seem to be different from calcium binding sites since: preincubation with Ca2+ lacks effect on the binding of Zn2+, and Ca2+ (but not Zn2+) increases tyrosine fluorescence intensity. Binding of Zn2+ reduces the extent of the conformational changes induced by Ca2+, and seems to affect Ca2(+)-binding. The data suggest that Ca2+ and Zn2+ might trigger the biological activity of calcyclin.

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.

Calbindin D-28k and parvalbumin in the rat nervous system

This paper describes the distribution of structures stained with mono- and polyclonal antibodies to the calcium-binding proteins calbindin D-28k and parvalbumin in the nervous system of adult rats. As a general characterization it can be stated that calbindin antibodies mainly label cells with thin, unmyelinated axons projecting in a diffuse manner. On the other hand, parvalbumin mostly occurs in cells with thick, myelinated axons and restricted, focused projection fields. The distinctive staining with antibodies against these two proteins can be observed throughout the nervous system. Calbindin D-28k is primarily associated with long-axon neurons (Golgi type I cells) exemplified by thalamic projection neurons, strionigral neurons, nucleus basalis Meynert neurons, cerebellar Purkinje cells, large spinal-, retinal-, cochlear- and vestibular ganglion cells. Calbindin D-28k occurs in all major pathways of the limbic system with the exception of the fornix. Calbindin D-28k is, however, also found in some short-axon cells (Golgi type II), represented by spinal cord interneurons in layer II and interneurons of the cerebral cortex. It is also detectable in some ependymal cells and abundantly occurs in vegetative centres of the hypothalamus. The "paracrine core" of the nervous system and its adjunct (1985, Nieuwenhuys, Chemoarchitecture of the Brain. Springer, Berlin) is very rich in calbindin D-28k. The distribution of calbindin D-28k-positive neurons is very similar to that of the dihydroperydine subtype of calcium channels. Most of the cells containing calbindin D-28k are vulnerable to neurodegenerative processes. Parvalbumin-immunoreactive neurons have a different, and mostly complementary distribution compared with those which react with calbindin D-28k antisera, but in a few cases (Purkinje cells of the cerebellum, spinal ganglion neurons), both calcium-binding proteins co-exist in the same neuron. Many parvalbumin-immunoreactive cells in the central nervous system are interneurons (Golgi type II) and, to a lesser extent, long-axon cells (Golgi type I), whereas conditions are vice versa in the peripheral nervous system. Intrinsic parvalbuminic neurons are prominent in the cerebral cortex, hippocampus, cerebellar cortex and spinal cord. Long-axon parvalbumin-immunoreactive neurons are, for example, the Purkinje cells, neurons of the thalamic reticular nucleus, globus pallidus, substantia nigra (pars reticulata) and a subpopulation among large spinal-, retinal-, cochlear- and vestibular ganglion cells. Parvalbumin is rich in cranial nerve nuclei related to eye movements. In addition to nervous elements, parvalbumin immunoreactivity occurs in a few ependymal cells and in some pillar cells of the organ of Corti.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium-binding protein from mouse Ehrlich ascites-tumour cells is homologous to human calcyclin

A Ca2+-binding protein was purified from mouse Ehrlich ascites-tumour cells. The protein forms monomers and disulphide-linked dimers, which can be separated by reverse-phase h.p.l.c. A partial amino acid sequence analysis demonstrated that the protein has an EF-hand structure. A striking homology was found to rat and human calcyclin (a member of the S-100 protein family), which is possibly involved in cell-cycle regulation.

Parvalbumin in mouse muscle in vivo and in vitro

Parvalbumin is a cytosolic calcium-binding protein found in adult fast-twitch mammalian muscle. Using an antibody to paravalbumin, we have shown that its distribution in adult mouse muscles is associated with certain fibre types. It is absent from slow-twitch type 1 fibres, is absent or at low levels in fast-twitch type 2A fibres, but is present at moderate or high levels in fast-twitch type 2B fibres. When adult mouse muscle is cultured with embryonic mouse spinal cord, the regenerated fibres become innervated, express the adult fast isoform of myosin heavy chain and appear histochemically as fast-twitch fibres. We therefore investigated whether these apparently mature fibres also contained parvalbumin. Parvalbumin was not found in any fibres of twenty mature cultures, suggesting that neurotrophic activity in the absence of specific adult nerve activity patterns was insufficient to cause the expression of parvalbumin in the cultures.

Two distinct phases and mechanisms of axonal growth shown by primary vestibular fibres in the brain, demonstrated by parvalbumin immunohistochemistry

Antibodies to parvalbumin label intensely a small number of non-overlapping fibre systems in embryonic rat brain. All are in hindbrain--the oculomotor and trochlear motor fibres, the acoustic and vestibular fibres of the VIIIth nerve, and an unidentified group of fibres which ascend under the dorsal surface in caudal medulla. Of these, the vestibular fibres are the first to acquire parvalbumin immunoreactivity, and we have used this property to follow the growth of their axons in the brain. This occurs in two phases. In the first, occurring at embryonic days 12-14, the axons grow in small groups or fascicles under the pial surface to their most distant terminal zones rostrally in the cerebellum and caudally in the descending vestibular nuclei. This growth is directed towards the two sites where germinal neuroepithelium is expanding over the medullary velum in forming the cerebellum and lateral recess of the IVth ventricle. In a second stage, commencing at E15, individual collaterals branch from these fascicles to arborize amongst their presumptive synaptic targets (cells of the vestibular nuclei and vestibulocerebellum) located in the sub-ventricular and ventricular layers. In this phase the axons follow a radial route, at right angles to their original subpial course, possibly by growing along radial glial processes. The target cells then migrate to their final position with the vestibular axons maintaining contact with them. The vestibular fibres are the first axons to enter the cerebellum, but from E15 onwards their fascicles are joined by increasing numbers of non-vestibular fibres following the same course. These other axons, and the movement of cells to form the deep cerebellar nuclei, separate the fascicles of vestibular fibres so that their course into the cerebellum becomes very diffuse. Thus this single set of axons grow, not only in two distinct phases, but also follow distinctly different substrates for growth in each. Furthermore, they then appear to act as pioneer fibres guiding the entry or egress of later-developing axons to or from the cerebellum.

Monoclonal antibodies directed against the calcium binding protein parvalbumin

We have produced twelve monoclonal antibodies (McAB) against carp-II parvalbumin. Three of them, designated 235, 239, 267 recognize determinants conserved in fish, chicken, mouse, rat, monkey and human parvalbumin. We show their use in the qualitative detection of parvalbumin (PV) by immunohistochemistry, in the quantitation of parvalbumin by radioimmunoassay and in the detection of parvalbumin on immunoblots.

Analysis of the Ca2+-binding parvalbumin in rat skeletal muscles of different thyroid states

The Ca2+-binding parvalbumin (PV) is possibly involved in the relaxation of fast-twitch muscle fibers and believed to be a marker for early muscular disturbances. The muscular content of parvalbumin has been shown to change with alterations of the relaxation speed that follow an experimentally changed nervous input. In hypo- and hyperthyroidism isometric twitch contraction and half-relaxation times are also altered, namely increased in hypothyroidism and decreased in hyperthyroidism. These changes are largely paralleled by modifications in the fiber type composition. Therefore we investigated the distribution and concentration of parvalbumin in extensor digitorum longus, soleus, and gastrocnemius muscles of rats by immunohistochemical and biochemical methods. The combined results of both procedures showed that parvalbumin distribution and concentration were largely unaffected in all thyroid states. This suggests that the expression of parvalbumin is neuronally controlled and not by thyroid hormones. Additionally our findings support the view that the changes in physiologic properties and fiber type composition are generated by a direct action of thyroid hormone on muscle fibers, and not via their nervous input.

Developmental and functional studies of parvalbumin and calbindin D28K in hypothalamic neurons grown in serum-free medium

The Ca2+-binding proteins parvalbumin (Mr = 12K) and calbindin D28K [previously designated vitamin D-dependent Ca2+-binding protein (Mr = 28K)] are neuronal markers, but their functional roles in mammalian brain are unknown. The expression of these two proteins was studied by immunocytochemical methods in serum-free cultures of hypothalamic cells from 16-day-old fetal mice. Parvalbumin is first detected in all immature neurons, but during differentiation, the number of parvalbumin-immunoreactive neurons greatly declines to a level reminiscent of that observed in vivo, where only a subpopulation of neurons stains for parvalbumin. In contrast, calbindin D28K was expressed throughout the period investigated only in a distinct subpopulation of neurons. Depolarization of fully differentiated hypothalamic neurons in culture resulted in a dramatic decrease of parvalbumin immunoreactivity but not of calbindin D28K immunoreactivity. The parvalbumin staining was restored on repolarization. Because the anti-parvalbumin serum seems to recognize only the metal-bound form of parvalbumin, the loss of immunoreactivity may signal a release of Ca2+ from intracellular parvalbumin during depolarization of the cells. We suggest that parvalbumin might be involved in Ca2+-dependent processes associated with neurotransmitter release.

Purification and characterization of the 27,000 Da calcium-binding protein of bovine brain

A Ca2+-binding protein named CAB-27 was purified from bovine brain 100,000 g supernatant. The protein has a molecular mass of 27,000 Da as determined by SDS/polyacrylamide-gel electrophoresis and 35,500 Da by sedimentation-coefficient and Stokes-radius analysis. The protein contains about 26% Glx and Asx and 13% basic residues. The acidic nature of the molecule is confirmed by its pI of 4.80. In the presence of 3 mM-MgCl2 and 150 mM-KCl, CAB-27 binds 2.0 mol of Ca2+/mol of protein, with an apparent Kd of 0.2 microM. Ca2+-binding is unaffected by prior incubation of the protein at 80 degrees C for 2 min. Brain contains about 130 mg of CAB-27/kg. Immunoblotting identified CAB-27 in several bovine tissues; it appears to be particularly rich in brain and kidney. In addition, CAB-27 is identified as an inhibitor of bovine pancreas phospholipase A2 in vitro. The inhibitory activity of CAB-27 was 20-fold less potent than lipocortin. On the basis of the Ca2+-binding properties, intracellular concentration and tissue distribution of this protein, we suggest that CAB-27 may be an important intracellular Ca2+ receptor.

Calcium-binding proteins in rat skin

Skin Ca2+-binding protein (SCaBP) was reported to be distinct from the Ca2+-binding parvalbumin (PV), however, more recently its amino acid sequence was shown to be identical to PV. We purified a protein (Mr 12,000; pI4.5) from isolated epidermis (free of other cell layers) of adult rats and whole skin (containing no PV) of newborn rats. This protein is referred to as epidermal protein (EP-12), distinct from PV in its hydrophobicity, amino acid composition and immunological properties. Previously isolated SCaBP was shown to be a mixture of EP-12 and PV. The localization and possible functions of EP-12 and of PV in skin of adult and newborn rat are discussed.

Lanthanide-binding properties of rat oncomodulin

Oncomodulin, the parvalbumin-like calcium-binding protein frequently expressed in tumor tissue, was isolated from Morris hepatoma 5123tc and studied using the luminescent lanthanide ions, Eu3+ and Tb3+. Titrations of the apoprotein - whether monitored by indirect excitation of bound Tb3+, by direct laser excitation of bound Eu3+, or by quenching of the intrinsic tyrosine fluorescence - all indicated the presence of two high-affinity binding sites for lanthanide ions, as in parvalbumin. Moreover, the appearance of the Eu3+ 7F0----5D0 excitation spectrum of Eu2-oncomodulin was found to be highly pH-dependent, as previously observed with parvalbumin. At pH 5.0, it consists of a single peak centered at 5796 A, having a linewidth of approximately 6 A. At higher pH values, this spectrum is replaced by a broader, more symmetric peak at 5782 A. Oncomodulin, however, was found to differ from parvalbumin in at least one important respect: In contrast to the muscle-associated protein, the affinities of the CD site in oncomodulation for Tb3+ and Ca2+ were found to be rather similar, with KCa/KTb approximately equal to 11 +/- 2.

Parvalbumin in cat brain: isolation, characterization, and localization

Because of the increasing evidence that Ca2+-binding proteins have important regulating functions in nerve cells and because of the indications that there are species differences in the structures of these proteins, parvalbumin was purified from cat brain and muscle. Brain and muscle parvalbumins were found to be indistinguishable from each other in their biochemical and immunological properties. However, cat parvalbumin differs from all other mammalian parvalbumins by its apparently lower Mr on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 10-11K (compared to rat parvalbumin, 12K), and a lower pI of 4.6 (rat parvalbumin, 4.9), in the tryptic peptide maps, and in the immunological properties, indicating a distinct primary structure. With the purified parvalbumin as antigen, polyclonal antibodies were raised in rabbits and these were subsequently used for immunohistochemical localizations of parvalbumin in the cat brain. In the visual cortices of adult cats immunoreactive neurons were present throughout layers II and IV. In cerebellar cortex, Purkinje, basket, and stellate cells were immunoreactive. Comparison with staining patterns obtained with antiserum against rat parvalbumin revealed some cross-reactivity but confirmed the existence of species differences in the antigenic structure of rat and cat parvalbumin.

Parvalbumin in rat kidney. Purification and localization

The Ca2+-binding parvalbumin has been purified for the first time from rat kidney. Its biochemical and immunological properties were indistinguishable from the muscle counterpart. By immunohistochemical methods parvalbumin was localized in part of the distal tubule and proximal collecting duct, similar to the vitamin D-dependent Ca2+-binding protein, calbindin-28K. Parvalbumin was found to be independent of the vitamin D status of the animal since its concentration remained unchanged in kidney extracts of normal, rachitic and vitamin D-replete rats. Both proteins may be involved in the regulation of intracellular Ca2+ in kidney.

Ca2+-binding proteins from bovine brain including a potent inhibitor of protein kinase C

We have previously described the use of Ca2+-dependent hydrophobic-interaction chromatography to isolate the Ca2+ + phospholipid-dependent protein kinase (protein kinase C) and a novel heat-stable 21 000-Mr Ca2+-binding protein from bovine brain [Walsh, Valentine, Ngai, Carruthers & Hollenberg (1984) Biochem. J. 224, 117-127]. The procedure described for purification of the 21 000-Mr calciprotein to electrophoretic homogeneity has been modified to permit the large-scale isolation of this Ca2+-binding protein, enabling further structural and functional characterization. The 21 000-Mr calciprotein was shown by equilibrium dialysis to bind approx. 1 mol of Ca2+/mol, with apparent Kd approx. 1 microM. The modified large-scale purification procedure revealed three additional, previously unidentified, Ca2+-binding proteins of Mr 17 000, 18 400 and 26 000. The 17 000-Mr and 18 400-Mr Ca2+-binding proteins are heat-stable, whereas the 26 000-Mr Ca2+-binding protein is heat-labile. Use of the transblot/45CaCl2 overlay technique [Maruyama, Mikawa & Ebashi (1984) J. Biochem. (Tokyo) 95, 511-519] suggests that the 18 400-Mr and 21 000-Mr Ca2+-binding proteins are high-affinity Ca2+-binding proteins, whereas the 17 000-Mr Ca2+-binding protein has a relatively low affinity for Ca2+. Consistent with this observation, the 18 400-Mr and 21 000-Mr Ca2+-binding proteins exhibit a Ca2+-dependent mobility shift on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, whereas the 17 000-Mr Ca2+-binding protein does not. The amino acid compositions of the 17 000-Mr, 18 400-Mr and 21 000-Mr Ca2+-binding proteins show some similarities to each other and to calmodulin and other members of the calmodulin superfamily; however, they are clearly distinct and novel calciproteins. In functional terms, none of the 17 000-Mr, 18 400-Mr or 21 000-Mr Ca2+-binding proteins activates either cyclic nucleotide phosphodiesterase or myosin light-chain kinase, both calmodulin-activated enzymes. However, the 17 000-Mr Ca2+-binding protein is a potent inhibitor of protein kinase C. It may therefore serve to regulate the activity of this important enzyme at elevated cytosolic Ca2+ concentrations.