Identification and characterization of sulfhydryl-containing proteolytic fragments involved in the Ca2+-induced conformational change of beef brain S-100

S-100 beta has a neuronal localisation in the rat hindbrain revealed by an antigen retrieval method

The localisation of S-100 in mammalian CNS neurons has been under debate for more than two decades. We address the question with two polyclonal and two new monoclonal antibodies. The specificity and the distribution in rat brain is based on an antigen retrieval method. We present evidence that aldehyde fixatives mask S-100 beta in neurons, and that the immunoreactivity is retrieved after trypsinisation. Neuronal S-100 beta is also detected in unfixed and ethanol fixed sections. The neuronal immunoreactivity is partly solubilised from unfixed tissue sections with 2.5 mM EDTA and is completely extracted with 2.5 mM EDTA and 1% Triton X-100. Most of the glial S-100 beta is washed out from unfixed tissue sections with saline. S-100 beta has distinct distribution in neurons of the hindbrain, i.e., the brainstem and cerebellum, but is not observed in the forebrain. One of the monoclonal antibodies immunostained neither neurons nor glia when it had been absorbed with S-100 crosslinked to nitrocellulose membranes. The distribution of neuronal S-100 beta differed from that of other neuronal calcium binding proteins, such as calbindin and parvalbumin. It was confined mainly to cholinergic neurons of the hindbrain. The presence of S-100 beta in distinct neuronal populations may indicate neurotrophic effects of S-100 beta. The notion is supported by the capability of S-100 to cause neurite outgrowth in vitro.

Structural and ion-binding properties of an S100b protein mixed disulfide: comparison with the reappraised native S100b protein properties

S100b protein, chemically modified by thioethanol groups (linked via disulfide bonds to two out of four Cys per dimer) was largely similar to reduced native S100b protein in its overall structure and differed only by small modifications extending, however, to the whole protein structure. Studies combining direct Ca2+ binding and associated conformational changes revealed that this chemical modification markedly increased the Ca2(+)-binding affinities (especially in the presence of physiological concentrations of K+ and Mg2+) and introduced a strong positive cooperativity. Different binding models are discussed and it emerges that in both proteins the Ca2(+)-binding sites are not equivalent and probably interact. Like the reduced protein, chemically modified S100b protein binds four Zn2+ ions in two classes of sites (of high and low affinities). Whereas the overall Zn2+ affinity was only slightly decreased, the binding sequence was probably reversed by the introduction of thioethanol groups. Moreover, in the presence of zinc, the Ca2+ affinities were higher and even identical, in both proteins.

Topical treatment of ulcerative proctitis with lidocaine

Rectal biopsy specimens from patients with ulcerative proctitis/proctosigmoiditis (UP/PS) were investigated immunocytochemically. In general, a changed mucosal innervation was demonstrated, with a marked increase in the number of nerve fibres and terminals with neuropeptide Y and tyrosine hydroxylase. In a few patients a hyperinnervation with VIPergic or SPergic nerves was seen. These findings indicate that hyperactive local nervous reflexes are of pathogenetic importance. To silence such activity, the diseased mucosa was treated with topically applied lidocaine. Such topical treatment with lidocaine gel in 21 consecutive patients with UP/PS for 3-8 weeks caused a rapid decrease of subjective and objective symptoms. During treatment mucosal integrity was restored, accompanied by depletion of OKT4 and OKT8 lymphocytes from the mucosa. However, the hyperinnervation pattern persisted during treatment.

Concomitant occurrence of an adrenal ganglioneuroma and a contralateral pheochromocytoma in a patient with von Recklinghausen's neurofibromatosis. An immunocytochemical study

This report presents concomitant occurrence of an adrenal ganglioneuroma and a contralateral pheochromocytoma in a patient with von Recklinghausen's disease. The patient's daughter also has cutaneous neurofibromatosis and an adrenal medullary tumor indicating that the observed "three component disease" may represent an inherited neurocristopathy. Immunocytochemically the ganglioneuroma showed a positive reaction with a tyrosinhydroxylase antiserum, but a negative reaction with a dopamine-beta-hydroxylase antiserum, suggesting the capacity of dopamine synthesis. Frequent ganglion cells were immunopositive against neuropeptide Y, but occasional ganglion cells were also positive against enkephalin and substance P. Adrenergic nerve fibers were abundant in the Schwann cell portion of the tumor, but peptide containing nerve cell processes were also demonstrated.

Conformational and hydrophobic properties of rat and bovine S-100 proteins

The binding of Ca2+ to rat or bovine S-100 proteins, in the absence of ligands, showed a dissociation constant (in 60 mM K+) of 0.5 to 1.0 mM as measured by the effects of Ca2+ on binding of S-100 to phenyl-Sepharose, reactivity of sulfhydryl groups, and difference spectra for PHE, TYR, and TRP residues. Binding of the ligands, "Stainsall" and chlorpromazine lowered the dissociation constant of S-100 for Ca2+ by 2- to 10-fold as measured by the same parameters. The conformational change, in response to Ca2+ binding, probably occurs by exposure to solvent of the hydrophobic region of alpha and beta subunits of S-100 at residue positions 74-93.

Fluorescence studies on the Ca2+ and Zn2+ binding properties of the alpha-subunit of bovine brain S-100a protein

The single cysteine on the alpha-subunit of bovine brain S-100a protein has been modified with the thiol specific probe, Acrylodan. When the labelled apoprotein was excited at 380 nm the fluorescence emission maximum was centered at 484 +/- 2 nm, suggesting that the probe is in a fairly hydrophobic environment. Addition of Ca2+ to the protein caused the emission maximum to undergo a red shift to 504 +/- 2 nm, implying that the fluorophore is now more exposed to the solvent. Zn2+, when added to the protein, induced only a small perturbation and the emission maximum shifted to 481 +/- 2 nm. Ca2+ was able to perturb the fluorophore in the presence of Zn2+. 2-p-Toluidinylnaphthalene-6-sulfonate (TNS)-labelled alpha-subunit when excited at 345 nm exhibited very little fluorescence in the absence of Ca2+. Addition of Ca2+ resulted in an increase in TNS fluorescence accompanied by a blue shift of the emission maximum to 445 +/- 1 nm indicating that the probe in the presence of Ca2+ moves to a hydrophobic domain. The fact that Ca2+ and Zn2+ can perturb the labelled sulfhydryl group in the presence of each other clearly demonstrates that the binding sites for the two metal ions must be different on the alpha-subunit as well as on the S-100a protein.

Anti-S-100 serum blocks long-term potentiation in the hippocampal slice

S-100 is a calcium-binding, glial protein which has been shown to be involved in behavioral learning and memory tasks. Long-term potentiation (LTP) in the hippocampus is a long-lasting enhancement of synaptic efficacy evoked by repetitive afferent stimulation. When anti-S-100 serum is applied by pressure ejection onto the stratum radiatum of area CA1 of the hippocampal slice, the amplitude of the extracellularly recorded population spike is not affected. However, repetitive stimulation of the afferents during S-100 application failed to produce LTP. At a distant site in the same slice, LTP occurs normally. Preimmune normal rabbit serum had no effect on the development of LTP. It appears that S-100 protein is involved in the establishment of LTP.

S-100 proteins

S-100 is a group of closely related, small, acidic Ca2+-binding proteins (S-100a0, S-100a and S-100b, which are alpha alpha, alpha beta, and beta beta in composition, respectively). S-100 is structurally related to calmodulin and other Ca2+-binding proteins. S-100 is abundant in the brain and is contained in well defined cell types of both neuroectodermal and non-neuroectodermal origin, as well as in their neoplastic counterparts. In the mammalian brain, S-100a and S-100b are confined to glial cells, while S-100a0 is neuronal in localization. Single S-100 isoforms bind Ca2+ with nearly the same affinity. K+ antagonizes the binding of Ca2+ to high affinity sites on S-100. S-100 binds Zn2+ with high affinity. S-100 is found in a soluble and a membrane-bound form and has the ability to interact with artificial and natural membranes. S-100 has no enzymatic activity. S-100 has been involved in several activities including memory processes, regulation of diffusion of monovalent cations across membranes, modulation of the physical state of membranes, regulation of the phosphorylation of several proteins, control of the assembly-disassembly of microtubules. Some of these effects are strictly Ca2+-dependent, while other are not. S-100 is being secreted or released to the extracellular space. In some cases, this event is hormonally regulated. Several S-100 binding proteins are being described.

Immunohistochemical co-localization of S-100b and the glial fibrillary acidic protein in rat brain

A rabbit antiserum against purified bovine brain S-100b protein was produced and characterized by immunoassay and immunoblot analysis of electrophoretically resolved soluble brain proteins. Fluorescent immunohistochemistry was conducted in order to determine the cellular localization of the S-100b immunoreactivity. Double immunohistofluorescent experiments on adult rat brain tissue sections with the rabbit antiserum to S-100b and a rat monoclonal antibody to the glial fibrillary acidic protein resulted in immunolabelling of the same cells. This finding determines a strict astroglial localization of the S-100b immunoreactivity. In addition, the immunolabelling of astrocyte perikarya and processes by the S-100b immunohistochemistry is consistent with a cytoplasmic location of S-100b. In contrast, the glial fibrillary acidic protein immunohistochemistry predominantly labeled the fine fibrillary processes of the cells. The present report suggests that S-100b immunohistochemistry is of use for the specific identification and morphological description of astrocytes in the rat brain.

S-100 protein-induced changes in the physical state of synaptosomal particulate fractions as monitored by spin labels

This report documents changes in the physical state of synaptosomal particulate fractions (SYN) upon binding of S-100 protein, as monitored by spin labels. Studies were conducted on SYN labeled with either 5-doxylstearic acid or 16-doxylstearic acid, which probe the polar region and the hydrophobic core of the lipid bilayer, respectively. S-100 perturbs to some extent both the polar surface and the hydrophobic core of SYN in a time- and temperature-dependent manner. Ca2+ is essential for S-100 to perturb the membranes. K+ almost completely inhibits the S-100 perturbing effect if present in the incubation medium, but fails to reverse the S-100-induced changes if added after S-100 has interacted with SYN. At room temperature and below, the overall S-100 effect registered after about 30 min of association of the protein with SYN is an increase in the fluidity of both the surface and the interior of the membranes. Spectra registered at intervals at room temperature indicate that the S-100 perturbing effect on the membrane surface is practically monophasic, consisting of an increase in fluidity, while that on the membrane interior is multiphasic, consisting of a decrease in fluidity during the first 10 min of association, followed by an increase in fluidity during the subsequent 20 min and a return to starting values during the second 30 min of association. Around 37 degrees C, on the contrary, a decrease in fluidity is registered in both regions. The data suggest that S-100 induces a spatial rearrangement of membrane components (proteins) involved in the specific binding and/or partially penetrates into the lipid bilayer.

Differentiation markers (S-100, GFAP, NSE and D2) in fetal rat brain cells during malignant transformation in cell culture

Malignant cell lines obtained by ethylnitrosourea (EtNU)-induced transformation of fetal rat brain cells in culture express protein markers of different types of neural cells. These are the nervous system-characteristic S-100 protein; glial fibrillary acidic protein (GFAP); neuron-specific-enolase (NSE), and the D2-cell adhesion molecule. S-100 protein was absent in fetal brain cells in culture, but gradually appeared in the later stages of malignant transformation and further increased at onset of rapid growth of atypical cells (stage IV). GFAP and D2 were weakly expressed in primary fetal brain cells and did not change throughout malignant transformation. NSE was present in both normal and carcinogen-treated fetal brain cells, and increased at later stages of malignant transformation. From stage III (40-100 days) some cultures were strongly positive and some negative, and the same was seen in the resulting tumorigenic cells about 100 days later. In conclusion the stepwise process of malignant transformation of brain cells in culture ended with a stable phenotype of cells capable of expressing varying types of differentiation markers. The presence of these markers in rat brain cells undergoing malignant transformation may indicate that EtNU given at 18th days of gestation is acting on multipotent neuroectodermal cells.

Reaction detector system for the simultaneous monitoring of primary amino groups and sulfhydryl groups in peptides eluted by high-performance liquid chromatography

A reaction detector system is described which can be used for simultaneous analysis of primary amino groups and sulfhydryl groups in peptides separated by high-performance liquid chromatography. By use of an automatic split valve system, well-defined portions of the effluent are diverted alternately into one of the two reaction detectors, based on the ninhydrin and Ellman assay, respectively. In the latter case the dithioerythritol included in the elution buffers for thiol preservation is eliminated with arsenite. For selective recovery of eluted peptides the amino/thiol group analyser can easily be converted into a high-yield monitoring system compatible with volatile, UV-opaque gradient buffers. In this version an automatic sample valve is used for the thiol assay, removing picomole amounts of material from the effluent destined for collection. In preparative applications there is a progressive net gain in sensitivity with increasing proportion of collected material. Under conditions of optimum recovery ca. 90% of the material could be recovered at a total consumption in the two detectors of less than 100 pmol. Experimental conditions are described which would allow for the additional identification of tryptophan, tyrosine and lysine-containing peptides. The monitoring system may also be used without modification for the assessment of key residues in polypeptides and proteins.

Binding of chlorpromazine to S-100 protein

Chlorpromazine (CPZ) induces in S-100 conformational changes resulting in the exposure of titratable SH groups of the protein to the solvent. This effect is even greater in the presence of Mg2+ +/- Ca2+. S-100 possesses binding sites for CPZ. The binding of CPZ to 3 microM S-100 is half-saturated by 0.18 microM CPZ in the presence of Mg2+ plus Ca2+ and by 0.24 microM CPZ in the presence of Mg2+ plus EGTA. The extent of the binding is greater in the presence of Ca2+ than in the presence of EGTA, especially at low CPZ concentrations.

Dermal nerve sheath myxoma. A light and electron microscopic, histochemical and immunohistochemical study

Two cases of dermal nerve sheath myxoma have been examined by light and electron microscopy, and by immunohistochemical and histochemical methods. The nomenclature of this tumor has been debated, and the histogenesis unsettled. Light microscopically, the lobulated myxoid tumors were generally composed of spindle-shaped and stellate tumor cells in an abundant matrix of mucosubstances. Ultrastructural features indicated an origin from the peripheral nerve sheath; among the pertinent findings were a single or duplicated external lamina investing the cells, desmosome-like junctions, cytoplasmic microfilaments and myelin figures, and interdigitating cytoplasmic processes. S-100 protein was demonstrated by means of the immunoperoxidase technique within both tumors, further supporting this origin. The histochemical analysis of the mucosubstance showed the presence of sulphated glucosaminoglycans. The name dermal nerve sheath myxoma, suggested by Harkin and Reed, is recommended.