Effect of S-100 proteins and calmodulin on Ca2+-induced disassembly of brain microtubule proteins in vitro

Changes in microtubule stability in zebrafish (Danio rerio) embryos after glyphosate exposure

Glyphosate, the most commonly used pesticide worldwide, blocks aromatic amino acid biosynthetic pathways and inhibits growth in plants. Although the specific mode of action of glyphosate in animals remains unclear, adverse effects during embryonic development have been reported, including epiboly delays, morphological alterations, and changes in central nervous system development and cardiogenesis. In this study, we suggest a possible toxicity mechanism for this herbicide related to changes in microtubule stability, which could alter the distribution and dynamics of cytoskeleton components. Using zebrafish embryos to evaluate in vivo effects of glyphosate exposure (5, 10, and 50 μg/ml), we found significant reductions in the levels of acetylated α-tubulin (50 μg/ml) and in the polymeric tubulin percentage in zebrafish embryos that had been exposed to 10 and 50 μg/ml glyphosate, without any changes in either the expression patterns of α-tubulin or the stability of actin filaments. These results indicate that high concentrations of glyphosate were associated with reduced levels of acetylated α-tubulin and altered microtubule stability, which may explain some of the neurotoxic and cardiotoxic effects that have been attributed to this herbicide.

Direct interaction of metastasis-inducing S100P protein with tubulin causes enhanced cell migration without changes in cell adhesion

Overexpression of S100P promotes breast cancer metastasis in animals and elevated levels in primary breast cancers are associated with poor patient outcomes. S100P can differentially interact with nonmuscle myosin (NM) isoforms (IIA > IIC > IIB) leading to the redistribution of actomyosin filaments to enhance cell migration. Using COS-7 cells which do not naturally express NMIIA, S100P is now shown to interact directly with α,β-tubulin in vitro and in vivo with an equilibrium Kd of 2-3 × 10-7 M. The overexpressed S100P is located mainly in nuclei and microtubule organising centres (MTOC) and it significantly reduces their number, slows down tubulin polymerisation and enhances cell migration in S100P-induced COS-7 or HeLa cells. It fails, however, to significantly reduce cell adhesion, in contrast with NMIIA-containing S100P-inducible HeLa cells. When taxol is used to stabilise MTs or colchicine to dissociate MTs, S100P's stimulation of migration is abolished. Affinity-chromatography of tryptic digests of α and β-tubulin on S100P-bound beads identifies multiple S100P-binding sites consistent with S100P binding to all four half molecules in gel-overlay assays. When screened by NMR and ITC for interacting with S100P, four chemically synthesised peptides show interactions with low micromolar dissociation constants. The two highest affinity peptides significantly inhibit binding of S100P to α,β-tubulin and, when tagged for cellular entry, also inhibit S100P-induced reduction in tubulin polymerisation and S100P-enhancement of COS-7 or HeLa cell migration. A third peptide incapable of interacting with S100P also fails in this respect. Thus S100P can interact directly with two different cytoskeletal filaments to independently enhance cell migration, the most important step in the metastatic cascade.

Regulation of the calcium signal by calmodulin

Stimulus-response coupling mediated by calmodulin involves several steps: a transitory increase in calcium concentration from 0.1 to 10 microM, induced by external stimuli; interaction of calcium with calmodulin, accompanied by stepwise structural transitions; the coordinated interaction with and activation of the many calmodulin-regulated enzymes and proteins. The binding of calcium to calmodulin is a cooperative and selective process that is modulated by magnesium. At physiological ionic strength, and only in the presence of magnesium, a large difference is seen between the affinities of sites III and IV (0.09 X 10(6) M-1) and sites I and II (0.0007 X 10(6) M-1) for calcium. This difference, together with the positive cooperativity previously observed, explains the stepwise conformational changes induced by calcium. The interaction of calmodulin with its target proteins requires the integrity of different portions of the calmodulin molecule. Calmodulin-regulated enzymes can be divided into three classes according to their abilities to bind with and to be activated by calmodulin fragments: enzymes which are activated by the C-terminal fragment, such as the Ca2+-ATPase and phosphorylase kinase; enzymes which require both halves of the molecule, such as cyclic AMP phosphodiesterase and myosin light chain kinase; and enzymes whose interaction with calmodulin fragments is too weak to be detected by activation, such as calcineurin and the multiprotein kinase. Thus different enzymes may be activated by different calmodulin conformers and the stepwise changes exhibited by calmodulin at different calcium levels can be used to regulate different metabolic pathways.

S100B testing in pregnancy

Follow-up studies have shown that the vast majority of neurological abnormalities present during childhood can have a prenatal or perinatal origin. It is relevant, therefore, to investigate the timing of adverse insults in the search for measures of prevention. However, such knowledge is still incomplete and subject to debate. Until recently, clinical-laboratory assessment was based essentially on biochemical aspecific parameters, ultrasound and Doppler patterns, and the determination of blood pH and gases. However, the measurement of brain constituents may offer a direct indicator of cell damage in the nervous system. The S100B protein, a calcium-binding protein highly concentrated in the nervous system, appears to meet the criteria required of such a marker in prenatal and perinatal medicine for its reproducible, simple and sensible measurements. Results in high-risk pregnancies demonstrated that S100B concentration increased in amniotic fluid and in cord blood of fetuses with brain damage. In addition, S100B protein has been also usefully employed to monitor the effects of maternal-antenatal therapy, such as NO and glucocorticoid administration. It appears also to be relevant that a neurotrophic role has been hypothesized for the protein, which in fact exhibits in amniotic fluid, in cord blood and in placenta patterns of concentration related to the gestational age.

Immunohistochemical distribution of S-100 protein and subunits (S100-alpha and S100-beta) in the swamp-type water buffalo (Bubalus bubalis) testis

The distribution and localization of S-100 protein (S-100) and its subunits (S100-alpha and S100-beta) in the testis of swamp-type water buffalo were investigated using immunohistochemistry. S-100 was detected in the Sertoli cells in the convoluted seminiferous tubules, modified Sertoli cells lining the terminal segment of the seminiferous tubules and in the intratesticular excurrent ducts (straight tubules and rete testis). S100-beta showed the same distribution and localization with that of S-100. However, the cytoplasmic extension of the Sertoli cells in S100-beta staining showed less staining intensity compared with that of S-100. S100-alpha showed a positive staining only in the modified Sertoli cells of the terminal segment of the seminiferous tubule. Endothelial cells of blood vessels were also positive with the proteins while the Leydig and spermatogenic cells showed a negative reaction. The localization of S-100 in the testis of the water buffalo was in parallel with that of other artiodactyls which supports the hypothesis that this protein is a multifunctional protein. S100-beta in the Sertoli cells suggests that this protein is involved in establishing blood-testis barrier. Its presence in the modified Sertoli cells and in the epithelium of the excurrent ducts suggest secretory and absorptive function, respectively. Meanwhile, S100-alpha, which was detected only in the modified Sertoli cells, is involved in the secretory activity of these cells that are related to exocrine function.

Catecholase activity associated with copper-S100B

This study addresses the spectroscopic properties and reactivity associated with the copper-loaded form of S100B isolated from bovine brain. Copper(II)-S100B displays EPR features typical of a type II copper center and is shown here to exhibit catecholase activity, the two-electron oxidation of catechols. The steady-state kinetics associated with the oxidation of several catecholamines has been probed in order to further characterize this activity. The evidence provided indicates that the catecholase chemistry is copper initiated. Superoxide dismutase has no effect on the rates of catecholamine oxidation catalyzed by Cu-S100B, establishing that superoxide is not produced during this reaction, ruling out an autoxidative mechanism. Addition of catalase to the Cu-S100B reaction with catechols reduces the amount of oxygen consumed by 50%, demonstrating that peroxide is released during this reaction. The release of peroxide is mechanistically distinct from the type III dinuclear copper proteins, catechol oxidase and tyrosinase.

Frog p26olf, a molecule with two S100-like regions in a single peptide

An S100-like calcium-binding protein, p26olf, was originally isolated from the frog (Rana Catesbeiana) olfactory epithelium with four chromatographical steps. The primary structure of p26olf contains two S100-like regions aligned in tandem with four functional EF-hands. At 100 mM K(+), wild-type p26olf binds Ca(2+) with a Kd value of 22 microM and a Hill coefficient of 2.0. Each EF-hand seems to have different affinity for Ca(2+): it is high in EF-A and -B and low in EF-C and -D. In our Ca(2+)-binding model, the order of Ca(2+)-binding to p26olf is EF-B, EF-A, EF-C, and EF-D. Expression of mRNA of p26olf is detected in various frog tissues: it is high in the olfactory epithelium, lung, and spleen, moderate in brain, retina, heart, and kidney, and low in liver and muscle. Immunohistochemical studies revealed that p26olf is prominently localized in the cilia of both olfactory and lung respiratory epithelium and especially enriched in the distal segment of the olfactory cilia. Several proteins in the olfactory cilia bind to p26olf in the presence of Ca(2+), suggesting that they are possible target proteins of p26olf. One of these target proteins is immunologically identified as a beta-adrenergic receptor kinase-like protein. In the olfactory cilia, p26olf may have some roles in the olfactory transduction or adaptation through interaction with this beta-adrenergic receptor kinase-like protein.

S100B protein in biological fluids: a tool for perinatal medicine

The diagnosis of perinatal insults currently relies on adequate documentation of general medical and obstetric factors and on radiologic and laboratory assessments. The measurement of brain constituents such as S100B protein may offer an alternative and direct indicator of cell damage in the nervous system when clinical and radiologic assessments are still silent and has the additional advantage of providing a quantitative indicator of the extent of brain lesions. S100B protein has been measured by several immunoassays in biological fluids (i.e., cerebrospinal fluid, blood, amniotic fluid, and urine) from fetuses and newborns at high risk of perinatal brain damage. S100B protein in biological fluids increased at an early stage when standard monitoring procedures were still silent in the study populations that later developed brain damage. S100B concentration was also significantly correlated with the extent of brain lesions. S100B protein appears to satisfy the criteria for a marker for brain injuries in perinatal medicine: (a) simple to perform measurements with good reproducibility; (b) detection in a variety of biological fluids, possibly reducing perinatal stress related to testing; (c) possible use in longitudinal monitoring because of its 1-h half-life; and (d) well-established use as an early and quantitative marker of brain lesions/damage. Finally, because of the neurotrophic role putatively played by S100B, its measurement in biological fluids at pre-/perinatal ages makes it a candidate for the laboratory evaluation of brain maturation.

Serum S100 concentrations are not useful in predicting micrometastatic disease in cutaneous malignant melanoma

BACKGROUND

S100 protein is an acidic calcium binding protein that is expressed by melanoma cells. Elevated serum values of S100 have been described in metastatic disease and it has been suggested that it may be used as an adjunct to staging and monitoring of treatment. Micrometastatic disease in the sentinel lymph node can be demonstrated by sentinel node biopsy (SNB) and the sentinel node status is known to be the most important predictor of relapse.

OBJECTIVES

To determine whether serum S100 concentrations could predict the presence of micrometastatic disease.

METHODS

Thirty-one patients with primary cutaneous melanoma > 1 mm were recruited from referrals to the Melanoma clinic. All patients had serum S100 concentrations evaluated prior to undergoing SNB. Serum S100 concentrations were established using an immunoluminometric method. Sentinel nodes were identified using a dual technique with both radiolabelled colloid (residual from preoperative lymphoscintigraphy) and blue dye according to the MD Anderson Cancer Center protocol. Results Nine of these 31 patients had evidence of micrometastatic disease on SNB. The mean serum S100 concentration of those with positive SNBs was 0.027 microg L-1 compared with 0.045 microg x L(-1) in patients with negative SNBs (normal < 0.14 microg x L(-1)). No patient in the study demonstrated raised concentrations of serum S100.

CONCLUSIONS

We conclude that serum S100 concentrations do not predict the presence of micrometastatic melanoma in sentinel nodes in primary cutaneous melanoma.

S100beta interaction with tau is promoted by zinc and inhibited by hyperphosphorylation in Alzheimer's disease

The zinc-binding protein S100beta has been identified as an interacting partner with the microtubule-associated protein tau. Both proteins are individually affected in Alzheimer's disease (AD). S100beta, is overexpressed in the disease, whereas hyperphosphorylated tau constitutes the primary component of neurofibrillary tangles. In this study, we examine factors that modulate their binding and the potential role the complex may play in AD pathogenesis. Zinc was identified as a critical component in the binding process and a primary modulator of S100beta-associated cellular responses. Abnormally phosphorylated tau extracted from AD tissue displayed a dramatically reduced capacity to bind S100beta, which was restored by pretreatment with alkaline phosphatase. In differentiated SH-SY5Y cells, exogenous S100beta was internalized and colocalized with tau consistent with an intracellular association. This was enhanced by the addition of zinc and eliminated by divalent metal chelators. S100beta uptake was also accompanied by extensive neurite outgrowth that may be mediated by its interaction with tau. S100beta-tau binding may represent a key pathway for neurite development, possibly through S100beta modulation of tau phosphorylation and/or functional stabilization of microtubules and process formation. S100beta-tau interaction may be disrupted by hyperphosphorylation and/or imbalances in zinc metabolism, and this may contribute to the neurite dystrophy associated with AD.

Immunocontent and secretion of S100B in astrocyte cultures from different brain regions in relation to morphology

Primary astrocyte cultures prepared from neonatal hippocampus, cerebral cortex and cerebellum were morphologically distinct. Cells from hippocampus and cortex were almost entirely protoplasmic, whereas cerebellar astrocytes had many processes; in the absence of serum these differences were accentuated. We compared the immunocontent and secretion of the mitogenic protein S100B in these cultures. Immunocontent was 2.5 times higher in cerebellar astrocytes than in hippocampal or cortical astrocytes. Cells from all three regions secreted S100B under basal conditions, but the secretion rate was higher in cerebellar astrocytes. Secretion depended on protein synthesis and was increased by incubation with forskolin or lysophosphatidic acid in mechanisms which were additive. The stellate morphology induced by forskolin was reversed by lysophosphatidic acid in hippocampal but not in cerebellar cultures, suggesting that S100B secretion was not associated with a process-bearing phenotype of astrocytes.

A logical sequence search for S100B target proteins

The EF-hand calcium-binding protein S100B has been shown to interact in vitro in a calcium-sensitive manner with many substrates. These potential S100B target proteins have been screened for the preservation of a previously identified consensus sequence across species. The results were compared to known structural and in vitro properties of the proteins to rationalize choices for potential binding partners. Our approach uncovered four oligomeric proteins tubulin (alpha and beta), glial fibrillary acidic protein (GFAP), desmin, and vimentin that have conserved regions matching the consensus sequence. In the type III intermediate filament proteins (GFAP, vimentin, and desmin), this region corresponds to a portion of a coiled-coil (helix 2A), the structural element responsible for their assembly. In tubulin, the sequence matches correspond to regions of alpha and beta tubulin found at the alpha beta tubulin interface. In both cases, these consensus sequence matches provide a logical explanation for in vitro observations that S100B is able to inhibit oligomerization of these proteins.

Purification of the Ca2+-binding protein S100A1 from myocardium and recombinant Escherichia coli

S100A1 is a new regulatory protein of myocardial contractility that is differentially expressed in early and late stages of myocardial hypertrophy. In order to further investigate the multiple functions of S100A1 in various assay systems we developed a new strategy for isolating biologically active S100A1 protein. After EDTA extraction of myocardium or recombinant bacteria, S100A1 was purified by Octyl-Sepharose hydrophobic interaction chromatography and HiTrapQ anion-exchange chromatography yielding 1.4-2.0 mg/100 g wet tissue and 0.7-1.0 mg/100 ml bacterial culture. Native porcine as well as human recombinant S100A1 revealed biological activity in physiological and biochemical assays.

S-100 protein in peripheral blood: a marker for melanoma metastases: a prospective 2-center study of 570 patients with melanoma

BACKGROUND

S-100 protein, commonly used in the immunohistochemical diagnosis of malignant melanoma and melanoma metastases, has recently been introduced as a tumor marker in peripheral blood.

OBJECTIVE

This prospective, observational, 2-center study evaluates S-100 in peripheral blood of patients with melanoma as a marker for metastasis.

METHODS

With application of an immunoluminometric assay, S-100 levels in 1396 samples of 570 patients with melanoma and 53 control subjects were measured in a blinded manner.

RESULTS

The cut-off level for patients with melanoma without medical history of metastases versus patients with newly occurring lymph node, visceral, and/or brain metastases was 0.114 microg/L, with a sensitivity of 94% (95% confidence interval, 86.4%-98.5%) and a specificity of 91% (95% confidence interval, 87.7%-93.6%). False-negative results included patients with unknown primary melanoma and those with amelanotic melanoma metastases.

CONCLUSION

The data suggest that S-100 in the peripheral blood of patients with melanoma could serve as a marker indicating new melanoma metastases and could help to monitor the course of the disease.

The calcium-modulated proteins, S100A1 and S100B, as potential regulators of the dynamics of type III intermediate filaments

The Ca2+-modulated, dimeric proteins of the EF-hand (helix-loop-helix) type, S100A1 and S100B, that have been shown to inhibit microtubule (MT) protein assembly and to promote MT disassembly, interact with the type III intermediate filament (IF) subunits, desmin and glial fibrillary acidic protein (GFAP), with a stoichiometry of 2 mol of IF subunit/mol of S100A1 or S100B dimer and an affinity of 0.5-1.0 microM in the presence of a few micromolar concentrations of Ca2+. Binding of S100A1 and S100B results in inhibition of desmin and GFAP assemblies into IFs and stimulation of the disassembly of preformed desmin and GFAP IFs. S100A1 and S100B interact with a stretch of residues in the N-terminal (head) domain of desmin and GFAP, thereby blocking the head-to-tail process of IF elongation. The C-terminal extension of S100A1 (and, likely, S100B) represents a critical part of the site that recognizes desmin and GFAP. S100B is localized to IFs within cells, suggesting that it might have a role in remodeling IFs upon elevation of cytosolic Ca2+ concentration by avoiding excess IF assembly and/or promoting IF disassembly in vivo. S100A1, that is not localized to IFs, might also play a role in the regulation of IF dynamics by binding to and sequestering unassembled IF subunits. Together, these observations suggest that S100A1 and S100B may be regarded as Ca2+-dependent regulators of the state of assembly of two important elements of the cytoskeleton, IFs and MTs, and, potentially, of MT- and IF-based activities.

Functional roles of S100 proteins, calcium-binding proteins of the EF-hand type

A multigenic family of Ca2+-binding proteins of the EF-hand type known as S100 comprises 19 members that are differentially expressed in a large number of cell types. Members of this protein family have been implicated in the Ca2+-dependent (and, in some cases, Zn2+- or Cu2+-dependent) regulation of a variety of intracellular activities such as protein phosphorylation, enzyme activities, cell proliferation (including neoplastic transformation) and differentiation, the dynamics of cytoskeleton constituents, the structural organization of membranes, intracellular Ca2+ homeostasis, inflammation, and in protection from oxidative cell damage. Some S100 members are released or secreted into the extracellular space and exert trophic or toxic effects depending on their concentration, act as chemoattractants for leukocytes, modulate cell proliferation, or regulate macrophage activation. Structural data suggest that many S100 members exist within cells as dimers in which the two monomers are related by a two-fold axis of rotation and that Ca2+ binding induces in individual monomers the exposure of a binding surface with which S100 dimers are believed to interact with their target proteins. Thus, any S100 dimer is suggested to expose two binding surfaces on opposite sides, which renders homodimeric S100 proteins ideal for crossbridging two homologous or heterologous target proteins. Although in some cases different S100 proteins share their target proteins, in most cases a high degree of target specificity has been described, suggesting that individual S100 members might be implicated in the regulation of specific activities. On the other hand, the relatively large number of target proteins identified for a single S100 protein might depend on the specific role played by the individual regions that in an S100 molecule contribute to the formation of the binding surface. The pleiotropic roles played by S100 members, the identification of S100 target proteins, the analysis of functional correlates of S100-target protein interactions, and the elucidation of the three-dimensional structure of some S100 members have greatly increased the interest in S100 proteins and our knowledge of S100 protein biology in the last few years. S100 proteins probably are an example of calcium-modulated, regulatory proteins that intervene in the fine tuning of a relatively large number of specific intracellular and (in the case of some members) extracellular activities. Systems, including knock-out animal models, should be now used with the aim of defining the correspondence between the in vitro regulatory role(s) attributed to individual members of this protein family and the in vivo function(s) of each S100 protein.

Calcium-dependent interaction of S100B with the C-terminal domain of the tumor suppressor p53

In vitro, the S100B protein interacts with baculovirus recombinant p53 protein and protects p53 from thermal denaturation. This effect is isoform-specific and is not observed with S100A1, S100A6, or calmodulin. Using truncated p53 proteins in the N-terminal (p53(1-320)) and C-terminal (p53(73-393)) domains, we localized the S100B-binding region to the C-terminal region of p53. We have confirmed a calcium-dependent interaction of the S100B with a synthetic peptide corresponding to the C-terminal region of p53 (residues 319-393 in human p53) using plasmon resonance experiments on a BIAcore system. In the presence of calcium, the equilibrium affinity of the S100B for the C-terminal region of p53 immobilized on the sensor chip was 24 +/- 10 nM. To narrow down the region within p53 involved in S100B binding, two synthetic peptides, O1(357-381) (residues 357-381 in mouse p53) and YF-O2(320-346) (residues 320-346 in mouse p53), covering the C-terminal region of p53 were compared for their interaction with purified S100B. Only YF-O2 peptide interacts with S100B with high affinity. The YF-O2 motif is a critical determinant for the thermostability of p53 and also corresponds to a domain responsible for cytoplasmic sequestration of p53. Our results may explain the rescue of nuclear wild type p53 activities by S100B in fibroblast cell lines expressing the temperature-sensitive p53val135 mutant at the nonpermissive temperature.

Decreased levels of S-100 protein in non-ulcer interstitial cystitis

Interstitial cystitis (IC) is a chronic debilitating condition which mainly affects women. Accumulated evidence indicates that IC is a heterogeneous syndrome. As compared to classic IC, the non-ulcer type of IC appears to be different concerning symptomatic, endoscopical and histological findings, as well as in response to various forms of treatment. S-100 is a neural protein considered to be located primarily in the axons. To explore further the neurogenic nature of the disease, we compared bladder wall S-100 content in controls and in patients with classic and non-ulcer IC. We noticed a decrease in S-100 content in non-ulcer IC as compared to controls. This may be an expression of altered peripheral innervation in non-ulcer IC, which, in turn, may be an indication of primary neurogenic etiology. The difference in S-100 content between classic and non-ulcer IC supports the hypothesis that they represent separate entities, which may explain differences in response to various treatments.

Purification and molecular cloning of a novel calcium-binding protein, p26olf, in the frog olfactory epithelium

Olfactory adaptation requires the change of intracellular calcium concentration during stimuli. To contribute in the study of the molecular mechanism of calcium-dependent regulations in olfactory receptor cells, we isolated a novel 26-kDa Ca2+-binding protein named p26olf from the frog olfactory epithelium after four chromatographical steps. Based on the partial amino acid sequences of the proteolysed fragments of p26olf, we obtained a cDNA clone that encodes p26olf. The analysis of its amino acid sequence revealed that p26olf consists of two S-100-like regions aligned sequentially with a calculated molecular mass of 24,493. Northern blot analysis showed that p26olf is expressed in the frog olfactory epithelium and also in other tissues. Immunoreactivity against p26olf was detected in the cilia layer of the olfactory epithelium. These results suggest that p26olf is a dimeric form of S-100 proteins and is involved in the olfactory transduction or adaptation.

Calcium regulation of Ndr protein kinase mediated by S100 calcium-binding proteins

Ndr is a nuclear serine/threonine protein kinase that belongs to a subfamily of kinases identified as being critical for the regulation of cell division and cell morphology. The regulatory mechanisms that control Ndr activity have not been characterized previously. In this paper, we present evidence that Ndr is regulated by EF-hand calcium-binding proteins of the S100 family, in response to changes in the intracellular calcium concentration. In vitro, S100B binds directly to and activates Ndr in a Ca2+-dependent manner. Moreover, Ndr is recovered from cell lysates in anti-S100B immunoprecipitates. The region of Ndr responsible for interaction with Ca2+/S100B is a basic/hydrophobic motif within the N-terminal regulatory domain of Ndr, and activation of Ndr by Ca2+/S100B is inhibited by a synthetic peptide derived from this region. In cultured cells, Ndr is rapidly activated following treatment with Ca2+ ionophore, and this activation is dependent upon the identified Ca2+/S100B-binding domain. Finally, Ndr activity is inhibited by W-7 in melanoma cells overexpressing S100B, but is unaffected by W-7 in melanoma cells that lack S100B. These results suggest that Ndr is regulated at least in part by changes in the intracellular calcium concentration, through binding of S100 proteins to its N-terminal regulatory domain.

GFAP, S-100 and vimentin proteins in rat after cerebral post-ischemic reperfusion

In the present study astrocytes reactivity during cerebral post-ischemic reperfusion was evaluated immunocytochemically by using antibodies to vimentin, glial fibrillary acidic protein (GFAP) and S-100 protein. At the 7th day of post-ischemic reperfusion few GFAP-positive cells were observed in the hippocampus and cerebellum, the number of GFAP-positive cells increased slightly after 20 days of reperfusion. This poor GFAP-positivity may be due to the inhibition of GFAP polymerization by S-100; in fact, S-100 immuno-reactivity was already evident from the 7th day. Vimentin immuno-staining was evident both at the 7th and 20th day of reperfusion in microglial cells and in oligodendrocytes, suggesting that these cells are involved in the recovery of neurons following brain injury.

The S100B protein inhibits phosphorylation of GFAP and vimentin in a cytoskeletal fraction from immature rat hippocampus

The S100B protein belongs to a family of small Ca2+-binding proteins involved in several functions including cytoskeletal reorganization. The effect of S 100B on protein phosphorylation was investigated in a cytoskeletal fraction prepared from immature rat hippocampus. An inhibitory effect of 5 microM S100B on total protein phosphorylation, ranging from 25% to 40%, was observed in the presence of Ca2+ alone, Ca2+ plus calmodulin or Ca2+ plus cAMP. Analysis by two dimensional electrophoresis revealed a Ca2+/calmodulin-dependent and a Ca2+/cAMP-dependent inhibitory effect of S100B, ranging from 62% to 67% of control, on the phosphorylation of the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. The fact that S100B binds to the N-terminal domain of GFAP and that the two proteins are co-localized in astrocytes suggests a potential in vivo role for S100B in modulating the phosphorylation of intermediate filament proteins in glia.

Clinical and prognostic relevance of serum S-100 beta protein in malignant melanoma

To assess the clinical and prognostic relevance of serum S-100 beta in malignant melanoma serum levels of S-100 beta protein were measured in 84 patients with malignant melanoma. Using a cut-off value of 0.3 microgram/L the sensitivity was 0% (none of 36) in patients with stage II, 31% (four of 13) in patients with stage III and 69% (24 of 35) in patients with stage IV. In the reference group serum S-100 beta was below 0.3 microgram/L in all cases (specificity = 100%). A significant correlation existed between serum S-100 beta values and clinical staging as well as survival. In patients with distant metastases the serum concentration of S-100 beta protein correlated well with the number of affected organs. Serial measurement in these patients revealed that tumour progression was accompanied by rising S-100 beta values whereas declining values could only be revealed in one patient with a dramatic clinical response to therapy. Our results suggest that serum S-100 beta determination is a useful marker for the evaluation of prognosis in patients with metastatic malignant melanoma and should be included in the clinical staging.

Basic helix-loop-helix protein sequences determining differential inhibition by calmodulin and S-100 proteins

Basic helix-loop-helix (bHLH) proteins are a group of transcription factors that are involved in differentiation and numerous other cellular processes. The proteins include the widely expressed class A bHLH proteins (E proteins) and the tissue-specific class B proteins. Previous studies have shown that calmodulin can inhibit the DNA binding activity of certain E proteins but not their heterodimers with class B proteins. Here we show that calmodulin binds to the DNA-interacting basic sequence within the bHLH domain of E proteins. The strength of the binding of bHLH proteins to calmodulin correlates directly with the calmodulin sensitivity of their DNA binding. The basic sequence of MyoD, a class B protein, can also interact with calmodulin. This interaction, however, is blocked by MyoD sequences directly N-terminal of the basic sequence. We further demonstrate that S-100 proteins can interact with and differentially inhibit the DNA binding of bHLH proteins through interaction with the basic sequence. Both the binding to the basic sequence and the effect of the directly N-terminal sequence vary for different S-100 proteins and bHLH proteins. The results suggest the involvement of both calmodulin and S-100 proteins in the differential regulation of bHLH proteins.

S-100-positive glial cells are involved in the regeneration of the visual pathway of teleosts

Glial cells in the normal and regenerating visual pathways of Tinca tinca (Cyprinid, Teleost) were studied by labelling with anti-S-100 antibody. In normal fish, S-100-positive bipolar cells were found in the optic nerve, optic tract, and in the diencephalic visual pathways. After crushing the left optic nerve, the distribution and the number of S-100-immunoreactive cells were modified. In the injured nerve, 7 to 15 days after crushing no immunoreactive cell bodies were found in the crushed area, but a greater number of S-100-positive cells were found on both sides of the injured area. Sixty days after crushing, positive cells penetrating the crushed area were observed; the normal pattern was almost restored 200 days after crushing. In the diencephalon, 25 days after crushing, the number of S-100-positive cells increased remarkably and the most intense immunostaining of glial processes was observed 60 days after crushing. The density of S-100-labelled cells decreased after 4 months postcrushing. However, in the optic tectum no changes were observed. The increase of glial cells in the lesioned visual pathway suggests that they could play an important role in axonal regeneration after crushing.

Immunohistochemical evaluation of transglutaminase C in tumours of salivary glands

Transglutaminase C (TGase C), a family of Ca(2+)-dependent enzymes and an essential component in the cross-linking of peptide bonds, has been found to be a marker of epithelial differentiation with a possible role in cellular apoptosis, extracellular matrix stabilisation and Ca2+ binding, thereby having a potential role in tumour growth, differentiation and invasive behaviour. The expression of TGase C was evaluated in normal human salivary glands and their neoplastic lesions which included pleomorphic adenoma (n = 30), Warthin's tumour (n = 5), adenoid cystic carcinoma (n = 10), acinic cell carcinoma (n = 5), mucoepidermoid carcinoma (n = 5) and control tissue specimens of normal oral mucosa and squamous cell carcinoma, using polyclonal antibody, the specificity of which was determined by Western blotting, generated by immunising rabbits with purified transglutaminase. The TGase C was observed in the epithelial cells in the control tissue specimens examined. Pleiomorphic adenoma revealed reaction products in luminal tumour cells, the non-luminal or modified myoepithelial cells and their plasmacytoid variants, squamous metaplastic cells and chondroid cells. Adenoid cystic carcinomas had tumour cells in the luminal cells of tubular and cribriform structures and the acinic cell carcinoma had from low to moderate immunoreactivity in the tumour cell component and a diffuse immunoreactivity in the stroma for TGase C. Mucoepidermoid carcinoma showed no reaction products in the mucous-producing cells, while intermediate and epidermoid cells had immunoreactivity in the cell cytoplasm. As the presence of TGase C in salivary gland tumours was confined to those tumour cells which form the predominant histomorphology in each tumour subtype, it may be suggested that these enzymes may have a potential role in the regulation of cellular function in neoplastic salivary tissues affecting tumour growth, differentiation and neoplastic behaviour.

S-100 protein subunits in bovine oviduct epithelium: in situ distribution and changes during primary cell culture

Cultures of bovine oviduct epithelial cells are widely used in co-culture systems to improve the results of in vitro fertilization. The aim of the present study was to evaluate the suitability of S-100 protein as a differentiation marker for bovine oviduct epithelial cells in vitro. The distribution of S-100 alpha and S-100 beta was examined immunohistochemically in bovine oviduct epithelium in situ and in primary cell cultures derived from it. Three segments of the Fallopian tube (isthmus, ampulla and fimbriae) were compared and analysed during different stages of the oestrus cycle (luteal phase and follicular phase). Ciliated and non-ciliated cells of the epithelium reacted with anti-S-100 alpha, S-100a (alpha beta) and S-100 beta antibodies, except for isthmic non-ciliated cells, which did not bind anti-S-100 beta or anti-S-100a (alpha beta). In addition, basal cells never showed immunoreactivity for S-100. In confluent monolayers of cultured oviduct epithelial cells, disappearance of reactivity for S-100 paralleled morphological signs of dedifferentiation (loss of cilia, cytoplasmic vacuolization). Free-floating oviduct epithelial cells, in contrast, retained morphological differentiation and still expressed S-100 antigen even after seven days in vitro. The immunohistochemical findings were confirmed by polyacrylamide gel electrophoresis and Western blotting. The results indicate that the presence of S-100 is closely connected to morphological differentiation and to the specific functional condition of bovine oviduct epithelial cells.

Appearance of neuronal S-100 beta during development of the rat brain

In addition to being an astroglial protein, S-100 beta is localised in distinct populations of neurons in the adult rat hindbrain. We report, here, the expression of S-100 beta in both neurons and glia of the rat brain during development. Prenatally, S-100 beta immunoreactivity was confined to glial cells close to the germinal zone. After birth, S-100 beta positive glial cells were seen mainly in the brainstem and cerebellum, while only a few were detected in cerebral cortex and hippocampus. The number of S-100 beta containing glial cells increased steadily during the first 2 postnatal weeks after which the adult pattern was attained. No S-100 beta containing neurons were present prenatally. The first S-100 beta containing neurons were seen in the mesencephalic trigeminal nucleus at postnatal day 1 (P1), and in the motor trigeminal nucleus at P3. Neuronal S-100 beta immunoreactivity in other nuclei was mostly attained from the 10th to the 21st postnatal day. The neuronal S-100 beta immunoreactivity was first detected in the cell nuclei during development, then increased in the cytoplasm with ages. A nuclear staining in many immunoreactive neurons persisted until the adult. It usually took 1 to 2 weeks for neuronal S-100 beta to attain the adult staining pattern, i.e., heavy staining of the cytoplasm and processes, after its appearance. The forebrain never contained S-100 beta positive neurons. The S-100 beta is first expressed in glial cells, suggesting it is primarily of the glial origin. Coupled with neurotrophic effects of the protein, the time course of neuronal S-100 beta expression during the critical period of neuronal development implies that it may be involved in neuronal differentiation and maturation.

Immunohistochemistry in diagnostic dermatopathology

Immunopathology continues to be important in diagnostic dermatopathology. Immunopathology is an invaluable tool for assessing the tissue of origin or direction of differentiation of cells. In some cases this can result in a more precise diagnosis. This article reviews the role of immunopathology in determining the biologic behavior of hematolymphoid infiltrates. It explores the methodology of immunoperoxidase, discusses the most commonly used antibody reagents, and presents a series of diagnostic dilemmas in which immunopathology can be useful. In each case a strategy is established that maximizes the likelihood of making a definitive diagnosis.

Transient expression of S-100 by melanotropes of the rat pituitary intermediate lobe during development

S-100, an acidic calcium-binding protein, is co-localized with vimentin in glial-like cells in the adult rat pituitary intermediate lobe. S-100 and melanotrope markers were not co-localized in the adult. During development, S-100 and vimentin were not co-localized but appeared in cells with different morphological characteristics. S-100 was co-localized with POMC mRNA and beta-endorphin during prenatal time and the first three postnatal weeks. This was demonstrated by double-label immunohistochemistry, using combinations of antisera against S-100, vimentin and beta-endorphin, and in situ hybridization histochemistry for POMC mRNA combined with immunohistochemistry for S-100. In the second and third weeks of postnatal development, S-100 was observed in fewer melanotropes and more frequently in stellate cells, which also expressed vimentin. Thus, S-100 appeared to be transiently expressed in melanotropes during prenatal and early postnatal development. S-100 serves as a neurotrophic and glial maturation factor in the CNS. Since S-100 expression in melanotropes coincides with the onset of dopaminergic innervation and morphological changes in glial-like cells of the lobe, it could have similar functions in the rat pituitary intermediate lobe.

The S-100: a protein family in search of a function

The S-100 is a group of low molecular weight (10-12 kD) calcium-binding proteins highly conserved among vertebrates. It is present in different tissues as dimers of homologous or different subunits (alpha, beta). In the nervous system, the S-100 exists as a mixture composed of beta beta and alpha beta dimers with the monomer beta represented more often. Its intracellular localisation is mainly restricted to the glial cytoplasmic compartment with a small fraction bound to membranes. In this compartment the S-100 acts as a potent inhibitor of phosphorylation on several substrates including the synaptosomal C-Kinase and Tau, a microtubule-associated protein. The S-100 in particular conditions, after binding with specific membrane sites (Kd = 0.2 microM; Bmax = 4.5 nM), is able to modify the activity of adenylate cyclase, probably via G-proteins. In addition, the Ca2+ homeostasis is also modulated by S-100 via an increase of specific membrane conductance and/or Ca2+ release from intracellular stores. "In vitro" and "in vivo" experiments showed that lower (nM) concentrations of extracellular S-100 beta act on glial and neuronal cells as a growth-differentiating factor. On the other hand, higher concentrations of the protein induce apoptosis of some cells such as the sympathetic-like PC12 line. Finally, data obtained from physiological (development, ageing) or pathological (dementia associated with Down's syndrome, Alzheimer's disease) conditions showed that a relationship could be established between the S-100 levels and some aspects of the statii.

S100 protein in oral biology and pathology

The demonstration of S100 protein is used extensively for both research and diagnostic purposes in oral biology and pathology. This article reviews the structure and putative function of S100, technicalities of S100 immunohistochemistry, the cells of the oral and perioral tissues which express S100 and the possible significance of S100 expression in disease.

Differential distribution of immunoreactive S-100 protein in mammalian testis

The present study deals with the immunohistochemical localization of S-100 protein in the testes of seven mammalian species including rat, cat, dog, pig, sheep, cattle and horse. Significant differences are demonstrated in the cellular distribution and intensity of immunoreaction for the protein. In bull, ram, boar and cat testes S-100 protein was localized in the cytoplasm and nuclei of Sertoli cells. A particularly intense staining was seen in the modified Sertoli cells of the terminal tubular segment. With the exception of the cat and horse S-100 protein immunoreactivity was additionally found in epithelial cells of the straight testicular tubules and in the epithelial cells of the rete testis. Endothelial cells of capillaries, veins and lymphatic vessels are regularly S-100 immunoreactive in ruminants. Leydig cells were found to be strongly positive for S-100 protein in the cat and rat testes and to a lower degree in pig and horse testes. Finally a distinct immunostaining of peritubular cells was restricted to the testis of dogs and rats. The remarkable species-specific variations of immunoreactivity for S-100 protein in different cell types of the testis support the hypothesis that S-100 protein is multifunctional protein and may have a different function in testicular physiology.

Immunohistochemical detection of S-100 protein in human deciduous dental pulp

S-100 protein was investigated in the temporary dental pulp by the immunoperoxidase technique, using the avidin-biotin complex method. The results showed that there was a strong positive reaction in the Schwann cells ensheathing axons and nerve fibers. The other cells within the pulp were immuno-negative. S-100 protein and the results of the present study are discussed.

Calpain processing of brain microtubules from the Atlantic cod, Gadus morhua

Microtubules isolated from Atlantic cod (Gadus morhua) brains retained assembly competence and ultraculture, although treatment with rabbit calpain resulted in loss of MAPs. In addition, spirals and aberrant structures formed when calpain I was activated post assembly. No such effect was seen with calpain II. Soluble fractions from cod brain were found to contain proteolytic activity that could be blocked by exogenously added calpastatin. Calpain was also isolated from cod muscle tissue with 10 times less yield, compared to rabbit lung. On the basis of Ca(2+)-requirements for activation in the mM range, electrophoretic mobility, antigenicity and hydrophobicity, we conclude that the proteolytic activity was attributable to calpain II. There was no difference in effects of rabbit and cod calpain II on cod microtubule proteins, indicating that calpain is a conserved protein. Our results suggest that calpains might be involved in the Ca(2+)-dependent irreversible regulation of cod brain microtubules.

The S-100 protein causes an increase of intracellular calcium and death of PC12 cells

The S-100 protein-PC12 cell interaction has been studied as a model system of the possible physiological role played by S-100 protein in the nervous system. The data reported demonstrate that S-100 exerts a cytotoxic action which eventually leads to PC12 cell death, regardless of the cell cycle phase. The effect is specific for the S-100 isoforms, which are made up of two identical subunits and is abolished by a monoclonal antibody directed against the same isoforms. Other isoforms and/or calcium-binding proteins, such as troponin or calmodulin, do not induce the same effects. The action of S-100 on cell viability is not detectable in other cell lines of different embryological origin, such as 3T3, L1210, GH3. S-100 causes a rapid and considerable increase (two- to three-fold) of intracellular Ca2+ concentration in PC12 cells accompanied by cytostatic and cytotoxic action. It is postulated that this action also occurs in vivo, as part of the physiological action of this protein.

S-100 protein immunoreactivity in bovine testis

The present study deals with immunohistochemical localization of S-100 protein in the bovine testis. Immunoreactivity for the protein was seen in Sertoli cells of the seminiferous tubules and as a particularly intense staining in the terminal tubular segment (transitional region, middle portion, and terminal plug), which is mainly composed of modified Sertoli cells. Immunoreactivity was also found in epithelial cells of the straight testicular tubules and rete testis, and in the endothelium of capillaries, veins and lymphatic vessels. Although the functional significance of S-100 protein immunoreactivity in the Sertoli cells remains unclear, the present results suggest that it may be involved in the microtubule assembly-disassembly system. The specificity of the immunolabelling observed should enable the antigen and/or antibody to S-100 to be used as an investigative and diagnostic tool in the study of bovine Sertoli cell function.

Comparative immunohistochemical analysis between jaw myxoma and mesenchymal cells of tooth germ

The histogenesis of jaw myxoma is still debated. According to some authors it arises from the primitive mesenchymal components of developing teeth. In this study, we have studied the expression of S-100 protein and vimentin in dental follicle, dental papilla and periodontal ligament cells using monoclonal and polyclonal antibodies. Myxoma of the jaw expresses vimentin and S-100 protein. On the contrary, as compared to jaw myxoma, the normal developmental structures were immunonegative for S-100 protein but stained for vimentin. These results could indicate a difference in the derivation other than tooth mesenchyma.

Human odontoblasts contain S-100 protein-like immunoreactivity

S-100 protein is a group of three closely related isoforms (S-100ao, S-100a, and S-100b). This protein was first described as unique to the nervous system but it has also been identified subsequently in a variety of cell types of neuroectodermal (i.e., melanocytes, glial cells) and non-neuroectodermal origin (i.e., Langerhans cells, adipocytes, chondrocytes). In the present investigation the presence of S-100 protein was studied in human odontoblasts using a specific polyclonal antibody directed against S-100 protein in immunoperoxidase labelling experiments. The S-100 protein was detected in the cytoplasm of odontoblasts. This result suggests that S-100 protein can play a role in odontoblast functions.

Perspectives in S-100 protein biology. Review article

The S-100 protein family constitutes a subgroup of Ca(2+)-binding proteins of the EF-hand type comprising three dimeric isoforms, S-100a0, S-100a and S-100b, plus a number of structurally related proteins displaying 28-55% homology with S-100 subunits. S-100 protein was discovered in 1965; yet, its biological functions have not been fully elucidated. The present report will review the putative biological roles of S-100 protein. Both intracellular and extracellular roles have been proposed for S-100 protein. Within cells, S-100 protein has been reported to regulate protein phosphorylation, ATPase, adenylate cyclase, and aldolase activities and Ca(2+)-induced Ca2+ release. Also, cytoskeletal systems, namely microtubules and microfilaments have been reported to be regulated by the protein in the presence of Ca2+. Some molecular targets of S-100 protein within cells, have been identified. This is the case with microtubule proteins, caldesmon, and a brain aldolase. S-100 protein has been reported to be secreted; extracellular S-100 protein can stimulate neuronal differentiation, glial proliferation, and prolactin secretion. However, the mechanisms by which S-100 is secreted and stimulates the above processes are largely unknown. Future research should characterize these latter aspects of S-100 biology and find out the linkage between its intracellular effects and its extracellular activities.

Antisense inhibition of glial S100 beta production results in alterations in cell morphology, cytoskeletal organization, and cell proliferation

The phenotypic effects of selectively decreasing the levels of S100 beta in cultured glial cells were analyzed. Two separate antisense approaches were utilized for inhibition of S100 beta production: analysis of clonal isolates of rat C6 glioma cells containing an S100 beta antisense gene under the control of a dexamethasone-inducible promoter, and analysis of C6 cells treated with S100 beta antisense oligodeoxynucleotides. Both antisense methods resulted in a decrease in S100 beta levels in the cell, as measured by RIA. The inhibition of S100 beta production correlated with three alterations in cellular phenotype: (a) a flattened cell morphology; (b) a more organized microfilament network; and (c) a decrease in cell growth rate. The studies describe here provide direct evidence for an involvement of S100 beta in glial cell structure and function, and suggest potential in vivo roles for S100 beta in regulation of glial cell morphology, cytoskeletal organization, and cell proliferation.

S100 is preferentially distributed in myelin-forming Schwann cells

In order to elucidate the role of S100 protein in vivo we used postembedding electron microscopical immunocytochemistry with commercially available antibodies to S100, and secondary antibodies conjugated to colloidal gold to determine the distribution of S100 protein in the sciatic nerve and the cervical sympathetic trunk of the rat. We found that S100 immunoreactivity in Schwann cells was differentially distributed. The amount of S100 immunoreactivity in myelinated fibres appeared to correlate directly with the thickness of the myelin sheath formed by the Schwann cell. Unmyelinated fibres were identical to the small myelinated fibres in S100 immunoreactivity. Within the Schwann cells, the immunoreactivity was seen in the nucleus and in the perikaryal cytoplasm, as well as in the Schmidt-Lanterman clefts and in the paranodal loops at the node of Ranvier, but not in the myelin itself. Using these antibodies we did not see reproducible or convincing intra-axonal immunoreactivity in normal nerve. These results suggest that in Schwann cells S100 expression may be related to axon diameter and degree of myelination. Future studies of S100 expression in development or in response to injury may clarify the role of S100 in Schwann cell biology.