Large scale preparation and crystallization of neuron-specific enolase

Structural basis of the histidine-mediated vitamin D receptor agonistic and antagonistic mechanisms of (23S)-25-dehydro-1α-hydroxyvitamin D3-26,23-lactone

TEI-9647 antagonizes vitamin D receptor (VDR) mediated genomic actions of 1α,25(OH)2D3in human cells but is agonistic in rodent cells. The presence of Cys403, Cys410 or of both residues in the C-terminal region of human VDR (hVDR) results in antagonistic action of this compound. In the complexes of TEI-9647 with wild-type hVDR (hVDRwt) and H397F hVDR, TEI-9647 functions as an antagonist and forms a covalent adduct with hVDR according to MALDI–TOF MS. The crystal structures of complexes of TEI-9647 with rat VDR (rVDR), H305F hVDR and H305F/H397F hVDR showed that the agonistic activity of TEI-9647 is caused by a hydrogen-bond interaction with His397 or Phe397 located in helix 11. Both biological activity assays and the crystal structure of H305F hVDR complexed with TEI-9647 showed that the interaction between His305 and TEI-9647 is crucial for antagonist activity. This study indicates the following stepwise mechanism for TEI-9647 antagonism. Firstly, TEI-9647 forms hydrogen bonds to His305, which promote conformational changes in hVDR and draw Cys403 or Cys410 towards the ligand. This is followed by the formation of a 1,4-Michael addition adduct between the thiol (–SH) group of Cys403 or Cys410 and theexo-methylene group of TEI-9647.

Serum Antibodies to Retinal Antigens in Lung Cancer and Sarcoidosis

OBJECTIVE

Autoantibodies to various neuronal proteins frequently accompany lung cancer and their appearance may precede cancer symptoms. In this study we examined which retinal antigens (RAs) are recognized by sera of patients with lung cancer and whether the occurrence of serum antibodies to particular RAs is characteristic for cancer in comparison with a noncancer lung disease.

METHODS

Sera of 72 patients with non-small-cell lung cancer (NSCLC), 29 with small-cell lung cancer (SCLC), 27 with sarcoidosis (S), and sera of 32 healthy donors were examined in immunoblotting using retinal extracts and purified RAs as antigens.

RESULTS

69.0% of SCLC, 45.8% of NSCLC, and 44.4% of S sera displayed anti-RAs reactivity. Significantly less (p < 0.05; chi(2) test) percent of healthy control sera reacted with RAs. Lung cancer sera recognized mainly 46-, 56-, and 36-kD and to a smaller extent also 96-, 72-, 43-, and 26-kD proteins. Most of them were recognized with about 2-fold lower frequencies by S and control sera. Only lung cancer sera contained very high-titer antibodies to 46- and 26-kD RAs, identified as alpha-enolase and recoverin, respectively.

CONCLUSION

Antibodies to RAs occur more frequently and in higher titers in lung cancer (especially SCLC) than in sarcoidosis or control sera. Although antibodies to retinal alpha-enolase, recoverin and other RAs are present mainly or exclusively in lung cancer sera, none of them seems to be a specific marker of a particular disease.

Purification and properties of gammagamma-enolase from pig brain

Isoelectric focusing revealed three enolase isoforms in pig brain, which were designated as alphaalpha-(pI = 6.5), alphagamma- (pI = 5.6), and gammagamma-enolase (pI = 5.2). The pI of purified gammagamma-enolase was also 5.2. The gammagamma-enolase isoform of enolase was purified from pig brain by a purification protocol involving heating to 55 degrees C for 3 min, acetone precipitation, ammonium sulfate precipitation (40%-80%), DEAE Sephadex ion-exchange chromatography (pH 6.2), and Sephadex G200 gel filtration. The final specific activity was 82 units/mg protein. As with other vertebrate enolases, gammagamma-enolase from pig proved to be a dimer with a native mass of 85 kDa and a subunit mass of 45 kDa. The pH optimum for the reaction in the glycolytic direction is 7.2. The Km values for 2-PGA, PEP, and Mg2+ were determined to be 0.05, 0.25, and 0.50 mM, respectively, similar to Km values of other vertebrate enolases. The amino acid composition of pig gammagamma-enolase, as determined by amino acid analysis, shows strong similarity to the compositions of gammagamma-enolases from rat, human, and mouse, as determined from their amino acid sequences. Despite the differences seen with some residues, and considering the ways that the compositions were obtained, it is assumed that pig gammagamma-enolase is more similar than the composition data would indicate. Moreover, it is likely that the sequences of pig gammagamma-enolase and the other gammagamma-enolases are almost identical. Li+ proved to be a noncompetitive inhibitor with either 2-PGA or Mg2+ as the variable substrate. This enolase crystallized in the monoclinic space group P2, or P2(1). An Rsymm <5% was obtained for data between 50 and 3.65 A, but was a disappointing 30% for data between 3.65 and 3.10 A, indicating crystal disorder.

Cytological compartmentalization in the staggerer cerebellum, as revealed by calbindin immunohistochemistry for Purkinje cells

The staggerer mouse carries a deletion in a gene encoding the nuclear hormone receptor RORalpha, which leads to severe impairments in phenotypic differentiation of cerebellar Purkinje cells. We previously found parasagittal compartments in the mature staggerer cerebellum, as defined by different transcription levels of Purkinje cell-specific molecules including calbindin. In the present study, we developed a hightiter anti-calbindin antibody to examine morphological features of the staggerer Purkinje cells. Immunohistochemistry for calbindin revealed compartmentalized Purkinje cell populations with different cell sizes, alignments, cell densities, and dendritic arborization, as well as different immunoreactivities, corresponding to the "transcriptional" compartments. Based on these immunohistochemical and cytological characteristics, the rostral cerebellum was clearly subdivided into three to seven parasagittal zones (Zones I-VII). Purkinje cells in Zones I and III were associated with the strongest calbindin immunoreactivities and exhibited morphological features reminiscent of the wild-type cells, i.e., large flask-shaped cell bodies, monolayer alignment, and arborized dendrites. Purkinje cells in Zone V were also labeled strongly, but they were small in cell size, ectopic and possessed long unbranched dendrites. On the other hand, Purkinje cells in Zones II, IV, and VI were very low in calbindin immunoreactivity and marked by small cell size, ectopia, poorly-developed dendrites and low cell density. Considering that this unique cytological compartmentalization emerges as the result of RORalpha gene mutation, it is suggested that normal cytodifferentiation of Purkinje cells is governed by both RORalpha-dependent and -independent mechanisms, and further that the latter mechanism might exert unevenly along the mediolateral cerebellar axis.

A nuclear factor containing the leucine-rich repeats expressed in murine cerebellar neurons

A nuclear protein, termed leucine-rich acidic nuclear protein (LANP), has been isolated from among rat cerebellar proteins whose expression was transiently increased during an early stage of postnatal development. The amino acid sequence, deduced from its cDNA, showed that LANP contains 247 amino acids consisting of two distinct structural domains: the N-terminal domain characterized by "leucine-rich repeat," which is found in many eukaryotic proteins and which potentially functions in mediating protein-protein interactions, and the C-terminal domain characterized by a cluster of acidic amino acids with a putative nuclear localization signal. Immunohistochemical study using an antibody against LANP revealed that the protein is localized mainly in nuclei of Purkinje cells. In the rat cerebellum on postnatal day 7, LANP mRNA was expressed moderately in the external granule and Purkinje cells and weakly in the internal granule cells. The expression in these cells, especially in Purkinje cells, increased in the second postnatal week and thereafter decreased to an adult level. The structural characteristics, localization, and the stage- and cell type-specific expression suggest a potential role of LANP in a signal transduction pathway that directs differentiation of cerebellar neurons.

Covalent structure of bovine brain calreticulin

The covalent structure of bovine brain calreticulin, a major Ca(2+)-binding protein in the lumen of the endoplasmic reticulum, was determined by analysis of the purified protein. The protein consisted of 400 amino acids, with an N-linked oligosaccharide attached to the polypeptide chain. The polypeptide sequence determined was compatible with the sequence of calreticulin deduced from cDNA of different sources, with a number of differences presumably due to species-specific amino acid substitutions. The protein retained the C-terminal tetrapeptide, KDEL, involved in retention of proteins resident in the endoplasmic reticulum, whereas the N-terminal signal peptide predicted from the cDNA sequence had been removed in the purified protein. The bovine brain protein contained a high-mannose type of oligosaccharide attached to Asn162, which is typical of resident endoplasmic reticulum proteins. The carbohydrate moiety was heterogeneous and had the composition GlcNAc2Man4-9, of which GlcNAc2Man5 was the most abundant in the bovine brain preparation. Glycosylation of calreticulin, however, appeared to be a species-specific modification, as Asn162 is replaced by Asp in the sequences already determined for a number of species. Analysis of the purified protein also identified an intramolecular disulphide bridge between Cys120 and Cys146.

Automated two-dimensional liquid chromatographic system for mapping proteins in highly complex mixtures

An automated two-dimensional liquid chromatographic system was developed for systematic protein separations which could serve for analytical mapping and preparative separations of proteins. The system applies the principles of the column-switching technique, and consists of two different columns connected in tandem through an electrical column switching valve, two pumping systems to operate each column independently and a system controller to perform sequential chromatography on the two columns. A protein mixture is applied to the first-dimensional anion-exchange column and is separated by stepwise elution with an increasing sodium chloride concentration. The eluent is introduced directly to the second-dimensional reversed-phase column, and is further separated by gradient elution with an increasing acetonitrile concentration. The two elution stages are synchronized by a computer program. By this system, very complex protein mixtures such as crude cerebellar extracts were resolved reproducibly into ca. 200 peaks within 12 h. The method can be used for the total analysis of proteins in various tissues and cells without complicated premanupulation of samples, and allows the simultaneous analysis of a protein isolated by chromatography. The isolated protein is most suitable for use in the strategy of protein and gene sequence analysis.

Development of a radioimmunoassay for neurone specific enolase (NSE) and its application in the study of patients receiving intra hepatic arterial streptozotocin and floxuridine

A radioimmunoassay has been developed for neurone specific enolase (NSE) and used to measure serum NSE levels in patients with neuroendocrine and non-neuroendocrine tumours following intra hepatic arterial chemotherapy. Ten patients were studied, 7 receiving streptozotocin and floxuridine for neuroendocrine tumours and three receiving cisplatinum for non-neuroendocrine neoplasms. All ten patients had liver metastases. In patients with tumours of neuroendocrine origin, a significant increase in serum NSE was recorded within 24 h of therapy. Slight increases in serum NSE levels were also recorded in three patients with non neuroendocrine tumours. These increases may reflect lysis of neuroendocrine cells within the tumour. Raised levels in non-neuroendocrine tumour patients may reveal damage done to healthy neuronal and neuroendocrine cells during treatment. NSE may be a useful marker of the extent of cell death following chemotherapy.

Purification and properties of the age-related protein (ARPB) detected in human brain: comparison with human brain calmodulin

ARPB is an age-related protein in the human brain which is present in individuals younger than approximately 40 years of age, but disappears or becomes remarkably decreased in individuals above this age (Yasuda, T. and Kishi, K. (1985) Proc. Japan Acad. 61B, 273-276). ARPB was isolated from four different cerebra obtained from subjects 0, 15, 35 and 37 years old, and purified to an electrophoretically homogeneous state. Its molecular weight was estimated to be 17,000 and 36,000-38,000 by SDS-polyacrylamide gel electrophoresis and gel filtration, respectively. The amino acid composition of the purified ARPB, containing an excess of acidic amino acid residues (about 33%), proved to be very similar to that of calmodulin. ARPB exhibited some of the properties characteristic of calmodulin, such as a Ca2+-dependent mobility change upon electrophoresis, and activation of calmodulin-deficient phosphodiesterase activity in a Ca2+-dependent manner. However, it was possible to distinguish ARPB and human calmodulin with regard to their kinetic parameters for the activation reaction of phosphodiesterase activity, despite a close similarity in their reaction mode. It can be concluded that ARPB belongs to one of the calmodulin group proteins, although it remains unknown whether ARPB is identical to calmodulin.

Preparation and purification of gamma gamma enolase (neuron-specific enolase) using high performance anion exchange chromatography

A simple and rapid method, using only two chromatographic steps, is described for the purification and preparation of gamma gamma enolase isoenzymes from human and beef brain extracts. In the first step, a crude gamma gamma enolase was obtained by chromatography on Q-Sepharose Fast Flow column. The crude fraction was then purified by high performance anion exchange chromatography on a Mono-Q column. gamma gamma enolase obtained in this manner was shown to be homogeneous by two dimensional polyacrylamide gel electrophoresis and by high performance gel permeation chromatography. The yield of gamma gamma enolase by this method was 7-8 mg of pure enzyme per 100 g of brain.

Brain 14-3-3 protein is an activator protein that activates tryptophan 5-monooxygenase and tyrosine 3-monooxygenase in the presence of Ca2+,calmodulin-dependent protein kinase II

We have found that the 14-3-3 protein, an acidic neuronal protein, is substantially identical to the 'activator' protein [(1981) J. Biol. Chem. 256, 5404-5409] that activates tryptophan 5-monooxygenase and tyrosine 3-monooxygenase in the presence of Ca2+, calmodulin dependent protein kinase II. This finding is based on the remarkable similarity of both these proteins in physicochemical, biochemical and immunochemical properties, as well as on detection for the 14-3-3 protein of an activator activity towards tryptophan 5-monooxygenase. The result suggests that the 14-3-3 protein plays a role in the regulation of serotonin and noradrenaline biosynthesis in brain.

The unique action for bone metabolism of 1 alpha,25-(OH)2D3-26,23-lactone

[23 (S), 25 (R)]-1 alpha,25-Dihydroxyvitamin D3-26,23-lactone [( 23 (S),25 (R)]-1 alpha,25-(OH) 2D3-26,23-lactone) increased dose-dependently alkaline phosphatase activity in osteoblastic cells, clone MC3T3-E1, in medium containing 0.1% bovine serum albumin. The maximal stimulated enzyme activity per mg protein was 1.6-fold over that of control cultures at 250 pg/ml. The metabolite also increased collagen synthesis in a dose-related fashion. On the other hand, [23 (S),25 (R)]-1 alpha,25-(OH)2D3-26,23-lactone decreased slightly but significantly 45Ca mobilization, and blocked the resorptive action of 1 alpha,25-dihydroxyvitamin D3 but not that of parathyroid hormone, in mouse calvaria in organ culture. These results indicate that [23 (S),25 (R)]-1 alpha, 25-(OH)2D3-26,23-lactone stimulates the differentiation of osteoblasts and inhibits bone resorption in vitro.