Redox manipulation of DNA binding activity and BuGR epitope reactivity of the glucocorticoid receptor.

Treatment of the transformed glucocorticoid receptor with hydrogen peroxide promotes the formation of disulfide bonds and inhibits the ability of the receptor to bind to DNA (Tienrungroj, W., Meshinchi, S., Sanchez, E. R., Pratt, S. E., Grippo, J. F., Holmgren, A., and Pratt, W. B. (1987) J. Biol. Chem. 262, 6992-7000). It has not been determined whether the inhibition of DNA binding activity is due to disulfide bonds formed within the DNA binding domain or between the DNA binding domain and another region of the receptor. In this paper, we examined the ability of hydrogen peroxide to inactivate the DNA binding activity of the mouse glucocorticoid receptor. We show that inhibition of DNA binding activity caused by hydrogen peroxide can be accounted for entirely by the formation of disulfide bonds between cysteine residues lying within the 15-kDa tryptic fragment containing the DNA binding domain of the receptor. Reversal of the peroxide-induced inactivation of DNA binding activity requires both zinc and a thiol-disulfide exchange reagent, such as dithiothreitol. Peroxide also eliminates recognition of the intact receptor and the 15-kDa tryptic fragment by the BuGR monoclonal antibody, and the reactivity of the BuGR epitope is restored by reduction without a requirement for zinc. Pretreatment of the receptor with methyl methanethiosulfonate inhibits much of the peroxide-mediated inactivation of the BuGR epitope but pretreatment with N-ethylmaleimide does not. Similarly, DNA binding activity of the receptor is inhibited by methyl methanethiosulfonate but not by N-ethylmaleimide. These results are consistent with the proposal that peroxide promotes the formation of disulfide bonds between thiols that lie spatially close to one another in the 15-kDa tryptic fragment, resulting in rapid elimination of zinc. Restoration of the zinc finger structure restores DNA-binding activity but restoration of the BuGR epitope requires only reduction without restoration of the zinc fingers.     

Tuftsin,Thr-Lys-Pro-Arg

Summary Tuftsin, a natural occurring tetrapeptide, has been found to exhibit several biological activities connected with immune system function. Although little is known about tuftsin's biogenesis, much information has been gleaned about its structure-function relationships, which have shown that several features of the molecule are essential for expression of full biological activity. Furthermore, specific receptor sites for tuftsin have been found to exist exclusively on phagocytic cells. Research indicates that tuftsin binding to target cells effect intracellular calcium and cyclic nucleotide levels. Implication of these facts on tuftsin's mode of action are discussed.Basic peptidic segments resembling tuftsin are found in a variety of regulatory peptides. Questions are, therefore, raised as to the biospecificity and cross-reactivity of these sequences. Substance P, one such peptide, which binds with and activates tuftsin receptors, is described.In light of tuftsin's therapeutic potential, assays for its determination have been introduced. When applied to analyze human blood serum of normal as well as of various pathological origins, direct correlation was found between tuftsin levels and susceptibility to bacterial infections.     

In vivo effects of cadmium on rat liver glucocorticoid receptor functional properties.

1. Cadmium (Cd2+) administered in vivo induced a 40% reduction of rat liver glucocorticoid receptor (GR) capacity and inhibition of glucocorticoid-receptor complexes binding to mouse mammary tumor virus (MMTV) DNA fragment containing GR consensus sequence. 2. The effect of Cd2+ on the GR binding activity can be reversed with DTT, suggesting Cd2+ interaction with thiol groups. 3. Cd(2+)-related GR modification seems to be mediated by Cd2+ binding to cytoplasmic components included in the regulation of the receptor function, although the direct binding of the metal to the receptor thiols could not be ruled out.     

Mercury stimulates rat liver glucocorticoid receptor association with Hsp90 and Hsp70

The subject of the present study is the influence of mercury on association of rat liver glucocorticoid receptor (GR) with heat shock proteins Hsp90 and Hsp70. The glucocorticoid receptor heterocomplexes with Hsp90 and Hsp70 were immunopurified from the liver cytosol of rats administered with different doses of mercury. The amounts of co-immunopurified apo-receptor, Hsp90 and Hsp70 were then determined by quantitative Western blotting. The ratio between the amount of heat shock protein Hsp90 or Hsp70 and the amount of apo-receptor within immunopurified heterocomplexes was found to increase in response to mercury administration. On the other hand, the levels of Hsp90 and Hsp70 in hepatic cytosol remained unaltered. The finding that mercury stimulates association of the two heat shock proteins with the glucocorticoid receptor, rendering the cytosolic heat shock protein levels unchanged, suggests that mercury affects the mechanisms controlling the assembly of the receptor heterocomplexes.     

Dot-ELISA vs. PCR of fine needle aspirates of tuberculous lymphadenitis: a prospective study in India

OBJECTIVE: To evaluate an in-house dot-enzyme-linked immunosorbent assay (ELISA) for confirmation of clinically suspected cases of tuberculous lymphadenitis (TBLN). STUDY DESIGN: The study was performed at the postgraduate departments of microbiology and pathology of a tertiary-care teaching hospital in India. Suspected cases of TBLN were prospectively enrolled. Fine needle aspiration was done of enlarged lymph nodes in all patients, and 2 smears were prepared, 1 for acid-fast bacillus (AFB) demonstration and the other for cytologic examination. The remaining material was tested with in-house dot-ELISA and by IS6110 amplification with polymerase chain reaction (PCR), for diagnosis of TBLN. RESULTS: ELISA was more sensitive and detected 93.2% of cases. PCR and fine needle aspiration cytology (FNAC) detected 82.5% and 61.0% cases, respectively. AFB positivity was 33.1%. CONCLUSION: Application of dot-ELISA was more sensitive but less specific as compared to PCR. PCR, though expensive, should be used in problem cases because of its high specificity.     

Genetic analysis of X-chromosome neurodegenerative mutants of Drosophila melanogaster induced by ethyl methansulfonate and nitrosoethylurea

In a series of Drosophila mutants with changes in the brain structure, some characters (reduced life span, behavioral changes, and neuronal loss in various brain regions) resemble symptoms observed in human patients with neurodegenerative diseases. In addition, similar specific phenotypes shared by different species suggest that common mechanisms underlie degeneration of their nerve cell. This study reports the results of a genetic analysis of new X-chromosome mutants with neurodegenerative changes in brain structure, which were induced by chemical mutagenesis. According to complementation test, all mutants were divided into three complementation groups, in which the life span and dynamics of neurodegenerative changes were studied. The life span of Drosophila melanogaster flies was found to depend on the state of their nervous system.     

Novel naphthoquinonyl derivatives: Potential structural components for the synthesis of cytotoxic peptides

Summary Syntheses and physicochemical properties are described of several novel naphthoquinonyl amino acid derivatives, which are potential components in cytotoxic peptide conjugates. These compounds include N - and N -naphthoquinonyl derivatives of lysine as well as N-naphthoquinonyl-carboxylic derivatives. The former class of compounds can be employed as building blocks in a stepwise peptide synthesis, whereas the latter two are adequate for postpeptide chain-assembly modifications. The ability of the naphthoquinonyl derivatives to produce semiquinone radicals and hydroxyl radicals (OH), using chemical (i.e. NaBH₄) and enzymatic (i.e. NADPH-cytochrome P-450 reductase) routes, respectively, was evaluated employing electron spin resonance spectroscopy.