The hexosamine pathway has been implicated in the pathogenesis of diabetic complications. We determined first that hyperglycemia induced a decrease in glyceraldehyde-3-phosphate dehydrogenase activity in bovine aortic endothelial cells via increased production of mitochondrial superoxide and a concomitant 2.4-fold increase in hexosamine pathway activity. Both decreased glyceraldehyde-3-phosphate dehydrogenase activity and increased hexosamine pathway activity were prevented completely by an inhibitor of electron transport complex II (thenoyltrifluoroacetone), an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenylhydrazone), a superoxide dismutase mimetic [manganese (III) tetrakis(4-benzoic acid) porphyrin], overexpression of either uncoupling protein 1 or manganese superoxide dismutase, and azaserine, an inhibitor of the rate-limiting enzyme in the hexosamine pathway (glutamine:fructose-6-phosphate amidotransferase). Immunoprecipitation of Sp1 followed by Western blotting with antibodies to O-linked GlcNAc, phosphoserine, and phosphothreonine showed that hyperglycemia increased GlcNAc by 1.7-fold, decreased phosphoserine by 80%, and decreased phosphothreonine by 70%. The same inhibitors prevented all these changes. Hyperglycemia increased expression from a transforming growth factor-␤ 1 promoter luciferase reporter by 2-fold and increased expression from a (؊740 to ؉44) plasminogen activator inhibitor-1 promoter luciferase reporter gene by nearly 3-fold. Inhibition of mitochondrial superoxide production or the glucosamine pathway prevented all these changes. Hyperglycemia increased expression from an 85-bp truncated plasminogen activator inhibitor-1 (PAI-1) promoter luciferase reporter containing two Sp1 sites in a similar fashion (3.8-fold). In contrast, hyperglycemia had no effect when the two Sp1 sites were mutated. Thus, hyperglycemia-induced mitochondrial superoxide overproduction increases hexosamine synthesis and O-glycosylation of Sp1, which activates expression of genes that contribute to the pathogenesis of diabetic complications. D iabetic hyperglycemia causes a variety of pathologic changes in small vessels, arteries, and peripheral nerves (1, 2). Three major hypotheses about how hyperglycemia causes diabetic complications have generated extensive data as well as several clinical trials based on specific inhibitors of these pathways (3-6). These three pathways-activation of protein kinase C isoforms (7), increased formation of glucose-derived advanced glycation endproducts (3), and increased glucose flux through the aldose reductase pathway (8)-recently have been shown to be consequences of a single common mechanism, hyperglycemia-induced mitochondrial superoxide overproduction (1).A fourth hypothesis about how hyperglycemia causes diabetic complications has been formulated recently (9, 10), in which glucose is shunted into the hexosamine pathway. Inhibition of the rate-limiting enzyme in the conversion of glucose to glucosamine, glutamine:fructose-6-phosphate amidotransferase, bl...

soxR governs a superoxide response regulon that contains the genes for endonuclease IV, Mn2+-superoxide dismutase, and glucose 6-phosphate dehydrogenase. The soxR gene encodes a 17-kDa protein; some mutations of this gene cause constitutive overexpression of the regulon. Induction by paraquat (methyl viologen) requires both soxR and a new gene, soxS. soxS is adjacent to soxR, it encodes a 13-kDa protein, and it is required for paraquat resistance. These functions were revealed by studies in which the sequence of the 1.1-kb soxR-soxS region was determined, the 5' ends of the mRNAs were mapped, and complementation tests were performed with soxRS plasmids containing deletions of known sequence. The two genes are divergently transcribed, and the transcripts overlap. The soxS promoter is within the 85-nucleotide intergenic region, whereas the soxR promoter is within soxS. soxS mRNA increases after induction. Both protein products have possible DNA-binding (helix-turn-helix) domains. SoxR contains four cysteines (CX2CXCX5C) that might be part of a sensor region. SoxS shows 17 to 31 % homology to the C-terminal portions of members of the AraC family of positive regulators.

soxR and soxS are adjacent genes that govern a superoxide response regulon. Previous studies revealed that induction of the regulon is accompanied by increased transcription of soxS, which can activate the target genes. Therefore, induction may occur in two stages: the soxR-dependent activation of soxS, followed by the soxS-dependent induction of other genes. However, the requirement for soxR was unproven because the only existing soxR mutations either were of the regulon-constitutive type or also involved soxS. Therefore, we produced an insertion mutation that was shown by complementation to inactivate only soxR. In confirmation of the two-stage model, soxR was required for the induction by paraquat of the target genes studied (nfo, zwf, and sodA), for paraquat resistance, and for the 47- to 76-fold induction of soxS-lacZ gene fusions. Paraquat did not affect the expression of soxR-lacZ gene fusions. In a soxRS deletion mutant, the regulon was constitutively activated by a runaway soxS+ plasmid. However, a lower-copy-number plasmid failed to activate nfo, zwf, or sodA but did increase the paraquat resistance of a soxRS mutant. Therefore, there is a differential response of the regulon genes to soxS overproduction. A soxR regulon-constitutive mutation was suppressed by a soxR+ plasmid, suggesting a competition between native and activated forms of SoxR. It is proposed that to enhance the sensitivity of the response, the cell minimizes such potential competition by manufacturing only a small amount of this sensor protein, thereby necessitating signal amplification via induction of soxS.

No abstract

We consider some questions related to the signs of Hecke eigenvalues or Fourier coefficients of classical modular forms. One problem is to determine to what extent those signs, for suitable sets of primes, determine uniquely the modular form, and we give both individual and statistical results. The second problem, which has been considered by a number of authors, is to determine the size, in terms of the conductor and weight, of the first sign-change of Hecke eigenvalues. Here we improve significantly the recent estimate of Iwaniec, Kohnen and Sengupta.Comment: 23 pages, 1 figure; new version with new coauthor and strong improvements of two of the two main results

The development of complex multispecies communities such as biofilms is controlled by interbacterial communication systems. We have previously reported an intergeneric communication between two oral bacteria, Streptococcus cristatus and Porphyromonas gingivalis, that results in inhibition of fimA expression. Here, we demonstrate that a surface protein, arginine deiminase (ArcA), of S. cristatus serves as a signal that initiates intergeneric communication. An ArcA-deficient mutant of S. cristatus is unable to communicate with P. gingivalis. Furthermore, arginase activity is not essential for the communication, and ArcA retains the ability to repress expression of fimA in the presence of arginine deiminase inhibitors. These results present a novel mechanism by which intergeneric communication in dental biofilms is accomplished.

Two distinctive types of fimbriae have been identified in Porphyromonas gingivalis. In this report, we demonstrate that minor fimbriae are involved in P. gingivalis autoaggregation and colonization. A mutant with a deficiency in minor fimbriae can bind to a saliva-coated surface but does not form microcolonies as the wild-type strain does.

International audienceLet P denote the set of primes and {f (p)} p∈P be a sequence of independent Bernoulli random variables taking values ±1 with probability 1/2. Extending f by multiplicativity to a random multiplicative function f supported on the set of squarefree integers, we prove that, for any ε > 0, the estimate nx f (n) √ x (log log x) 3/2+ε holds almost surely—thus qualitatively matching the law of iterated logarithm, valid for independent variables. This improves on corresponding results by Wintner, Erd˝ os and Halász