The roles of the classical and alternative nuclear factor-kappaB pathways: potential implications for autoimmunity and rheumatoid arthritis

Nuclear factor-κB (NF-κB) is an inducible transcription factor controlled by two principal signaling cascades, each activated by a set of signal ligands: the classical/canonical NF-κB activation pathway and the alternative/noncanonical pathway. The former pathway proceeds via phosphorylation and degradation of inhibitor of NF-κB (IκB) and leads most commonly to activation of the heterodimer RelA/NF-κB1(p50). The latter pathway proceeds via phosphorylation and proteolytic processing of NF-κB2 (p100) and leads to activation, most commonly, of the heterodimer RelB/NF-κB2 (p52). Both pathways play critical roles at multiple levels of the immune system in both health and disease, including the autoimmune inflammatory response. These roles include cell cycle progression, cell survival, adhesion, and inhibition of apoptosis. NF-κB is constitutively activated in many autoimmune diseases, including diabetes type 1, systemic lupus erythematosus, and rheumatoid arthritis (RA). In this review we survey recent developments in the involvement of the classical and alternative pathways of NF-κB activation in autoimmunity, focusing particularly on RA. We discuss the involvement of NF-κB in self-reactive T and B lymphocyte development, survival and proliferation, and the maintenance of chronic inflammation due to cytokines such as tumor necrosis factor-α, IL-1, IL-6, and IL-8. We discuss the roles played by IL-17 and T-helper-17 cells in the inflammatory process; in the activation, maturation, and proliferation of RA fibroblast-like synovial cells; and differentiation and activation of osteoclast bone-resorbing activity. The prospects of therapeutic intervention to block activation of the NF-κB signaling pathways in RA are also discussed

Security for Grid Services

Grid computing is concerned with the sharing and coordinated use of diverse resources in distributed "virtual organizations." The dynamic and multi-institutional nature of these environments introduces challenging security issues that demand new technical approaches. In particular, one must deal with diverse local mechanisms, support dynamic creation of services, and enable dynamic creation of trust domains. We describe how these issues are addressed in two generations of the Globus Toolkit. First, we review the Globus Toolkit version 2 (GT2) approach; then, we describe new approaches developed to support the Globus Toolkit version 3 (GT3) implementation of the Open Grid Services Architecture, an initiative that is recasting Grid concepts within a service oriented framework based on Web services. GT3's security implementation uses Web services security mechanisms for credential exchange and other purposes, and introduces a tight least-privilege model that avoids the need for any privileged network service.Comment: 10 pages; 4 figure

Pushing Open Government Through Social Media

E-government aims to enhance the interaction between citizens, business, and government. Recently, the term open government is increasingly used to emphasize the importance of co-creation in governmental issues. In this study, the social media activities of the municipalities of North Rhine-Westphalia, Germany, are investigated with regard to the topic “open government” as one pillar of e-government. The findings show that user interaction is mostly represented through likes and shares and rarely by comments. A topic detection of the posted content reveals that different terms are covered by the municipalities and shows that open government is getting more and more diverse in recent years. The number of posts is still increasing each year on the social media platforms Facebook and Twitter, but the topic of open government is still a peripheral phenomenon

Position of γ-Chain Carboxy-Terminal Regions in Fibrinogen/Fibrin Cross-Linking Mixtures

There are conflicting ideas regarding the location of the carboxyl-terminal regions of cross-linked γ-chain dimers in double-stranded fibrin fibrils. Some investigators believe that the chains are always oriented longitudinally along each fibril strand and traverse the contacting ends of abutting fibrin D domains (“DD-long” cross-linking). Other investigations have indicated instead that the chains are situated transversely between adjacent D domains in opposing fibril strands (transverse cross-linking). To distinguish between these two possibilities, the γ dimer composition of factor XIIIa-cross-linked fibrin/fibrinogen complexes that had been formed through noncovalent D/E interactions between fibrinogen D domains and fibrin E domains was examined. Two factor XIIIa-mediated cross-linking conditions were employed. In the first, fibrin/fibrinogen complexes were formed between 125I-labeled fibrinogen 2 (“peak 2” fibrinogen), each heterodimeric molecule containing one γA and one larger γ‘ chain, and nonlabeled fibrin 1 molecules (“peak 1” fibrin), each containing two γA chains. If DD-long cross-linking occurred, 125I-labeled γA−γA, γA−γ‘, and γ‘−γ‘dimers in a 1:2:1 ratio would result. Transverse cross-linking would yield a 1:1 mixture of 125I-labeled γA−γA and γA−γ‘ dimers, without any γ‘−γ‘ dimers. Autoradiographic analyses of reduced SDS−PAGE gels from protocol 1 revealed 125I-labeled γA−γA and γA−γ‘ dimers at a ratio of ∼1:1. No labeled γ‘−γ‘ dimers were detected. Protocol 2 used a converse mixture, 125I-fibrin 2 and nonlabeled fibrinogen 1. DD-long cross-linking of this mixture would yield only nonradioactive γA−γA dimers, whereas transverse cross-linking would yield a 1:1 mixture of 125I-labeled γA−γA and γA−γ‘ dimers. Autoradiographic analyses of this mixture yielded 125I-labeled γA−γA and γA−γ‘ dimers in a 1:1 ratio. These findings provide no evidence that longitudinal (DD-long) γ chain positioning occurs in cross-linked fibrin and indicate instead that most, if not all, γ-chain positioning in an assembled fibrin polymer is transverse

Fibrinogen Birmingham: A Heterozygous Dysfibrinogenemia (Aα 16 Arg → His) Containing Heterodimeric Molecules

Fibrinogen was isolated from the plasma of a 25-year-old female with a history of mild bleeding and several recent moderate to severe hemorrhagic episodes. Coagulability with thrombin approached 100% and varied directly with the time of incubation with the enzyme. High- performance liquid chromatography analysis of thrombin-induced fibrinopeptide release demonstrated retarded fibrinopeptide A (FPA) and fibrinopeptide B (FPB) release and the presence of an abnormal A peptide (FPA) amounting to 50% of the total. The same biochemical abnormalities were found in her asymptomatic father. Amino acid analysis and carboxypeptidase digestion of FPA demonstrated the substitution of His for Arg at A alpha 16. In contrast to the thrombin- and reptilase-sensitive Arg-Gly bond in the normal A alpha chain, the abnormal A alpha chain (A alpha) sequence is resistant to reptilase attack but is slowly cleaved by thrombin. To evaluate whether Birmingham A alpha and A alpha chains had been assembled nonselectively into heterodimeric (ie, 50% A alpha, A alpha) and homodimeric (ie, 25% A alpha, A alpha; 25% A alpha, A alpha) species, the clot and the clot liquor resulting from reptilase treatment of normal or Birmingham fibrinogen were separated, and each was then further incubated with thrombin to release remaining fibrinopeptides. Assuming that fibrinogen Birmingham contained heterodimeric molecules and that these and the normal molecules were completely incorporated into a reptilase clot, the expected coagulability would be 75%. In addition, subsequent thrombin treatment of the reptilase clot would release 50% of the total FPA and 75% of the total FPB present in the original sample. On the other hand, if only homodimeric fibrinogen species (50% A alpha, A alpha; 50% A alpha, A alpha) existed, the maximum reptilase coagulability would be 50%, and after thrombin treatment, 50% of the total FPB and no FPA would be recovered from the reptilase clot. We found the propositus\u27s fibrinogen to be 68% coagulable, and we recovered 45% of the FPA and 70% of the FPB from the reptilase clot. Essentially the same coagulability and distribution of fibrinopeptides was found in the reptilase clot from her father\u27s fibrinogen. We therefore conclude that fibrinogen Birmingham contains heterodimeric species (A alpha, A alpha) amounting to approximately 50% of the circulating fibrinogen molecules. The existence of heterodimers is consistent with a nonselective intracellular process of constituent chain assembly of dimeric plasma fibrinogen molecules

Identification and Characterization of the Thrombin Binding Sites on Fibrin

Thrombin binds to fibrin at two classes of non-substrate sites, one of high affinity and the other of low affinity. We investigated the location of these thrombin binding sites by assessing the binding of thrombin to fibrin lacking or containing γ′ chains, which are fibrinogen γ chain variants that contain a highly anionic carboxyl-terminal sequence. We found the high affinity thrombin binding site to be located exclusively in D domains on γ′ chains (Ka, 4.9 × 106−1; n, 1.05 per γ′ chain), whereas the low affinity thrombin binding site was in the fibrin E domain (Ka, 0.29 × 106−1; n, 1.69 per molecule). The amino-terminal β15-42 fibrin sequence is an important constituent of low affinity binding, since thrombin binding at this site is greatly diminished in fibrin molecules lacking this sequence. The tyrosine-sulfated, thrombin exosite-binding hirudin peptide, S-Hir53-64 (hirugen), inhibited both low and high affinity thrombin binding to fibrin (IC50 1.4 and 3.0 μ, respectively). The presence of the high affinity γ′ chain site on fibrinogen molecules did not inhibit fibrinogen conversion to fibrin as assessed by thrombin time measurements, and thrombin exosite binding to fibrin at either site did not inhibit its catalytic activity toward a small thrombin substrate, S-2238. We infer from these findings that there are two low affinity non-substrate thrombin binding sites, one in each half of the dimeric fibrin E domain, and that they may represent a residual aspect of thrombin binding and cleavage of its substrate fibrinogen. The high affinity thrombin binding site on γ′ chains is a constitutive feature of fibrin as well as fibrinogen

Plasma Factor XIII Binds Specifically to Fibrinogen Molecules Containing γ‘ Chains

The difference between peak 1 and peak 2 fibrinogen lies in their γ chains. Peak 1 molecules contain 2 γA chains; peak 2 molecules contain 1 γA and 1 γ‘ chain, the latter of which contains a 20 amino acid extension (γ‘ 408−427) replacing the carboxyl-terminal 4 amino acids of the γA chain (γA 408−411). While the existence of γ‘ chains in plasma fibrinogen molecules has been known for many years, their function remains unknown. When fibrinogen is purified from plasma, the factor XIII zymogen (A2B2) copurifies with it and is found only in the peak 2 fibrinogen when this fraction is separated from peak 1 fibrinogen by ion-exchange chromatography on DEAE-cellulose. Factor XIII alone applied to the same DEAE column elutes at a position between peak 1 and peak 2. When mixtures of peak 1 fibrinogen plus factor XIII or peak 2 fibrinogen plus factor XIII are applied to DEAE columns, the peak 1/factor XIII mixture elutes in two peaks, whereas the peak 2/factor XIII mixture elutes in the peak 2 fibrinogen position. Gel sieving on Superose 6 of peak 1/factor XIII mixtures results in two protein peaks, the first of which contains the fibrinogen. Most factor XIII activity elutes in the second peak with a small amount of activity emerging with the trailing end of the fibrinogen peak. Gel sieving of mixtures of peak 2 and factor XIII results in a single protein peak with all factor XIII activity emerging with the leading edge of the fibrinogen peak. The interaction between peak 2 fibrinogen and plasma factor XIII appears to be through binding to the B subunit of factor XIII since placental or platelet factor XIII (A2), which does not contain B subunits, elutes independently from peak 2 fibrinogen on DEAE-cellulose chromatography. The results indicate that peak 2 fibrinogen γ‘ chains have a physiologically significant affinity for the B subunits of plasma factor XIII and that through this interaction fibrinogen serves as a carrier for the plasma zymogen in circulating blood