Bcl-rambo, a novel Bcl-2 homologue that induces apoptosis via its unique C-terminal extension

The Bcl-2 family of proteins plays a central regulatory role in apoptosis. We have identified a novel, widely expressed Bcl-2 member which we have named Bcl-rambo. Bcl-rambo shows overall structural homology to the anti-apoptotic Bcl-2 members containing conserved Bcl-2 homology (BH) motifs 1, 2, 3, and 4. Unlike Bcl-2, however, the C-terminal membrane anchor region is preceded by a unique 250 amino acid insertion containing two tandem repeats. No interaction of Bcl-rambo with either anti-apoptotic (Bcl-2, Bcl-x(L), Bcl-w, A1, MCL-1, E1B-19K, and BHRF1) or pro-apoptotic (Bax, Bak, Bik, Bid, Bim, and Bad) members of the Bcl-2 family was observed. In mammalian cells, Bcl-rambo was localized to mitochondria, and its overexpression induces apoptosis that is specifically blocked by the caspase inhibitors, IAPs, whereas inhibitors controlling upstream events of either the 'death receptor' (FLIP, FADD-DN) or the 'mitochondrial' pro-apoptotic pathway (Bcl-x(L)) had no effect. Surprisingly, the Bcl-rambo cell death activity was induced by its membrane-anchored C-terminal domain and not by the Bcl-2 homology region. Thus, Bcl-rambo constitutes a novel type of pro-apoptotic Bcl-2 member that triggers cell death independently of its BH motifs.     

Skull osteology of Vipera walser (Squamata,Viperidae): Description,variability, ontogeny,and diagnostic characters in comparison to other Italian vipers

Vipera walser is the most recently recognized European viper. This rare species is endemic to a small area in the Piedmont Alps of Italy, but its closest relatives are found among the Caucasian viper species. In order to provide a starting point for a phylogenetic and biogeographic investigation based on osteology, and including fossils remains, we analyzed four specimens of V. walser and compared them with specimens of the four other Italian viper species. Based on these specimens, we improved the diagnosis of V. walser and provided a first evaluation of intraspecific variability and ontogenetic variation. The skull of V. walser is subject to significant variation, most likely related to ontogeny in some cases (i.e., development of the parietal crest, development of the basioccipital process, shape of the posterior margin of the parabasisphenoid, shape of the quadrate). Based on the studied material, it is possible to distinguish V. walser from the other Italian vipers by the shape of the occipital crest of the supraoccipital, which is posteriorly directed, whereas it is laterally directed in the other species. The osteological diagnosibility provides further support for the validity of V. walser as a distinct species from Vipera berus.     

Differential expression of NLRP3 among hematopoietic cells

Although the importance of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in health and disease is well appreciated, a precise characterization of NLRP3 expression is yet undetermined. To this purpose, we generated a knock-in mouse in which the Nlrp3 coding sequence was substituted for the GFP (enhanced GFP [egfp]) gene. In this way, the expression of eGFP is driven by the endogenous regulatory elements of the Nlrp3 gene. In this study, we show that eGFP expression indeed mirrors that of NLRP3. Interestingly, splenic neutrophils, macrophages, and, in particular, monocytes and conventional dendritic cells showed robust eGFP fluorescence, whereas lymphoid subsets, eosinophils, and plasmacytoid dendritic cells showed negligible eGFP levels. NLRP3 expression was highly inducible in macrophages, both by MyD88- and Trif-dependent pathways. In vivo, when mice were challenged with diverse inflammatory stimuli, differences in both the number of eGFP-expressing cells and fluorescence intensity were observed in the draining lymph node. Thus, NLRP3 levels at the site of adaptive response initiation are controlled by recruitment of NLRP3-expressing cells and by NLRP3 induction.     

Thiadiazoles as new inhibitors of diacylglycerol acyltransferase type 1

A novel class of DGAT1 inhibitors containing a thiadiazole core has been discovered. Chemical optimization lead to inhibitors of human DGAT1 with an appropriate ADME profile and that show in vivo activity in target tissues.     

PIDD Death-Domain Phosphorylation by ATM Controls Prodeath versus Prosurvival PIDDosome Signaling

Biochemical evidence implicates the death-domain (DD) protein PIDD as a molecular switch capable of?signaling cell survival or death in response to genotoxic stress. PIDD activity is determined by binding-partner selection at its DD: whereas recruitment of RIP1 triggers prosurvival NF-κB signaling, recruitment of RAIDD activates proapoptotic caspase-2 via PIDDosome formation. However, it remains unclear how interactor selection, and thus fate decision, is regulated at the PIDD platform. We show that the PIDDosome functions in the "Chk1-suppressed" apoptotic response to DNA damage, a conserved ATM/ATR-caspase-2 pathway antagonized by Chk1. In this pathway, ATM phosphorylates PIDD on Thr788 within the DD. This phosphorylation is necessary and sufficient for RAIDD binding and caspase-2 activation. Conversely, nonphosphorylatable PIDD fails to bind RAIDD or activate caspase-2, and engages prosurvival RIP1 instead. Thus, ATM phosphorylation of the PIDD DD enables a binary switch through which cells elect to survive or die upon DNA injury.     

The SPRY domain of Pyrin, mutated in familial Mediterranean fever patients, interacts with inflammasome components and inhibits proIL-1beta processing

The autoinflammatory disorders Muckle-Wells syndrome, familial cold urtecaria and chronic infantile neurological cutaneous and articular syndrome are associated with mutations in the NALP3 (Cryopyrin) gene, which is the central platform of the proinflammatory caspase-1 activating complex, named the inflammasome. In patients with another autoinflammatory disorder, familial Mediterranean fever (FMF), mutations in the SPRY domain of the Pyrin protein are frequently found. Recent evidence suggests that Pyrin associates with ASC, an inflammasome component, via its Pyrin domain, thereby halting the inflammatory response. This interaction, however, does not explain the effects of mutations of the SPRY domain found in FMF patients. Here we show that the Pyrin SPRY domain not only interacts with NALP3, but also with caspase-1 and its substrate pro-interleukin(IL)-1beta. Whereas a Pyrin knockdown results in increased caspase-1 activation and IL-1beta secretion, overexpression of the SPRY domain alone blocks these processes. Thus Pyrin binds to several inflammasome components thereby modulating their activity.     

Activation of the NALP3 inflammasome is triggered by low intracellular potassium concentration

Inflammasomes are Nod-like receptor(NLR)- and caspase-1-containing cytoplasmic multiprotein complexes, which upon their assembly, process and activate the proinflammatory cytokines interleukin (IL)-1beta and IL-18. The inflammasomes harboring the NLR members NALP1, NALP3 and IPAF have been best characterized. While the IPAF inflammasome is activated by bacterial flagellin, activation of the NALP3 inflammasome is triggered not only by several microbial components, but also by a plethora of danger-associated host molecules such as uric acid. How NALP3 senses these chemically unrelated activators is not known. Here, we provide evidence that activation of NALP3, but not of the IPAF inflammasome, is blocked by inhibiting K(+) efflux from cells. Low intracellular K(+) is also a requirement for NALP1 inflammasome activation by lethal toxin of Bacillus anthracis. In vitro, NALP inflammasome assembly and caspase-1 recruitment occurs spontaneously at K(+) concentrations below 90 mM, but is prevented at higher concentrations. Thus, low intracellular K(+) may be the least common trigger of NALP-inflammasome activation.