Pathogen-Mediated Proteolysis of the Cell Death Regulator RIPK1 and the Host Defense Modulator RIPK2 in Human Aortic Endothelial Cells

Porphyromonas gingivalis is the primary etiologic agent of periodontal disease that is associated with other human chronic inflammatory diseases, including atherosclerosis. The ability of P. gingivalis to invade and persist within human aortic endothelial cells (HAEC) has been postulated to contribute to a low to moderate chronic state of inflammation, although how this is specifically achieved has not been well defined. In this study, we demonstrate that P. gingivalis infection of HAEC resulted in the rapid cleavage of receptor interacting protein 1 (RIPK1), a mediator of tumor necrosis factor (TNF) receptor-1 (TNF-R1)-induced cell activation or death, and RIPK2, a key mediator of both innate immune signaling and adaptive immunity. The cleavage of RIPK1 or RIPK2 was not observed in cells treated with apoptotic stimuli, or cells stimulated with agonists to TNF-R1, nucleotide oligomerization domain receptor 1(NOD1), NOD2, Toll-like receptor 2 (TLR2) or TLR4. P. gingivalis-induced cleavage of RIPK1 and RIPK2 was inhibited in the presence of a lysine-specific gingipain (Kgp) inhibitor. RIPK1 and RIPK2 cleavage was not observed in HAEC treated with an isogenic mutant deficient in the lysine-specific gingipain, confirming a role for Kgp in the cleavage of RIPK1 and RIPK2. Similar proteolysis of poly (ADP-ribose) polymerase (PARP) was observed. We also demonstrated direct proteolysis of RIPK2 by P. gingivalis in a cell-free system which was abrogated in the presence of a Kgp-specific protease inhibitor. Our studies thus reveal an important role for pathogen-mediated modification of cellular kinases as a potential strategy for bacterial persistence within target host cells, which is associated with low-grade chronic inflammation, a hallmark of pathogen-mediated chronic inflammatory disorders

TRIM27 Negatively Regulates NOD2 by Ubiquitination and Proteasomal Degradation

NOD2, the nucleotide-binding domain and leucine-rich repeat containing gene family (NLR) member 2 is involved in mediating antimicrobial responses. Dysfunctional NOD2 activity can lead to severe inflammatory disorders, but the regulation of NOD2 is still poorly understood. Recently, proteins of the tripartite motif (TRIM) protein family have emerged as regulators of innate immune responses by acting as E3 ubiquitin ligases. We identified TRIM27 as a new specific binding partner for NOD2. We show that NOD2 physically interacts with TRIM27 via the nucleotide-binding domain, and that NOD2 activation enhances this interaction. Dependent on functional TRIM27, ectopically expressed NOD2 is ubiquitinated with K48-linked ubiquitin chains followed by proteasomal degradation. Accordingly, TRIM27 affects NOD2-mediated pro-inflammatory responses. NOD2 mutations are linked to susceptibility to Crohns disease. We found that TRIM27 expression is increased in Crohns disease patients, underscoring a physiological role of TRIM27 in regulating NOD2 signaling. In HeLa cells, TRIM27 is partially localized in the nucleus. We revealed that ectopically expressed NOD2 can shuttle to the nucleus in a Walker A dependent manner, suggesting that NOD2 and TRIM27 might functionally cooperate in the nucleus. We conclude that TRIM27 negatively regulates NOD2-mediated signaling by degradation of NOD2 and suggest that TRIM27 could be a new target for therapeutic intervention in NOD2-associated diseases.Funding Agencies|German Research Foundation (DFG)|SFB670-NG01|Swedish Society of Medicine||Regional Research Council of South-East Sweden (FORSS)||Swedish Research Council division of Medicine||Gustav V 90th anniversary foundation||Italian Telethon Foundation||DFG|SE 1122/2-1|</p

The cytoskeleton in cell-autonomous immunity: structural determinants of host defence

Host cells use antimicrobial proteins, pathogen-restrictive compartmentalization and cell death in their defence against intracellular pathogens. Recent work has revealed that four components of the cytoskeleton — actin, microtubules, intermediate filaments and septins, which are well known for their roles in cell division, shape and movement — have important functions in innate immunity and cellular self-defence. Investigations using cellular and animal models have shown that these cytoskeletal proteins are crucial for sensing bacteria and for mobilizing effector mechanisms to eliminate them. In this Review, we highlight the emerging roles of the cytoskeleton as a structural determinant of cell-autonomous host defence

Carotinoide und A-Vitamine

Der Name Carotinoide stammt von Tswett (1911)21, geprägt nach Carotin, dem von Wackenroder (183122) krystallisiert erhaltenen, orangeroten, stickstoffreien Farbstoff der Mohrrübe (Daucus carota). Auf die Fettlöslichkeit und das gemeinsame Vorkommen mit Fetten und Lipoiden deutet die Bezeichnung Lipochrome (Krukenberg 1882 23) hin

Vanadiumkomplexe Des Salicylaldoxims

Salicylaldoxim und Natriumvanadat ergeben in wäßriger Lösung über eine gelbe, salzartige Vorstufe [I] bei pH 4 einen braunroten Normalkomplex [III], der bei pH 3 in einen schwarzvioletten Durchdringungskomplex gleicher Zusammensetzung, Oxo‐hydroxo‐bis‐(salicylaldoxim)‐vanadin(V) [IV], übergeht. III bildet bei pH 7 ein Mononatrium‐Salz [II]. — Polare Lösungsmittel führen IV in III über. In unpolaren Lösungsmitteln stellt sich ein temperaturabhängiges Gleichgewicht IV ⇄ III ein (Wp20 = ‐10.1 kcal; ${\rm \vec A}$20 = 22.8, {\rm \mathord{\buildrel{\lower3pt\hbox{\scriptscriptstyle\leftarrow}} \over A} } 20 = 12.7 kcal; ΔS20 = 34 cal/Grad in CCl4). — Aus Salicylaldoxim und Vanadylsulfat entsteht grauviolettes Oxo‐bis‐(salicylaldoxim)‐vanadin(IV) [V], mit Sulfato‐vanadin(III)‐säure aerob ebenfalls V, anaerob ein instabiler, dunkelbrauner Vanadin(III)‐Komplex, dessen Ligand durch das 3‐wertige Vanadium reduziert wird