Understanding the mechanisms of Salmonella virulence is an important challenge. The capacity of this intracellular bacterial pathogen to cause diseases depends on the expression of virulence factors including the second type III secretion system (TTSS-2), which is used to translocate into the eukaryotic cytosol a set of effector proteins that divert the biology of the host cell and shape the bacterial replicative niche. Yet little is known about the eukaryotic functions affected by individual Salmonella effectors. Here we report that the TTSS-2 effector PipB2 interacts with the kinesin light chain, a subunit of the kinesin-1 motor complex that drives anterograde transport along microtubules. Translocation of PipB2 is both necessary and sufficient for the recruitment of kinesin-1 to the membrane of the Salmonella-containing vacuole. In vivo, PipB2 contributes to the attenuation of Salmonella mutant strains in mice. Taken together, our data indicate that the TTSS-2-mediated fine-tuning of kinesin-1 activity associated with the bacterial vacuole is crucial for the virulence of Salmonella.SifA ͉ molecular motor

TNF-stimulated gene/protein-6 (TSG-6) is expressed by many different cell types in response to pro-inflammatory cytokines and plays an important role in the protection of tissues from the damaging consequences of acute inflammation. Recently, TSG-6 was identified as being largely responsible for the beneficial effects of multipotent mesenchymal stem cells, for example in the treatment of animal models of myocardial infarction and corneal injury/allogenic transplant. The protective effect of TSG-6 is due in part to its inhibition of neutrophil migration, but the mechanism(s) underlying this activity remain(s) unknown. Here we have shown that TSG-6 inhibits chemokine-stimulated trans-endothelial migration of neutrophils via a direct interaction (KD ~25 nM) between TSG-6 and the glycosaminoglycan-binding site of CXCL8, which antagonizes the association of CXCL8 with heparin. Furthermore, we found that TSG-6 impairs the binding of CXCL8 to cell surface glycosaminoglycans and the transport of CXCL8 across an endothelial cell monolayer. In vivo this could limit the formation of haptotactic gradients on endothelial heparan sulfate proteoglycans and, hence, integrin-mediated tight adhesion and migration. We further observed that TSG-6 suppresses CXCL8-mediated chemotaxis of neutrophils; this lower potency effect might be important at sites where there is high local expression of TSG-6. Thus, we have identified TSG-6 as a CXCL8-binding protein, making it the first soluble mammalian chemokine-binding protein to be described to date. We have also revealed a potential mechanism whereby TSG-6 mediates its anti-inflammatory and protective effects. This could inform the development of new treatments for inflammation in the context of disease or post transplantation.

Several protein-protein interactions within the SARS-CoV proteome have been identified, one of them being between nonstructural proteins nsp10 and nsp16. In this work, we have mapped key residues on the nsp10 surface involved in this interaction. Alanine-scanning mutagenesis, bioinformatics, and molecular modeling were used to identify several "hot spots," such as Val 42 Coronaviruses (CoVs),7 classified into the family Coronaviridae in the order Nidovirales, possess a viral RNA genome that is among the largest known (2). They include important pathogens of livestock, wild and companion animals, and humans, such as the severe acute respiratory syndrome CoV (SARSCoV) (3-5). They are mainly etiological agents of respiratory and enteric diseases, exemplified by the worldwide pandemic of SARS-CoV spreading in 2003 from Asia, with a final number of cases around 8,000 and a 10% mortality.The genome of SARS-CoV contains a single-stranded plussense RNA of ϳ29.7 kb (2). At the molecular level, CoVs employ a variety of unusual strategies to accomplish a complex program of gene expression (5). Coronavirus replication requires the synthesis of both genomic and multiple subgenomic RNA species and the assembly of progeny virions by a pathway that is unique among enveloped RNA viruses (5-7). Fourteen open reading frames (ORFs) have been identified, of which 12 are located in the 3Ј-end of the genome. The other two ORFs (1a and 1b), which are located in the 5Ј-proximal twothirds of the genome, encode two large polyproteins translated directly from genomic RNA. ORF 1b is expressed by a Ϫ1 ribosomal frameshifting at the end of pp1a, extending its coding sequence and thus generating the pp1ab polyprotein (6). These two polyproteins are cleaved into 16 functional viral replicase proteins called nsp1 to -16 (for non-structural proteins 1-16). Those nsps form the membrane-bound replication-transcription complex, which is localized to a network of endoplasmic reticulum-derived membranes in the infected cell (8, 9). Bioinformatics, structural biology, (reverse) genetics, and biochemical studies have contributed to the characterization of CoV