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

Background: Nutrients stimulate calcium dependent activation of energy metabolism, in pancreatic beta cells.Results: Glucose-induced ATP synthase-dependent respiration is strictly calcium-dependent, with little or no effect of calcium on the NAD(P)H response.Conclusion: Calcium coordinates oxidative metabolism and respiration in pancreatic beta cells.Significance: Calcium has novel mitochondrial targets downstream of mitochondrial dehydrogenases.

a b s t r a c tTo further characterize the molecular events supporting the tumor suppressor activity of Scrib in mammals, we aim to identify new binding partners. We isolated MCC, a recently identified binding partner for b-catenin, as a new interacting protein for Scrib. MCC interacts with both Scrib and the NHERF1/NHERF2/Ezrin complex in a PDZ-dependent manner. In T47D cells, MCC and Scrib proteins colocalize at the cell membrane and reduced expression of MCC results in impaired cell migration. By contrast to Scrib, MCC inhibits cell directed migration independently of Rac1, Cdc42 and PAK activation. Altogether, these results identify MCC as a potential scaffold protein regulating cell movement and able to bind Scrib, b-catenin and NHERF1/2.

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease that shows minimal response to chemotherapy. Genetic changes involved in the progression of PDAC concern genes that encode proteins related to signal transduction networks. This fact reveals the importance in identifying the role and the relations between multiple signaling cascades in PDAC. One of the major factors that modulate signaling events is multidomain scaffold proteins that function by binding several proteins simultaneously, inducing their proximity and influencing the outcome of signaling. A particular group among them, containing multiple Src homology 3 (SH3) domains that can bind proteins containing proline-rich motifs, was associated to different aspects of cancer cell homeostasis. In this work, using a microarray-based analysis, we have shown that 13 multiple SH3 domain containing scaffold proteins are expressed in PDAC cells. Using a yeast two-hybrid approach, we have identified proteins that interact with these adaptor proteins. Among them we have found several molecules that modulate cell proliferation and survival (CIZ1, BIRC6, RBBP6), signaling (LTBP4, Notch2, TOM1L1, STK24) and membrane dynamics (PLSCR1, DDEF2, VCP). Our results indicate that interactions mediated by multi-SH3 domain-containing proteins could lead to the formation of dynamic protein complexes that function in pancreatic cancer cell signaling. The identification of such protein complexes is of paramount importance in deciphering pancreatic cancer biology and designing novel therapeutic approaches.

Mantle cell lymphoma (MCL) is one of the most frequent of the newly recognized non-Hodgkin's lymphomas. The major problem of MCL therapy is the occurrence of relapse and subsequent resistance to chemotherapy and immunotherapy in virtually all cases. Here, we show that one injection of antihuman transferrin receptor (TfR) monoclonal antibody A24 totally prevented xenografted MCL tumor establishment in nude mice. It also delayed and inhibited tumor progression of established tumors, prolonging mice survival. In vitro, A24 induced up to 85% reduction of MCL cell proliferation (IC 50 = 3.75 nmol/L) independently of antibody aggregation, complement-dependent or antibody-dependent cell-mediated cytotoxicity. A24 induced MCL cell apoptosis through caspase-3 and caspase-9 activation, either alone or synergistically with chemotherapeutic agents. A24 induced TfR endocytosis via the clathrin adaptor protein-2 complex pathway followed by transport to lysosomal compartments. Therefore, A24-based therapies alone or in association with classic chemotherapies could provide a new alternative strategy against MCL, particularly in relapsing cases. [Cancer Res 2007;67(3):1145-54]

No abstract