Human Integrin α3β1 Regulates TLR2 Recognition of Lipopeptides from Endosomal Compartments

Toll-like receptor (TLR)-2/TLR1 heterodimers recognize bacterial lipopeptides and initiate the production of inflammatory mediators. Adaptors and co-receptors that mediate this process, as well as the mechanisms by which these adaptors and co-receptors function, are still being discovered.Using shRNA, blocking antibodies, and fluorescent microscopy, we show that U937 macrophage responses to the TLR2/1 ligand, Pam(3)CSK(4), are dependent upon an integrin, α(3)β(1). The mechanism for integrin α(3)β(1) involvement in TLR2/1 signaling is through its role in endocytosis of lipopeptides. Using inhibitors of endosomal acidification/maturation and physical tethering of the ligand, we show that the endocytosis of Pam(3)CSK(4) is necessary for the complete TLR2/1-mediated pro-inflammatory cytokine response. We also show that TLR2/1 signaling from the endosome results in the induction of different inflammatory mediators than TLR2/1 signaling from the plasma membrane.Here we identify integrin α(3)β(1) as a novel regulator for the recognition of bacterial lipopeptides. We demonstrate that induction of a specific subset of cytokines is dependent upon integrin α(3)β(1)-mediated endocytosis of the ligand. In addition, we address an ongoing controversy regarding endosomal recognition of bacterial lipopeptides by demonstrating that TLR2/1 signals from within endosomal compartments as well as the plasma membrane, and that downstream responses may differ depending upon receptor localization. We propose that the regulation of endosomal TLR2/1 signaling by integrin α(3)β(1) serves as a mechanism for modulating inflammatory responses

Overexpression of Akt1 Enhances Adipogenesis and Leads to Lipoma Formation in Zebrafish

<div><h3>Background</h3><p>Obesity is a complex, multifactorial disorder influenced by the interaction of genetic, epigenetic, and environmental factors. Obesity increases the risk of contracting many chronic diseases or metabolic syndrome. Researchers have established several mammalian models of obesity to study its underlying mechanism. However, a lower vertebrate model for conveniently performing drug screening against obesity remains elusive. The specific aim of this study was to create a zebrafish obesity model by over expressing the insulin signaling hub of the <em>Akt1</em> gene.</p> <h3>Methodology/Principal Findings</h3><p><em>Skin oncogenic transformation screening shows that a stable zebrafish transgenic of Tg(krt4Hsa.myrAkt1</em>)^cy18 displays severely obese phenotypes at the adult stage. In Tg(<em>krt4:Hsa.myrAkt1</em>)^cy18, the expression of exogenous human constitutively active Akt1 (myrAkt1) can activate endogenous downstream targets of mTOR, GSK-3α/β, and 70S6K. During the embryonic to larval transitory phase, the specific over expression of myrAkt1 in skin can promote hypertrophic and hyperplastic growth. From 21 hour post-fertilization (hpf) onwards, myrAkt1 transgene was ectopically expressed in several mesenchymal derived tissues. This may be the result of the integration position effect. Tg(<em>krt4:Hsa.myrAkt1</em>)^cy18 caused a rapid increase of body weight, hyperplastic growth of adipocytes, abnormal accumulation of fat tissues, and blood glucose intolerance at the adult stage. Real-time RT-PCR analysis showed the majority of key genes on regulating adipogenesis, adipocytokine, and inflammation are highly upregulated in Tg(<em>krt4:Hsa.myrAkt1</em>)^cy18. In contrast, the myogenesis- and skeletogenesis-related gene transcripts are significantly downregulated in Tg(<em>krt4:Hsa.myrAkt1</em>)^cy18, suggesting that excess adipocyte differentiation occurs at the expense of other mesenchymal derived tissues.</p> <h3>Conclusion/Significance</h3><p>Collectively, the findings of this study provide direct evidence that Akt1 signaling plays an important role in balancing normal levels of fat tissue in vivo. The obese zebrafish examined in this study could be a new powerful model to screen novel drugs for the treatment of human obesity.</p> </div

Relationship of Geographic Distance, Depth, Temperature, and Viruses with Prokaryotic Communities in the Eastern Tropical Atlantic Ocean

The richness and biogeographical distribution pattern of bacterial and archaeal communities was assessed by terminal restriction fragment length polymorphism analysis of polymerase chain reaction-amplified fragments of the 16S rRNA gene at the surface (15-25 m depth), in the deep chlorophyll maximum layer (DCM; 50 m depth), and deep waters (75-1000 m depth) of the eastern tropical Atlantic Ocean. Additionally, prokaryotic and viral abundance and the frequency of infected prokaryotic cells (FIC) were determined along with physico-chemical parameters to identify factors influencing prokaryotic richness and biogeography. Viral abundance was highest in the DCM layer averaging 45.5 x 10(6) ml(-1), whereas in the mixed surface layer and in the waters below the DCM, average viral abundance was 11.3 x 10(6) and 4.3 x 10(6) ml(-1), respectively. The average estimate of FIC was 8.3% in the mixed surface layer and the DCM and 2.4% in deeper waters. FIC was positively related to prokaryotic and viral abundance and negatively to archaeal richness. There was no detectable effect of geographic distance (maximum distance between stations approximately 4600 km) or differences between water masses on bacterial and archaeal community composition. Bacterial communities showed a clear depth zonation, whereas changes in archaeal community composition were related to temperature and FIC. The results indicate that planktonic archaeal virus host systems are a dynamic component of marine ecosystems under natural conditions