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Abstract Background Four and one half LIM domain protein 2 (FHL2) has been reported to be a key regulator in many cellular processes being associated with fibrogenesis such as cell migration and contraction. Moreover, hepatic FHL2 is involved in regulation pathways mediating proliferation and cell death machineries. We here investigated the role of FHL2 in the setting of experimental and clinical liver fibrosis. Methods FHL2−/− and wild type (wt) mice were challenged with CCl4. Fibrotic response was assessed by quantitative real time PCR (qRT-PCR) of fibrotic marker genes, measurement of hydroxyproline content and histological methods. Murine FHL2−/− and hepatic stellate cells (HSC) were isolated and investigated via immunofluorescence. Human fibrotic and normal liver samples were analysed immunohistochemically using antibodies directed against FHL2. Results FHL2−/− mice displayed aggravated liver fibrosis compared to wt mice. However, immunofluorescence revealed no significant morphological changes in cultured FHL2−/− and wt myofibroblasts (MFB). In human liver samples, FHL2 was strongly expressed both in the nucleus and cytoplasm in MFB of fibrotic livers. In contrast, FHL2 expression was absent in normal liver tissue. Conclusions Deficiency of FHL2 results in aggravation of murine liver fibrosis. In human liver samples, FHL2 is expressed in activated HSCs and portal fibroblasts in human fibrotic livers, pointing to a central role of FHL2 for human hepatic fibrogenesis as well.

The pattern-recognition molecule Nod1 is a critical sensor for bacterial derived diaminopimelic acid-containing peptidoglycan fragments which induces innate immune responses in epithelial cells. Here we report the subcellular localization of this protein in human epithelial cells. Nod1 is localized in the cytosol and at the plasma membrane in human cells. This membrane association is dependent on the integrity of the protein, on its signalling capacity and on an intact actin cytoskeleton. Signalling-inactive mutants of Nod1 or disruption of the actin cytoskeleton interferes with this localization pattern and impacts on downstream NF-κB activation. Moreover, the invasive bacterium Shigella flexneri was used as a model for physiological activation of Nod1. Imaging revealed that Nod1 is recruited to the site of bacterial entry, where it colocalizes with NEMO. Our data provide evidence that membrane association is linked to Nod1 function and, in view of recent findings on Nod2, that this may be a common feature of NLR family members. [ABSTRACT FROM AUTHOR]

Formation of iron/sulfur (Fe/S) clusters, protein translocation and protein folding are essential processes in the mitochondria of Saccharomyces cerevisiae. In a systematic approach to characterize essential proteins involved in these processes, we identified a novel essential protein of the mitochondrial matrix, which is highly conserved from yeast to human and which we termed Isd11. Depletion of Isd11 caused a strong reduction in the levels of the Fe/S proteins aconitase and the Rieske protein, and a massive decrease in the enzymatic activities of aconitase and succinate dehydrogenase. Incorporation of iron into the Fe/S protein Leu1 and formation of the Fe/S cluster containing holoform of the mitochondrial ferredoxin Yah1 were inhibited in the absence of Isd11. This strongly suggests that Isd11 is required for the assembly of Fe/S proteins. We show that Isd11 forms a stable complex with Nfs1, the cysteine desulfurase of the mitochondrial machinery for Fe/S cluster assembly. In the absence of Isd11, Nfs1 is prone to aggregation. We propose that Isd11 acts together with Nfs1 in an early step in the biogenesis of Fe/S proteins. [ABSTRACT FROM AUTHOR]

A hallmark of solid tumors is the consumption of large amounts of glucose and production of lactate, also known as Warburg-like metabolism. This metabolic phenotype is typical for aggressive tumor growth, and can be visualized by 18F-fluorodeoxyglucose (18F-FDG) uptake detected by positron emission tomography (PET). High 18F-FDG uptake inversely correlates with survival and goes along with reduced expression of the catalytic beta-subunit of the H+-ATP synthase (ß-F1-ATPase) in several tumor entities analyzed so far.For this study we characterized a series of 15 head and neck squamous cell carcinoma (HNSCC) by (i) determining 18F-FDG-uptake; (ii) quantitative expression analysis of ß-F1-ATPase (Complex V), NDUF-S1 (Complex I) and COX1 (Complex IV) of the mitochondrial electron transport chain (ETC), as well as Hsp60 (mitochondrial mass) and GAPDH (glycolysis) in tumor cells; (iii) sequencing of the mtDNA of representative tumor samples.Whereas high 18F-FDG-uptake also correlates with poor prognosis in HNSCC, it surprisingly is accompanied by high levels of ß-F1-ATPase, but not by any of the other analyzed proteins.In conclusion, we here describe a completely new phenotype of metabolic adaptation possibly enabling those tumors with highest levels of ß-F1-ATPase to rapidly proliferate even in hypoxic zones, which are typical for HNSCC.

Members of the NLR family evolved as intracellular sensors for bacterial and viral infection. However, our knowledge on the implication of most of the human NLR proteins in innate immune responses still remains fragmentary. Here we characterized the role of human NLRP10 in bacterial infection. Our data revealed that NLRP10 is a cytoplasmic localized protein that positively contributes to innate immune responses induced by the invasive bacterial pathogen Shigella flexneri. SiRNA-mediated knock-down studies showed that NLRP10 contributes to pro-inflammatory cytokine release triggered by Shigella in epithelial cells and primary dermal fibroblasts, by influencing p38 and NF-κB activation. This effect is dependent on the ATPase activity of NLRP10 and its PYD domain. Mechanistically, NLRP10 interacts with NOD1, a NLR that is pivotally involved in sensing of invasive microbes, and both proteins are recruited to the bacterial entry point at the plasma membrane. Moreover, NLRP10 physically interacts with downstream components of the NOD1 signalling pathway, such as RIP2, TAK1 and NEMO. Taken together, our data revealed a novel role of NLRP10 in innate immune responses towards bacterial infection and suggest that NLRP10 functions as a scaffold for the formation of the NOD1-Nodosome., (© 2012 Blackwell Publishing Ltd.)