Peroxisomes transport folded and oligomeric proteins across their membrane. Two cytosolic import receptors, Pex5p and Pex7p, along with approximately 12 membrane-bound peroxins participate in this process. While interactions among individual peroxins have been described, their organization into functional units has remained elusive. We have purified and defined two core complexes of the peroxisomal import machinery: the docking complex comprising Pex14p and Pex17p, with the loosely associated Pex13p, and the RING finger complex containing Pex2p, Pex10p, and Pex12p. Association of both complexes into a larger import complex requires Pex8p, an intraperoxisomal protein. We conclude that Pex8p organizes the formation of the larger import complex from the trans side of the peroxisomal membrane and thus might enable functional communication between both sides of the membrane.

Pancreatic cancer is one of the most fatal malignancies lacking effective therapies. Notch signaling is a key regulator of cell fate specification and pancreatic cancer development; however, the role of individual Notch receptors and downstream signaling is largely unknown. Here, we show that Notch2 is predominantly expressed in ductal cells and pancreatic intraepithelial neoplasia (PanIN) lesions. Using genetically engineered mice, we demonstrate the effect of conditional Notch receptor ablation in Kras G12D-driven pancreatic carcinogenesis. Deficiency of Notch2 but not Notch1 stops PanIN progression, prolongs survival, and leads to a phenotypical switch toward anaplastic pancreatic cancer with epithelial-mesenchymal transition. By expression profiling, we identified increased Myc signaling regulated by Notch2 during tumor development, placing Notch2 as a central regulator of PanIN progression and malignant transformation. Our study supports the concept of distinctive roles of individual Notch receptors in cancer development.genetically engineered mice | K-Ras | Myc | Notch | pancreatic cancer P ancreatic ductal adenocarcinoma (PDAC) remains a devastating disease despite tremendous therapeutical efforts. PDAC derives from several preneoplastic lesions, including pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm (MCN), of which PanINs are the most common precursors (1). PanINs typically progress through defined histological and molecular stages, with the most advanced PanIN3 lesion being defined as carcinoma in situ (2). Because of early metastatic spread, PanIN3 represents the latest curable precursor lesion. Thus, defining the regulators of PanIN initiation and progression is of utmost importance.

IntroductionLiver failure patients might be at risk for citrate accumulation during continuous venovenous hemodialysis (CVVHD) with regional citrate anticoagulation. The aim of this study was to investigate the predictive capability of baseline liver function parameters regarding citrate accumulation, expressed as an increase in the calcium total/calcium ionized (Catot/Caion) ratio ≥2.5, and to describe the feasibility of citrate CVVHD in liver failure patients.MethodsWe conducted a prospective observational study in medical ICU patients treated in a German university hospital. We performed 43 CVVHD runs using citrate for regional anticoagulation in 28 critically ill patients with decompensated liver cirrhosis or acute liver failure (maximum of two CVVHD runs per patient). Liver function was characterized before CVVHD using laboratory parameters, calculation of Child-Pugh and Model of End-stage Liver Disease scores, and determination of the plasma disappearance rate of indocyanine green. In addition to blood gas analysis, we measured total calcium and citrate in serum at baseline and after definitive time points for each CVVHD run.ResultsAccumulation of citrate in serum correlated with an increase in the Catot/Caion ratio. Although the critical upper threshold of Catot/Caion ratio ≥2.5 was exceeded 10 times in seven different CVVHD runs, equalization of initial metabolic acidosis was possible without major disturbances of acid-base and electrolyte status. Standard laboratory liver function parameters showed poor predictive capabilities regarding citrate accumulation in terms of an elevated Catot/Caion ratio ≥2.5. In contrast, serum lactate ≥3.4 mmol/l and prothrombin time ≤26% predicted an increase in the Catot/Caion ratio ≥2.5 with high sensitivity (86% for both lactate and prothrombin time) and specificity (86% for lactate, 92% for prothrombin time).ConclusionsDespite substantial accumulation of citrate in serum, CVVHD with regional citrate anticoagulation seems feasible in patients with severely impaired liver function. Citrate accumulation in serum is reflected by an increase in the Catot/Caion ratio. To identify patients at risk for citrate accumulation in terms of a Catot/Caion ratio ≥2.5, baseline serum lactate (threshold ≥3.4 mmol/l) and prothrombin time (threshold ≤26%) may be useful for risk prediction in daily clinical practice. Careful monitoring of electrolytes and acid-base status is mandatory to ensure patient safety.

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Whereas the final differentiation of conventional dendritic cells (CDCs) from committed precursors occurs locally in secondary lymphoid or peripheral tissues, plasmacytoid dendritic cells (PDCs) are thought to fully develop in the bone marrow from common DC progenitors before migrating to the periphery. In our study, we define, for the first time, a subpopulation of CCR9 ؊ major histocompatibility complex class II low PDCs in murine bone marrow, which express E2-2 and are immediate precursors of CCR9 ؉ fully differentiated PDCs. However, CCR9 IntroductionAlthough plasmacytoid dendritic cells (PDCs) express markers of the "lymphoid" lineage, they can be derived from both common myeloid and common lymphoid progenitors. 1 Several elegant studies have convincingly shown that PDCs arise from common dendritic cell (DC) progenitors (or pro-DCs) in the bone marrow (BM), 2,3 which have the additional potential to generate precursor cells committed to conventional dendritic cell (CDC) development (pre-CDCs). 4,5 In contrast, common DC progenitors derived precursor cells committed exclusively to PDC development have not been described. Generation of PDCs is dependent on transcription factor E2-2, which drives the expression of other key transcription factors involved in PDC development and function (IRF8, Spi-B, IRF7) as well as PDC-specific markers (BST2 and Siglec H in murine PDCs, BDCA2 in human PDCs). 6 It has been reported that a population of Siglec-H-negative PDC-like cells in murine BM, which is only present in lymphocytic choriomeningitis virus-infected mice is capable of differentiating into CDCs during viral infection in a type I interferon (IFN)-dependent manner. 7,8 The potential of PDCs or committed PDC precursors to differentiate into other DC subpopulations in the absence of infection is unknown.It has been assumed from the available data that PDCs fully differentiate in the BM, circulate in the blood, and then enter lymphoid organs and peripheral tissues. CDCs, however, are generated from circulating committed precursors (pre-CDCs), which differentiate locally in lymphoid and peripheral tissues under the control of growth factors, such as Fms-like tyrosine kinase 3 ligand (Flt3L). 4,9 Thus, the development of CDC subpopulations is shaped by the local microenvironment allowing adaptation to tissue-specific functions. This has been shown recently for DCs in the intestinal lamina propria whose development from precursors is driven by local growth factors and the enteric microbial flora. [10][11][12] It is so far not clear whether PDCs in the intestine or in other peripheral tissues exclusively derive from fully differentiated circulating PDCs 13 or whether they can also differentiate locally from committed precursor cells under the influence of the specific tissue microenvironment.In this study, we identify an immediate PDC precursor in murine BM, which is characterized by expression of the transcription factor E2-2, PDC-specific markers (BST2, Siglec H), and production of type I IFN but lack of CCR9 and lo...

Growth factors have been implicated in pancreatic carcinogenesis. In this study we analyzed the effect of Tgfa overexpression in addition to mutant Kras(G12D) by crossing Elastase-Tgfa mice with p48(+/Cre);Kras(+/LSL-G12D) mice. We show that concomitant expression of TGFalpha and Kras(G12D) accelerates the progression of mPanIN lesions to metastatic pancreatic cancer and leads to the development of cystic papillary lesions resembling human intraductal papillary mucinous neoplasms (IPMN). Microarray data in mice revealed an IPMN signature and IPMNs expressed MUC1 and MUC5AC but not MUC2, similar to human pancreatobiliary IPMNs. Invasive ductal adenocarcinoma developed from PanINs and IPMNs, suggesting precursor lines for both lesion types in this model. In conclusion, Egfr signaling in synergy with oncogenic Kras may be a prerequisite for IPMN development and progression to pancreatic cancer.

Import of peroxisomal matrix proteins is essential for peroxisome biogenesis. Genetic and biochemical studies using a variety of different model systems have led to the discovery of 23 PEX genes required for this process. Although it is generally believed that, in contrast to mitochondria and chloroplasts, translocation of proteins into peroxisomes involves a receptor cycle, there are reported differences of an evolutionary conservation of this cycle either with respect to the components or the steps involved in different organisms. We show here that the early steps of protein import into peroxisomes exhibit a greater similarity than was thought previously to be the case. Pex20p of Yarrowia lipolytica, Pex18p and Pex21p of Saccharomyces cerevisiae and mammalian Pex5pL fulfil a common function in the PTS2 pathway of their respective organisms. These non-orthologous proteins possess a conserved sequence region that most likely represents a common PTS2-receptor binding site and di-aromatic pentapeptide motifs that could be involved in binding of the putative docking proteins. We propose that not necessarily the same proteins but functional modules of them are conserved in the early steps of peroxisomal protein import.

that caution should be exercised when exploring the use of pharmaceuticals targeting the CXCR2 receptor as a therapeutic option for the treatment of various solid tumors.