Necrotizing enterocolitis (NEC) is a devastating neonatal intestinal inflammatory disease, occurring primarily in premature infants, causing significant morbidity and mortality. The pathogenesis of NEC is associated with an excessive inflammatory IL-8 response. In this study, we hypothesized that this excessive inflammatory response is related to an immature expression of innate immune response genes. To address this hypothesis, intestinal RNA expression analysis of innate immune response genes was performed after laser capture microdissection of resected ileal epithelium from fetuses, NEC patients and children and confirmed in ex vivo human intestinal xenografts. Changes in mRNA levels of toll-like receptors (TLR)-2 and -4, their signaling molecules and transcription factors (MyD88, TRAF-6 and NFκB1) and negative regulators (SIGIRR, IRAK-M, A-20 and TOLLIP) and the effector IL-8 were characterized by qRT-PCR. The expression of TLR2, TLR4, MyD88, TRAF-6, NFκB1 and IL-8 mRNA was increased while SIGIRR, IRAK-M, A-20 and TOLLIP mRNA were decreased in fetal vs. mature human enterocytes and further altered in NEC enterocytes. Similar changes in mRNA expression were observed in immature, but not mature, human intestinal xenografts. Confirmation of gene expression was also validated with selective protein measurements and with suggested evidence that immature TRL4 enterocyte surface expression was internalized in mature enterocytes. Cortisone, an intestinal maturation factor, treatment corrected the mRNA differences only in the immature intestinal xenograft. Using specific siRNA to attenuate expression of primary fetal enterocyte cultures, both TOLLIP and A-20 were confirmed to be important when knocked down by exhibiting the same excessive inflammatory response seen in the NEC intestine. We conclude that the excessive inflammatory response of the immature intestine, a hallmark of NEC, is due to a developmental immaturity in innate immune response genes.

We report here the molecular cloning of a newly identified preprotachykinin gene, Pptc, which specifies the sequence for a new preprotachykinin protein and bioactive peptide designated hemokinin 1 (HK-1). PPT-C mRNA was detected primarily in hematopoietic cells in contrast to the previously described Ppta and Pptb genes, which are predominantly expressed in neuronal tissues. HK-1 has several biological activities that are similar to the most studied tachykinin, substance P, such as induction of plasma extravasation and mast cell degranulation. However, HK-1 also has properties that are indicative of a critical role in mouse B cell development. HK-1 stimulated the proliferation of interleukin 7-expanded B cell precursors, whereas substance P had no effect. HK-1, but not substance P, promoted the survival of freshly isolated bone marrow B lineage cells or cultured, lipopolysaccharide-stimulated pre-B cells. N-acetyl-L-trytophan-3,5-bistrifluromethyl benzyl ester, a tachykinin receptor antagonist, increased apoptosis of these cells and in vivo administration of this antagonist led to specific reductions of the B220lowCD43 population (the pre-B cell compartment) in the bone marrow and the IgMhighIgDlow population (the newly generated B cells) in the spleen. Thus, HK-1 may be an autocrine factor that is important for the survival of B cell precursors at a critical phase of development.

Despite our general understanding that members of the SNARE superfamily participate in diverse intracellular docking/fusion events, the physiological role of the majority of SNAREs in the intact organism remains elusive. In this study, through targeted gene knockout in mice, we establish that VAMP8/endobrevin is a major player in regulated exocytosis of the exocrine pancreas. VAMP8 is enriched on the membrane of zymogen granules and exists in a complex with syntaxin 4 and SNAP-23. VAMP8-/- mice developed normally but showed severe defects in the pancreas. VAMP8 null acinar cells contained three times more zymogen granules than control acinar cells. Furthermore, secretagogue-stimulated secretion was abolished in pancreatic fragments derived from VAMP8-/- mice. In addition, VAMP8-/- mice were partially resistant to supramaximal caerulein-induced pancreatitis. These results suggest a major physiological role of VAMP8 in regulated exocytosis of pancreatic acinar cells by serving as a v-SNARE of zymogen granules.

The endoplasmic reticulum (ER) of animal cells is a single, dynamic, and continuous membrane network of interconnected cisternae and tubules spread out throughout the cytosol in direct contact with the nuclear envelope. During mitosis, the nuclear envelope undergoes a major rearrangement, as it rapidly partitions its membrane-bound contents into the ER. It is therefore of great interest to determine whether any major transformation in the architecture of the ER also occurs during cell division. We present structural evidence, from rapid, live-cell, three-dimensional imaging with confirmation from high-resolution electron microscopy tomography of samples preserved by high-pressure freezing and freeze substitution, unambiguously showing that from prometaphase to telophase of mammalian cells, most of the ER is organized as extended cisternae, with a very small fraction remaining organized as tubules. In contrast, during interphase, the ER displays the familiar reticular network of convolved cisternae linked to tubules.

Follicular helper T (Tfh) cells are recognized as a distinct CD4+ helper T-cell subset, which provides for B-cell activation and production of specific antibody responses, and play a critical role in the development of autoimmune disease. So far, only one study investigated the circulating Tfh cells increased in a subset of SLE patients. Since relatively little is known about the Tfh cells in rheumatoid arthritis (RA) patients, in this study, Tfh-cell frequency, related cytokine IL-21, and transcription factor Bcl-6 were investigated in 53 patients with RA and 31 health controls. Firstly, we found that the frequency of CD4+CXCR5+ICOShigh Tfh cells was increased significantly in the peripheral blood of RA patients, compared with that in healthy controls. It is known that Tfh cells are critical for directing the development of an antibody response by germinal centers B cells; secondly, we observed that the Tfh-cell frequency is accompanied by the level of anti-CCP antibody in RA patients. Furthermore, expression of Bcl-6 mRNA and plasma IL-21 concentrations in RA patients was increased. Taken together, these findings have shown that the increased frequency of circulating Tfh cells is correlated with elevated levels of anti-CCP antibody, indicating the possible involvement of Tfh cells in the disease progression of RA.

A cellular role and the mechanism of action for small GTPase Arl1 have been defined. Arl1-GTP interacts with the GRIP domains of Golgin-97 and Golgin-245, a process dependent on conserved residues of the GRIP domains that are important for Golgi targeting. The switch II region of Arl1 confers the specificity of this interaction. Arl1-GTP mediates Golgi recruitment of Golgin-97 in a switch II-dependent manner, whereas tethering Arl1-GTP onto endosomes can mediate endosomal targeting of Golgin-97. Golgin-97 and Golgin-245 are dissociated from the Golgi when Arl1 is knocked-down by its siRNA. Arl1-GTP thus functions to recruit Golgin-97 and Golgin-245 onto the Golgi via interacting with their GRIP domains.

An in vitro transport assay, established with a modified Shiga toxin B subunit (STxB) as a marker, has proved to be useful for the study of transport from the early/recycling endosome (EE/RE) to the trans-Golgi network (TGN). Here, we modified this assay to test antibodies to all known soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) that have been shown to localize in the Golgi and found that syntaxin 5, GS28, Ykt6, and GS15 antibodies specifically inhibited STxB transport. Because syntaxin 5, GS28, Ykt6, and GS15 exist as a unique SNARE complex, our observation indicates that these four SNAREs function as a complex in EE/RE-TGN transport. The importance of GS15 in EE/RE-TGN transport was further demonstrated by a block in recombinant STxB transport in HeLa cells when GS15 expression was knocked down by its small interfering iRNA. Morphological analyses showed that some GS15 and Ykt6 were redistributed from the Golgi to the endosomes when the recycling endosome was perturbed by SNX3-overexpression, suggesting that GS15 and Ykt6 might cycle between the endosomes and the Golgi apparatus. Further studies indicated that syntaxin 5 and syntaxin 16 exerted their role in EE/RE-TGN transport in an additive manner. The kinetics of inhibition exhibited by syntaxin 16 and syntaxin 5 antibodies is similar. INTRODUCTIONMammalian cells endocytose a variety of molecules. Some of them escape from the lysosomal degradative pathway and are instead delivered to the Golgi apparatus. Examples of these are some protein toxins such as cholera toxin, Shiga toxin, and ricin (Sandvig and van Deurs, 2002) as well as some endogenous proteins such as TGN38 (Ghosh et al., 1998;Mallet and Maxfield, 1999), mannose 6-phosphate receptor (Goda and Pfeffer, 1988), furin (Mallet and Maxfield, 1999), GLUT4 (Shewan et al., 2003), and some glycosylphosphatidylinositol (GPI)-anchored proteins (Nichols et al., 2001;Nichols, 2002). To date, several retrograde transport pathways in the endocytic route to the trans-Golgi network (TGN) have been identified. These include a well-studied pathway from the late endosome to the TGN taken by mannose 6-phosphate receptors (Goda and Pfeffer, 1988) and furin (Mallet and Maxfield, 1999), and a newly discovered direct pathway from the early/recycling endosome to the TGN taken by TGN38 (Ghosh et al., 1998;Mallet and Maxfield, 1999), GLUT4 (Shewan et al., 2003), and exogenously added Shiga toxin B subunit (Mallard et al., 1998). Similar transport from the late endosome (prevacuolar compartment) and the early/recycling endosome (post-Golgi compartment) to the TGN (late Golgi) has been described in the yeast Saccharomyces cerevisiae (Bensen et al., 2001;Siniossoglou et al., 2001). Recently, GPI-anchored green fluorescent protein (GFP), CD59, and a fraction of cholera toxin B subunit have been found to accumulate in a discrete population of endosomes en route to the Golgi apparatus (Nichols, 2002). These endosomes are devoid of markers for classical early and recycling endosomes, but they do...

Communication between microorganisms and the gastrointestinal epithelium, ie, bacterial-epithelial "crosstalk," is examined. Because most basic research on the molecular interaction of bacteria with the gut epithelium relates to pathogen-enterocyte interaction, crosstalk with pathologic bacterial is considered in detail. Through their interactions with the intestinal epithelium, pathogens can modify epithelium function to enhance their penetration across the epithelial barrier and to exploit mucosal host defenses for their own benefit. Three representative pathogens are used to illustrate the various adaptive techniques used to colonize and penetrate the mucosal barrier. Salmonella enterica typhimurium interacts with the physiologic receptor for epidermal growth factor to co-opt the receptor's signal transduction mechanisms. Enteropathic Escherichia coli secretes a receptor (type III secretion) into the microvillus surface of enterocytes that disrupts the microvillus and alters its actin structure to form a dome-like anchoring site. Shigella flexneri is used to illustrate how pathogens use the follicular epithelial cell (M cell), the physiologic conduit for antigens to reach gut associated-lymphoid tissues, for penetration of the epithelial barrier. Shigella organisms attached to M cells use their endocytotic properties to enter the cell. Once inside the cell, the organism lyses the endocytic vacuole and co-opts actin and myosin to form a propelling tail for further penetration of the epithelium through the basolateral surface. Probiotics can protect the intestine by competing with pathogens for attachment, strengthening tight junctions between enterocytes, and enhancing the mucosal immune response to pathogens. However, additional molecular studies are needed to define more precisely the mechanism of probiotic-epithelial crosstalk.