Yu-Hong Cui

Stabilization of XIAP mRNA through the RNA binding protein HuR regulated by cellular polyamines

The X chromosome-linked inhibitor of apoptosis protein (XIAP) is the most potent intrinsic caspase inhibitor and plays an important role in the maintenance of intestinal epithelial integrity. The RNA binding protein, HuR, regulates the stability and translation of many target transcripts. Here, we report that HuR associated with both the 3′-untranslated region and coding sequence of the mRNA encoding XIAP, stabilized the XIAP transcript and elevated its expression in intestinal epithelial cells. Ectopic HuR overexpression or elevated cytoplasmic levels of endogenous HuR by decreasing cellular polyamines increased [HuR/XIAP mRNA] complexes, in turn promoting XIAP mRNA stability and increasing XIAP protein abundance. Conversely, HuR silencing in normal and polyamine-deficient cells rendered the XIAP mRNA unstable, thus reducing the steady state levels of XIAP. Inhibition of XIAP expression by XIAP silencing or by HuR silencing reversed the resistance of polyamine-deficient cells to apoptosis. Our findings demonstrate that HuR regulates XIAP expression by stabilizing its mRNA and implicates HuR-mediated XIAP in the control of intestinal epithelial apoptosis.

miR-503 represses CUG-binding protein 1 translation by recruiting CUGBP1 mRNA to processing bodies

This study shows that microRNA-503 interacts with the CUG-binding protein 1 (CUGBP1) mRNA and represses its translation by recruiting the CUGBP1 mRNA to processing bodies.

Regulation of Cyclin-Dependent Kinase 4 Translation through CUG-Binding Protein 1 and microRNA-222 by Polyamines

The findings presented indicate that polyamine-regulated CUG-binding protein 1 and microRNA-222 modulate cyclin-dependent kinase 4 (CDK4) translation at least in part by altering the recruitment of CDK4 mRNA to processing bodies.

STIM1 translocation to the plasma membrane enhances intestinal epithelial restitution by inducing TRPC1-mediated Ca2+ signaling after wounding

Early epithelial restitution is an important repair modality in the gut mucosa and occurs as a consequence of epithelial cell migration. Canonical transient receptor potential-1 (TRPC1) functions as a store-operated Ca2+ channel (SOCs) in intestinal epithelial cells (IECs) and regulates intestinal restitution, but the exact upstream signals initiating TRPC1 activation after mucosal injury remain elusive. Stromal interaction molecule 1 (STIM1) is a single membrane-spanning protein and is recently identified as essential components of SOC activation. The current study was performed to determine whether STIM1 plays a role in the regulation of intestinal epithelial restitution by activating TRPC1 channels. STIM1 translocation to the plasma membrane increased after wounding, which was followed by an increase in IEC migration to reseal wounds. Increased STIM1 levels at the plasma membrane by overexpressing EF-hand mutant STIM1 enhanced Ca2+ influx through SOCs and stimulated IEC migration after wounding. STIM1 interacted with TRPC1 and formed STIM1/TRPC1 complex, whereas inactivation of STIM1 by STIM1 silencing decreased SOC-mediated Ca2+ influx and inhibited epithelial restitution. In cells overexpressing EF-hand mutant STIM1, TRPC1 silencing also decreased STIM1/TRPC1 complex, reduced SOC-mediated Ca2+ influx, and repressed cell migration after wounding. Our findings demonstrate that induced STIM1 translocation to the plasma membrane promotes IEC migration after wounding by enhancing TRPC1-mediated Ca2+ signaling and provide new insight into the mechanism of intestinal epithelial restitution.

Polyamines inhibit the assembly of stress granules in normal intestinal epithelial cells regulating apoptosis.

Polyamines regulate multiple signaling pathways and are implicated in many aspects of cellular functions, but the exact molecular processes governed by polyamines remain largely unknown. In response to environmental stress, repression of translation is associated with the assembly of stress granules (SGs) that contain a fraction of arrested mRNAs and are thought to function as mRNA storage. Here we show that polyamines modulate the assembly of SGs in normal intestinal epithelial cells (IECs) and that induced SGs following polyamine depletion are implicated in the protection of IECs against apoptosis. Increasing the levels of cellular polyamines by ectopic overexpression of the ornithine decarboxylase gene decreased cytoplasmic levels of SG-signature constituent proteins eukaryotic initiation factor 3b and T-cell intracellular antigen-1 (TIA-1)-related protein and repressed the assembly of SGs induced by exposure to arsenite-induced oxidative stress. In contrast, depletion of cellular polyamines by inhibiting ornithine decarboxylase with α-difluoromethylornithine increased cytoplasmic eukaryotic initiation factor 3b and TIA-1 related protein abundance and enhanced arsenite-induced SG assembly. Polyamine-deficient cells also exhibited an increase in resistance to tumor necrosis factor-α/cycloheximide-induced apoptosis, which was prevented by inhibiting SG formation with silencing SG resident proteins Sort1 and TIA-1. These results indicate that the elevation of cellular polyamines represses the assembly of SGs in normal IECs and that increased SGs in polyamine-deficient cells are crucial for increased resistance to apoptosis.

986 Mir-29b and Mir-503 Differentially Modulate Intestinal Epithelial Barrier Function by Altering Claudin-1 Expression

G A A b st ra ct s uncertain (e.g. ulcer disease, esophagitis). Analyzing data through 2009, we then identified individuals within the cohort who had a repeat EGD within three years of their index EGD. Results: Approximately 11.6% of Medicare beneficiaries in the sample underwent an index EGD between 2004 and 2006 (n = 108,785). Of these, 33.4% (n = 36,331) had at least one repeat EGD within three years of their index EGD. Most likely to undergo a repeat EGD were patients with an index diagnosis of varices (61.0%) and Barretts esophagus (58.5%). However, the absolute contribution of these two diagnoses to all repeat exams was very small (0.5% and 6.5%). Index diagnoses suggesting that a repeat EGD was routinely indicated comprised only 22.6% of repeat exams. In contrast, index diagnoses that did not suggest the need for a repeat EGD comprised 59.9% of repeat exams. Common diagnostic categories in this latter group included gastritis/duodenitis (21.0% of repeat exams), abdominal pain/dyspepsia (9.6%), or nonspecific EGD findings (9.2%). Conclusion: One in three Medicare beneficiaries undergoing an EGD had a repeat EGD within three years. Most of these repeated exams were performed for patients with a diagnosis at index endoscopy that does not imply that a repeat exam would be necessary. These findings raise questions about whether EGD is overutilized, particularly in terms of repetitive exams.

Mo1959 Induced JunD Represses Intestinal Epithelial Cell Proliferation by Increasing MicroRNA-29b After Polyamine Depletion

G A A b st ra ct s (p<0.05). Conclusions: Pediatric AP patients are kept fasting for extended periods of time and the initial diet is typically clear liquids despite the lack of evidence to support this practice. Tolerance of nutrition continues to be monitored by serum lipase levels even though it is known to correlate poorly with disease severity. Pediatric AP patients with more severe disease are more likely to receive PN and spend longer periods fasting. This occurs despite evidence in adults suggesting that early enteral nutrition is associatedwith improved outcomes in severe AP. Because of this discrepancy, there is a need for further research in pediatric AP regarding the potential benefit of EN and its early institution.