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1 HIV-1 belongs to the genus Lentivirus, a group of retroviruses characterized by their ability to cause long lasting infection and encode nonprototypical accessory genes. The HIV-1 accessory protein Vpu is a small 81-amino-acid (16 kDa), type-I integral membrane phosphoprotein that is unique to HIV-1 and some simian immunodeficiency viruses (SIVs). Structurally, Vpu contains an N-terminal transmembrane (TM) domain along with two cytoplasmic alpha helices that are separated by highly conserved, constitutively phosphorylated serines. To date, Vpu has been shown to antagonize four host proteins: CD4, BST-2, CD1d, and NTB-A. We have recently discovered a novel function of Vpu in the downmodulation of the chemokine receptor CCR7 from the surface of infected CD4+ T cells. Our studies have found Vpu to be both necessary and sufficient for CCR7 surface downregulation. Interestingly, total levels of CCR7 remained unchanged in infected cells, suggesting Vpu sequesters rather than degrades the chemokine receptor. Downregulation of CCR7 from the surface was abrogated when cells were infected with a Vpu TM mutant. In contrast, mutation of Vpu’s 2 conserved serines did not affect CCR7 surface downmodulation by Vpu. Additionally, we found, through coimmunoprecipitation (co-IP) studies, that Vpu specifically interacts with CCR7 and that both proteins preferentially colocalize within the trans golgi network (TGN).
AN EVALUATION OF THE IMPACT OF FECAL MATERIAL FROM CATTLE EGRET (BUBULCUS IBIS)
HERONRIES ON WATER QUALITY IN TEXASJudlyn Telesford, Miguel Mora.
Texas A&M University, College Station, TX.
The impairment of watersheds by pathogens, as indicated by the detection of high levels of Escherichia coli (E.
coli), has been a problem in Texas for many years. Avian species such as Egrets establish large heronries in close proximity to water. To our knowledge, no information is available on the E. coli and nutrient loads contributed to Texas watersheds by these birds. The objective of this study was to determine the direct and indirect impact of heronries on water quality by quantifying E. coli and nutrient loads. A heronry at Murphy Park [MP] was used to study the indirect impact while another at Richland Creek [RC] was used to study the direct impact. Water samples were collected 3 times during the breeding season around MP and beneath RC. E. coli counts in all samples exceeded the criteria for primary contact recreation (126 CFU/100 ml) set by the Texas Commission on Environmental Quality. Nitrogen concentrations at MP ranged from 11,200 to 40,000 mg/l. Phosphorus concentrations were as high as 0.38 mg/l, and dissolved oxygen (DO) was as low as 5.8 mg/l. At Richland Creek, E. coli counts were as high as 230, 000 CFU/100ml and total N concentrations ranged from 12,000 to 66,600 mg/l. DO was as low as 4.5 mg/l. These results have improved our understanding of the potential contribution to Texas watersheds of E. coli and nutrients from heronries and can aid in the development of best management practices and other strategies to address bacterial and nutrient loads in Texas.
IMPROVING PANCREATIC CANCER CHEMOTHERAPY THROUGH THE ADDITION OF COMPOUNDS DERIVED
FROM NEXRUTINE®Amanda Muñoz1, Florastina Payton-Stewart2, Addanki Pratap Kumar1.
University of Texas Health Science Center at San Antonio, San Antonio, TX, 2Xavier University of Louisiana, New 1 Orleans, LA.
Pancreatic cancer (PanCA) is one of the more challenging forms of cancer to treat and, as such, is the fourth leading cause of cancer-associated deaths in the US. Currently, patients diagnosed with PanCA have a 5-year survival rate of less than 10%. Poor drug delivery and effectiveness are 2 factors known to complicate therapeutic strategies in PanCA and contribute to the observed low survival rates. Therefore, we need to improve the current drugs or develop novel therapeutics with greater efficacy to improve patient survival. Our laboratory has focused on improving the
344 ORAL ABSTRACTS
current treatment options by supplementing chemotherapeutics with Nexrutine® (Nx). Nx is an herbal supplement, which has been shown to inhibit PanCA cell growth through modulation of inflammatory signaling pathways. Based on this and preliminary data, we hypothesized that compounds derived from the active components of Nx may induce a synergistic or additive anticancer effect on pancreatic cancer in combination with standard-of-care chemotherapeutic agents. In this presentation, we will identify a derivative that can exert synergistic or additive growth-inhibitory activities in combination with oxaliplatin, gemcitabine, 5-fluorouracil, and paclitaxel. Methods used to obtain our results include cell culture, proliferation assays, combination indices analysis, cell cycle assays, and colony formation assays.
Our results suggest that some of the derivatives examined could potentially be used as an adjuvant or neoadjuvant to chemotherapy regimens in PanCA patients to improve patient survival.
A GENOMICS APPROACH TO UNDERSTANDING THE TOXICITY OF DRINKING WATER CONTAMINANTSVanessa De La Rosa, Jonathan Asfaha, Chris Vulpe.
University of California, Berkeley, Berkeley, CA.
Trichloroethylene (TCE) is an industrial solvent and the most common drinking water contaminant in the US. TCE is a human carcinogen and highly toxic, yet the molecular events mediating toxicity and cancer remain convoluted. We aim to use a functional genomics approach in model organisms to gain insight into the genes and cellular pathways that modulate TCE toxicity. Initial functional studies used the yeast deletion library consisting of 4,600 mutant strains, each with a single gene knocked out. Screening the yeast library with TCE identified a subset of mutagenic DNA repair genes important in the response to TCE. This suggests TCE damages DNA and requires a repair response to mediate toxicity in yeast. Subsequent functional studies were conducted in transformed avian lymphocyte cell lines to determine if TCE DNA damage and the mutagenic DNA repair response were conserved. Various DNA repair knockouts exposed to biologically relevant TCE doses exhibited decreased viability, and biochemical analysis of posttranslational modifications showed initiation of DNA repair during TCE exposure. Results from these functional studies suggest TCE-induced DNA damage and repair response is conserved in higher eukaryotes. Ongoing studies using human cell lines and mass spectrometry will provide physical evidence of DNA damage and further support TCE-induced damage as a modulator of toxicity. In conclusion, these studies have identified previously unknown cellular targets that potentially modulate TCE toxicity and progression of cancer in humans. Furthermore, we show that a functional genomics approach is a viable platform for understanding toxicity mechanisms in higher organisms.
ALTERED GABAERGIC SIGNALING CONTRIBUTES TO AGE-RELATED MEMORY DECLINECristina Banuelos, Sofia Beas, Ryan Gilbert, Barry Setlow, Jennifer Bizon.
University of Florida College of Medicine, Gainesville, FL.
Impairment in working memory functions supported by the prefrontal cortex (PFC) are a common feature of normal aging. Working memory critically involves GABAergic signaling in PFC; yet, surprisingly little is known about GABAergic alterations in PFC during normal aging or whether such changes contribute to age-associated impairments in working memory. To investigate this, young adult (7 mo) and aged (25 mo) male F344 rats were characterized on an operant-based delayed response test of working memory. Rats were required to remember the location of a sample lever over a delay period (0 - 24 s) to obtain a food reward. Aged rats performed comparably to young rats under no-delay conditions, but exhibited deficits relative to young rats at long delays. Immunoblots of PFC homogenates showed that the GABA synthesizing enzyme GAD67 was increased, but the transporter important for reuptake of GABA after synaptic release (GAT-1) was decreased in aged PFC. GABA(B) receptor, GABA(B)R, expression was also reduced in aged PFC and was inversely related to working memory performance among aged rats. We next tested whether reducing GABA(B)R activation could improve working memory in impaired, aged rats.
Systemic injections of CGP55845 (0.1 mg/kg), a GABA(B)R antagonist, enhanced performance in aged rats, and these effects were mimicked by microinjections of CGP55845 into PFC. Together, these data suggest that age-related dysregulation of GABAergic signaling in PFC may play a causal role in impaired working memory and that targeting Graduate Oral GABA(B)Rs may provide therapeutic benefits for age-related impairments in executive functions.
A XENOPUS TADPOLE MODEL FOR VALPROATE-INDUCED NEURODEVELOPMENTAL DISORDERSEric James, Jenny Gu, Arseny Khakhalin, Carlos Aizenman.
Brown University, Providence, RI.
Autism spectrum disorder (ASD) is the most prevalent neurodevelopmental disorder afflicting children. Prenatal exposure to valproic acid (VPA), a commonly prescribed anticonvulsant, increases the risk for ASD in children.
Rodents exposed to VPA in utero have been used to generate a VPA-induced rodent model of autism. The overarching neuronal phenotypes of these “autistic” mice are reduced cell excitability and hyperconnected local networks. However, the mechanisms by which prenatal VPA exposure produces ASD in humans and animal models is not understood. The retinotectal circuit of the Xenopus tadpole is a well-characterized neural circuit that has been used to study mechanisms of neuronal development. We exposed tadpole embryos to 1 mM VPA and tested excitability and connectivity of tectal neurons using whole-cell patch-clamp recordings. The results of exposing tadpoles to VPA during this critical period were a reduction in cell excitability and network hyperexcitability, thus recapitulating neuronal phenotypes of other VPA-induced animal models of ASD. Behavioral research has demonstrated autistic children and VPA-induced models of ASD have an increased sensitivity to sensory stimuli. We conducted behavioral assays on the VPA-treated tadpoles and observed an increased response to sensory stimuli.
Xenopus tadpoles are a high-throughput model organism with well-understood neural organization useful for studying mechanisms that govern development of neural circuits. When these attributes of Xenopus are combined with the results of our experiments, it is clear the Xenopus tadpole is a viable and efficient model to study the mechanisms by which VPA-induced ASD occurs.
RESCUE EFFECTS OF CERAMIDE INHIBITION BY MYRIOCIN IN CHRONIC ALCOHOLIC LIVER DISEASETeresa Ramirez1, Lisa Longato1, Ming Tong2, Valerie Zabala2, Jack Wands1, Suzanne de la Monte1.
Brown University, Providence, RI, 2Rhode Island Hospital, Providence, RI.
1 Alcohol-related liver disease (ALD) causes steatohepatitis with insulin resistance. Insulin resistance impairs hepatocellular growth, survival, and metabolism. Disrupted lipid metabolism leads to increased ceramide accumulation in the liver. Attendant lipotoxicity promotes endoplasmic reticulum (ER) and oxidative stress, which worsen inflammation and insulin resistance. Adult male Long Evans rats were pair-fed with isocaloric liquid diets containing 0% or 37% ethanol (caloric) for 8 weeks. After 3 weeks on the liquid diets, they were intraperitoneally injected with myriocin (0.3 mg/kg) or saline (vehicle) in 100 μl volumes. Myriocin is a serine palmitoyl transferase (de novo pathway) inhibitor that blocks ceramide synthesis. We characterized the effects of myriocin treatment on the histopathological and ultrastructural features of steatohepatitis, biochemical and molecular indices of hepatic steatosis; insulin resistance, signaling through the insulin receptor, insulin receptor substrate (IRS), and Akt pathways;
and ER stress pathway activation. Myriocin reduced the severity of alcohol-related steatohepatitis, including the abundance and sizes of lipid droplets and mitochondria, inflammation, and architectural disruption of the ER. In addition, myriocin-reduced hepatic lipid and ceramide levels were associated with constitutive enhancement of insulin signaling through the insulin receptor and IRS2 and modulation of ER stress signaling mechanisms. Ceramide accumulation in liver mediates tissue injury, insulin resistance, and lipotoxicity in ALD. Reducing hepatic ceramide levels can help restore the structural and functional integrity of the liver in chronic ALD due to amelioration of insulin resistance and ER stress. However, additional measures are needed to protect the liver from alcohol-induced necroinflammatory responses vis-à-vis continued alcohol abuse.
PLANT SCIENCESRoom 207A
TIGHT, INDUCIBLE EXPRESSION OF PATHOGEN EFFECTOR PROTEINS IN RESISTANT PLANTS ACHIEVED
WITH AN ALTERNATIVELY SPLICED SUICIDE EXONTania L. Gonzalez, Brian J. Staskawicz, Ming C. Hammond.
University of California, Berkeley, Berkeley, CA.