EMORY  UNIVERSITY

           

 

Office of Postdoctoral Education,

School of Medicine                                                                                   

    http://www.med.emory.edu/postdoc/

 

 

1643 Pierce Drive, Room 307

Atlanta, GA 30322

Phone: (404)-727-3302

 

 

Poster Awards

 

               Poster category

          Award

Biochemistry/Molecular Biology

Yanhua Wang

Cancer Biology

Srinivasa Datla

Cell Biology

Taro Hitosugi

Diseases and Systems & Public Health

Jeffrey Handy

Infectious Diseases

Vijayakumar Velu

Neurosciences

Daniel Moreno De Luca

 
 
 
Congratulations!!!
 
 

Epac Regulation of Urea Transport and the UT-A1 Urea Transporter in Rat Inner Medullary Collecting Duct

Yanhua Wang, Janet D. Klein, Christopher F. Martin, Kimilia J. Kent, Susan M. Wall, and Jeff M. Sands

Mentor: Jeff M. Sands, MD

Department: Medicine/Renal

Urea plays a critical role in the urinary concentrating mechanism, and therefore, in the regulation of water balance. Vasopressin, acting through cAMP, stimulates urea transport across perfused rat terminal inner medullary collecting ducts (IMCD) by increasing UT-A1 phosphorylation and apical plasma membrane accumulation. Cyclic AMP is traditionally thought to act through protein kinase A (PKA). However, cAMP can also activate Epac (exchange protein activated by cAMP). In this study, we tested whether Epac is involved in regulation of urea transport and UT-A1 transporter activity in rat IMCD. Functional analysis showed that the Epac activator, Sp-8-pCPT-2 O-Me-cAMPS, significantly increased urea permeability in isolated, perfused rat terminal IMCDs by 29%. Incubation of rat IMCD suspensions with the Epac activator significantly increased the accumulation of UT-A1 in the plasma membrane (biotinylated UT-A1) and UT-A1 phosphorylation. The Epac activator is specific for Epac as it did not increase the abundance of phopho-CREB. To further explore the signaling pathway, we tested whether forskolin could stimulate ERK 1/2 phosphorylation. Forskolin significantly increased ERK 1/2 phosphorylation by 25%; this increase was not inhibited by a PKA inhibitor, H-89, indicating that forskolin-stimulation of ERK 1/2 phosphorylation was through Epac and not PKA. The MEK 1/2 inhibitor, U0126, inhibited forskolin-stimulated UT-A1 phosphorylation. We conclude that activation of Epac increases urea transport, UT-A1 phosphorylation, and UT-A1 plasma membrane accumulation. The increase in UT-A1 phosphorylation is mediated by the MEK-ERK pathway.

 

 

NOX4 Interactive Protein, NOXR1, Inhibits Vascular Smooth Muscle Cell Migration by Affecting the Focal Adhesion Turnover

Srinivasa Raju Datla, Alicia N Lyle and Kathy K Griendling

Mentor: Kathy K Griendling, PhD

Department: Medicine/Cardiology

NADPH oxidase derived reactive oxygen species contribute to vascular smooth muscles cell (VSMC) physiology and the pathogenesis of vascular disease. We recently identified NOXR1 as a positive regulator of NOX4 in VSMCs and our previous results suggest that NOXR1 is involved in VSMC migration. In this study, we further investigate the role of NOXR1 in VSMC migration and focal adhesion turnover. In a wound healing assay, the migratory phenotypic changes typically exhibited by cells at the front edge of the wound, such as lamellipodia extension, are inhibited by NOXR1 overexpression. siNOXR1 treatment abolishes Tyr-microtubules and focal adhesion structures, as exhibited by the loss of the focal adhesion markers phospho-FAK (FAKpY397), vinculin, and paxillin (visualized by immunocytochemistry (ICC)). To investigate the role of NOXR1 in focal adhesion turnover, we tested the effects of NOXR1 overexpression on Nocodazole-induced microtubule-dependent focal adhesion dissolution and reformation. Nocodazole treatment (10 μM) completely depolymerizes microtubules after 4 hr and, when it is replaced with fresh serum free medium, the Tyr-microtubules begin to re-polymerize within 15 min and completely re-establish by 30 min. This causes a loss of focal adhesions structures at 30 min, which are reformed by 60 min. As measured by ICC for FAKpY397, paxillin, and vinculin, NOXR1 overexpression blocks this focal adhesion turnover and prevents the accompanying decrease in RhoA activity observed at 30 min in control cells. In western blot studies, Nocodazole washout significantly reduces the levels of FAKpY397 in a time dependent manner in control cells (26.71 ± 5.8% decrease at 30 min, P<0.01), and this effect is attenuated by NOXR1 overexpression. Conversely, siNOXR1 treatment significantly reduces paxillin expression (50.27 ± 8.28%, P<0.05). Taken together, these results implicate a role for NOXR1 in focal adhesion turnover and, thus, VSMC migration. Our findings identify a role for NOXR1/NOX4 in the regulation of cytoskeletal dynamics in VSMCs and potentially identify a new therapeutic target for vascular pathologies with a significant migratory component.

 

 

Tyrosine Phosphorylation Inhibits PKM2 to Promote Aerobic Glycolysis and Tumour Growth

 

Taro Hitosugi1, Sumin Kang1, Shannon Elf1, Katherine Lythgoe1, Tae-Wook Chung1, Shaozhong Dong1, Sagar Lonial1, Xu Wang1, Georgia Z. Chen1, Jianxin Xie2, Ting-Lei Gu2, Roberto D. Polakiewicz2, Johannes L. Roesel3, Titus J. Boggon4, D. Gary Gilliland5, Lewis C. Cantley6, Jonathan Kaufman1, and Jing Chen1

1 Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 2Cell Signaling Technology, Inc. (CST), Danvers, MA, 3Novartis Pharma AG, Basel, Switzerland, 4Department of Pharmacology, Yale University School of Medicine, New Haven, CT, 5Howard Hughes Medical Institute, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, 6Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA

Mentor: Jing Chen, PhD

Department: Hematology/Medical Oncology

The Warburg effect describes a pro-oncogenic metabolism switch that cancer cells take up more glucose than normal tissue, yet use less glucose for oxidative phosphorylation and favor glycolysis even in the presence of oxygen (aerobic glycolysis). However, the molecular mechanisms underlying the Warburg effect remain unclear. We performed phospho-proteomics studies to better understand how tyrosine kinase signaling, commonly upregulated in tumours, regulates the Warburg effect to contribute to tumourigenesis and tumour growth. We found that oncogenic FGFR1 phosphorylates and inhibits pyruvate kinase M2 isoform (PKM2). Recent seminal studies from Christofk et al have demonstrated that the enzymatic activity of PKM2 is inhibited by phosphotyrosine binding and the subsequent release of its activator fructose-1,6-bisphosphate (FBP). PKM2 expression is important for aerobic glycolysis and provides a growth advantage to tumours. However, it remains unclear which dedicated tyrosine kinase pathways are physiologically responsible for this regulation and whether PKM2 itself is tyrosine phosphorylated to achieve inhibition of PKM2 in cancer cells. Here we report that FGFR1 inhibits PKM2 by direct phosphorylation at Y105. This consequently disrupts cofactor FBP binding to PKM2 in a putative "inter-molecule manner", where one sister molecule in the inactive PKM2 dimer, when phosphorylated, may function as an inhibitory binding partner to the other. Moreover, phosphorylation of PKM2 Y105 is common in many human cancer cells. Expression of the PKM2 Y105F mutant in cancer cells following RNAi-mediated knockdown of endogenous PKM2 leads to decreased cell proliferation under hypoxia, increased oxidative phosphorylation with reduced lactate production, and reduced tumour growth in xenograft nude mice. Together, tyrosine phosphorylation regulates PKM2 to programme cancer cell metabolism and promote tumour growth. This may represent a common, acute molecular mechanism to regulate the Warburg effect, in addition to the chronic changes that are believed to be regulated by hypoxia inducible factor 1 and Myc.

Source of funding for Research: N.I.H. RO1 grant and ACS

 

 

Adiponectin Mitigates Leptin-Induced Hepatic Fibrosis via Induction of Suppressors of Cytokine Signaling-3 (SOCS-3)

 

Jeffrey A. Handy1, Pingping Fu1, Jamie E. Mells2, Nitika Arora Gupta3, Neeraj K. Saxena1,4, and Frank A. Anania1

 

1Division of Digestive Diseases, Emory University School of Medicine, Atlanta, GA,2Emory University Graduate Division Biological and Biomedical Sciences, Atlanta, GA,3Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, 4Department of Hematology and Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA

 

Mentor: Frank Anania, MD

 

Department: Medicine/Digestive Diseases

 

Adiponectin is an adipokine that was recently shown to be anti-fibrogenic in the pathogenesis of hepatic fibrosis. Leptin, on the other hand, promotes hepatic fibrosis. The purpose of this study was to elucidate a mechanism whereby adiponectin dampens leptin signaling in hepatic stellate cells (HSC), and prevents excess extracellular matrix production. Culture-activated rat HSCs were exposed to recombinant human adiponectin and recombinant leptin. Immunoblot analysis for TIMP-1, SOCS-3 and the phosphorylated species of Stat3 and AMPK were conducted. We also examined MMP-1 activity by ELISA. In HSCs, adiponectin induced phosphorylation of AMPK, and subsequently suppressed leptin-mediated Stat3 phosphorylation. Adiponectin also blocked leptin-mediated induction of TIMP-1, and significantly increased MMP-1 activity, in vitro. To extend this study, we also treated Adiponectin knock-out mice (Ad-/-) daily with 5 mg/kg recombinant leptin and/or carbon tetrachloride (2 ml/kg) for six weeks. Post-necropsy analysis was performed to examine for inflammation, and histologic changes in the Ad -/- and wild-type mice. There was no significant difference in inflammation or aminotransferases between mice receiving carbon tetrachloride and leptin vs. carbon tetrachloride alone. As anticipated, the combination of leptin and CCl4 enhanced hepatic fibrosis, quantified by amount of collagen in injured livers. Livers from wild-type mice exposed to both CCl4 and leptin had significantly higher levels of SOCS-3 mRNA and protein than did livers from similarly treated adiponectin knockout mice; however, livers from leptin/CCL4-treated wild-type mice also had significantly lower TIMP-1 mRNA and protein levels than similarly treated adiponectin knockout mice. We therefore conclude that adiponectin mitigates liver fibrosis by downregulation of the Jak-Stat signal transduction pathway by activation of AMPK and subsequent activation of SOCS-3.

 

 

Enhancing SIV-Specific Immunity in Vivo by PD-1 Blockade

 

Vijayakumar Velu1, Kehmia Titanji1, Baogong Zhu2, Sajid Husain1, Annette Pladevega1, Lilin Lai1, Thomas H. Vanderford3, Lakshmi Chennareddi1, Guido Silvestri3, Gordon J. Freeman2, Rafi Ahmed1, Rama Rao Amara1

 

1Emory Vaccine Center, Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, GA, 2Harvard Medical School, Boston, MA, 3University of Pennsylvania, Philadelphia, PA.

 

Mentor: Rama Rao Amara, PhD

 

Department: Microbiology and Immunology

 

Chronic immunodeficiency virus infections are characterized by dysfunctional cellular and humoral antiviral immune responses. As such, immune modulatory therapies that enhance and/or restore the function of virus-specific immunity may protect from disease progression. Here, we investigate the safety and immune restoration potential of the blockade of co-inhibitory receptor programmed death-1 (PD-1) during chronic SIV infection in macaques. We demonstrate that PD-1 blockade using an antibody to PD-1 is well tolerated and results in rapid expansion of virus-specific CD8 T cells with improved functional quality. This enhanced T cell immunity was seen in the blood and also in the gut, a major reservoir of SIV infection. PD-1 blockade also resulted in proliferation of memory B cells and increases in SIV envelope-specific antibody. These improved immune responses were associated with significant reductions in plasma viral load and also prolonged the survival of SIV-infected macaques. Impressively, blockade was effective during the early (wk10) as well as late (~wk90) phases of chronic infection even under conditions of severe lymphopenia. These results demonstrate enhancement of both cellular and humoral immune responses during a pathogenic immunodeficiency virus infection by blocking a single inhibitory pathway and identify a novel therapeutic approach for HIV/AIDS.

 

Source of Funding for Research: NIH R01AI074417, FNIH P51RR00165

 

 

Recurrent 17q12 Deletions Identified in Autism Males

 

D. Moreno De Luca1, M. R. Rossi1, M. Adam1, A. Pakula2, S. M. Myers3, Kim Uhas1,

L. Weik4, L. Guy2, S. Aradhya5, C. L. Martin1, D. H. Ledbetter1

 

1Emory University School of Medicine, Atlanta, GA, 2Marcus Autism Center, Atlanta, GA, 3Geisinger Medical Center, Danville, PA, 4Children’s Hospital of Wisconsin, Milwaukee, WI, 5GeneDx, Gaithersburg, MD

 

Mentors: David Ledbetter, PhD and Christa. L. Martin, PhD, FACMG

 

Department: Human Genetics

 

A new, recurrent microdeletion of 17q12 (del 17q12) was recently reported in association with renal disease (in pediatric patients and a stillbirth) or diabetes in patients with maturity-onset diabetes of the young type 5 (MODY5). The deletion is 1.5 Mb in size, is mediated by flanking segmental duplications, and contains the TCF2 gene responsible for the autosomal dominant MODY5 form of diabetes. Initial reports indicated that this microdeletion was not associated with mental retardation and no features of autism disorders were noted. We analyzed a subset of 7752 patients from a consortium of clinical cytogenetics laboratories (ISCA, or International Standard Cytogenomic Array consortium), which has performed clinical testing by whole genome, oligonucleotide aCGH in over 15,000 patients, approximately 20% of whom have a primary indication of autism or autism spectrum disorder (ASD). We identified three males and one female, age 4, 7, 12 and 1, with the same ~1.5 Mb deletion of 17q12 as recently reported in renal disease or diabetes. All three males were referred for aCGH testing with a primary indication of autism, and the female was referred for developmental delay. Additionally, all patients share phenotypic features such as macrocephaly, onychodystrophy, and different degrees of renal anomalies, and none of them show signs of diabetes to date. Parental testing has been completed in 3 individuals and demonstrated that the deletion was de novo. This region of proximal 17q overlaps with an autism linkage peak identified in multiple studies, predominantly associated with “male-only” families (i.e., families in whom all affected individuals are males), strongly suggesting a sexspecific risk allele for autism. Interestingly, all three of our male patients had autism. These data raise the possibility that the 17q12 microdeletion may be associated with an increased risk of autism, especially in males.