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Biomedical Sciences Seminar Series

Winter 2007 Poster Presentation

January 26, 2007 at 1 pm
Physical Sciences Lobby
Victor Galvan, Renee Williams, Lucinda Robledo, Marysol Navarro, Grace Masangkay, Carlos Hernandez, Gilson Sanchez, Shandee Dixon, Gilson Sanchez, Marysol Navarro

Poster #1-Renee Williams

Complexation of Aβspecies with Fe3+

Renee T. Williams, Dianlu Jiang, Feimeng Zhou*
Department of Chemistry and Biochemistry
California State University, Los Angeles
5151 State University Drive
Los Angeles, CA 90032 

In collaboration with

Lijie Men and Wang Yishen* 

Department of Chemistry
University of California, Riverside
900 University Avenue
Riverside, CA 92521

Alzheimer’s disease (AD) is a progressive, neurodegenerative disorder characterized by the deposition of amyloid plaque.  The plaque is primarily composed of insoluble beta-amyloid (Aβ) protein fibrils and metals at elevated concentrations.  In a human brain, the neurotoxicity of Aβ plaque has been suggested to originate from a Fenton-like reaction wherein the peptide-metal complex(es) is(are) involved in the generation of  reactive oxygen species.  To date, the majority of studies have focused on Aβ-copper and Aβ-zinc interactions, whereas Aβ-iron complexes have not been extensively investigated.  As such, the objective of this research is to 1) show that an Aβ-iron complex is formed, 2) determine if the complex is redox-active, and 3) establish a binding constant for the complex.  We will correlate our results obtained in vitro to in vivo observations and attempt to provide insight to the understanding of the Aβ aggregation process and its possible link with oxidative stress.

Poster #2-Shandee Dixon

In-vivo Pathogenicity studies of Sendai Virus Reverse Genetics Variants Containing Different Combinations of Mutations in the M and F Genes

Shandee Dixon, Marysol Navarro, Joseph T. Seto and Nancy L. Mc Queen
Department of Biological Sciences,
California State University Los Angeles

Wild-type (wt) Sendai virus causes a localized respiratory tract infection while its variant, F1-R, causes a systemic infection. Two phenotypic differences in F1-R have been correlated with its pantropic phenotype. The first difference is the enhanced cleavability of the fusion (F) protein of F1-R that has been attributed to one or more of the amino acid substitutions in the F protein. The second difference is the microtubule disruption and subsequent bipolar budding of F1-R that has been attributed to two amino acid substitutions in the M protein. We have hypothesized that specific combinations of the amino acid substitutions in the F and M proteins of Sendai are responsible for the pantropic behavior of the virus. To confirm this hypothesis a reverse-genetics viral recovery system was used to generate three variant viruses, RGV-0, RGV-1 and RGV-7. RGV0 has all six F1-R F gene mutations and both F1-R M gene mutations, RGV1 only has one of the F1-R F gene mutations, and RGV7 has the same F1-R F gene mutation as RGV1 plus both of the F1-R M gene mutations.

Intranasal infections were used to test the pathogenicity of the reverse genetics viruses in mice. Wt and F1-R Sendai viruses were used as controls for pneumotropic and pantropic viruses, respectively. Viruses collected from lungs, kidneys, and livers of the infected mice were amplified in 10-day–old embryonating chicken eggs and viruses recovered from the allantoic fluid of the infected eggs were titered using a hemagglutination (HA) assay. Viral RNA recovered from HA positive samples were transcribed into cDNA by means of Reverse-Transcriptase PCR followed by sequencing to confirm that the viruses had the appropriate mutations. The results indicate that wt, RGV1 and RGV7 were all pneumotropic, while F1-R and RGV0 both caused a systemic infection. Based on these studies we can say conclusively that the mutations in genes other than M and F genes of F1-R do not contribute to the systemic infection caused by F1-R. Studies to determine the specific combination of F1-R F and M gene mutations that contribute to F1-R’s ability to cause a systemic infection are underway.

Acknoledgements: Funding for this project was provided by MBRS Score Grant # F06GM8101-32 to N. L. McQueen, NIH MBRS-RISE MS TO PHD Grant # GM 61331 to C. Gutierrez and LSAMP-BDIII NSF Grant # HRD-0331537.


Poster #3- Gilson Sanchez

Bioinformatic and Molecular Biological Approaches to
Identify Id2 Promoter Sequences

Required for Efficient Expression and Down-Regulation
G. J. Sanchez and S. B. Sharp
Department of Biological Sciences
California State University, Los Angeles, CA. 90032


Poster #4- Marysol Navarro

Is the amino acid change at position 104 in the fusion protein of F1-R essential for Sendai virus variant F1-R’s ability to cause a systemic infection?

Marysol Navarro, Joseph T. Seto, and Nancy L. McQueen

Abstract: Sendai virus (SeV) is a murine negative-strand RNA virus. Wild type (wt) virus causes a localized respiratory tract infection in mice. A variant, F1-R, causes a systemic infection. We have identified two determinants that correlate with the systemic infection caused by F1-R. One of these determinants is the enhanced cleavability of the fusion (F) protein of F1-R that we have attributed to two or more of the six mutations in the F gene. Cleavage is required for virus infectivity. Wt F is only cleaved by Tryptase Clara, a protease restricted to the lungs, while F1-R F is cleaved by ubiquitous proteases. Thus, wt Sendai can only undergo multiple rounds of replication in the lungs while F1-R can undergo multiple rounds of replication in many different organs.

The second determinant is the differential budding behavior of F1-R that we have attributed to two mutations in the matrix (M) gene of F1-R. Wild type SeV buds from the apical domain of epithelial cells into the lumen of the respiratory tract where it subsequently infects new cells in the respiratory tract to cause a localized infection. F1-R buds from both the apical and basolateral domains, thus releasing virus into the basement membrane through which it can gain quick access to the bloodstream for dissemination. Based on studies of a revertant of F1-R that has lost its pantropic phenotype, we originally hypothesized that the two mutations in the M gene of F1-R and a mutation in the F gene that results in an amino acid substitution adjacent to the cleavage site of F (F115) were the only mutations needed for F1-R to cause a systemic infection. To test this hypothesis we used reverse genetics to make Sendai viruses with various combinations of the F1-R F and M gene mutations. RGV0 contains all six F1-R F and both M mutations, while RGV1 contains only the F1-R F mutation that encodes F115 and RGV7 contains the F1-R F mutation encoding F115 and both M mutations. Much to our surprise only RGV0 had an F protein with enhanced cleavability and only RGV0 caused a systemic infection in mice. These results mean that in addition to the F1-R F mutation adjacent to the cleavage site of F that had previously been shown to be critical for the systemic infection caused by F1-R, other mutations in F contribute to the enhanced cleavability of F1-R F and the pantropism of F1-R.

Wt F has a glycosylation site at amino acid 104 that is lacking on F1-R F because of an amino acid change at that site. A loss of an oligosaccharide side chain on an influenza virus strain and functional analyses of glycosylation sites on F suggests that fusion activity and cleavability of F is increased when the glycosylation site at F104 is lost. Therefore, my project is to generate a variant SeV, designated RGV18, with the F1-R amino acid changes at F104 and F115, plus both M amino acid changes. The mutant will be studied in both tissue culture and mice to determine its affects both in vitro and in vivo. As a first step in this process I have amplified pRGV7, a cDNA plasmid of SeV that contains the F1-R F mutation encoding F115 and both M mutations. Site directed mutagenesis of pRGV7 was done to introduce a mutation encoding the F1-R amino acid change at F104. The resulting plasmid, pRGV18, still remains to be confirmed through sequencing. If it contains the desired mutation it will subsequently be used to generate the virus, RGV18, and to study its’ in vitro and in vivo pathogenicity.


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