Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

Browse

Filters

20152

Settings

Subject: search.filters.subject.Bcl-2

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    THE POTENTIAL DICHOTOMOUS ROLE OF ACTIVATING TRANSCRIPTION FACTOR 3 (ATF3) IN COLON CANCER
    (2015) Jiang, Xiaojing; Lee, Seong-Ho; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Colorectal cancer (CRC) is the third leading cause of cancer-related death in the United States. During the tumorigenesis and metastasis of CRC, cells encounter numerous cellular and molecular events. ATF3, a member of the ATF/CREB transcription factor family, plays an important role on regulation of apoptosis and is regarded as a potential molecular target for chemoprevention and chemotherapy of colon cancer. The current study was performed to investigate cellular and molecular mechanisms by which ATF3 affects colon cancer-related phenotypes including apoptosis and metastasis. Here, we demonstrated that knockdown of ATF3 using small interfering RNA (siRNA) promotes the expression of anti-apoptotic protein, B-cell lymphoma 2 (Bcl-2), in colon cancer cells, while overexpression of ATF3 resulted in a dramatic decrease in Bcl-2 protein. Gain of function of ATF3 in colon cancer cell line HCT116 led to an increase of pro-apoptotic protein Bcl-2 homologous antagonist killer (Bak), followed by the induction of apoptosis. Furthermore, we observed that ATF3 overexpression downregulated expression of epithelial-mesenchymal transition (EMT)-related transcription factors. However, mammosphere forming assay indicated that ATF3 overexpressed colon cancer cells form larger and more budding sites compared to control, which is associated with an increase of cluster of differentiation 44 (CD44) expression and a decrease of retinoblastoma (Rb) and tight junction protein zonula occludens (ZO)-1. This study suggested that ATF3 may play a dichotomous role in regulation of apoptosis and metastasis in colon cancer.
  • Thumbnail Image
    Item
    BIOPHYSICAL STUDIES OF THE MECHANISM OF CERAMIDE CHANNEL DESTABLIZATION BY BCL-XL IN APOPTOSIS AND THE USE OF RECTIFICATION TO PROBE THE STRUCTURE AND DYNAMICS OF A NOVEL ESCHERICHIA COLI CHANNEL
    (2015) Chang, Kai-Ti; Colombini, Marco; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Ceramide forms a novel type of channel in the mitochondrial outer membrane and these channels are involved the release of intermembrane space proteins from mitochondria, a decision-making step in the apoptotic process. An antiapoptotic protein, Bcl-xL, regulates the apoptotic process and inhibits the formation of ceramide channels. However, there is no precedent to indicate how a protein regulates a lipid channel. We investigated the mechanism of this regulation and identified the hydrophobic groove of the Bcl-xL as the binding site by which Bcl-xL binds to the channel. This was demonstrated by using a combination of experimental and modeling methods, including site-directed mutagenesis, a fluorescence quenching assay, a mitochondrial outer membrane permeability assay, and molecular dynamic simulations. Interestingly, the hydrophobic groove serves to inhibit another channel former, Bax. We found that the binding sites for Bax and ceramide on Bcl-xL are distinct but overlapping. We used that fact to generate mutants that have differential abilities to inhibit one or the other of these channels. These are useful because although ceramide is important in apoptosis, it is still controversial that whether ceramide channels result in apoptosis in vivo. To probe the relative importance of these two channels in apoptosis, Bcl-xL mutant proteins were expressed in Bcl-xL deficient cells. Weakening the inhibitory potency of Bcl-xL on either Bax or ceramide channels resulted in cells being more sensitive to the induction of apoptosis. This is the first evidence for the role of ceramide channels in the apoptotic process in vivo. In a separate investigation, a novel voltage-gated channel unit was found in E. coli extracts. The unit is consistent with three channels forming the functional triplet. These channels are highly voltage gated and highly cooperative. Those results indicated that one of the channels is oriented in an antiparallel fashion compared to the rest. This arrangement is very rare in protein channels. Rectification of the current flowing through the channels was used to identify the orientation of the channels to provide evidence for or against the antiparallel hypothesis. The results favor the antiparallel hypothesis but also reveal an unexpected asymmetry in the transmembrane electrostatics.