Semester

Spring

Date of Graduation

2010

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Microbiology, Immunology, and Cell Biology

Committee Chair

Steven Frisch

Abstract

Anoikis is a subset of apoptosis, suppressed by cell-extracellular matrix association. It is a safeguard mechanism against tumor metastasis. The present study was designed to understand the role of cortical cytoskeletal protein ankyrin-G and its interacting proteins in anoikis. E-cadherin and ankyrin-G are function partners and during epithelial-mesenchymal-transition (EMT), both gets downregulated. During cell-extracellular matrix dissociation, ankyrin-G shifts to cytoplasm from cytoskeleton and loses spectrin interaction. Overexpression of ankyrin-G induced apoptosis in death domain dependent manner, promoted by the presence of ankyrin-G death domain interacting partner, RIP1 (Receptor Interacting Protein with death domain). Ankyrin-G also interacted with a MAGE family protein NRAGE (Neurotrophin Receptor Interacting mAGE protein), which suppressed ankyrin-G induced apoptosis.;NRAGE suppressed anoikis and promoted anchorage independent growth. It was also upregulated in the cells which have undergone EMT as well as in various other tumor types. The oncogenic transcription repressor TBX2 (T-Box Protein) interacted with NRAGE and co-operated functionally in anoikis suppression and anchorage independent growth. Ankyrin-G sequestered NRAGE in cytoplasm and counteracted NRAGE mediated transcription activity. NRAGE also affected E-cadherin mediated adherens junction kinetics and activated pro-survival signaling in cells dissociated from extracellular matrix.;We report a novel pathway, controlled by E-cadherin and ankyrin-G, sequestering NRAGE in cytoplasm in epithelial cells. During EMT, loss of E-cadherin and ankyrin-G promotes NRAGE localization to nucleus. NRAGE co-operates with TBX2 in suppressing anoikis and promoting anchorage independent growth.

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