All ETDs from UAB

Advisory Committee Chair

Harald Sontheimer

Advisory Committee Members

David Bedwell

Kevin Kirk

Burt Nabors

Jacques Wadiche

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Malignant gliomas are the most common and deadly form of primary brain cancer afflicting adults. Current treatment regimens, including surgical debulking, radiotherapy, and chemotherapy, have limited efficacy, and median patient survival remains only 14 months. Therefore, novel therapies must target different aspects of glioma biology. Two of the most striking features of this cancer are the unusual ability of glioma cells to robustly proliferate and migrate in the brain, and recent evidence suggests that ClC-3, a voltage-gated Cl- channel/transporter is implicated in both of these processes. We hypothesize that ClC-3 may facilitate proliferation and migration by promoting hydrodynamic shape and volume changes; as Cl- efflux occurs, water osmotically leaves the cytoplasm. These shape and volume changes are critical as, for example, a glioma cell divides into 2 daughter cells, or migrates through narrow extracellular spaces in the brain. In this dissertation, we assess upstream signaling to determine how ClC-3 is activated in the context of proliferation and migration. Using a combination of biophysical, biochemical, genetic, and imaging techniques, we identify several mechanisms suggesting that Ca2+/calmodulin-dependent protein kinase (CaMKII) regulates ClC-3 activity. We demonstrate that channels or ligands that increase [Ca2+]i also activate CaMKII, leading to downstream ClC-3 activation and promoting proliferation and migration. CaMKII regulation of ClC-3 is required for a critical cytoplasmic condensation checkpoint at the metaphase-anaphase transition, and inhibition of either protein leads to disrupted volume regulation and proliferation. Additionally, we found that bradykinin, a chemotactic peptide, increases glioma cell migration by activating CaMKII-dependent ClC-3 channels. Inhibition of ClC-3 or CaMKII completely blocked bradykinin-induced migration. We propose that CaMKII activation of ClC-3 is a critical mediator of cellular proliferation and migration and should be integrated into preexisting models. We speculate that [Ca2+]i may be a "master regulator" of both proliferation and migration by simultaneously controlling cytoskeletal proteins, kinases, and Ca2+-sensitive ion channels. Finally, our data suggest that targeting Cl- channels or bradykinin receptors on human glioma cells may be a novel therapeutic strategy for the management of malignant gliomas.

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