Nucleotide-Dependent Preferential Localization of Ras in Model Membranes with Lipid Raft Nanodomains

Author

Anna Shishina, Marquette University

Date of Award

Fall 2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Kovriguine, Evgueni

Second Advisor

Rathore, Rajendra

Third Advisor

Kincaid, James R.

Abstract

Membrane proteins constitute a third of all proteins in the cell and more than 50% of drug targets. However, the analysis of membrane proteins has many challenges owing to their partially hydrophobic surfaces, flexibility and lack of stability. One example of an essential membrane protein is Ras superfamily. Ras is a small monomeric GTPase involved in regulation of cell growth, proliferation and differentiation. Therefore, Ras and its effectors are among the most important targets for cancer therapy. A detailed knowledge of the processes occurring during signal propagation via Ras might help to elucidate the mechanisms of the involved signal cascades. The preparation of lipid-modified Ras proteins and their study in the presence of the lipid membrane mimic is the subject of this work. Here we investigate the Ras interaction with lipids in isolation from a possible modulation by other cellular membrane proteins. In our study we focus on a property of Ras that it does not act as an ordinary membrane protein, which stays anchored at the same lipid domain throughout its lifetime. Instead, Ras is capable of moving between raft and disordered lipid domains during its functional cycle. It is suggested that Ras binds to some membrane proteins, and thus changes its localization. We have demonstrated that Ras molecule directly recognizes lipid domains, and its binding affinity depends on the activation state of Ras. The results of this work contribute to the further elucidation of the mechanisms of tumorogenesis [sic] and may provide new starting points for further developments in cancer therapy.