The Pendergast Lab, in which I am working this summer, broadly studies the Abelson family of non-receptor tyrosine kinases. Tyrosine kinases are a subclass of protein kinase, molecules which phosphorylate proteins. In the case of tyrosine kinases, the phosphate group is attached to a tyrosine amino acid in the target protein’s chain. This phosphorylation activates or deactivates the target protein, enabling or preventing its function.
Abelson kinases, encoded by the genes Abl1 and Abl2, are important molecules in a wide range of cell signaling pathways. Abl kinases are highly expressed in a range of cancers cell lines, suggesting that the pathways in which they are involved play a significant role in tumor development. The Pendergast Lab’s research focuses on mapping out these pathways, and the way in which Abl kinases function within them. My mentor is currently researching a number of metabolic pathways in which Abl kinases are potentially involved, and my project focuses on a protein involved in one of these pathways.
The protein, encoded by the gene SLC7A11, is called system xCT. It is an antiporter, a membrane transporter protein which simultaneously imports cystine and exports glutamate. Cystine is an important molecule in the cell’s response to oxidative stress, the cellular damage caused by reactive oxygen species. Recent studies have suggested that oxidative stress inhibits tumor growth, and cancer cells therefore depend on antioxidant response pathways such as the one involving xCT. Blocking this pathway and thereby leaving cancer cells exposed to the tumor-inhibiting influence of oxidative stress may be therapeutically useful. I will investigate the hypothesis that Abl kinases play a role in the activation of xCT expression.
I will begin by inhibiting Abl kinases, using the allosteric inhibitor GNF5, and observing the effect on cellular levels of xCT. I will measure the effect at the protein level using Western Blotting, and also at the mRNA level using RTPCR. A decrease in xCT upon Abl inhibition would suggest that the kinases are indeed somehow involved in increasing xCT expression or activation. Further experiments would be required to determine the pathway through which Abl kinases increase the expression or function of xCT, and the other molecules involved in this pathway.
As I have started to learn, scientific hypothesis are not always validated. If early results do not correspond to our hypothesis regarding Abl and xCT, I may have to change the focus of my project. However, the process of designing models and experiments to test one’s hypotheses is itself incredibly rewarding, and a good understanding of this process is ultimately more important than individual results.