WHU-Pharm Project Description
Tumor cells are characterized by their high growth and poliferation rate. Because of this, they need to consume much more glucose as a source of energy. While blood glucose concentration stays stable under normal circumastances, tissues invaded by tumor cells could show a decreased level of glucose concentration. The difference of glucose concentration provides us a promising way to discriminate tumor cells from normal cells.
Once low concentration of glucose is detected, it would be good if the “sensor” could take action to destroy the tumor cells. To achieve this, we plan to combine the glucose sensor with a liposome, which contains the enzymes and genes needed to de novo synthesize a certain anti-tumor drug.
Our goal is to build a sensor that acts as a switch, adjusting the expression level of the gene that codes for the drug. The lac operon in E.coli gave us inspiration. E.coli use lactose as a source of energy only when glucose is absent. When glucose and lactose both exist, glucose is prefered while lactose is not consumed. This selection is achieved by a protein called cAMP responding protein (CRP) or cAMP receptor protein (CAP) which can bind cAMP. When there is sufficient glucose in the environment, there is enough energy for ATP synthesis, hence cAMP level remains low. Similarly, cAMP level is high when there glucose concentration is low. When cAMP binds to CRP, the activated CRP binds to upstream of the operon, allowing downstream gene to transcribe.
We used part Bba_J04450 to construct the glucose sensor. Bba_J04450 is a part with CRP binding site and a red flourescent protein (RFP) coding sequence. The RFP could be used as a reporter to reflect expression level. When exposed to environments with different glucose concentration, the RFP gene is expressed at different level. By measruing the fluorescent intensity, we can quantify the relationship between glucose concentration and expression level.