Submitted on June 28, 2005
Accepted on October 15, 2005
Quantum Dots conjugated to Bombesin or Angiotensin II Label the cognate G Protein-Coupled Receptor in Living Cells
Steven H Young1 and Enrique Rozengurt1*
1 Medicine, University of California Los Angeles, Los Angeles, CA, USA
* To whom correspondence should be addressed. E-mail: eduerozengurt{at}mednet.ucla.edu.
Quantum dots exhibit high fluorescence and low photobleaching in comparison to organic dyes, properties which should enhance their detection at low densities. In view of the properties of quantum dots and the biological and pharmaceutical importance of G protein-coupled receptors (GPCRs), we attempted to use quantum dots to label GPCRs in a variety of live cell types. Agonist, consisting of biotinylated bombesin or angiotensin II, was conjugated to Qdot® quantum dots coated with streptavidin through a biotin-streptavidin linkage (Qdot-agonist). Here, we demonstrate that Qdot-bombesin can label the bombesin-preferring GPCR in living mouse Swiss 3T3 cells and in Rat-1 cells. Similarly, we used Qdot-angiotensin II to label GPCR in intact rat intestinal epithelial IEC-18 cells and in human pancreatic HPAF II cells. We demonstrate that Qdot-angiotensin II is brighter and more photostable than agonist labeled with an organic dye such as Cy3. Our results demonstrate that Qdot technology can be adapted to monitor ligand binding to GPCRs. Combined with the narrow and symmetric emission profile of Qdots, this suggests a new multiplex strategy to determine the effect of agonists/antagonists on agonist binding to several GPCRs simultaneously in living cells.
