Researchers from the Broad Institute of MIT and Harvard have utilized an advanced single-molecule imaging technique to reveal how certain proteins related to cancer interact within living cells. This method uses stable nanoparticle probes that illuminate single molecules for extended periods. For the first time, the team observed individual receptors on the cell membrane as they interact and disengage to modify cellular signaling.
The study, published in Cell, highlights the technique’s potential to explore various receptors and molecules, enhancing drug screening to better understand therapeutic impacts on living cells. “With our photostable probes, we can map out the entire lifespan of these molecules in their native environment and see things that have never been observable before,” explains Sam Peng, the study’s lead author and a core member at the Broad Institute and assistant professor of chemistry at MIT.
Existing single-molecule tracking contrast agents like dyes suffer from photobleaching, limiting their usefulness. Peng’s lab developed long-lasting upconverting nanoparticles that maintain stable signals under laser light. These nanoparticles contain rare-earth ions that continue to luminesce for extended durations. By modifying the ions, scientists can create probes that emit various colors, enabling multi-target tracking in a single experiment.
In their research, the team focused on the EGFR family of cell receptors, associated with several cancers. Collaborating with Matthew Meyerson and Heidi Greulich from the Broad’s Cancer Program, they aimed to uncover new biological insights into receptor dynamics, such as pairing, duration, and partner selection. They customized nanoparticles to tag EGFR and cancer-related receptors HER2 and HER3, observing their dynamics in living human cells.
Peng’s team found that EGFR receptors could pair and remain dimerized for several minutes when activated, a phenomenon not visible with traditional dyes. Prolonged dimerization may lead to excessive cell growth and cancer. A microscopy video showed nanoparticles tagged to EGFR receptors tracking their dimerization. Mutated EGFR molecules formed more stable dimers, even without external stimuli, explaining how these mutations could lead to uncontrolled cell growth and cancer.
The researchers also discovered new details about HER2 and HER3’s stable pairings, shedding light on their roles in cancer. When tagging all three receptor types in one experiment, they observed a dynamic process of receptors pairing, unpairing, and finding new partners on the cell surface. Beyond understanding EGFR biology, the team hopes their method will inspire new research questions in other scientific fields.
“We think this technique could be transformative for studying molecular biology because it enables dynamic biological processes to be observed with high spatiotemporal resolution over unprecedented timescales,” says Peng. The team plans to further explore the method’s application in studying drug mechanisms and aims to enhance their probes by making them smaller, brighter, and capable of emitting more colors.
Original Source: news.mit.edu
