The Reich Group at the University of California, Santa Barbara’s Department of Chemistry and Biochemistry have developed a new way to use lasers to spatially and temporally control the release of a tagged protein inside a cell.
Researchers used the receptors on prostate cancer cells, which rely on the recognition of a C-end rule internalizing peptide that is fused to the end of a fluorescent protein. The peptide is specific for the receptor, and once met, is able to take in the protein-loaded nanoparticles and engulfs it into the cell through endocytosis, a process that brings large molecules into cells.
“Our goal is to have the protein be very specific and have a high affinity for proteins with polyhistidine tails,” said Morales, the lead author of the paper. “If you synthesize or grow proteins in a lab, we want to be able to easily load the protein into our nanoparticles.”
The team used a modular nickel linking layer on the surface of the nanoparticles that can support different kinds of proteins with a polyhistidine tag, commonly found on proteins expressed in labs.
“You can point the laser at cells where and when you want a particular protein to be turned on,” said Reich. “And that means you can ask biological questions that you could never ask before because you’re able to say ‘I want this one cell to do this.’”
The Reich’s group’s hollow gold nanoshells are effective carriers, but transporting large molecules such as proteins into cells is only half the battle. In order for the protein to be effective in the cell, it must be released from the vesicle holding it. The design of the particles allows this to happen.
“When we excite the nanoshells with light, the surface of the nanoparticle becomes hot, and burn up inside, a process called thermal ablation,” said Morales. “The light releases the cargo that’s on the surface and causes the formation of vapor bubbles and pops the vesicle, allowing for the protein to escape.”
This technology helps open new doors to the field of optogenetics, which uses light to control cellular events. Optogenetics focuses on taking special proteins that are responsive to light and selectively turns neurons on or off with unprecedented precision. Additionally, this technology has a wide range of applicability, such as cancer therapeutics.
“Not only do we have the ability to target with a laser where and when we want to release our therapeutic, but we also have leverage on the protein itself,” said Morales. “We have specificity toward the target and are able to use proteins as a potent therapeutic.”
According to Reich, this technology has important implications for basic research in molecular biology and beyond. The findings appear in the journal Molecular Pharmaceutics.
“Biologists are going to make use of this kind of technology, but they aren’t going to develop it,” said Reich. “There are a few people on campus who could use this technology so we have a unique opportunity at UCSB to be leading in interfacing between developers and the users.”