Scientists who developed a technology for identifying and targeting unique protein receptor ZIP Codes on the cellular surface have found a way to penetrate the outer membrane and deliver engineered particles - called iPhage - to organelles inside the cell.
In a paper published today online in Nature Communications, the team led by researchers at The University of Texas MD Anderson Cancer Center reports packaging the phage particles with a peptide called penetratin to reach inside the cell.
This new capacity was used to screen for peptide ligands - binding agents - that connect to receptors on mitochondria, which generate a cell's energy, and ribosomes, which process mRNA to make proteins.
The team found a peptide that binds to a specific ribosomal protein called RPL29 which, when delivered with penetratin, disrupts ribosomal function and kills cells. Cell survival was reduced in both malignant and non-malignant cells and in both mouse and human cell lines.
"We provided proof-of-concept for a direct intracellular ligand-receptor screening technology, which is clearly an unmet need in cancer biology, along with the discovery of an organelle ZIP Code that mediates cell death," said Renata Pasqualini, Ph.D., co-senior author of the paper and a professor in MD Anderson's David H. Koch Center for Applied Research of Genitourinary Cancers.
The RPL29 pathway is a new cell death pathway. The researchers found evidence of three types of cell death caused by disrupting the pathway with the new ligand.
"The molecular tool reported here along with its future ramifications will hopefully be of interest to targeted drug development, gene delivery, and mechanisms of human organelle diseases," said Wadih Arap, M.D., Ph.D., also of the Koch Center.
The iPhage screens for ligands inside the cell
Arap and Pasqualini pioneered a screening technique that exploits the existence of unique ZIP Codes in the vascular system to identify molecular targets and the ligands that can be used to selectively hit them.
They developed engineered viral particles, called phage, and packaged them with massive peptide libraries. When injected, these phage/peptide combinations bind to specific receptors in the blood vessels and organs. Cells are then fractionated and analyzed to discover which ligands bind to specific surface proteins.
Arap, Pasqualini and their colleagues have a number of targeted drugs in various stages of development based on screening and then delivery with the combinatorial particles.
The team wondered whether packaging the particles with penetratin, which is known to cross membranes without requiring a cellular receptor, would allow their technology to work inside of cells. "Penetratin makes a little bubble on the cell surface and the bubble goes in through the membrane," Arap said.They dubbed the combination of penetratin and phage particles "internalizing phage," or iPhage. In a series of experiments, the team found:
iPhage successfully entered normal and malignant cells in both mouse and human cell lines while the engineered phage alone, or phage packaged with mutated penetratin, did not gain entry.Connecting iPhage with the mitochondria localization signal (MLS) peptide resulted in a 10-fold concentration of MLS-iPhage in mitochondria compared to simple iPhage, showing that specific organelles could be targeted.
To screen for new ligands that might target specific organelles, they attached a random peptide library to iPhage particles and treated the KS1767 cells. Subsequent analysis found the peptide that binds to RPL29.
Packaged with penetratin, this "internalizing homing peptide" with the ungainly name YKWYYRGAA killed 75 percent of cells in culture while the peptide alone or penetratin alone killed virtually none.
Signs of apoptotic, autophagic and necrotic cell death were found with electron microscopy in cells killed by the YKWYYRGAA-penetratin combination.
Future studies will be needed to understand the complex cell death mechanism caused by the combination.
The study was funded by grants from the National Institutes of Health, the National Cancer Institute, the U.S. Department of Defense, by awards from AngelWorks, the Gilson-Longenbaugh Foundation, the Marcus Foundation, Inc., and MD Anderson's Odyssey Scholar program.
The University of Texas System, Arap and Pasqualini have equity in Alvos Therapeutics and Ablaris Therapeutics, MD Anderson manages and monitors these arrangements in accordance with its conflict-of-interest policy.
Co-authors with Arap and Pasqualini are co-first author Roberto Rangel and Liliana Guzman-Rojas, Fernanda Staquicini, Hitomi Hosoya, E. Magda Barbu, Michael Ozawa, Jing Nie and Erkki Koivunen, all of MD Anderson's Koch Center; Lucia le Roux and Juri Gelovani of MD Anderson's Department of Experimental Diagnostic Imaging; Kenneth Dunner Jr. and Robert Langley of MD Anderson's Department of Cancer Biology; E. Helene Sage of the Benaroya Research Institute at Virginia Mason in Seattle; Roy Lobb of Alvos Therapeutics, Waltham, Mass.; and Richard Sidman of Harvard Medical School and Beth Israel-Deaconess Medical Center in Boston.
Scott Merville | EurekAlert!
Cells communicate in a dynamic code
19.02.2018 | California Institute of Technology
Studying mitosis' structure to understand the inside of cancer cells
19.02.2018 | Biophysical Society
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Materials Sciences
19.02.2018 | Materials Sciences
19.02.2018 | Life Sciences