Researchers develop new molecular transporter to bring cargos into algal cells

21 August 2012

Scientists from the US Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and Stanford University have developed a new general molecular method based on guanidinium-rich molecular transporters (GR-MoTrs) for bringing small and large cargos into algal cells. Significantly, this method is shown to work in wild-type algae that have an intact cell wall.

Algae offer the potential for the direct biosynthesis of biofuels, chemical building blocks, vaccines, pharmaceuticals, and other useful compounds. But before scientists learn the best ways to harness the power of algae, they must first gain a better understanding of what happens inside algae cells. They must also learn how to optimize the inner-workings of algae for the production of biofuels and other applications.

This requires slipping molecular-sized cargo inside algae cells to track metabolic changes and the flux of carbon, or to tweak the cell’s energy-producing mechanisms. However, algae cells are protected by a double defense—an outer wall and lipid membrane—that blocks unwanted molecules from getting inside.

Until now, the main way researchers delivered molecules inside algae cells was to use physical processes, such as shooting tiny metal beads coated with DNA at cells. Another approach involves rapidly shaking cells with small glass beads coated with DNA or small molecules. This creates breaks in the cell wall and membrane, which allows the cargo to slip inside. In contrast, the Berkeley Lab technique doesn’t require such potentially damaging and inefficient methods.

We show for the first time that a guanidinium-rich molecular transporter can deliver a variety of cargo in several algae species. The range of uses for this molecular transporter is likely to be very broad. It could offer insights on algae barriers and serve as a new tool for the molecular manipulation and imaging of algae.

—Bahram Parvin, a staff scientist in Berkeley Lab’s Life Sciences Division

The research was led by Berkeley Lab’s Joel Hyman and Stanford University’s Erika Geihe and Brian Tantrow. Parvin and Stanford University’s Paul Wender are the co-corresponding authors of the research, which is described in a recent early edition of the Proceedings of the National Academy of Sciences.

The scientists started with a molecular transporter (also known as a cell-penetrating peptide or protein transduction domain) that features arginine, one of the amino acids found in all proteins. Arginine is in the guanidinium family of organic compounds. For the past several years, Wender’s group has developed ways to deliver drugs and other small molecules into mammalian cells using guanidinium-rich molecular transporters. They and others have also laden transporters with cargo such as metals, imaging agents, and genetic material.

The Berkeley Lab and Stanford University scientists conducted several experiments that showed that guanidinium-rich molecular transporters can cross the cell wall of an algae species called Chlamydomonas reinhardtii, which was chosen because its molecular and genetic traits are well understood. In one experiment, they fastened a protein cargo to the transporter, and found that it too entered the cell. The scientists also showed that the transporter can enter the cells of other algae species including Neochloris oleoabundans and Scenedesmus dimorphus.

The scientists next plan to refine the guanidinium-rich molecular transporter so that it can be used to optimize the energy-production pathways of algae. They’re modifying it so it can deliver genetic cargo, and they’re developing it into a sensitive assay for imaging gene expression. They’d also like to use it as a probe to track changes in algae’s carbon cycle as a result of genetic engineering.

This research was supported in part by the Department of Energy’s Office of Science and the National Institutes of Health.

Resources

• Joel M. Hyman, Erika I. Geihe, Brian M. Trantow, Bahram Parvin, and Paul A. Wender (2012) A molecular method for the delivery of small molecules and proteins across the cell wall of algae using molecular transporters. PNAS 109 (33) 13225-13230 doi: 10.1073/pnas.1202509109