Creating an Artificial Golgi
Researchers at Rensselaer are engineering an artificial Golgi, an organelle in cells that is involved in the biosynthesis of proteins. The NSF-supported project has two major goalsgaining fundamental understanding of the complex process of glycosylation and developing the ability to synthesize improved pharmaceutical agents based on this process.
Glycosylation is an important operation in which proteins are modified by the attachment of specific carbohydrates before they are sent out of the cell to do their work. The complexity of glycosylation has hindered fundamental understanding of biosynthesis and has made controlled synthesis of essential therapeutic agents difficult and expensive, explains Jonathan Dordick, director of CBIS and the Howard P. Isermann Professor of Chemical and Biological Engineering, who is principal investigator on the project.
To overcome this difficulty, he and co-investigator Robert Linhardt, the Ann and John H. Broadbent Jr. ’59 Senior Constellation Professor of Biocatalysis and Metabolic Engineering, are creating a digital microfluidic system, a new class of lab-on-chip, that can perform the controlled biocatalytic synthesis of heparin sulfate/heparin, a process that normally would be done in the Golgi.
To create this system, up to 100,000 tiny gold squares are placed on a chip the size of a dime. Nanodroplets carry components found naturally in the Golgi, those raw materials and enzymes that are responsible for the processing and packaging of the heparin compound. Computer-controlled electronics allow the droplets to be physically manipulated around the chip.
Factors like sequence and timing can be controlled, as can specific amounts or combinations of components. “Simulating control points will allow new hypotheses to be tested,” says Linhardt. “And it will allow new ways of testing those hypotheses.”
The artificial Golgi project builds on knowledge both Dordick and Linhardt have built through a number of ongoing NIH-funded research projects.
Linhardt studies carbohydrates and is interested in how carbohydrate attachments to proteins fine-tune their function. He currently has an NIH grant to sequence the polysaccharide component of carbohydrate-carrying proteins. These proteoglycans play an important role in a variety of diseases, including cancer and diseases associated with aging. While most current research concentrates on the proteins, Linhardt is developing a new approach to greatly elevate understanding of the carbohydrates. He also has NIH funding to build libraries of carbohydrates that occur in microbes and are involved in many infectious diseases.
Dordick’s research is focused on biocatalysis, the use of enzymes as catalysts to get from one compound to another. He has created the MetaChip for screening drug toxicity, particularly toxic breakdown products that are formed when the enzymes of the liver metabolize the drugs.
He has NIH funding to use high-throughput biocatalysis methods to optimize compounds as new drug candidates. In another NIH-funded project, he is developing enzyme-nanomaterial-polymeric composites to coat teeth and dental implants to protect them from the formation of dental plaque. He also is supported by NIH to study apocynin, one of the polyphenols found in fruits and vegetables, olive oil, red wine, and tea. He is looking at both its chemical structure and the process by which it disrupts specific protein-protein interactions thought to be involved in vascular diseases, information that is expected to shed light on how polyphenols inhibit disease-causing reactions.