By studying the addition of sugars to proteins - a process called glycosylation - in the nervous system of insects, Temple University researcher Karen Palter believes she may be able to better understand neurodegenerative diseases in humans.
Currently, her lab is involved in two collaborative research projects exploring the glycosylation process that could eventually play important roles in producing therapeutic drugs more efficiently and understanding neurodegenerative diseases such as epilepsy and memory loss.
Proteins in higher organisms, from fruit flies to humans, which are secreted or displayed on cell surfaces must have sugars attached to them in order to function properly. This glycosylation process is necessary for protein stability, may modulate protein activity and provides recognition sites on cell surface proteins, which is necessary for cell-to-cell interactions.
The glycosylation process fascinates Palter, an associate professor of biology in Temple's College of Science and Technology, who has been studying its biological roles for the past six years.
One project involves growing insect cells outside of the organism and using them to produce human proteins that can be used therapeutically, such as clotting factors.
“When I first became involved in this project, the objective was a bio-engineering one,” said Palter, a geneticist. “We wanted to produce an insect cell line that basically could produce the exact glycosylation pattern that would occur in humans. Because insect cells are missing the last two steps in the glycosylation process, you can't use them to generate therapeutic proteins, even though they are easier and less expensive to use, compared with mammalian cell lines.”
Palter, who came to Temple in 1988, says the insect cells must be genetically altered to produce human proteins that have a glycosylation pattern typical of human proteins, and not insect proteins; otherwise, the proteins will be destroyed in the liver or recognized as foreign by the immune system.
“When we started, the objective was to look at the genomes of insects, which just started being sequenced, and figure out what glycosylation enzymes they had and what enzymes they were missing so that we could either add on or subtract an enzyme to duplicate the human pathway,” she said.
Palter was intrigued by a paper from Jurgen Roth and his colleagues published in 1992, which reported detecting the complex sugars typical of human proteins in insects, but found they were restricted to the cells of the central nervous system.
“Unfortunately, researchers did not believe or follow up on Roth's initial study,” she said. “However, I became interested in what the role of complex glycosylation might be in the central nervous system. As a geneticist, I thought we could use the sophisticated genetic approaches available in the fruit fly to understand this.”