Researchers from Purdue University and Kyoto University in Japan have shown for the first time that proteins similar to multi-drug resistant proteins in humans move a plant growth hormone into cells, said Purdue plant cell biologist Angus Murphy. Because plant proteins called P-glycoproteins (PGPs) are closely related to human P-glycoproteins that impact chemotherapy effectiveness, discovery of methods to control the plant protein's activity may aid in development of therapies to reduce drug dosages administered to cancer patients, Murphy said.
"Results of this research will give us a better idea of the functioning of the multi-drug resistance process in which human cancer cells reject anticancer treatments," Murphy said. Results of the two studies suggest a previously unknown relationship between two protein families involved in this process, he said. Working together, the proteins apparently move molecules of the plant growth hormone auxin through cell walls. In humans, related proteins rid cells of toxins such as cancer drugs.
"The findings of these two studies have important implications for biomedicine because we now can identify the parts of these proteins that determine whether cells take up or throw off different molecules, such as cancer drugs," Murphy said.
In the Plant Journal study, Murphy and his collaborators at the University of Zurich showed for first time that PGP1, a P-glycoprotein from the commonly used experimental plant Arabidopsis, directly transports auxin out of plant cells and also out of yeast and mammalian cells. In the Plant Cell study, they found that other PGP proteins move auxin into cells. "Auxin molecules essentially are pulled through the cell membrane by PGP transport proteins," Murphy said. "It's an energetic process that happens like pulling a rope through something sticky." (Catherine Parrot, Pub. Date: May 2005)..................
