The discovery is good news for cancer sufferers, who for too long have had to endure a 'hit and miss' approach to treatment. The sheer variability and severity of different cancer types means that chemotherapy has to be tailored to the individual.
"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," said Purdue plant cell biologist Angus Murphy.
Scientists at the University of Zurich showed for first time that PGP1, a P-glycoprotein from the plant Arabidopsis, transports auxin out of plant cells and also out of yeast and mammalian cells. They also found that other PGP proteins move auxin into cells.
The scientists theorise that discovery of methods to control the plant protein's activity may aid in development of therapies to reduce drug dosages administered to cancer patients.
Both the multi-drug resistant PGPs in people and plants are part of a large family of proteins, called ATP-binding cassette (ABC) proteins that detoxify cells, send messages from cell to cell to influence biochemical reactions, and to regulate those reactions.
"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.
In 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 best known member of another class of transport proteins, PIN1, also may be a transporter, but appears to function primarily as an aide for auxin transport.
This finding revealed that PINs and PGPs might function together in long-distance auxin transport, according to the research..
Named for the pin-shaped appearance of the mutant originally used to identify the gene that directs the activities of PIN1, these proteins are members of the major protein family, called facilators, that aid processes such as hormone transport.
"Recent evidence suggests that teamwork between PGP and PIN proteins determines the direction auxin moves and, therefore, how the plant develops," Murphy said.
Murphy is corresponding author of the study published in the November issue of Plant Cell.