A molecular switch helps cell recognise sex partner

“This mating decision is controlled by a simple chemical switch that converts an incoming pheromone signal into a cellular response,” says study author Stephen Michnick, University of Montreal biochemistry professor.

Enzyme activity begins
“As pheromone signal increases, two enzymes in the cell begin to compete with each other, one adding, the other removing a chemical modification on a protein called Ste5,” the author said. He noted that at a critical threshold of pheromone signal, one of the enzymes overwhelms the others’ capacity to modify Ste5, triggering a sudden, switch-like cascade of chemical messages to be delivered to the cell to say it’s time to mate.

The findings were made in collaboration with physicist Peter Swain, McGill University and the University of Edinburgh, and his postdoctoral fellow Vahid Shahrezaei, now a lecturer at Imperial College London, Britain.  They were able to describe with mathematical precision how this switch works to drive the mating decision.

Yeast used for research
The research team used the single cell yeast, which is used to leaven bread, for their study. “Although yeast is dramatically different from people, at a molecular and cellular level we have a lot in common,” says Michnick.

“The same molecules that create the switching decision in yeast are found in very similar forms in human cells,” he adds.

“Similar switching decisions to those made by yeast are made by stem cells during embryonic development and become dysfunctional in cancers.”
Using yeast enabled the research to show how a cell might make important decisions. When yeast cells decide to mate, they must know that there is a mating partner close enough, and then make a snap decision to get ready to mate, says study author and graduate student Mohan Malleshaiah.

Their decision to mate is not just fast, but precise, resulting in their selection of the best available partner, even though there may be many competing potential mates nearby, Malleshaiah says, according to a Montreal release.

“It is fascinating to see that the same principles that Darwin described to explain why a lioness chooses the strongest lion or a peahen chooses a peacock that has the most beautiful plumage can be so clearly observed at a molecular level in yeast,” Malleshaiah adds.

“Perhaps... we may look forward to more discoveries of such switching mechanisms, with the potential of understanding and predicting how humans emerge from the complex process of cells deciding to become different tissues during development and how these decision-making switches break down in diseases,” says Michnick.