Every living thing is composed of cells and, via receptor proteins on their outer surface, cells communicate with each other and with the outside world. Receptors are found on skin cells (pain and pressure receptors, for example) as well as on the cells of other tissues and organs.

By binding with certain substances, such as hormones, the receptors pick up signals from outside the cell, then they transmit the signal to the interior of the cell where it can induce all kinds of reactions. Receptors can be stimulated or blocked to evoke or prevent a certain effect. Foreign substances, such as medicines, can also bind to a receptor and cause a particular effect. For some time, scientists have suspected that cells can also detect the presence of food via one or another receptor - but no one has known how that might happen.

Researchers for VIB (the Flanders Institute for Biotechnology) connected to the Katholieke Universiteit Leuven say they have discovered an important new mechanism with which cells can detect nutrients. This happens in the same way - and with the same effects – as when cells receive a message from a hormone. This finding can teach us more about how food affects our body and it can form the basis for new candidate targets for medicines. 

In addition to receptors, cells also have transport proteins that can carry nutrients through the cell membrane to the inside of the cell, where they can be put to use. Furthermore so-called ‘transceptors’ have been discovered that sense and transport food simultaneously.

Now, VIB researcher Griet Van Zeebroeck and her colleagues in Johan Thevelein’s group have shown for the first time how one of these transceptors (called Gap1) works. Gap1 transports amino acids (a protein’s building blocks) to the inside of a cell. At the same time, via the same mechanisms that cells use to transmit signals from hormones, Gap1 sends the cell a signal that food is present. The transceptor apparently uses the same binding site to recognize the food as it uses to grasp the food for transport. 

Yeast vs. humans
This research has been conducted on yeast cells, as yeast (Saccharomyces cerevisiae) is a micro-organism that is used as a model organism. Yeast cells are surprisingly similar to human cells, but they are easier to cultivate and manipulate. Very often, proteins that are found in yeast - transport proteins and receptors, for example - have similar variants in human cells. 

This research can have important implications for the development of medicines because about half of all medicines are transmitted to cells via receptors.  Receptors are located on the cells’ exterior surface and are therefore the best targets for medicines. If these newly discovered transceptors are also found in humans, then an unexpected new group of candidate targets for medicines becomes available - offering promising possibilities for the treatment of metabolic diseases.

This research has been conducted by Griet Van Zeebroeck and colleagues in Johan Thevelein’s ‘Nutrient Sensing and Signaling in Yeast’ research group in VIB’s Department of Molecular Microbiology, under the direction of Johan Thevelein.

Article: Van Zeebroeck et al., 'Transport and signaling via the amino acid binding site of the yeast Gap1 amino acid transceptor', Nature chemical biology