Deubiquitinating enzymes vital for endosomal transport identified

The University of Konstanz’s Plant Physiology and Biochemistry research group has discovered previously unrecognized molecular mechanisms by which plants acclimatize to their environment—vital basic knowledge in times of climate change.

Plants are constantly subjected to environmental changes, and their existence is dependent on their capability to detect and adapt to these changes. Protein molecules in the cell membrane are important for coordinating extracellular signals and intracellular reactions.

The Plant Physiology and Biochemistry research group at the University of Konstanz has now identified two deubiquitinating enzymes that are involved in the molecular mechanism of this adaptation process. The research was published in the journal Nature Communications.

The amount of protein molecules is crucial

The cell must detect nutrients or pathogens in its environment as part of the adaptation process. This is the function of unique protein molecules known as transporters and receptors, which are found on the cell membrane, which separates the inside of the cell from the outside world. They are both created and destroyed in the cell. The quantity of these molecules is critical for the plant's signal perception.

Ubiquitin, a tiny signal protein, binds to other proteins and assures their degradation. Simultaneously, deubiquitylating enzymes can reverse this impact by eliminating ubiquitins.

The research team led by Erika Isono, a biology professor, examined 18 of these deubiquitylating enzymes in the model plant Arabidopsis thaliana. The researchers discovered two of these enzymes, called OTU11 and OTU12, which are situated at the cell membrane and are involved in controlling the amount of cell membrane proteins, in collaboration with Karin Hauser, Michael Kovermann, and Christine Peter from the Department of Chemistry.

OTU11 and OTU12 can shorten certain ubiquitin chains. This influences the degradation of the modified proteins.”

Karin Vogel, Study Lead Author, University of Konstanz

The biologist also identified how they are activated: by adhering to negatively charged lipids on the cell membrane.

Previously unknown form of activity adjustment

This suggests that the enzymes’ activity is closely regulated. There are currently several activation methods for deubiquitylating enzymes. The mechanism described in this research is a previously undiscovered type of activity adaptation. This control is critical because the impact of deubiquitylating enzymes can have serious ramifications for cell function.

Our discovery shows that the deubiquitylating enzymes do not become active until they arrive at the membrane, where the lipids are located. This fits perfectly with the intracellular localization and function of the two enzymes.”

Erika Isono, Biology Professor, University of Konstanz

The basic biological study employs model plants to examine fundamental biochemical and molecular biological mechanisms. Long-term goals include optimizing agricultural production, which is especially crucial in times of climate change because plant growing conditions can alter as a result.

It's important that we understand at the molecular level how plants respond to the environment. The ubiquitin-dependent signaling pathway probably plays an important role in this process.”

Erika Isono, Biology Professor, University of Konstanz