Protein phosphatases and signalling

PP2A and PP4 (Protein Phosphatase 2A and Protein Phosphatase 4) are conserved enzymes found in all eukaryotes and are in fact crucial for biological functions in all kinds of eukaryotic cells.

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Cathrine Lillo
Professor Cathrine Lillo

The importance of protein phosphatases for upholding healthy life and the cellular collapse that occurs when these enzymes are inhibited is strikingly illustrated by the problem with drinking water and algae blooms.

Some algae produce a toxin (microcystin) that bind to PP2A and PP4 and prevents the enzymes from doing their job in humans, animals and plants. For example in 2014, half a million people in Ohio were without drinking water because of such toxins in Lake Erie. These toxins are a worldwide problem, - also in our local Hålandsvannet close to Stavanger.

Protein phosphatases remove phosphate from proteins, and this dephosphorylation will change the properties of proteins regarding their stability, activity and subcellular localization. However, the target proteins being dephosphorylated by PP2A and PP4 are generally not known, and identifying these proteins is an important aim of our research.

PP2A and PP4 are part of signalling cascades that regulate plant growth, defence and development. The acquisition of nutrients, response to pathogens, flowering time and fruit development are processes involving PP2A and PP4, but we still do not know many details concerning exactly where in the processes PP2A and PP4 are involved.

Our research show that PP2A and PP4 are important in the perception and/or transmission of signals from the environment, for example stress responses to pathogens and quick responses to light changes. Our experiments also indicate a role for PP2A in responses to changes in oxygen conditions.

Canonical PP2A and PP4 are trimeric proteins consisting of a catalytic, a regulatory, and a scaffolding subunit. In the model plant Arabidopsis thaliana there are at least 20 scaffolding/regulatory subunits, and their specific function in metabolism and physiology is hardly known. In addition to Arabidopsis, we will also use tomato plants in our future research.

Tomato is the most important greenhouse crop in the Stavanger region (Rogaland). We intend to identify which subunits are taking part in which processes in the plant, and finely identify substrates of the different PP2A and PP4 complexes.

Nitrate reductase, a key enzyme in nitrate assimilation, is activated by PP2A during dark to light transitions of plants, and nitrogen assimilation continues to be a topic of interest for the group.

Furthermore PP2A regulates processes related to b-oxydation of fatty acids and hormone precursors, which will be further studied.

Protein Phosphatase and Signalling group

  • Lillo, Cathrine
  • Kataya, Amr
  • Heidari, Behzad
  • Nemie-Feyissa, Dugassa
  • Creighton, Maria

Norwegian cooperation

  • Dr. Michel Verheul, NIBIO and Dr. Ivan Paponov , NIBIO, S√¶rheim Research Station

International cooperation

  • Prof Jose Sanchez-Serano and Dr Maite Sanmartin, National Centre of Biotechnology (CNB-CSIC) in Madrid/Spain
  • Dr. Anna Kolton, Faculty of Biotechnology and Horticulture, University of Agriculture in Krakow/Poland

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