Cells contain many different organelles that fulfill various essential and specific functions. Specific reactions that are carried out in the various organelles are, for example, the generation of energy or the synthesis of dedicated molecules such as certain lipids and proteins. Because these reactions are usually compartmentalized within the organelles, required proteins are specifically targeted to a certain organelle. In our study, we investigated the specific targeting of proteins to the peroxisome organelles. Peroxisomes are important for lipid metabolism and the detoxification of reactive oxygen species, which can cause damage to any component of living cells, like DNA or proteins.
We specifically studied the diffusion and interaction characteristics of the peroxisomal import receptor and its cargo proteins in the cellular cytosol by using fluorescence microscopy, as indicated in the cover image of the June 8 issue of Biophysical Reports. The receptor and the cargo were each labeled with differently colored fluorescent dyes, and their diffusion and interaction characteristics were extracted as their fluorescence shined on and off when they moved inside and out of a laser beam focused inside the cytoplasm. Our main observation was that the import receptor diffused much slower than expected, pointing to an additional cytosolic binding partner other than the cargo proteins. We could rule out many potential causes of a slow-down such as multimerization of the receptor, and we could pinpoint to specific parts of the import receptor, where the additional binding takes place. However, the exact identity of these additional binding partners thus far remains unknown.
With our study, we highlight important new insights into the mechanism of organelle protein and demonstrate that advanced microscopy methods combined with biochemical knowledge of protein trafficking mechanisms in the cell can support and enrich each other.
If you are interested in finding out more about how we use advanced microscopy methods to study intracellular dynamics, please visit https://www.biophysical-imaging.com/.
- S. Galiani, K. Reglinski, P. Carravilla, A. Barbotin, I. Urbančič, J. Ott, J. Sehr, E. Sezgin, F. Schneider, D. Waithe, P. Hublitz, W. Schliebs, R. Erdmann, and C. Eggeling