Sugars Influence Cell-to-Surface Adhesion
How can cells adhere to surfaces and move on them? This is a question which was investigated by an international team of researchers headed by Prof. Michael Hippler from the University of Münster and Prof. Kaiyao Huang from the Institute of Hydrobiology (Chinese Academy of Sciences, Wuhan, China). The researchers used the green alga Chlamydomonas reinhardtii as their model organism. They manipulated the alga by altering the sugar modifications in proteins on the cell surface. As a result, they were able to alter the cellular surface adhesion, also known as adhesion force. The results have now been published in the open access scientific journal “eLife”.
Background and methodology
Flagella-mediated adhesion and gliding by Chlamydomonas reinhardtii (green alga) on a solid surface (top). Using TIRF microscopy, these dynamics can be visualized and analysed (bottom).
In order to study these processes, the researchers first used so-called insertional mutagenesis and the CRISPR/Cas9 method to deactivate genes which encode enzymes relevant to the N-glycosylation process. “The next step was to analyse the sugar modifications of these genetically altered algae strains using mass spectrometry methods,” says Michael Hippler, explaining the team’s approach. In order to visualise the cell-gliding, the researchers used a special method of optical microscopy – total internal reflection fluorescence microscopy (TIRF). This method is frequently used to carry out examinations of structures which are located very close to a surface. For this purpose, a fluorescent protein was expressed in the flagella of the algae in order to make the flagella and the cell-gliding visible.
In order to measure how much force was used in adhering the individual cells to the surface, atomic force microscopy was used and micropipette adhesion measurements were undertaken in collaboration with groups at the University of Liverpool (UK) and the Max Planck Institute of Dynamics and Self-Organization in GÖttingen. “This enabled us to verify that adhesion forces in the nanometre range are reduced by altering the protein sugar modifications,” adds Kaiyao Huang.
The two flagella on the green alga resemble for example not only the flagella of sperm but also other movable flagella. These are usually called ‘cilia’ and are also found in the human body – for example in the respiratory tracts. “If we transfer our findings to human cells, sugar-modified proteins could be used to change the interaction of sperm or cilia with all sorts of surfaces,” say Kaiyao Huang and Michael Hippler.
Besides researchers from the University of Münster, scientists from Berlin’s Humboldt University, the Universities of Wuhan (China) and Liverpool (England) and the Max Planck Institute of Dynamics and Self-Organization in GÖttingen contributed to the study.
The study received financial support from the German Research Foundation (DFG) and the National Nature Science Foundation of China, as well as from the Royal Society and the Biotechnology and Biological Sciences Research Council in the UK.
Nannan Xu, Anne Oltmanns, Longsheng Zhao, Antoine Girot, Marzieh Karimi, Lara Hoepfner, Simon Kelterborn, Martin Scholz, Julia Beißel, Peter Hegemann, Oliver Bäumchen, Lu-Ning Liu, Kaiyao Huang, Michael Hippler (2020). Altered N-glycan composition impacts flagella mediated adhesion in Chlamydomonas reinhardtii. eLife. DOI: 10.1101/2020.05.18.102624