Integrin-mediated adhesion in the unicellular holozoan Capsaspora owczarzaki
In animals, cell-matrix adhesion is mainly mediated by integrins and their associated proteins. Comparative genomic analyses have shown that core components of the integrin adhesome pre-date the emergence of animals, however, whether it mediates cell adhesion in non-metazoan taxa remains unknown. Here, we investigate cell-substrate adhesion in Capsaspora owczarzaki, the closest unicellular relative of animals with the most complete integrin adhesome. Using an adhesion assay, we show that C. owczarzaki adheres to surfaces using actin-dependent filopodia. We show that integrin {beta}2 and its associated protein vinculin localise as distinct patches in the filopodia. We also demonstrate that substrate adhesion and integrin localisation are enhanced by the ligand fibronectin. Finally, using a specific antibody for Integrin {beta}2, we inhibited cell adhesion to a fibronectin-coated surface. Our results show that adhesion to the substrate in C. owczarzaki is mediated by integrins. This suggests that integrin-mediated adhesion pre-dates the emergence of animals.