Roles of Endocytic Processes and Early Endosomes on Focal Adhesion Dynamics in MDA-MB-231 Cells

Focal adhesion (FA) play a critical role in many biological processes which include cell survival and cell migration. They serve as a cellular anchor, allowing cells to stay attached to the extracellular matrix (ECM), and can also regulate cellular transduction. Previously, it has been suggested that vesicles such as endosomes could interact directly with FA or be implicated in their turnover. In this study, we investigated whether there is a relationship between FA and the early endocytic machinery in MDA-MB-231 cells.

In this study, cell culture, transfection, time lapse confocal microscopies, immunocytochemistry, western blotting, cell fractionation, and immunoprecipitation techniques were performed.

Cells acutely treated with Dynasore, an inhibitor of dynamin, or with Pitstop 2, an inhibitor of clathryn-dependent endocytosis showed a reduction in the expression of early endosome biomarkers such as Rab5 and EEA1. Additionally, cells treated with these endocytic inhibitors exhibited an increased number and size of FA, as well as an increased FA turnover duration. This data was consistent with the reduction of the speed of cell migration. We demonstrated that Rab5- and EEA1-positive early endosomes were found to be colocalized with internalized FA.

The present study suggests that there is a link between FA and early endosome markers, which indicates that the early endosomes may be involved in FA dynamics.