Introduction: In vivo, cancer cells can utilize tube-like microtracks formed within the extracellular matrix (ECM) of the stroma as 'highways' to escape the primary tumor, however very little is known about the molecular mechanisms that govern cell migration through these microtracks. Cell polarization and actin organization are both essential for efficient cell migration and cells are known to migrate very unidirectionally in confined spaces. In this study, we focused on understanding the role of Girdin during unidirectional migration. Girdin is a prometastatic protein known to be involved in cell polarity by directly interacting with the cell polarity protein Par-3 (Partitioning defective-3) and also known as an actin binding protein.
Methods: We utilized a microfabricated platform to recreate these microtracks in vitro using collagen and used siRNA to knockdown Girdin in MDA-MB-231 cells.
Results: Our data indicate that knockdown of Girdin results in decreased cell speed during 3D collagen microtrack migration. Loss of Girdin also results in altered cell morphology and cell orientation. Moreover, Girdin-depletion impairs actin organization and stress fiber formation, which can be restored by upregulating the GTPase RhoA. Activation of RhoA induces actin stress fiber formation, restores elongated migratory cell shape and partial cell migration in 3D collagen microtracks in the absence of Girdin.
Conclusions: Our data suggest that Girdin helps directional migration in collagen microtracks by promoting actin cytoskeletal organization and maintaining morphological cell polarity.
Keywords: Actin Cytoskeleton; Cell Morphology; Cell Orientation; Extracellular Matrix; Golgi Apparatus; RhoA.