Dictyostelium discoideum is a social amoeba commonly used as a model organism for the study of various cellular processes, including directed cell migration. Mechanical cues, such as shear flow, have the ability to induce directed migration. However, little is known about the role of cell-substrate adhesion in mechanotransduction of D. discoideum. We hypothesized that adhesion is essential for the ability of cells to sense and respond to mechanical cues. To test this hypothesis, we examined whether mechanotransduction depends on SibA, a transmembrane protein involved in the adhesion of D. discoideum. Before testing cell response to shear flow, we studied the adhesion of SibA-null cells grown under our experimental conditions. Adhesion of SibA-null cells in growth media was significantly reduced compared to wild-type cells, consistent with previously published findings. Notably, adhesion was significantly decreased by 25% in SibA-null compared to wild-type cells grown on a bacterial lawn, which is the growth method used prior to the assessment of response to shear flow. To test how SibA-null cells respond to acute mechanical stimulation, we examined the localization of active Ras as a read-out of the activation of the signal transduction network involved in directed migration. Both wild-type and SibA-null cells had a comparable response to 2-second stimulation with shear flow at two different pressures. These findings suggest that the modest reduction in adhesion observed in SibA-null cells did not affect the ability of cells to respond to shear flow stimulation. Whether more substantial changes in adhesion would perturb mechanotransduction in this system remains to be examined.
