Fig. 7. Orientation of the internal PtdIns(3,4,5)P₃ gradient in response to shear flow. CRAC-GFP-expressing cells were observed at high magnification under constant shear flow (=2 Pa). Cells were observed between 2 minutes and 10 minutes upon application of the flow. The figure shows a gallery of cells presenting a unique CRAC-GFP front aligned with the direction of the flow (arrow). Statistics of the CRAC-GFP orientation is provided in Table 4. Top: GFP fluorescence. Middle: fluorescence intensity profile along the line shown in the top panel. Bottom: phase contrast images of the same cells. These images were taken 5 seconds after the fluorescence ones. The triangles point to membrane extensions that had occurred between the two pictures. In the fluorescence image of the cell reported in (A), an endocytic structure can be seen (arrowhead).