The PI3K pathway controls ErbB2- dependent microtubule stability and chemotaxis.

<p>(<b>A</b>) Upper panels: SKBr3 cells expressing EGFP-tubulin were pre-treated with DMSO or the PI3K inhibitor LY294002, before addition of HRG and analysis by time-lapse fluorescence microcopy. Still images, from Video 1, corresponding to early (0.5 to 1.5 h) and late (>1.5 h) time points are shown. Lower panels: Cells loaded on a Dunn chamber were treated as in A, for analysis of the chemotactic response at early time points (0.5 to 1.5 h) or late time points (1.5 to 4 h). Rose diagrams and Rayleigh tests are shown. p>0.05 is considered random migration. (<b>B</b>) The percentage of cells with disassembled microtubules was evaluated. 90–150 cells were counted per condition in three independent experiments; mean+/−s.e.m. is shown; * p<0.01. (<b>C</b>) Cells were pretreated with the indicated drugs, before addition of HRG for 30 or 90 min. Cells were fractionated into microtubule-enriched and soluble tubulin-enriched fractions and tubulin content was analyzed by Western blotting. An anti-RhoGDI antibody was used to assess protein loading. Nocodazole (Noco) and Taxol were used as reference microtubule-destabilizing and -stabilizing drugs, respectively.