Fig. 5

NGF and TrkA activation are dispensable in nanostructure-induced neuritogenesis whereas β1 integrin activation/signaling are essential. a The scheme illustrates the interference points of the various inhibitors of proteins involved in the integrin and RTK signaling cascade which were used in the experiments. b–d The PC12 cells were plated on PLL (+NGF) or surfaces with a roughness R_q of 15 nm rms. In case of inhibitor treatment, the inhibitors were preincubated for 15 min prior to cell plating and then present for the whole ongoing experimental period. The cell morphology was recorded by phase contrast microscopy 24 h after plating the cells. As biological read-out for the differentiation the quantification of the neurite outgrowth is shown (obtained with the help of ImageJ); representative images can be found in Additional file 1: Figure S1. The bars display the change of neurite outgrowth compared to the situation without treatment on the corresponding substrate. The bars are flanked by SD. The graph displays the results of an inhibitor treatment against b TrkA (GW441756 1 µM, from two independent experiments), c the incubation with the 4B4 inhibitory antibody (2.5 µg/ml) (or activity-neutral antibody K20 (2.5 µg/ml) as control) against β1 integrin (from three independent experiments) or d the inhibition of MEK 1/2 (U1026 10 µM, from two independent experiments), always both in the canonical (NGF-induced) and the nanostructure-induced condition (n: >500 cells, >150 neurites). Further inhibitions of major mediators and processes involved in integrin signaling and cytoskeletal organization are displayed in Additional file 3: Figure S3