Fig 1: The membrane deformation disrupts cell interfaces.(a) Processed images of raw IF data (similar images are shown in Supplementary Fig. 7a,b) acquired from TIRFM imaging of HER2 (red, aH2Fab:QD), integrin beta 1 (ITGB1; blue, aCD29:alexa568) and paxillin (green, apaxillin:Alexa488) in MCF-7-HER2 cells showing the relative locations of these proteins. Less overlap between HER2 and ITGB1 is observed than between ITGB1 and paxillin. Scale bars, 5 µm. (b) IF images of paxillin distributions in basal cell membranes of various MCF-7 transfectants. The Paxillin distributions in all high HER2 expressers (3+; wtHER2 and the two signalling-incompetent HER2 mutants) are irregular compared to the more uniform distribution in the low HER2 expresser MCF-7-vctrl. Scale bars, 20 µm. (c) Average cell-surface coverage (mean±s.e.m.) of paxillin clusters (normalized (Nor.). Paxillin coverage) was calculated from the ratio of the area covered with paxillin (FLS greater than ~13% of the maximum intensity) to the total cell-surface area. ***P value<10-6 by two-sided, unpaired Welch's t-test. (d) Confocal IF images of E-cadherin (green, aE-cadherin:alexa488) in various MCF-7 transfectants. Scale bars, 30 µm. (e) Confocal IF images of HER2 (red, aH2Fab:QD) and E-cadherin in MCF-7-wtHER2 (left panels) and MCF-7-?icdHER2 (right panels) co-cultured with MCF-7-vctrl to contrast the delocalized patterns of E-cadherin in high HER2 expressers (red arrows) with the localized E-cadherin distributions in low expressers (green arrows). Scale bars, 20 µm. (f) A cartoon illustrating how the HER2-induced membrane deformation perturbs cell–substrate and cell–cell interfaces, and thus disrupts epithelial integrity. Shades of beige and red represent different cells.