Fig. 5: The formation of STIM1-Orai1 complex promotes the expansion of blebs.

a–f Membrane blebbing in DLD1 cells expressing Lifeact-RFP with either WT or dominant negative (E106Q) Orai1. a Representative still images from five independent experiments. b Tricolor maps showing angular coordinates along the horizontal axis and time on the vertical axis. Red zones represent expansion, blue zones represent retraction, and white zones represent no movement. Results shown are representative of three independent experiments. c Fluorescence intensities of GCaMP6s in “bleb” and “cell body” cytoplasm were quantified in DLD1 cells expressing either WT or E106Q Orai1. The ratio of “bleb” to “cell body” intensities are plotted over time. Data presented are means ± SD based on the values from five independent experiments. The number (d, N = 20 cells), area (e, N = 20 blebs), and retraction velocity (f, N = 10 blebs) of membrane blebs in WT or E106Q Orai1-expressing cells. g–l Membrane blebbing in DLD1 cells expressing Lifeact-RFP with either WT or dominant active (DA, D76A) STIM1. g Representative still images from three independent experiments. Arrowhead indicate persistent ER-PM contact site. h Tricolor maps showing angular coordinates along the horizontal axis and time on the vertical axis. Red zones represent expansion, blue zones represent retraction, and white zones represent no movement. Results shown are representative of three independent experiments. i Histograms of bleb expansion and retraction velocities in WT an DA STIM1-expressing cells. Three independent measurements are plotted for each condition. The number (j, N = 20 cells), area (k, N = 20 blebs), and retraction velocity (l, N = 10 blebs) of membrane blebs in WT or DA STIM1-expressing cells. Individual data points are plotted with the means ± SD. m Schematic of PM-ER contact site formation in the early stages of bleb formation. Details of the model are described in the text. a and g Scale bar, 10 μm. d–f, j–l ****P < 0.0001 (Two-sided, unpaired Student’s t test). Source data are provided as a Source Data file.