Fig. 1. BRII is upregulated when A431 cells are serum-starving. Serum-starved or non-serum-starved A431 cells were fixed and fluorescently labeled to test for the expression of (B,C,G) BRII or (D,E,F) BRIa, using a polyclonal antiserum against BRII and a secondary donkey anti goat RRX antibody, respectively. Cells were fixed and high magnification images of flat membrane regions were collected with a confocal microscope. (F,G) Fluorescence-intensities for quantification, calculated from a large number (40) of images from different cells. Zoom-1 image of non-serum-starved A431 cells (A) labeled for BRIa, (B) stained for BRII. (C) Serum starvation of A431 cells leads to upregulation of BRII at the cell surface. (D) Non-serum-starved A431 cells that express BRIa. (E) Starved cells express comparable amounts of BRIa at the cell surface. (F) Expression levels of BRIa are the same for non-starved (N BRIa), starved (S BRIa) and stimulated (S BRIa + B) A431 cells. (G) Expression levels of BRII are very low for non-starved (N BRII) A431 cells, but is increased many-fold after starvation for 72 hours (S BRII) and remains constant upon stimulation with BMP-2 (S BRII + B). (H) A typical autocorrelation function for BRIa.