Figure 1.

Par1b promotes lateral lumen polarity in low Ca²⁺ (SMEM) monolayers. Cells were dislodged with Cellstripper (A–C) or trypsinized and cultured on collagen IV-coated (D) coverslips in SMEM for 18 h. (A) Confocal x-y and x-z sections showing gp135, phalloidin, and ZO-1 in Par1b cells; arrow, lateral lumina surrounded by ZO-1; arrowhead, gp135 in the intracellular apical compartment. (B) DPPIV-GFP (green) and DPPIV ectodomain antibody (red) in unpermeabilized (left) and Tx100-permeabilized (right) control (top) and Par1b (bottom) cells. ZO-1 labeling (blue) occurred after permeabilization. Note that the DPPIV antibody did not have access to intracellular VACs in control cells and intercellular lumina (arrows) in Par1b cells unless they were permeabilized. (C) Merged confocal x-y views of E-cadherin, Dlg, or Scribble and phalloidin- and Z-O1–labeled cells; arrows point to luminal surfaces in Par1b cells; note that the lateral markers are absent from this domain. (D) Confocal images of gp135, phalloidin, and ZO-1 in cells that where trypsinized and cultured on either uncoated or collagen IV (10 μg/cm²)-coated coverslips. Graph, effect of increasing concentration of collagen IV (0–20 μg/cm²) on lateral lumen formation in Par1b cells. Bars, 10 μm.