FIGURE 1:

GPP130 lumenal sequence element confers Mn sensitivity. (A) Localization is shown for GFP-tagged GP73 constructs containing the indicated GPP130 residues in the absence or presence of 0.5 mM MnCl₂ for 2 h. The images are cropped and identically thresholded to accentuate presence in peripheral punctae. Arrowheads indicate the position of example punctae. The localization of endogenous GPP130 in the same Mn-treated cells serves as an internal control for the Mn response. The chimeric constructs contain the cytoplasmic, transmembrane, and stem domain of GP73, followed by a GPP130 segment, followed by GFP. Before analysis the cells were treated with 0.1 mg/ml cycloheximide for 2 h to prevent new synthesis. Scale bar, 5 μm. (B) Schematic diagram of the GPP130 segments present in the GFP-tagged GP73 chimeric constructs and the quantified determination of their presence in peripheral endosomal structures in the absence or presence of Mn. Object analysis is described in Materials and Methods. Values are averages (n > 25 cells, ±SEM). *p < 0.05 for comparison to untreated.