Figure 4.

TPC1 Localizes to ER-Endosome Contact Sites and Regulates Their Formation

(A and B) Electron micrographs showing distribution of TPC1 and TPC2 in fibroblasts (A) and localization of TPC1 at contact sites (B). Summary data quantifying the presence of TPC1 at contact versus non-contact sites are shown to the right. Cells were transfected with GFP-tagged TPC constructs and stained for GFP (white arrows) using pre-embedding labeling. Scale bar, 200 nm. Black arrows, ER contact sites.

(C–E) Electron micrographs showing ER membrane contact sites between late endosomes and lysosomes in fibroblasts treated with a scrambled siRNA, 100 μM Ned-19, or with siRNA targeting TPC1 or TPC2 (C). The percentage of endosomes (D) or lysosomes (E) with an ER contact site were quantified. Data are from three independent treatments (± SEM). Scale bar, 200 nm. Black arrows, ER contact sites.

See also Figure S3.