Figure 1.

HPIV3 IBs Change the Distribution of ER Proteins

(A–D) HeLa cells grown in 24-well plates were transfected with plasmids encoding N-Myc (0.1 μg) and HA-P (0.4 μg) for 24 h to form IBs and analyzed for colocalization of the Golgi protein TGN46 (A), the mitochondrial protein Tom20 (B), the ER protein Calnexin (C), the ER protein PDI (D), and IBs. The fluorescence intensity profile of IBs (green) and organelle proteins (red) was measured along the line drawn on a 2× zoom panel by Leica Application Suite Advanced Fluorescence Lite.

(E and F) HeLa cells stably expressing GFP-tagged P were infected with HPIV3 (MOI = 0.1) for consecutive times (0 h, 12 h, 24 h, 30 h, and 36 h) and analyzed for distribution of the ER proteins Calnexin (E) and PDI (F). Yellow arrows indicate representative colocalization of ER proteins and IBs.

(G) Kinetic process of the ER protein Calnexin fusing into IBs. HeLa cells expressing GFP-tagged P were seeded into 20-mm dishes for 24 h, infected with HPIV3 (MOI = 0.1), transfected with mCherry-Calnexin (0.5 μg), and visualized by live-cell imaging. The fusion event is marked with white arrows and numbers. In (a) and (b), white arrows indicate Calnexin protein (red) attached to small IBs (green) fused into small IBs to form a homogeneous structure. In (b) and (c), 1 and 2 fused into 3. In (d) and (e), arrow 4 indicates that Calnexin was absorbed into small IBs. In (f)–(h), 3 and 4 fused into 7 and 5 and 6 fused into 8. In (i) and (j), 7 and 8 fused into 9.

Scale bars, 10 μm. See also Figure S1.