Figure 6.

Grp78 (glucose-regulated protein 78) knockout (KO) decreases alveolar epithelial type II (AT2) cell proliferation and colony-forming efficiency. (A and B) Tm⁺ AT2 cells decrease (A) and Tm⁺ Edu⁺ cells increase (B) at 1 week, peak at 2 weeks, and decrease over time after tamoxifen (Tmx) (100–140 mg/kg on three consecutive days) injection into Grp78^SCE;ROSA^Tm/Tm (Tm reporter gene knocked into the ubiquitously expressed ROSA [reverse orientation with splice acceptor] 26 locus, originally identified by gene trapping using the ROSA vector) mice (2–4 mo old) compared with SCE;ROSA^Tm/Tm mice after Tmx. n = 3 for each group. Two-way ANOVA: *P < 0.05. (C) Tm⁺ AT1 cells (arrows) appear in Grp78 KO lungs at 14 days, and a cluster of Tm⁺ AT1 cells is enlarged at 90 days after Tmx. n = 3. Scale bars, 50 μm. Inset shows higher-magnification views of rectangular area. (D and E) Representative image (D) and quantitative analysis (E) show a trend toward decreased number of colonies of AT2 cells isolated 1 week after Tmx injection (100–140 mg/kg) into Grp78^SCE mice compared with AT2 cells from mice without Tmx injection. n = 3. Scale bars: upper panels, 1 mm; lower panels, 100 μm. (F and G) Representative image (F) and quantitative analysis (G) show that Tm⁺ Grp78 KO AT2 cells sorted 5 days after Tmx injection into Grp78^SCE;ROSA^Tm/Tm mice form very few colonies compared with cells from SCE;ROSA^Tm/Tm mice. n = 3. Scale bars: upper panels, 1 mm; lower panels, 100 μm. EdU = 5-ehtynyl-2′-deoxyuridine; Tm = Tomato.