tment. Furthermore, 139504-50-0 site O-glycosylation inhibition in response to a 1-d treatment with 10 mM GalNAc-bn was also observed in human 11095475 colon adenocarcinoma Colo 205 cells, one of the most heavily O -glycosylated cell lines . These findings indicate that 10 mM GalNAc-bn treatment resulted in stable and maximum inhibition of O-glycosylation 1 d after treatment, whereas the effects of 2 mM GalNAc-bn appeared gradually after 3 d of treatment. Although it was thought that various optimum concentrations were required for different cell lines and conditions, to obtain comprehensible results in the present study using NIH3T3 cells, we chose a 1-d treatment of NIH3T3 cells with 10 mM GalNAc-bn to inhibit Oglycosylation in subsequent experiments. Western blot analysis Western blot analysis was performed as previously described. Immunodetection was performed using the ECL Western Blotting Detection System 
with peroxidase-coupled secondary antibodies according to the manufacturer’s instructions. Immunocytochemistry NIH3T3 and Colo 205 cells were cultured in 4-well Lab-Tek Chamber Slides and treated with 2 mM GalNAc-bn or the same volume of DMSO for 10 d or with 10 mM GalNAc-bn for 1 d. These cells were fixed with 4% paraformaldehyde for 1 h at room temperature, then blocked for 1 h in 5% goat serum, 0.1% bovine serum albumin, and 0.1% Triton-X in PBS at room temperature, incubated with primary antibodies for over 12 h at 4C, washed with PBS-T for 30 min, and treated with secondary antibodies. Fluorescence was analyzed on a Zeiss Axiovert 100 microscope. TUNEL assay Cell death was assessed with the TMR Red In Situ Cell Death Detection Kit, and cells were observed under a fluorescence microscope. Phenylindole dihydrochloride images were overlaid with TUNEL-stained images to enumerate the different cell populations. TUNEL-positive cells are expressed as a percentage of total DAPI-positive cells. For each experiment, at least 5 fields were Identification of the site of GalNAc-bn-induced inhibition of O-glycosylation If the inhibition of O-glycosylation by GalNAc-bn occurred in the Golgi apparatus, the binding complex comprising PNA and O-glycosylation-inhibited sites 15325591 would be detected in the Golgi apparatus. We sought to clarify this issue using NIH3T3 cells and Colo 205 cells. To investigate whether PNA binding complexes were localized in the Golgi apparatus, we performed double 3 HSP47 Prevents Golgi Stress-Induced Cell Death doi: 10.1371/journal.pone.0069732.g001 immunostaining with antibodies against PNA and GM130 in NIH3T3 cells after O-glycosylation inhibition. Under normal conditions, PNA was hardly detectable in the cells, whereas strong PNA immunoreactivity was detected in the cytoplasm near the nucleus 1 d after GalNAc-bn treatment. The PNA staining pattern was very similar to that obtained with the anti-GM130 antibody, which recognizes the Golgi apparatus. As shown in Expression of the ER resident chaperone HSP47 was elevated during O-glycosylation inhibition Protein expression is generally reduced when glycosylation is inhibited. Therefore, proteins whose synthesis is increased in response to O-glycosylation inhibition are likely involved in Golgi protection. Therefore, we next sought to identify molecules whose expression was increased 1 d after GalNAc-bn treatment using two-dimensional polyacrylamide gel electrophoresis. We used Colo 205 cells because Oglycosylation is very active in these cells; therefore, Oglycosylation inhibition is expected to
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