The endoplasmic reticulum-resident chaperone heat shock protein 47 protects the Golgi apparatus from the effects of O-glycosylation inhibition

PLoS One. 2013 Jul 29;8(7):e69732. doi: 10.1371/journal.pone.0069732. Print 2013.

Abstract

The Golgi apparatus is important for the transport of secretory cargo. Glycosylation is a major post-translational event. Recognition of O-glycans on proteins is necessary for glycoprotein trafficking. In this study, specific inhibition of O-glycosylation (Golgi stress) induced the expression of endoplasmic reticulum (ER)-resident heat shock protein (HSP) 47 in NIH3T3 cells, although cell death was not induced by Golgi stress alone. When HSP47 expression was downregulated by siRNA, inhibition of O-glycosylation caused cell death. Three days after the induction of Golgi stress, the Golgi apparatus was disassembled, many vacuoles appeared near the Golgi apparatus and extended into the cytoplasm, the nuclei had split, and cell death assay-positive cells appeared. Six hours after the induction of Golgi stress, HSP47-knockdown cells exhibited increased cleavage of Golgi-resident caspase-2. Furthermore, activation of mitochondrial caspase-9 and ER-resident unfolded protein response (UPR)-related molecules and efflux of cytochrome c from the mitochondria to the cytoplasm was observed in HSP47-knockdown cells 24 h after the induction of Golgi stress. These findings indicate that (i) the ER-resident chaperon HSP47 protected cells from Golgi stress, and (ii) Golgi stress-induced cell death caused by the inhibition of HSP47 expression resulted from caspase-2 activation in the Golgi apparatus, extending to the ER and mitochondria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Endoplasmic Reticulum / metabolism*
  • Glycosylation
  • Golgi Apparatus / metabolism*
  • HSP47 Heat-Shock Proteins / metabolism*
  • Mice
  • Mitochondria / metabolism
  • NIH 3T3 Cells

Substances

  • HSP47 Heat-Shock Proteins

Grant support

This work was supported in part by Grant-in-Aid for Scientific Research (C) (KAKENHI; grant 25430079), the Sakamoto Research Institute of Psychopathology, and the Global Center of Excellence Program from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding was received for this study.