Cell Stress and Chaperones

, Volume 13, Issue 4, pp 497–507

Endoplasmic reticulum stress in the absence of calnexin

  • Helen Coe
  • Karen Bedard
  • Jody Groenendyk
  • Joanna Jung
  • Marek Michalak
Original Paper

DOI: 10.1007/s12192-008-0049-x

Cite this article as:
Coe, H., Bedard, K., Groenendyk, J. et al. Cell Stress and Chaperones (2008) 13: 497. doi:10.1007/s12192-008-0049-x
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Abstract

Calnexin is a type I integral endoplasmic reticulum (ER) membrane chaperone involved in folding of newly synthesized (glycol)proteins. In this study, we used β-galactosidase reporter gene knock-in and reverse transcriptase polymerase chain reaction (RT-PCR) to investigate activation of the calnexin gene during embryonic development. We showed that the calnexin gene was activated in neuronal tissue at the early stages of embryonic development but remained low in the heart, intestine, and smooth muscle. At early stages of embryonic development, large quantities of calnexin messenger RNA (mRNA) were also found in neuronal tissue and liver. There was no detectable calnexin mRNA in the heart, lung, and intestine. The absence of calnexin had no significant effect on ER stress response (unfolded protein response, UPR) at the tissue level as tested by IRE1-dependent splicing of Xbp1 mRNA. In contrast, non-stimulated calnexin-deficient cells showed increased activation of IRE1, as measured by RT-PCR and luciferase reporter gene analysis of splicing of Xbp1 mRNA and activation of the BiP promoter. This indicates that cnx−/− cells have increased constitutively active UPR. Importantly, cnx−/− cells have significantly increased proteasomal activity, which may play a role in the adaptive mechanisms addressing the acute ER stress observed in the absence of calnexin.

Keywords

Calnexin Embryonic development Endoplasmic reticulum IRE Unfolded protein responses ERAD 

Abbreviations

ER

endoplasmic reticulum

UPR

unfolded protein response

IRE1

inositol-requiring enzyme 1

Xbp1

X-box binding protein 1

ERAD

ER-associated degradation

PDI

protein disulfide isomerase

PBS

phosphate buffered saline

OCT

optimal cutting temperature compound

Copyright information

© Cell Stress Society International 2008

Authors and Affiliations

  • Helen Coe
    • 1
  • Karen Bedard
    • 1
  • Jody Groenendyk
    • 1
  • Joanna Jung
    • 1
  • Marek Michalak
    • 1
  1. 1.Departments of Biochemistry and PediatricsUniversity of AlbertaEdmontonCanada

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