Activation of the unfolded protein response in infarcted mouse heart and hypoxic cultured cardiac myocytes

Donna J. Thuerauf, Marie Marcinko, Natalie Gude, Marta Rubio, Mark A. Sussman, Christopher C. Glembotski

Research output: Contribution to journalArticlepeer-review

248 Scopus citations

Abstract

Endoplasmic reticulum (ER) stresses that reduce ER protein folding activate the unfolded protein response (UPR). One effector of the UPR is the transcription factor X-box binding protein-1 (XBP1), which is expressed on ER stress-mediated splicing of the XBP1 mRNA. XBP1 induces certain ER-targeted proteins, eg, glucose-regulated protein 78 (GRP78), that help resolve the ER stress and foster cell survival. In this study, we determined whether hypoxia can activate the UPR in the cardiac context. Neonatal rat ventricular myocyte cultures subjected to hypoxia (16 hours) exhibited increased XBP1 mRNA splicing, XBP1 protein expression, GRP78 promoter activation, and GRP78 protein levels; however, the levels of these UPR markers declined during reoxygenation, suggesting that the UPR is activated during hypoxia but not during reoxygenation. When cells were infected with a recombinant adenovirus (AdV) encoding dominant-negative XBP1 (AdV-XBP1dn), UPR markers were reduced; however, hypoxia/reoxygenation-induced apoptosis increased. Confocal immunocytofluorescence demonstrated that hypoxia induced GRP78 in neonatal rat and isolated adult mouse ventricular myocytes. Moreover, mouse hearts subjected to in vivo myocardial infarction exhibited increased GRP78 expression in cardiac myocytes near the infarct, but not in healthy cells distal to the infarct. These results indicate that hypoxia activates the UPR in cardiac myocytes and that XBP1-inducible proteins may contribute to protecting the myocardium during hypoxic stress.

Original languageEnglish (US)
Pages (from-to)275-282
Number of pages8
JournalCirculation research
Volume99
Issue number3
DOIs
StatePublished - Aug 2006
Externally publishedYes

Keywords

  • Cardiac myocytes
  • Cardiac transcription factors
  • Chaperones
  • ER stress
  • Hypoxia
  • Ischemia
  • Mouse
  • Myocardial infarction
  • Unfolded protein response

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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