Double-stranded RNA-dependent protein kinase is required for bone calcification in MC3T3-E1 cells in vitro

Kaya Yoshida, Hirohiko Okamura, Bruna Rabelo Amorim, Akiko Ozaki, Hiroaki Tanaka, Hiroyuki Morimoto, Tatsuji Haneji

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

In this study, we demonstrated that double-stranded RNA-dependent protein kinase (PKR) is required for the calcification of osteoblasts via the signal transducers and activators of transcription 1α (STAT1α) signaling in vitro. A dominant-negative mutant PKR cDNA, in which the amino acid lysine at 296 was replaced with arginine and which does not have catalytic activity, was transfected into mouse osteoblastic MC3T3-E1 cells; thereby, we established cells that stably expressed the PKR mutant gene (PKR-K/R). Phosphorylation of PKR was not stimulated by polyinosic-polycytidylic acid in the mutant cells. The PKR-K/R mutant cells exhibited up-regulated cell growth and had low alkaline phosphatase (ALP) activity. The PKR-K/R mutant cells were not able to form bone nodules in vitro. In the PKR-K/R mutant cells, runt-related gene 2 (Runx2)-mediated transcription decreased compared with the levels in the control cells. The expression of STAT1α protein increased and the protein was translocated to the nucleus in the PKR-K/R mutant cells. When the expression of STAT1α protein in PKR mutant cells was suppressed using RNAi, the activity of Runx2-mediated transcription recovered to the control level. Our results indicate that PKR is a stimulator of Runx2 transcription and is a negative modulator of STAT1α expression. Our findings also suggest that PKR plays important roles in the differentiation and calcification of osteoblasts by modulating STAT1α and/or Runx2 expression.

Original languageEnglish
Pages (from-to)117-125
Number of pages9
JournalExperimental Cell Research
Volume311
Issue number1
DOIs
Publication statusPublished - Nov 15 2005
Externally publishedYes

Keywords

  • Bone
  • Osteoblasts
  • PKR
  • Runx2
  • STAT1α

ASJC Scopus subject areas

  • Cell Biology

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