Functional expression of double-stranded RNA-dependent protein kinase in rat intestinal epithelial cells.
Intestinal epithelial cells (IECs) are exposed to external environment, microbial and viral products, and serve as essential barriers to antigens. Recent studies have shown that IECs express Toll-like receptors (TLRs) and respond to microbial components. The antimicrobial and antiviral barriers consist of many molecules including TLRs. To investigate the further component of this barrier in intestine, we examined the expression of double-stranded RNA-dependent protein kinase (PKR). PKR is a player in the cellular antiviral response and phosphorylates alpha-subunit of the eukaryotic translation initiation factor 2 (eIF-2alpha) to block protein synthesis and induces apoptosis. In this study, we showed that the expression of PKR was restricted to the cytoplasm of absorptive epithelial cells in the intestine of adult rat. We also demonstrated that PKR was expressed in the cultured rat intestinal epithelial cells (IEC-6). The level of PKR protein expression and the activity of alkaline phosphatase (ALP) increased in the cultured IEC-6 cells in a time-dependent manner. Inhibition of PKR by the 2-aminopurine treatment decreased ALP activity in the IEC-6 cells. Treatment of IEC-6 cells with synthetic double-stranded RNA (dsRNA) induced cell death in a dose-dependent manner. The addition of hydrocortisone also provoked suppression of PKR expression and ALP activity. This modulation might be mediated by signal transducers and activators of transcription-1 (STAT-1) protein. We concluded that PKR is expressed in IECs as potent barriers to antigens and is a possible modulator of the differentiation of rat IECs.
Sato
Nagahiro
N
Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, 1-1, Iseigaoka, Yahatanishi, Kitakyushu 807-8555, Japan.
Morimoto
Hiroyuki
H
Baba
Ryoko
R
Nakamata
Junichi
J
Doi
Yoshiaki
Y
Yamaguchi
Koji
K
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D020895:Enterocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006854:Hydrocortisone / Q000494:pharmacology; D007421:Intestine, Small / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D011070:Poly I-C / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D012330:RNA, Double-Stranded / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011914:Rats, Inbred BN; D050794:STAT1 Transcription Factor / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D019892:eIF-2 Kinase / Q000235:genetics* / Q000378:metabolism*
D047428:Protein Kinase Inhibitors; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494081:Stat1 protein, rat; D019892:eIF-2 Kinase; D000469:Alkaline Phosphatase; D011070:Poly I-C; D006854:Hydrocortisone