Document 0118
 DOCN  M95B0118
 TI    Calcium depletion from the endoplasmic reticulum activates the
       double-stranded RNA-dependent protein kinase (PKR) to inhibit protein
       synthesis.
 DT    9511
 AU    Srivastava SP; Davies MV; Kaufman RJ; Department of Biological
       Chemistry, University of Michigan; Medical Center, Ann Arbor 48105, USA.
 SO    J Biol Chem. 1995 Jul 14;270(28):16619-24. Unique Identifier : AIDSLINE
       MED/95348080
 AB    Calcium depletion from the endoplasmic reticulum inhibits protein
       synthesis and correlates with increased phosphorylation of the alpha
       subunit of eukaryotic initiation factor 2 (eIF-2 alpha) by a mechanism
       that does not require ongoing protein synthesis. To elucidate whether
       protein synthesis inhibition requires eIF-2 alpha phosphorylation and
       whether eIF-2 alpha phosphorylation is mediated by the double-stranded
       RNA-dependent protein kinase (PKR), we studied protein synthesis in
       response to calcium depletion mediated by calcium ionophore A23187 in
       cell lines overexpressing wild-type eIF-2 alpha, a mutant eIF-2 alpha
       (S51A) that is resistant to phosphorylation, or a dominant negative
       mutant PKR (K296P in catalytic subdomain II). Expression of either
       mutant eIF-2 alpha or mutant PKR partially protected NIH3T3 cells from
       inhibition of protein synthesis upon A23187 treatment. In contrast,
       overexpression of wild-type PKR increased sensitivity to protein
       synthesis inhibition mediated by A23187 treatment. In a COS-1 monkey
       cell transient transfection system, increased eIF-2 alpha
       phosphorylation in response to A23187 treatment was inhibited by
       expression of the dominant negative PKR mutant. Overexpression of the
       PKR regulatory RNA binding domain, independent of the PKR catalytic
       domain, was sufficient to inhibit increased phosphorylation of eIF-2
       alpha upon A23187 treatment. In addition, overexpression of the HIV TAR
       RNA binding protein also inhibited eIF-2 alpha phosphorylation upon
       A23187 treatment. Taken together, our data show that calcium depletion
       activates PKR to phosphorylate eIF-2 alpha, and this activation is
       likely mediated through the PKR RNA binding domain.
 DE    Animal  Base Sequence  Calcium/*PHYSIOLOGY  Cell Line  Endoplasmic
       Reticulum/*METABOLISM  Enzyme Activation  Mice  Molecular Sequence Data
       Phosphorylation  Protein-Serine-Threonine Kinases/*METABOLISM
       Proteins/*BIOSYNTHESIS  RNA, Double-Stranded/METABOLISM  Support, U.S.
       Gov't, P.H.S.  3T3 Cells  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).