This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kronfeld-Kinar, Y. Articles by Salzberg, S. Search for Related Content PubMed PubMed Citation Articles by Kronfeld-Kinar, Y. Articles by Salzberg, S.

Involvement of PKR in the Regulation of Myogenesis¹

Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900 [Y. K-K., S. V., T. H., S. S.], and Laboratory of Microbiology, Rambam Medical Center, Haifa [F. L.], Israel

The involvement of the double-stranded RNA-activated protein kinase PKR in the regulation of the myogenic process was investigated. For this purpose, the murine myogenic cell line C2C12 was used. The cells were first cultivated in either growth medium or differentiation medium (DM), and the activation of PKR during differentiation was determined by monitoring its enzymatic activity and by immunoblot analysis. A significant increase in both parameters was detected already at 24 h in DM, whereas in cells grown in growth medium, the increase was evident only after 96 h, when spontaneous differentiation was observed in highly crowded cultures. Consequently, we established the direct effect of PKR activation on the myogenic process. C2C12 cells were transfected with an expression vector harboring a cDNA molecule encoding human PKR fused to the inducible metallothionein promoter. One of the clones (clone 8) expressing high levels of PKR was selected and further analyzed. In the presence of ZnCl₂, which activates the promoter, the rate of cell growth of the transfected cells was clearly reduced compared to that of wild-type C2C12 cells transfected with only the neomycin-resistant gene (C2-NEO). In addition, altered morphology with partial fusion was observed. Biochemically, an increase in creatine kinase activity accompanied by an increased rate of expression of the myogenic protein troponin T and the myogenic transcription factors myoD and myogenin was detected in clone 8 cells exposed to ZnCl₂. Most importantly, an induction in the level of cyclin-dependent kinase inhibitor p21^WAF1 and an increase in the level of the underphosphorylated active form of the tumor suppressor protein pRb concomitant with the down-regulation of cyclin D1 and c-myc were also evident in the transfected clones. These changes were similar to those observed in normal C2C12 cells cultivated in DM. We conclude that PKR is an important regulatory protein participating in the myogenic process.

This article has been cited by other articles:

				J. F. Raven, D. Baltzis, S. Wang, Z. Mounir, A. I. Papadakis, H. Q. Gao, and A. E. Koromilas PKR and PKR-like Endoplasmic Reticulum Kinase Induce the Proteasome-dependent Degradation of Cyclin D1 via a Mechanism Requiring Eukaryotic Initiation Factor 2{alpha} Phosphorylation J. Biol. Chem., February 8, 2008; 283(6): 3097 - 3108. [Abstract] [Full Text] [PDF]

				U. von Holzen, A. Pataer, U. Raju, D. Bocangel, S. A. Vorburger, Y. Liu, X. Lu, J. A. Roth, B. B. Aggarwal, G. N. Barber, et al. The Double-Stranded RNA-Activated Protein Kinase Mediates Radiation Resistance in Mouse Embryo Fibroblasts through Nuclear Factor {kappa}B and Akt Activation Clin. Cancer Res., October 15, 2007; 13(20): 6032 - 6039. [Abstract] [Full Text] [PDF]

				M. A. Garcia, J. Gil, I. Ventoso, S. Guerra, E. Domingo, C. Rivas, and M. Esteban Impact of Protein Kinase PKR in Cell Biology: from Antiviral to Antiproliferative Action Microbiol. Mol. Biol. Rev., December 1, 2006; 70(4): 1032 - 1060. [Abstract] [Full Text] [PDF]

				D. Sinha, Z. Wang, K. L. Ruchalski, J. S. Levine, S. Krishnan, W. Lieberthal, J. H. Schwartz, and S. C. Borkan Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors Am J Physiol Renal Physiol, April 1, 2005; 288(4): F703 - F713. [Abstract] [Full Text] [PDF]

				N. Kubica, S. R. Kimball, L. S. Jefferson, and P. A. Farrell Alterations in the expression of mRNAs and proteins that code for species relevant to eIF2B activity after an acute bout of resistance exercise J Appl Physiol, February 1, 2004; 96(2): 679 - 687. [Abstract] [Full Text] [PDF]

				S.-L. Tan, S. U. Tareen, M. W. Melville, C. M. Blakely, and M. G. Katze The Direct Binding of the Catalytic Subunit of Protein Phosphatase 1 to the PKR Protein Kinase Is Necessary but Not Sufficient for Inactivation and Disruption of Enzyme Dimer Formation J. Biol. Chem., September 20, 2002; 277(39): 36109 - 36117. [Abstract] [Full Text] [PDF]

				M. S. Chacko, X. Ma, and M. L. Adamo Double-Stranded Ribonucleic Acid Decreases C6 Rat Glioma Cell Proliferation in Part by Activating Protein Kinase R and Decreasing Insulin-Like Growth Factor I Levels Endocrinology, June 1, 2002; 143(6): 2144 - 2154. [Abstract] [Full Text] [PDF]

				J. D. Amack and M. S. Mahadevan The myotonic dystrophy expanded CUG repeat tract is necessary but not sufficient to disrupt C2C12 myoblast differentiation Hum. Mol. Genet., September 1, 2001; 10(18): 1879 - 1887. [Abstract] [Full Text] [PDF]

				C. Bisbal, M. Silhol, H. Laubenthal, T. Kaluza, G. Carnac, L. Milligan, F. Le Roy, and T. Salehzada The 2'-5' Oligoadenylate/RNase L/RNase L Inhibitor Pathway Regulates Both MyoD mRNA Stability and Muscle Cell Differentiation Mol. Cell. Biol., July 15, 2000; 20(14): 4959 - 4969. [Abstract] [Full Text]