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 Recio, J. A. Articles by Notario, V. Search for Related Content PubMed PubMed Citation Articles by Recio, J. A. Articles by Notario, V.

Both Normal and Transforming PCPH Proteins Have Guanosine Diphosphatase Activity But Only the Oncoprotein Cooperates with Ras in Activating Extracellular Signal-regulated Kinase ERK1¹

Laboratory of Experimental Carcinogenesis, Department of Radiation Medicine, Georgetown University Medical Center, Washington, DC 20007

Previous reports from our laboratory described the activation of the PCPH gene into the PCPH oncogene (mt-PCPH, reported previously as Cph) by a single point mutational deletion. As a consequence, the mt-PCPH oncoprotein is a truncated form of the normal PCPH protein. Although both proteins have ribonucleotide diphosphate-binding activity, only mt-PCPH acted synergistically with a human H-Ras oncoprotein to transform murine NIH3T3 fibroblasts. We report here the expression of the PCPH and mt-PCPH proteins in Escherichia coli and the finding that the purified bacterial recombinant proteins have intrinsic guanosine diphosphatase (GDPase) activity. However, expression of the Syrian hamster PCPH and mt-PCPH proteins in haploid yeast strains engineered to be GDPase deficient by targeted disruption of the single GDA1 allele did not complement their glycosylation-disabled phenotype, suggesting the existence of significant functional differences between the mammalian and yeast enzymes. Results from transient cotransfections into NIH3T3, COS-7, or 293T cells indicated that, in mammalian cells, both PCPH and mt-PCPH cause an overall down-regulation of the stimulatory effect of epidermal growth factor or the activated ras or raf oncogenes on the Ras/mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) signaling pathway. However, despite this overall negative regulatory role on Ras signaling, mt-PCPH, but not PCPH, cooperated with the Ras oncoprotein to produce a prolonged stimulation of the phosphorylation of ERK1 but had no effect on the phosphorylation levels of ERK2. These results represent a clear difference between the mechanisms of action of PCPH and mt-PCPH and suggest that the ability to cause a sustained activation of ERK1 may be an important determinant of the transforming activity of mt-PCPH.

This article has been cited by other articles:

				J. Villar, M. I. Arenas, C. M. MacCarthy, M. J. Blanquez, O. M. Tirado, and V. Notario PCPH/ENTPD5 Expression Enhances the Invasiveness of Human Prostate Cancer Cells by a Protein Kinase C{delta} Dependent Mechanism Cancer Res., November 15, 2007; 67(22): 10859 - 10868. [Abstract] [Full Text] [PDF]

				J. M. Mullin, J. M. Leatherman, M. C. Valenzano, E. R. Huerta, J. Verrechio, D. M. Smith, K. Snetselaar, M. Liu, M. K. Francis, and C. Sell Ras Mutation Impairs Epithelial Barrier Function to a Wide Range of Nonelectrolytes Mol. Biol. Cell, December 1, 2005; 16(12): 5538 - 5550. [Abstract] [Full Text] [PDF]

				O. M. Tirado, S. Mateo-Lozano, S. Sanders, L. E. Dettin, and V. Notario The PCPH Oncoprotein Antagonizes the Proapoptotic Role of the Mammalian Target of Rapamycin in the Response of Normal Fibroblasts to Ionizing Radiation Cancer Res., October 1, 2003; 63(19): 6290 - 6298. [Abstract] [Full Text] [PDF]

				J. G. Ellis IV, M. Davila, and R. Chakrabarti Potential Involvement of Extracellular Signal-regulated Kinase 1 and 2 in Encystation of a Primitive Eukaryote, Giardia lamblia. STAGE-SPECIFIC ACTIVATION AND INTRACELLULAR LOCALIZATION J. Biol. Chem., January 10, 2003; 278(3): 1936 - 1945. [Abstract] [Full Text] [PDF]

				H. Yaguchi, N. Ohkura, T. Tsukada, and K. Yamaguchi Menin, the Multiple Endocrine Neoplasia Type 1 Gene Product, Exhibits GTP-hydrolyzing Activity in the Presence of the Tumor Metastasis Suppressor nm23 J. Biol. Chem., October 4, 2002; 277(41): 38197 - 38204. [Abstract] [Full Text] [PDF]

				J. A. Recio, J. G. Paez, S. Sanders, T. Kawakami, and V. Notario Partial Depletion of Intracellular ATP Mediates the Stress-Survival Function of the PCPH Oncoprotein Cancer Res., May 1, 2002; 62(9): 2690 - 2694. [Abstract] [Full Text] [PDF]