Erythropoietin Receptor Signal Transduction Requires Protein Geranylgeranylation
- Departments of Pharmacology (S.N.H., M.K.H., R.J.H.) and Internal Medicine (R.J.H.), Carver College of Medicine, University of Iowa, Iowa City, Iowa
- Address correspondence to:
Dr. Raymond J. Hohl, Department of Internal Medicine, C32 GH, University of Iowa, Iowa City, IA 52242. E-mail: raymondhohl{at}uiowa.edu
Abstract
Erythropoietin (Epo) acts through the erythropoietin receptor, a member of the type-1 cytokine receptor family, to influence survival, proliferation, and differentiation of erythroid progenitors. Epo stimulation of factor-dependent 32D cells results in phosphorylation of many proteins, including Janus kinase (Jak) 2, signal transducer and activator of transcription (Stat) 5, and extracellular signal-regulated kinase (Erk). Some of Epo-activated signaling proteins require isoprenylation, either farnesylation or geranylgeranylation, for post-translational modification. In this study, we sought to characterize the interplay between protein isoprenylation and Epo signal transduction. Using two different Epo-responsive cell lines, we found that depletion of mevalonate and its isoprenoid derivatives using the 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor lovastatin impairs Epo signaling as assessed by phosphorylation of cellular substrates and inhibition of apoptosis. Interestingly, the effect of mevalonate depletion was prevented by adding back geranylgeranyl pyrophosphate but not farnesyl pyrophosphate. Furthermore, selective inhibition of protein geranylgeranylation mimicked the effect of lovastatin, whereas selective inhibition of farnesylation had no effect. These results indicate that protein geranylgeranylation and not farnesylation is important for proper Epo signal transduction.
Footnotes
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This work was supported by the Roy J. Carver Charitable Trust as a Research Program of Excellence and the Roland W. Holden Family Program for Experimental Cancer Therapeutics.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.092510.
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ABBREVIATIONS: Epo, erythropoietin; EpoR, erythropoietin receptor; Stat, signal transducer and activator of transcription; Jak, Janus kinase; Erk, extracellular signal-regulated kinase; HMG, 3-hydroxy-3-methylglutaryl; FPP, farnesyl pyrophosphate; FITC, fluorescein isothiocyanate; GGPP, geranylgeranyl pyrophosphate; FTI-277, farnesyltransferase inhibitor-277; PAGE, polyacrylamide gel electrophoresis; IPP, isopentenyl pyrophosphate; GPP, geranyl pyrophosphate; FTase, farnesyltransferase; GGTase, geranylgeranyltransferase; GGTI-286, geranylgeranyltransferase inhibitor-286; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; IL, interleukin.
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↵1 Current affiliation: Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA.
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- Received July 12, 2005.
- Accepted September 30, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
