HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 283, Issue 19, 12941-12948, May 9, 2008

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 283/19/12941    most recent M709302200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Dusa, A. Articles by Constantinescu, S. N. PubMed PubMed Citation Articles by Dusa, A. Articles by Constantinescu, S. N. Social Bookmarking                      What's this?

Substitution of Pseudokinase Domain Residue Val-617 by Large Non-polar Amino Acids Causes Activation of JAK2^*

Alexandra Dusa¹², Judith Staerk¹³, Joanne Elliott^¶, Christian Pecquet⁴, Hélène A. Poirel^||, James A. Johnston^¶, and Stefan N. Constantinescu⁵

From the Ludwig Institute for Cancer Research, B-1200 Brussels, Belgium, the de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium, the ^¶Infection and Immunity Group, Centre for Cancer Research and Cell Biology, Queens University, Belfast BT7 1NN, United Kingdom, and the ^||Centre for Human Genetics, Cliniques Universitaires St Luc, Université Catholique de Louvain, B-1200 Brussels, Belgium

Explaining the uniqueness of the acquired somatic JAK2 V617F mutation, which is present in more than 95% of polycythemia vera patients, has been a challenge. The V617F mutation in the pseudokinase domain of JAK2 renders the unmutated kinase domain constitutively active. We have performed random mutagenesis at position 617 of JAK2 and tested each of the 20 possible amino acids for ability to induce constitutive signaling in Ba/F3 cells expressing the erythropoietin receptor. Four JAK2 mutants, V617W, V617M, V617I, and V617L, were able to induce cytokine independence and constitutive downstream signaling. Only V617W induced a level of constitutive activation comparable with V617F. Also, only V617W stabilized tyrosine-phosphorylated suppressor of cytokine signaling 3 (SOCS3), a mechanism by which JAK2 V617F overcomes inhibition by SOCS3. The V617W mutant induced a myeloproliferative disease in mice, mainly characterized by erythrocytosis and megakaryocytic proliferation. Although JAK2 V617W would predictably be pathogenic in humans, the substitution of the Val codon, GTC, by TTG, the codon for Trp, would require three base pair changes, and thus it is unlikely to occur. We discuss how the predicted conformations of the activated JAK2 mutants can lead to better screening assays for novel small molecule inhibitors.

Received for publication, November 13, 2007 , and in revised form, March 6, 2008.

^* This work was supported by a grant from the Mandat d'Impulsion of the Belgian National Fund for Scientific Research (F. N. R. S.), the Fondation contre le cancer, Belgium, the Atlantic Philanthropies/Ludwig Institute for Cancer Research Clinical Discovery Program, the Salus Sanguinis Foundation, Belgium, the Action de Recherche Concertée (ARC) MEXP31 of the Université catholique de Louvain, and the PAI Program BCHM61B5, Belgium (to S. N. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains two supplemental figures.

¹ Co-first authors.

² A. D. currently holds an F. N. R. S. Télévie Ph. D. fellowship and was also funded by the Belgian American Educational Foundation.

³ J. S. was funded by a Ph. D. fellowship from the Daimler Benz foundation (Ladenburg, Germany), a F. N. R. S. Télévie, and a Salus Sanguinis fellowship.

⁴ The recipient of a de Duve Institute postdoctoral fellowship.

⁵ A Research Associate of the F. N. R. S., Belgium. To whom correspondence should be addressed: Ave. Hippocrate 74, UCL 75-4, Brussels, B-1200, Belgium. Fax: 322-764-65-66; E-mail: stefan.constantinescu{at}bru.licr.org.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?