title: Expression level and differential JAK2-V617F-binding of the adaptor protein Lnk regulates JAK2-mediated signals in myeloproliferative neoplasms.
abstract: Activating mutations in signaling molecules, such as JAK2-V617F, have been associated with myeloproliferative neoplasms (MPNs). Mice lacking the inhibitory adaptor protein Lnk display deregulation of thrombopoietin/thrombopoietin receptor signaling pathways and exhibit similar myeloproliferative characteristics to those found in MPN patients, suggesting a role for Lnk in the molecular pathogenesis of these diseases. Here, we showed that LNK levels are up-regulated and correlate with an increase in the JAK2-V617F mutant allele burden in MPN patients. Using megakaryocytic cells, we demonstrated that Lnk expression is regulated by the TPO-signaling pathway, thus indicating an important negative control loop in these cells. Analysis of platelets derived from MPN patients and megakaryocytic cell lines showed that Lnk can interact with JAK2-WT and V617F through its SH2 domain, but also through an unrevealed JAK2-binding site within its N-terminal region. In addition, the presence of the V617F mutation causes a tighter association with Lnk. Finally, we found that the expression level of the Lnk protein can modulate JAK2-V617F-dependent cell proliferation and that its different domains contribute to the inhibition of multilineage and megakaryocytic progenitor cell growth in vitro. Together, our results indicate that changes in Lnk expression and JAK2-V617F-binding regulate JAK2-mediated signals in MPNs.
authors.affiliation: Hôpital Avicenne, Assistance Publique-Hôpitaux de Paris (AP-HP), Service d'Hématologie Biologique, Bobigny, France.
authors.forename: Fanny
authors.initials: F
authors.lastname: Baran-Marszak
authors.forename: Hajer
authors.initials: H
authors.lastname: Magdoud
authors.forename: Christophe
authors.initials: C
authors.lastname: Desterke
authors.forename: Anabell
authors.initials: A
authors.lastname: Alvarado
authors.forename: Claudine
authors.initials: C
authors.lastname: Roger
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Harel
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Mazoyer
authors.forename: Bruno
authors.initials: B
authors.lastname: Cassinat
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chevret
authors.forename: Carole
authors.initials: C
authors.lastname: Tonetti
authors.forename: Stéphane
authors.initials: S
authors.lastname: Giraudier
authors.forename: Pierre
authors.initials: P
authors.lastname: Fenaux
authors.forename: Florence
authors.initials: F
authors.lastname: Cymbalista
authors.forename: Nadine
authors.initials: N
authors.lastname: Varin-Blank
authors.forename: Marie-Caroline
authors.initials: MC
authors.lastname: Le Bousse-Kerdilès
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Kiladjian
authors.forename: Laura
authors.initials: L
authors.lastname: Velazquez
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2 / Q000235:genetics* / Q000378:metabolism*; D008533:Megakaryocytes / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics*; D009196:Myeloproliferative Disorders / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013926:Thrombopoietin / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012333:RNA, Messenger; C490778:SH2B3 protein, human; D013926:Thrombopoietin; C507924:JAK2 protein, human; D053614:Janus Kinase 2