title: Multiple oligomerization domains of KANK1-PDGFRβ are required for JAK2-independent hematopoietic cell proliferation and signaling via STAT5 and ERK.
abstract: BACKGROUND
  KANK1-PDGFRB is a fusion gene generated by the t(5;9) translocation between KANK1 and the platelet-derived growth factor receptor beta gene PDGFRB. This hybrid was identified in a myeloproliferative neoplasm featuring severe thrombocythemia, in the absence of the JAK2 V617F mutation.
  
  
  METHODS
  KANK1-PDGFRB was transduced into Ba/F3 cells and CD34(+) human progenitor cells to gain insights into the mechanisms whereby this fusion gene transforms cells.
  
  
  RESULTS
  Although platelet-derived growth factor receptors are capable of activating JAK2, KANK1-PDGFRβ did not induce JAK2 phosphorylation in hematopoietic cells and a JAK inhibitor did not affect KANK1-PDGFRβ-induced cell growth. Like JAK2 V617F, KANK1-PDGFRβ constitutively activated STAT5 transcription factors, but this did not require JAK kinases. In addition KANK1-PDGFRβ induced the phosphorylation of phospholipase C-γ, ERK1 and ERK2, like wild-type PDGFRβ and TEL-PDGFRβ, another hybrid protein found in myeloid malignancies. We next tested various mutant forms of KANK1-PDGFRβ in Ba/F3 cells and human CD34(+) hematopoietic progenitors. The three coiled-coil domains located in the N-terminus of KANK1 were required for KANK1-PDGFRβ-induced cell growth and signaling via STAT5 and ERK. However, the coiled-coils were not essential for KANK1-PDGFRβ oligomerization, which could be mediated by another new oligomerization domain. KANK1-PDGFRβ formed homotrimeric complexes and heavier oligomers.
  
  
  CONCLUSIONS
  KANK1-PDGFRB is a unique example of a thrombocythemia-associated oncogene that does not signal via JAK2. The fusion protein is activated by multiple oligomerization domains, which are required for signaling and cell growth stimulation.
authors.affiliation: de Duve Institute, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Medves
authors.forename: Laura A
authors.initials: LA
authors.lastname: Noël
authors.forename: Carmen P
authors.initials: CP
authors.lastname: Montano-Almendras
authors.forename: Roxana I
authors.initials: RI
authors.lastname: Albu
authors.forename: Hélène
authors.initials: H
authors.lastname: Schoemans
authors.forename: Stefan N
authors.initials: SN
authors.lastname: Constantinescu
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Demoulin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D003598:Cytoskeletal Proteins; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism*; D009196:Myeloproliferative Disorders / Q000235:genetics / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; C467739:KANK1 protein, human; C569811:KANK1-PDGFRbeta fusion protein, human; D015514:Oncogene Proteins, Fusion; D050799:STAT5 Transcription Factor; D025521:Tumor Suppressor Proteins; D020797:Receptor, Platelet-Derived Growth Factor beta; D053614:Janus Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases