The Hopscotch Jak kinase requires the Raf pathway to promote blood cell activation and differentiation in Drosophila

Mol Genet Genomics. 2002 Mar;267(1):57-63. doi: 10.1007/s00438-001-0632-7. Epub 2002 Feb 1.


Cytokines regulate the development and differentiated functions of hematopoietic cells by activating multiple signaling pathways, including the Jak-Stat pathway, the PI3-kinase pathway, and the Ras/Raf pathway. While the Jak-Stat interaction has been extensively studied, the relationship between this pathway and other cytokine-induced signaling pathways is not fully understood. In Drosophila melanogaster, mutations that result in hyperactivity of the Jak kinase Hopscotch (Hop) cause an activation of the larval blood cell encapsulation response, including blood cell aggregation and differentiation of plasmatocytes into apparent lamellocytes. Here, we demonstrate that Hop requires the activity of the Raf pathway to promote the activation response of larval plasmatocytes, and provide evidence to suggest that the Hop and D-Raf proteins physically interact. We also show that basal level activity of the Raf pathway is required for the accumulation of circulating blood cells.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blood Cells / cytology
  • Cell Differentiation*
  • Drosophila Proteins*
  • Drosophila melanogaster / cytology*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / growth & development
  • Janus Kinases
  • Larva
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins c-raf / metabolism*
  • Transcription Factors


  • Drosophila Proteins
  • Transcription Factors
  • Protein-Tyrosine Kinases
  • Janus Kinases
  • hop protein, Drosophila
  • Proto-Oncogene Proteins c-raf
  • Raf protein, Drosophila